1. A chemical reaction involves:
A) Breaking and forming of bonds
B) Only breaking of bonds
C) Only forming of bonds
D) Change in physical state only
Answer: A
Explanation: Chemical reactions occur by breaking old bonds and forming new ones.
2. Which of the following is not a chemical reaction?
A) Rusting of iron
B) Burning of paper
C) Melting of ice
D) Respiration
Answer: C
Explanation: Melting of ice is a physical change, not a chemical reaction.
3. Which of the following is a chemical reaction?
A) Dissolving sugar in water
B) Lighting a candle
C) Boiling water
D) Cutting paper
Answer: B
Explanation: Lighting a candle involves combustion → chemical reaction.
4. Which of the following represents a decomposition reaction?
A) 2H₂ + O₂ → 2H₂O
B) CaCO₃ → CaO + CO₂
C) Zn + H₂SO₄ → ZnSO₄ + H₂
D) NaOH + HCl → NaCl + H₂O
Answer: B
Explanation: CaCO₃ breaks into CaO and CO₂ → decomposition.
5. A reaction in which heat is released is called:
A) Endothermic reaction
B) Exothermic reaction
C) Photochemical reaction
D) Catalytic reaction
Answer: B
Explanation: Exothermic reactions release heat energy (e.g., combustion).
6. Which of the following is an endothermic reaction?
A) Combustion of coal
B) Respiration
C) Photosynthesis
D) Neutralization
Answer: C
Explanation: Photosynthesis absorbs sunlight → endothermic.
7. Which reaction is used in black and white photography?
A) Decomposition of AgBr
B) Combination of H₂ + O₂
C) Neutralization of acid and base
D) Combustion of methane
Answer: A
Explanation: Light decomposes AgBr → Ag + Br₂ (photochemical reaction).
8. Rusting of iron is an example of:
A) Oxidation
B) Reduction
C) Neutralization
D) Precipitation
Answer: A
Explanation: Iron reacts with oxygen and moisture → Fe₂O₃·xH₂O (rust).
9. The reaction between acid and base is called:
A) Combustion
B) Neutralization
C) Reduction
D) Precipitation
Answer: B
Explanation: Acid + Base → Salt + Water = neutralization.
10. Which of the following is a redox reaction?
A) Zn + CuSO₄ → ZnSO₄ + Cu
B) HCl + NaOH → NaCl + H₂O
C) AgNO₃ + NaCl → AgCl + NaNO₃
D) CaCO₃ → CaO + CO₂
Answer: A
Explanation: Zn oxidized, Cu²⁺ reduced → redox.
11. Which of the following is a combination reaction?
A) 2H₂ + O₂ → 2H₂O
B) CaCO₃ → CaO + CO₂
C) Zn + H₂SO₄ → ZnSO₄ + H₂
D) AgNO₃ + NaCl → AgCl + NaNO₃
Answer: A
Explanation: Two elements combine → water.
12. Which of the following is a displacement reaction?
A) 2H₂ + O₂ → 2H₂O
B) CuSO₄ + Zn → ZnSO₄ + Cu
C) HCl + NaOH → NaCl + H₂O
D) CaCO₃ → CaO + CO₂
Answer: B
Explanation: Zn displaces Cu from CuSO₄.
13. Which of the following is an example of precipitation reaction?
A) AgNO₃ + NaCl → AgCl + NaNO₃
B) HCl + NaOH → NaCl + H₂O
C) 2H₂ + O₂ → 2H₂O
D) CaCO₃ → CaO + CO₂
Answer: A
Explanation: AgCl precipitate forms.
14. A reaction that proceeds with the help of sunlight is called:
A) Thermal reaction
B) Photochemical reaction
C) Electrochemical reaction
D) Catalytic reaction
Answer: B
Explanation: Example: Photosynthesis, decomposition of AgCl in sunlight.
15. The reaction in which an element replaces another in a compound is called:
A) Combination
B) Double displacement
C) Single displacement
D) Decomposition
Answer: C
Explanation: One element replaces another → single displacement.
