Take timed practice tests on Coordination Compounds for JEE Main and JEE Advanced with session-wise drills, score review, and explanation-led revision.
Six 20-question timed sessions plus a 60-question chapter module. Each item is original and reframed for copyright safety.
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1. In [Cu(NH₃)₄]²⁺, the coordination number of Cu is:
Explanation: The coordination number is the number of ligands directly bonded to the central metal ion. Here Cu²⁺ is bonded to 4 NH₃ molecules, so CN = 4.
2. NH₃ is classified as which type of ligand?
Explanation: NH₃ donates one lone pair through the N atom — it binds to the metal through only one point. Hence it is a monodentate ligand.
3. The IUPAC name of [Co(NH₃)₆]³⁺ is:
Explanation: IUPAC naming for coordination cation: ligands in alphabetical order (with multiplying prefixes) + metal name + oxidation state in parentheses. So: hexaammine-cobalt(III).
4. The oxidation state of Fe in K₄[Fe(CN)₆] is:
Explanation: K₄[Fe(CN)₆]: 4(+1) + x + 6(−1) = 0 → 4 + x − 6 = 0 → x = +2. Iron is in +2 oxidation state (ferrocyanide).
5. In [NiCl₄]²⁻, Ni²⁺ is sp³ hybridised. This complex is:
Explanation: Ni²⁺ has d⁸ configuration. With weak field Cl⁻ ligands: sp³ hybridisation → tetrahedral geometry. Unpaired electrons remain → paramagnetic. Compare with [Ni(CN)₄]²⁻ (dsp² hybridisation, square planar, diamagnetic) due to strong CN⁻.
6. In an octahedral crystal field, the d-orbitals split into:
Explanation: In an octahedral field, ligands approach along axes. Orbitals pointing at ligands (dx²-y², dz²) = eg set (higher energy). Orbitals between axes (dxy, dxz, dyz) = t₂g set (lower energy). Δo = energy gap between eg and t₂g.
7. Geometrical isomers exist for which complex?
Explanation: [Pt(NH₃)₂Cl₂] is a square planar complex Ma₂b₂ type — it shows cis (same side) and trans (opposite side) geometrical isomerism. Cisplatin (cis isomer) is the anticancer drug.
8. Which of the following is the strongest ligand according to the spectrochemical series?
Explanation: Spectrochemical series (weak to strong field): I⁻
9. Ethylenediamine (en) is a bidentate ligand because:
Explanation: Ethylenediamine (H₂N−CH₂−CH₂−NH₂) has two −NH₂ groups, each donating a lone pair to the metal. It forms a 5-membered chelate ring, making it bidentate.
10. The magnetic moment (spin only) of [Fe(CN)₆]³⁻ is approximately:
Explanation: Fe³⁺ is d⁵. CN⁻ is a strong field ligand → large Δo → all electrons pair up in t₂g. Configuration: t₂g⁵ eg⁰ → 1 unpaired electron. μ = √(n(n+2)) = √(1×3) = √3 ≈ 1.73 BM.
11. A larger stability constant (Kf) for a coordination compound indicates:
Explanation: The stability constant (Kf = formation constant) measures how readily the complex forms: M + nL ⇌ [MLn]. A larger Kf means the equilibrium lies far to the right — the complex is more stable.
12. In [Cr(en)₃]³⁺ (en = ethylenediamine), the hybridisation of Cr is:
Explanation: Cr³⁺ is d³. en is a strong field ligand. In octahedral coordination with strong field: inner orbital complex with d²sp³ hybridisation (using 3d, 4s, and 4p orbitals). 3 unpaired electrons remain (t₂g³).
13. Which pair shows linkage isomerism?
Explanation: Linkage isomerism occurs with ambidentate ligands (can bind through two different atoms). NO₂⁻ can bind through N (nitro) or O (nitrito). [Co(NH₃)₅(NO₂)]²⁺ = nitro; [Co(NH₃)₅(ONO)]²⁺ = nitrito isomer.
14. The central metal ion in haemoglobin is:
Explanation: Haemoglobin contains Fe²⁺ at the centre of the porphyrin ring (heme group). It binds O₂ reversibly. In CO poisoning, CO binds Fe²⁺ much more strongly than O₂.
15. Ionisation isomers [Co(NH₃)₅Br]SO₄ and [Co(NH₃)₅SO₄]Br differ in:
Explanation: Ionisation isomers have same formula but different ions in the coordination sphere vs. the counter-ion (outer sphere). [Co(NH₃)₅Br]SO₄: Br inside, SO₄²⁻ outside. [Co(NH₃)₅SO₄]Br: SO₄²⁻ inside, Br⁻ outside. They produce different ions in solution.
16. CFSE (Crystal Field Stabilisation Energy) for d⁶ in a strong octahedral field (low spin) is:
Explanation: Low spin d⁶ in octahedral: t₂g⁶ eg⁰. CFSE = 6×(−0.4Δo) + 0×(+0.6Δo) = −2.4Δo (ignoring pairing energy correction). This high stability is why [Fe(CN)₆]⁴⁻ (Fe²⁺ d⁶, strong CN⁻) is so stable.