Question

Cuprous ion $(Cu^+ )$ is colourless whereas cupric ion $(Cu^{++} )$ is blue in the aqueous solution. Cuprous ion $(Cu^+ )$ has unpaired electrons while cupric ion $(Cu^{++} )$ does not.

• A. If both assertion and reason are true and reason is a correct explanation of the assertion
• B. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
• C. If the assertion is true but the reason is false
• D. If both the assertion and reason are false

Answer 1

The Correct Option is C

Cuprous ions $\left( Cu ^{+}\right)$ is colourless because it has no unpaired electrons in the $3d$ sub-shell as it has $3 d ^{10}$ configuration. The cupric ion $\left( Cu ^{++}\right)$ has one unpaired electron as it has configuration $3 d^{9}$. By absorbing the visible light, the unpaired electron can migrate from one set of $d$- orbitals to another under the applied field of water molecules. Hence, cupric ion $\left( Cu ^{++}\right)$ in aqueous solution shows blue colour.