16. The process of respiration is:
A) Endothermic
B) Exothermic
C) Neutralization
D) Photochemical
Answer: B
Explanation: Respiration releases energy → exothermic.
17. Which of the following is an example of double displacement reaction?
A) Zn + CuSO₄ → ZnSO₄ + Cu
B) Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
C) 2H₂ + O₂ → 2H₂O
D) CaCO₃ → CaO + CO₂
Answer: B
Explanation: Exchange of ions between two compounds.
18. The burning of methane is an example of:
A) Combination
B) Decomposition
C) Neutralization
D) Combustion
Answer: D
Explanation: CH₄ + O₂ → CO₂ + H₂O + heat.
19. Which is not a type of chemical reaction?
A) Combination
B) Decomposition
C) Displacement
D) Rotation
Answer: D
Explanation: Rotation is a physical process.
20. Respiration is essentially the reverse of:
A) Combustion
B) Photosynthesis
C) Electrolysis
D) Oxidation
Answer: B
Explanation: Photosynthesis stores energy, respiration releases it.
21. Which of the following reactions is endothermic?
A) Evaporation of water
B) Photosynthesis
C) Thermal decomposition of CaCO₃
D) All of the above
Answer: D
Explanation: All absorb energy.
22. Which of the following is not a characteristic of a chemical reaction?
A) Evolution of gas
B) Change in temperature
C) Formation of precipitate
D) Change in shape only
Answer: D
Explanation: Change in shape is a physical change.
23. The energy required to start a chemical reaction is called:
A) Bond energy
B) Lattice energy
C) Activation energy
D) Ionization energy
Answer: C
Explanation: Activation energy initiates reaction.
24. Which gas is evolved when Zn reacts with dilute H₂SO₄?
A) CO₂
B) H₂
C) SO₂
D) O₂
Answer: B
Explanation: Zn + H₂SO₄ → ZnSO₄ + H₂.
25. When CaO is added to water, the reaction is:
A) Endothermic
B) Exothermic
C) Neutralization
D) Decomposition
Answer: B
Explanation: CaO + H₂O → Ca(OH)₂ + heat (slaking of lime).
26. The law used in balancing chemical equations is:
A) Law of definite proportion
B) Law of conservation of mass
C) Law of multiple proportion
D) Law of constant energy
Answer: B
Explanation: During reactions, total mass of reactants = mass of products.
27. The balanced form of: H₂ + O₂ → H₂O is:
A) H₂ + O₂ → H₂O
B) 2H₂ + O₂ → 2H₂O
C) H₂ + 2O₂ → 2H₂O
D) 2H₂ + 2O₂ → H₂O₂
Answer: B
Explanation: 2 molecules of H₂ combine with 1 of O₂ → 2H₂O.
28. In the reaction: Zn + CuSO₄ → ZnSO₄ + Cu, the oxidizing agent is:
A) Zn
B) CuSO₄
C) Cu
D) SO₄²⁻
Answer: B
Explanation: Cu²⁺ ions in CuSO₄ oxidize Zn to Zn²⁺.
29. Oxidation means:
A) Loss of electrons
B) Gain of electrons
C) Gain of protons
D) Loss of neutrons
Answer: A
Explanation: Oxidation = loss of electrons, Reduction = gain of electrons.
30. Reduction means:
A) Loss of electrons
B) Gain of electrons
C) Loss of protons
D) Increase in oxidation number
Answer: B
Explanation: Reduction = gain of electrons (decrease in oxidation number).
31. Which is a redox reaction?
A) Zn + 2HCl → ZnCl₂ + H₂
B) HCl + NaOH → NaCl + H₂O
C) AgNO₃ + NaCl → AgCl + NaNO₃
D) CaCO₃ → CaO + CO₂
Answer: A
Explanation: Zn oxidized, H⁺ reduced → redox.
32. Which of the following reactions is not a redox reaction?
A) NaOH + HCl → NaCl + H₂O
B) 2Mg + O₂ → 2MgO
C) Fe₂O₃ + 3CO → 2Fe + 3CO₂
D) Zn + CuSO₄ → ZnSO₄ + Cu
Answer: A
Explanation: Neutralization has no change in oxidation state.
