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

  • #1

Homework Statement


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?


Homework Equations





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
 

Answers and Replies

  • #2
Borek
Mentor
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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.
 
  • #3
Thanks Borek, very helpful :).
 

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