Target: 10 Questions in 10 minutes

An IB Chemistry data booklet is helpful

Questions 1-2 are about the reverse water gas shift reaction, a process for converting carbon dioxide, CO2, into more useful products.
The reaction equation is..

CO2(g) + H2(g) ⇌ CO(g) + H2O(g)             ∆H0 = +42 kJ mol-1

The equilibrium constant for this reaction has a value of 0.11 at 673K.

 reference: sciencedirect.com
1. In a container of 10 dm3, 5 mol of CO2 and 10 mol of H2 were initially put together with 2 mol of CO and 2 mol of H2O. What is the value of the reaction quotient Q initially?
  • A.   1.00
  • B.   0.27
  • C.   0.11
  • D.   0.08

2. As the reaction proceeds, what happens to the value of Q and the position of equilibrium?

  Q The position of equilibrium
A Increases Shifts to the right
B Decreases Shifts to the left
C Increases Shifts to the left
D Decreases Shifts to the right

3. Which of the following statements is true for a reversible reaction at equilibrium?

I. The standard Gibbs energy change, ∆G0, is equal to 0
II. The Gibbs energy of the reaction mixture is at its minimum
III. There are equal amounts of reactants and products
  • A.   I only
  • B.   II only
  • C.   I and II only
  • D.   I, II and III
4. For the condensation reaction to make the ester ethyl ethanoate ...

CH3COOH(l) + CH3CH2OH(l) ⇌ CH3COOCH2CH3(l) + H2O(l)

..a mixture of 0.280 mol of ethanoic acid and 0.400 mol of ethanol was set up and allowed to reach equilibrium under reflux. At equilibrium there was 0.060 mol of ethanoic acid remaining in the reaction mixture. What is the value of the equilibrium constant, Kc, for this reaction mixture?
  • A.   0.18
  • B.   0.43
  • C.   4.48
  • D.   More information is needed on the volume of the reaction mixture

Questions 5-6 are about the Haber process, N2(g) + 3H2(g) ⇌ 2NH3(g).

At temperature T, an equilibrium mixture contains 1.88 mol dm-3 of N2(g), 5.63 mol dm-3 of H2(g) and 6.24 mol dm-3 of NH3(g).

 
5. What is the value of the equilibrium constant, Kc, for this reaction mixture?
  • A.  0.116
  • B.  0.393
  • C.  0.589
  • D.  0.876
6. If the reaction vessel suddenly halves in size for the above reaction mixture, what happens to the reaction quotient Q at this instant and how does the position of equilibrium shift?
 
  Q The position of equilibrium
A Increases Shifts to the right
B Decreases Shifts to the left
C Increases Shifts to the left
D Decreases Shifts to the right
7. When aqueous iodine solution is mixed with hexane, some of the iodine will dissolve into the hexane layer and establish an equilibrium I2(aq) ⇌ I2(C6H14). The amount of iodine dissolved in each layer of the solvents can be determined by titrating with sodium thiosulphate, I2 + 2S2O32-  →  2I- + S4O62- .

In an experiment, the initial concentration of 10 cm3 of an aqueous iodine solution was 0.005 mol dm-3. 10 cm3 of hexane was added. At equilibrium, 15 cm3 of 0.005 mol dm-3 Na2S2O3 was required to react with all the iodine dissolved in 10 cm3 of hexane layer.

What is the value of Kc for this process I2(aq) ⇌ I2(C6H14) ?

  • A.  0.75
  • B.  1.00
  • C.  1.50
  • D.  3.00
8. In a reversible reaction, M(aq) + 4L (aq) ⇌ N(aq), the equilibrium constant at temperature T is 7.00x10-5. Given that the equilibrium concentration of L is 3.00 mol dm-3 and that of N is 0.00172 mol dm-3, what is the equilibrium concentration of M at this temperature?
  • A.   0.0180
  • B.   0.303
  • C.   8.19
  • D.   1990

Questions 9 and 10 are about the steam reforming reaction to make hydrogen gas:

CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g)        ∆H0 = +210 kJ mol-1

9. What effect does increasing temperature have on the value of the equilibrium constant Kc and the value of the standard Gibbs energy change ∆G0?		  
  Kc ∆G0
A Increases Becomes more positive
B Decreases Becomes more negative
C Decreases Becomes more positive
D Increases Becomes more negative

10. What effect does increasing pressure have on the value of the forward reaction rate constant k and the spontaneity of the reaction?

  
  k Spontaneity of the reaction
A Increases Becomes more spontaneous
B Decreases Does not change
C Does not change Does not change
D Decreases Becomes less spontaneous