How is pOH determined?

1 Answer
Jun 4, 2016

pOHpOH is detemined equivalently to pHpH, but pH+pOH=14pH+pOH=14 under standard conditions.

Explanation:

pHpH == -log_10[H_3O^+]log10[H3O+]

pOHpOH == -log_10[HO^-]log10[HO]

Now K_wKw == [H_3O^+][HO^-][H3O+][HO] == 10^(-14)" at 298K"1014 at 298K.

Thus -log_10K_w=-log_10[H_3O^+] -log_10[HO^-]log10Kw=log10[H3O+]log10[HO]

=-log_10(10^-14)=log10(1014) == +14+14

And thus pOH+pH=14pOH+pH=14 under standard conditions.

You should review the logarithmic function if you have any problem with this treatment. You should review it anyway, because I might have made a mistake.