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Question #44872

Difficulty: 8/10 | 🟢 Free

The Question

An intense purple-colored transition metal oxoanion $X$ is synthesized by the electrolytic oxidation of a green-colored oxoanion $Y$ in an alkaline medium at 298 K. The intense color of $X$ is characterized by a high molar extinction coefficient ( $\epsilon \approx 2400 \, L \, mol^{-1} \, cm^{-1}$ ). Which of the following correctly identifies the nature of the electronic transition responsible for the color of $X$ and its spin-only magnetic moment ( $\mu_s$ )?

Options

A.
Fully allowed $t_1 \rightarrow e$ LMCT; $\mu_s = 0$ B.M.
B.
Partially allowed $e \rightarrow t_2$ $d-d$ transition; $\mu_s = 1.73$ B.M.
C.
Fully allowed $t_2 \rightarrow t_1^*$ MLCT; $\mu_s = 0$ B.M.
D.
Spin-allowed $t_1 \rightarrow e$ LMCT; $\mu_s = 1.73$ B.M.

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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

Magnetic Moment Quenching|Color and Charge Transfer|Color and d-d Transitions

Why This Question Is Tricky

Common Mistakes

The question tests the distinction between $d-d$ transitions and charge transfer spectra.

A common student trap is assuming that intense color in transition metal complexes necessitates unpaired $d$ -electrons undergoing $d-d$ transitions, leading to an incorrect assignment of a non-zero magnetic moment (e.g., $\mu_s = 1.73$ B.M.).

By specifying a $d^0$ system (\ce{MnO4^-}) with a high molar absorptivity, the problem forces the recognition of LMCT.

Furthermore, it probes advanced Molecular Orbital Theory knowledge by requiring the identification of the specific $t_1 \rightarrow e$ transition in tetrahedral complexes, distinguishing it from MLCT or incorrect $d-d$ assignments.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	D and F Block Elements - Class 12
Concept	Magnetic Moment Quenching
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free