Question

An Account For The Following ${\mathrm{Cu}}^{+}$ Is Unstable In An Aqueous Solution.

Answer 1

Copper:

• The atomic number of $\mathrm{Cu}$ is $29$.
• The electronic configuration of copper is $$[Ar]3d^{10}4s^1$$.
• The electronic configuration of $\mathrm{C}{\mathrm{u}}^{+}$ will be $$[Ar]3d^{10}$$ as one electron is removed.

${\mathrm{Cu}}^{+}$ is unstable in an aqueous solution:

• Though the $\mathrm{C}{\mathrm{u}}^{+}$ion has a fully filled d orbital still it is not stable in an aqueous solution.
• In the aqueous solution, the $\mathrm{C}{\mathrm{u}}^{2+}$ion is more stable than $\mathrm{C}{\mathrm{u}}^{+}$ion because although the energy is needed to remove one electron from the $\mathrm{C}{\mathrm{u}}^{+}$to form $\mathrm{C}{\mathrm{u}}^{2+}$ion but the high hydration energy of the $\mathrm{C}{\mathrm{u}}^{2+}$compensates for it.
• So, the$\mathrm{C}{\mathrm{u}}^{+}$ion is unstable in an aqueous medium and undergoes the disproportionation reaction, and gives $\mathrm{C}{\mathrm{u}}^{2+}$and $\mathrm{Cu}$ as the product.
• It gets oxidized to give cuprous ion and reduced to give copper metal.
• The chemical reaction can be depicted as:
• $2{\mathrm{Cu}}^{+}\left(\mathrm{aq}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)$