How can it be both? That' double talk. I would look at it this way. Let's try to reason through it.
......H2O + H2O ==> H3O^+ + OH^-
and heat goes on the left or right to complete the equation.
(H3O^+)(OH^-) = Kw.
So, increasing T makes Kw larger,that means there are more (H3O^+) and more (OH^-) so the ionization equation must have shifted to the right when heat was added. So we complete the equation by adding the heat this way.
...H2O + H2O + heat ==> H3O^+ + OH^-
Now you know the reaction is what?
The value of Kw increases with increasing temperature. Is the autoionization of water endothermic or exothermic?
In thinking its both but I don't know how to explain it.hmm...
2 answers
Oh, okay so increasing the kw makes the reaction produce more OH- and H+ so energy must be increasing on the reacting side to produce a endothermic reaction meaning energy is being absorbed to obtain a high temperature for the kw. Ahh...I get it! Thank you!