1. The hybridization of the central atom in SF₄ is –
(A) sp³
(B) sp³d
(C) sp²
(D) sp³d²
Answer: (B)
Explanation: Sulfur in SF₄ forms four bonds with fluorine and has one lone pair, requiring five hybrid orbitals. This is achieved through sp³d hybridization, resulting in a seesaw shape per VSEPR theory.
2. Which gas is used in the manufacture of urea?
(A) Nitrogen
(B) Carbon dioxide
(C) Ammonia
(D) Oxygen
Answer: (C)
Explanation: Urea (NH₂CONH₂) is synthesized via the reaction of ammonia (NH₃) with carbon dioxide (CO₂) in the Bosch-Meiser process.
3. The bond angle in an ammonia molecule (NH₃) is approximately –
(A) 90°
(B) 107°
(C) 120°
(D) 180°
Answer: (B)
Explanation: Ammonia has a trigonal pyramidal shape with three bonding pairs and one lone pair on nitrogen, leading to a bond angle of ~107°, slightly less than tetrahedral (109.5°) due to lone pair repulsion.
4. The primary source of sulfur dioxide in the atmosphere is –
(A) Volcanic eruptions
(B) Photosynthesis
(C) Combustion of fossil fuels
(D) Ocean evaporation
Answer: (C)
Explanation: Sulfur dioxide (SO₂) is primarily released from burning fossil fuels containing sulfur, such as coal and oil, contributing to air pollution and acid rain.
5. Which of the following is an acidic oxide?
(A) MgO
(B) Na₂O
(C) SO₃
(D) CaO
Answer: (C)
Explanation: Acidic oxides react with water to form acids. SO₃ forms H₂SO₄ with water, making it acidic, while MgO, Na₂O, and CaO are basic oxides.
6. The rate constant of a reaction depends on –
(A) Concentration of reactants
(B) Temperature
(C) Volume of the system
(D) Pressure only
Answer: (B)
Explanation: The rate constant (k) is temperature-dependent, as described by the Arrhenius equation (k = Ae^(-Ea/RT)), and is independent of reactant concentration, volume, or pressure.
7. The element with the highest electron affinity is –
(A) Fluorine
(B) Chlorine
(C) Oxygen
(D) Nitrogen
Answer: (B)
Explanation: Electron affinity generally increases across a period. Chlorine has the highest electron affinity (3.6 eV) due to its favorable electron gain, slightly higher than fluorine (3.4 eV) due to fluorine’s small size and electron repulsion.
8. The shape of the CO₃²⁻ ion is –
(A) Linear
(B) Trigonal planar
(C) Tetrahedral
(D) Bent
Answer: (B)
Explanation: The carbonate ion (CO₃²⁻) has three bonding pairs and no lone pairs around the central carbon, resulting in a trigonal planar shape (120° bond angles).
9. The catalyst used in the hydrogenation of oils is –
(A) Platinum
(B) Nickel
(C) Iron
(D) Vanadium pentoxide
Answer: (B)
Explanation: Nickel is used as a catalyst in the hydrogenation of vegetable oils to produce solid fats (e.g., margarine) by adding hydrogen to double bonds.
10. Which of the following is a diamagnetic ion?
(A) Fe²⁺
(B) Cu²⁺
(C) Zn²⁺
(D) Mn²⁺
Answer: (C)
Explanation: Diamagnetic ions have all paired electrons. Zn²⁺ ([Ar]3d¹⁰) has a fully filled d-subshell, making it diamagnetic, while Fe²⁺, Cu²⁺, and Mn²⁺ have unpaired electrons.
11. The functional group in amines is –
(A) -NH₂
(B) -OH
(C) -COOH
(D) -CHO
Answer: (A)
Explanation: Amines are characterized by the -NH₂ (amino) group in primary amines, or substituted versions in secondary and tertiary amines.
12. The pH of a 0.1 M solution of a weak acid (Ka = 10⁻⁵) is –
(A) 1
(B) 3
(C) 5
(D) 7
Answer: (B)
Explanation: For a weak acid, [H⁺] = √(Ka × [HA]) = √(10⁻⁵ × 0.1) = √10⁻⁶ = 10⁻³ M. pH = -log(10⁻³) = 3.
13. The oxidation state of iron in Fe₃O₄ is –
(A) +2
(B) +3
(C) +2 and +3
(D) +4
Answer: (C)
Explanation: Fe₃O₄ is a mixed oxide (FeO·Fe₂O₃). One Fe is +2 (from FeO) and two Fe are +3 (from Fe₂O₃), giving an average oxidation state.
14. Which of the following is a tertiary alcohol?
(A) Ethanol
(B) Propan-2-ol
(C) 2-Methylpropan-2-ol
(D) Butan-1-ol
Answer: (C)
Explanation: A tertiary alcohol has the -OH group on a carbon bonded to three other carbons. 2-Methylpropan-2-ol ((CH₃)₃COH) is tertiary.
15. The first law of thermodynamics is a statement of –
(A) Conservation of energy
(B) Entropy increase
(C) Heat transfer
(D) Work efficiency
Answer: (A)
Explanation: The first law (ΔU = q – w) states that the internal energy change of a system equals heat added minus work done, reflecting energy conservation.
