A solution contains Fe²⁺, Fe³⁺ and I^$$-$$ ions. This solution was treated with iodine at 35^oC. E^o for Fe³⁺/Fe²⁺ is + 0.77 V and E^o for I₂/2I^$$-$$ = 0.536 V.
The favourable redox reaction is

Standard electrode potential of three metals X, Y and Z are $$-$$1.2 V, + 0.5 V and $$-$$ 3.0 V respectively. The reducing power of these metals will be

Standard electrode potential for Sn⁴⁺/Sn²⁺ couple is + 0.15 V and that for the Cr³⁺/Cr couple is $$-$$ 0.74 V. These two couples in their standard state are connected to make a cell. The cell potential will be

The electrode potentials for Cu²⁺_(aq) + e^$$-$$ $$ \to $$ Cu⁺_(aq)
and Cu⁺_(aq) + e^$$-$$ $$ \to $$ Cu_(s) are + 0.15 V and + 0.50 V respectively.

The value of E^o_cu²⁺/cu will be