When iron nails are dipped in ${\mathrm{CuSO}}_4$ solution the brown colour matter deposit on iron nail is due to

When iron nails are dipped in ${\mathrm{CuSO}}_4$ solution the brown colour matter deposit on iron nail is due to copper metal displace on the surface of iron.

${\mathrm{Fe}}_{\left(\mathrm{s}\right)}+{\mathrm{CuSO}}_{4\left(\mathrm{aq}\right)}\to \underset{\mathrm{Green} \mathrm{Colour} \mathrm{Solution}}{{\mathrm{FeSO}}_{4\left(\mathrm{aq}\right)}}+\underset{\mathrm{Brown} \mathrm{diposite}}{{\mathrm{Cu}}_{\left(\mathrm{s}\right)}}$