chemistry application questions 2010

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Additional Science Chemistry

Module Review C2 - Structures and Bonding

C2 - Ammonia

Name: ……………………………………………………………………. Science Group: ……………………………………………………….. Form: ……………………………………………………………………..

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Science – Revision Chemistry C2

Before you start – make sure you have things organised. Your Revision – some basics for success ! Understand what the examiners will be looking for from your performance.

GCSE Grade Skill required How do you test this ? Balance

A* Evaluate (judge the use / accuracy) (compare two methods ……)

A Synthesise (put ideas together) (what would happen if …..?)

Synthesis ; ‐ Mind map the topics ‐ Link the different topics ‐ Use ‘synthesis’ style exam

questions

20%

B Apply (solve unfamiliar problems) (predict what will happen next….)

C Analyse (make sense of information) (explain the pattern in this data…)

Application and Problem Solving ; ‐ Using problem solving style exam

questions (In this booklet)

‐ Questions from the text book ‐ Test each other

40%

D Explain (use facts to answer questions) (rephrase this information….)

E Remember (learn facts) (list the factors that affect….)

Knowledge and Understanding ; ‐ Use textbooks ‐ Use the learning outcome sheet ‐ Use Exam questions

(In this booklet)

40%

5 Steps to Revision Heaven ! Step 1 – Make sure you know what you have to learn / know / understand (Use the Outcomes) Step 2 – Plan your time carefully to make sure you cover everything (and still have a life !) Step 3 – Divide your Revision time into short time slots (perhaps 60 mins) Step 4 – Have a quiet, organised place in which to revise Step 5 – Organise your Revision time ;

‐ 20 mins to review the facts on your selected section ‐ 20 mins to test yourself against real exam questions (look at the table above) ‐ 20 mins to review what you found difficult and work on that particular section / skill

Do NOT stop at learning facts – practice the higher skills and you will get better at them !

Practice the Application questions, and not simply the Knowledge

and Understanding questions.

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Structures and Bonding C2A Your Learning Outcomes Topic

1.I can recall that atoms contain protons, neutrons and electrons 2.I can recall the relative charge and mass of protons, neutrons and electrons 3.I can work out how many protons, neutrons and electrons there are in atoms using mass and atomic numbers

4.I can explain what isotopes are 5.I can work out the electronic structure of an atom from the Atomic Number 6.I can recall that atoms are arranged in order of atomic number in the Periodic Table 7.I can explain the difference between elements and compounds 8.I know what an ion is – and how metals and non metal atoms form ions with opposite charges 9.I can describe how ions can be formed when metals react with non-metals 10.I can describe how Group 1 elements react with non-metals 11.I can describe how Group 7 elements react with metals 12.I can describe the structure and explain the properties of ionic compounds 13.I can write the formula of an ionic compound 14.I can explain what a covalent bond is 15.I can describe the structure and explain the properties of simple molecular substances 16.I can draw the structure of molecules using stick diagrams and dot-cross diagrams 17.I can describe the structure and explain the properties of giant covalent compounds 18.I can describe the structure and explain the properties of diamond and graphite 19.I can describe and explain some properties of metals 20. H I can describe the structure of metallic substances

21. H I can represent the bonding in metals in a diagram 22.I can name the three types of bonding: ionic, covalent and metallic 23.I can name the five types of structure: ionic, simple molecular, giant covalent, metallic and monatomic

24.I can identify which type of structure a substance has from its physical properties 25.I can explain what smart materials are and can give some of their uses 26.I can explain what nanomaterials are and can give some of their uses 27.I can evaluate developments and applications of smart materials and nanoscience 28. H I can recall what relative atomic and formula masses are 29.I can calculate relative formula mass given the formula of a molecule or compound 30.I can calculate the percentage by mass of an element in a compound 31.I can recall what a mole is 32. H I can use the formula mass = Mr x moles

33. H I can calculate the mass of substances involved in chemical reactions

34. H I can explain what an empirical formula is

35. H I can explain what a molecular formula is

36. H I can work out empirical and molecular formulas

37. H I can calculate the yield for a reaction

38. H I can balance equations

39. H I can calculate the atom economy for a reaction 40.I can explain why reactions do not give a 100 % yield 41.I can explain what atom economy is and why reactions with a high atom economy are important for sustainable development and economic reasons

42.I can explain the energy changes that can take place in reactions 43.I can describe what happens in electrolysis 44. H I can write half equations to represent what happens in electrolysis 45.I can define what oxidation and reduction are in terms of the transfer of electrons

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Structures and Bonding C2A Your Learning Outcomes

Topic - cont’d 46.I understand what happens in the electrolysis of solutions 47.I can predict the products of electrolysis of solutions 48.I can describe what happens in the electrolysis of sodium chloride solution 49.I can recall what the products and uses of the electrolysis of sodium chloride solution 50.I can explain how copper can be purified by electrolysis Why is ammonia important C2B Your Learning Outcomes

Topic 1.I can explain how energy transfers are linked with chemical reactions 2.I can describe the differences between exothermic reactions and endothermic reactions 3.I can describe what happens in a reversible reaction 4.I can describe how to test for the presence of water using white anhydrous copper sulphate 5. H I can explain what an equilibrium reaction is

6. H I can explain that the relative amounts of the reacting substances depend on the reaction conditions

7.I can describe how the Haber Process is used to make ammonia 8.I can explain the processes that occur during the Haber process – and how to control them 9.I can explain how to measure the rate of a reaction 10.I can interpret graphs showing how amounts of substance involved in a reaction change 11.I can explain the collision theory and activation energy 12.I can describe how increasing the temperature increases the rate of a reaction 13.I can explain that the rate of a reaction increases if the solid reactants have a greater surface area

14.I can explain how rate of reaction is affected using the collision theory 15.I can explain how increasing the concentration of reactants increases the rate of a reaction 16.I can explain how increasing the pressure of gases increases the rate of a reaction 17.I can describe what a catalyst is and how it increases the rate of a reaction 18.I can evaluate the advantages and disadvantages of using a catalyst in an industrial process 19. H I can explain how changing the temperature can alter the position of an equilibrium

20. H I can explain how changing the pressure affects the position of an equilibrium

21. H I can explain that equal volumes of gases have the same numbers of molecules

22. H I can explain how the concentration of a solution is measured 23.I can describe how insoluble salts are made by precipitation reactions 24.I can give examples of useful precipitation reactions 25.I can describe how to make a soluble salt from an acid and either a metal or an insoluble base 26.I can explain that the salt formed depends on the acid and base used 27.I can explain the difference between bases and alkalis 28.I can describe how acids contain hydrogen ions and alkalis contain hydroxide ions and can use the pH scale

29.I can describe how to carry out a titration 30.I can describe how neutralisation can be followed using an indicator 31.I can describe how ammonia dissolves in water to form an alkaline solution 32.I can give an example of the use of ammonium salts

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Layout of this booklet. This table shows where you can find questions for you to check your understanding and skill level for each section. Structure and Bonding ;

Section Learning outcome numbers Questions for this section

1.Atom structure and the Periodic Table 1 to 11 Pages 5 to 17 (Answers – pages 17 to 20)

2.Bonding and properties 12 to 27 Pages 21 to 30 (Answers – pages 31 to 34)

3.Quantitative chemistry and calculations 28 to 42 Pages 35 to 37 (Answers – page 38)

4. Electrolysis 43 to 50 Pages 39 to 42 (Answers – pages 43 & 44)

Why is Ammonia important ?

Section Learning outcome numbers Questions for this section

1.Different types of chemical reactions 1 to 4 27 to 30

Pages 45 to 50 (Answers – pages 51 & 52)

2.Reversible reactions / the Haber Process 5 to 8 Pages 53 to 58 (Answers – pages 59 to 61)

3.Rates of reaction – measure and explain 9 to 22 Pages 62 to 66 (Answers – pages 67 to 68)

4.Soluble and insoluble salts 23 to 26 31 to 32

Pages 69 to 72 (Answers – pages 73 to 74)

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Structure and Bonding Atom Structure and the Periodic Table – self test questions.

