I am given the following information:

Lactic acid................0.025M...................pH 2.74

How do I calculate the pKa? I don't know how to do it without the concentration. Help please!

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  1. dissociation: lactic acid>>>H+ + act-

    ka= x*x/(.025-x)
    but you know x=10^-2.74=.001819
    ka= .001819^2/(.025-.001819)=.001819^2/0.023181= 0.000142735904=10^-3.85

    pKa= 3.85
    check my math

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  2. Thank you so much!!!

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