Question

pH of a solution is 12. The number H⁺ ions present in 1 cm³ of this solution is ____________.

Options

• 6.022 × 10⁸

• 6.022 × 10⁷

• 6.022 × 10⁻⁷

• 6.022 × 10⁻¹²

Answer 1

pH of a solution is 12. The number H⁺ ions present in 1 cm³ of this solution is 6.022 × 10⁸.

Explanation:

pH = 12

pH = −log₁₀ [H⁺]

∴ [H⁺] = 10⁻¹² M

i.e., 1000 cm³ of acidic solution will contain 10⁻¹² moles of H⁺ ions.

∴ 1 cm³ of solution will contain 10⁻¹⁵ moles of H⁺ ions.

Number of H⁺ ions in 1 cm³ solution = 10⁻¹⁵ × N_A

= 10⁻¹⁵ × 6.022 × 10²³

= 6.022 × 10⁸