IBDP Official Exam Material
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Topic 7: Equilibrium
For both SL and HL students
1. [1 mark]
The exothermic reaction I2 (g) + 3Cl2 (g) ⇌ 2ICl3 (g) is at equilibrium in a fixed volume. What is correct about the reaction quotient, Q, and shift in position of equilibrium the instant temperature is raised?
A. Q > K, equilibrium shifts right towards products.
B. Q > K, equilibrium shifts left towards reactants.
C. Q < K, equilibrium shifts right towards products.
D. Q < K, equilibrium shifts left towards reactants.
2. [1 mark]
12Cl2 (g) + 12I2 (g) ⇌ ICl (g) Kc = 454
What is the Kc value for the reaction below?
2 ICl (g) ⇌ Cl2 (g) + I2 (g)
A. 2×454
B. 12×454
C. 4542
D. 14542
3. [1 mark]
Which species are acids in the equilibrium below?
CH3NH2 + H2O ⇌ CH3NH3+ + OH–
A. CH3NH2 and H2O
B. H2O and CH3NH3+
C. H2O and OH–
D. CH3NH2 and CH3NH3+
4. [1 mark]
The equilibrium constant, Kc, for the reaction 2A + 4B ⇌ 2C + 4D has a value of 4.0. What is the value of Kc for the reaction below at the same temperature?
C + 2D ⇌ A + 2B
A. 0.25
B. 0.50
C. 1.0
D. 16
5. [1 mark]
Ammonia is produced by the Haber–Bosch process which involves the equilibrium:
N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g)
Deduce the expression for the equilibrium constant, Kc, for this equation.
6. [2 marks]
Explain why an increase in pressure shifts the position of equilibrium towards the products and how this affects the value of the equilibrium constant, Kc.
7. [1 mark]
State how the use of a catalyst affects the position of the equilibrium.
8. [1 mark]
What effect does a catalyst have on the position of equilibrium and the value of the equilibrium constant, Kc, for an exothermic reaction?
9. [3 marks]
Consider the first stage of the reaction.
CH4 (g) + H2O (g) ⇌ CO (g) + 3H2 (g)
Determine the enthalpy change, ΔH, in kJ. Use section 11 of the data booklet.
Bond enthalpy of CO = 1077 kJ mol−1.
10. [1 mark]
State the expression for Kc for this stage of the reaction.
11. [1 mark]
State and explain the effect of increasing temperature on the value of Kc.
12. [3 marks]
Consider the following equilibrium reaction:
2SO2 (g) + O2 (g) ⇌ 2SO3 (g)
State and explain how the equilibrium would be affected by increasing the volume of the reaction container at a constant temperature.
13. [1 mark]
What is correct when temperature increases in this reaction at equilibrium?
2NOCl g⇌2NO g+Cl2 g H=+75.5 kJ
14. [1 mark]
What is the equilibrium constant expression for the following equation?
2NO2 (g) + F2 (g) ⇌ 2NO2F (g)
A. 2[NO2F]2[NO2]+[F2]
B. 2[NO2F]2[NO2][F2]
C. [NO2]2[F2][NO2F]2
D. [NO2F]2[NO2]2[F2]
15. [1 mark]
Consider the reaction:
2N2O (g) ⇌ 2N2 (g) + O2 (g)
The values of Kc at different temperatures are:
Which statement is correct at higher temperature?
A. The forward reaction is favoured.
B. The reverse reaction is favoured.
C. The rate of the reverse reaction is greater than the rate of the forward reaction.
D. The concentration of both reactants and products increase.
16. [1 mark]
The equilibrium constant for N2(g) + 3H2(g) ⇌ 2NH3(g) is K.
What is the equilibrium constant for this equation?
2N2(g) + 6H2(g) ⇌ 4NH3(g)
A. K
B. 2K
C. K2
D. 2K2
17. [1 mark]
Which factor does not affect the position of equilibrium in this reaction?
2NO2(g) ⇌ N2O4(g) ΔH = −58 kJ mol−1
A. Change in volume of the container
B. Change in temperature
C. Addition of a catalyst
D. Change in pressure
18. [1 mark]
This reaction is used in the manufacture of sulfuric acid.
2SO2 (g) + O2 (g) ⇌ 2SO3 (g) Kc = 280 at 1000 K
State why this equilibrium reaction is considered homogeneous.
19. [3 marks]
0.200 mol sulfur dioxide, 0.300 mol oxygen and 0.500 mol sulfur trioxide were mixed in a 1.00 dm3 flask at 1000 K.
Predict the direction of the reaction showing your working.
20. [1 mark]
What will happen if the pressure is increased in the following reaction mixture at equilibrium?
CO2 (g) + H2O (l) ⇌ H+ (aq) + HCO3− (aq)
A. The equilibrium will shift to the right and pH will decrease.
B. The equilibrium will shift to the right and pH will increase.
C. The equilibrium will shift to the left and pH will increase.
D. The equilibrium will shift to the left and pH will decrease.
21. [1 mark]
Consider the equilibrium between N2O4(g) and NO2(g).
N2O4(g) ⇌ 2NO2(g) ΔH = +58 kJ mol−1
Which changes shift the position of equilibrium to the right?
I.Increasing the temperatureII.Decreasing the pressureIII.Adding a catalyst
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
22. [1 mark]
What is the equilibrium constant expression, Kc, for the following reaction?
2NH3(g) + 2O2(g) ⇌ N2O(g) + 3H2O(g)
A. 3H2ON2O2NH32O2
B. NH32O22N2OH2O3
C. 2NH32O23H2ON2O
D. N2OH2O3NH32O22
If you need the markscheme, including the examiners' reports for each question, and more exam and teaching materials on this topic, contact me through the contact page