What is the pH of a room temperature solution with a concentration of OH- of 3.92 x 10-5?

Question

Remember: K_w = 10^-14, and pH + pOH = 14= pKw 

Answer 1

There are a couple of ways to solve this problem.

1). pH + pOH = 14

pOH = -log [OH^-] = -log 3.92x10^-5 = 4.41

pH = 14 - 4.41

pH = 9.59

2). K_w = [H⁺][OH^-] = 1x10^-14

1x10^-14 / 3.92x10^-5 = [H⁺]

[H⁺] = 2.55x10^-10

pH = -log [H⁺]

pH = -log 2.55x10^-10

pH = 9.59