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Question #44727

Difficulty: 8/10 | 🟢 Free

The Question

An aqueous solution is prepared by dissolving $2.665 \text{ g}$ of a dark green coordination compound with the empirical formula $\ce{CrCl3.6H2O}$ (Molar mass = $266.5 \text{ g mol}^{-1}$ ) in $100 \text{ g}$ of water. The freezing point of this solution is $-0.372^\circ\text{C}$ ( $K_f$ for water = $1.86 \text{ K kg mol}^{-1}$ ). Assume $100\%$ ionization of the complex.

When $2.665 \text{ g}$ of this complex is treated with excess $\ce{AgNO3(aq)}$ , $x \text{ g}$ of a white precipitate is formed.

When another $2.665 \text{ g}$ sample of the complex is kept over concentrated $\ce{H2SO4}$ in a desiccator, it loses $y \text{ g}$ of its mass.

Let $z$ be the total number of stereoisomers possible for the complex cation.

What are the values of $x$ , $y$ , and $z$ ? (Molar mass of $\ce{AgCl} = 143.5 \text{ g mol}^{-1}$ )

Options

A.
$x = 1.435$ , $y = 0.36$ , $z = 2$
B.
$x = 2.870$ , $y = 0.18$ , $z = 1$
C.
$x = 4.305$ , $y = 0.00$ , $z = 1$
D.
$x = 1.435$ , $y = 0.36$ , $z = 3$

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Molecular Mass Abnormalities|Hydrate and Ionization Isomerism|Crystal Field Splitting (Octahedral)

Why This Question Is Tricky

Common Mistakes

This problem tests the intersection of Colligative Properties and Coordination Chemistry (Hydrate Isomerism).

Students often blindly calculate the van't Hoff factor assuming simple salts, or assume the empirical formula $\ce{CrCl3.6H2O}$ implies $i=4$ .

The trap requires deducing the exact coordination sphere $\ce{[Cr(H2O)4Cl2]Cl.2H2O}$ from the freezing point depression.

A secondary stereochemical trap exists: students frequently assume the \textit{cis} isomer of any octahedral complex is optically active, confusing $\ce{MA4B2}$ with $\ce{M(AA)2B2}$ , which would incorrectly lead to $z=3$ .

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Solutions - Class 12
Concept	Molecular Mass Abnormalities
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free