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Biochem Ph Problem

by vcuram
Tags: biochem
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Sep26-08, 09:44 PM
P: 2
1. The problem statement, all variables and given/known data

Solid Na2HPO4 is dissolved in water. What is the resulting pH of the solution? Relative pka's of phosphate derivaties are ~2, ~7, and ~12.

2. Relevant equations

No equation needed, just look at the species which phosphate would develop.

3. The attempt at a solution

I believe the specified compound would be in equilibrium between one of these species;
H3PO4, H2PO4 (-), HPO4 (-2) and PO4 (-3). The choices are 12, 7, 2, 9, or there is not enough information.
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Sep27-08, 03:37 AM
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P: 23,393
pH of amphiprotic salt solution
Sep27-08, 09:46 AM
P: 2
Thank you very much! If I understand correctly then the answer would be 1/2 (7 +12) which would be ~ 9 ph?

That is the answer I chose. Thank you.

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