JEE Main Chemistry · Coordination Compounds PYQ
JEE Main Coordination Compounds Previous Year Questions (2002–2025)
Coordination Compounds is a top-5 Inorganic Chemistry chapter — ~5% weightage with 1–2 questions per session. Alongside p-block and d-&f-block, it anchors the Inorganic Chemistry marks that are the fastest Chemistry score gains available. Most questions trace directly to NCERT lines in Class 12 Chapter 9.
Coordination Compounds PYQs from 2002 to 2025, covering nomenclature, CFT/VBT, isomerism (geometrical & optical), magnetic moment and applications. Each solution cites the NCERT line or reaction scheme it's derived from, so you build NTA's preferred phrasing recall.
Coordination Compounds at a Glance
Key Sub-Topics & What's Tested
Nomenclature
IUPAC rules for naming complex ions, ligand abbreviations, oxidation state assignment, ambidentate ligands.
Werner's Theory & EAN
Primary/secondary valency, Effective Atomic Number rule (18-electron rule), Werner's postulates, conductivity measurements.
Valence Bond Theory (VBT)
Hybridisation (sp³, dsp², sp³d², d²sp³) for different geometries, inner vs outer orbital complexes, limitations of VBT.
Crystal Field Theory (CFT)
Splitting of d-orbitals in octahedral/tetrahedral fields, Δ₀ vs Δt, CFSE calculation, spectrochemical series, high-spin vs low-spin.
Magnetic Moment
μ = √[n(n+2)] BM where n is unpaired electrons, correlation with geometry and ligand field strength.
Isomerism
Geometrical (cis/trans), optical (chirality in octahedral complexes), linkage, ionisation, hydrate, coordination isomerism.
Colour of Complexes
d-d transitions, complementary colour, charge-transfer complexes, why [Zn(H2O)6]²⁺ is colourless but [Cu(H2O)6]²⁺ is blue.
Biological & Industrial Applications
Haemoglobin, chlorophyll, vitamin B12, EDTA complexometric titrations, cisplatin anti-cancer drug.
Question Type Distribution
| Question Type | Share (approx) | Example Pattern |
|---|---|---|
| Nomenclature MCQ | 20% | Identify the correct IUPAC name for [Co(NH3)4Cl2]Cl. |
| Hybridisation / Geometry | 20% | Determine hybridisation of [Ni(CN)4]²⁻ and predict geometry. |
| Magnetic Moment / Unpaired Electrons | 20% | Calculate magnetic moment of [Fe(CN)6]³⁻ using CFT. |
| Isomerism Identification | 15% | Count the number of geometrical isomers of [Co(en)2Cl2]⁺. |
| Colour & CFT Application | 10% | Which ligand produces the largest Δ₀ — explain using spectrochemical series. |
| Applications / Biology | 15% | Metal ion in haemoglobin is? Write coordination number of Mg in chlorophyll. |
How to Solve Coordination Compounds PYQs
- 1Memorise the spectrochemical series. I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H2O < NH3 < en < CN⁻ < CO. This single series decides ~60% of Δ₀ comparisons in PYQs.
- 2Master VBT for 4 common geometries. Tetrahedral (sp³), square planar (dsp²), octahedral (sp³d² or d²sp³), trigonal bipyramidal. Know the ligand field strength that drives each.
- 3For magnetic moment, count unpaired electrons in CFT. Draw the d-orbital splitting diagram for the metal's oxidation state, fill with Hund's rule, count unpaired e⁻, plug into μ = √[n(n+2)].
- 4Isomerism: draw the complex before counting. Don't rely on formula tricks. Physically sketch the octahedron or square planar and move ligands to count isomers.
- 5For nomenclature, follow IUPAC step-by-step. (1) Count ligands, (2) Alphabetise, (3) Name metal with oxidation state in Roman numerals, (4) Apply cation-anion convention. No shortcuts here.
Common Mistakes That Cost Marks
- Wrong oxidation state calculation. Sum of oxidation states = overall charge of complex. Missing the charge on ligands (especially Cl⁻ or CN⁻) is the #1 mistake.
- Confusing inner (d²sp³) and outer (sp³d²) orbital complexes. CN⁻ and CO = inner. H2O and F⁻ = outer. Using the wrong one gives wrong magnetic moment.
- Missing optical isomerism in octahedral complexes. [Co(en)3]³⁺ has optical isomers even though it has no plane of symmetry. NCERT Ch 9 discusses this — read it.
- Using high-spin for CO or CN⁻ ligands. These are strong-field ligands — always low-spin. The spectrochemical series is non-negotiable here.
- Writing ligand name alphabetically as individual letters vs as full prefix. IUPAC rules alphabetise by ligand name, not by prefix ("di", "tri" don't count).
Related JEE Main Practice
Frequently asked questions
How many Coordination Compounds PYQs should I solve?
Target 50–70 PYQs across 2010–2025. Coordination Compounds has high template reuse — a large share of PYQs are variants of standard nomenclature, magnetic moment or isomerism questions.
Is NCERT Class 12 Chapter 9 enough for this chapter?
Yes — for JEE Main, NCERT + 5 years of PYQs is sufficient for 20+/25 in this chapter. Coaching reference books for Inorganic are optional for this chapter specifically; the NCERT is remarkably thorough.
Which hybridisation questions are most asked?
d²sp³ octahedral vs sp³d² octahedral (depends on ligand field strength) and dsp² square planar vs sp³ tetrahedral (for 4-coordinate complexes). Master these four patterns and you cover most hybridisation PYQs.
How many optical isomers does [Co(en)3]³⁺ have?
Two — a pair of enantiomers (Δ and Λ). This is a NCERT-level result and shows up in PYQs as-is. Standard memorise-it answer.
What's the magnetic moment of a Fe³⁺ complex with weak-field ligand?
Fe³⁺ is d⁵. With weak-field ligand (high-spin), 5 unpaired electrons → μ = √(5·7) ≈ 5.92 BM. With strong-field (low-spin), 1 unpaired → μ = √3 ≈ 1.73 BM. Know both cases.
Do JEE Main PYQs test CFSE calculation?
Occasionally — usually as a comparison question (which complex has higher/lower CFSE) rather than a direct numerical. Know CFSE = -0.4Δ₀ per t2g electron + 0.6Δ₀ per eg electron.
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