Chemistry Problem

Question

Determine the pH of a 0.25 M solution of KOBr

Answer 1

Looking at the hydrolysis of BrO^-, we have...

BrO- + H2O ==> HBrO + OH-

From the Ka for HBrO we can find the Kb for BrO-

Ka HBrO = 2x10^-9 (look it up)

Kb = 1x10^-14 / 2x10^-9 = 5x10^-6

Kb = 5x10^-6 = [HBrO][OH-] / [BrO-] = (x)(x) / 0.25-x (assume x is small relative to 0.25 and ignore it)

x² = 1.25x10^-6

x = 1.12x10^-3 M = [OH-]

pOH = -log 1.12x10^-3 M

pOH = 2.95

pH = 14 - 2.95

pH = 11.05