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Calculate the Ka for the acid.?

Enough of a monoprotic acid is dissolved in water to produce a 1.20 M solution. The pH of the resulting solution is 2.56.

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  • 1 month ago
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    Equilibrium: HA(aq) <--> H+(aq) + A-(aq)

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

    From the pH, [H+] = 10^-pH 

    [H+] = 2.75X10^-3 M

    From the equilibrium, [H+] = [A-] = 2.75X10^-3 M

    [HA] = 1.20 - 0.003 = 1.20

    Ka = (2.75X10^-3)^2 / 1.20 = 6.3X10^-6

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