CHEMISTRY · Single correct · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A gaseous reaction has ΔH∘=−198kJ (exothermic). Which statement best describes how its equilibrium constant K changes when the temperature is raised from 298K to 350K?
(a) The effect on K cannot be predicted without knowing the sign of ΔS∘.
(b) K increases because higher temperature favors the forward reaction for any gas–phase equilibrium.
(c) K decreases because heat acts as a product, so adding heat shifts the equilibrium toward reactants.
(d) K remains essentially constant because temperature affects the rate of reaction, not the equilibrium constant.