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The Ka of a weak acid is 1.48 x 10-5. Assuming the "x is small" approximation...

The Ka of a weak acid is 1.48 x 10-5. Assuming the "x is small" approximation is valid, what is the predicted pH of a 0.05 M solution of the weak acid? Provide your response to two decimal places.

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Expert Solution

                             HA ------------> H^+ (aq) + A^- (aq)

                I           0.05                 0                  0

               C            -x                   +x                 +x

              E            0.05-x               +x                +x

                   Ka   = [H+][A-]/[HA]

                 1.48*10^-5   = x*x/(0.05-x)

                1.48*10^-5 *(0.05-x) = x^2

                   x    = 0.000853

                 [H+]   = x = 0.000853M

                PH   = -log[H+]

                       = -log0.000853

                        = 3.069 >>>answer


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