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Question #44121

Difficulty: 8/10 | 🟢 Free

The Question

An aqueous solution of a yellow transition metal oxoanion $\mathbf{P}$ is acidified with dilute $\ce{H2SO4}$ at $298\text{ K}$ , yielding an orange oxoanion $\mathbf{Q}$ . Both $\mathbf{P}$ and $\mathbf{Q}$ are diamagnetic and exhibit intense color due to Ligand-to-Metal Charge Transfer (LMCT). Let $x$ and $y$ be the oxidation states of the central metal in $\mathbf{P}$ and $\mathbf{Q}$ respectively, as represented in their IUPAC Stock notations. Which of the following correctly identifies the Stock notations $(x, y)$ and the fundamental nature of the $\mathbf{P} \rightleftharpoons \mathbf{Q}$ transformation?

Options

A.
(VI), (VI); Non-redox condensation
B.
(VI), (VII); Disproportionation
C.
(IV), (VI); Oxidation
D.
(VI), (III); Reduction

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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

Stock Notation Logic|Dichromate-Chromate Equilibrium

Why This Question Is Tricky

Common Mistakes

The question tests the 'Chemical Exception' where a dramatic color change (yellow to orange) in transition metal complexes is incorrectly assumed to be a redox reaction involving a change in oxidation state.

Students frequently fall into the trap of modifying the Stock notation during the chromate-dichromate shift.

However, the equilibrium ( $2\ce{CrO4^{2-}} + 2\ce{H+} \rightleftharpoons \ce{Cr2O7^{2-}} + \ce{H2O}$ ) is purely a pH-dependent condensation.

The oxidation state of Chromium remains +6 (Stock notation VI) in both the tetrahedral chromate and the bridged dichromate.

The intense colors arise from Ligand-to-Metal Charge Transfer (LMCT) in the $d^0$ metal centers, not from d-d transitions or redox processes.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Redox Reactions - Class 11 Part 2
Concept	Stock Notation Logic
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free