How do you calculate the pOH of a solution?

1 Answer
Jun 6, 2016

In water you use the relationship pH+pOH=14.

Explanation:

We know that at 298K, equilibrium obtains between hydronium ion and hydroxide ions in water:

Kw=1014=[HO][H3O+]. We can take log10 of both sides:

log10(Kw)=log10[HO]log10[H3O+]=log10(1014)

i.e. log10[HO]log10[H3O+]=14 by definition of the log function. And again by definition pH=log10[H3O+] etc.

Thus pH+pOH=14. There should be many problems here that use this relationship. Of course, you have to find them. Good luck.