How much OH- must be added to achieve desired pH?

physicsnnewbie

1. The problem statement, all variables and given/known data
Glycine which has a pKa of 9.6 can exist in protonated form (-NH3+) or as the free base (-NH2) because of the reversible equalibrium R-NH3+ <------> R-NH2 + H+.

How much 5 M KOH must be added to 1.0 L of 0.1 M glycine at pH 9 to bring the pH to exactly 10?


2. Relevant equations



3. The attempt at a solution
I have spent a couple hours trying to figure this out but don't really know where to start. A couple hints might point me in the right direction

Borek

When you add KOH to pH 9 glycine solution you are in fact neutralizing -NH₃⁺.

Use Henderon-Hasselbalch equation to calculate amount of -NH₃⁺ in solution at pH 9 and 10, then it is a simple stoichiometry.

physicsnnewbie

Thanks Borek, very helpful :).