33. In the reaction: Fe₂O₃ + 3CO → 2Fe + 3CO₂, the reducing agent is:
A) Fe₂O₃
B) CO
C) Fe
D) CO₂
Answer: B
Explanation: CO reduces Fe₂O₃ to Fe; itself oxidized to CO₂.
34. Which of the following is an exothermic process?
A) Photosynthesis
B) Respiration
C) Evaporation
D) Electrolysis
Answer: B
Explanation: Respiration releases energy → exothermic.
35. Which is an endothermic process?
A) Burning of fuel
B) Neutralization
C) Thermal decomposition of CaCO₃
D) Respiration
Answer: C
Explanation: CaCO₃ → CaO + CO₂ requires heat input.
36. The energy change in a chemical reaction is expressed as:
A) ΔS
B) ΔH
C) ΔG
D) ΔP
Answer: B
Explanation: Enthalpy change (ΔH) measures heat absorbed or released.
37. A redox reaction always involves:
A) Only oxidation
B) Only reduction
C) Both oxidation and reduction simultaneously
D) Neither oxidation nor reduction
Answer: C
Explanation: Redox = oxidation + reduction together.
38. In the thermite reaction, Fe is obtained from:
A) Fe₂O₃
B) FeSO₄
C) FeCl₃
D) Fe₂(SO₄)₃
Answer: A
Explanation: Thermite: Fe₂O₃ + Al → Al₂O₃ + Fe.
39. Thermite reaction is used in:
A) Welding of railway tracks
B) Making glass
C) Cooking food
D) Electroplating
Answer: A
Explanation: Exothermic thermite reaction produces molten iron for welding.
40. In redox reactions, the substance oxidized is called:
A) Oxidizing agent
B) Reducing agent
C) Catalyst
D) Neutralizer
Answer: B
Explanation: The one oxidized donates electrons → reducing agent.
41. In bleaching powder, the oxidizing property is due to:
A) Ca²⁺
B) Cl₂
C) ClO⁻
D) O₂
Answer: C
Explanation: Bleaching action is due to ClO⁻ ion.
42. In photosynthesis, CO₂ is:
A) Oxidized
B) Reduced
C) Neutralized
D) Hydrolyzed
Answer: B
Explanation: CO₂ is reduced to glucose using sunlight.
43. Electrolysis of water gives:
A) H₂ at cathode, O₂ at anode
B) O₂ at cathode, H₂ at anode
C) H₂ + O₂ both at cathode
D) H₂ + O₂ both at anode
Answer: A
Explanation: At cathode → reduction (H₂); at anode → oxidation (O₂).
44. Oxidation state of sulfur in H₂SO₄ is:
A) +2
B) +4
C) +6
D) –2
Answer: C
Explanation: 2(+1) + S + 4(–2) = 0 → S = +6.
45. Which process involves both oxidation and reduction?
A) Electrolysis
B) Neutralization
C) Redox reaction
D) Combustion
Answer: C
Explanation: Oxidation and reduction occur simultaneously in redox.
46. Combustion of methane is a:
A) Decomposition reaction
B) Neutralization reaction
C) Redox reaction
D) Photochemical reaction
Answer: C
Explanation: CH₄ + O₂ → CO₂ + H₂O; C oxidized, O₂ reduced.
47. In the Haber process (N₂ + 3H₂ → 2NH₃), N₂ is:
A) Oxidized
B) Reduced
C) Both oxidized and reduced
D) Neither
Answer: B
Explanation: N in N₂ (0) → N in NH₃ (–3) → reduction.
48. Which metal is extracted using a displacement reaction?
A) Ag from AgNO₃
B) Na from NaCl
C) Mg from MgO
D) Al from Al₂O₃
Answer: A
Explanation: Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag (displacement).
49. Neutralization reaction is always:
A) Exothermic
B) Endothermic
C) Photochemical
D) Reversible
Answer: A
Explanation: Acid + base releases heat → exothermic.
50. Which of the following is used in explosives and redox reactions?
A) KCl
B) KNO₃
C) NaCl
D) NaOH
Answer: B
Explanation: Potassium nitrate (KNO₃) is a strong oxidizer, used in gunpowder.
