Question

For an exothermic reaction at equilibrium, how will increasing the temperature affect Keq? A. Keq will increase. B. Keq will decrease. C. Keq will stay the same. D. Keq will double.

Answer 1

B. $K_{eq}$ will decrease.

Explanation

The increase in temperature disturbs the equilibrium. The Le Chatelier's Principle suggests that the system would respond in a way that minimizes the degree of the impact.

There's an increase in temperature. The system will try to reduce its temperature. It will favor the backward reaction, which is endothermic and removes heat from the system. Doing so will convert some of its products to reactants.

The $K_{eq}$ of an equilibrium is a fraction of multiple concentrations. For the reversible reaction  a A + b B ⇄ c C + d D, $K_{eq} = \frac{[C]^{c}\cdot [D]^d}{[A]^{a} \cdot [B]^{b}}$, where [A], [B], [C], and [D] are equilibrium concentrations of the four species. Converting some products back to reactants increases [A] and [B] while reducing [C] and [D]. As a result, $K_{eq}$ will decrease.