Question

A coordination compound $CrCl_{3} \cdot 4H_{2}O$ gives white precipitate of $AgCl$ with $AgNO_{3}$. The molar conductance of the compound corresponds to two ions. The structural formula of the compound is

• A. $[Cr(H_{2}O )_{4}Cl_{3}]$
• B. $[Cr(H_{2}O )_{3}Cl_{3}]H_{2}O$
• C. $[Cr(H_{2}O)_{4}Cl_{2}]Cl$
• D. $[Cr(H_{2}O )_{4}Cl]Cl_{2}$

Answer 1

Answer: (C)

It gives precipitate with $AgNO_{3}$ it means it gives $Cl^{-}$ ions in the solution. Since conductivity corresponds to two ions, it shows one $Cl^{-}$ is outside the coordination sphere. The structure will be
$[Cr(H_{2}O)_{4}Cl_{2}] Cl \to [Cr(H_{2}O)_{4}Cl_{2}]^{+}+Cl^{-}$
$AgNO_{3}+Cl^{-} \to \underset{\text{white ppt.}}{{Agcl}}+NO^{-}_{3}$