Question
The pH of an acid solution is 5.90. Calculate the Ka for the monoprotic acid. The initial acid concentration is 0.10 M.
What I have done:
pH = 5.9
a = 10^-5.9 = 1.2589 * 10^-6
Ka = [H+][A-]/[HA]
Ka = (1.2589*10^-6)^2/(.01-1.2589)
I got -1.26903013E-12, but it's not accepted as a correct answer.
What I have done:
pH = 5.9
a = 10^-5.9 = 1.2589 * 10^-6
Ka = [H+][A-]/[HA]
Ka = (1.2589*10^-6)^2/(.01-1.2589)
I got -1.26903013E-12, but it's not accepted as a correct answer.
Answers
bobpursley
Ka = (1.2589*10^-6)^2/(.1-1.2589E-6) was your error, so you can approximate this with
(1.2589*10^-6)^2/(.1 ) =
= 1.58 e-11
(1.2589*10^-6)^2/(.1 ) =
= 1.58 e-11