IIT JAM Chemistry
100 Concept-Based High-Yield MCQs with Answers & Explanations
Important: These questions are presented as IIT JAM-style / concept-based practice MCQs. An individual question is not labelled as an actual IIT JAM PYQ unless its original paper and official answer key have been independently verified. This avoids assigning incorrect years to generated practice questions.
ORGANIC CHEMISTRY (1–35)
1. [GOC] The correct order of acidity is:
View Answer
Answer: a) H2O > CH3OH > CH3CH2OH > (CH3)3COH
Alkyl groups exert a +I effect and destabilize the alkoxide ion. Therefore, in aqueous solution, acidity decreases as alkyl substitution increases.
2. [Stereochemistry] The total number of stereoisomers of 2,3-dibromobutane is:
View Answer
Answer: b) 3
The stereoisomers are (2R,3R), (2S,3S), and meso-(2R,3S).
3. [Reaction Mechanism] Addition of HCl to 1,3-cyclopentadiene can give:
View Answer
Answer: a) An allylic chloride
Electrophilic addition to the conjugated diene proceeds through an allylic carbocation, followed by chloride attack. The product nomenclature depends on the numbering convention used for the resulting cyclopentene.
4. [Reagents] The reagent combination used for anti-Markovnikov hydration of an alkene is:
View Answer
Answer: b)
Hydroboration–oxidation gives anti-Markovnikov alcohol formation with syn addition.
5. [Pericyclic] The Diels–Alder reaction is a:
View Answer
Answer: b) [4+2] cycloaddition
A conjugated diene containing 4π electrons reacts with a dienophile containing 2π electrons.
6. [GOC] The most stable carbocation among the following is:
View Answer
Answer: d) (CH3)3C+
For simple alkyl carbocations, the usual stability order is 3° > 2° > 1° > methyl due to hyperconjugation and electron donation.
7. [Stereochemistry] An SN2 reaction at a stereogenic carbon generally results in:
View Answer
Answer: b) Inversion of configuration
SN2 occurs by backside attack, producing Walden inversion at the reacting stereocentre.
8. [Pericyclic] The Cope rearrangement is a:
View Answer
Answer: b) [3,3] sigmatropic rearrangement
The Cope rearrangement is a thermal, concerted [3,3]-sigmatropic rearrangement of a 1,5-diene.
9. [Reagents] Which reagent converts RCOOH into RCH2OH?
View Answer
Answer: a) LiAlH4
LiAlH4 is a strong reducing agent that converts carboxylic acids into primary alcohols.
10. [Physical Organic] Which compound has the largest dipole moment among the following?
View Answer
Answer: b) CH3Cl
The dipole moment depends on both charge separation and bond length/electronic distribution. CH3Cl has a slightly larger experimental dipole moment than CH3F.
11. [Stereochemistry] The number of optically active stereoisomers of tartaric acid is:
View Answer
Answer: b) 2
Tartaric acid has two optically active enantiomers, (R,R) and (S,S). The third stereoisomer is meso and is optically inactive.
12. [Reaction Mechanism] The characteristic intermediate of a simple SN1 reaction is:
View Answer
Answer: a) Carbocation
The slow ionization step produces a carbocation intermediate.
13. [Name Reaction] Which compound can undergo the Cannizzaro reaction?
View Answer
Answer: c) Benzaldehyde
Benzaldehyde has no α-hydrogen and therefore undergoes base-induced disproportionation.
14. [Name Reaction] The Hofmann bromamide degradation commonly uses:
View Answer
Answer: b) Br2/KOH
A primary amide gives a primary amine containing one fewer carbon atom.
15. [Pericyclic] Woodward–Hoffmann rules are based primarily on:
View Answer
Answer: a) Orbital symmetry
The rules determine allowed and forbidden pericyclic processes from conservation of orbital symmetry.
16. [Conformation] The most stable conformation of cyclohexane is:
View Answer
Answer: c) Chair
The chair conformation minimizes both angle strain and torsional strain.
17. [NMR] The aldehydic proton generally appears in 1H NMR near:
View Answer
Answer: d) 9–10 ppm
The aldehydic proton is strongly deshielded by the carbonyl group.
18. [Elimination] E2 elimination is characterized by:
View Answer
Answer: d) A single concerted step
C–H bond breaking and leaving-group departure occur in the same elementary step.
19. [Pericyclic] The Claisen rearrangement is a:
View Answer
Answer: b) [3,3] shift
An allyl vinyl ether undergoes a thermal [3,3]-sigmatropic rearrangement.
