The acid-dissociation constant at 25.0 °C for hypochlorous acid (HClO)is 3.0 × .At equilibrium,the molarity of In a 0.010 mol L^-1 aqueous solution of HClO is: A)1.7 × B)0.010 C)5.8 × D)4.76 E)2.00

Question

Quizplus · Accepted Answer

The equilibrium expression for the dissociation of HClO is:
K_a = [H^+][ClO^-]/[HClO]
At equilibrium, let x be the concentration of H^+ and ClO^- ions produced and 0.010- x be the concentration of HClO. Thus,
K_a = x^2 / (0.010 - x)
Rearranging, we get:
x = sqrt(K_a*(0.010-x))
Since K_a is very small, we can assume that (0.010- x) ≈ 0.010. Thus,
x = sqrt(K_a*0.010)≈1.65 x 10^-4 M
Since HClO dissociates into equal quantities of H^+ and ClO^-, the final concentration of ClO^- ions is also 1.65 x 10^-4 M. Therefore, the correct answer is A, 1.7 x 10^-4 M.

The Acid-Dissociation Constant at 25