1. This is a Knowledge and Understanding question.

The diagram represents an atom. Choose words from the list to label the diagram.

electron ion neutron nucleus

proton

(Total 3 marks)


There are millions of different substances that make up our world. All these substances are made from chemical elements.

(a) What is an element?

.....................................................................................................................................

..................................................................................................................................... (1)

(b) Many substances are compounds. What is a compound?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 3 marks)

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The two carbon atoms represented below are isotopes.

14 mass number 12C C

6 proton number 6

ISOTOPE 1. ISOTOPE 2.

(a) Describe two ways in which the isotopes are similar.

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Describe as fully as you can one way in which they are different.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 4 marks)


The diagram shows the structure of a lithium atom.

++

+

+

KEY

= proton= electron

(a) (i) What is represented by .................................................................................

(ii) What is represented by +

++ ...........................................................................

(2)

(b) What is the symbol for lithium? ................................................................................ (1)

(Total 3 marks)

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The diagram represents the electronic structure of an atom of an element.

×

×

×

× ×

×

Nucleus

The periodic table on the Data Sheet may help you with this question.

(a) Name this element.

..................................................................................................................................... (1)

(b) Complete this sentence.

The nucleus of an atom contains neutrons and .......................................................... (1)

(Total 2 marks)

6. This is an Application question.

Electrons, neutrons and protons are sub-atomic particles.

(a) Complete the six spaces in the following table.

Name of sub-atomic particle

Relative mass Relative charge

....................................... 1 ........................................

....................................... ........................................ 0

....................................... 18401

.........................................

(3)

(b) An aluminium atom has 13 electrons. How are these arranged in shells around the

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nucleus?

.................................................................................................................................... (1)

(c) Chromium atoms have 24 protons and 28 neutrons.

(i) How many electrons does each neutral chromium atom have?

........................................................................................................................... (1)

(ii) What is the mass number of chromium?

........................................................................................................................... (1)

(d) What change occurs to an atom which undergoes the process of reduction in a chemical reaction?

....................................................................................................................................

.................................................................................................................................... (1)

(e) The diagram shows part of the ionic lattice of a sodium chloride crystal.

Sodium ionChloride ion

Explain why the ions in this lattice stay in place.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (3)

(Total 10 marks)

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The diagram shows a light bulb.

Argon gas

Metalfilament

(a) (i) An argon atom has the structure shown. Use the words in the box to label the particles in the atom. Each word should only be used once.

electron neutron proton

882

1822

(2)

(ii) Argon is unreactive. Why?

.....................................................................................................................

..................................................................................................................... (1)

(b) Oxygen would not be a suitable gas to use in a light bulb. Explain why.

................................................................................................................................

................................................................................................................................ (2)

(Total 5 marks)


11

Use a Periodic Table to help you to answer this question.

(a) Describe, in as much detail as you can, the structure of a fluorine atom.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(b) Complete the diagram to show the electronic structure of a magnesium atom.

Mg

(1)

(Total 4 marks)

12


The diagram shows an atom.

...................................D

....................................C

....................................B

....................................A

(a) On the diagram, write the names of structures A, B, C and D. (4)

(b) To which Group of the periodic table does this atom belong?

.....................................................................................................................................

Give one reason for your answer.

.....................................................................................................................................

..................................................................................................................................... (2)

(c) Name the element which is made up of this type of atom.

..................................................................................................................................... (1)

(Total 7 marks)

13


The diagrams show three isotopes of potassium.

1920

1921

1922

Key

Proton Neutron Electron

(i) In what way does the atomic structure show you that they are all atoms?

.....................................................................................................................................

..................................................................................................................................... (1)

(ii) Explain why these three atoms are called isotopes of potassium.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 4 marks)

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11. This is an Application / Synthesis question.

About 100 years ago a scientist called J. J. Thomson thought that an atom was a ball of positive charge with negative particles stuck inside. Today a different model is used. The diagram shows how an atom of carbon is represented by this model.

+ +

++

++

(a) The negative particles are called electrons.

(i) What is the name of the positive particles ⊕?

........................................................................................................................... (1)

(ii) What particle is represented by •?

........................................................................................................................... (1)

(iii) What is the central part of the atom called that contains both ⊕ and •?

........................................................................................................................... (1)

(b) Use the model to explain why the six electrons are arranged as shown.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 5 marks)

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(a) The diagram shows the atomic structure of an atom of lithium.

(i) Label the diagram to show an electron, a neutron and a proton. (2)

(ii) What is the atomic number of lithium?

.......................................................................................................................... (1)

(b) The diagrams show the electron arrangement of the atoms of two elements.

– –– –– –– – ––

– –

– –– –

– –– –– –– –

–

–

X

(i) Name the part of the atoms labelled X.

.......................................................................................................................... (1)

(ii) Why are these two elements in the same group of the Periodic Table?

..........................................................................................................................

.......................................................................................................................... (1)

(Total 5 marks)

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13. This is an Application / Synthesis question.

John Dalton wrote these statements in 1808.

• “All substances are made of a vast number of extremely small particles called atoms.”

• “Every particle of water is like every other particle of water, every particle of hydrogen is like every other particle of hydrogen, etc.”

(a) “Every particle of water is like every other particle of water.” Use Dalton’s ideas and your knowledge of water to explain why.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Dalton thought that all atoms of an element are exactly the same. We now know that it is possible to have atoms of the same element but with different mass numbers. The diagrams represent two atoms of hydrogen.

+ +

Atom A Atom B

(i) State, in terms of particles, how these two atoms are different.

..........................................................................................................................

.......................................................................................................................... (1)

(ii) Complete this sentence by choosing the correct word from the box.

ions isotopes molecules protons

Atoms of the same element which have different mass numbers are called

......................................................................... . (1)

(Total 4 marks)

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14. This is an Application question. Caesium is an element in Group 1 of the periodic table.

(a) Which of the electronic structures represented by A to D is correct for a caesium atom? The periodic table on the Data Sheet may help you to answer this question.

Electronic structure

A 2, 8, 18, 18, 8, 1

B 2, 8, 18, 18, 9

C 2, 8, 18, 27

D 2, 8, 18, 18, 6, 3

The electronic structure for a caesium atom is represented by letter ......................... (1)

(b) When a small piece of lithium is added to cold water it fizzes around on the surface of the water. A small piece of caesium explodes when added to water.

Explain in terms of electronic structure why a caesium atom is more reactive than a lithium atom.

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 3 marks)

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Structure and Bonding Atom Structure and the Periodic Table – answers. 1. electron

nucleus neutron

each for 1 mark [3]

2. (a) a substance which contains one type of atom 1

or a substance that cannot be broken down into anything simpler

for 1 mark (b) more than one element/more than one type of atom 2

combined/join together/bonded for 1 mark each

[3] 3. (a) same number/six electrons; 2

same number/six protons; react in same way not same element or both carbon

any two for 1 mark each (b) different number of neutrons 2

gains 1 mark but or

146 C has two more neutrons different mass number

gains 1 mark or but two mass units bigger

gains 2 marks

14

6 C has 8 neutrons while

126 C has 6 neutrons

gains 2 marks [4]

4. (a) (i) neutron (name only) 2

(ii) nucleus / protons and neutrons each for 1 mark (do not allow mass number)

(b) Li (correct cases of letters required) 1 for 1 mark

[3] 5. (a) carbon 1

accept C (b) protons 1

[2]

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6. (a) proton + (1) 3 both required

neutron 1 both required

electron − (1) both required

(b) 2.8.3 1 accept words or diagram to this effect

(c) (i) 24 1

(ii) 52 1 (d) any one of 1

• gains one or more electrons accept gains an electron

• becomes an anion do not credit becomes an ion

• becomes a negative ion (e) sodium ions have a (single) positive 1

charge and chloride ions have a (single) negative charge

do not credit ‘chlorine ions’ but allow this error to be carried forward

ions with opposite charge are 1

attracted (to each other) or the positive ions and the negative ions are attracted (to each other) or the sodium ions and the chloride ions are attracted (to each other)

(positive and negative) ions are 1

arranged alternatively (in each direction or dimension)

or ions with the same charge are repelled (by each other) no mark for just ionic bonds

