Chemistry Homework Question -- Kb of diethylamine?

Question

Hello,

I am having trouble with my AP Chemistry homework. Here's the problem:

A 0.25 M solution of diethylamine, (CH3CH2)2NH, has a pH of 12.15. What is the Kb of diethylamine?

I figured out the concentration of H+ ions (from the pH) to be 7.08 x 10^-13. I now don't know how to proceed. Can you help me please?

Answer 1

You're nearly there. First work out [OH-].

Then [OH-] = root (Kb x 0.25).