16. The metal used in storage batteries is –
(A) Copper
(B) Lead
(C) Zinc
(D) Nickel
Answer: (B)
Explanation: Lead is used in lead-acid batteries, commonly found in vehicles, due to its ability to undergo reversible redox reactions.
17. The monomer of polythene is –
(A) Ethylene
(B) Propylene
(C) Vinyl chloride
(D) Styrene
Answer: (A)
Explanation: Polythene (polyethylene) is formed by polymerizing ethylene (C₂H₄), a simple alkene.
18. The half-life of a zero-order reaction depends on –
(A) Rate constant only
(B) Initial concentration
(C) Temperature only
(D) Catalyst only
Answer: (B)
Explanation: For a zero-order reaction, t₁/₂ = [A]₀/(2k), depending on the initial concentration ([A]₀) and rate constant (k).
19. Which of the following is an amphiprotic substance?
(A) H₂SO₄
(B) HCO₃⁻
(C) NaOH
(D) HCl
Answer: (B)
Explanation: Amphiprotic substances can donate and accept protons. HCO₃⁻ acts as an acid (donates H⁺ to form CO₃²⁻) and a base (accepts H⁺ to form H₂CO₃).
20. The gas used in lasers is –
(A) Helium
(B) Neon
(C) Argon
(D) All of the above
Answer: (D)
Explanation: Helium, neon, and argon are used in gas lasers (e.g., He-Ne lasers), depending on the desired wavelength and application.
21. The coordination number of Cl⁻ in NaCl crystal is –
(A) 4
(B) 6
(C) 8
(D) 12
Answer: (B)
Explanation: In the NaCl (rock salt) structure, each Cl⁻ ion is surrounded by six Na⁺ ions, giving a coordination number of 6.
22. Which of the following is a biodegradable polymer?
(A) Nylon
(B) Polythene
(C) Polylactic acid
(D) PVC
Answer: (C)
Explanation: Polylactic acid (PLA) is a biodegradable polymer derived from renewable resources, unlike nylon, polythene, and PVC.
23. The unit of specific conductance is –
(A) Ohm·m
(B) S/m
(C) Ohm⁻¹·m⁻¹
(D) S·m²
Answer: (C)
Explanation: Specific conductance (κ) is the reciprocal of resistivity, with SI unit S/m (siemens per meter), equivalent to Ohm⁻¹·m⁻¹.
24. The compound responsible for the green flame in fireworks is –
(A) Barium chloride
(B) Strontium nitrate
(C) Copper sulfate
(D) Sodium chloride
Answer: (A)
Explanation: Barium chloride produces a green flame in fireworks due to the emission spectrum of barium ions.
25. The number of sigma bonds in ethyne (C₂H₂) is –
(A) 2
(B) 3
(C) 4
(D) 5
Answer: (B)
Explanation: Ethyne (HC≡CH) has one C≡C triple bond (1 sigma + 2 pi) and two C-H single bonds (2 sigma). Total sigma bonds = 1 + 2 = 3.
26. Which of the following is a strong electrolyte?
(A) CH₃COOH
(B) NH₃
(C) KCl
(D) HCN
Answer: (C)
Explanation: KCl is a strong electrolyte, fully dissociating into K⁺ and Cl⁻ in water. CH₃COOH, NH₃, and HCN are weak electrolytes due to partial dissociation.
27. The color of bromine liquid is –
(A) Red-brown
(B) Green
(C) Yellow
(D) Colorless
Answer: (A)
Explanation: Bromine (Br₂) is a red-brown liquid at room temperature due to its molecular electronic transitions.
28. The process of converting a solid directly to a gas is called –
(A) Evaporation
(B) Sublimation
(C) Condensation
(D) Deposition
Answer: (B)
Explanation: Sublimation is the direct transition from solid to gas without passing through the liquid phase, e.g., dry ice (CO₂).
29. The third most abundant gas in Earth’s atmosphere is –
(A) Oxygen
(B) Nitrogen
(C) Argon
(D) Carbon dioxide
Answer: (C)
Explanation: Argon (0.93%) is the third most abundant gas in Earth’s atmosphere, after nitrogen (78%) and oxygen (21%).
30. The element used in radiotherapy is –
(A) Cobalt
(B) Uranium
(C) Thorium
(D) Plutonium
Answer: (A)
Explanation: Cobalt-60 is used in radiotherapy due to its gamma radiation, effective for treating cancer.
31. The functional group in carboxylic acids is –
(A) -OH
(B) -CHO
(C) -COOH
(D) -COOR
Answer: (C)
Explanation: Carboxylic acids are characterized by the -COOH group, containing a carbonyl and hydroxyl group.
32. The rate of diffusion of a gas is proportional to –
(A) Temperature
(B) Square root of temperature
(C) Inverse of square root of molecular weight
(D) Pressure only
Answer: (C)
Explanation: Graham’s law states that the rate of diffusion is proportional to 1/√M, where M is the molecular weight.
