c
\(Cu\, \to \,C{u^{ +  + }}\, + \,2{e^ - }\)

i.e., to deposit \(1\,mole\) of \(Cu\) at cathode from \(Cu^{2+}\)  \(SO_4^{2-}\) solution \(=\,2\,\,mole\) of electrons are required

i.e., To deposit

\(6.35\,g\, = \,\frac{{6.35}}{{63.5}}\, \times 2\, = \,\frac{2}{{10}}\, = \,\frac{1}{5}\,moles\)

Thus total no. of elecrtrons required \(=\,\frac {N_A}{5}\)