Practice 100 Chemical Reactions MCQs with answers covering types of reactions, redox reactions, balancing equations, exothermic and endothermic reactions, and reaction rates—ideal for students and exam preparation.
Chemical reactions are fundamental processes that explain how substances interact, transform, and produce new materials in both natural and industrial settings. Understanding key concepts such as types of chemical reactions, balancing chemical equations, oxidation and reduction, exothermic and endothermic reactions, and factors affecting reaction rates is essential for chemistry students and competitive exam aspirants. This article presents 100 carefully curated Chemical Reactions MCQs with answers, designed to strengthen conceptual clarity, support quick revision, and enhance exam performance. These chemical reactions multiple choice questions are ideal for school exams, entrance tests, and general chemistry practice.
Below are 100 Multiple Choice Questions (MCQs) on the topic Chemical Reactions, written in clear English and suitable for school, college, and competitive exams.
Chemical Reactions – 100 MCQs with Answers
1. A chemical reaction involves
A. Physical change only
B. Formation of new substances
C. Change in shape
D. Change in state only
Answer: B
2. A substance that takes part in a chemical reaction is called
A. Product
B. Catalyst
C. Reactant
D. Residue
Answer: C
3. A substance formed as a result of a chemical reaction is called
A. Reactant
B. Catalyst
C. Product
D. Medium
Answer: C
4. Which of the following is a chemical change?
A. Melting of ice
B. Boiling of water
C. Rusting of iron
D. Dissolving sugar in water
Answer: C
5. Rusting of iron requires
A. Oxygen only
B. Water only
C. Oxygen and water
D. Carbon dioxide
Answer: C
6. A chemical equation is
A. A word equation
B. A symbolic representation of a reaction
C. A physical change
D. A balanced statement
Answer: B
7. Which law is obeyed by a balanced chemical equation?
A. Law of multiple proportions
B. Law of conservation of mass
C. Law of definite proportions
D. Law of constant volume
Answer: B
8. In a balanced chemical equation, the number of atoms of each element is
A. More on RHS
B. More on LHS
C. Equal on both sides
D. Different
Answer: C
9. Which of the following is a combination reaction?
A. Decomposition of calcium carbonate
B. Burning of magnesium
C. Rusting of iron
D. Displacement of copper
Answer: B
10. The reaction in which a compound breaks into simpler substances is called
A. Combination reaction
B. Displacement reaction
C. Decomposition reaction
D. Neutralization reaction
Answer: C
11. Which type of reaction requires heat to proceed?
A. Endothermic
B. Exothermic
C. Neutralization
D. Displacement
Answer: A
12. An exothermic reaction is one that
A. Absorbs heat
B. Releases heat
C. Does not involve heat
D. Requires catalyst
Answer: B
13. Which gas is released during the reaction of acid with metal?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide
