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The pH of a solution that contains 0.818 M acetic acid (Ka = 1.76 x 10-5) and 0.172 M sodium acetate is
__________. The Ka of acetic acid is 1.76 × 10-5.

  • chemistry -

    You are missing units for your Ka.

    I am sure that I have answered this one recently. Anyway start from the equation

    HAc <-> H+ + Ac-

    Ka = [H+][Ac-]/[HAc]

    at the start we have 0.181 M HAc
    and 0.172 M NaAc

    at equilibrium we have

    (0.181-x)M HAc (some has dissociated)
    (0.172+x)M Ac- (we now have more Ac- due to the dissociation)

    x M H+

    so we can write Ka
    (0.172-x)(x)/(0.181-x)= 1.76 × 10-5

    you can either solve the quadratic or we can say that x is small wrt 0.172 and 0.181, hence

    (0.172)(x)/(0.181)= 1.76 × 10-5

    find x

    hence find the pH=-log(x)

  • chemistry -

    sorry, answer found. no longer need help..

  • chemistry -

    I hope the method above agrees with the answer you have found.

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