You have a solution containing 1 mol each of two unknown amino acids in a mixture at pH6.5 (pKa=6.0). What would be the pH if you added 0.2 mol of NaOH?

I've used the Henderson-Hasselbalch to get this:

6.5 = 6.0 + log [B/A]
10^.5 = [B/A]
3.16/1 = [B/A]

What do I do next?

1 answer

A+B=2 moles

Based upon your calculations, 2*0.316=0.632 moles of A

2-0.632=1.37 moles of B

pH=pka+log[moles of B/moles of A]=6.0+log[moles of B/moles of A]

****Check my thinking. Not sure about the problem since you have to take into account the isolectric points of the amino acids