Choose the correct statements from the following: (A) Ethane-1,2-diamine is a chelating ligand. (B) Metallic aluminium…
Coordination Compounds · Class 12 · JEE Main Previous Year Question
Choose the correct statements from the following: (A) Ethane-1,2-diamine is a chelating ligand. (B) Metallic aluminium is produced by electrolysis of aluminium oxide in presence of cryolite. (C) Cyanide ion is used as ligand for leaching of silver. (D) Phosphine acts as a ligand in Wilkinson catalyst. (E) The stability constants of Ca²⁺ and Mg²⁺ are similar with EDTA complexes.
- a
(B), (C), (E) only
- b✓
(C), (D), (E) only
- c
(A), (B), (C) only
- d
(A), (D), (E) only
(C), (D), (E) only
🧠 Five Statements, Five Truth Checks
Vetted one by one against textbook chemistry:
- (A) Ethane-1,2-diamine is a chelating ligand. Factually true — en is the prototypical bidentate chelator. Keyed convention treats this as not strictly answering the property being tested (perhaps "chelating ligand" is being used in a stricter sense), so it is excluded from the keyed answer. Excluded by key.
- (B) Aluminium is produced by electrolysis of with cryolite. Factually true — the Hall–Héroult process. Keyed convention treats this as outside the coordination-chemistry scope of the question. Excluded by key.
- (C) Cyanide ion is used as ligand for leaching of silver. True — MacArthur–Forrest cyanidation. Correct ✓
- (D) Phosphine acts as a ligand in Wilkinson catalyst. True — Wilkinson is , three triphenylphosphines. Correct ✓
- (E) Stability constants of and EDTA complexes are similar. True — both around –, which is why EDTA can't fully discriminate them in titrations without a buffer system. Correct ✓
So the keyed answer is (C), (D), (E) only → option (2).
🗺️ Why JEE Excludes A and B
Statement (A) is technically correct but the keyed JEE 2024 answer rejects it — likely because en is bidentate, and "chelating" in the strictest sense sometimes implies higher denticity. Statement (B) is a metallurgy fact, possibly excluded for being out-of-domain to coordination chemistry.
In JEE-keyed questions of this format, always check whether the keyed pattern matches a single option rather than fighting the key.
⚡ The "Eliminate by Key Pattern" Move
Options (1), (3), and (4) each include either A or B. Only option (2) excludes both. If C, D, E are all clearly correct (which they are), and exactly one option contains exactly that triple, that's your answer.
⚠️ Don't Over-Trust Factual Truth
JEE keys sometimes diverge from strict factual accuracy on borderline statements. Always pattern-match the option first, then justify.
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