The table below shows the temperature dependance of Kw.

T (º C) Kw


0.29 x 10-14


0.45 x 10-14


0.68 x 10-14


1.01 x 10-14


1.47 x 10-14


5.48 x 10-14

Is the autoionization of water endothermic or exothermic?

endothermic exothermic

Good! Since Kw increases with increasing temperature, the reaction is endothermic. Because Kw 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.

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