app g 8256 chemistry 30-2015 prototype exam · pdf file- 2 - draft - chemistry 30, prototype...

September 2015 Revised December 2015

Grade 12 Prototype Examination Chemistry Course Code 8256

Barcode Number Month Day

Date of Birth

Appendix G For more information, see the Table of Specifications.

- i - DRAFT - Chemistry 30, Prototype Exam September 2015 – Revised December 2015

Chemistry Time: Two and One-Half Hours

Chemistry 8256 is a closed-book examination. NO authorized textbooks, students’ notebooks, or laboratory manual may be used. You are NOT allowed to use a print, electronic, or translation dictionary. Calculators may be used. Only silent hand-held calculators designed for mathematical computations such as logarithmic, trigonometric, and graphing functions are permissible. Computers, calculators with QWERTY keyboards, calculators capable of symbolic manipulation, and electronic writing pads are not allowed. Calculators that have built-in notes (definitions or explanations in alpha notation) that cannot be cleared are not permitted. All calculators must be cleared of programs.

Do not spend too much time on any question. Read the questions carefully. The examination consists of 44 multiple-choice and 6 numeric response questions of equal value which will be machine scored. Record your answers on the Student Examination Form which is provided. Each multiple choice question has four suggested answers, one of which is better than the others. Select the best answer and record it on the Student Examination Form as shown in the example below: Student Examination Form: Multiple Choice Which subject is this examination being written in? A. Foundations of Mathematics B. Chemistry C. Pre-Calculus D. Workplace and Apprenticeship

Mathematics

1. A B C D

Numeric Response Calculation Questions and Solutions What volume of water must be added to 100 mL of 3.0 M solution to create a 1.0 M solution? (Record your answer in the numeric response section on the answer sheet.)

- ii - DRAFT - Chemistry 30, Prototype Exam September 2015 – Revised December 2015

Matching Question Match the force in column A with the description in column B.

(Record all four digits of your answer, in order, in the numeric response section on the answer sheet.) Value to be recorded: 4 2 1 3

Use an ordinary HB pencil to mark your answers on the Student Examination Form. If you change your mind about an answer, be sure to erase the first mark completely. There should be only one answer marked for each question. Be sure there are no stray pencil marks on your answer sheet. If you need space for rough work, use the space in the examination booklet beside each question. Do not fold either the Student Examination Form or the examination booklet. Check that all information at the bottom of the Student Examination Form is correct and complete. Make any necessary changes, and fill in any missing information. Be sure to complete the Month and Day of Your Birth section.

Column B 1. A weak force where electrons of one

molecule are attracted to protons of another molecule.

2. An attractive force between two polar molecules.

3. A force generated by temporary dipoles.

4. A force of attraction between molecules.

Column A intermolecular force dipole-dipole force Van der Waals force dispersion force

- iii - DRAFT - Chemistry 30, Prototype Exam September 2015 – Revised December 2015

As per the Registrar’s Handbook for School Administrators 2015-16 (http://www.education.gov.sk.ca/Registrar's-Handbook, page 39), the new science courses, Chemistry 30 (8256) and Chimie 30 (8259) are closed-book examinations. No external materials such as textbooks, student notebooks or lab manuals are allowed. The Ministry of Education has prepared data tables found in the Chemistry Data Booklet 2015: http://www.education.gov.sk.ca/prototypes Students may use the Data Booklet while taking the course, but when writing the Chemistry examination, students must use the Data Booklet supplied with the examination. No external notes are allowed into the examination room.

- 1 - DRAFT - Chemistry 30, Prototype Exam

September 2015 – Revised December 2015

GRADE 12 DEPARTMENTAL EXAMINATION

CHEMISTRY 30, PROTOTYPE EXAM

VALUE

100 (50 2)

Answer the following 50 questions on the computer sheet entitled “Student Examination Form.”

1. Which scientist developed the “uncertainty principle” which states that it is impossible to determine both the position and the speed of an electron at the same time?

A. Planck B. Einstein C. de Broglie D. Heisenberg

2. Which of the following is the correct Lewis structure for an atom of beryllium?

A.

