JEE MAIN - Chemistry (2020 - 9th January Morning Slot - No. 17)

Complex X of composition Cr(H2O)6Cln has a spin only magnetic moment of 3.83 BM. It reacts with AgNO3 and shows geometrical isomerism. The IUPAC nomenclature of X is :
Hexaaqua chromium (III) chloride
Tetraaquadichlorido chromium(IV) chloride dihydrate
Tetraaquadichlorido chromium (III) chloride dihydrate
Dichloridotetraaqua chromium (IV) chloride dihydrate

Explanation

Given complex Cr(H2O)6Cln

As the magnetic mement is 3.83 BM then

Spin only magnetic moment = $$\sqrt {n\left( {n + 2} \right)} $$ BM = 3.83

$$ \Rightarrow $$ n = 3

Chromium in +3 oxidation state so molecular formula is Cr(H2O)6Cln.

$$ \therefore $$ This formula have following isomers

(a) [Cr(H2O)6]Cl3 : react with AgNO3 but does not show geometrical isomerism.

(b) [Cr(H2O)5Cl]Cl2.H2O react with AgNO3 but does not show geometrical isomerism.

(c) [Cr(H2O)4Cl2]Cl.2H2O react with AgNO3 & show geometrical isomerism.

(d) [Cr(H2O)3Cl3].3H2O does not react with AgNO3 & show geometrical isomerism.

Compound will be [Cr(H2O)4Cl2] Cl.2H2O

IUPAC NAME : Tetraaquadichlorido chromium(III) chloride dihydrate

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