Give the chemical reaction when a $Cu$ rod is kept in an $AgNO_{3}$ solution.

(N/A) When a $Cu$ rod is dipped into an $AgNO_{3}$ solution,$Ag^{+}$ ions are reduced to $Ag$ metal,which gets deposited on the copper rod.
The oxidation and reduction half-reactions are:
Oxidation: $Cu_{(s)} \rightarrow Cu^{2+}_{(aq)} + 2e^{-}$
Reduction: $2Ag^{+}_{(aq)} + 2e^{-} \rightarrow 2Ag_{(s)}$
The overall cell reaction is:
$Cu_{(s)} + 2AgNO_{3(aq)} \rightarrow Cu(NO_{3})_{2(aq)} + 2Ag_{(s)}$
As the reaction proceeds,the concentration of $Cu^{2+}$ ions in the solution increases,which imparts a blue colour to the solution.