Determine the pH of a 0.10 M solution of (CH3CH2)2NH

Answer 1

This is diethyl amine, a weak base. We need the Kb of this base. I looked it up and found it to be 8.6x10^-4

(CH₃CH₂)₂NH + H₂O ==> (CH₃CH₂)₂NH₂⁺ + OH^-

Kb = [(CH₃CH₂)₂NH₂⁺][OH^-] / [(CH₃CH₂)₂NH]

8.6x10-4 = (x)(x) / 0.10

x² = 8.6x10^-5

x = 9.3x10^-3 M = [OH^-]

pOH = -log [OH^-]

pOH = 2.03

pH = 14 - pOH

pH = 11.97 = 12