The forward process of this reaction is endothermic.
Work Step by Step
Analyzing the informations from the question, we can see that, with the raise of the temperature, the ion-product constant increases. The equation for the ion-product constant is: $[H^+] * [OH^-] = K_w$ Which means that, the raise of the constant means the increase of $[H^+]$ and $[OH^-]$ production. Therefore, the increase of heat benefits the forward reaction. Which means that it is a endothermic reaction.