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Kinetics & Equilibrium Review Packet

Standard Level

1. Which quantities in the enthalpy level diagram are altered by the use of a catalyst?

II

III

IEnthalpy

Time

A. I and II only

B. I and III only

C. II and III only

D. I, II and III (Total 1 mark)

2. Which of the following is (are) important in determining whether a reaction occurs?

I. Energy of the molecules

II. Orientation of the molecules

A. I only

B. II only

C. Both I and II

D. Neither I nor II (Total 1 mark)

3. Consider the reaction between solid CaCO3 and aqueous HCl. The reaction will be speeded up by an increase in which of the following conditions?

I. Concentration of the HCl

II. Size of the CaCO3 particles

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III. Temperature

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A. I only

B. I and III only

C. II and III only

D. I, II and III (Total 1 mark)

4. Excess magnesium was added to a beaker of aqueous hydrochloric acid on a balance. A graph of the mass of the beaker and contents was plotted against time (line 1).

Mass

1

2

Time

What change in the experiment could give line 2?

I. The same mass of magnesium but in smaller pieces

II. The same volume of a more concentrated solution of hydrochloric acid

III. A lower temperature

A. I only

B. II only

C. III only

D. None of the above (Total 1 mark)

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5. Which of the following is (are) altered when a liquid at its boiling point is converted to a gas at the same temperature?

I. The size of the molecules

II. The distance between the molecules

III. The average kinetic energy of the molecules

A. I only

B. II only

C. III only

D. I and II only (Total 1 mark)

6. Based on the definition for rate of reaction, which units are used for a rate?

A. mol dm–3

B. mol time–1

C. dm time–1

D. mol dm–3 time–1

(Total 1 mark)

7. Which of the quantities in the enthalpy level diagram below is (are) affected by the use of a catalyst?

I II

III

Enthalpy

Time

5

A. I only

B. III only

C. I and II only

D. II and III only (Total 1 mark)

8. In the Haber process for the synthesis of ammonia, what effects does the catalyst have?

Rate of formation of NH3(g) Amount of NH3(g) formed A. Increases Increases B. Increases Decreases C. Increases No change D. No change Increases

(Total 1 mark)

9. Which statement is correct about the behaviour of a catalyst in a reversible reaction?

A. It decreases the enthalpy change of the forward reaction.

B. It increases the enthalpy change of the reverse reaction.

C. It decreases the activation energy of the forward reaction.

D. It increases the activation energy of the reverse reaction. (Total 1 mark)

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10. The rate of a reaction between two gases increases when the temperature is increased and a catalyst is added. Which statements are both correct for the effect of these changes on the reaction?

Increasing the temperature Adding a catalyst

A. Collision frequency increases Activation energy increases

B. Activation energy increases Activation energy does not change

C. Activation energy does not change Activation energy decreases

D. Activation energy increases Collision frequency increases (Total 1 mark)

11. What changes occur when the temperature is increased in the following reaction at equilibrium?

Br2(g) + Cl2(g) 2BrCl(g) ∆Hο = +14 kJ mol–1

Position of equilibrium Value of equilibrium constant A. Shifts towards the reactants Decreases B. Shifts towards the reactants Increases C. Shifts towards the products Decreases D. Shifts towards the products Increases

(Total 1 mark)

12. The equation for the Haber process is:

N2(g) + 3H2(g) 2NH3(g) ΔHӨ = −92.2 kJ

Which conditions will favour the production of the greatest amount of ammonia at equilibrium?

A. High temperature and high pressure

B. High temperature and low pressure

C. Low temperature and high pressure

D. Low temperature and low pressure (Total 1 mark)

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13. Sulfur dioxide and oxygen react to form sulfur trioxide according to the equilibrium.

2SO2(g) + O2(g) 2SO3(g)

How is the amount of SO2 and the value of the equilibrium constant for the reaction affected by an increase in pressure?

A. The amount of SO3 and the value of the equilibrium constant both increase.

B. The amount of SO3 and the value of the equilibrium constant both decrease.

C. The amount of SO3 increases but the value of the equilibrium constant decreases.

D. The amount of SO3 increases but the value of the equilibrium constant does not change. (Total 1 mark)

14. What is the equilibrium constant expression, Kc, for the reaction below?

N2(g) + 2O2(g) 2NO2(g)

A. Kc = [ ][ ][ ]22

2

ONNO

B. Kc = [ ][ ][ ]22

2

ON3NO2

C. Kc = [ ][ ][ ]222

22

ONNO

D. Kc = [ ]

[ ] [ ]222

22

ONNO+

(Total 1 mark)

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15. Consider the following equilibrium reaction in a closed container at 350°C

SO2(g) + Cl2(g) SO2Cl2(g) ΔHӨ = −85 kJ

Which statement is correct?