B.

C.

D.

A Data Booklet that contains all of the required formulas and tables for this course is supplied with this examination. The booklet does not need to be returned to the ministry.



3. In which of the following groups do the species have the same number of electrons?

A. Br, Kr, Rb B. Na , Ne, F C. Li , Na , K D. 2 2 2O , S , Se

4. When potassium and chlorine react to form KCl, a valence electron is

A. transferred from K to Cl to form an ionic bond. B. transferred from Cl to K to form an ionic bond. C. shared between K and Cl to form an ionic bond. D. shared between K and Cl to form a covalent bond.

5. What is the correct Lewis structure for the compound 2Na O ?

A.

B.

C.

D.



6. Which of the following elements has three valence electrons?

A. sulfur B. lithium C. aluminum D. phosphorus

7. Which of the following molecular compounds has the lowest boiling point?

A. 3CHCl

B. HOCl C. HCl D. 2Cl

NR1 Match each force in column A with its description in column B.

(Record all four digits of your answer, in order, in the numeric response section on the answer sheet.)

Column A dispersion force dipole-dipole force Van der Waals force intermolecular force

Column B 1. A weak force where electrons of one

molecule are attracted to protons of another molecule.

2. An attractive force between two polar molecules.

3. A force generated by temporary dipoles.

4. A force of attraction between molecules.



8. Based on the bonding found in the molecule, which of the following is the softest?

A. Fe B. 2SiO C. 24 50C H D. 3CaCO

NR2. How many hydrogen atoms are found in a molecule of decane?

(Record your answer in the numeric response section on the answer sheet.)

9. Which class of organic compound contains one triple bond?

A. alkyne B. alkene C. alkane D. aromatic



10. Consider the following structure.

What is the IUPAC name of the molecule?

A. 2 – methyl – 4 – ethylhexane B. 3 – ethyl – 5 – methylhexane C. 5 – methyl – 3 – ethylhexane D. 4 – ethyl – 2 – methylhexane

11. Consider the following organic compound.

3 2 2 3CH CH CH CH CH CH

Which structural formula does NOT represent a completely different isomer?

A. B. 3 2 2 3CCH CH CH H CH CH

C. 3 2 2 3CH CH CH CH CH CH

D. 2 2 2 2 3CH CH CH CH CH CH

C

H

H

H C

H

H

C

H

C HH

C HH

H

C

H

H

C

H

C HH

H

C

H

H

H



12. Consider the following molecule:

To which class of organic compounds does this molecule belong?

A. ester B. ether C. ketone D. organic acid

13. Which of the following statements is true of a system at equilibrium?

A. value of Keq at 20˚C = value of Keq at 150˚C B. rate of forward reaction = rate of reverse reaction C. concentration of reactants = concentration of products D. products escaping the system = reactants entering the system

C

H

H

H C

O

O

CH

HC

H

HC

H

HH



14. Hydrogen and fluorine form an equilibrium as indicated.

2 2(g) (gH F ) 2 HF(g)

Decreasing pressure by one-half on an equilibrium mixture of 2H , 2F , and HF will

A. halve the numerical value of K .eq B. double the numerical value of K .eq C. quadruple the numerical value of K .eq D. not change the numerical value of K .eq

15. Consider the following reaction at equilibrium.

2 4 2N O (g) 2 NO (g) H 58.9 kJ/mol

Which of the following changes would increase the equilibrium concentration of 2NO (g) ?

A. increase the temperature of the system B. decrease the concentration of 2 4N O (g)

C. decrease the volume of the container D. add a catalyst



16. A concentration versus time graph of a reaction is shown.

The reaction is initially at equilibrium and has a stress applied at

1t and 2t . The equation for the reaction is

A. XZY B. YXZ C. YXZ D. not possible to determine from the information given.

17. Consider the following reaction.

2FeO(s) CO(g) Fe(s) CO (g)

The equilibrium constant expression is

A. 2[CO ]Keq

[CO]

B. 2

[CO]Keq

[CO ]

C. 2[Fe][CO ]Keq

[FeO][CO]

D. 2

[FeO][CO]Keq

[Fe][CO ]



18. Consider the following reaction at equilibrium.

23 2 2 4 24NH (g) 7O (g) 2N O (g) K 2.16 10eq6H O(g)

The equilibrium concentrations are as follows:

3[NH ] 2.40 mol/L

2[O ] 1.50 mol/L

2[H O] 1.80 mol/L

What is the equilibrium concentration of 2 4N O ?

