A solution of 0.050 M benzoic acid, HC7H5O2 , is 3.5% ionized. at 25 oC. a) What are the [H ] and pH of this solution

[H⁺] = 0.00175 M

pH = 2.757

Explanation:

The ionization of benzoic acid is given below:

C₆H₅COOH > C₆H₅COO⁻(aq) + H⁺(aq)

1 mole of H⁺ ions are produced from the dissociation of 1 mole C₆H₅COOH.

Therefore 0.050 M benzoic acid produces 0.050 M H⁺.

However, the benzoic acid is only 3.5% ionized, therefore concentration of H+ ion, [H⁺] = 3.5/100 * 0.050 M

[H⁺] = 0.00175 M

pH = - log[H⁺]

pH = - log(0.00175)

pH = 2.757