Question

Equal volumes of three acid solutions of pH 1, 2 and 3 are mixed in a vessel. What will be the H⁺ ion concentration in the mixture?

Options

• 3.7 × 10⁻²

• 10⁻⁶

• 0.111

• none of these

Answer 1

3.7 × 10⁻²

Explanation:

pH = −log₁₀ [H⁺]

∴ [H⁺] = 10^−pH

Let the volume be x mL

V₁M₁ + V₂M₂ + V₃M₃ = VM

∴ x mL of 10⁻¹ M + x mL of 10⁻² M + x mL of 10⁻³ M = 3x mL of [H⁺]

∴ [H⁺] = `("x"[0.1 + 0.01 + 0.001])/(3"x")`

= `(0.1 + 0.01 + 0.001)/3`

= `0.111/3`

= 0.037

= 3.7 × 10⁻²