Question

Complex X of composition $Cr(H_{2}O{)}_{6}C{l}_n$ has a spin only magnetic moment of 3.83 BM. It reacts with $AgN{O}_3$ and shows geometrical isomerism. The IUPAC nomenclature of X is :

• A. Tetraaquadichlorido chromium(IV) chloride dihydrate
• B. Hexaaqua chromium(III) chloride
• C. Dichloridotetraaqua chromium(IV) chloride dihydrate
• D. Tetraaquadichlorido chromium(III) chloride dihydrate

Answer 1

Answer: (D)

$Cr{\left(H_{2}O\right)}_{6}C{l}_n$ if magnetic mement is 3.83 BM then it contain three unpaired electrons. It means chromium in +3 oxidation state so molecular formula is $Cr{\left(H_{2}O\right)}_{6}C{l}_3$
$\therefore$ This formula have following isomers
(a)$\left[Cr{\left(H_{2}O\right)}_6\right]C{l}_3:$ react with $AgN{O}_3$ but does not show geometrical isomerism.
(b) $\left[Cr{\left(H_{2}O\right)}_{5}Cl\right]C{l}_2.H_{2}O$ react with $AgN{O}_3$ but does not show geometrical isomerism.
(c) $\left[Cr{\left(H_{2}O\right)}_{4}C{l}_2\right]Cl.2H_{2}O$ react with $AgN{O}_3\&$ show geometrical isomerism.
(d) $\left[Cr{\left(H_{2}O\right)}_{3}C{l}_3\right].3H_{2}O$ does not react with $AgN{O}_3\&$ show geometrical isomerism.
$\left[Cr{\left(H_{2}O\right)}_{4}C{l}_2\right]Cl.2H_{2}O$ react with $AgN{O}_3\&$ show geometrical isomerism and it's IUPAC nomenclature is Tetraaquadichlorido chromium (III) Chloride dihydrate.