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chemistry

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Lactic acid is a weak monoprotic acid. If a 0.10 M solution of it has a pH of 2.44, what is the dissociation constant (Ka) for lactic acid.

I got 1.3x10^-4? Is that right?

  • chemistry - ,

    You're in the right ball park but I might argue a little with the answer. If we call lactic acid, HL, then
    ...........HL ==> H^+ + L^-
    initial...0.10.....0.....0
    change.....-x.....x.....x
    final.....0.1-x...x.....x
    For pH 2.44 I obtained 0.00363 and substituted
    (0.00363)(0.00363)/(0.10-0.00363) = Ka
    For which I obtained 1.368E-4 which would round to 1.4E-4 to two s.f.

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