Question

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?

• A. $Zn+C{u}^{2+}\to Cu+Z{n}^{2+}$
• B. $Zn+2A{g}^{+}\to 2Ag+Z{n}^{2+}$
• C. $H_2+C{u}^{2+}\to 2H^{+}+Cu$
• D. $H_2+N{i}^{2+}\to 2H^{+}+Ni$
• E. $Zn\left(s\right)+2H^{+}(aq.)\rightleftharpoons Z{n}^{2+}(aq.)+H_2\left(g\right)$

Answer 1

The correct option is B $Zn+2A{g}^{+}\to 2Ag+Z{n}^{2+}$

We have,

$E^0$ for $Zn=0.76$

$E^0$ for $Cu=-0.34$

$E^0$ for $Ag=-0.80$

$E^0$ for $H_2=0$

$E^0$ for $Ni=0.25$

For, maximum voltage $E_{cell}^0$ sholud me maximum.

$E_{cell}^0$ is maximum for $Zn$ and $Ag$ cell.

$E_{cell}^0=E_{Oxidation}^0-E_{Reduction}^0=0.76-(-0.80)=1.56V$

Hence, option B is correct.