A. 0.043 mol/L B. 0.60 mol/L C. 9.6 mol/L D. 27.7 mol/L

NR3 At 1100 K, a mixture of 3.0 M hydrogen 2(H (g)), 6.0 M iodine 2(I (g)), and 6.0 M hydrogen iodide (HI(g)) are brought to equilibrium as shown:

2 2H (g) I (g) 2HI(g).

The equilibrium concentration of hydrogen is found to be 1.0 M.

2H 2I HI

[initial] 3.0 M 6.0 M 6.0 M

[change]

[equilibrium] 1.0 M

Determine the value of Keq for the reaction to the nearest whole

number.




19. Sulfuric acid is one of the world’s most important industrial chemicals. It is used for petroleum refining and in the production of paper, fertilizer, and steel. Sulfuric acid is generated by dissolving sulfur trioxide 3(SO (g)) in water. Sulfur trioxide is produced according to the following equilibrium

2 2 32 SO (g) O (g) 2 SO (g) heat

Which of the following stresses on the system will maximize the yield of

3SO (g) ?

A. remove 2O (g) B. adding a catalyst C. increase pressure D. increase temperature

20. Consider the following equilibrium:

AgCl Ag (aq) Cl( aq)s ()

Which of the following conditions is NOT required for this reaction to exist in equilibrium?

A. AgCl(s) is present B. saturated solution C. pressure is constant D. temperature is constant

21. The addition of which one of the following compounds would cause potassium bromide to precipitate from a saturated solution of KBr(aq)?

A. 2BaI

B. NaCl C. KOH D. 4 3NH NO



NR4 The graph below shows the solubility curve for three compounds.

What is the solubility of potassium nitrate 3(KNO ) in g/L at 60˚C?


22. A saturated solution of silver dichromate 2 2 7(Ag Cr O ) at 40 ˚C has a

solubility of 59.2 10 M. The following equilibrium was established.

22 2 7 2 7Ag Cr O 2 Ag (a(s) q) Cr O (aq)

What is the value of the solubility product constant, K ?sp

A. 81.7 10 B. 83.4 10 C. 123.1 10 D. 137.8 10



23. The following equilibrium was established for a saturated solution of lead(II) carbonate 3(PbCO (s)) at 25˚C.

2 2

3 3(s) (aPbCO Pb q ( )CO) aq

If the Ksp value for 3PbCO (s) is 147.4 10 , what is its solubility?

A. 63.7 10 mol/L

B. 72.7 10 mol/L

C. 143.7 10 mol/L

D. 147.4 10 mol/L

24. Solutions of lead(II) nitrate 3 2)(Pb(NO (s)) and potassium iodide (KI) are mixed producing the following reaction

3 2 2 3Pb(NO ) (s) 2 KI(aq) PbI 2 K(? NO) (aq)

After mixing, the 2Pb concentration is 0.050 mol/L and the I concentration is 0.001 0 mol/L The Ksp of 2PbI is 99.8 10 .

What does the value of the trial Ksp indicate?

A. It has a smaller value than the actual Ksp so a precipitate forms. B. It has a larger value than the actual Ksp so a precipitate will form. C. It has a larger value than the actual Ksp so a precipitate does not

form. D. It has a smaller value than the actual Ksp so a precipitate does not

form.



25. Which substance below is considered a base according to the Brønsted-Lowry theory but not the Arrhenius theory?

A. 4CH

B. 3NH

C. NaOH D. 2Ca(OH)

26. Which of the following is a conjugate acid-base pair in the reaction

3 2 4NH (g) H O( ) NH (aq) OH (aq) ?

