General Chemistry 2 Class

Question

The acid-dissociation constant for hypochlorous acid, HClO, is 3.0 x 10^-8. Calculate the concentration of H3O+, ClO-, and HClO at equilibrium if the initial concentration of the acid is 0.075 M.

Answer 1

HClO <==> H+. +. ClO- where H+ = H3O+

Ka = [H+][ClO-] /[HClO]

3.0x10^-8 = (x)(x) / 0.075 - x and assume x is small relative to 0.075

3.0x10^-8 = x² / 0.075

x^{2 =} 2.25x10^-9

x = 4.74x10^-5 M = [H+] = [ClO-]

[HClO] = .075 - 4.74x10^-4 = 0.07495 M