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Finding pH of solution

  1. Nov 18, 2012 #1
    A solution is prepared by mixing 200 mL of 0.2 M CH3COOH with 100 mL of 0.1 M of NaOH solution.Calculate the pH of the solution.(Ka=1.8x10-5)

    I really don't know how to start this, so please help me.Its gonna be a similar one on my exam tomorrow.

  2. jcsd
  3. Nov 19, 2012 #2


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    Assume the strong base completely converts the acetic acid to acetate. From there look at the expression which defines Ka for this acid. That's a start.

    If you can't see it from that information, try looking over this information.
  4. Nov 20, 2012 #3


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    Hint: have you heard about buffers?
  5. Nov 24, 2012 #4
    This is a buffer question. You will need to set up two ICE tables. The first one outlines the remaining concentration of weak acid and conjugate base after the reaction with OH-. The second should use those concentrations to determine the final pH. If you have a book, there should be an example.
  6. Nov 24, 2012 #5


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    Staff: Mentor

    Actually no need even for a single ICE table, this is almost a simple plug and chug application of the Henderson-Hasselbalch equation. You just need to start calculating concentrations of the reaction products, assuming reaction went to completion.
  7. Nov 24, 2012 #6
    Correct, the Henderson-Hasselbalch equation is the preferred method. If this student does not know where to start, however, I figured writing out the concentration ratios would help in gaining some intuition.
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