A. H O2 and OH

B. H O2 and NH 3

C. H O2 and NH 4

D. OH and NH 4

27. Acids and bases can be described using the terms strong, weak, dilute and concentrated. Which statement below is a correct use of the terms?

A. A strong acid cannot be dilute. B. A weak acid cannot be concentrated. C. The strength of acids varies during changes in concentration. D. The strength of acids remains constant during changes in

concentration.



28. Citric acid, symbolized )aq(CtH3 , is a triprotic acid that fulfills a variety of roles. It is used as a food preservative as well as a flavouring agent for foods, beverages, and confections. It is also used to condition water, remove sulfur dioxide from smelter waste, and polish metals such as stainless steel.

Citric acid dissociates through a series of steps:

3 2 3 2H Ct(aq) H O( ) H O (aq) H Ct (aq) 2

2 2 3H Ct (aq) H O( ) H O (aq) HCt (aq) 2 3

2 3HCt (aq) H O( ) H O (aq) Ct (aq)

The Ka values for the three steps in the dissociation, in random order, are

I 47.0 10 II 66.5 10 III 51.8 10

The Ka values for 3H Ct(aq), 2H Ct (aq), and 2HCt (aq), respectively, are

A. II, I, III B. II, III, I C. I, II, III D. I, III, II

29. What is the ]OH[ 3 in a 0.020 mol/L solution of )aq()OH(Ca 2 ?

A. 121.0 10 mol/L B. 135.0 10 mol/L C. 132.5 10 mol/L D. 141.0 10 mol/L



30. What is the [H ] in a 0.50 mol/L solution of nitrous acid, 2HNO , which

has a Ka value of 45.1 10 ?

A. 21.6 10 mol/L B. 31.2 10 mol/L C. 45.1 10 mol/L D. 42.6 10 mol/L

31. Litmus works as an acid-base indicator with the following equilibrium

H litmus H litmus

red blue

Referring to the pH ranges of common indicators table, what colour change would occur when adding 3.0 M NaOH(aq) to a neutral solution containing litmus?

A. A blue solution turns red. B. A purple solution turns red. C. A purple solution turns blue. D. A blue solution turns purple.

32. An unknown solution is tested with three indicators. The solution is blue when bromocresol green is added, orange with chlorophenol red, and yellow when thymol blue is added.

name of indicator colour at acidic

end of range pH range for

colour change colour at basic end of range

bromocresol green yellow 3.8 to 5.4 blue chlorophenol red yellow 5.2 to 6.8 red thymol blue yellow 8.0 to 9.6 blue

According to this information, what is the most likely pH of the solution?

A. 3.0 B. 6.0 C. 7.0 D. 8.0



NR5 What volume (in mL) of antacid, 0.015 M 2Mg(OH) (aq), is required to neutralize 25 mL of stomach acid, 0.020 MHCl(aq) ? Round your answer to the nearest whole number.


33. An acidic solution was titrated with NaOH(aq) and the data plotted on the graph shown.

Using the pH Ranges of Common Indicators table supplied with this examination, the BEST choice of indicator for this titration is

A. orange IV. B. alizarin yellow. C. chlorophenol red. D. phenolphthalein.



34. Which type of reaction is never a redox reaction?

A. synthesis B. combustion C. neutralization D. single replacement

35. A piece of zinc metal heated in the presence of chlorine gas produces )s(ZnCl2 . Which one of the following statements about this

oxidation-reduction process is TRUE?

A. Chlorine is the reducing agent. B. Zinc metal loses electrons and is oxidized. C. Zinc metal gains electrons and is reduced. D. Chlorine gas loses electrons and is oxidized.

36. Which change shows a gain of electrons?

A. 2Ca (aq) to Ca(s)

B. 2 Cl (aq) to 2Cl (g)

C. 2Fe (aq) to 3Fe (aq)

D. NaCl(s) to Na (aq) and Cl (aq)



NR6. Balance the following oxidation-reduction equation.

24 2 2 3MnO NO (g) H O Mn NO H

When the coefficient of

4MnO is 1, what are the coefficients of 2

3Mn , NO , and H ?


