The number of statements correct from the following for Copper (at. no. 29) is/are ____________.
(A) Cu(II) complexes are always paramagnetic.
(B) Cu(I) complexes are generally colourless
(C) Cu(I) is easily oxidized
(D) In Fehling solution, the active reagent has Cu(I)
Answer (integer)
3
Solution
(A) $\mathrm{Cu}$ (II) complexes are always paramagnetic as they have one unpaired electron due to $d^{9}$ configuration of $\mathrm{Cu}(\mathrm{II})$
<br/><br/>
(B) $\mathrm{Cu}(\mathrm{I})$ complexes are generally colourless due to $d^{10}$ configuration.
<br/><br/>
(C) $\mathrm{Cu}(\mathrm{I})$ is easily oxidised to $\mathrm{Cu}^{+2}$ in aqueous solution
<br/><br/>
$2 \mathrm{Cu}^{+} \rightarrow \mathrm{Cu}^{+2}+\mathrm{Cu}$
<br/><br/>
$\mathrm{Cu}^{+1}$ disproportionates to $\mathrm{Cu}^{+2}$ and $\mathrm{Cu}$
<br/><br/>
$\left(E_{\text {cell }}^{\circ}>0\right.$ for this cell reaction in aqueous solution)
<br/><br/>
In Fehling's solution, active reagent has $\mathrm{Cu}(\mathrm{II})$ which is reduced to $\mathrm{Cu}(\mathrm{I})$ on reaction with aldehydes.
<br/><br/>
Hence (D) statement is incorrect
About this question
Subject: Chemistry · Chapter: d and f Block Elements · Topic: Properties of Transition Metals
This question is part of PrepWiser's free JEE Main question bank. 155 more solved questions on d and f Block Elements are available — start with the harder ones if your accuracy is >70%.