1.Consider the following two reactions that are at equilibrium at 500 °C.

The magnitude of the value of Kc for the second reaction is
A. 8.18 × 10^-2
B. 5.72 × 10^-1
C. 1.75 × 10¹
D. 1.22 × 10¹
Solution

2. The system below is at equilibrium.

At time t = 10 minutes, the temperature is increased. Which one of the following concentration–time graphs represents the change in concentrations?

Solution

3. Methanol, CH₃OH, is widely used as a starting material for a range of products, including paints and pharmaceuticals. A chemical reaction for the synthesis of CH₃OH is

a. Define the term ‘reversible reaction’. (1 mark)

Solution
b. The operating conditions used for producing CH3OH are 500 K and 10000 kPa in the presence of a catalyst.

i. The rate of the reaction can be increased by increasing the temperature. Explain the impact this would have on the yield. (2 marks)

Solution

ii. Using Le Châtelier’s principle, state one way in which the yield of
CH₃OH could be increased at a constant temperature. Justify your response. (2 marks)

Solution

c. A mixture of carbon monoxide, CO, hydrogen, H₂, and CH₃OH gases inside a sealed container is at equilibrium at 500 K. The equilibrium expression is

A change to the system is applied at time t1.

The concentrations at t1 are measured to be:
• [CO] = 2.00 M
• [H₂] = 1.25 M
• [CH₃OH] = 5.60 M

Determine what needs to happen for the system to return to equilibrium. Use calculations to support your response. (3 marks)

Solution

d. 5.00 mol of CO and an unknown amount of H₂ were injected into an evacuated 1.00 L sealed container at 500 K. Once equilibrium was established, the concentration of CH₃OH was determined to be 1.30 M. Calculate the amount of H₂, in moles, initially added to the container.
(4 marks)

Solution