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Homework Help: Biochem Ph Problem

  1. Sep 26, 2008 #1
    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.
  2. jcsd
  3. Sep 27, 2008 #2


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    Staff: Mentor

  4. Sep 27, 2008 #3
    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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