Question

When copper turnings are added to the silver nitrate solution, a blue coloured solution is formed after some time. It is because copper ____.

• A. oxidises silver from the solution.
• B. forms a blue coloured complex with $AgN{O}_3$.
• C. is oxidised to $C{u}^{2+}$.
• D. is reduced to $C{u}^{2+}$.

Answer 1

The correct option is C

is oxidised to $C{u}^{2+}$.

The equation of the reaction is: $Cu\left(s\right)+2AgN{O}_3\left(aq\right)\to Cu\left(N{O}_3{)}_2\right(aq)+2Ag\left(s\right)$
Here, the copper undergoes oxidation which involves loss of 2 electrons to form $C{u}^{2+}$, whereas silver is less reactive than copper and hence undergoes reduction which involves gain of 2 electrons to form $Ag$. In other words, copper displaces silver and forms a blue coloured aqueous solution of copper nitrate.