Electrode potential of $Zn^{2+}/Zn$ is $-0.76\,V$ and that of $Cu^{2+}/Cu$ is $+0.34\,V$. The $EMF$ of the cell constructed between these two electrodes is ............ $V$.

Iron displaces copper from its salt solution,because

For the given reactions:
$Sn^{2+} + 2e^{-} \rightarrow Sn$
$Sn^{4+} + 4e^{-} \rightarrow Sn$
The electrode potentials are $E^{\circ}_{Sn^{2+}/Sn} = -0.140 \ V$ and $E^{\circ}_{Sn^{4+}/Sn} = 0.010 \ V$. The magnitude of standard electrode potential for $Sn^{4+}/Sn^{2+}$,i.e.,$E^{\circ}_{Sn^{4+}/Sn^{2+}}$,is $..... \times 10^{-2} \ V$. (Nearest integer)

The cell potential of a cell in operation is

From the following ${E^o}$ values of half cells,what combination of two half cells would result in a cell with the largest potential?
$I$. $A + e^- \to A^{-}$,${E^o} = +0.24 \ V$
$II$. $B^{-} + e^- \to B^{-2}$,${E^o} = +1.25 \ V$
$III$. $C^{-} + 2e^- \to C^{-3}$,${E^o} = +0.15 \ V$
$IV$. $D + 2e^- \to D^{-2}$,${E^o} = +0.68 \ V$

$A$ cell constructed by coupling a standard copper electrode and a standard magnesium electrode has an $emf$ of $2.7 \ V$. If the standard reduction potential of the copper electrode is $+0.34 \ V$,the standard reduction potential of the magnesium electrode is .............. $V$.