1. The hybridization of the central atom in PCl₅ is –
(A) sp³
(B) sp³d
(C) sp²
(D) dsp²
Answer: (B)
Explanation: Phosphorus in PCl₅ forms five bonds with chlorine atoms, requiring five hybrid orbitals. This is achieved through sp³d hybridization, involving one s, three p, and one d orbital, resulting in a trigonal bipyramidal shape.
2. Which gas is used in the manufacture of dynamite?
(A) Nitrous oxide
(B) Nitric oxide
(C) Glycerol
(D) Nitroglycerin
Answer: (D)
Explanation: Nitroglycerin, a highly explosive compound, is the key ingredient in dynamite. It is synthesized by nitrating glycerol with nitric acid.
3. The bond angle in a water molecule (H₂O) is approximately –
(A) 180°
(B) 120°
(C) 104.5°
(D) 109.5°
Answer: (C)
Explanation: Water has a bent shape due to two bonding pairs and two lone pairs on oxygen, leading to a bond angle of ~104.5°, as per VSEPR theory, slightly less than the tetrahedral angle (109.5°) due to lone pair repulsion.
4. The main source of helium on Earth is –
(A) Sunlight
(B) Radioactive decay
(C) Volcanic activity
(D) Photosynthesis
Answer: (B)
Explanation: Helium is primarily produced by the alpha decay of radioactive elements like uranium and thorium in Earth’s crust, where alpha particles (He²⁺) gain electrons to form helium gas.
5. Which of the following is a neutral oxide?
(A) CO₂
(B) NO
(C) SO₂
(D) P₂O₅
Answer: (B)
Explanation: Neutral oxides do not react with water to form acids or bases. Nitric oxide (NO) is neutral, while CO₂, SO₂, and P₂O₅ form acidic solutions with water.
6. The rate of a second-order reaction depends on –
(A) [Reactant]
(B) [Reactant]²
(C) [Catalyst]
(D) Temperature only
Answer: (B)
Explanation: For a second-order reaction, the rate law is rate = k[A]² or k[A][B], so the rate depends on the square of the reactant concentration or the product of two reactant concentrations.
7. The element with the lowest electronegativity is –
(A) Cesium
(B) Fluorine
(C) Sodium
(D) Lithium
Answer: (A)
Explanation: Electronegativity decreases down a group and increases across a period. Cesium, in the bottom-left corner of the periodic table, has the lowest electronegativity.
8. The shape of the NH₄⁺ ion is –
(A) Trigonal planar
(B) Tetrahedral
(C) Linear
(D) Square planar
Answer: (B)
Explanation: The ammonium ion (NH₄⁺) has four bonding pairs and no lone pairs around nitrogen, resulting in a tetrahedral shape, as predicted by VSEPR theory.
9. The catalyst used in the Ostwald process for nitric acid production is –
(A) Platinum
(B) Iron
(C) Vanadium pentoxide
(D) Nickel
Answer: (A)
Explanation: The Ostwald process (4NH₃ + 5O₂ → 4NO + 6H₂O) uses platinum as a catalyst to oxidize ammonia to nitric oxide, a key step in nitric acid production.
10. Which of the following is a paramagnetic substance?
(A) Zn
(B) N₂
(C) O₂
(D) Ne
Answer: (C)
Explanation: Paramagnetic substances have unpaired electrons. O₂ has two unpaired electrons in its π*2p orbitals, making it paramagnetic. Zn, N₂, and Ne have all paired electrons.
11. The functional group in ethers is –
(A) -OH
(B) -CHO
(C) -O-
(D) -COOH
Answer: (C)
Explanation: Ethers are characterized by an oxygen atom bonded to two alkyl or aryl groups (R-O-R’).
12. The pH of a 0.001 M NaOH solution is –
(A) 3
(B) 7
(C) 11
(D) 14
Answer: (C)
Explanation: NaOH is a strong base, fully dissociating. [OH⁻] = 0.001 M = 10⁻³ M. pOH = -log(10⁻³) = 3. pH = 14 – pOH = 14 – 3 = 11.
13. The common oxidation state of actinides is –
(A) +2
(B) +3
(C) +4
(D) +5
Answer: (B)
Explanation: Actinides typically exhibit a +3 oxidation state, similar to lanthanides, due to the loss of electrons from 7s and 6d or 5f orbitals.
14. Which of the following is a secondary alcohol?
(A) Methanol
(B) Ethanol
(C) Propan-2-ol
(D) Butan-1-ol
Answer: (C)
Explanation: A secondary alcohol has the -OH group attached to a carbon bonded to two other carbons. Propan-2-ol (CH₃CHOHCH₃) is a secondary alcohol.
15. The second law of thermodynamics states that –
(A) Energy is conserved
(B) Entropy of an isolated system increases
(C) Heat flows from hot to cold
(D) Work equals heat
Answer: (B)
Explanation: The second law states that the entropy of an isolated system increases in spontaneous processes, reflecting the tendency toward disorder.
