A detergent solution has a pH of 11.63 at 25°C. What is the hydroxide-ion [OH-] concentration?

Answer 1

pH + pOH = pKw = 14. Solve for pOH, then pOH = -log(OH^-).

Solve for OH^-

OR you can use
pH = -log(H^+) and solve for )H^+), then
(H^+)(OH^-) = Kw = 1E-14
and solve for OH^-

Answer 2

Is this the correct way to set it up & solve for the problem?

[OH-] = 10^-11.63
[OH-] = 2.34E-12

I wasn't sure if it was the same set up as it is for the hydronium ion.

Answer 3

No. The pH is 11.63, your set up calculates (H^+). I would do
14-11.63 = 2.37 = pOH, then
(OH^-) = 10^-2.37 = 4.27E-3.

Answer 4

Okay, thanks so much for your help!! :)