[10] 7. (a) (i) all correct two marks 2

one or two correct one mark electron

proton neutron

(ii) (argon has) a full outer shell (of electrons) 1

accept energy level for shell accept does not lose or gain electrons do not accept does not form bonds or react or is a noble or inert gas

(b) oxygen would react (with metal) 1

accept oxygen is reactive do not accept metal would react (neutral)

metal would burn 1

accept metal would be ‘destroyed’ or metal oxide formed or metal is oxidised do not accept it would explode or would not last long accept filament for metal

[5]

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8. (a) 9 protons /Proton Number 9 1 mass / atomic number is neutral

10 neutrons 1 electron arrangement 2,7 / 9 electrons 1

incorrect configurations neutral if no points scored, allow 1 mark for nucleus surrounded by electrons or nucleus contains neutrons and protons

(b) 1

Mark is for 2,8,2 arrangements. accept electrons anywhere in correct orbit

[4] 9. (a) A – electron 1

B – nucleus 1 C – proton 1 D – neutron 1

(b) Group 1 / alkali metals 1

has one electron in outer shell 1 accept 3 protons / 3 electrons / atomic number 3 therefore lithium (so Group 1 / alkali metals)

(c) lithium 1

accept Li [7]

10. (i) same number of protons and electrons 1

accept equal numbers of protons and electrons do not accept they are neutral

(ii) same element 1

accept all atoms are potassium same number of protons 1

accept same atomic number accept they all have 19+

different number of neutrons 1 accept different mass numbers do not accept different atomic masses

[4] 11. (a) (i) proton 1

(ii) neutron 1 (iii) nucleus 1

(b) there are shells or energy levels or orbitals 1

do not accept ring the maximum number of electrons 1

found in the first shell or energy level is 2 accept first shell is full with 2 electrons

[5]

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12. (a) (i) electron or e 2

proton or p neutron or n

all correct 2 marks one correct 1 mark (ii) three / 3 1

accept 3 Li not Li3 (b) (i) nucleus 1

(ii) they both have seven electrons in the outer shell 1 accept they both have the same number of electrons in the outer shell or both need one electron to make fill outer shell

[5] 13. (a) water (molecules) contain two hydrogen

atoms and one oxygen atom 2 all water molecules have the formula H2O for 2 marks water molecules contain hydrogen and oxygen (atoms) for 1 mark water is H2O for 1 mark

(b) (i) atom A has no neutrons / atom B has one neutron 1

allow different numbers of neutrons (ii) isotopes 1

[4] 14. (a) A 1

accept a or 2, 8, 18, 18, 8, 1 (b) outer shell further from nucleus or 1

outer shell electron less strongly attracted to nucleus or outer shell more shielded

do not accept more shells or larger / bigger atoms alone so outer shell electron lost more easily (owtte) 1

accept correct converse linked to lithium ‘it’ must be linked to caesium outer must be used once at least for both marks

[3]

22

Bonding – self test questions

1. This is a Knowledge and Understanding & Application question.

Electrons, neutrons and protons are sub-atomic particles.

(a) Complete the six spaces in the following table.

Name of sub-atomic particle

Relative mass Relative charge

....................................... 1 ........................................

....................................... ........................................ 0

....................................... 18401

.........................................

(3)

(b) An aluminium atom has 13 electrons. How are these arranged in shells around the nucleus?

.................................................................................................................................... (1)

(c) Chromium atoms have 24 protons and 28 neutrons.

(i) How many electrons does each neutral chromium atom have?

........................................................................................................................... (1)

(ii) What is the mass number of chromium?

........................................................................................................................... (1)

(d) What change occurs to an atom which undergoes the process of reduction in a chemical reaction?

....................................................................................................................................

.................................................................................................................................... (1)

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(e) The diagram shows part of the ionic lattice of a sodium chloride crystal.

Sodium ionChloride ion

Explain why the ions in this lattice stay in place.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (3)

(Total 10 marks)


This question is about the structure of atoms.

(a) Choose words from the list to complete the sentences below.

electrons ions neutrons protons

In an atom, the particles with a negative charge are called .....................................

Particles in the nucleus with no charge are called .....................................................

An atom has no overall charge because is has the same number of electrons and

.................................................................................................................................... (3)

(b) Two isotopes of the element carbon are:

12

6

14

6C Cand

Complete the table of information for these two isotopes.

ATOMICNUMBER

MASSNUMBER

NUMBER OFPROTONS

NUMBER OFNEUTRONS

Isotope12

6C

Isotope14

6C

12 66 6

6 6

(2)

(Total 5 marks)

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3. This is a Knowledge and Understanding and Application question.

(a) The diagrams represent the atomic structures of two gases, hydrogen and helium.

x = an electronp = a protonn = a neutron

2p2n

hydrogen helium

Hydrogen gas is made up of diatomic molecules (molecules with two atoms). Helium gas exists as single atoms.

(i) How is a molecule of hydrogen formed from two hydrogen atoms? (You may use a diagram as part of your answer)

...........................................................................................................................

........................................................................................................................... (2)

(ii) Why does helium exist only as single atoms?

...........................................................................................................................

........................................................................................................................... (2)

(b) Hydrogen combines with carbon to form methane. Each molecule contains four hydrogen atoms strongly bonded to a carbon atom.

H

H

H

CH

H

H

H

H

CH

H

H

H

H

CH

H

H

H

H

CH

H

C

H

H

H H

structural formulaof methane CH4methane molecules

Explain why methane has a low boiling point.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 6 marks)

25


Choose words from this list to complete the sentences below.

carbonate chloride compound mixture oxide solution

(a) When two elements react, the new substance formed is called a .............................. . (1)

(b) The white powder formed when zinc reacts with oxygen is called zinc .......................... . (1)

(Total 2 marks)

5. This is a Knowledge and Understanding and Application question.

Atoms of calcium, phosphorus and fluorine are represented below, each with its mass number and proton number.

40Ca

20

31P

15

19F

9

mass numbers

proton numbers

(a) Use this information to complete the table.

Number of protons in the nucleus

Number of neutrons in the nucleus

Number of electrons

CALCIUM

20

20

PHOSPHORUS

16

15

FLUORINE

9

9

(3)

(b) Calcium and fluorine atoms can combine to form the compound calcium fluoride, CaF2.

The fluoride ion is represented by F–.

(i) Explain how the fluorine atom forms a fluoride ion.

..........................................................................................................................

.......................................................................................................................... (2)

(ii) How is the calcium ion represented?

.......................................................................................................................... (2)

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(c) Phosphorus and fluorine form a covalent compound, phosphorus trifluoride.

Complete the sentences below which are about this compound.

Phosphorus trifluoride is made up of phosphorus and fluorine ................................

These are joined together by sharing pairs of ............................................... to form

phosphorus trifluoride ........................................................ . (3)

(d) (i) Sodium chloride, an ionic compound, has a high melting point whereas paraffin wax, a molecular compound, melts easily.

Explain why.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(ii) Molten ionic compounds conduct electricity but molecular compounds are non-conductors, even when liquid.

Explain why.

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(Total 14 marks)

6. This is an Application and Synthesis question.

The diagrams show the giant structures of sodium chloride and diamond.

sodium chloride (melting point 801°C) diamond (melting point 4800°C)

27

(a) The equation shows how sodium choride could be formed.

Balance the equation.

Na + Cl2 → Na Cl (1)

(b) By reference to the detailed structure of sodium chloride explain fully why:

(i) sodium chloride has a quite high melting point,

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(ii) solid sodium chloride melts when it is heated strongly,

...........................................................................................................................

........................................................................................................................... (2)

(iii) molten sodium chloride will conduct electricity.

...........................................................................................................................

........................................................................................................................... (1)

(c) By reference to the detailed structure of diamond, explain why the melting point of diamond, is higher than that of sodium chloride.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 7 marks)

28

7. This is an Application and Synthesis question.

(a) By reference to their structure, explain how the particles in a piece of metal are held together and how the shape of the metal can be changed without it breaking.

(You may use a diagram in your answer.)

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

(5)

(b) Explain why metals are good conductors of electricity and suggest why this conductivity increases across the periodic table from sodium to magnesium to aluminium.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

(Total 9 marks)

29


Magnesium oxide is a compound, made up of magnesium ions and oxide ions.

