Question

The hydroxyl ion concentration in an aqueous solution of NaOH is 2 × 10⁻⁴ mol dm⁻³. Calculate PH of the solution.

Answer 1

Given:

Hydroxyl ion concentration (OH⁻) = 2 × 10⁻⁴ mol dm⁻³

pH and pOH relation: pH + pOH = 14

pOH = −log [OH⁻]

Calculate pOH:

pOH = −log (2 × 10⁻⁴)

= −[log2 + log10⁻⁴]

= −[0.3010 − 4]

= 4 − 0.3010

= 3.699

Calculate pH:

pH = 14 − pOH

= 14 − 3.699

= 10.301

The pH of the solution is 10.301.