Question

When copper turnings are added to 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 ${\text{AgNO}}_3$
• C. is oxidised to ${\text{Cu}}^{2+}$
• D. is reduced to ${\text{Cu}}^{2+}$

Answer 1

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

The equation of the reaction 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, the copper undergoes oxidation which involves loss of two electrons to form ${\text{Cu}}^{2+}$ion, whereas silver is less reactive than copper and hence undergoes reduction which involves gain of two electrons to form $\text{Ag}$. In other words, copper displaces silver and forms a blue coloured aqueous solution of copper nitrate.