A 0.10 M weak acid HA with Ka = 1×10⁻⁵ has pH ≈

3.0 [H⁺] ≈ √(Ka·C) = √(10⁻⁵·0.10) = 10⁻³ → pH = 3.

Weak Acid and Base Equilibria

AP Chemistry· difficulty 4/5

A 0.10 M weak acid HA with K_a = 1\times10⁻⁵ has pH \approx

Explanation

[H⁺] \approx \sqrt(K_a\cdotC) = \sqrt(10⁻⁵\cdot0.10) = 10⁻³ \to pH = 3.

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