Question

Assertion : $[Fe(H_{2}O ) _{6}]^{3+}$ is strongly paramagnetic whereas $[Fe(CN)_{6}]^{3-}$ is weakly paramagnetic.
Reason : $H_{2}O$ is a weak field ligand and $CN^{-}$ is a strong field ligand.

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

Answer 1

Answer: (A)

$\left[ Fe ( CN )_{6}\right]^{3-} \Rightarrow C \ \bar {N} \Rightarrow $ Strong field ligand.
$Fe ^{3+}=[\text{Ar}] 3 d ^{5}($ Refer $o$ image o1)
1. 1 unpaired electrons.
2. Weakly paramagnetic
$\left[ Fe \left( H _{2} O \right)_{6}\right]^{3+} \Rightarrow H _{2} O \Rightarrow $ Weak field ligand.
$\Rightarrow Fe ^{3+} \Rightarrow [ Ar ] 3 d ^{5}$ (Refer o image o2)
5 unpaired electrons.
$\left[ Fe \left( H _{2} O \right)_{6}\right]^{2+}=$ Strong paramagnetic.