Answer: C
14. A reaction in which one element replaces another is called
A. Combination
B. Decomposition
C. Displacement
D. Redox
Answer: C
15. Which metal can displace copper from copper sulfate solution?
A. Gold
B. Silver
C. Iron
D. Mercury
Answer: C
16. Oxidation involves
A. Gain of electrons
B. Loss of electrons
C. Gain of neutrons
D. Loss of protons
Answer: B
17. Reduction involves
A. Loss of electrons
B. Gain of electrons
C. Loss of protons
D. Gain of neutrons
Answer: B
18. A reaction involving both oxidation and reduction is called
A. Neutralization
B. Combination
C. Redox reaction
D. Decomposition
Answer: C
19. Which of the following is a precipitation reaction?
A. Burning of fuel
B. Formation of insoluble solid
C. Decomposition by heat
D. Rusting
Answer: B
20. The white precipitate formed when silver nitrate reacts with sodium chloride is
A. Sodium nitrate
B. Silver oxide
C. Silver chloride
D. Sodium chloride
Answer: C
21. Neutralization reaction occurs between
A. Acid and acid
B. Base and base
C. Acid and base
D. Salt and water
Answer: C
22. The pH of a neutral solution is
A. 1
B. 5
C. 7
D. 14
Answer: C
23. Which substance speeds up a chemical reaction without being consumed?
A. Reactant
B. Product
C. Catalyst
D. Inhibitor
Answer: C
24. Which of the following is NOT a chemical reaction?
A. Burning of coal
B. Digestion of food
C. Freezing of water
D. Rusting
Answer: C
25. In photosynthesis, plants convert
A. Oxygen into carbon dioxide
B. Carbon dioxide into glucose
C. Nitrogen into protein
D. Water into oxygen
Answer: B
26. Respiration is an example of
A. Endothermic reaction
B. Exothermic reaction
C. Decomposition reaction
D. Combination reaction
Answer: B
27. Which reaction involves exchange of ions?
A. Displacement
B. Double displacement
C. Combination
D. Decomposition
Answer: B
28. The reaction between sodium hydroxide and hydrochloric acid produces
A. Sodium chloride and water
B. Sodium hydrogen carbonate
C. Hydrogen gas
D. Oxygen gas
Answer: A
29. Which condition increases the rate of chemical reaction?
A. Lower temperature
B. Smaller surface area
C. Presence of catalyst
D. Dilution
Answer: C
30. Increasing temperature generally
A. Decreases reaction rate
B. Stops reaction
C. Increases reaction rate
D. Has no effect
Answer: C
31. Which of the following is an example of corrosion?
A. Burning
B. Rusting
C. Photosynthesis
D. Respiration
Answer: B
32. Corrosion of iron forms
A. Iron oxide
B. Iron carbonate
C. Iron hydroxide
D. Iron sulfide
Answer: A
33. Which metal does not corrode easily?
A. Iron
B. Copper
C. Gold
D. Aluminum
Answer: C
34. Galvanization prevents rusting by coating iron with
A. Copper
B. Silver
C. Zinc
D. Aluminum
Answer: C
35. A reversible reaction is one which
A. Occurs only once
B. Cannot be reversed
C. Proceeds in both directions
D. Is always slow
Answer: C
36. Which symbol is used to show heat in a chemical equation?
A. ↑
B. ↓
C. Δ
D. →
Answer: C
37. The arrow (→) in a chemical equation means
A. Equals
B. Reacts to form
C. Heat
D. Catalyst
Answer: B
38. Which reaction gives off light and heat?
A. Photosynthesis
B. Combustion
C. Decomposition
D. Neutralization
Answer: B
39. Burning of candle wax is a
A. Physical change
B. Chemical change
C. Nuclear change
D. Temporary change
Answer: B
40. Which of the following is a fast reaction?
A. Rusting
B. Fermentation
C. Explosion
D. Digestion
Answer: C
41. Which gas is produced when calcium carbonate is heated?
A. Oxygen
B. Nitrogen
C. Carbon dioxide
D. Hydrogen
Answer: C
42. The reaction CaCO₃ → CaO + CO₂ is a
A. Combination reaction
B. Decomposition reaction
C. Displacement reaction
D. Redox reaction
Answer: B
43. Which factor does NOT affect reaction rate?
A. Temperature
B. Pressure
C. Color
D. Catalyst
Answer: C
44. Which reaction occurs in the presence of sunlight?
A. Thermal decomposition
B. Photochemical reaction
C. Neutralization
D. Displacement
Answer: B
45. Which chemical reaction takes place in batteries?
A. Acid-base reaction
B. Nuclear reaction
C. Redox reaction
D. Combination reaction
Answer: C
46. Which of the following reactions is reversible?
A. Rusting
B. Combustion
C. Photosynthesis
D. Explosion
Answer: C
47. Which gas supports combustion?
A. Nitrogen
B. Carbon dioxide
C. Oxygen
D. Hydrogen
Answer: C
48. A reaction in which energy is absorbed is called
A. Exothermic
B. Endothermic
C. Neutral
D. Redox
Answer: B
49. Which of the following is a slow chemical reaction?
A. Burning
B. Explosion
C. Rusting
D. Neutralization
Answer: C
50. The process of balancing a chemical equation ensures
A. Correct formulas
B. Mass conservation
C. Reaction speed
D. Energy change
Answer: B
51. Which reaction involves exchange of ions between two compounds?
A. Combination
B. Decomposition
C. Single displacement
D. Double displacement
Answer: D
52. The reaction between barium chloride and sodium sulfate produces
A. Barium sulfate precipitate
B. Sodium chloride precipitate
C. Barium chloride solution
D. Sulfur dioxide gas
Answer: A
53. Which of the following is a reversible reaction?
A. Rusting of iron
B. Combustion of coal
C. Photosynthesis
D. Explosion
Answer: C
54. Which reaction occurs in the presence of a catalyst?
A. Combustion
B. Catalytic reaction
C. Decomposition
D. Neutralization
Answer: B
55. Which metal is most reactive?
A. Copper
B. Iron
C. Zinc
D. Potassium
Answer: D
56. Which substance acts as a reducing agent?
A. One that gets oxidized
B. One that gets reduced
C. One that gains oxygen
D. One that loses hydrogen
Answer: A
57. Oxidation can also be defined as
A. Gain of hydrogen
