In a closed system at equilibrium, which of the following statements is true?

A. The concentration of reactants is zero.

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

C. The concentration of products and reactants remains constant.

D. The reaction has completely stopped.

Which of the following is a characteristic of a system at equilibrium?

A. The system is at its lowest energy state.

B. The system no longer reacts with its surroundings.

C. The system's macroscopic properties remain unchanged.

D. The system has reached maximum entropy.

According to Le Chatelier's principle, if the concentration of a reactant in a system at equilibrium is increased, what will happen to the position of equilibrium?

A. It will shift towards the products.

B. It will shift towards the reactants.

C. It will remain unchanged.

D. It will shift in a direction that reduces the change.

In the Haber process for the synthesis of ammonia, how does an increase in pressure affect the position of equilibrium?

A. Shifts to the right, favouring the formation of ammonia.

B. Shifts to the left, favouring the decomposition of ammonia.

C. Remains unchanged.

D. Shifts in a direction that increases the pressure.

For a given reaction at equilibrium, if Kc is much greater than 1, what can be inferred?

A. The concentration of reactants is much higher than that of products.

B. The concentration of products is much higher than that of reactants.

C. The reaction is not at equilibrium.

D. The reaction rate is very slow.

a) Explain the concept of forward and reverse reactions occurring at the same rate in a chemical system. [2]

b) What are the main characteristics of a system that is at equilibrium? [2]

a) Describe the effect of increasing the concentration of a reactant on the position of equilibrium. [2]

b) How does the addition of a catalyst affect the rate of reaching equilibrium? [2]

a) Define the term 'Kc' in the context of chemical equilibrium. [2]

b) How is the value of Kc related to the position of equilibrium in a reaction? [2]

a) Describe the industrial significance of Le Chatelier's principle with respect to the Haber process. [3]

b) In the context of the Haber process, what would be the effect on the equilibrium yield of ammonia if the pressure was increased? [2]

c) Why is a compromise temperature used in the Haber process? [2]

a) Define the term 'half-life' in the context of a first-order reaction. [2]

b) How is the half-life of a first-order reaction related to its rate constant? [2]

c) Why is the half-life of a first-order reaction independent of the initial concentration? [3]

Which of the following changes will NOT affect the value of Kc for a reaction?

A. Changing the concentration of reactants.

B. Adding a catalyst.

C. Changing the temperature.

D. Adding an inert gas.

For a reaction at equilibrium, if the temperature is increased and the value of Kc decreases, what can be inferred about the reaction?

A. It is exothermic.

B. It is endothermic.

C. It is neither exothermic nor endothermic.

D. It has a high activation energy.

In the industrial synthesis of methanol, how would a decrease in temperature affect the yield of methanol, assuming the reaction is exothermic?

A. Increase the yield.

B. Decrease the yield.

C. Have no effect on the yield.

D. Make the reaction non-spontaneous.

Which of the following is NOT an application of Le Chatelier's principle in industry?

A. Adjusting conditions to maximise product yield.

B. Reducing energy costs by operating at lower temperatures.

C. Using a catalyst to shift the position of equilibrium.

D. Controlling the rate of reaction to ensure safety.

For a reaction at equilibrium, if the volume of the container is decreased, what will happen to the position of equilibrium in a reaction with more moles of gas on the reactant side?

A. Shift to the right.

B. Shift to the left.

C. Remain unchanged.

D. Depend on the temperature.

a) What is meant by the 'position of equilibrium'? [2]

b) How does a change in temperature affect the value of the equilibrium constant, Kc? [3]

c) Explain the effect of adding an inert gas to a system at equilibrium at constant volume. [2]

a) Describe the relationship between the rate constants for the forward and reverse reactions and the equilibrium constant, Kc. [3]

b) If a reaction has an equilibrium constant much greater than 1, what does this indicate about the position of equilibrium? [2]

c) How does a catalyst affect the value of the equilibrium constant? [2]

a) Define the term 'equilibrium constant' and explain its significance in predicting the extent of a reaction. [3]

b) For the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g), if the concentration of NH3 is doubled while keeping the concentrations of N2 and H2 constant, how will the position of equilibrium shift? [2]

c) Describe the effect of a catalyst on the rate of attainment of equilibrium. [3]

d) Given that the equilibrium constant for a reaction is 0.01 at 25°C, predict the direction in which the equilibrium will shift if the temperature is increased. [2]

a) Explain the concept of 'dynamic equilibrium'. [3]

b) How does a change in pressure affect the position of equilibrium in a gaseous reaction? [3]

c) For a reaction with a positive entropy change, how would an increase in temperature affect the equilibrium position? [2]

d) Given a reaction where the forward process is endothermic, predict the effect of decreasing the temperature on the equilibrium constant, Kc. [2]

a) Describe the characteristics of a system at equilibrium. [3]

b) How does the concentration of a reactant affect the value of the equilibrium constant, Kc? [2]

c) Explain the principle behind the industrial application of Le Chatelier's principle in the production of methanol. [3]

d) If the equilibrium constant for a reaction is found to be 1000 at a certain temperature, what can be inferred about the position of equilibrium? [2]