Question

Calculate the standard reduction potential for the reduction half-reaction of cu(iii) to cu(ii).

Answer 1

We will use the following half equations :

1.) Cu³⁺ + 2e⁻ —> Cu⁺ E₁= 1.28 V

2.) Cu²⁺ + e⁻ — > Cu⁺ E₂= 0.15 V

3.) Cu²⁺ + 2e⁻ —> Cu (s) E₃ = 0.34 V

4.) Cu⁺ + e⁻ —> Cu(s) E₄ = 0.52 V

DIAGRAM

Cu ³⁺............... Cu ²⁺............. Cu⁺.............. CuO
............ X...............|......0.15 V...... |........0.52.......|
|...............................1.28 V............. |

Cu³⁺ + e⁻ —> Cu²⁺ E = x

Cu²⁺ + e⁻ —> Cu⁺ E = 0.15 V

Cu³⁺ + 2e⁻ — > Cu+ E = 1.28

X + 0.15 V = 1.28 × 2

X + 0.15 V = 2.56 V

X = 2.56 - 0.15 = 2.41 V