The acid-dissociation constant at 25.0°C for hypochlorous acid (HClO)is 3.0 × 10^-8.At equilibrium,the molarity of H₃O⁺ in a 0.044 M solution of HClO is A) 3.6 × 10^-5 B) 0.044 C) 2.8 × 10^-10 D) 4.44 E) 1.36

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Quizplus · Accepted Answer

The acid-dissociation constant expression for hypochlorous acid is: Ka = [H+][ClO-]/[HClO] At equilibrium, let the concentration of H+ be x. Then, the concentration of ClO- will also be x, and the concentration of HClO will be (0.044 - x) since some of the HClO has dissociated. Using the given Ka value: 3.0 × 10^-8 = x^2/(0.044 - x) This is a quadratic equation with a very small Ka value, which means that x will be much smaller than 0.044 (which is the initial concentration of HClO). Therefore, we can assume that x is negligible compared to 0.044, and we can approximate the denominator as 0.044: 3.0 × 10^-8 = x^2/(0.044) Solving for x: x = 3.6 × 10^-5 M Therefore, the concentration of H₃O⁺ at equilibrium is also 3.6 × 10^-5 M. Answer choice A corresponds to this value, so it is the correct answer.

The Acid-Dissociation Constant at 25