A buffer solution is made by dissolving 0.230 moles of sodium hypochlorite in 1.00 L of 0.220 M hypochlorous acid.What is the pH of the solution after 0.0100 moles of sodium hydroxide is added? (The K_a of HClO is 2.9 * 10^-8.)

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Quizplus · Accepted Answer

The pH of the solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the base (sodium hypochlorite) and [HA] is the concentration of the acid (hypochlorous acid). The pKa is the negative logarithm of the acid dissociation constant (Ka), which is given as 2.9 x 10^-8, so pKa = -log(2.9 x 10^-8) ≈ 7.54. After adding 0.0100 moles of NaOH, the concentration of sodium hypochlorite increases by 0.0100 moles (since NaOH reacts with HClO to form NaClO and water), and the concentration of hypochlorous acid decreases by 0.0100 moles. Therefore, the new concentrations are: [A-] = (0.230 + 0.0100) / 1.00 L = 0.240 M, [HA] = (0.220 - 0.0100) / 1.00 L = 0.210 M. Substituting these values into the Henderson-Hasselbalch equation gives: pH = 7.54 + log(0.240/0.210) ≈ 7.596.

A Buffer Solution Is Made by Dissolving 0