Question

A solution of ammonia has a pH of 11.8. What is the concentration of OH– ions in the solution?

A.) 1.00 x 10^-14 M
B.) 6.33 x 10^-3 M
C.) 1.58 x 10^-12 M
D.) 1.58 x 10^-4 M

Answer 1

We determine the concentration of OH- ions by calculating first the pOH first of the solution.

pH + pOH = 14
pOH = 14 - 11.8 = 2.2

pOH = -log (OH-) = 2.2
(OH-) = 6.33 x 10^-3 M

Therefore, the correct answer is option B.

Answer 2

pH + pOH = 14

11.8 + pOH = 14

pOH = 14 - 11.8

pOH = 2.2

[OH-] = 10 ^- pOH

[OH-] = 10 ^- 2.2

[OH-] = 6.33 x 10^-3 M

Answer B

hope this helps!