What is the pH of a 0.20 M solution of nitrous acid? K_a = 4.5 × 10^-4

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Quizplus · Accepted Answer

The pH of a weak acid solution can be calculated using the formula pH = -log[H⁺], where [H⁺] is the concentration of hydrogen ions. For nitrous acid (HNO₂), which is a weak acid, the concentration of H⁺ can be approximated using the formula [H⁺] = √(Kₐ × [HA]). Substituting the given values, [H⁺] = √(4.5 × 10⁻⁴ × 0.20) ≈ 0.0095 M. Therefore, pH = -log(0.0095) ≈ 2.02.

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