16. The metal used in aircraft manufacturing is –
(A) Iron
(B) Aluminum
(C) Copper
(D) Zinc
Answer: (B)
Explanation: Aluminum is widely used in aircraft due to its low density, high strength, and corrosion resistance.
17. The monomer of polystyrene is –
(A) Ethylene
(B) Vinyl chloride
(C) Styrene
(D) Propylene
Answer: (C)
Explanation: Polystyrene is formed by polymerizing styrene (C₆H₅CH=CH₂), an aromatic alkene.
18. The half-life of a second-order reaction depends on –
(A) Initial concentration
(B) Rate constant only
(C) Temperature only
(D) Catalyst only
Answer: (A)
Explanation: For a second-order reaction, the half-life is t₁/₂ = 1/(k[A]₀), which depends on the initial concentration ([A]₀) and the rate constant (k).
19. Which of the following is a basic oxide?
(A) SO₂
(B) CO₂
(C) Na₂O
(D) P₂O₅
Answer: (C)
Explanation: Basic oxides react with acids to form salts and water. Na₂O reacts with water to form NaOH, a strong base, making it a basic oxide.
20. The gas used in advertising signs is –
(A) Helium
(B) Neon
(C) Argon
(D) Krypton
Answer: (B)
Explanation: Neon is used in neon signs due to its bright red-orange glow when electrified.
21. The coordination number of Cs⁺ in CsCl crystal is –
(A) 4
(B) 6
(C) 8
(D) 12
Answer: (C)
Explanation: CsCl has a body-centered cubic structure, where each Cs⁺ ion is surrounded by eight Cl⁻ ions, giving a coordination number of 8.
22. Which of the following is a synthetic polymer?
(A) Cellulose
(B) Starch
(C) Nylon
(D) Proteins
Answer: (C)
Explanation: Nylon is a synthetic polyamide, while cellulose, starch, and proteins are natural polymers.
23. The unit of equilibrium constant for a gaseous reaction (Kₚ) is –
(A) mol L⁻¹
(B) atm
(C) Dimensionless
(D) Depends on reaction
Answer: (D)
Explanation: The unit of Kₚ depends on the stoichiometry of the reaction, as it is expressed in terms of partial pressures (atm). For Δn = 0, Kₚ is dimensionless; otherwise, it has units like atm^Δn.
24. The compound responsible for the blue color of copper sulfate is –
(A) Cu²⁺
(B) SO₄²⁻
(C) H₂O
(D) CuSO₄
Answer: (A)
Explanation: The blue color of hydrated copper sulfate (CuSO₄·5H₂O) is due to the Cu²⁺ ion’s d-d electron transitions in the presence of water ligands.
25. The number of pi bonds in benzene (C₆H₆) is –
(A) 3
(B) 4
(C) 5
(D) 6
Answer: (A)
Explanation: Benzene has a ring structure with three alternating double bonds, each contributing one pi bond, for a total of three pi bonds.
26. Which of the following is a weak acid?
(A) HCl
(B) HNO₃
(C) CH₃COOH
(D) H₂SO₄
Answer: (C)
Explanation: Acetic acid (CH₃COOH) is a weak acid, as it partially dissociates in water, unlike strong acids like HCl, HNO₃, and H₂SO₄.
27. The color of iodine vapor is –
(A) Yellow
(B) Violet
(C) Green
(D) Red
Answer: (B)
Explanation: Iodine vapor has a characteristic violet color due to electronic transitions in the I₂ molecule.
28. The process of converting a liquid to a gas is called –
(A) Sublimation
(B) Evaporation
(C) Condensation
(D) Deposition
Answer: (B)
Explanation: Evaporation is the phase transition from liquid to gas at the surface of a liquid, typically below its boiling point.
29. The second most abundant element in Earth’s atmosphere is –
(A) Nitrogen
(B) Oxygen
(C) Argon
(D) Carbon dioxide
Answer: (B)
Explanation: Oxygen (O₂) constitutes about 21% of Earth’s atmosphere, making it the second most abundant gas after nitrogen (78%).
30. The element used in control rods of nuclear reactors is –
(A) Graphite
(B) Boron
(C) Uranium
(D) Sodium
Answer: (B)
Explanation: Boron, often as boron carbide, is used in control rods to absorb neutrons and regulate nuclear fission.
31. The functional group in esters is –
(A) -COOH
(B) -CHO
(C) -COOR
(D) -OH
Answer: (C)
Explanation: Esters have the functional group -COOR, where the carbon is double-bonded to oxygen and single-bonded to an alkoxy group.
32. The rate of effusion of a gas is proportional to –
(A) Molecular weight
(B) Square root of molecular weight
(C) Inverse of square root of molecular weight
(D) Temperature only
Answer: (C)
Explanation: Graham’s law states that the rate of effusion is proportional to 1/√M, where M is the molecular weight of the gas.
