11. The Ka for benzoic acid is 6.5 * 10-5. Calculate the pH of a 0.10 M benzoic acid solution.

2.6

Explanation:

Benzoic acid is a weak acid that dissociates according to the following equation.

C₆H₅COOH (aq) ⇄ C₆H₅COO⁻ (aq) + H⁺ (aq)

We can calculate the equilibrium concentration of H⁺ using the following expression.

[H⁺] = √ (Ka * Ca)

where,

Ka is the acid dissociation constant

Ca is the initial concentration of the acid

[H⁺] = √ (6.5 * 10⁻⁵ * 0.10) = 2.5 * 10⁻³

The pH is

pH = - log [H⁺] = - log 2.5 * 10⁻³ = 2.6