Question

The following skeletal oxidation-reduction reaction occurs under acidic conditions. Write the balanced REDUCTION half reaction. Pb + ClO4- Pb2+ + ClO3-

Answer 1

Pb in Pb has oxidation state of 0

Pb in Pb+2 has oxidation state of +2

So, Pb in Pb is oxidised to Pb+2

Cl in ClO4- has oxidation state of +7

Cl in ClO3- has oxidation state of +5

So, Cl in ClO4- is reduced to ClO3-

Reduction half cell:

ClO4- + 2e- --> ClO3-

Balance Oxygen by adding water

ClO4- + 2e- --> ClO3- + H2O

Balance Hydrogen by adding H+

ClO4- + 2 H+ + 2e- --> ClO3- + H2O

Add equal number of OH- on both sides as the number of H+

ClO4- + 2 H+ + 2 OH- + 2e- --> ClO3- + H2O + 2 OH-

Combine H+ and OH- to form water

ClO4- + 2 H2O + 2e- --> ClO3- + H2O + 2 OH-

Remove common H2O from both sides

Balanced Eqn is

ClO4- + H2O + 2e- --> ClO3- + 2 OH-

This is balanced chemical equation in basic medium

Answer:

ClO₄^- + H₂O + 2e^- --> ClO₃^- + 2 OH^-