Question

0.01 M KMnO4 solution was added to 20.0 mL of 0.05 M Mohr's salt solution through a burette. The initial reading of 50 mL burette is zero. The volume of KMnO4 solution left in burette after the end point is _____ml. [nearest integer]

Answer 1

The correct answer is 30
Meq of oxidising agent = Meq of reducing agent
$(M×V×n_F)KMnO_4=(M×V×n_F)_{Mohr’s salt}$
0.01 × 20 × 5 = 0.05 × V × 1
Volume required = 20 ml
Since initial volume of KMnO4 in burette is 50 ml. Hence volume of KMnO4 left in the burette after end point is 30 ml.