What is the OH- concentration of a solution whose pH is 12.40?

Question

Michael G. · Accepted Answer

Trinity,

from the pH you can determine the H3O^+ concentration by using ph=-log[H3O^+]. Then you can use Kw=KaxKb to solve for OH- concentration

10^-12.40 = 10^log[h3o^+] =
4.0x10^-13 M = [h3o^+]

Now use 4.0x10^-13[OH^-] = 1.00x10^-14 =

[OH^-]= 2.5X10^-2 M

Trinity · Answer

thanks@ Michael

DrBob222 · Answer

pH + pOH = pKw = 14. You know pH, solve for pOH. Then pOH = -log(OH^-) Substitute and solve for OH. You should get a little less than 2 but that's just an estimate.

Trinity · Answer

Thanks @ DrBob222

DrBob222 · Answer

I hit the wrong key. The answer should be a little less than 3.

Snowman2 · Answer

If [H3O+] = 1.7 x 10–3 M, what is the pH of the solution?