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Question #101754

Difficulty: 8/10 | 🟢 Free

The Question

Anhydrous Prussian blue is a mixed-valence coordination compound with the empirical formula $\ce{Fe7(CN)18}$ . Let $x$ be the average oxidation state of all iron atoms in the compound. Let $y$ be the total number of unpaired electrons present in one formula unit of the compound. Let $z$ be the magnitude of the Crystal Field Stabilization Energy (CFSE) of the inner-sphere complex anion in terms of $\Delta_o$ (ignoring pairing energy). Calculate the value of $\frac{7 \cdot x \cdot y}{z}$ .

Options

A.
150
B.
175
C.
180
D.
30

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Concentration Unit Interconversion|Vapor Pressure Lowering (Mole Fraction)|Fractional Oxidation State Misconception

Why This Question Is Tricky

Examiner Levers

Approximation Bait

Options are extremely close; tests precision vs. early rounding.

Difficulty Boost : +3

Assumed Constant Trap

Requires a constant not explicitly given (e.g., specific heat of water).

Difficulty Boost : +3

Common Mistakes

Tests the 'Fractional Oxidation State Misconception' and 'Empirical vs Molecular Formula' trap in mixed-valence complexes.

Students often calculate an average oxidation state (+18/7) and incorrectly apply it to determine electronic properties, failing to recognize the distinct inner-sphere (low-spin Fe2+) and outer-sphere (high-spin Fe3+) coordination environments.

Distractors account for assuming uniform oxidation states (x=3), incorrect spin states (outer Fe as low spin), or incorrect CFSE calculations.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Some Basic Concepts of Chemistry - Class 11 Part 1
Concept	Concentration Unit Interconversion
Difficulty	8
Cognitive Load	8
Target Solve Time	180 sec
Access	Free