Mg

Mg

O

Mg

Mg

OMg

O

O

(a) What is the charge on each magnesium ion? ............................................................. (1)

(b) Explain how the magnesium ions get this charge.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 3 marks)


Diesel oil is obtained from crude oil. It can be used as a fuel for car engines. The diagram below represents a compound found in diesel oil.

H C C C C C C C C C C C C C C C CH H H H H H H H H H H H H H H H

H H H H H H H H H H H H H H H H

H

(a) What is the formula of this compound?

..................................................................................................................................... (1)

(b) Each of the lines on the diagram above represents a covalent bond.

What is a covalent bond?

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 3 marks)

30

10. This is a Knowledge and Understanding question

The hydrogen halides (hydrogen fluoride, hydrogen chloride, hydrogen bromide and hydrogen iodide) are important chemicals.

The diagram below represents a molecule of hydrogen chloride.

ClHx

x

x xx xx xx x

x

x

x

x

x

x

x

x

(i) What type of particles are represented by the crosses (X)?

..................................................................................................................................... (1)

(ii) What type of chemical bond holds the atoms in this molecule together?

..................................................................................................................................... (1)

(iii) Would you expect hydrogen chloride to be a gas, a liquid or a solid, at room temperature and pressure? Explain your answer.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 5 marks)


Chlorine will combine with the non-metal element, carbon, to form this molecular compound.

Cl Cl

Cl

Cl

C

(a) What is the type of bond in this molecule?

..................................................................................................................................... (1)

31

(b) Explain how these bonds are formed. (You may use a diagram).

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

(2)

(Total 3 marks) 12. This is an Application question The diagram shows one molecule of the compound ammonia.

N

H H

H

Write down everything that the diagram tells you about each molecule of ammonia.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

............................................................................................................................................... (Total 4 marks)

32

Bonding – Self test questions – ANSWERS 1. (a) proton + (1) 3

both required neutron 1

both required electron − (1)

both required (b) 2.8.3 1

accept words or diagram to this effect (c) (i) 24 1

(ii) 52 1 (d) any one of 1

• gains one or more electrons accept gains an electron

• becomes an anion do not credit becomes an ion

• becomes a negative ion (e) sodium ions have a (single) positive 1

charge and chloride ions have a (single) negative charge

do not credit ‘chlorine ions’ but allow this error to be carried forward

ions with opposite charge are 1

attracted (to each other) or the positive ions and the negative ions are attracted (to each other) or the sodium ions and the chloride ions are attracted (to each other)

(positive and negative) ions are 1

arranged alternatively (in each direction or dimension)

or ions with the same charge are repelled (by each other) no mark for just ionic bonds

[10] 2. (a) electrons 3

neutrons protons

for 1 mark each (b) mass number no. of neutrons 2

14 8 for 1 mark each

[5] 3. (a) (i) idea that 2

• two hydrogen atoms share one pair of electrons • linked by a covalent bond • each then has two outer electrons / a full outer shell / two • electrons in the highest (occupied) energy level

(2 marks may be awarded for a correct electron diagram i.e. with electrons on boundary of or within marked area).

any two for 1 mark each

33

(ii) idea that 2 • helium atoms do not give / take / share electrons / react • because the (outer) shell / orbit is full

or • highest (occupied) energy level is full

(but not just “contains two electrons”) for 1 mark each

(b) idea that 2 • the (attractive) forces between molecules are weak

(not bonds between atoms) • so little energy is required / it is easy for molecules to escape from the liquid*

/ escape from other molecules* (allow evaporate / change into a gas)

for 1 mark each [6]

4. (a) compound 1 (b) oxide 1

[2] 5. (a) 3

No of protonsNo of neutronsNo of electrons

Calcium

20

Phosphorus15

Fluorine

10

for 1 mark each

(b) (i) gain of electron(s) 2

from (atoms) (of) calcium for 1 mark

(ii) Ca+ 2

gains 1 mark but superscript only

Ca2+ / Ca ++ gains 2 marks

(c) atoms 3

electrons molecule(s) not compound

each for 1 mark (d) (i) ideas that 2

• ionic - strong forces between ions • molecular - weak forces between molecules

each for 1 mark (ii) ideas that 2

• ionic - ions/charged particles are free to move • molecular -molecules do not carry a charge

each for 1 mark [14]

34

6. (a) 2 Na + Cl2 → 2 NaCl allow 2 Na+ Cl– 1 for 1 mark (allow Na + ½Cl2 → Na Cl)

(b) (i) idea that 1

• it has strong (attractive) forces/bonds between ions / charged particles

for 1 mark (not ‘..it has a rigid structure’- this defines a solid or ‘...particles

close together’ - they are in a liquid) (ii) ideas that 2

• there is increased vibration of ions / particles on heating • ions have sufficient energy to overcome attractive forces / to

break out of the • rigid structure / to move about

(must be in terms of increased energy of particles lions) each for 1 mark

(iii) • ions can go to electrodes / ions are free to move 1

for 1 mark [do not credit ‘ions carry charges’]

(c) ideas that 2

• it has stronger attractive forces between atoms/particles (not ‘ions’) • each carbon atom forms covalent bonds with neighbouring atoms

each for 1 mark [7]

7. (a) Idea that 5

the electrons do not belong to specific atoms/delocalised electrons [credit if done on appropriate diagram] metal atoms form positive ions the attraction which exists between particles with opposite charges, holds the metal together no specific bonds exist between adjacent atoms/ions atoms/ions can slide over each other so allowing metals to bend

each for 1 mark (b) some electrons in the structure are delocalised/free to move 4

for 1 mark these free electrons carry the electric current

for 1 mark from left to right across the period, atoms of elements have

more free electrons gains 1 mark

but from left to right across the period, atoms of elements have more free electrons because they have more electrons in the outer shells

gains 2 marks [9]

8. (a) positive 1 for 1 mark

(b) any reference to loss of electrons 2 for 1 mark

reference to charge being +2 (in (a)) or to loss of 2 electrons (in (b))

for 1 mark [3]

35

9. (a) C16 H34 1 for 1 mark

(b) electron 2

gains 1 mark but

shared electrons gains 2 marks

[3] 10. (i) electrons 1

for 1 mark (ii) covalent 1

for 1 mark (iii) made of small molecules: 3

usually gas or liquid ) dependent on have low melting points ) having first have low boiling points ) point above forces between molecules are weak

any 1 for 1 mark [5]

11. (a) covalent bonds 1

for 1 mark (b) any reference to shared electrons 2

gains 1 mark but

idea that bond is shared pair of electrons gains 2 marks

[3] 12. idea that

• contains nitrogen atoms contains hydrogen atoms atoms are chemically bonded NOT linked/joined ratio of one nitrogen to three hydrogen (atoms)

formula of ammonia is NH3 for 1 mark each

[4]

36

Quantitative chemistry – self test questions


Calculate the formula mass (Mr), of the compound

calcium hydroxide, Ca (OH)2.

(Show your working)

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................ (Total 3 marks)


The symbol equation below shows the reduction of iron (III) oxide by carbon monoxide.

Fe2O3 + 3CO → 2Fe + 3CO2

(a) Calculate the formula mass of iron (III) oxide.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (3)

(b) What percentage (%) of iron (III) oxide is iron?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Answer ........................................ % (2)

(Total 5 marks)

37

3. This is a Knowledge and Understanding / Application question.

(a) Calculate the formula mass (Mr) of the compound iron (III) oxide, Fe2O3.

(Show your working.)

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(b) Calculate the mass of iron produced when 32g of iron (III) oxide is completely reduced by aluminium.

The reaction is shown in the symbol equation:

Fe2O3 + 2Al → 2Fe + Al2O3

(Show your working.)

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Answer = ..................................... grams (3)

(Total 6 marks)

4. This is a Knowledge and Understanding / Application question. Calcium carbonate tablets are used to treat people with calcium deficiency.

Calcifull Tablets

CaActive ingredient:Calcium carbonate CaCO

(Each tablet contains 1.25g CaCO )3

3

38

(a) Calculate the relative formula mass (Mr)of calcium carbonate.

