I don't understand how the pH value ("Neutral pH", right) is calculated in this table:

http://www.chembuddy.com/?left=pH-calculation&right=water-ion-productI see that the pH is half the pK

_{w}... but why?

Example: The K

_{w} at 100 C is 51.3 *10^(-14), so [H+] = sqrt(51.3 *10^(-14)) = 7.16*10^(-7). The pH value is therefore -log(7.16*10^(-7)) = 6.14 as it says in the table. No problems so far.

But now I want to calculate the pOH value. Since pH + pOH = 14, pOH = 14 - 6,14 = 7.86. But I also know that [H+] = [OH-] = 7.16*10^(-7), so pOH = -log(7.16*10^(-7)) = 6.14?! That can't be right.

What am I missing here?