1. The hybridization of nitrogen in NH₃ is –
(A) sp
(B) sp²
(C) sp³
(D) dsp²
Answer: (C)
Explanation: Nitrogen in NH₃ has three bonding pairs and one lone pair, requiring four hybrid orbitals. This results in sp³ hybridization, forming a tetrahedral electron geometry and a trigonal pyramidal molecular shape.
2. Which gas is responsible for the depletion of the ozone layer?
(A) CO₂
(B) CFCs
(C) SO₂
(D) N₂O
Answer: (B)
Explanation: Chlorofluorocarbons (CFCs) release chlorine atoms in the stratosphere, which catalyze the breakdown of ozone (O₃) into O₂, depleting the ozone layer.
3. The bond order of O₂⁺ is –
(A) 1
(B) 1.5
(C) 2
(D) 2.5
Answer: (D)
Explanation: Using molecular orbital theory, O₂ has 12 valence electrons, and O₂⁺ has 11. The bond order is calculated as (8 bonding electrons – 3 antibonding electrons)/2 = 2.5.
4. Which of the following is a Lewis acid?
(A) NH₃
(B) BF₃
(C) H₂O
(D) OH⁻
Answer: (B)
Explanation: A Lewis acid accepts an electron pair. BF₃ has an incomplete octet and can accept a lone pair, making it a Lewis acid. NH₃, H₂O, and OH⁻ are Lewis bases due to their lone pairs.
5. The primary constituent of natural gas is –
(A) Ethane
(B) Methane
(C) Propane
(D) Butane
Answer: (B)
Explanation: Natural gas is primarily composed of methane (CH₄), typically 70–90%, with smaller amounts of ethane, propane, and butane.
6. The unit of rate constant for a zero-order reaction is –
(A) s⁻¹
(B) mol L⁻¹ s⁻¹
(C) L mol⁻¹ s⁻¹
(D) mol⁻¹ L s⁻¹
Answer: (B)
Explanation: For a zero-order reaction, the rate law is rate = k, so the unit of k is the same as the rate, which is mol L⁻¹ s⁻¹.
7. Which element has the highest ionization energy?
(A) Nitrogen
(B) Oxygen
(C) Fluorine
(D) Helium
Answer: (D)
Explanation: Ionization energy increases across a period and decreases down a group. Helium, being in the top-right corner of the periodic table, has the highest ionization energy.
8. The shape of the XeF₄ molecule is –
(A) Tetrahedral
(B) Square planar
(C) Trigonal bipyramidal
(D) Octahedral
Answer: (B)
Explanation: XeF₄ has four bonding pairs and two lone pairs around xenon. According to VSEPR theory, this results in a square planar molecular shape.
9. The catalyst used in the contact process for sulfuric acid production is –
(A) Iron
(B) Vanadium pentoxide
(C) Platinum
(D) Nickel
Answer: (B)
Explanation: The contact process (2SO₂ + O₂ → 2SO₃) uses vanadium pentoxide (V₂O₅) as a catalyst to oxidize SO₂ to SO₃, which is then converted to H₂SO₄.
10. Which of the following is a diamagnetic substance?
(A) O₂
(B) NO
(C) N₂
(D) Fe
Answer: (C)
Explanation: Diamagnetic substances have all paired electrons. N₂ has a triple bond with all electrons paired (bond order 3), making it diamagnetic. O₂ and NO have unpaired electrons, and Fe is ferromagnetic.
11. The functional group in aldehydes is –
(A) -OH
(B) -CHO
(C) -COOH
(D) -NH₂
Answer: (B)
Explanation: Aldehydes are characterized by the -CHO (formyl) group, where the carbon is bonded to a hydrogen and a double-bonded oxygen.
12. The pH of a 0.01 M HCl solution is –
(A) 1
(B) 2
(C) 3
(D) 4
Answer: (B)
Explanation: HCl is a strong acid that fully dissociates. [H⁺] = 0.01 M = 10⁻² M. pH = -log[H⁺] = -log(10⁻²) = 2.
13. The common oxidation state of lanthanides is –
(A) +1
(B) +2
(C) +3
(D) +4
Answer: (C)
Explanation: Lanthanides typically exhibit a +3 oxidation state due to the loss of two 6s and one 5d or 4f electron, achieving a stable configuration.
14. Which of the following is a primary alcohol?
(A) Propan-2-ol
(B) Ethanol
(C) 2-Methylpropan-2-ol
(D) Butan-2-ol
Answer: (B)
Explanation: A primary alcohol has the -OH group attached to a carbon bonded to only one other carbon. Ethanol (CH₃CH₂OH) is a primary alcohol, while the others are secondary or tertiary.
15. The entropy of a system increases in –
(A) Reversible processes
(B) Irreversible processes
(C) Both (A) and (B)
(D) Neither (A) nor (B)
Answer: (C)
Explanation: Entropy, a measure of disorder, increases in spontaneous (irreversible) processes and can increase in reversible processes if heat is absorbed, per the second law of thermodynamics.
