$2{H_2}O + 2{e^ - } \to {H_2} + 2O{H^ - }$.
આપેલ :
$F{e^{2 + }} + 2{e^ - } \to Fe;$ ${E^o}_{F{e^{2 + }}/Fe} = - 0.47\,V$
$F{e^{3 + }} + {e^ - } \to F{e^{2 + }};$ ${E^o}_{F{e^{3 + }}/F{e^{2 + }}} = + 0.77\,V$
$Fe_{(aq)}^{3 + } + {e^ - } \to Fe_{(aq)}^{2 + }$ ; ${E^o} = 0.771{\mkern 1mu} \,volts;{\mkern 1mu} $
${\mkern 1mu} {I_{2(g)}} + 2{e^ - } \to 2I_{(aq)}^ - \,;{\mkern 1mu} $ ${E^o} = 0.536{\mkern 1mu} \,volts$
કોષ પક્રિયા $2Fe^{3+}_{(aq)} + 2l^{-}_{(aq)} \rightarrow 2Fe^{2+}_{(aq)} + I_{2(g)}$ માટે $E^o_{cell} = ….$
$[Fe(CN)_6]^{4-} \rightarrow [Fe(CN)_6]^{3-} + e^{-1}\, ;$ $ E^o = -0.35\, V$
$Fe^{2+} \rightarrow Fe^{3+} + e^{-1}\ ;$ $E^o = -0.77\, V$
$Zn = Z{n^{2 + }} + 2{e^ - };\,\,{E^o} = + 0.76\,V$
$Fe = F{e^{2 + }} + 2{e^ - };\,\,{E^o} = + 0.41\,V$
નીચેના કોષ પ્રક્રિયા માટે $EMF$ ......... $\mathrm{V}$ છે
$F{e^{2 + }} + Zn\, \to \,Z{n^{2 + }} + Fe$