What is the "pH" for 2.5 xx 10^(-6) "M" "HCl"?

1 Answer
Jun 2, 2016

pH=5.60

Explanation:

HCl is a strong acid that fully ionizes when dissolved in water according to the following equation:

HCl + H_2O -> H_3O^+ + Cl^-

Having 1:1 ratio => [H_3O^+] = 2.5xx10^-6\ M

pH = -log [H_3O^+]
pH = -log(2.5xx10^-6)
pH = 5.60

Note that the contribution of the autoionization of H_2O to [H_3O^+] is small (in the range of 10^-7 M) that is why it is neglected. If it was not, it may contribute about one-tenth or so to the "pH".