20. [Reagents] The Wolff–Kishner reduction uses:
View Answer
Answer: a)
Aldehydes and ketones are converted into hydrocarbons under strongly basic conditions.
21. [GOC] Which alkyl group has the strongest +I effect?
View Answer
Answer: d) t-C4H9–
The electron-releasing inductive effect generally increases with alkyl substitution.
22. [Stereochemistry] Which compound is achiral?
View Answer
Answer: b) 2-Chloropropane
The carbon atom of 2-chloropropane has two identical CH3 groups, so it is not stereogenic.
23. [IR] A typical C≡C stretching absorption occurs approximately at:
View Answer
Answer: b) 2100–2260 cm−1
The C≡C stretching vibration generally occurs in the 2100–2260 cm−1 region.
24. [Grignard] Reaction of PhMgBr with CO2 followed by acidic work-up gives:
View Answer
Answer: a) Benzoic acid
The Grignard reagent attacks CO2 to form a carboxylate, which gives benzoic acid after protonation.
25. [Grignard] Reaction of a nitrile RCN with R′MgX followed by hydrolysis generally gives:
View Answer
Answer: b) Ketone
The Grignard reagent adds to the nitrile and the resulting imine species hydrolyses to a ketone.
26. [Pericyclic] A [1,5]-hydrogen sigmatropic shift involves movement of hydrogen across a conjugated π-system through a:
View Answer
Answer: a)
A [1,5]-H shift is a sigmatropic rearrangement in which the hydrogen moves from one end of the conjugated system to the other appropriate position.
27. [Reagents] Clemmensen reduction uses:
View Answer
Answer: b) Zn(Hg)/HCl
Clemmensen reduction converts aldehydes and ketones to hydrocarbons under strongly acidic conditions.
28. [GOC] The most acidic hydrogen in acetylacetone is located on the:
View Answer
Answer: b) Central methylene group
Removal of a proton from the central CH2 gives an enolate stabilized by both carbonyl groups.
29. [Stereochemistry] In trans-CH3CH=CHCl, the higher-priority groups are on opposite sides. The configuration is:
View Answer
Answer: a) E
By CIP priority, Cl is higher than H and CH3 is higher than H. Opposite sides therefore correspond to E.
30. [Name Reaction] The Favorskii rearrangement is characteristically associated with:
View Answer
Answer: a) α-Halo ketones
Under basic conditions, α-halo ketones undergo rearrangement, commonly through a cyclopropanone-related intermediate.
31. [13C NMR] How many 13C NMR signals are expected for mesitylene (1,3,5-trimethylbenzene)?
View Answer
Answer: c) 3
There are three carbon environments: substituted ring carbons, ring CH carbons, and methyl carbons.
32. [Name Reaction] Reaction of an aldehyde with a nitroalkane under basic conditions is known as:
View Answer
Answer: b) Henry reaction
The Henry reaction is also called the nitroaldol reaction.
33. [Name Reaction] Oppenauer oxidation is commonly performed using:
View Answer
Answer: a)
Oppenauer oxidation is the reverse of Meerwein–Ponndorf–Verley reduction and commonly uses an aluminium alkoxide.
34. [Electrocyclic] A thermal electrocyclic reaction of a 6π-electron system proceeds by:
View Answer
Answer: a) Conrotatory motion
For thermal electrocyclic reactions, 4n+2 π electrons undergo conrotatory ring closure/opening.
35. [Alkene Stability] Which is the most stable alkene among the following?
View Answer
Answer: c) 2-Methylpropene
2-Methylpropene is trisubstituted, whereas trans-2-butene is disubstituted. Greater alkyl substitution generally increases alkene stability.
INORGANIC CHEMISTRY (36–65)
36. [Coordination] The number of geometrical isomers of [MA3B3] in an octahedral complex is:
View Answer
Answer: b) 2
The two geometrical arrangements are fac and mer.
37. [Coordination] The geometry and hybridization commonly assigned to [Ni(CN)4]2− are:
View Answer
Answer: b) Square planar, dsp2
CN− is a strong-field ligand and Ni(II) is d8; the complex is square planar and diamagnetic.
38. [Coordination] In [Co(en)2Cl2]+, the oxidation state of cobalt is:
View Answer
Answer: c) +3
en is neutral and two Cl− ligands contribute −2. Since the complex charge is +1, Co must be +3.
39. [Coordination] Which complex has the largest octahedral splitting Δ0?
View Answer
Answer: d) [Co(CN)6]3−
CN− is a stronger-field ligand than NH3, H2O and F−.
