Answer:
1. Ka = 8.16x10⁻⁵
2. pH = 2.40
Explanation:
1. The dissociation of a weak acid in water occurs as follows:
HA ⇄ H⁺ + A⁻
Ka = [H⁺] [A⁻] / [HA]
As 2% of the 0.20M solution is dissociated:
[H⁺] = [A⁻] = 0.20M * 2% = 0.004M -As H⁺ and A⁻ comes from the same reaction, their concentrations are the same
[HA] = 0.20M * 98% = 0.196M
Ka = (0.004)² / (0.196M) = 8.16x10⁻⁵
2. pH = -log [H⁺] = -log [0.004M]
pH = 2.40
