Q. Two isomers X and Y with the formula $Cr\left( H_{2}O \right)_{5}{ClBr}_{2}\$were taken for experiment on depression in freezing point. It was found that one mole of X gave depression corresponding to 2 moles of particles and one mole of Y gave depression due to 3 moles of particles. The structural formula of X and Y respectively, are
A) $\left\lbrack Cr\left( H_{2}O \right)_{5}Cl \right\rbrack{Br}_{2};\lbrack Cr\left( H_{2}O \right)_{4}{Br}_{2}\rbrack Cl.H_{2}O$
B) $\left\lbrack Cr\left( H_{2}O \right)_{5}Cl \right\rbrack{Br}_{2};\lbrack Cr\left( H_{2}O \right)_{3}{ClBr}_{2}\rbrack.2H_{2}O\rbrack$
C) $\lbrack Cr\left( H_{2}O \right)_{5}Br\rbrack BrCl;\lbrack Cr\left( H_{2}O \right)_{4}ClBr\rbrack Br.H_{2}O$
D) $\left\lbrack Cr\left( H_{2}O \right)_{4}{Br}_{2} \right\rbrack{ClH}_{2}O;\left\lbrack Cr\left( H_{2}O \right)_{5}Cl \right\rbrack{Br}_{2}$
Explanation
(d)
One mole of X gave depression corresponding to 2 moles of particles, i.e., on ionisation X gives 2 moles of ions , thus it contains only 1 ion outside the coordination sphere and its structural formula is $\lbrack Cr\left( H_{2}O \right)_{4}{Br}_{2}\rbrack Cl.H_{2}O\$while Y gives 3 moles of ions, thus it contains two ions outside the coordination sphere and its structural formula is
$\left\lbrack Cr\left( H_{2}O \right)_{5}\ Cl \right\rbrack{Br}_{2}2$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.