[treadlightly]

Hey everyone,
I'm in my first semester of biochemistry. I have this problem that confuses me so much. I was wondering if someone could walk me through it instead of just giving me the answer.

The problem goes like this:
Calculate the pH of a solution made from dissolving 0.2 mols of glycine and 0.1 mol of NaOH in a liter of water. The answer is supposed to be pH = 9.6.

There is something at the bottom of the problem saying that I should consider the charge of glycine power and the titration curve before adding any acid or base.
From what I know, glycine powder has a charge of 0 (because it's a powder), and before adding any acid or base, glycine is a zwitterion, so it has a charge of 0.
Glycine has a pI at pH6; pKa1=pH @ pH=2.3 and pKa2=pH @ pH=9.7

What I started doing was making a reaction between NaOH and glycine:
H3N⁺-CH2-COO^- + OH^- --> H2N-CH2-COO- + H2O

-----
oh crap. I think I just solved my own problem. So the 0.1mol of NaOH would react with 0.1 mols of glycine to produce H2N-CH2-COO-, which has a -1 charge. Since half of all glycine has a 0 charge and the other half has a -1 charge, there is a -1/2 charge overall and the pH of the solution is equal to pKa2, which is 9.7. Can anyone confirm this?
Is there another way to do this?

EDIT: SORRY! pK2 is equal to pH at 9.7, not 6.7

[Borek]

I got 9.6 as well.

[treadlightly]

Thanks for the confirmation, Borek. If it's not too much trouble, could you tell me what you did to get the answer? I was also wondering if there is a way to get the answer without referring to a titration curve. Any help would be awesome

[Babcock_Hall]

I would think of it in terms of the Henderson-Hasselbalch equation.

[Borek]

Actually I just plugged numbers into pH calculator (built into the Buffer Maker).