16. Which metal is used in galvanization?
(A) Copper
(B) Zinc
(C) Iron
(D) Aluminum
Answer: (B)
Explanation: Galvanization involves coating iron or steel with zinc to prevent corrosion, as zinc is more reactive and sacrificially corrodes.
17. The monomer of PVC is –
(A) Ethylene
(B) Vinyl chloride
(C) Styrene
(D) Propylene
Answer: (B)
Explanation: Polyvinyl chloride (PVC) is formed by polymerizing vinyl chloride (CH₂=CHCl), which contains a chlorine atom on the ethene backbone.
18. The half-life of a first-order reaction is independent of –
(A) Temperature
(B) Catalyst
(C) Initial concentration
(D) Rate constant
Answer: (C)
Explanation: For a first-order reaction, the half-life is given by t₁/₂ = ln(2)/k, which depends on the rate constant (k) but not on the initial concentration.
19. Which of the following is an amphoteric oxide?
(A) Na₂O
(B) Al₂O₃
(C) SO₂
(D) CO₂
Answer: (B)
Explanation: Amphoteric oxides react with both acids and bases. Al₂O₃ reacts with HCl to form AlCl₃ and with NaOH to form NaAlO₂, making it amphoteric.
20. The gas used in welding is –
(A) Oxygen
(B) Acetylene
(C) Nitrogen
(D) Hydrogen
Answer: (B)
Explanation: Acetylene (C₂H₂) is used in oxy-acetylene welding due to its high flame temperature when burned with oxygen.
21. The coordination number of Na⁺ in NaCl crystal is –
(A) 4
(B) 6
(C) 8
(D) 12
Answer: (B)
Explanation: NaCl has a face-centered cubic (FCC) structure where each Na⁺ ion is surrounded by six Cl⁻ ions, giving a coordination number of 6.
22. Which of the following is a natural polymer?
(A) Nylon
(B) Cellulose
(C) Teflon
(D) Polyethylene
Answer: (B)
Explanation: Cellulose, found in plant cell walls, is a natural polysaccharide. Nylon, Teflon, and polyethylene are synthetic polymers.
23. The standard electrode potential is measured in –
(A) Volts
(B) Amperes
(C) Joules
(D) Ohms
Answer: (A)
Explanation: Standard electrode potential, a measure of a half-cell’s tendency to gain or lose electrons, is expressed in volts (V).
24. The compound responsible for the smell of rain is –
(A) Geosmin
(B) Ozone
(C) Ethanol
(D) Formaldehyde
Answer: (A)
Explanation: Geosmin, produced by soil bacteria like actinomycetes, gives the characteristic earthy smell after rain.
25. The number of sigma bonds in ethene (C₂H₄) is –
(A) 4
(B) 5
(C) 6
(D) 7
Answer: (B)
Explanation: Ethene (C₂H₄) has one C=C double bond (1 sigma + 1 pi) and four C-H single bonds (4 sigma). Total sigma bonds = 1 + 4 = 5.
26. Which of the following is a strong base?
(A) NH₃
(B) NaOH
(C) Ca(OH)₂
(D) Mg(OH)₂
Answer: (B)
Explanation: NaOH is a strong base as it completely dissociates in water to form OH⁻ ions. NH₃, Ca(OH)₂, and Mg(OH)₂ are weaker due to partial dissociation or lower solubility.
27. The color of KMnO₄ is due to –
(A) d-d transition
(B) Charge transfer
(C) f-f transition
(D) Spin transition
Answer: (B)
Explanation: The purple color of KMnO₄ arises from ligand-to-metal charge transfer, where electrons are excited from oxygen ligands to the manganese center.
28. The process of converting a gas directly to a solid is called –
(A) Sublimation
(B) Deposition
(C) Condensation
(D) Evaporation
Answer: (B)
Explanation: Deposition is the phase transition from gas to solid without passing through the liquid phase, e.g., frost formation.
29. The most abundant gas in the Earth’s atmosphere is –
(A) Oxygen
(B) Nitrogen
(C) Carbon dioxide
(D) Argon
Answer: (B)
Explanation: Nitrogen (N₂) constitutes about 78% of Earth’s atmosphere, followed by oxygen (21%), argon (0.93%), and carbon dioxide (0.0407%).
30. The element used in nuclear reactors as a moderator is –
(A) Graphite
(B) Iron
(C) Uranium
(D) Sodium
Answer: (A)
Explanation: Graphite is used as a moderator in nuclear reactors to slow down neutrons, enhancing the efficiency of nuclear fission.
31. The functional group in ketones is –
(A) -OH
(B) -CHO
(C) -CO-
(D) -COOH
Answer: (C)
Explanation: Ketones contain the carbonyl group (-CO-), where the carbon is bonded to two alkyl groups.
32. The rate of diffusion of a gas is inversely proportional to –
(A) Temperature
(B) Pressure
(C) Square root of its molecular weight
(D) Volume
Answer: (C)
Explanation: According to Graham’s law, the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight (r ∝ 1/√M).
33. Which of the following is an example of a colloidal solution?
(A) Saltwater
(B) Milk
(C) Sugar syrup
(D) Vinegar
Answer: (B)
Explanation: Milk is a colloid, with fat globules dispersed in water. Saltwater, sugar syrup, and vinegar are true solutions, not colloids.
