If the ka of a monoprotic weak acid is 1.2 * 10-6, what is the ph of a 0.23 m solution of this acid?

Question

Isiah Mcdowell

Chemistry

10 May, 00:06

If the ka of a monoprotic weak acid is 1.2 * 10-6, what is the ph of a 0.23 m solution of this acid?

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Tara Hardin · Answer 1

Answer is: pH of monoprotic weak acid is 3.28.

Chemical reaction: HA (aq) ⇄ A⁻ (aq) + H⁺ (aq).

c (monoprotic acid) = 0.23 M.

Ka = 1.2 ·10⁻⁶.

[A⁻] = [H⁺ ] = x.

[HA] = 0.23 M - x.

Ka = [A⁻]·[H⁺] / [HA].

1.2·10⁻⁶ = x² / (0.23 M - x).

Solve quadratic equation: [H⁺] = 0.000524 M.

pH = - log[H⁺].

pH = - log (0.000524 M).

pH = 3.28.