51. Electrolysis of molten NaCl produces:
A) Na at anode, Cl₂ at cathode
B) Na at cathode, Cl₂ at anode
C) Cl₂ at cathode, NaOH at anode
D) H₂ at cathode, O₂ at anode
Answer: B
Explanation: At cathode → Na⁺ reduced to Na; at anode → Cl⁻ oxidized to Cl₂.
52. In a galvanic cell:
A) Chemical energy → Electrical energy
B) Electrical energy → Chemical energy
C) Heat → Mechanical energy
D) Light → Electrical energy
Answer: A
Explanation: Galvanic cell converts chemical energy into electrical energy.
53. In electrolysis, the electrode where oxidation occurs is:
A) Anode
B) Cathode
C) Both
D) None
Answer: A
Explanation: Oxidation occurs at anode, reduction at cathode.
54. Electroplating is based on:
A) Neutralization reaction
B) Photochemical reaction
C) Electrolysis
D) Precipitation
Answer: C
Explanation: Electroplating deposits a thin layer of metal by electrolysis.
55. Which reaction takes place in photosynthesis?
A) CO₂ reduced to glucose
B) H₂O reduced to O₂
C) Glucose oxidized to CO₂
D) O₂ reduced to CO₂
Answer: A
Explanation: Photosynthesis: CO₂ reduced to glucose using sunlight.
56. Which pigment absorbs light energy in photosynthesis?
A) Hemoglobin
B) Melanin
C) Chlorophyll
D) Myoglobin
Answer: C
Explanation: Chlorophyll absorbs light and drives photosynthesis.
57. Which is the reverse of photosynthesis?
A) Respiration
B) Combustion
C) Fermentation
D) Electrolysis
Answer: A
Explanation: Respiration breaks down glucose → CO₂ + H₂O, opposite of photosynthesis.
58. Fermentation of glucose produces:
A) CO₂ and water
B) Ethanol and CO₂
C) Methane and water
D) Acetic acid and O₂
Answer: B
Explanation: Fermentation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂.
59. In the chlor-alkali process, the products are:
A) NaOH, Cl₂, H₂
B) NaCl, H₂O, O₂
C) Na₂CO₃, HCl, O₂
D) NaOH, O₂, NaCl
Answer: A
Explanation: Electrolysis of brine produces NaOH, Cl₂, and H₂.
60. Haber’s process involves the reaction:
A) N₂ + 3H₂ ⇌ 2NH₃
B) C + O₂ → CO₂
C) CaCO₃ → CaO + CO₂
D) HCl + NaOH → NaCl + H₂O
Answer: A
Explanation: Haber’s process manufactures NH₃.
61. Which catalyst is used in Haber’s process?
A) Pt
B) V₂O₅
C) Fe
D) Ni
Answer: C
Explanation: Iron catalyst with K₂O/Al₂O₃ promoters is used.
62. In Contact process (H₂SO₄ manufacture), the catalyst is:
A) Pt
B) V₂O₅
C) Fe₂O₃
D) Ni
Answer: B
Explanation: Vanadium pentoxide catalyzes SO₂ → SO₃.
63. The Ostwald process is used to manufacture:
A) HCl
B) HNO₃
C) NH₃
D) NaOH
Answer: B
Explanation: Ostwald process produces nitric acid (HNO₃).
64. Catalyst used in Ostwald process is:
A) V₂O₅
B) Ni
C) Pt-Rh gauze
D) Fe
Answer: C
Explanation: Pt-Rh gauze catalyzes oxidation of NH₃.
65. Fermentation of milk to curd is due to:
A) Yeast
B) Lactobacillus
C) Virus
D) Fungi
Answer: B
Explanation: Lactic acid bacteria (Lactobacillus) convert lactose → lactic acid.
66. Which industrial process involves polymerization?
A) Haber process
B) Contact process
C) Ziegler–Natta process
D) Ostwald process
Answer: C
Explanation: Ziegler–Natta process produces polymers like polyethylene.
