Question

What are the concentrations of hydroxide and hydronium ions in a solution with a pH of 4.6? 1.3 × 10–4 M H3O+ and 7.7 × 10–11 M OH– 2.5 × 10–5 M H3O+ and 4.0 × 10–10 M OH– 7.9 × 10–6 M H3O+ and 1.3 × 10–9 M OH– 8.7 × 10–7 M H3O+ and 1.1 × 10–8 M OH–

Answer 1

Answer:

2.5 × 10⁻⁵ M H₃O⁺ and 4.0 × 10⁻¹⁰ M OH⁻.

Explanation:

∵ pH = - log[H₃O⁺]

∴ 4.6 = - log[H₃O⁺].

∴ log[H₃O⁺] = - 4.6.

∴ [H₃O⁺] = 2.51 x 10⁻⁵.

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

[H₃O⁺] = 2.51  x 10⁻⁵ M.

∴ [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(2.51  x 10⁻⁵ M) = 3.98 × 10⁻¹⁰ M ≅ 4.0 × 10⁻¹⁰ M.

So, the right choice is: 2.5 × 10⁻⁵ M H₃O⁺ and 4.0 × 10⁻¹⁰ M OH⁻.