[antoinetta]

Hi, I'm having trouble setting up this question.  Find the pH for a 0.30M NH₃/0.36M NH₄Cl buffer system, after the addition of 20ml of 0.050M NaOH to 80ml of the buffer solution.

So, I set up ths NH₄Cl -> NH₄ + Cl^-
NH₄⁺ + H₂O -> NH₃ + H⁺

I know the number of NaOH added is 0.001 mol ... where do I go from here?

[english]

What do you think NaOH is doing in this reaction.  It's a strong base, therefore it's reacting with your acid (ammonium).

How does this affect your concentrations of ammonium and ammonia?