On the basis of standard electrode potential values, suggest which of the following reactions would take place?

As we know that,

(a)
$\mathrm{Cu}+{\mathrm{Zn}}^{2+}\to {\mathrm{Cu}}^{2+}+\mathrm{Zn}$
In the given cell reaction, Cu is oxidised to Cu2+, therefore, Cu2+/Cu couple acts as anode and Zn2+ is reduced to Zn, therefore, Zn2+/Zn couple acts as cathode.
$\mathrm{E}{°}_{\mathrm{cell}}=\mathrm{E}{°}_{\mathrm{cathode}}-\mathrm{E}{°}_{\mathrm{anode}}$
Positive value of $\mathrm{E}{°}_{\mathrm{cell}}$ indicates that the reaction will not occur.
(a) $\mathrm{Mg}+{\mathrm{Fe}}^{2+}\to {\mathrm{Mg}}^{2+}+\mathrm{Fe}$
In the given cell reaction, Mg is oxidised to Mg2+ hence, Mg2+/Mg couple acts as anode and Fe2+ is reduced to Fe hence, Fe2+/Fe couple acts as cathode.
$\mathrm{E}{°}_{\mathrm{cell}}=\mathrm{E}{°}_{\mathrm{cathode}}-\mathrm{E}{°}_{\mathrm{anode}}$
Positive value of $\mathrm{E}{°}_{\mathrm{cell}}$ 5 indicates that the reaction will occur.
(c) ${\mathrm{Br}}_{2}+2{\mathrm{Cl}}^{-}\to {\mathrm{Cl}}_{2}+2{\mathrm{Br}}^{-}$
In the given cell reaction, Cl- is oxidised to Cl2 hence, Cl-/Cl2 couple acts as anode and Br2 is reduced to Br- hence; Br-/Br2 couple acts as cathode.
$\mathrm{E}{°}_{\mathrm{cell}}=\mathrm{E}{°}_{\mathrm{cathode}}-\mathrm{E}{°}_{\mathrm{anode}}$
Negative value of $\mathrm{E}{°}_{\mathrm{cell}}$ indicates that the reaction will occur.
(d) $\mathrm{Fe}+{\mathrm{Cd}}^{2+}\to \mathrm{Cd}+{\mathrm{Fe}}^{2+}$
In the given cell reaction, Fe is oxidised to Fe2+ hence, Fe2+/Fe couple acts as anode and Cd2+ is reduced to Cd hence, Cd2+/Cd couple acts as cathode.
$\mathrm{E}{°}_{\mathrm{cell}}=\mathrm{E}{°}_{\mathrm{cathode}}-\mathrm{E}{°}_{\mathrm{anode}}$
Positive value $\mathrm{E}{°}_{\mathrm{cell}}$ indicates that the reaction will occur.