40. [Coordination] Number of unpaired electrons in high-spin [Fe(H2O)6]2+ is:
View Answer
Answer: d) 4
Fe2+ is d6. H2O is a weak-field ligand, giving high-spin t2g4eg2 with four unpaired electrons.
41. [Organometallic] The effective atomic number (EAN) of Cr in Cr(CO)6 is:
View Answer
Answer: c) 36
Cr contributes 24 electrons and six CO ligands donate 12 electrons: 24 + 12 = 36.
42. [Coordination] The linkage isomer of [Co(NH3)5(NO2)]2+ is:
View Answer
Answer: a)
NO2− can coordinate through N (nitro) or O (nitrito), producing linkage isomers.
43. [Crystal Field] The CFSE of a high-spin d5 octahedral ion, excluding pairing energy, is:
View Answer
Answer: b) 0
t2g3eg2 gives 3(−0.4Δ0) + 2(+0.6Δ0) = 0.
44. [Bioinorganic] The cis isomer of [PtCl2(NH3)2] is the well-known drug:
View Answer
Answer: a) Cisplatin
Cisplatin is cis-[PtCl2(NH3)2] and is widely used as an anticancer drug.
45. [Magnetism] The spin-only magnetic moment for a species with five unpaired electrons is:
View Answer
Answer: d) 5.92 BM
μ = √[n(n+2)] = √[5(7)] = √35 ≈ 5.92 BM.
46. [Coordination] Which ligand generally gives the strongest chelate effect with Ni2+?
View Answer
Answer: c) EDTA
EDTA is a multidentate ligand and forms several coordinate bonds with the same metal ion.
47. [Electronic Spectra] [Ti(H2O)6]3+ is a d1 complex. In the simplest crystal-field picture, it has:
View Answer
Answer: a) One main d–d transition
A d1 ion has one electron in t2g, which can be promoted to eg.
48. [Coordination] Which complex is kinetically inert under ordinary conditions?
View Answer
Answer: a) [Co(NH3)6]3+
Low-spin Co(III), d6 complexes are typically substitution-inert.
49. [Magnetism] The spin-only magnetic moment of high-spin Fe3+ is:
View Answer
Answer: d) 5.92 BM
Fe3+ is d5 and high spin, giving five unpaired electrons.
50. [Jahn–Teller] A classic strong Jahn–Teller distortion in an octahedral complex is associated with:
View Answer
Answer: c) d9
Octahedral d9 configurations, such as Cu(II), commonly show strong Jahn–Teller distortion.
51. [Periodic Trends] The correct increasing order of radius for these isoelectronic ions is:
View Answer
Answer: b)
All have ten electrons. Increasing nuclear charge pulls the same electron cloud more strongly.
52. [Periodic Trends] Among the halogens, the electron affinity is most negative for:
View Answer
Answer: b) Cl
Although F is more electronegative, its compact 2p orbital causes greater electron–electron repulsion. Cl therefore has the more negative electron affinity.
53. [Periodic Trends] Which oxide is amphoteric?
View Answer
Answer: c) Al2O3
Al2O3 reacts with both acids and strong bases.
54. [Periodic Trends] Lanthanide contraction is mainly caused by:
View Answer
Answer: a)
4f electrons shield the increasing nuclear charge poorly, causing progressive contraction.
55. [Periodic Trends] Among the following, the strongly acidic oxide is:
View Answer
Answer: d) SO3
SO3 reacts with water to form H2SO4 and is a strongly acidic oxide.
56. [Organometallic] Which species is expected to have the highest CO stretching frequency due to the least metal-to-CO back-bonding?
View Answer
Answer: a)
A more electron-poor metal centre has weaker π back-donation into CO π* orbitals, so the C–O bond is stronger and its stretching frequency is higher.
57. [18-Electron Rule] Which of the following has an electron count different from 18?
View Answer
Answer: d) [V(CO)6]+
V+ is d4; six CO ligands donate 12 electrons, giving 16 electrons total. The first three species have 18 electrons.
58. [Bioinorganic] The metal present in vitamin B12 is:
View Answer
Answer: b) Co
Vitamin B12 is a cobalt-containing corrinoid compound.
59. [Bioinorganic] The principal oxygen-carrying protein in human blood is:
View Answer
Answer: b) Hemoglobin
Hemoglobin contains heme iron and transports oxygen in blood.
60. [Organometallic] The hapticity of each cyclopentadienyl ligand in ferrocene is:
View Answer
Answer: c) η5
All five carbon atoms of each Cp ring interact with the metal.
