Calculate the pH of a 2.0 × 10^-3 M solution of KClO₂. K_a for HClO₂ = 1.2 × 10^-2 A) 7.24 B) 7.03 C) 6.97 D) 7.39 E) 6.61

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Quizplus · Accepted Answer

KClO₂ is a salt derived from the weak acid HClO₂. When it dissolves in water, it partially hydrolyzes, producing HClO₂ and OH⁻, which makes the solution slightly basic. The pH can be calculated using the formula for the hydrolysis of the anion and the $K_a$ of HClO₂. Given $K_a = 1.2 \times 10^{-2}$, we can find $K_b$ using the relation $K_w = K_a \times K_b$, where $K_w = 1.0 \times 10^{-14}$ at 25°C. Thus, $K_b = \frac{K_w}{K_a} = \frac{1.0 \times 10^{-14}}{1.2 \times 10^{-2}} = 8.33 \times 10^{-13}$. Using this $K_b$ and the concentration of KClO₂, we can calculate the $OH^-$ concentration and then the $pOH$, and finally the $pH = 14 - pOH$. The calculation leads to a pH slightly above 7, with the closest match being 7.03.

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