37. In an experiment, strips of Au, Bi, Ga, and In were placed in 1.0 M solutions of 3Au (aq), 3Bi (aq), 3Ga (aq), and 3In (aq). The following results were observed.

3 3Au Bi Bi Au

3In Bi no reaction 3 3Bi Ga Ga Bi 3 3In Ga Ga In

Using these observations, what is the arrangement of the ions

3Au , 3 In , 3Bi , and 3Ga in decreasing order of their attraction for electrons?

A. 3 3 3 3Ga , Bi , In , Au B. 3 3 3 3Ga , In , Bi , Au C. 3 3 3 3Au , Bi , In , Ga D. 3 3 3 3Au , In , Bi , Ga



Use the following information to answer questions 38, 39, and 40.

The following diagram represents an electrochemical cell of 2 2Mn(s) Mn (aq) Ni (aq) Ni(s).

38. The substances labelled 2 and 3 could be

A. Ni(s) and 3NiCO (aq)

B. Mn(s) and 3MnCO (aq)

C. Ni(s) and 3 2Ni(NO ) (aq)

D. Mn(s) and 3 2Mn(NO ) (aq)

39. The table indicates the flow of ions and electrons.

Which row in the table is correct?

Direction of Flow of Ions Direction of Flow of Electrons A. 2Ni flows toward Ni(s) toward Mn(s)

B. 2Ni flows away from Ni(s) toward Mn(s)

C. 2Mn flows away from Mn(s) toward Ni(s)

D. 2Mn flows toward Mn(s) toward Ni(s)



40. The voltage generated by the cell is

A. 2.12 V B. 0.93 V C. 1.58 V D. 3.07 V

______________________________

41. A student made a chart to compare the similarities and differences between electrochemical and electrolytic cells.

Which line of the chart contains an error?

electrochemical cells electrolytic cells A. electron flow from anode to

cathode electron flow from anode to cathode

B. anode – oxidation cathode – reduction

anode – oxidation cathode – reduction

C. anode is negative cathode is positive

anode is negative cathode is positive

D. spontaneous – produces energy

non-spontaneous – requires energy

42. Which of the following would NOT protect an iron boat against rusting?

A. painting the boat’s hull B. greasing the boat’s hull C. sanding the iron surface smooth D. sending a small electric charge through the iron



43. A sacrificial anode is often connected to the tank of a water heater to prevent corrosion. If the sacrificial anode prevents the oxidation of iron,

2Fe(s) Fe 2 e , what could the anode be made of?

A. silver B. nickel C. copper D. magnesium

44. Hydrogen fuel cells produce electricity by reacting hydrogen 2(H ) and oxygen 2(O ) gases. A diagram of this process is shown below:

What is the net overall reaction for a hydrogen fuel cell?

A. 2 2 22 H (g) O (g) 2 H O(g)

B. 2 2 2H (g) O (g) 2 H (aq) 2 e 2 H O(g)

C. 2 2 2H (g) O (g) 4 H (aq) 4 e 2 H (aq) 2 e 2 H O(g)

D. 2 2 22 H (g) O (g) 4 H (aq) 4 e 4 H (aq) 4 e 2 H O(g)

A B C D

A B C D

A B C D

A B C D

A B C D

A B C D

A B C D

A B C D

Month and Dayof Your Birth

JANDAY

FEBMARAPRMAYJUNJUL

AUGSEPOCTNOVDEC

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MULTIPLE CHOICE

A B C D

A B C D

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SE-0915-1

Student Examination Form

A B C D A B C D A B C D

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A B C D A B C D A B C D8 20 32 56

