Good! Since K_w increases with increasing temperature, the reaction is endothermic. Because K_w is larger at higher temperatures, the autoionization of water is more product favored at higher tempertures. Thus more H₃O⁺ from to the autoionization of water is present at higher temperatures.

K_w increases with increasing temperature. This means that as heat is added, the concentration of the products increase (since K_w is equal to the product of H⁺ and OH^-). Does this occur in endothermic or exothermic systems?