67. Respiration is essentially a:
A) Redox reaction
B) Precipitation reaction
C) Photochemical reaction
D) Neutralization
Answer: A
Explanation: Glucose oxidized, O₂ reduced → redox.
68. Which of the following is an example of photochemical reaction?
A) Photosynthesis
B) Decomposition of AgCl in sunlight
C) Formation of ozone
D) All of the above
Answer: D
Explanation: All are light-driven reactions.
69. Which gas is released during photosynthesis?
A) CO₂
B) O₂
C) N₂
D) H₂
Answer: B
Explanation: O₂ is released as a by-product.
70. In respiration, glucose is broken down into:
A) CO₂ + H₂O
B) CO₂ + O₂
C) CO + H₂
D) H₂ + O₂
Answer: A
Explanation: C₆H₁₂O₆ + O₂ → CO₂ + H₂O + energy.
71. The chemical reaction in a dry cell is a:
A) Combustion reaction
B) Redox reaction
C) Neutralization
D) Photochemical reaction
Answer: B
Explanation: Zinc is oxidized, MnO₂ reduced → redox.
72. Electrolysis of water is an example of:
A) Combination reaction
B) Decomposition reaction
C) Double displacement reaction
D) Neutralization
Answer: B
Explanation: Water decomposes → H₂ and O₂.
73. Which biological reaction is exothermic?
A) Photosynthesis
B) DNA replication
C) Respiration
D) Protein synthesis
Answer: C
Explanation: Respiration releases energy → exothermic.
74. Which chemical reaction is responsible for ozone formation in the atmosphere?
A) CO₂ + H₂O → H₂CO₃
B) O₂ + UV → 2O
C) O + O₂ → O₃
D) Both B and C
Answer: D
Explanation: UV splits O₂ → O; then O + O₂ → O₃.
75. Which reaction in the body releases energy in ATP form?
A) Respiration
B) Photosynthesis
C) Fermentation
D) Electrolysis
Answer: A
Explanation: Cellular respiration releases energy stored as ATP.
76. Which type of reaction is responsible for acid rain?
A) Neutralization
B) Combustion of fossil fuels
C) Electrolysis
D) Displacement
Answer: B
Explanation: SO₂ and NOx formed from combustion react with water to form acids → acid rain.
77. Corrosion of metals is essentially a:
A) Physical change
B) Redox reaction
C) Precipitation reaction
D) Neutralization
Answer: B
Explanation: Corrosion involves oxidation of metals (e.g., Fe → rust).
78. The reaction: 2KClO₃ → 2KCl + 3O₂ is an example of:
A) Combination
B) Decomposition
C) Neutralization
D) Displacement
Answer: B
Explanation: KClO₃ decomposes on heating to give O₂.
79. Which is an example of a displacement reaction used in daily life?
A) Rusting of iron
B) Silver plating of ornaments using Cu
C) Burning of LPG
D) Photosynthesis
Answer: B
Explanation: Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag, used in silver plating.
80. Which type of reaction occurs in a blast furnace for iron extraction?
A) Combination
B) Reduction
C) Neutralization
D) Decomposition
Answer: B
Explanation: Fe₂O₃ is reduced to Fe by CO.
81. Which chemical reaction is responsible for global warming?
A) Formation of H₂O
B) Combustion of fossil fuels producing CO₂
C) Neutralization of acids and bases
D) Ozone formation
Answer: B
Explanation: Excess CO₂ from combustion → greenhouse effect.
82. Which reaction is used in fire extinguishers?
A) Na₂CO₃ + HCl → NaCl + H₂O + CO₂
B) K₂CO₃ + H₂O → KOH + CO₂
C) CaCO₃ → CaO + CO₂
D) C + O₂ → CO₂
Answer: A
Explanation: CO₂ released smothers fire.
83. Which reaction occurs in nuclear power plants?
A) Chemical redox reaction
B) Fission reaction
C) Fusion reaction
D) Displacement
Answer: B
Explanation: Nuclear fission of U-235 releases energy (not chemical but linked to energy production).
84. Burning of coal mainly produces:
A) H₂O
B) CO₂
C) O₂
D) H₂
Answer: B
Explanation: Carbon burns in oxygen → CO₂.