Relative atomic masses: C = 12; O = 16; Ca = 40.

.....................................................................................................................................

.....................................................................................................................................

Relative formula mass = .............................. (2)

(b) Calculate the percentage of calcium in calcium carbonate, CaCO3.

.....................................................................................................................................

.....................................................................................................................................

Percentage of calcium = .......................... % (2)

(c) Calculate the mass of calcium in each tablet.

.....................................................................................................................................

.....................................................................................................................................

Mass of calcium = .................................... g (2)

(d) An unwanted side effect of this medicine is that it can cause the patient to have ‘wind’ (too much gas in the intestine).

The equation below represents the reaction between calcium carbonate and hydrochloric acid (the acid present in the stomach).

CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + H2O (l) + CO2 (g)

Suggest why the patient may suffer from ‘wind’.

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 7 marks)

39

Quantitative Chemistry – Answers to self test questions. 1. Ca = 40 (OH)2 = (16 + 1)2 or 34 gain 1 mark each but Mr = 74 gains 3 marks

[3] 2. (a) evidence of Fe = 56, O = 16 3

gains 1 mark but (56 × 2) + (16 × 3) gains 2 marks but 160 gains 3 marks (b) evidence of 112*/160 2

gains 1 mark but 70*

gains 2 marks * (credit answers consistent with part (a))

[5] 3. (a) Fe2 [56 × 2] or 112 3

O3 [16 × 3] or 48 each gain 1 mark

but Mr = 160 gains 3 marks

(b) [Fe2 O3 + 2A1 → 2Fe + A12 O3] 3 160 → 112 (NB Credit if unworked

(or value (or value but should be totalled) from (a)) from (a))

gains 1 mark but

32 g. of Fe2 O3 → 32/160 × 112 gains 2 marks

but = 22.4

gains 3 marks [6]

4. (a) 100 2

ignore units 40 + 12 + (3 × 16) for 1 mark

(b) 40 2 (ecf from part (a) can get 2 marks)

100)(

40×

atheir for 1 mark

(c) 0.5 2 (ecf from part (b) can get 2 marks)

⎟⎠⎞

⎜⎝⎛×

100)(25.1 btheir or other correct working for 1 mark

(d) gas produced or carbon dioxide / CO2 produced 1 [7]

40

Electrolysis – self test questions


Copper metal can be extracted from a solution of copper(II) chloride.

positiveelectrode

negativeelectrode

solution ofcopper (II)chloride

Copper chloride is an ionic compound.

State where the copper would collect and explain your answer fully.

...............................................................................................................................................

...............................................................................................................................................

............................................................................................................................................... (Total 2 marks)

2. This is mainly a Knowledge and Understanding question (with Application at the end !)

Chlorine, hydrogen and sodium hydroxide are produced by the electrolysis of sodium chloride solution. A student passed electricity through sodium chloride solution using the apparatus shown in the diagram.

41

(a) Name:

Gas A .............................................................

Gas B ............................................................. (1)

(b) Describe and give the result of a test you could do in a school laboratory to find out which gas is chlorine.

Test ............................................................................................................................

....................................................................................................................................

Result (what you would see) .....................................................................................

.................................................................................................................................... (2)

(c) Chlorine is used for treating water for drinking and in swimming pools. Why?

.................................................................................................................................... (1)

(d) (i) Balance the half equation for the production of hydrogen at the electrode.

................ H+ + .............. e– → H2 (1)

(ii) Which word, from the list, best describes the reaction in part (d)(i)? Put a ring around the correct word.

decomposition cracking neutralisation

oxidation reduction (1)

(e) In an experiment the student collected 24 cm³ of chlorine gas, Cl2 , at room temperature and pressure. Calculate the mass of this volume of gas. (Relative atomic mass of Cl = 35.5. The volume of the relative formula mass (Mr ) of any gas at room temperature and pressure is 24 litres).

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 9 marks)

42


The diagram below shows the electrolysis of sodium chloride solution, in the laboratory.

+ –Power supply

NegativeelectrodePositive

electrode(chlorine formedhere)

sodium chloridesolution

(a) Which gas forms at the negative electrode? .............................................................. (1)

(b) Explain why chlorine gas forms at the positive electrode.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(c) State one use of chlorine gas.

..................................................................................................................................... (1)

(Total 4 marks)

43

4. This is mainly an Application question. The diagram shows electrolysis of sodium chloride solution.

chlorine gas

positiveelectrode (carbon)

power supply

negativeelectrode (carbon)

hydrogen gas


chlorine gas

positiveelectrode (carbon)

power supply

negativeelectrode (carbon)

hydrogen gas


(a) Complete and balance these equations to show the reactions during electrolysis.

At the positive electrode

Cl– – e– → Cl2

At the negative electrode

Na → Na (2)

(b) Silver halides such as silver chloride and silver bromide are used in photography. The equation shows a reaction to prepare a silver halide.

3(aq)(s)3(aq)(aq) NaNOAgBrAgNONaBr2product1productreactants

+⎯→⎯+

Name and describe the products of this reaction, in words, as fully as you can.

product 1

.....................................................................................................................................

.....................................................................................................................................

product 2

.....................................................................................................................................

..................................................................................................................................... (4)

(Total 6 marks)

44

Electrolysis – answers to self test questions

1. copper collects at the negative electrode 2 copper positive ions

each for 1 mark [2]

2. (a) Gas A = chlorine / Cl2 (not Cl) 1 Gas B = hydrogen / H2 (not H)

both correct for 1 mark

(b) universal indicator paper / litmus paper (red or blue) / pH paper / starch iodide paper/or solutions / a named suitable indicator bleached (owtte) (not discoloured) / starch – iodide turns blue (a reasoned answer based on the test for hydrogen can gain one mark for example: test both tubes with a burning splint - the one containing hydrogen will pop and the one containing chlorine will not)

for 1 mark each 2

(c) kills germs (owtte) 1 both correct for 1 mark

(d) (i) 2H+ + 2e– → H2 1

multiples accepted such as 4 H+ + 4e– → 2H2 or H+ + e– → 1/2 H2

for one mark

(ii) reduction / need not be circled if it is clearly marked 1 e.g. underlined

for one mark

(e) (moles of Cl2) = 24 / 24000 = 0.001 (24 / 24000 gains one mark or 0.001/ 1/1000) (1 mole of chlorine) = 2 × 35.5 = 71(g) 3 (mass of chlorine) = 0.001 × 71 = 0.071g (correct answer = 3)

(if they give no units or g this is acceptable but other units -1 mark)

(if they do not get the correct answer we then look for working marks - general principle is one mark lost for each mistake)

giving the equation volume / 24000 = mass of gas / Mr (one mark)

answer 0.0355 = 2 marks (without working)

answers based on Mr of chlorine as 35.5 are worth a maximum of 2 marks for 1 mark each

[9]

45

3. (a) hydrogen 1 for 1 mark

(b) chloride ions are negative; 2 negative ions move to positive electrode

each for 1 mark

(c) any one use of chlorine e.g. 1 sterilisation; bleaching; making plastics

any one for 1 mark [4]

4. (a) 2Cl– – 2e– → Cl2 (allow unaltered LHS to produce ½ Cl2) 2

Na+ + e– → Na (allow x 2 for all terms)

(credit candidates who point out that hydrogen / H2 is in fact produced) for 1 mark each

(b) for product 1*, idea of 4 a solid / precipitate or silver bromide

gains 1 mark

but solid / a precipitate of silver bromide

gains 2 marks

for product 2*, idea of aqueous / a solution / dissolved (in water) / or sodium nitrate

gains 1 mark (do not allow liquid)

but aqueous / a solution / dissolved (in water) of sodium nitrate

(*do not credit formulae) gains 2 marks

[6]

46

Why is Ammonia important ?

Types of reactions – self test questions


This label has been taken from a packet of indigestion tablets.

The back of the packet tells you that the tablets work by neutralising some of the acid in your stomach.

DISPERSE IN THE MOUTH

HEARTBURNACID INDIGESTIONTRAPPED WIND

FAST EFFECTIVE RELIEF FROM3 KINDS OF INDIGESTION

®

(a) What happens to the pH inside your stomach as the tablets neutralise some of the acid?