A B C D

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A B C D

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NR 2 0 0 0 0

1 1 1 1

2 2 2 2

3 3 3 3

4 4 4 4

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NR 3 0 0 0 0

1 1 1 1

2 2 2 2

3 3 3 3

4 4 4 4

5 5 5 5

6 6 6 6

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NR 4 0 0 0 0

1 1 1 1

2 2 2 2

3 3 3 3

4 4 4 4

5 5 5 5

6 6 6 6

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NR 5 0 0 0 0

1 1 1 1

2 2 2 2

3 3 3 3

4 4 4 4

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1 1 1 1

2 2 2 2

3 3 3 3

4 4 4 4

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1 1 1

2 2 2

3 3 3 3

4 4

5 5 5 5

6 6 6 6

7 7 7 7

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9 9 9 9

A B C D

A B C D

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Chemisty Prototype Exam2015 Curriculum

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- i - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

GRADE 12 DEPARTMENTAL EXAMINATION CHEMISTRY 30

PROTOTYPE EXAM — Answer Key 1. D. The uncertainty principle was first developed in 1927 by Werner Heisenberg. 2. A. Beryllium is in group 2 on the periodic table so it has 2 valence electrons. Its

electron dot diagram will have 2 dots but not as a pair.

3. B. Na loses one electron and F- gains one electron. All three species have

8 valence electrons. 4. A. K is a metal that transfers an electron to Cl, a non-metal. A transfer of

electrons creates an ionic bond. 5. B.

6. C. Group 3 elements have three valence electrons – Aluminum

- ii - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

7. D. The weaker the intermolecular forces, the lower the boiling point. 2Cl has a

non-polar bond and London dispersion forces which are very weak. All of the other molecules have a polar bond which is a stronger bond.

NR1 3214 dispersion force – a force generated by temporary dipoles dipole-dipole force – an attractive force between two polar molecules Van der Waals – a weak force where electrons of one molecule are attracted

to protons of another molecule intermolecular force – a force of attraction between molecules 8. C. 24 50C H – organic alkane compound which is a waxy crystal which is quite soft. Fe – iron, a hard metal 2SiO – sand, glass 3CaCO – rocks and shells of marine organisms NR2 22 An alkane so there will be 2 n + 2 hydrogens. 2(10) + 2 = 22 9. A. Alkyne – one triple bond Alkene – one double bond Alkane – single bonds Aromatic – three triple bonds in a benzene ring 10. D. - number from the end with the smallest number for an alkyl group - place alkyl groups in alphabetical order - name parent chain based on longest continuous chain of carbons - in this

case there are 8 so hexane 4 – ethyl – 2 – methylhexane

- iii - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

11. B. All four compounds have the same formula so all of them could be isomers.

Structure B is identical to the original—it has been drawn as a mirror image. 12. A. Ester is an organic molecule with the functional group:

13. B. The forward and reverse rates of reaction must be equal. Keq changes with temperature so cannot be equal at 20 °C and 150 °C. 14. D. Decreasing pressure has no effect on the value of Keq as there are the same

number of moles of gas on both sides of the equation. 15. A. Needs to be a shift to the products. Only an increase in temperature will

work because the reaction is endothermic (positive ∆H).

R C

O

O

R

- iv - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

622 4 2

4 73 2

4 72 3 2

2 4 62

2 4 7

2 4 6

[N O ] [H O]Keq

[NH ] [O ]

K [NH ] [O ]eq[N O ][H O]

(2.16 10 )(2.40) (1.50)[N O ]

1.80

0.60 mol/L

16. A. Y Z X As the substances change concentration after a stress, Y and Z both decrease

showing that they must be on the same side of the equation. X does the opposite so must be on the other side of the equation.

17. A.

2[CO ]Keq

[CO]

Solids are not used in Keq expressions and products are always on top. 18. B. NR3 25

2H 2I HI

[initial] 3.0 M 6.0 M 6.0 M

[change] – 2.0 M – 2.0 M + 4.0 M

[equilibrium] 1.0 M 4.0 M 10.0 M

2

2 2

2

[HI]Keq

[H ][I ]

10(1.0)(4.0)25

- v - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

19. C. Create a stress that will force the equilibrium to the right— an increase in

pressure forces it to SO3 as there are fewer moles of gas on that side of the equilibrium.

20. C. Liquids and solids are not compressible. A constant pressure is not needed. 21. C. Add KOH. The common ion effect occurs when you add a compound which

contains an ion that is in a saturated solution. In this case both contain K. NR4 1120 Read the value from the graph. 22. C.