85. The reaction responsible for smog formation is:
A) NOx + hydrocarbons + sunlight
B) CO₂ + O₂
C) SO₂ + H₂O
D) HCl + NH₃
Answer: A
Explanation: Photochemical reaction of NOx and hydrocarbons → smog.
86. Which of the following is an oxidation reaction?
A) Fe²⁺ → Fe³⁺
B) Cl₂ → 2Cl⁻
C) Cu²⁺ → Cu
D) MnO₂ → Mn²⁺
Answer: A
Explanation: Fe²⁺ loses one electron → oxidation.
87. Which of the following is a reduction reaction?
A) Zn → Zn²⁺
B) O₂ → O²⁻
C) Fe²⁺ → Fe³⁺
D) Cl⁻ → Cl₂
Answer: B
Explanation: O₂ gains electrons → reduced.
88. Combustion of hydrogen gives:
A) H₂O
B) CO₂
C) H₂O₂
D) H₂O + CO₂
Answer: A
Explanation: 2H₂ + O₂ → 2H₂O.
89. Which type of chemical reaction releases maximum energy?
A) Neutralization
B) Combustion
C) Displacement
D) Precipitation
Answer: B
Explanation: Combustion releases large amounts of heat and light.
90. The process of tarnishing of silver is due to:
A) SO₂
B) H₂S
C) CO₂
D) O₂
Answer: B
Explanation: Ag + H₂S → Ag₂S (black coating).
91. Which gas is produced when metals react with acids?
A) CO₂
B) SO₂
C) H₂
D) O₂
Answer: C
Explanation: Metal + Acid → Salt + H₂.
92. The green coating on copper articles is due to:
A) CuO
B) CuCO₃·Cu(OH)₂
C) CuSO₄
D) CuCl₂
Answer: B
Explanation: Copper reacts with CO₂ and H₂O → basic copper carbonate.
93. Which reaction is used in breathing by scuba divers?
A) Decomposition of KClO₃
B) Reaction of NaOH with CO₂
C) Release of O₂ from compressed tanks
D) Displacement of O₂ from CuO
Answer: C
Explanation: Divers carry compressed O₂ cylinders.
94. Which reaction explains bleaching action of chlorine?
A) Cl₂ + H₂O → HCl + HOCl
B) HOCl → HCl + [O]
C) [O] + Colored substance → Colorless substance
D) All of the above
Answer: D
Explanation: Chlorine releases nascent oxygen which decolorizes substances.
95. Which chemical reaction is responsible for depletion of ozone layer?
A) CO₂ + H₂O → H₂CO₃
B) CFCs releasing Cl atoms
C) Combustion of coal
D) Rusting of iron
Answer: B
Explanation: CFCs release Cl· radicals which destroy ozone molecules.
96. Which type of reaction is used in making soap?
A) Neutralization
B) Saponification
C) Precipitation
D) Displacement
Answer: B
Explanation: Saponification = hydrolysis of fats by alkali to form soap + glycerol.
97. Which of the following is an industrial redox reaction?
A) Extraction of iron from Fe₂O₃
B) Electrolysis of water
C) Production of Na by Downs cell
D) All of the above
Answer: D
Explanation: All involve oxidation–reduction processes.
98. The photosynthesis reaction can be written as:
A) CO₂ + H₂O → C₆H₁₂O₆ + O₂
B) C₆H₁₂O₆ → CO₂ + H₂O
C) H₂ + O₂ → H₂O
D) CO₂ + O₂ → CO
Answer: A
Explanation: Photosynthesis forms glucose and oxygen.
99. Which chemical reaction is reversible?
A) Photosynthesis
B) Haber process (N₂ + 3H₂ ⇌ 2NH₃)
C) Combustion of methane
D) Rusting of iron
Answer: B
Explanation: Haber process is reversible, equilibrium-based.
100. Which statement about chemical reactions is correct?
A) They always produce heat
B) They always change state of matter
C) They involve breaking and making of bonds
D) They cannot be reversed
Answer: C
Explanation: The essence of all chemical reactions is bond breaking and bond formation.