$W\,=\,\frac {E\times i\times t}{96500}$
Where $E\,=$ equivqlent weight
$=\,\frac {mol.\,mass\,of\,metal\,(M)}{oxidation\,state\,of\,metal(x)}$
Substituting the value in the formula
$W\,=\,\frac {M}{x}$ $\times $ $\frac {i\times t}{96500}$
or $x=\frac {M}{W}$ $\times $ $\frac {i\times t}{96500}$ $ = \,\frac{{10\, \times \,2 \times 60 \times 60\,}}{{96500\, \times 0.250}} = 3$
[Given :no . of moles $=\frac {M}{W}\,=\,0.250$ ]
Hence oxidation state of metals is $(+3)$
$(i)\, A3^-\rightarrow A^{2-} + e; E° = 1.5 \,V$
$(ii) \,B^{+}+ e \rightarrow B; E° = 0.5 \,V$
$(iii)\, C^{2+} + e \rightarrow C^{+}; E°= 0.5\, V$
$(iv)\, D \rightarrow D^{2+}+ 2e; E° = -1.15\, V$
$Zn\,(s)\,\, + \,\,C{u^{2 + }}\,(aq)\, \rightleftharpoons \,Z{n^{2 + \,}}\,(aq)\, + Cu\,(s)$
$(R = 8 \,JK^{-1}\,mol^{-1},\, F = 96000\,C\,mol^{-1})$
$(1$ ફેરાડે $= 96500\, C,$ પરમાણ્વીય દળ of $Co = 59)$