33. Which of the following is a true solution?
(A) Milk
(B) Sugar syrup
(C) Fog
(D) Smoke
Answer: (B)
Explanation: Sugar syrup is a true solution, with sugar molecules homogeneously dissolved in water. Milk, fog, and smoke are colloids or suspensions.
34. The oxidation number of chlorine in ClO₄⁻ is –
(A) +1
(B) +3
(C) +5
(D) +7
Answer: (D)
Explanation: In ClO₄⁻, O = -2. Let Cl = x. Then, x + 4(-2) = -1 → x – 8 = -1 → x = +7.
35. The allotrope of carbon used in cutting tools is –
(A) Graphite
(B) Diamond
(C) Fullerene
(D) Charcoal
Answer: (B)
Explanation: Diamond, with its tetrahedral covalent structure, is extremely hard and used in cutting tools.
36. The SI unit of surface tension is –
(A) N/m
(B) J/m²
(C) N·m
(D) kg/m²
Answer: (A)
Explanation: Surface tension is force per unit length, with SI unit N/m.
37. The compound used as an anesthetic is –
(A) CHCl₃
(B) CCl₄
(C) CH₃OH
(D) C₂H₅OH
Answer: (A)
Explanation: Chloroform (CHCl₃) was historically used as an anesthetic due to its sedative properties.
38. The reaction 2Na + Cl₂ → 2NaCl is an example of –
(A) Decomposition
(B) Combination
(C) Displacement
(D) Double displacement
Answer: (B)
Explanation: This is a combination reaction, where two elements (Na and Cl₂) combine to form a single compound (NaCl).
39. The element with atomic number 19 belongs to –
(A) Halogens
(B) Alkali metals
(C) Noble gases
(D) Alkaline earth metals
Answer: (B)
Explanation: Atomic number 19 corresponds to potassium, in group 1 (alkali metals).
40. The common ion effect reduces the –
(A) Solubility of a salt
(B) pH of a solution
(C) Rate of reaction
(D) Boiling point
Answer: (A)
Explanation: The common ion effect decreases the solubility of a sparingly soluble salt by shifting the dissolution equilibrium (Le Chatelier’s principle).
41. The smell of garlic is due to –
(A) Allyl sulfide
(B) Ethyl chloride
(C) Methylamine
(D) Acetic acid
Answer: (A)
Explanation: Allyl sulfide compounds, such as diallyl disulfide, give garlic its characteristic odor.
42. The crystal structure of graphite is –
(A) Tetrahedral
(B) Hexagonal
(C) Cubic
(D) Orthorhombic
Answer: (B)
Explanation: Graphite has a layered, hexagonal crystal structure with strong covalent bonds within layers and weak van der Waals forces between them.
43. The gas used in airships historically was –
(A) Helium
(B) Hydrogen
(C) Nitrogen
(D) Argon
Answer: (B)
Explanation: Hydrogen was used in early airships due to its low density, but its flammability led to the use of safer helium.
44. The common name for methanoic acid is –
(A) Acetic acid
(B) Formic acid
(C) Propionic acid
(D) Butyric acid
Answer: (B)
Explanation: Methanoic acid (HCOOH) is commonly known as formic acid, found in ant stings.
45. The phenomenon of splitting of light into colors is called –
(A) Diffraction
(B) Dispersion
(C) Polarization
(D) Interference
Answer: (B)
Explanation: Dispersion is the separation of white light into its constituent colors due to varying refractive indices, as seen in a prism.
46. The element used in smoke detectors is –
(A) Uranium
(B) Americium
(C) Plutonium
(D) Thorium
Answer: (B)
Explanation: Americium-241, a radioactive element, is used in smoke detectors to ionize air and detect smoke particles.
47. The formula of plaster of Paris is –
(A) CaSO₄·2H₂O
(B) CaSO₄·½H₂O
(C) CaSO₄
(D) CaCO₃
Answer: (B)
Explanation: Plaster of Paris is calcium sulfate hemihydrate (CaSO₄·½H₂O), used in casts and construction.
48. The oxidation number of nitrogen in N₂O is –
(A) +1
(B) +2
(C) -1
(D) 0
Answer: (A)
Explanation: In N₂O, O = -2. Let N = x. Then, 2x + (-2) = 0 → 2x = 2 → x = +1.
49. Which of the following is not a buffer solution?
(A) NH₄Cl + NH₃
(B) CH₃COOH + CH₃COONa
(C) HCl + NaCl
(D) HCOOH + HCOONa
Answer: (C)
Explanation: A buffer requires a weak acid/base and its conjugate. HCl + NaCl contains a strong acid, so it’s not a buffer.
50. The IUPAC name of CH₃CHO is –
(A) Methanal
(B) Ethanal
(C) Propanal
(D) Butanal
Answer: (B)
Explanation: CH₃CHO has two carbon atoms and an aldehyde group, so its IUPAC name is ethanal.