Question

The following half-cells are availble:

(i) Ag⁺ (1.0 M) ∣ Ag (s) 0.7994 v
(ii) Zn²⁺ (1.0 M) ∣ Zn (s) -0.76 v
(iii) Cu²⁺ (1.0 M) ∣ Cu (s) 0.337 v
(iv) Co²⁺ (1.0 M) ∣ Co (s) -0.28 v

Linking any two half-cells makes a voltaic cell. Given four different half-cells, six voltaic cells are possible. These are labeled, for simplicity, Ag - Zn, Ag-Cu, Ag-Co, Zn - Cu, Zn-Co, and Cu-Co. (the first metal is the anode and the second is the cathode.)

In which of the voltaic cells does the copper become reduced?