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Question #44874
The Question
A solution of the diamagnetic square planar complex \textit{trans}-\ce{[Ni(L)2Cl2]} (where \ce{L} is a bulky phosphine ligand) in a non-polar solvent at establishes a thermodynamic equilibrium with its \textit{cis}-isomer. Due to severe steric hindrance between the bulky \ce{L} ligands, the \textit{cis}-isomer undergoes a complete tetrahedral twist, adopting a high-spin electronic configuration. If the observed effective magnetic moment () of the equilibrium mixture is , what is the mole percentage of the \textit{cis}-isomer in the solution? (Assume spin-only magnetic moments for all species).
Options
- A.
25%
- B.
50%
- C.
12.5%
- D.
75%
Check Your Answer
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|Geometric Isomerism Requirements|Valence Bond Theory Hybridization
Why This Question Is Tricky
Common Mistakes
The core trap lies in the rote memorization that '\ce{Ni(II)} with strong field phosphine ligands is always square planar and diamagnetic.' Students often overlook that geometric isomerism (cis vs. trans) can dictate the coordination geometry due to steric hindrance.
The bulky ligands in the cis-position force a tetrahedral twist to relieve steric strain, lifting the degeneracy and unquenching the magnetic moment.
Furthermore, the problem tests the physical chemistry principle that molar magnetic susceptibility (and thus ) is additive in an equilibrium mixture.
A common trap is averaging the magnetic moments directly (), which incorrectly yields .
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 |