How do I find the pH of this?
1) What is the pH of a 10uM (micromolar) aqueous solution of HIO, a weak acid with a Ka of 2.3 x 10^-11?
and show me how to do it don't just give me an answer please
1) What is the pH of a 10uM (micromolar) aqueous solution of HIO, a weak acid with a Ka of 2.3 x 10^-11?
and show me how to do it don't just give me an answer please
steve_geo1
Favorite Answer
10uM = 10 x 10^-6M = 1 x 10^-5M
Ka = [H+][IO-]/[HIO] = 2.3 x 10^-11
Let [H+] = x. Then [IO-] = x and [HIO] = (1x10^-5)-x. But x is very small, so [HIO] is essentially 1x10^-5
x2/(1x10^-5) = 2.3x10^-11
x^2 = 2.3 x10^-16. So x = 1.52 x 10^-8 = [H+]
From that [H+], the pH would be 7.8, which is impossible. So the pH = 7.0, because the [H+] from ionization of H2O swamps that from ionization of such a minute amount of HIO.