A. Decreasing the temperature will increase the amount of SO2Cl2(g).

B. Increasing the volume of the container will increase the amount of SO2Cl2(g).

C. Increasing the temperature will increase the amount of SO2Cl2(g).

D. Adding a catalyst will increase the amount of SO2Cl2(g). (Total 1 mark)

16. Consider the following equilibrium reaction in a closed container at 350°C.

SO2(g) + Cl2(g) SO2Cl2(g) ΔHӨ = −85 kJ

Which statement is correct?

A. Decreasing the temperature will increase the amount of SO2Cl2(g).

B. Increasing the volume of the container will increase the amount of SO2Cl2(g).

C. Increasing the temperature will increase the amount of SO2Cl2(g).

D. Adding a catalyst will increase the amount of SO2Cl2(g). (Total 1 mark)

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17. Iron(III) ions react with thiocyanate ions as follows.

Fe3+(aq) + CNS–(aq) Fe(CNS)2+(aq)

What are the units of the equilibrium constant, Kc, for the reaction?

A. mol dm–3

B. mol2 dm–6

C. mol–1 dm3

D. mol–2 dm6 (Total 1 mark)

18. The equation for a reversible reaction used in industry to convert methane to hydrogen is shown below.

CH4(g) + H2O(g) CO(g) + 3H2(g) ΔHӨ = +210 kJ

Which statement is always correct about this reaction when equilibrium has been reached?

A. The concentrations of methane and carbon monoxide are equal.

B. The rate of the forward reaction is greater than the rate of the reverse reaction.

C. The amount of hydrogen is three times the amount of methane.

D. The value of ΔHӨ for the reverse reaction is –210 kJ. (Total 1 mark)

19. Which statement is always true for a chemical reaction that has reached equilibrium?

A. The yield of product(s) is greater than 50%.

B. The rate of the forward reaction is greater than the rate of the reverse reaction.

C. The amounts of reactants and products do not change.

D. Both forward and reverse reactions have stopped. (Total 1 mark)

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20. A sealed container at room temperature is half full of water. The temperature of the container is increased and left for equilibrium to re-establish. Which statement is correct when the equilibrium is re-established at the higher temperature?

A. The rate of vaporization is greater than the rate of condensation.

B. The amount of water vapour is greater than the amount of liquid water.

C. The amount of water vapour is greater than it is at the lower temperature.

D. The rate of condensation is greater than the rate of vaporization. (Total 1 mark)

21. (a) An industrial gas mixture is produced by the catalytic reforming of methane using steam.

CH4(g) + H2O(g) CO(g) + 3H2(g) ΔH = +206 kJ

By circling the appropriate letter(s) below, identify the change(s) that would shift the position of equilibrium to the right.

A increasing the temperature B decreasing the temperature

C increasing the pressure D adding a catalyst

E decreasing the pressure F increasing the concentration of H2 (2)

(b) The following graph represents the change of concentration of reactant and product during a reaction.

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.00 10 20 30 40 50 60

Time / s

[reactant] or[product] /mol dm–3

Product

Reactant

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(i) Calculate the average rate of reaction over the first 15 s, stating the units.

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(ii) After 19 s the concentrations of the reactant and product do not change. State what this indicates about the reaction.

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(Total 6 marks)

22. The table below gives information about the percentage yield of ammonia obtained in the Haber process under different conditions.

Pressure/ Temperature/°C atmosphere

200 300 400 500 10 50.7 14.7 3.9 1.2 100 81.7 52.5 25.2 10.6 200 89.1 66.7 38.8 18.3 300 89.9 71.1 47.1 24.4 400 94.6 79.7 55.4 31.9 600 95.4 84.2 65.2 42.3

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(a) From the table, identify which combination of temperature and pressure gives the highest yield of ammonia.

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

(b) The equation for the main reaction in the Haber process is

N2(g) + 3H2(g) 2NH3(g) ∆H is negative

Use this information to state and explain the effect on the yield of ammonia of increasing

(i) pressure: …………………………….………………………………………..

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(ii) temperature: ………………………………………………………………….

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(c) In practice, typical conditions used in the Haber process are a temperature of 500 °C and a pressure of 200 atmospheres. Explain why these conditions are used rather than those that give the highest yield.

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(d) Write the equilibrium constant expression, Kc, for the production of ammonia.

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(Total 8 marks)

23. (a) The following equilibrium is established at 1700°C.

CO2(g) + H2(g) H2O(g) CO(g)

If only carbon dioxide gas and hydrogen gas are present initially, sketch on a graph a line representing rate against time for (i) the forward reaction and (ii) the reverse reaction until shortly after equilibrium is established. Explain the shape of each line.

(7)

(b) Kc for the equilibrium reaction is determined at two different temperatures. At 850°C, Kc = 1.1 whereas at 1700°C, Kc = 4.9.

