NH3 is a weak base (Kb = 1.8 × 10–5) and so the salt NH4Cl acts as a weak acid. What is the pH of a solution that is 0.050 M in NH4Cl?

Answer 1

.........NH4^+ + H2O ==> H3O^+ + NH3
I......0.05...............0........0
C........-x...............x........x
E......0.05-x..............x.......x

ka(for NH4^+) = (Kw/Kb for NH3) =
(H3O^+)(NH3)/(NH4^+)
Substitute and solve for x = (H3O^+), convert to pH.

Answer 2

1254.23