2023 H2 Chem P1 Q12 — Chemical equilibrium Solution

The answer is D.
\(K_p\) changes only with temperature. For an exothermic forward reaction, raising the temperature favours the endothermic backward reaction, so the equilibrium position shifts to the left, the partial pressures of the products fall relative to those of the reactants, and \(K_p\) decreases.
A: Incorrect. A catalyst increases the rates of the forward and backward reactions by the same extent, so equilibrium is reached faster but \(K_p\) is unchanged.
B: Incorrect. \(K_p\) is only affected by changes in temperature. Changing the pressure may shift the position of equilibrium, but it does not change \(K_p\) for any gas phase reaction.
C: Incorrect. Pressure does not change \(K_p\) at all, and the order of reaction is a kinetic property that has no bearing on the equilibrium constant.