For ${\mathrm{I}}_2+2\mathrm{e}\to 2{\mathrm{I}}^{-}$ standard reduction potential $=+0.54\text{ volt. For }2{\mathrm{Br}}^{-}⟶{\mathrm{Br}}_2+2{\mathrm{e}}^{-}$ standard
oxidation potential $=-1.09\text{ volt. For }\mathrm{Fe}⟶{\mathrm{Fe}}^{2+}$ $+2{\mathrm{e}}^{-}$ standard oxidation potential = + 0.44 volt. Which of the following reactions is
non-spontaneous?

For a reaction 

${{\mathrm{E}}^{\mathrm{o}}}_{\mathrm{cell}}={\mathrm{E}}_{\mathrm{cathode}}^{\mathrm{o}}-{\mathrm{E}}_{\mathrm{anode}}^{\mathrm{o}}$

$$\begin{gathered} \mathrm{if} {\mathrm{E}}_{\mathrm{cell}}^{\mathrm{o}}=+\mathrm{ve} \left(\mathrm{spontaneous}\right) \\ \mathrm{if} {\mathrm{E}}_{\mathrm{cell}}^{\mathrm{o}}=-\mathrm{ve} (\mathrm{non} \mathrm{spontaneous})\hspace{0.17em} \end{gathered}$$

$$\begin{gathered} \hspace{0.17em}\mathrm{For} {\mathrm{Br}}_2+\hspace{0.17em}2{\mathrm{I}}^{-}\to 2{\mathrm{Br}}^{-}+\hspace{0.17em}{\mathrm{I}}_{2 } \\ {\mathrm{E}}_{\mathrm{cell}}= \left({\mathrm{E}}_{{\mathrm{Br}}_2/{\mathrm{Br}}^{-}}\right)-\left({\mathrm{E}}_{{\mathrm{I}}_2/{\mathrm{I}}^{-}}\right)=1.36\mathrm{V} [\mathrm{spontaneous} ] \end{gathered}$$

$$\begin{gathered} \mathrm{For} \mathrm{Fe}+\hspace{0.17em}{\mathrm{Br}}_2\to {\mathrm{Fe}}^{2+}+ 2{\mathrm{Br}}^{-} \\ {\mathrm{E}}_{\mathrm{cell}}^{\mathrm{o}}=\left({\mathrm{E}}_{{\mathrm{Br}}_2/{\mathrm{Br}}^{-}}^{\mathrm{o}}\right)-\left({\mathrm{E}}_{\mathrm{Fe}/{\mathrm{Fe}}^{2+}}^{\mathrm{o}}\right)=+0.65\mathrm{V}\hspace{0.17em}\left[\mathrm{spontaneous}\right] \end{gathered}$$

$$\begin{gathered} \mathrm{For} \mathrm{Fe}+\hspace{0.17em}{\mathrm{I}}_2\to {\mathrm{Fe}}^{2+}+ 2{\mathrm{I}}^{-} \\ {\mathrm{E}}_{\mathrm{cell}}^{\mathrm{o}}=\left({\mathrm{E}}_{{\mathrm{I}}_2/{\mathrm{I}}^{-}}^{\mathrm{o}}\right)-\left({\mathrm{E}}_{\mathrm{Fe}/{\mathrm{Fe}}^{2+}}^{\mathrm{o}}\right)=+0.1\mathrm{V}\hspace{0.17em}\left[\mathrm{spontaneous}\right] \end{gathered}$$

$$\begin{gathered} \mathrm{For} {\mathrm{I}}_2+\hspace{0.17em}2{\mathrm{Br}}^{-}\to 2{\mathrm{I}}^{-}+\hspace{0.17em}{\mathrm{Br}}_2 \\ {\mathrm{E}}_{\mathrm{cell}}^{\mathrm{o}}=\left({\mathrm{E}}_{{\mathrm{I}}_2/{\mathrm{I}}^{-}}^{\mathrm{o}}\right)-\left({\mathrm{E}}_{{\mathrm{Br}}_{2/{\mathrm{Br}}^{-}}}^{\mathrm{o}}\right)=-1.36\mathrm{V} [\mathrm{non} \mathrm{spontaneous}] \end{gathered}$$