For the half-cell $Zn^{2+} | Zn$,the standard electrode potential $E^{\circ}$ is $-0.76 \ V$. What is the $e.m.f.$ of the cell $Zn_{(s)} | Zn^{2+}_{(aq)} (1 \ M) || 2H^{+}_{(aq)} (1 \ M) | H_{2(g)} (1 \ atm)$ in $V$?

The reaction $Zn^{2+} + 2e^{-} \to Zn$ has a standard electrode potential of $-0.76 \ V$. This means:

Standard oxidation potentials $(SOP)$ of four metals $P, Q, R$ and $S$ are $+2.87 \ V, +3.05 \ V, -0.80 \ V$ and $+0.25 \ V$ respectively. The reducing power of these metals is:

Given:
$Co^{3+} + e^- \longrightarrow Co^{2+}; E^o = 1.81 \ V$
$Pb^{4+} + 2e^- \longrightarrow Pb^{2+}; E^o = + 1.67 \ V$
$Ce^{4+} + e^- \longrightarrow Ce^{3+}; E^o = + 1.61 \ V$
$Bi^{3+} + 3e^- \longrightarrow Bi; E^o = + 0.20 \ V$
Oxidizing power of the species will increase in the order:

Among the following metals,the strongest reducing agent is

For the decomposition of $Al_2O_3$ at $500^{\circ}C$,the free energy change is $\frac{2}{3} Al_2O_3 \to \frac{4}{3} Al + O_2$,$\Delta G = +966 \ kJ \ mol^{-1}$. The potential difference required for the electrolytic reduction of $Al_2O_3$ at $500^{\circ}C$ is ........... $V$.