Calculate the pH at the equivalence point in the titration of 50.0 mL of 0.170 M
ID: 908005 • Letter: C
Question
Calculate the pH at the equivalence point in the titration of 50.0 mL of 0.170 M HCIO(aq) with 0.170 M KOH(aq). HClO + OH^- arrow ClO^- + H2O 1. Find the concentration of C10 2. Find the Kb of Cl0 3. Find the pH just as you would for a typical weak base problem. Step 1: At the equivalence point, all the HCIO has been converted to ClO^- in a 1:1 mole ratio. How many millimoles of ClO^- are present at the equivalence point? What is the total volume of solution at the equivalence point? Using your answers above, find the concentration of ClO^-.Explanation / Answer
millimoles of HClO = 50 x 0.170
= 8.5
millimoles of KOH = 0.170 V
at equivalence point millimoles of acid = millimoles of base
8.5 = 0.170 V
V = 50 ml
total volume = 50 + 50 = 100 ml
at equivalencepoint = 100 ml volume
ClO - concentration = 8.5 / total volume
= 8.5 / 100
= 0.085 M
ClO - concentration = 0.085 M
ClO- is the salt of weak acid + strong base so
pH = 7 + 1/2 [pKa + logC]
pH = 7 + 1/2 [7.40 + log 0.085]
pH = 10.16