What is the H3O+ ion concentration of a solution that has an OH- ion concentration of 1.0 × 10^-3M?

A) 1.0 × 10^-3M
B) 1.0 × 10^-7M
C) 1.0 × 10^-11M
D) 1.0 × 10^-14M

C.  1.0 × 10^-11M

Explanation:

First Step: Determine the pOH of the solution by taking the -Log [-OH]

                  pOH = -Log (1.0 × 10^-3)

                           = 3

Second Step : Obtain the pH, using the following equation; pH + pOH = 14

                     pH + 3 = 14, making pH the subject of the formular we then have;

                     pH = 14 -3 = 11.

Last Step:  Take the anti-log of the pH to get the concentration of H3O+.

               ∴    Anti-log of 11 =  1.0 × 10^-11M