Coordination Compounds Previous Year Questions — JEE Main Chemistry
68 past-year Coordination Compounds questions from JEE Main (Chemistry) — page 9.
Q62 (2024)
Match List I with List II
<div style="overflow-x: auto; margin: 1rem 0;"><div class="rankbit-table-container"><table class="rankbit-table"><thead><tr><th style="border: 1px solid #888; padding: 8px;">LIST-I (Substances)</th><th style="border: 1px solid #888; padding: 8px;">LIST-II (Element Present)</th></tr></thead><tbody><tr><td style="border: 1px solid #888; padding: 8px;">A. Ziegler catalyst</td><td style="border: 1px solid #888; padding: 8px;">I. Rhodium</td></tr><tr><td style="border: 1px solid #888; padding: 8px;">B. Blood Pigment</td><td style="border: 1px solid #888; padding: 8px;">II. Cobalt</td></tr><tr><td style="border: 1px solid #888; padding: 8px;">C. Wilkinson catalyst</td><td style="border: 1px solid #888; padding: 8px;">III. Iron</td></tr><tr><td style="border: 1px solid #888; padding: 8px;">D. Vitamin $B_{12}$</td><td style="border: 1px solid #888; padding: 8px;">IV. Titanium</td></tr></tbody></table></div></div>
Choose the correct answer from the options given below:
- $\text{A-II, B-IV, C-I, D-III}$
- $\text{A-II, B-III, C-IV, D-I}$
- $\text{A-III, B-II, C-IV, D-I}$
- $\text{A-IV, B-III, C-I, D-II}$
### Core Logic
Let us identify the central metal atom/element present in each of the given coordination complexes or biological molecules:
1. **Ziegler-Natta catalyst**: Used for polymerization of alkenes. Its chemical composition involves $TiCl_4$ and $(C_2H_5)_3Al$. Hence, the transition metal present is Titanium (IV).
2. **Blood pigment (Haemoglobin)**: The oxygen-carrying metalloprotein in red blood cells. It contains an Iron (III) central atom coordinated to a porphyrin ring.
3. **Wilkinson's catalyst**: Used for the hydrogenation of alkenes. Its formula is $[RhCl(PPh_3)_3]$, meaning it contains Rhodium (I).
4. **Vitamin $B_{12}$ (Cyanocobalamin)**: A biologically important coordination compound containing Cobalt (II) at the center of a corrin ring.
### Step 1: Final Mapping
Matching the elements:
(A) Ziegler catalyst $\rightarrow$ (IV) Titanium
(B) Blood Pigment $\rightarrow$ (III) Iron
(C) Wilkinson catalyst $\rightarrow$ (I) Rhodium
(D) Vitamin $B_{12}$ $\rightarrow$ (II) Cobalt
This strictly maps to sequence A-IV, B-III, C-I, D-II.
### Pattern Recognition
Always memorize the central metal for famous catalysts and biomolecules: Chlorophyll (Mg), Haemoglobin (Fe), Vitamin B12 (Co), Wilkinson (Rh), Ziegler-Natta (Ti).
### Evaluation Rubric / Model Answer
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### Chapter Mix
Class 12 Chemistry: Coordination Compounds
Class 12 Chemistry: d and f Block Elements
Q1754 (2024)
The coordination geometry around the manganese in decacarbonyldimanganese(0)
- $\text{Octahedral}$
- $\text{Trigonal bipyramidal}$
- $\text{Square pyramidal}$
- $\text{Square planar}$
### Core Logic
Decacarbonyldimanganese(0) is $Mn_2(CO)_{10}$.
In this binuclear carbonyl, there is one $Mn-Mn$ bond. Each $Mn$ atom is additionally bonded to five carbonyl ($CO$) ligands.
Therefore, the coordination number of each $Mn$ atom is $1 + 5 = 6$.
The arrangement of these 6 bonds around each $Mn$ atom is octahedral.
{{SOL_IMG1}}
### Evaluation Rubric / Model Answer
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### Chapter Mix
Class 12 Chemistry: Coordination Compounds
Q81 (2024)
Number of complexes which show optical isomerism among the following is
$cis-[\mathrm{Cr}(ox)_2\mathrm{Cl}_2]^{3-}$, $[\mathrm{Co}(en)_3]^{3+}$
$cis-[\mathrm{Pt}(en)_2\mathrm{Cl}_2]^{2+}$, $cis-[\mathrm{Co}(en)_2\mathrm{Cl}_2]^{+}$
$trans-[\mathrm{Pt}(en)_2\mathrm{Cl}_2]^{2+}$, $trans-[\mathrm{Cr}(ox)_2\mathrm{Cl}_2]^{3-}$
### Core Logic
Optical isomerism is shown by complexes that are chiral, meaning they lack both a plane of symmetry (POS) and a center of symmetry (COS).
