chemistry mock

Question Answer book

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P.C.s Chemistry

S.3 Mock paper

Time allowed: 1 hour Max. Mark: 100

Question-Answer book


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Section A:

MC Question (40marks, 2@)

1. Which of the following descriptions about the electric charges on neutron, proton

and electron is correct?

Neutron Proton Electron

A. Positive Positive Negative

B. Positive Neutral Positive

C. Neutral Negative Positive

D. Neutral Positive Negative

2. Which of the following statements about helium is INCORRECT?

A. Helium is less dense than air.

B. Helium is a noble gas and form the duplet rule.

C. Helium atom has an octet structure.

D. Helium does not burn.

3. Refer to the following elements:

Element Atomic number Relative atomic number

P 7 14.0

Q 20 40.1

Elements P and Q combine to form a compound X. Which of the following

statements about X are correct?

(1) X is formed by electron sharing.

(2) X is a solid at room temperature and pressure.

(3) The formula mass of X is 148.3.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only


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4. Rubidium Rb is a group I element below potassium of the periodic table. Which of

the following statements about rubidium are correct?

(1) Its oxide is a crystalline solid.

(2) It can be obtained by heating its oxide with carbon.

(3) The chemical formula of its oxide is Rb2O.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

5. A substances Y melts at 1850o. It does not conduct electricity in solid or molten

state. T probable has

A a metallic structure

B a giant covalent structure

C a simple molecular structure

D an ionic structure

6. Which of the following molecules has the greatest number of lone pair electrons?

A Ammonia

B Carbon monoxide

C Ethane (C2H6)

D Ozone (O3)

7. Xenon is a noble gas, which is the middle of Group 0 in the periodic table. Which

of the following prediction is INCORRECT?

A It exists as monoatomic molecules in the gaseous state

B It is colourless

C It cannot form any compound with other elements.

D It is denser than air.


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Directions: Questions 8 and 9 refer to the following table which shows some

properties of four different substances:

Substance Melting Point

(oC)

Solubility

solid liquid

W 1 565 non-conductor conductor

X 1 610 non-conductor non-conductor

Y 40 non-conductor non-conductor

Z 1 670 conductor conductor

8. Which substance has a giant covalent structure?

A W

B X

C Y

D Z

9. Which of the following statements is correct?

A The compound formed between Z and chlorine conducts electricity in

molten state.

B X is soluble in heptane (a non-aqueous solvent).

C Y is a liquid at room temperature and pressure.

D W is malleable.

10. Caesium Cs is a Group I element and chlorine is a Group VII element. Which of

..the following statements concerning caesium chloride is INCORRECT?

A Caesium chloride must be stored in paraffin oil.

B Caesium chloride has a high melting point.

C Caesium chloride is a white compound.

D Caesium chloride is soluble in water.

11. Which of the following molecules has the smallest number of lone pair electrons?

A Ammonia

B Carbon monoxide

C Boron trifluoride

D Ozone (O3)


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12. Which of the following reagents is / are commonly stored in brown bottles?

(1) Calcium carbonate

(2) Concentrated nitric acid

(3) Sodium hydroxide solution

A (1) only

B (2) only

C (2) and (3) only

D (1), (2) and (3)

13. Which of the following statements about an atom is/are correct?

(1) Nucleus carries no charge.

(2) The mass of an atom concentrates at the nucleus.

(3) Electrons are moving at high speed around an atom.

A. (1) only

B. (2) only

C. (1) and (3) only

D. (1), (2) and (3)

14. Barium is an alkaline earth metal. The chemical formula of its carbonate is

A BaCO3.

B Ba2CO3.

C Ba(CO3)2.

D Ba3(CO3)2.

15. The chemical formula for the nitride of metal X is X3N2. The chemical formula of

the sulphate of X is

A XSO4.

B X2SO4.

C X(SO4)2.

D X2(SO4)3.


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16. Elements X and Y form a compound with the following electronic structure:

(Only electrons in the outermost shells are shown.)

Which of the following combinations is correct?

X Y

A Be O

B Al S

C Mg N

D C O

17. What is the colour of an aqueous solution of iron(III) nitrate?

A Pale green

B Yellow

C Blue

D Pink

Directions: Please refer to the following instructions:

A Both statements are true and the 2nd statement is a correct explanation of the

1st statement.

B Both statements are true but the 2nd statement is NOT a correct explanation of

the 1st statement.

C The 1st statement is false while the 2nd statement is true.

D Both statements are false.

18. The formula of aluminium oxide Aluminium is a Group III element while

is Al3O2 oxygen is a Group VI element

19. Iodine is a liquid at room Iodine molecules are held together by van

temperature and pressure der Waals force.

20. Both diamond and graphite Both diamond and graphite have giant

conduct electricity. covalent structures.


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Section B:

Structural Question (60 marks)

1. N2O is a covalent compound, which is a gas at room condition.

(a)Draw the electron diagram of N2O, showing the outermost shell electrons only.

(4 marks)

(b) Show the structural formula of N2O. (2 marks)

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(6marks)

2. The electron diagram of ammonium chloride is as follows:

(Only electrons in the outermost shells are shown.)

(a) What are elements X, Y and Z? (3 marks)

____________________________________________________________

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(b) i) Identify the type of bond exists between the two ions. (1 mark)

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ii) Identify the type of bond exists between elements X and Y. (1 mark)

____________________________________________________________

(d) Describe a chemical test to show the presence of chloride ions in a solid sample

and state the expected observation(s). (3 marks)

____________________________________________________________________

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(8marks)

3. Elements X and Y form ionic oxides X2O and Y2O3 respectively.

(a) To which groups do X and Y belong in the Periodic Table? (2 marks)

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(b) X and Y are in the same period. Which element, X or Y, has a greater atomic

number? Explain your answer. (3 marks)

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(c) Explain how Y forms a compound with chlorine. Draw the electron diagram

(showing outermost shell only) of the formation of the compound. (6 marks)

(11 marks)

4. A part of the periodic table is shown below.

a) Across a period, the elements show a gradual change in some of their physical

properties. State ONE such property. (2 marks)

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b) For each of the following pairs of elements, suggest ONE reaction in which they

behave similarly.

i) Sodium and potassium (2 marks)

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ii) Chlorine and fluorine (2 marks)

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(c) Which metal and non-metal in the above table would react most vigorously with

each other? (1 mark)

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(d) The atomic number of krypton Kr is 36. The electronic arrangement of a krypton

atom is 2, 8, x, y. What are the values of x and y? (2 marks)

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(e) Suggest a method to store caesium in the laboratory. (1 mark)

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(f) Suggest a method to store calcium in the laboratory. (1 marks)

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(11 marks)

5. Francium and Radium are the element at the bottom of Group I and Group II

respectively. Compare and state THREE similarities and THREE differences between

francium and radium. (12 marks, each point carried out 2 marks)

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(12 marks)

6. The diagram below shows the structure of an atom of element X. The crosses,

black dots and white dots represent three different kinds of particles.

(a) Identify these particles and state their charges. (3 marks)

_____________________________________________________________________

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(b) What is the atomic number and mass number of element X? (2marks)

_____________________________________________________________________

(c) To which group does element X belong? What name is given to the elements in

this group? (2 marks)

_____________________________________________________________________

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(d) What would be the formula of the compound formed by X and carbon? (1 mark)

_____________________________________________________________________

(e) State ONE physical property and ONE chemical property of the group which

element X belonged. (4 marks)

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(12 marks)

*END OF PAPER*

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