JEE Main 2022 — D And F Block Elements Question with Solution

(A) $\mathrm{Cu}$ (II) complexes are always paramagnetic as they have one unpaired electron due to $d^9$ configuration of $\mathrm{Cu}(\mathrm{II})$

(B) $\mathrm{Cu}(\mathrm{I})$ complexes are generally colourless due to $d^{10}$ configuration.

(C) $\mathrm{Cu}(\mathrm{I})$ is easily oxidised to ${\mathrm{Cu}}^{+2}$ in aqueous solution

$2{\mathrm{Cu}}^{+}\to {\mathrm{Cu}}^{+2}+\mathrm{Cu}$

${\mathrm{Cu}}^{+1}$ disproportionates to ${\mathrm{Cu}}^{+2}$ and $\mathrm{Cu}$

$(E_{\text{cell }}^{\circ }>0$ for this cell reaction in aqueous solution)

In Fehling's solution, active reagent has $\mathrm{Cu}(\mathrm{II})$ which is reduced to $\mathrm{Cu}(\mathrm{I})$ on reaction with aldehydes.

Hence (D) statement is incorrect