The pOH of a solution is 13.28. What is the [OH]

Say that this is the concentration of OH - ions in solution. All you have to do is to get the negative log of the [OH-] to get the pOH. After getting the pOH, get the pH of the solution.

pOH = - log[OH-]

= - log (1.0 * 10^-5)

= 5.00

This is actually the pOH value, not the pH. To get the pH, just subtract the pOH from 14.

pH = 14 - pOH

= 14.00 - 5.00

= 9.00

The value 2.5 x 10^-11 M is the concentration of OH - ions in solution. To get the pH, get the pOH first.

pOH = - log[OH-]

= - log (2.5 x 10^-11)

= 10.6

Then, subtract this from 14 to get the pH. The pH is 3.40.

Note: When you determine the pOH or pH of the sample, always make sure you enter - log in the calculator so you'll get a positive result.