1. $cis-[\mathrm{Cr}(ox)_2\mathrm{Cl}_2]^{3-}$: Cis configuration with bidentate ligands lacks a POS/COS. $\rightarrow$ Shows optical isomerism.
2. $[\mathrm{Co}(en)_3]^{3+}$: Tris(bidentate) complex lacks POS/COS. $\rightarrow$ Shows optical isomerism (exists as $\Delta$ and $\Lambda$ enantiomers).
3. $cis-[\mathrm{Pt}(en)_2\mathrm{Cl}_2]^{2+}$: Cis configuration lacks POS/COS. $\rightarrow$ Shows optical isomerism.
4. $cis-[\mathrm{Co}(en)_2\mathrm{Cl}_2]^{+}$: Cis configuration lacks POS/COS. $\rightarrow$ Shows optical isomerism.
5. $trans-[\mathrm{Pt}(en)_2\mathrm{Cl}_2]^{2+}$: Trans configuration is highly symmetric and contains a POS (along the square plane). $\rightarrow$ Cannot show optical isomerism.
6. $trans-[\mathrm{Cr}(ox)_2\mathrm{Cl}_2]^{3-}$: Trans configuration contains a POS/COS. $\rightarrow$ Cannot show optical isomerism.
### Step 1: Final Tally
Out of the 6 complexes, 4 can show optical isomerism.
The answer is 4.
### Pattern Recognition
For octahedral complexes with bidentate ligands: $cis$ isomers generally show optical isomerism, whereas $trans$ isomers have a plane of symmetry and are optically inactive. $[M(L-L)_3]$ types are always chiral.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Chemistry: Coordination Compounds
Q1850 (2024)
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 act as a ligand in Wilkinson catalyst.
(E) The stability constants of $Ca^{2+}$ and $Mg^{2+}$ are similar with EDTA complexes.
Choose the correct answer from the options given below:
- $\text{(B), (C), (E) only}$
- $\text{(C), (D), (E) only}$
- $\text{(A), (B), (C) only}$
- $\text{(A), (D), (E) only}$
### Core Logic
(A) Ethane-1,2-diamine (en) is a bidentate ligand. Because it coordinates through two nitrogen atoms to the same metal ion, it forms a ring, making it a chelating ligand. (True)
{{SOL_IMG1}}
(B) In the Hall-Heroult process, metallic aluminium is produced by the electrolysis of molten alumina ($Al_2O_3$). Cryolite ($Na_3AlF_6$) is added to lower the melting point and increase conductivity. (True)
(C) In the extraction of silver (MacArthur-Forrest cyanide process), $Ag$ ore is leached with a dilute solution of $NaCN$ or $KCN$ in the presence of air to form the soluble complex $[Ag(CN)_2]^-$. Thus, cyanide acts as a ligand. (True)
$$Ag_2S + NaCN \rightleftharpoons Na[Ag(CN)_2] + Na_2S$$
(D) Wilkinson's catalyst is $[RhCl(PPh_3)_3]$. The ligand is triphenylphosphine ($PPh_3$), not phosphine ($PH_3$). (False)
(E) The stability constant of the $Ca^{2+}$-EDTA complex is significantly higher than that of the $Mg^{2+}$-EDTA complex, which is why EDTA is used to estimate hardness sequentially. They are not similar. (False)
### Step 1: Conclusion
Only statements (A), (B), and (C) are correct.
### Evaluation Rubric / Model Answer
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### Chapter Mix
Class 12 Chemistry: Coordination Compounds
Class 12 Chemistry: General Principles and Processes of Isolation of Elements
Q67 (2024)
Aluminium chloride in acidified aqueous solution forms an ion having geometry
- $\text{Octahedral}$
- $\text{Square Planar}$
- $\text{Tetrahedral}$
- $\text{Trigonal bipyramidal}$
### Core Logic
$AlCl_3$ dissolves in acidified water to form the hexaquaaluminium(III) complex ion.
The reaction can be represented as: $AlCl_3 + 6H_2O \rightarrow [Al(H_2O)_6]^{3+} + 3Cl^-$
### Step 1: Analyzing Geometry
The central aluminium atom coordinates with 6 water molecules, giving a coordination number of 6. A coordination number of 6 results in an octahedral geometry ($sp^3d^2$ hybridization).
### Evaluation Rubric / Model Answer
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### Chapter Mix
Class 12 Chemistry: Coordination Compounds
Class 11 Chemistry: The p-Block Elements
