Which from following statement is correct regarding emf of cell for the cell reaction,

$$ \mathrm{Cd}_{(\mathrm{s})}+\mathrm{Cu}_{(\mathrm{aq})}^{+2} \longrightarrow \mathrm{Cd}_{(\mathrm{aq})}^{+2}+\mathrm{Cu}_{(\mathrm{s})} $$

if concentration of $\mathrm{Cd}^{+2}$ is 10 times greater than concentration of $\mathrm{Cu}_{(\mathrm{aq})}^{+2}$ at 298 K .

Which of the following species acts as reducing agent during working of hydrogen-oxygen fuel cell?

Standard potential $\left(\mathrm{E}^{\circ}\right)$ of $\mathrm{Zn}_{(\mathrm{aq})}^{+2}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Zn}_{(\mathrm{s})}$ is -0.76 V .

What is standard potential of reaction $2 \mathrm{Zn}_{(\mathrm{s})} \longrightarrow 2 \mathrm{Zn}_{(\mathrm{aq})}^{+2}+4 \mathrm{e}^{-}$?

Which from following formulae is used to obtain value of $\mathrm{E}_{\text {cell }}^r$ for a reaction taking place in Dry cell?