Which of the following equations represents the cell potential?

Arrange the following metals in the order in which they displace each other from the solution of their salts: $Al, Cu, Fe, Mg$ and $Zn$.

Two half-cell reactions are given below:
$Co^{3+} + e^- \rightarrow Co^{2+}, E^{\circ}_{Co^{3+}/Co^{2+}} = 1.81 \, V$
$Al^{3+} + 3e^- \rightarrow Al(s), E^{\circ}_{Al^{3+}/Al} = -1.66 \, V$
The standard $EMF$ of a cell with a feasible redox reaction will be:

The standard reduction potentials for $Cu^{2+}|Cu$ and $Cu^{2+}|Cu^{+}$ are $0.337 \, V$ and $0.153 \, V$ respectively. What is the standard electrode potential for the $Cu^{+}|Cu$ half-cell in $V$?

Explain: Reduction reaction is possible with higher $E^{\theta}$ value.

If $E_{Au^{+}/Au}^o$ is $1.69 \text{ V}$ and $E_{Au^{3+}/Au}^o$ is $1.40 \text{ V}$,then $E_{Au^{+}/Au^{3+}}^o$ will be ... $\text{V}$.