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Some students decide to find out how many tablets are needed to neutralise some acid in a beaker.

The diagrams show what they did. How would the students know when the acid had been neutralised?

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 4 marks)

47


The diagrams show what happens when an acid is added to an alkali.

Indicatoris green

Indicatoris red

Flask containsdilute sodium

hydroxide solution+ universal indicator.

Indicator is purple

STAGE 1 STAGE 2 STAGE 3

More dilute hydrochloricacid added and

mixed

Dilute hydrochloricacid added and

mixed

(a) What is present in the solution at stages 2 and 3 apart from universal indicator and water?

(i) At stage 2 .........................................................................................................

(ii) At stage 3.......................................................................................................... (3)

(b) Write an ionic equation to show how water is formed in this reaction and state the sources of the ions.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 6 marks)


Some students slowly add solution Y to solution X.

The graph shows what happens to the pH of the solution in the beaker as they do this.

A

B

C

14

7

0

pH13

1

volume of Y added(cm )3

5 10 15 20

Solution X

Solution Y

48

(a) Choose words from this list to complete the sentences below.

acidic alkaline neutral

At point A on the graph the solution in the beaker is ...............................................

At point B on the graph the solution in the beaker is ...............................................

At point C on the graph the solution in the beaker is ............................................... (2)

(b) Describe, as fully as you can, what happens to the pH of the mixture as solution Y is slowly added.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (5)

(Total 7 marks)


Some drain cleaners contain a mixture of sodium hydroxide and powdered aluminium. When the mixture is poured into a drain it mixes with water and a chemical reaction takes place. The heat from the reaction helps to melt grease in the drain. Hydrogen gas is produced which stirs up the particles and helps to unclog the drain.

(a) Balance the equation for the reaction.

2Al(s) + ........ NaOH(aq) + ......... H2O → .........NaAl(OH)4(aq) + 3H2 (2)

(b) Why do the solid sodium hydroxide and aluminium powder not react when stored in a sealed container?

..................................................................................................................................... (1)

(c) Sodium hydroxide is a strong alkali and would react with any acids in the drain.

(i) Name the ion produced when any alkali is dissolved in water.

........................................................................................................................... (1)

49

(ii) Name the ion produced when any acid is dissolved in water.

........................................................................................................................... (1)

(iii) Name the compound formed when these ions react with each other.

........................................................................................................................... (1)

(Total 6 marks)


The symbol equation below shows the reaction when methane burns in oxygen.

CH4 + 2O2 → CO2 + 2H2O

An energy level diagram for this reaction is shown below.

methane +oxygen

(reactants)Energylevel

y

z

x

carbon dioxide +water (products)

(a) Which chemical bonds are broken and which are formed during this reaction?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

50

(b) Explain the significance of x, y and z on the energy level diagram in terms of the energy transfers which occur when these chemical bonds are broken and formed.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (5)

(Total 9 marks) 6. This is an Application question. Methane and oxygen react together to produce carbon dioxide and water.

4 2 2 2CH + 2O CO + 2H O 818 kJ of energy is given outto the surroundings for eachformula mass (mole) ofmethane that reacts.

The methane gas will not burn in oxygen until a flame is applied, but once lit it continues to burn.

(a) Explain why energy must be supplied to start the reaction but it continues by itself once started.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

51

(b) Sketch an energy level diagram for the reaction and indicate on the diagram the nett energy released.

Energy

Time (3)

(Total 7 marks)

52

Types of Reaction – answers to self test questions

1. (a) rises 2

reference to figures in correct range (1 to just less than 7)

for 1 mark each (b) any reference to indicator 2

gains 1 mark but

indicator green gains 2 marks

[4] 2. (a) (i) sodium ions and chloride ions 1

(allow sodium chloride/salt) [not “chlorine”]

for 1 mark (ii) sodium ions and chloride ions 2

(allow sodium chloride/salt) for 1 mark

H + ions (allow hydrochloric acid) for 1 mark

(b) H+ + OH– → H2O [N.B Na+ and Cl– may also be present] 3

H+ ions from acid OH– ions from alkali

each for 1 mark [N.B First mark lost if changes on ions not shown]

[6] 3. (a) acidic } 2

neutral } in this order alkaline}

all correct 2 marks one correct 1 mark

(b) ideas that

• nothing happens at first (to pH) / pH stays the same • then (rapidly) changes / increases • then stays at same (higher) level

(c) reference to 5

• change being from pH1 to pH13 / pH goes up • change commencing with 10 cm3 (of Y) • change ceasing with 11cm3 (of y) • neutral / ph7 with 10.5 cm3 / at B

any five for 1 mark each [7]

53

4. (a) (2) : (6) : (2) 2

All 3 correct gains 2 marks 2 correct gains 1 mark

(b) no water present/moist air cannot enter/do not thoroughly mix/ 1

must be in solution etc. for 1 mark

(c) (i) hydroxide (ion) / OH– 1

for 1 mark (ii) hydrogen (ion) / H+ 1

for 1 mark (iii) water/H2O/hydrogen oxide 1

for 1 mark [6]

5. (a) breaking of C-H bonds 4

breaking of O-O bonds making of C-O bonds

for 1 mark each making of H-O bonds (b) X energy needed to break bonds 5

has to be supplied/activation energy Y energy released when bonds form Z = Y-X

overall, energy is released/reaction is exothermic each for 1 mark

[9] 6. (a) idea that

(max 4) existing bonds must first be broken

for 1 mark (credit molecules / atoms more likely to react when they collide)

energy is released when new bonds form gains 1 mark

but more energy is released when new bonds form

gains 2 marks or

overall reaction exothermic this breaks more bonds so the reaction continues

for 1 mark (b) • reactant level higher than product level (names of reactants and 3

products not required) • indication that activation energy required (i.e. the “hump”) • any correct indication of nett energy change

(i.e. between product and reactant levels even if other marks not gained)

for 1 mark each [7]

54

Reversible reactions – self test questions


A student heated some blue copper sulphate crystals. The crystals turned into white copper sulphate.

Heat

Coppersulphatecrystals

Steam

(a) The blue copper sulphate had to be heated to change it into white copper sulphate.

State whether the reaction was exothermic or endothermic. ....................................

Explain your answer.

.....................................................................................................................................

..................................................................................................................................... (1)

(b) The word equation for this reaction is shown below.

hydratedcopper sulphate

(blue)

anhydrouscopper sulphate

(white)[+ heat energy] + water

(i) What does the symbol tell you about this reaction?

.......................................................................................................................... (1)

(ii) How could the student turn the white powder back to blue?

.......................................................................................................................... (1)

(Total 3 marks)

55


The diagram shows the final stages in the manufacture of ammonia.

Nitrogen and Hydrogen450°C and 200 atmospheres

ConverterIron

Cooler

Ammonia

(a) Why is iron used in the converter?

....................................................................................................................................

.................................................................................................................................... (1)

(b) Write the word equation for the reaction in the converter.

....................................... + ....................................... ..................................

(1)

(c) The yield of ammonia is only about 15%.

(i) Why can the yield not be 100%?

..........................................................................................................................

.......................................................................................................................... (1)

(ii) Describe what happens to the mixture of gases after it leaves the converter.

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(Total 5 marks)

56


Ammonia is manufactured by the Haber Process, where nitrogen and hydrogen react together as follows:

N2 + 3H2 ⇔ 2NH3

The reaction is reversible. A balance is eventually reached when ammonia is being formed at the same rate at which it is decomposing.

This point is called ‘equilibrium’.

PERCENTAGE OF AMMONIA AT EQUILIBRIUM

PRESSURE (ATM)

25100400

100ºC 300ºC 500ºC

91.796.799.4

27.452.579.7

2.910.631.9

(a) (i) What is meant by a ‘reversible reaction’?

.........................................................................................................................

......................................................................................................................... (1)

(ii) Which substances are present in the mixture at equilibrium?

......................................................................................................................... (1)

(b) (i) Under what conditions shown in the table is the maximum yield of ammonia obtained?

.........................................................................................................................

