Question

A solution has hydrogen ion concentration 0.01 M. Calculate pOH of the same solution.

Answer 1

Given: [H⁺] = 0.01 M = 10⁻² M

By using the formula:

pH = −log₁₀[H⁺]

= −log₁₀(0.01)

= −log₁₀(10⁻²)

= 2

At standard temperature (25°C), the sum of pH and pOH is always equal to 14. This relationship is derived from the self-ionisation constant of water (K_ω = 1.0 × 10⁻¹⁴):

Substitute the calculated pH value into the equilibrium equation to find the pOH:

2 + pOH = 14

pOH = 14 − 2

= 12

∴ The pOH of a solution with a hydrogen ion concentration of 0.01 M is 12.