Question

Assertion : Potassium ferricyanide, ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$ is diamagnetic , while potassium ferrocyanide ${\left[Fe{\left(CN\right)}_6\right]}^{4-}$ is paramagnetic.

Reason : Oxidation state of Fe in potassium fericyanide is +2 , but in potassium ferrocyanide its oxidation state is +3.

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

Answer 1

The correct option is B If both assertion and reason are false.

$K_3\left[Fe{\left(CN\right)}_6\right]$ (potassium ferricyanide)
O.S =+3 and configuration of $F{e}^{+3}$ is $d^5$
$C{N}^{-}$ is strong filed ligand so electrons gets paired up and left with one unpaired electron.
therefore, it is slightly paramagnetic in nature, but $K_4\left[Fe{\left(CN\right)}_6\right]$ O.S = +2
and configuration of $F{e}^{+2}$ is $d^6$
Thus, in potassium ferrocyanide all the electrons get paired up and no unpaired electron.
Therefore , it is diamagnetic in nature.

Hence, option (d) is correct.