In: Chemistry
What is the [OH-] of a 1x10-3 M solution of NH4Cl?
NH3 , Kb value = 1.8 x 10^-5
Ka = Kw / Kb = 1.0 x 10^-14 / 1.8 x 10^-5
Ka = 5.55 x 10^-10
NH4+ -----------------------> NH3 + H+
10^-3 0 0
10^-3-x x x
Ka = x^2 / 10^-3 -x
5.55 x 10^-10 = x^2 / 10^-3 -x
x^2 + 5.55 x 10^-10 x - 5.55 x 10^-13 = 0
x = 7.44 x 10^-7
[H+] = 7.44 x 10^-7 M
[OH-] = Kw [H+]
= 1.0 x 10^-14 / 7.44 x 10^-7
= 1.34 x 10^-8 M
[OH-] = 1.34 x 10^-8 M