Question

When copper turnings are added to silver nitrate solution, a blue coloured solution is formed after some time. Which of the following option justifies the observation?

• A. $\text{Cu}$ is oxidised to ${\text{Cu}}^{2+}$.
• B. $\text{Cu}$ is reduced to ${\text{Cu}}^{2+}$
• C. Copper forms a blue coloured complex with ${\text{AgNO}}_3$
• D. Copper oxidises silver from the solution.

Answer 1

The correct option is A $\text{Cu}$ is oxidised to ${\text{Cu}}^{2+}$.

The equation of the reaction that occurs when copper is added to a silver nitrate solution is:

$\text{Cu}\text{(s)}+2{\text{AgNO}}_3\text{(aq)}\to {\text{Cu(NO}}_3{)}_2\text{(aq)}+2\text{Ag}\text{(s)}$

Here, copper undergoes oxidation which involves loss of two electrons to form ${\text{Cu}}^{2+}$ ion.
Silver is present as ${\text{Ag}}^{+}$ ion in silver nitrate solution. As silver is less reactive than copper, it undergoes reduction (gain of electron) to form $\text{Ag}$.
In other words, copper displaces silver from its solution, and forms a blue coloured aqueous solution of copper nitrate.