Enough of a monoprotic acid is dissolved in water to produce a 1.23 M solution. The pH of the resulting solution is 2.65 . Calculate the Ka for the acid.

Answer 1

HA ==> H⁺ + A^-

Ka = [H⁺][A-] /[HA]

pH = -log [H⁺]

[H⁺] = 1x10^-2.65

[H⁺] = 2.24x10^-3 M = [A^-]

Ka = (2.24x10^-3)(2.24x10^-3) / 1.23

Ka = 4.08x10^-6