d
Sol. \(4 \mathrm{OH}^{-} \rightarrow 2 \mathrm{H}_2 \mathrm{O}+\mathrm{O}_2+4 \mathrm{e}^{-}\)

for 2 mole of \(\mathrm{H}_2 \mathrm{O}=4 \mathrm{~F}\) charge is required for 1 mole of \(\mathrm{H}_2 \mathrm{O}=\frac{4 \mathrm{~F}}{2}=2 \mathrm{~F}\) required

\(\stackrel{+7}{\mathrm{Mn}} \mathrm{O}_4^{-} \rightarrow \stackrel{+2}{\mathrm{Mn}^{2+}}\)

for \(1\) mole \(\mathrm{MnO}_4^{-} 5 \mathrm{~F}\) charge is required

\(\mathrm{Ca}^{2+} \xrightarrow{+2 \mathrm{e}^{-}} \mathrm{Ca}\)

For \(1\) mole \(\mathrm{Ca}^{2+}\) ion required \(=2 \mathrm{~F}\)

\(1.5\) mole \(\mathrm{Ca}^{2+}\) ion required \(=\frac{2}{1} \times 1.5=3 \mathrm{~F}\)

\(\stackrel{+2}{\mathrm{FeO}} \rightarrow \stackrel{+3}{\mathrm{Fe}_2} \mathrm{O}_3\)

for \(1\) mole \(\mathrm{FeO}, \)1\( \mathrm{~F}\) charge is required.