......................................................................................................................... (2)

(ii) The Haber Process is usually carried out at a higher temperature than that which would produce the maximum yield. Suggest why.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (2)

57

(c) Ammonia can be converted into nitric acid in three stages:

Stage 1 Ammonia reacts with oxygen from the air to form nitrogen monoxide and water

4NH3 + 5O2 4NO + 6H2O

Stage 2 On cooling, nitrogen monoxide reacts with oxygen from the air to form nitrogen dioxide.

Stage 3 Nitrogen dioxide reacts with water to form nitric acid and nitrogen monoxide.

(i) Describe the conditions under which the reaction in Stage 1 takes place.

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (3)

(ii) Balance the equation for the reaction at Stage 2.

NO + O2 NO2 (1)

(iii) Balance the equation for the reaction at Stage 3.

NO2 + H2O HNO3 + NO (1)

(d) The chemical plant for manufacturing ammonia is often on the same site as plants manufacturing nitric acid and fertilisers.

(i) What advantages will this have for the manufacturing company?

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (2)

(ii) Briefly describe two important ways in which it is possible to reduce the environmental impact of such plants on the surrounding area.

1 ......................................................................................................................

.........................................................................................................................

2 ......................................................................................................................

......................................................................................................................... (2)

(Total 15 marks)

58

4. This is an Application question. The reaction of methane with steam is used in industry to make hydrogen.

(a) One of the reactions in this process is represented by this equation.

CH4 (g) + H2O CO (g) + 3H2 (g)

The forward reaction is endothermic.

State the conditions of temperature and pressure that would give the maximum yield of hydrogen.

Explain your answers.

(i) Temperature

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(ii) Pressure

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(iii) Which one of the following metals is most likely to be a catalyst for this process? Draw a ring around your answer.

aluminium lead magnesium nickel sodium

Give a reason for your choice.

..........................................................................................................................

.......................................................................................................................... (1)

59

(b) A second stage in this process is represented by this equation.

C O + O C O + H HO

H H

(i) Use the bond energies given in the table to help you to calculate the nett energy transfer (energy change) for this reaction.

Bond Bond energy in kJ/mol

C ≡ O 1077

C = O 805

H – H 436

O – H 464

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

Nett energy transfer = ...................................... kJ/mol (3)

(ii) State whether this reaction is exothermic or endothermic. .............................

Explain, by reference to your calculation, how you know.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(Total 10 marks)

60

Reversible reactions – answers to self test questions 1. (a) endothermic and because it takes in heat / energy 1

both for one mark (b) (i) reversible reaction (or explanation) 1

(ii) add water 1 do not accept cooling or reverse the reaction

[3] 2. (a) as a catalyst 1

accept to speed up the reaction (equilibrium)

(b) nitrogen + hydrogen ammonia 1

N2 + H2 NH3 accept mixed formula / word equations ignore balancing

(c) (i) the reaction is reversible / an equilibrium 1

accept that ammonia can break down again into nitrogen and hydrogen accept reaction goes both ways do not accept some nitrogen and hydrogen do not react

(ii) (the gases are cooled) 1

no marks as given in the diagram accept correct formulae NH3, N2 H2

ammonia removed as a liquid 1 accept ammonia liquefies or condenses

nitrogen and hydrogen are recycled accept nitrogen and hydrogen are put back through the converter accept ‘other gases’ only if ammonia identified for first mark

[5] 3. (a) (i) idea that it is 1

a reaction in which the products can themselves react to reform the original substance or a reaction that can go in either direction (allow explanation in terms of the specific reaction in the question)

for 1 mark (ii) nitrogen, hydrogen and ammonia 1

(allow formulae) for 1 mark

(b) (i) high pressure/400 atm 2

low temperature/100°C for 1 mark each

(ii) higher rate of reaction 2

good rate of production or idea that more economic (ally viable) (allow catalyst more effective at higher temperature)

for 1 mark each

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(c) (i) ideas that it involves use of catalyst

gains 1 mark but 2

use of platinum catalyst gains 2 marks

high temperature/900°C 1 for 1 mark

(ii) 2 NO + O2 → 2NO2 1

for 1 mark each (iii) 3 NO2 + H2O → 2HNO3+NO 1

for 1 mark each (d) (i) references to 2

• transport reductions • economic savings • saves time • guaranteed consumer/supplier

for 1 mark each (ii) • selection of site 2

• design of plant • safe disposal of waste • make gas emissions safe(r) • monitoring/safety checks • reduction of waste gas emissions • research into more efficient processes • research into energy savings/use of cooling water • training of staff re: emergency procedures • warning/evacuation procedures for the community (or any two sensible suggestions)

any two for 1 mark each [15]

4. (a) (i) high temperature 1

accept temperature given if ≥ 400°C ignore value if “high” stated, unless silly value

endothermic or reaction takes in energy

or Δ H is +ve 1 independent marks

(ii) low pressure 1

or up to and including 10 atmospheres (low pressure) favours a reaction in which

more molecules are formed 1 2 moles → 4 moles (2 molecules → 4 molecules) independent marks

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(iii) nickel and it is a transition / transitional 1

element / metal (owtte) or nickel and variable oxidation state / number or it is similar to other named transition elements e.g. iron

(b) (i) (bonds broken =) 2005 (kJ) 1

(bonds formed =) 2046 (kJ) 1 energy change =

2005 – 2046 = (–)41 1 for correct subtraction ignore sign

(ii) (exothermic)

if in part (b)(i) answer is not 41 answer is consequential on endothermic or exothermic shown accept correct reasoning for incorrect answer from (b)(i)

energy given out forming new bonds 1 do not accept energy needed to form new bonds

greater than energy put in to break old bonds 1

accept exothermic and more energy given out than taken in for 1 mark accept negative value for energy change or energy in products less than energy in reactants for 1 mark

[10]

63

Rates of Reaction – self test questions

1. This is a Knowledge and Understanding (with a little Application) question.

Some students were investigating how fast hydrogen gas is released in the reaction between magnesium and dilute hydrochloric acid.

To begin with they used 0.1 g of magnesium ribbon.

Next, they repeated the experiment using 0.1 g of magnesium powder.

In each case, they used enough acid to react with all the metal.

(a) Their results are shown on the graph below.

RibbonPowd

erVolume ofhydrogenproduced

(cm³)

Time (seconds)

Hydrogen is produced in both the reactions.

Use the information on the graph to describe two other ways in which the two reactions are similar.

1. .................................................................................................................................

.....................................................................................................................................

2. .................................................................................................................................

..................................................................................................................................... (2)

(b) Describe one way in which the reactions are different.

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 3 marks)

64


A student does an experiment to examine the rate of reaction between magnesium and dilute hydrochloric acid. She adds 25 cm³ of the acid to a weighed amount of the metal. The reaction produces hydrogen gas.

magnesium + hydrochloricacid

magnesium + hydrogenchloride

She collects the gas and measures the volume collected at one minute intervals. All the metal reacted but there was some acid left unreacted. Her results are shown on the graph.

50

40

30

20

10

02 4 6 8 10 12

Volume ofhydrogen

(cm )3

(a) The diagram shows part of the apparatus she used for the experiment. Complete the diagram to show how the student could collect the hydrogen produced and measure the volume after each minute.

(2)

65

(b) (i) When is the rate of reaction at its fastest? ..........................................................................................................................

(1) (ii) State one way in which she could increase the rate of reaction.

.......................................................................................................................... (1)

(c) (i) What is the total volume of hydrogen collected in the experiment? ................................................................................................................... cm³

(1) (ii) State one way in which she could increase the final volume of hydrogen collected.

.......................................................................................................................... (1)

(Total 6 marks)

3. This is a Knowledge and Understanding (with a little Application) question.

When a catalyst such as manganese oxide is added to hydrogen peroxide solution, H2O2, the hydrogen peroxide decomposes to give off oxygen.

(a) (i) Describe how to test for oxygen.

...........................................................................................................................

........................................................................................................................... (2)

(ii) Complete and balance the equation for the decomposition of hydrogen peroxide.

2H2O2 → ..................................... + ....................................... (3)

(b) The graph shows the volume of gas given off during an experiment using hydrogen peroxide solution and manganese oxide.

