The oxidation potentials of Zn, Cu, Ag, `H_(2)` and Ni are 0.76, -0.34, 0.80, 0 and 0.25 volt respectively. Which of the following reactions will provide maximum voltage ?

Options

A. `Cu + 2 Ag^(+) (aq)rarrCu^(2+)(aq)+2 Ag`
B. `Zn+2 Ag^(+)(aq)rarrZn^(2+)(aq)+2Ag`
C. `H_(2)+Ni^(2+)(aq)rarr2H^(+)(aq)+Ni`
D. `Zn+2H^(+)(aq)rarrZn^(2+)(aq)+H_(2)`

Answer

b

Explanation

The reduction potential of Zn Cu Ag and Ni are : 0.76,+0.34 +0.80 and -0.25 respective ly the maximum e.m.f of the cell is obtained when the electrode llpotential of the anode is minimum and that of the cathode is maximum i.e Zn and Ag respecitvely
`therefore E.N.F =E_("cathode")E^(@)-E_("anode")^(@)`
=+0.80 -(-0.76)=+1.56V
thus option (b) is correct