On the basis of these Kc values explain whether the reaction is exothermic or endothermic.

(3) (Total 10 marks)

24. Consider the following equilibrium reaction.

2SO2(g) + O2(g) 2SO3(g) ∆H = –198 kJ

Using Le Chatelier’s Principle, state and explain what will happen to the position of equilibrium if

(a) the temperature increases.

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(b) the pressure increases.

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(Total 4 marks)

25. The equation for one reversible reaction involving oxides of nitrogen is shown below:

N2O4(g) 2NO2(g) ΔHӨ = +58 kJ

Experimental data for this reaction can be represented on the following graph:

0.2

0.4

0.6

0.8

1.0

0 2 4 6Time / min

reactant

product

concentration/ mol dm –3

8 10

(i) Write an expression for the equilibrium constant, Kc, for the reaction. Explain the significance of the horizontal parts of the lines on the graph. State what can be deduced about the magnitude of Kc for the reaction, giving a reason.

(4)

(ii) Use Le Chatelier’s principle to predict and explain the effect of increasing the temperature on the position of equilibrium.

(2)

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(iii) Use Le Chatelier’s principle to predict and explain the effect of increasing the pressure on the position of equilibrium.

(2)

(iv) State and explain the effects of a catalyst on the forward and reverse reactions, on the position of equilibrium and on the value of Kc.

(6) (Total 14 marks)

26. (i) Draw a graph to show the distribution of energies in a sample of gas molecules. Label the axes and label your curve T1. Using the same axes, draw a second curve to represent the distribution of energies at a higher temperature. Label this curve T2.

(3)

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(ii) State and explain, with reference to your graph, what happens to the rate of a reaction when the temperature is increased.

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(Total 5 marks)

27. The graph below shows the volume of carbon dioxide gas produced against time when excess calcium carbonate is added to x cm3 of 2.0 mol dm–3 hydrochloric acid.

Volume of CO2

Time

(i) Write a balanced equation for the reaction.

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(ii) State and explain the change in the rate of reaction with time. Outline how you would determine the rate of the reaction at a particular time.

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(iii) Sketch the above graph on an answer sheet. On the same graph, draw the curves you would expect if:

I. the same volume (x cm3) of 1.0 mol dm–3 HCl is used.

II. double the volume (2x cm3) of 1.0 mol dm–3 HCl is used.

Label the curves and explain your answer in each case.

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(Total 10 marks)

28. The reaction between ammonium chloride and sodium nitrite in aqueous solution can be represented by the following equation.

NH4Cl(aq) + NaNO2(aq) → N2(g) + 2H2O(l) + NaCl(aq)

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The graph below shows the volume of nitrogen gas produced at 30 second intervals from a mixture of ammonium chloride and sodium nitrite in aqueous solution at 20°C.

140

120

100

80

60

40

20

00 20 40 60 80 100 120 140 160 180

Time / s

Volume of N / cm23

(a) (i) State how the rate of formation of nitrogen changes with time. Explain your answer in terms of collision theory.

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(ii) Explain why the volume eventually remains constant.

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(b) (i) State how the rate of formation of nitrogen would change if the temperature were increased from 20°C to 40°C.

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(ii) State two reasons for the change described in (b)(i) and explain which of the two is more important in causing the change.

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(iii) The reaction between solid ammonium chloride and aqueous sodium nitrite can be represented by the following equation.

NH4Cl(s) + NaNO2(aq) → N2(g) + 2H2O(l) + NaCl(aq)

State and explain how the rate of formation of nitrogen would change if the same amount of ammonium chloride was used as large lumps instead of as a fine powder.

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(Total 9 marks)

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29. When excess lumps of magnesium carbonate are added to dilute hydrochloric acid the following reaction takes place.

MgCO3(s) + 2HCl(aq) → MgCl2(aq) + CO2(g) + H2O(l)

(a) Outline two ways in which the rate of this reaction could be studied. In each case sketch a graph to show how the value of the chosen variable would change with time.

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(b) State and explain three ways in which the rate of this reaction could be increased.

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(c) State and explain whether the total volume of carbon dioxide gas produced would increase, decrease or stay the same if

(i) more lumps of magnesium carbonate were used.

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(ii) the experiments were carried out at a higher temperature.

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(Total 14 marks)

30. Carbon dioxide gas in the atmosphere reacts slightly with rainwater as shown below.

CO2(g) + H2O(l) H+(aq) + HCO3–(aq)

(i) State the meaning of the sign.

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(ii) Predict the effect, if any, of the presence of a catalyst on the acidity of rainwater. Give a reason for your answer.

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(iii) Use Le Chatelier’s principle to predict the effect of the addition of a small quantity of an alkali on the acidity of rainwater. Explain what effect, if any, this would have on the equilibrium constant, Kc.

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(Total 6 marks)