60

50

40

30

20

10

00 20 40 60 80 100 120 140 160

Time in seconds

Volume ofgas givenoff in cm3

Draw, on the axes above, a graph to show the result you would expect if the volume of hydrogen peroxide solution had been the same, but it was twice as concentrated.

(3) (Total 8 marks)

66

4. This is an Application question. Solutions A and B are colourless.

When they are mixed, they react and turn blue after a period of time. A student investigated how temperature affected the rate of reaction between solutions A and B. The rate was measured by timing how long the mixture took to turn blue at different temperatures.

The results are shown in the table.

Temperature in °C 22 25 30 34 45 51

Time taken to turn blue, in seconds 290 250 238 200 170 160

(a) (i) Draw a graph for these results with a line of best fit.

300

290

280

270

260

250

240

230

220

210

200

190

180

170

160

150

00 10 20 30 40 50 60

Temperature in °C

Time takento turn blue,in seconds

(2)

67

(ii) Use your graph to find out how long it takes the solution to turn blue at 40°C.

Time = ............................... s (1)

(b) One of the results is anomalous.

(i) Complete this sentence.

The result at.............°C is anomalous. (1)

(ii) Suggest two possible causes of this anomalous result.

1 ........................................................................................................................

...........................................................................................................................

2 ........................................................................................................................

........................................................................................................................... (2)

(c) Explain, in terms of particles, why increasing the temperature increases the rate of reaction.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 9 marks)

68

Rates of Reaction – answers to self test questions 1. (a) both reactions slow down with time; 2

both reactions produce same volume of hydrogen each for 1 mark

(b) idea rate is faster with powder 1

or idea rate is slower with ribbon (allow powder completed before ribbon)

for 1 mark [3]

2. (a) (must be possible for the gas to enter and displace the water) 2

or other suitable apparatus • apparatus to collect the gas correctly assembled

for 1 mark • calibrated collection vessel (award even if diagram is wrong)

for 1 mark

(b) (i) at the start / in the first 1/2 minutes (or any time within this range) 1 for 1 mark

(ii) increase the temperature / use smaller pieces of metal / 1 use more metal / increase the surface area of the metal / add a catalyst / shake the flask / increase the concentration / strength of the acid

for 1 mark (c) (i) 48 1

for 1 mark (ii) increase the amount of magnesium used 1

for 1 mark (do not allow increase the amount of acid used)

[6] 3. (a) (i) re-lights 1

lights or lights with a pop a glowing splint 1

glowing or smouldering splint (ii) → 2H2O + O2

each formula for 1 mark 2 balanced equation 1 mark 1 2H2 or O2 gets one mark only (for O2)

(b) graph steeper 1

becomes horizontal 1 reaches twice the height, 40 cm3 ±1 cm3 1

69

60

50

40

30

20

10

0

Time in seconds

Volume ofgas givenoff in cm3

0 20 40 60 80 100 120 140 160

[8]

4. (a) (i) plotting points accurately 1

± 21 square

sensible smooth curve 1 must not join dots

(ii) as read from their graph 1 (b) (i) 30 (°C) 1

(ii) any two from: 2 ● eg error in timing ● temperature not exactly measured ● different amounts of reagents ● different concentrations of A and B ● any other sensible reason

(c) any three from: 3

● particles gain energy ● move faster ● collide more often ● collide with more force / energy / harder /

more successful collisions / more collisions with activation energy

[9]

70

Making salts – self test questions

1. This is a Knowledge and Understanding question

Bordeaux Mixture controls some fungal infections on plants.

A student wanted to make some Bordeaux Mixture.

Controls potatoand tomato blight,peach leaf curl,leaf moulds andother diseases onfruit trees.

BORDEAUXMIXTURE

Do not breathe in dust.Wash hands after use.Store in a safe place.

Contains: calcium oxide copper sulphate

(a) The student knew that calcium oxide could be made by heating limestone. Limestone contains calcium carbonate, CaCO3.

(i) Write the word equation for this reaction.

........................................................................................................................... (1)

(ii) What type of reaction is this?

........................................................................................................................... (1)

(b) The student knew that copper sulphate, CuSO4, could be made by the following general reaction.

acid + base → salt + water

(i) What type of reaction is this?

........................................................................................................................... (1)

(ii) The base used is copper oxide. Name and give the chemical formula of the acid used.

Name ................................................................................................................

Chemical formula ............................................................................................. (2)

71

(c) The student wrote about how the copper sulphate was made.

“Some of the acid was warmed. Copper oxide was added. The mixture was stirred. More copper oxide was added until no more would react. The mixture was then filtered.”

(i) Why was the acid warmed?

...........................................................................................................................

........................................................................................................................... (1)

(ii) Copper oxide was added until no more would react. Explain why.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(iii) The filtration apparatus is shown.

Filter paper

Filter funnel

Beaker

Describe and explain what happens as the mixture is filtered.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 10 marks)

72


(i) Which acid from the list should the student add to sodium hydroxide solution to make sodium sulphate?

ethanoic acid hydrochloric acid nitric acid sulphuric acid

..................................................................................................................................... (1)

(ii) When the acid was added to the alkali the beaker became warm. Name the type of reaction that releases heat.

..................................................................................................................................... (1)

(iii) Use a Periodic Table to help you to write the formula of sodium sulphate.

Formula: ..................................................................................................................... (1)

(Total 3 marks) 3. When a solution of lead nitrate is added to a solution of sodium chloride, a white precipitate of

lead chloride is produced.

precipitate oflead chloridesolution of

sodium chloride

solution oflead nitrate

(a) (i) Why is a precipitate formed?

...........................................................................................................................

........................................................................................................................... (1)

(ii) Complete and balance the equation for this precipitation reaction.

Pb+2(aq) + Cl–(aq) →

(3)

73

(b) Complete the table below by writing in the name and formula of the precipitate formed for each reaction. If there is no precipitate, write “no precipitate”.

SOLUTION 1 SOLUTION 2NAME OF

PRECIPITATE FORMEDFORMULAADDED

TO

(i) coppersulphate

sodiumhydroxide

magnesiumsulphate

zincnitrate

(ii) leadnitrate

(iii) sodiumchloride

(5)

(Total 9 marks)

74

Making salts – answers to self review questions 1. (a) (i) 1

calcium

carbonate

→ calcium

oxide

+ carbon

dioxide

accept CaO3 → CaO + CO2 (ii) (thermal) decomposition 1

accept endothermic accept reversible

(b) (i) neutralisation 1

accept exothermic (ii) sulphuric (acid)

H2SO4 2 (c) (i) to speed up the reaction 1

accept to increase the rate of reaction or to increase the number or rate of collisions do not accept “dissolves” copper oxide faster

(ii) all acid reacts 1

accept there will be no acid left or acid used up acid is neutralised (for 2 marks) 1

do not accept to form a concentrated or saturated solution (excess) copper oxide collects in filter 1

paper accept larger particles (of copper oxide) cannot pass through filter paper

copper sulphate solution passes 1

through the filter paper accept dissolved copper sulphate passes through filter paper or smaller particles (of copper sulphate) in solution (liquid) pass through filter paper accept (black) solid collects in filter paper and filtrate or soluble solid or (blue) solution (liquid) passes through filter paper for 1 mark only

[10]

75

2. (i) sulphuric acid / H2SO4 accept sulfuric 1 for one mark

(ii) exothermic 1 for one mark

(iii) Na2SO4 / (Na)2SO4 / Na2(SO4) / (Na+)2SO42– 1 for one mark lower case O(Na2SO4) not accepted / tops of subscripted letters should be in line or lower than lower case letters of symbols

[3]

3. (a) (i) lead chloride/product of lead + chloride 1

ions is insoluble (in water) for 1 mark

(ii) Pb2+ + 2C1¯ → PbC12 *(s) 3

(allow (Pb)2+ 2 (C1–) ) formula solid state symbol balancing for 1 mark each

(b) copper hydroxide Cu(OH)2 5 each for 1 mark

lead sulphate PbSO4 each for 1 mark

no precipitate for 1 mark

Allow 1 mark for correct formula Na2SO4 in (i)

Allow 1 mark for correct formula Mg (NO3)2 in (ii)

0 marks for any formula in (iii) [9]

chemistry application questions 2010

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