Acid base and pH

Question

Determine the hydroxide ion concentration in a solution that is 0.0028 M HNO3.

Answer 1

There are several ways to approach this problem. You should know the following relationships:

[H⁺][OH-] = 1x10^-14

pH + pOH = 14

HNO3 is a strong acid so [H+] = [HNO3] = 0.0028 M

Using the above formula [H⁺][OH-] = 1x10^-14 and solving for [OH-] we have...

2.8x10^-3 x [OH-] = 1x10^-14

[OH-] = 1x10^-14/2.8x10^-3

[OH-] = 3.6x10^-12 M