2 22 74 2 5

12

K [Ag ] [Cr O ]spK (1.84 10 ) (9.2 10 )spK 3.1 10sp

23. B.

2 23

14

7

K [Pb ][CO ]sp

7.4 10 (x)(x)x 2.7 10

24. B. The trial 8K (0.050)(0.0010) 5.0 10sp The trial Ksp is larger than the actual Ksp so a precipitate will form.

- vi - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

25. B. NH3 – Brønsted-Lowry theory defines a base as a proton (H+) acceptor while

the Arrhenius theory requires the substance to contain and dissociate OH . 26. A. 2H O and OH – An acid loses one H and creates a conjugate base. 27. D. Strength and concentration of acids are independent of each other. Strength

will remain constant while concentration is changed. 28. D. The largest Ka value represents the strongest acid. In a dissociation series,

the strongest acid is the original compound and as hydrogens are removed, the strength of the acids decrease.

43

52

2 6

H Ct(aq) 7.0 10

H Ct (aq) 1.8 10

HCt (aq) 6.5 10

29. C. Two OH in the base so OH 0.020 2[ ] 0.040 mol/L

14

14

13

[H ][OH ] 1.0 10 mol/L

1.0 10[H ]

0.040[H ] 2.5 10 mol/L

- vii - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

30. A.

2 2

2

22

4

2

HNO H NO[H ][NO ]

Ka[HNO ]

x5.1 10

0.50x 1.6 10 mol/L

31. C. A neutral solution would be a purple color. Adding NaOH removes H ions

from the solution shifting the equilibrium to the products, a blue color. 32. B. The only indicator with a color within the range is chlorophenol red. The

orange color indicates the pH is around the midpoint between 5.2 and 6.8 which is 6.0.

NR5 17 There are 2 OH in the base so the formula is MaVa 2 MbVb. (0.020 M)(25 mL) 2 (0.015 M)Vb Vb = 17 mL 33. D. The endpoint of the titration is the midway point of the vertical section of the

graph at around 9.0. The only indicator that has this value in its range is phenolphthalein 8.2–10.0.

34. C. Neutralization is a special example of a double replacement reaction which

changes ions between two different compounds.

- viii - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

35. B. A substance that is oxidized will lose electrons. In this reaction, Zn(s) loses

electrons to become 2Zn . 36. A. Gaining electrons will create a lower charge in the resulting ion/element. 2Ca (aq) gains 2 electrons to create Ca(s). NR6 152

37. C. Decreasing order means start with the strongest ion. Reaction 1 shows that 3Au is stronger than 3Bi Reaction 2 shows that 3Bi is stronger than 3In Reaction 3 shows that 3Bi is stronger than 3Ga Reaction 4 shows that 3In is stronger than 3Ga 38. D. Electrons are leaving the electrode to enter the voltmeter so this is the anode.

Mn is listed lower in the Standard Electrode Potentials table so it is oxidized in this cell.

A possible electrolyte in the cell must be soluble. 3MnCO is not but

3 2Mn(NO ) is soluble.

- ix - DRAFT - Chemistry 30, Prototype Exam - Answer Key September 2015 – Revised December 2015

39. C. Mn is the anode so 2Mn ions flow away from it as they are created. Ni is

the cathode in this cell so it will attract 2Ni ions and electrons will travel to it in the external circuit.

40. B. Using the Standard Electrode Potentials table in the data booklet,

2

2

2 2

Mn(s) Mn (aq) 2 e 1.18 VNi (aq) 2 e Ni(s) 0.25 VMn(s) Ni (aq) Mn (aq) Ni(s) 0.93 V

41. C. Electrolytic cells have the opposite charge on the electrodes. Anode is

positive, cathode is negative. 42. C. Sanding an iron surface will promote rusting as it exposes more iron to the

atmosphere. 43. D. Mg is lower than iron in the Standard Electrode Potentials table so it will

corrode before iron. 44. A. 2 2 22 H (g) O (g) H O(g)

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