The standard cell potential E°(cell) is +0.34 V for the redox reaction 2 In(s) + 6 H⁺(aq) → 2 In³⁺(aq) + 3 H₂(g). Determine E° for the half-reaction In³⁺(aq) + 3 e⁻ → In(s).

Answer 1

2In(s) + 6H⁺(aq) ==> 2In³⁺(aq) + 3H₂(g)

In³⁺(aq) + 3e- ==> In(s) Eº = ? = -0.34 V

2H⁺ + 2e- ==> H₂(g) Eº = 0 (this is a SHE, a Standard Hydrogen Electrode)

Since the Eºcell is positive (i.e. +0.34 V), and since the Eºcell = red.potential cathode - red. potential anode,

we have 0 - x = +0.34 and x = -0.34