A buffer solution is 1.40 M in NH3 and 1.00 M in NH4Cl. If 0.100 moles of NaOH are added to 1.00 L of the buffer, what is its pH?

1 answer

...........NH4^+ + OH^- ==>NH3 + H2O
initial....1.0......0......1.4.....
add.................0.1.............
change....-0.1.....-0.1.....+0.1
equil.....0.9......0........1.5

Substitute into pH = pKa + log (base/acid) and solve for pH.