Question

Balance the following reaction, taking place under acidic

conditions, and fill in the blanks with the necessary coefficients.

(Coefficients may be 0.)

Zn(s) + VO2+(aq)→Zn2+(aq) + V2+(aq)

Answer 1

Zn in Zn has oxidation state of 0

Zn in Zn+2 has oxidation state of +2

So, Zn in Zn is oxidised to Zn+2

V in VO2+ has oxidation state of +5

V in V+2 has oxidation state of +2

So, V in VO2+ is reduced to V+2

Reduction half cell:

VO2+ + 3e- --> V+2

Oxidation half cell:

Zn --> Zn+2 + 2e-

Balance number of electrons to be same in both half reactions

Reduction half cell:

2 VO2+ + 6e- --> 2 V+2

Oxidation half cell:

3 Zn --> 3 Zn+2 + 6e-

Lets combine both the reactions.

2 VO2+ + 3 Zn --> 2 V+2 + 3 Zn+2

Balance Oxygen by adding water

2 VO2+ + 3 Zn --> 2 V+2 + 3 Zn+2 + 4 H2O

Balance Hydrogen by adding H+

2 VO2+ + 3 Zn + 8 H+ --> 2 V+2 + 3 Zn+2 + 4 H2O

This is balanced chemical equation in acidic medium

2 VO₂⁺ + 3 Zn + 8 H⁺ --> 2 V²⁺ + 3 Zn²⁺ + 4 H₂O