Question

In NaOH solution [OH^–] is 2.87 × 10^–4. Calculate the pH of the solution.

Answer 1

Given: [OH^–] = ${\displaystyle 2.87\times {10}^{-4}}$ M

To find: pH of the solution

Formulae: 

i. pOH = –log₁₀[OH^–]

ii. pH + pOH = 14

Calculation:

From formula (i),

pOH = –log₁₀[OH^–]

∴ pOH = –log₁₀[2.87 × 10^–4]

= –log₁₀2.87 – log₁₀10^–4

∴ –log₁₀2.87 + 4 = 4 – 0.4579

pOH = 3.5421

From formula (ii),

pH + pOH = 14

pH = 14 – pOH

= 14 – 3.5421

= 10.4579

pH of the solution is 10.4579