Summarizing pH and pOH

Key Concepts and Summary

The concentration of hydronium ion in a solution of an acid in water is greater than 1.0 \(×\) 10⁻⁷M at 25 °C. The concentration of hydroxide ion in a solution of a base in water is greater than 1.0 \(×\) 10⁻⁷M at 25 °C. The concentration of \({\text{H}}_{3}{\text{O}}^{\text{+}}\) in a solution can be expressed as the pH of the solution; pH = −log\({\text{H}}_{3}{\text{O}}^{\text{+}}.\) The concentration of OH⁻ can be expressed as the pOH of the solution: pOH = −log[OH⁻]. In pure water, pH = 7.00 and pOH = 7.00

Key Equations

• \(\text{pH}=\text{−log}\left[{\text{H}}_{3}{\text{O}}^{\text{+}}\right]\)
• pOH = −log[OH⁻]
• [H₃O⁺] = 10^−pH
• [OH⁻] = 10^−pOH
• pH + pOH = pK_w = 14.00 at 25 °C

Glossary

acidic

describes a solution in which [H₃O⁺] > [OH⁻]

basic

describes a solution in which [H₃O⁺] < [OH⁻]

neutral

describes a solution in which [H₃O⁺] = [OH⁻]

pH

logarithmic measure of the concentration of hydronium ions in a solution

pOH

logarithmic measure of the concentration of hydroxide ions in a solution