B. Loss of oxygen
C. Loss of hydrogen
D. Gain of electrons
Answer: C
58. Reduction can also be defined as
A. Gain of oxygen
B. Loss of electrons
C. Gain of hydrogen
D. Loss of neutrons
Answer: C
59. Which reaction produces heat and light?
A. Decomposition
B. Combustion
C. Neutralization
D. Precipitation
Answer: B
60. Which of the following is NOT an example of a redox reaction?
A. Rusting
B. Respiration
C. Photosynthesis
D. Melting of ice
Answer: D
61. Which chemical reaction is involved in digestion of food?
A. Physical reaction
B. Chemical reaction
C. Nuclear reaction
D. Reversible reaction
Answer: B
62. The process of burning fuel is a
A. Endothermic reaction
B. Exothermic reaction
C. Neutral reaction
D. Photochemical reaction
Answer: B
63. Which reaction requires light energy?
A. Combustion
B. Respiration
C. Photosynthesis
D. Decomposition
Answer: C
64. Which gas is released during thermal decomposition of metal carbonates?
A. Oxygen
B. Hydrogen
C. Carbon dioxide
D. Nitrogen
Answer: C
65. A balanced chemical equation has
A. Equal number of molecules
B. Equal mass on both sides
C. Equal volume on both sides
D. Equal coefficients
Answer: B
66. Which substance remains unchanged during a reaction?
A. Reactant
B. Product
C. Catalyst
D. Precipitate
Answer: C
67. Which of the following slows down a chemical reaction?
A. Increase in temperature
B. Catalyst
C. Decrease in surface area
D. Increase in concentration
Answer: C
68. The rate of reaction increases when
A. Temperature decreases
B. Concentration increases
C. Catalyst is removed
D. Pressure decreases
Answer: B
69. Which reaction takes place in electrolysis of water?
A. Combination
B. Decomposition
C. Displacement
D. Neutralization
Answer: B
70. Electrolysis of water produces
A. Hydrogen and oxygen
B. Carbon dioxide and oxygen
C. Nitrogen and hydrogen
D. Oxygen only
Answer: A
71. Which type of reaction occurs when quicklime reacts with water?
A. Decomposition
B. Combination
C. Displacement
D. Double displacement
Answer: B
72. The reaction CaO + H₂O → Ca(OH)₂ is
A. Endothermic
B. Exothermic
C. Neutral
D. Reversible
Answer: B
73. Which of the following is an example of slow reaction?
A. Explosion
B. Combustion
C. Rusting
D. Neutralization
Answer: C
74. Which reaction forms an insoluble solid?
A. Combination
B. Decomposition
C. Precipitation
D. Redox
Answer: C
75. A reaction in which two compounds exchange ions is
A. Single displacement
B. Combination
C. Double displacement
D. Decomposition
Answer: C
76. Which of the following reactions releases energy?
A. Endothermic
B. Exothermic
C. Neutral
D. Reversible
Answer: B
77. The rusting of iron is an example of
A. Oxidation
B. Reduction
C. Neutralization
D. Decomposition
Answer: A
78. Which substance is oxidized in a reaction?
A. One that gains electrons
B. One that loses electrons
C. One that gains hydrogen
D. One that loses oxygen
Answer: B
79. Which reaction occurs in living organisms to release energy?
A. Photosynthesis
B. Respiration
C. Combustion
D. Neutralization
Answer: B
80. Which type of reaction occurs in acid-base reactions?
A. Combination
B. Neutralization
C. Decomposition
D. Oxidation
Answer: B
81. Which factor does NOT affect reaction rate?
A. Temperature
B. Concentration
C. Color of reactants
D. Catalyst
Answer: C
82. Which reaction produces a salt and water?
A. Decomposition
B. Neutralization
C. Combination
D. Redox
Answer: B
83. The reaction of sodium with water is
A. Slow
B. Moderate
C. Very fast
D. No reaction
Answer: C
84. Which chemical reaction is used in fireworks?
A. Endothermic
B. Combustion
C. Neutralization
D. Precipitation
Answer: B
85. Which symbol shows evolution of gas in a chemical equation?
A. ↓
B. Δ
C. →
D. ↑
Answer: D
86. Which symbol shows formation of precipitate?
A. ↑
B. →
C. ↓
D. Δ
Answer: C
87. A reaction that absorbs heat from surroundings is
A. Exothermic
B. Endothermic
C. Neutral
D. Fast
Answer: B
88. Which reaction happens continuously but slowly?
A. Explosion
B. Combustion
C. Rusting
D. Neutralization
Answer: C
89. Chemical reactions are important because they
A. Change matter
B. Release energy
C. Help life processes
D. All of these
Answer: D
90. Which reaction occurs in a car engine?
A. Neutralization
B. Combustion
C. Decomposition
D. Precipitation
Answer: B
91. Which reaction takes place during fermentation?
A. Oxidation
B. Reduction
C. Chemical reaction
D. Physical reaction
Answer: C
92. Which reaction is used to make cement hard?
A. Decomposition
B. Hydration
C. Combustion
D. Oxidation
Answer: B
93. Which reaction produces energy in cells?
A. Photosynthesis
B. Respiration
C. Neutralization
D. Electrolysis
Answer: B
94. Which of the following is NOT a type of chemical reaction?
A. Combination
B. Displacement
C. Decomposition
D. Reflection
Answer: D
95. Chemical reactions always involve
A. Change in state
B. Change in energy
C. Change in color
D. Change in mass
Answer: B
96. Which reaction occurs in rust prevention by painting?
A. Oxidation
B. Reduction
C. Prevention of oxidation
D. Decomposition
Answer: C
97. Which reaction is used in electroplating?
A. Redox reaction
B. Neutralization
C. Combination
D. Decomposition
Answer: A
98. Which reaction occurs in digestion of food?
A. Physical reaction
B. Chemical reaction
C. Nuclear reaction
D. Reversible reaction
Answer: B
99. Which reaction releases gas bubbles?
A. Precipitation
B. Decomposition
C. Gas evolution reaction
D. Neutralization
Answer: C
100. Chemical reactions are essential for
A. Industry
B. Life processes
C. Environment
D. All of these
Answer: D