61. [Solid State] The packing efficiency of an FCC lattice is approximately:
View Answer
Answer: c) 74%
FCC has a packing efficiency of π/(3√2), approximately 74%.
62. [Solid State] A primitive cubic unit cell contains how many lattice points?
View Answer
Answer: a) 1
Eight corner contributions of 1/8 each give one lattice point per primitive cubic unit cell.
63. [Nuclear Chemistry] In the reaction 147N + 42He → 178O + X, X is:
View Answer
Answer: a) 11H
Mass number: 14 + 4 = 17 + 1. Atomic number: 7 + 2 = 8 + 1. Therefore X is a proton.
64. [Solid State] A Schottky defect consists of:
View Answer
Answer: a)
Stoichiometry and electrical neutrality are maintained by removing equal numbers of cations and anions from their normal lattice sites.
65. [Nuclear Chemistry] If the half-life of 14C is 5730 years, the age of a sample containing 25% of its original 14C is:
View Answer
Answer: b) 11460 years
25% = (1/2)2, so two half-lives have elapsed: 2 × 5730 = 11460 years.
PHYSICAL CHEMISTRY (66–90)
66. [Thermodynamics] For a reversible isothermal process, the entropy change of the system is:
View Answer
Answer: b) qrev/T
For an isothermal reversible process: ΔS = qrev/T.
67. [Thermodynamics] Using the chemistry sign convention, work for reversible isothermal expansion of an ideal gas is:
View Answer
Answer: b)
With w = −∫PextdV and P = nRT/V: w = −nRT ln(V2/V1).
68. [Thermodynamics] At constant temperature and pressure, a spontaneous process has:
View Answer
Answer: b) ΔG < 0
For a spontaneous forward process at constant T and P, ΔG is negative. At equilibrium, ΔG = 0.
69. [Thermodynamics] The temperature derivative of Gibbs free energy for a reaction at constant pressure is:
View Answer
Answer: b)
From dG = VdP − SdT, at constant pressure: (∂G/∂T)P = −S. For a reaction, this becomes −ΔS.
70. [Thermodynamics] The Joule–Thomson coefficient of an ideal gas is:
View Answer
Answer: c) Zero
For an ideal gas, enthalpy depends only on temperature, so an isenthalpic pressure change produces no temperature change.
71. [Thermodynamics] At equilibrium at constant T and P, the Gibbs free energy change of reaction is:
View Answer
Answer: c) Zero
At equilibrium, the reaction driving force vanishes and ΔGreaction = 0.
72. [Thermodynamics] If Th is the hot-reservoir temperature and Tc is the cold-reservoir temperature, Carnot efficiency is:
View Answer
Answer: a)
η = 1 − Tc/Th, with temperatures measured on an absolute scale.
73. [Coordination / Quantum] In an octahedral crystal field, the five d orbitals split into:
View Answer
Answer: b)
The t2g set contains three orbitals and the eg set contains two orbitals.
74. [Quantum] The commutator [x,px] is:
View Answer
Answer: b) iℏ
The canonical commutation relation is [x,px] = iℏ.
75. [Molecular Quantum Chemistry] The ground-state electronic term symbol of O2 is:
View Answer
Answer: b) 3Σg−
Ground-state O2 has two unpaired electrons in degenerate π* orbitals and is therefore a triplet.
76. [Quantum] The zero-point energy of a one-dimensional harmonic oscillator is:
View Answer
Answer: b) ½hν
Ev = (v + 1/2)hν. For v = 0, E = 1/2hν.
77. [Rotational Spectroscopy] The basic rotational selection rule for a rigid heteronuclear diatomic molecule is:
View Answer
Answer: a) ΔJ = ±1
Electric-dipole rotational transitions obey ΔJ = ±1.
78. [Kinetics] A first-order reaction has a half-life of 10 min. The time required for 75% completion is:
View Answer
Answer: b) 20 min
75% completion means 25% remains. Two half-lives reduce the concentration to 25%.
79. [Kinetics] The unit of the rate constant for a second-order reaction is:
View Answer
Answer: c)
For rate = k[A]2, k has units of concentration−1 time−1.
80. [Kinetics] For a zero-order reaction, a plot of [A] versus time is:
View Answer
Answer: b)
[A] = [A]0 − kt, so the slope is −k.
81. [Kinetics] The Arrhenius equation is:
View Answer
Answer: a)
The exponential term describes the fraction of molecules capable of overcoming the activation barrier.
82. [Kinetics] If rate = k[A]2[B], the order with respect to B is:
View Answer
Answer: b) 1
The exponent of [B] in the experimentally determined rate law is its partial order.
