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Question #44256

Difficulty: 8/10 | 🟢 Free

The Question

Metals $M_1$ and $M_2$ belong to the 3d transition series and both exhibit anomalous ground-state electronic configurations that violate the Aufbau principle. The atomic number of $M_1$ is less than that of $M_2$ .

Consider the following species formed under standard conditions (298 K): (I) Complex $P$ : The homoleptic octahedral complex formed by $M_1^{2+}$ with \ce{H2O}. (II) Complex $Q$ : The homoleptic octahedral complex formed by $M_1^{3+}$ with \ce{CN-}. (III) Compound $R$ : The water-insoluble metal-containing precipitate formed when $M_2^{2+}(aq)$ is treated with excess \ce{KI(aq)}.

Let $\mu_P$ , $\mu_Q$ , and $\mu_R$ be the spin-only magnetic moments (in Bohr Magnetons) of the central metal in $P$ , $Q$ , and $R$ respectively.

Calculate the value of $(\mu_P^2 + \mu_Q^2 + \mu_R^2)$ .

Options

A.
23
B.
26
C.
39
D.
42

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

Aufbau Principle Exceptions|d-block Variable Oxidation States|Spin-Only Magnetic Moment

Why This Question Is Tricky

Common Mistakes

The question tests two major exceptions in d-block chemistry.

First, identifying Cr and Cu via their Aufbau principle anomalies.

Second, and more crucially, the 'Hidden Variable' is the redox instability of Cu(II) in the presence of iodide ions.

Students often fall into the trap of assuming a simple metathesis reaction to form CuI2 (a d9 paramagnetic species with n=1, leading to an incorrect sum of 42).

Recognizing that I- acts as a reducing agent to form diamagnetic CuI (d10, n=0) is the key discriminator for Advanced-level students.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Structure of Atom - Class 11 Part 1
Concept	Aufbau Principle Exceptions
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free