Question

The pH of a solution is 4.5. What is the concentration of hydroxide ion in the solution.

Answer 1

According to the definitions:

[OH-] = 10^-pOH

pOH = 14 - pH

From here:

pOH = 14 - pH = 14 - 4.5 = 9.5

[OH-] = 10^-pOH = 10^-9.5 = 3.2 × 10^-10 M

Answer: 3.2 × 10^-10 M