34. The oxidation number of sulfur in H₂SO₄ is –
(A) +2
(B) +4
(C) +6
(D) +8
Answer: (C)
Explanation: In H₂SO₄, H = +1, O = -2. Let S = x. Then, 2(+1) + x + 4(-2) = 0 → 2 + x – 8 = 0 → x = +6.
35. The allotrope of carbon used in lubricants is –
(A) Diamond
(B) Graphite
(C) Fullerene
(D) Amorphous carbon
Answer: (B)
Explanation: Graphite has a layered structure with weak van der Waals forces between layers, allowing it to slide easily and act as a lubricant.
36. The SI unit of dipole moment is –
(A) Coulomb
(B) Debye
(C) Ampere-meter
(D) Joule
Answer: (B)
Explanation: Dipole moment is measured in Debye (D), where 1 D = 3.33564 × 10⁻³⁰ C·m in SI units.
37. The compound used as a refrigerant is –
(A) NH₃
(B) CHCl₃
(C) CCl₂F₂
(D) CH₃OH
Answer: (C)
Explanation: Dichlorodifluoromethane (CCl₂F₂), a CFC, was historically used as a refrigerant (Freon-12) due to its low boiling point.
38. The reaction 2H₂O₂ → 2H₂O + O₂ is an example of –
(A) Combination
(B) Decomposition
(C) Displacement
(D) Double displacement
Answer: (B)
Explanation: The breakdown of H₂O₂ into H₂O and O₂ is a decomposition reaction, where a single compound splits into two or more products.
39. The element with atomic number 17 belongs to –
(A) Alkali metals
(B) Halogens
(C) Noble gases
(D) Alkaline earth metals
Answer: (B)
Explanation: Atomic number 17 corresponds to chlorine, which is in group 17 (halogens) of the periodic table.
40. The solubility product (Ksp) is related to –
(A) Acids
(B) Bases
(C) Sparingly soluble salts
(D) Gases
Answer: (C)
Explanation: Ksp is the equilibrium constant for the dissolution of sparingly soluble salts, indicating the extent of solubility in water.
41. The smell of rancid butter is due to –
(A) Acetic acid
(B) Butyric acid
(C) Lactic acid
(D) Citric acid
Answer: (B)
Explanation: Rancid butter’s odor comes from butyric acid, formed by the hydrolysis of butterfat triglycerides.
42. The crystal structure of diamond is –
(A) Body-centered cubic
(B) Face-centered cubic
(C) Tetrahedral
(D) Hexagonal
Answer: (C)
Explanation: Diamond has a tetrahedral crystal structure, where each carbon atom is covalently bonded to four others in a 3D network.
43. The gas used in balloons is –
(A) Hydrogen
(B) Helium
(C) Nitrogen
(D) Oxygen
Answer: (B)
Explanation: Helium, a light and inert gas, is used in balloons due to its low density and non-flammable nature.
44. The common name for ethanoic acid is –
(A) Formic acid
(B) Acetic acid
(C) Propionic acid
(D) Butyric acid
Answer: (B)
Explanation: Ethanoic acid (CH₃COOH) is commonly known as acetic acid, found in vinegar.
45. The phenomenon of bending of light around obstacles is called –
(A) Reflection
(B) Refraction
(C) Diffraction
(D) Polarization
Answer: (C)
Explanation: Diffraction is the bending of light waves around the edges of obstacles or through narrow openings, a wave property.
46. The element used in photoelectric cells is –
(A) Sodium
(B) Cesium
(C) Magnesium
(D) Iron
Answer: (B)
Explanation: Cesium has a low ionization energy, making it ideal for photoelectric cells, where it emits electrons when exposed to light.
47. The formula of gypsum is –
(A) CaSO₄·2H₂O
(B) CaSO₄·H₂O
(C) CaSO₄
(D) CaCO₃
Answer: (A)
Explanation: Gypsum is calcium sulfate dihydrate (CaSO₄·2H₂O), used in plaster and drywall.
48. The oxidation number of carbon in CH₂O is –
(A) 0
(B) +2
(C) -2
(D) +4
Answer: (A)
Explanation: In CH₂O, H = +1, O = -2. Let C = x. Then, x + 2(+1) + (-2) = 0 → x + 2 – 2 = 0 → x = 0.
49. Which of the following is a buffer solution?
(A) NaCl + H₂O
(B) CH₃COOH + CH₃COONa
(C) HCl + NaOH
(D) H₂SO₄ + Na₂SO₄
Answer: (B)
Explanation: A buffer solution resists pH changes and consists of a weak acid and its conjugate base. CH₃COOH (acetic acid) and CH₃COONa (sodium acetate) form a buffer.
50. The IUPAC name of CH₃CH₂OH is –
(A) Methanol
(B) Ethanol
(C) Propanol
(D) Butanol
Answer: (B)
Explanation: CH₃CH₂OH has two carbon atoms, and the IUPAC name for a two-carbon alcohol is ethanol.