What is to be done to determine the potential of any half cell?

Discuss the method to determine the cell potential of any cell when a standard hydrogen electrode is considered as the cathode with a suitable example.

Standard reduction potentials at $25^\circ C$ of $Li^{+}|Li$,$Ba^{2+}|Ba$,$Na^{+}|Na$,and $Mg^{2+}|Mg$ are $-3.05 \ V$,$-2.90 \ V$,$-2.71 \ V$,and $-2.37 \ V$ respectively. Which one of the following is the strongest oxidising agent?

$A$ gas $X$ at $1 \, atm$ is bubbled through a solution containing a mixture of $1 \, M \, Y^{-}$ and $1 \, M \, Z^{-}$ at $25 \, ^oC$. If the reduction potential of $Z > Y > X$,then

For the cell reaction $Mg_{(s)} + Zn^{2+}_{(aq)} (1M) \rightarrow Zn_{(s)} + Mg^{2+}_{(aq)} (1M)$,the $emf$ is $1.60 \ V$. The $E$ of the cell is ........ $V$.

The standard electrode potentials for some half-reactions are given below. Which statement is correct?
$(A) Sn^{4+} + 2e^{-} \rightarrow Sn^{2+}, E^o = +0.15 \ V$
$(B) 2Hg^{2+} + 2e^{-} \rightarrow Hg_{2}^{2+}, E^o = +0.92 \ V$
$(C) PbO_2 + 4H^{+} + 2e^{-} \rightarrow Pb^{2+} + 2H_2O, E^o = +1.45 \ V$