83. [Electrochemistry] For Zn|Zn2+||Cu2+|Cu, the reaction quotient is:
View Answer
Answer: b) [Cu2+]/[Zn2+]
The overall reaction is Zn + Cu2+ → Zn2+ + Cu, so Q = a(Zn2+)/a(Cu2+) for the reaction as written.
84. [Electrochemistry] The specific conductivity κ of a strong electrolyte generally:
View Answer
Answer: b) Decreases on dilution
On dilution, the number of ions per unit volume decreases, so specific conductivity decreases. Molar conductivity, in contrast, increases.
85. [Electrochemistry] At equilibrium for an electrochemical cell:
View Answer
Answer: b) Ecell = 0
At equilibrium, ΔG = −nFE = 0, hence E = 0 and Q = K.
86. [Electrochemistry] Kohlrausch's law can be used to determine:
View Answer
Answer: c) Both a and b
Independent ionic migration allows limiting conductivities of weak electrolytes and conductivity-based estimates related to sparingly soluble salts.
87. [Surface Chemistry] In the Langmuir equation θ = KP/(1+KP), the dimension of K is:
View Answer
Answer: b) Inverse pressure
KP must be dimensionless, so K has units inverse to those used for pressure.
88. [Surface Chemistry] The Freundlich adsorption isotherm is:
View Answer
Answer: a)
The empirical Freundlich equation is x/m = kP1/n.
89. [Rotational Spectroscopy] For a rigid diatomic molecule, the rotational constant B is proportional to:
View Answer
Answer: b) 1/(μr2)
B = h/(8π2cI), and I = μr2. Therefore B ∝ 1/(μr2).
90. [Quantum Chemistry] The number of radial nodes in a 3p orbital is:
View Answer
Answer: b) 1
Radial nodes = n − l − 1 = 3 − 1 − 1 = 1.
SPECTROSCOPY & MISCELLANEOUS (91–100)
91. [1H NMR] The number of 1H NMR signals in diethyl ether, CH3CH2OCH2CH3, is:
View Answer
Answer: a) 2
The molecule is symmetrical. Both CH3 groups are equivalent and both CH2 groups are equivalent. Therefore there are two proton environments.
92. [IR] A strong absorption near 1700 cm−1 is characteristic of:
View Answer
Answer: c) C=O
The carbonyl stretching vibration commonly occurs around 1650–1750 cm−1, depending on the functional group.
93. [UV-Visible] The n→π* transition of a simple saturated ketone generally occurs near:
View Answer
Answer: b) 280 nm
Carbonyl compounds commonly show a weak n→π* band in approximately the 270–300 nm region.
94. [Mass Spectrometry] The commonly observed base peak in the mass spectrum of ethanol is:
View Answer
Answer: b) m/z 31
The CH2OH+ fragment at m/z 31 is a prominent and commonly reported base peak for ethanol.
95. [1H NMR] Which compound gives a singlet near δ 2.1 ppm integrating to 6H?
View Answer
Answer: a) CH3COCH3
The two methyl groups of acetone are equivalent and have no adjacent hydrogens, so they appear as a 6H singlet near 2.1 ppm.
96. [Chromatography] In gas-liquid chromatography (GLC), the stationary phase is:
View Answer
Answer: a) A liquid stationary phase
In GLC, the mobile phase is a gas and the stationary phase is a non-volatile liquid coated on a solid support or immobilized on the column.
97. [Photochemistry] The primary photochemical event in a photosynthetic reaction centre is closely associated with:
View Answer
Answer: c)
Photoexcitation of the reaction centre leads to charge separation and initiates electron-transfer processes.
98. [Polymer Chemistry] The monomer of PTFE (Teflon) is:
View Answer
Answer: c) CF2=CF2
Tetrafluoroethylene polymerizes to form polytetrafluoroethylene: [–CF2–CF2–]ₙ.
99. [Environmental Chemistry] Which class of compounds is strongly associated with stratospheric ozone depletion?
View Answer
Answer: c) CFCs
UV radiation can release chlorine radicals from CFC-derived compounds; these radicals catalytically destroy ozone.
100. [13C NMR] How many 13C NMR signals does benzene show?
View Answer
Answer: a) 1
All six carbon atoms of benzene are chemically equivalent, so benzene gives one 13C resonance.
Study Note: For actual IIT JAM preparation, use this page as a concept-practice set. For genuine PYQs, always cross-check the exact question, year, option order and final answer against the official JAM master paper and final answer key.