33. Which of the following is a suspension?
(A) Milk
(B) Saltwater
(C) Muddy water
(D) Sugar syrup
Answer: (C)
Explanation: Muddy water is a suspension, with solid particles dispersed in liquid that settle over time. Milk is a colloid, while saltwater and sugar syrup are true solutions.
34. The oxidation number of phosphorus in P₂O₅ is –
(A) +3
(B) +5
(C) +4
(D) +6
Answer: (B)
Explanation: In P₂O₅, O = -2. Let P = x. Then, 2x + 5(-2) = 0 → 2x – 10 = 0 → x = +5.
35. The allotrope of phosphorus that is highly reactive is –
(A) White phosphorus
(B) Red phosphorus
(C) Black phosphorus
(D) Violet phosphorus
Answer: (A)
Explanation: White phosphorus (P₄) is highly reactive due to its strained tetrahedral structure, igniting spontaneously in air.
36. The SI unit of viscosity is –
(A) N/m²
(B) Pa·s
(C) kg/m
(D) J/s
Answer: (B)
Explanation: Viscosity is measured in pascal-seconds (Pa·s), representing the resistance to flow.
37. The compound used as a disinfectant is –
(A) Ethanol
(B) Methanol
(C) Phenol
(D) Chloroform
Answer: (C)
Explanation: Phenol (C₆H₅OH) is used as a disinfectant due to its antiseptic properties.
38. The reaction CaCO₃ → CaO + CO₂ is an example of –
(A) Combination
(B) Decomposition
(C) Displacement
(D) Double displacement
Answer: (B)
Explanation: This is a decomposition reaction, where calcium carbonate breaks down into calcium oxide and carbon dioxide upon heating.
39. The element with atomic number 12 belongs to –
(A) Alkali metals
(B) Halogens
(C) Noble gases
(D) Alkaline earth metals
Answer: (D)
Explanation: Atomic number 12 corresponds to magnesium, in group 2 (alkaline earth metals).
40. Le Chatelier’s principle applies to –
(A) Physical changes only
(B) Chemical equilibrium
(C) Nuclear reactions
(D) Phase transitions only
Answer: (B)
Explanation: Le Chatelier’s principle predicts how a system at chemical equilibrium responds to changes in concentration, pressure, or temperature.
41. The compound responsible for the smell of onions is –
(A) Allyl sulfide
(B) Propyl disulfide
(C) Ethylamine
(D) Acetic acid
Answer: (B)
Explanation: Propyl disulfide and related sulfur compounds give onions their characteristic pungent odor.
42. The crystal structure of sodium chloride is –
(A) Hexagonal
(B) Face-centered cubic
(C) Body-centered cubic
(D) Orthorhombic
Answer: (B)
Explanation: NaCl has a face-centered cubic (FCC) structure, with alternating Na⁺ and Cl⁻ ions.
43. The gas used in breathing equipment is –
(A) Nitrogen
(B) Oxygen
(C) Helium
(D) Argon
Answer: (C)
Explanation: Helium is used in breathing equipment for deep-sea diving (e.g., heliox) due to its low solubility and non-reactive nature.
44. The common name for propanoic acid is –
(A) Formic acid
(B) Acetic acid
(C) Propionic acid
(D) Butyric acid
Answer: (C)
Explanation: Propanoic acid (C₂H₅COOH) is commonly known as propionic acid, used in food preservation.
45. The phenomenon of emission of light from a substance after absorbing energy is –
(A) Fluorescence
(B) Diffraction
(C) Refraction
(D) Polarization
Answer: (A)
Explanation: Fluorescence is the emission of light by a substance after absorbing energy, typically in the visible or UV range.
46. The element used in solar cells is –
(A) Silicon
(B) Germanium
(C) Gallium
(D) All of the above
Answer: (D)
Explanation: Silicon, germanium, and gallium (e.g., in gallium arsenide) are used in solar cells for their semiconductor properties.
47. The formula of washing soda is –
(A) Na₂CO₃·10H₂O
(B) NaHCO₃
(C) Na₂SO₄
(D) NaCl
Answer: (A)
Explanation: Washing soda is sodium carbonate decahydrate (Na₂CO₃·10H₂O), used in cleaning.
48. The oxidation number of sulfur in SO₃²⁻ is –
(A) +2
(B) +4
(C) +6
(D) +3
Answer: (B)
Explanation: In SO₃²⁻, O = -2. Let S = x. Then, x + 3(-2) = -2 → x – 6 = -2 → x = +4.
49. Which of the following is a redox indicator?
(A) Phenolphthalein
(B) Methyl orange
(C) Methylene blue
(D) Litmus
Answer: (C)
Explanation: Methylene blue changes color based on oxidation state, making it a redox indicator, unlike pH indicators like phenolphthalein, methyl orange, or litmus.
50. The IUPAC name of CH₃COCH₃ is –
(A) Propanone
(B) Ethanone
(C) Methanone
(D) Butanone
Answer: (A)
Explanation: CH₃COCH₃ has three carbon atoms and a ketone group, so its IUPAC name is propanone.