Reactivity 2.3—How far? The extent of chemical change: Practice Questions

Consider the following equilibrium:
\( 2A(g) + B(g) \rightleftharpoons 2C(g) \)
What is the correct expression for the equilibrium constant, \( K_c \)?

The production of methanol is an exothermic process:
\( CO(g) + 2H_2(g) \rightleftharpoons CH_3OH(g) \)
Which set of conditions would yield the maximum amount of methanol at equilibrium?

The following data shows the variation of the equilibrium constant \( K_p \) with temperature for a reaction:
At \( 300 \text{ K}, K_p = 4.5 \times 10^5 \)
At \( 500 \text{ K}, K_p = 1.2 \times 10^2 \)
What can be concluded about the enthalpy change (\( ΔH \)) and entropy change (\( ΔS \)) for the forward reaction?

A reaction at equilibrium has an equilibrium constant, \(K_c = 4.5 \times 10^{-6}\). What does this magnitude indicate about the relative amounts of reactants and products at equilibrium?

Which of the following will change the value of the equilibrium constant, \( K_c \), for a gas-phase reaction?

Consider the reversible reaction for the synthesis of ammonia:

$$N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \quad \Delta H = -92 \text{ kJ mol}^{-1}$$

a) At a certain temperature and pressure, the system is at equilibrium. Predict the effect of each of the following changes on the position of equilibrium (shift left, shift right, or no change) and the amount of ammonia ($$NH_3$$) present:

b) At a different temperature, an equilibrium mixture in a $$2.00 \text{ L}$$ vessel contains $$0.10 \text{ mol}$$ of $$N_2$$, $$0.30 \text{ mol}$$ of $$H_2$$, and $$0.20 \text{ mol}$$ of $$NH_3$$. Calculate the equilibrium constant, $$K_c$$, for this reaction at this temperature.