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Question #44550

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The Question

An octahedral cobalt(III) complex has the empirical formula \ce{CoCl3 \cdot 4NH3 \cdot 2H2O}. A $0.05\text{ m}$ aqueous solution of this complex (Isomer X) exhibits a freezing point depression of $0.186^\circ\text{C}$ . When Isomer X is placed over a strong desiccant, it loses $13.36\%$ of its initial mass. Another hydrate isomer of this complex, Isomer Y, does not lose any mass under identical desiccating conditions. Assuming 100% ionization and no dimerization, which of the following represents the correct IUPAC name of Isomer X and the theoretical Van't Hoff factor ( $i$ ) of Isomer Y? (Given: $K_f$ for water = $1.86\text{ K kg mol}^{-1}$ , Atomic masses: Co = 59, Cl = 35.5, N = 14, O = 16, H = 1)

Options

A.
Tetraamminedichloridocobalt(III) chloride dihydrate; $i = 4$
B.
Dichloridotetraamminecobalt(III) chloride dihydrate; $i = 4$
C.
Tetraamminedichloridocobalt(III) chloride dihydrate; $i = 3$
D.
Tetraammineaquachloridocobalt(III) chloride monohydrate; $i = 3$

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Numerical_Precision

Improve calculation stamina and avoid rounding errors in high-stakes competitive examinations.

Concepts Behind This Question

IUPAC Nomenclature Priority|Van’t Hoff Factor (i) Application

Why This Question Is Tricky

Common Mistakes

The hidden variable being tested is the distinction between the coordination sphere and the ionization sphere, specifically through the lens of hydrate isomerism and its effect on the Van't Hoff factor.

Students often overlook that water molecules can act as either covalently bonded ligands or ionically associated water of crystallization.

Failing to correlate the mass loss with the number of counter-ions leads to an incorrect coordination sphere assignment.

Furthermore, the IUPAC nomenclature tests the alphabetical priority rule (ammine before chlorido), which is a common trap.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Coordination Compounds - Class 12
Concept	IUPAC Nomenclature Priority
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free