200 ml of 0200M hypobromous acid HBrO is titrated with 0250M

20.0 ml of 0.200M hypobromous acid, HBrO, is titrated with 0.250M sodium hydroxide, NaOH. Calculate the pH of the solution at the equivalence point of the titration pH = Check

Solution

hBrO is weak acid with 8.7 pKa value

millimoles of HBrO = 20.0 x 0.200 = 4.0

4.0 millimoles of NaOH must be added to reach equivalence point

4.0 = V x 0.250

V = 16 mL

total volume = 16 + 20 = 36 mL

[salt] = 4.0 / 36 = 0.111 M

for such salts

pH = 1/2 [pKw + pKa + log C]

pH = 1/2 [14 + 8.7 + log 0.111]

pH = 10.87