Practice the most important Chemistry MCQ Questions with Answers for SSC, Railway, Banking, Police, Defence and other competitive exams. These carefully selected multiple choice questions cover Matter, Atoms, Molecules, Periodic Table, Acids, Bases, Salts, Metals, Non-metals, Chemical Reactions and other important Chemistry topics. Every question includes four options, the correct answer and a brief explanation for quick revision.
Q1. The smallest unit of an element is:
A. Molecule
B. Atom
C. Electron
D. Compound
View Answer
An atom is the smallest particle of an element that retains its chemical properties.
Q2. The smallest unit of a compound is:
A. Atom
B. Molecule
C. Electron
D. Proton
View Answer
A molecule is the smallest unit of a compound capable of independent existence.
Q3. Which scientist proposed the Atomic Theory?
A. Ernest Rutherford
B. John Dalton
C. Niels Bohr
D. J. J. Thomson
View Answer
John Dalton proposed the modern Atomic Theory in 1808.
Q4. The negatively charged particle of an atom is:
A. Proton
B. Electron
C. Neutron
D. Nucleus
View Answer
Electrons carry a negative charge and revolve around the nucleus.
Q5. The positively charged particle of an atom is:
A. Electron
B. Proton
C. Neutron
D. Photon
View Answer
Protons are positively charged particles present in the nucleus of an atom.
Q6. Which subatomic particle has no electric charge?
A. Electron
B. Proton
C. Neutron
D. Positron
View Answer
Neutrons are electrically neutral particles found in the nucleus.
Q7. The atomic number of an element is equal to the number of:
A. Neutrons
B. Protons
C. Electrons and Neutrons
D. Molecules
View Answer
The atomic number is defined as the number of protons present in the nucleus.
Q8. The sum of protons and neutrons is called the:
A. Atomic Number
B. Mass Number
C. Atomic Mass
D. Valency
View Answer
Mass number equals the total number of protons and neutrons in an atom.
Q9. Which scientist discovered the electron?
A. Rutherford
B. J. J. Thomson
C. Chadwick
D. Dalton
View Answer
J. J. Thomson discovered the electron in 1897 using cathode ray experiments.
Q10. Which scientist discovered the neutron?
A. Rutherford
B. Dalton
C. James Chadwick
D. Bohr
View Answer
James Chadwick discovered the neutron in 1932.
Q11. Matter is anything that has:
A. Colour only
B. Mass and occupies space
C. Shape only
D. Weight only
View Answer
Matter is defined as anything that has mass and occupies space.
Q12. Which is NOT a state of matter?
A. Solid
B. Liquid
C. Gas
D. Energy
View Answer
The common states of matter are solid, liquid and gas (with plasma also recognized as a state of matter).
Q13. Which state of matter has a definite shape and definite volume?
A. Solid
B. Liquid
C. Gas
D. Plasma
View Answer
Solids have both a definite shape and a definite volume.
Q14. Which state of matter has a definite volume but no definite shape?
A. Solid
B. Liquid
C. Gas
D. Plasma
View Answer
Liquids take the shape of their container but retain a fixed volume.
Q15. Which state of matter has neither definite shape nor definite volume?
A. Solid
B. Liquid
C. Gas
D. Ice
View Answer
Gases expand to fill the entire container and have neither fixed shape nor fixed volume.
Q16. Water changes into vapour by the process of:
A. Condensation
B. Evaporation
C. Sublimation
D. Freezing
View Answer
Evaporation is the process by which liquid water changes into water vapour.
Q17. The process of converting vapour into liquid is called:
A. Sublimation
B. Condensation
C. Melting
D. Freezing
View Answer
Condensation occurs when a gas loses heat and changes into a liquid.
Q18. The process of changing a solid directly into a gas is called:
A. Evaporation
B. Condensation
C. Sublimation
D. Freezing
View Answer
In sublimation, a solid changes directly into a gas without becoming a liquid.
Q19. Which of the following is a pure substance?
A. Air
B. Salt (Sodium Chloride)
C. Milk
D. Soil
View Answer
Sodium chloride is a compound with a fixed composition and is therefore a pure substance.
Q20. Air is a:
A. Compound
B. Element
C. Mixture
D. Metal
View Answer
Air is a homogeneous mixture of gases, mainly nitrogen and oxygen.
Q21. Which scientist is known as the Father of the Modern Periodic Table?
A. John Dalton
B. Dmitri Mendeleev
C. Ernest Rutherford
D. J. J. Thomson
View Answer
Dmitri Mendeleev proposed the first widely accepted Periodic Table and is known as its father.
Q22. The Modern Periodic Law was given by:
A. Henry Moseley
B. John Dalton
C. Niels Bohr
D. Rutherford
View Answer
Henry Moseley stated that the properties of elements are periodic functions of their atomic numbers.
Q23. The modern periodic table is arranged according to:
A. Atomic Mass
B. Atomic Number
C. Density
D. Valency
View Answer
The modern periodic table is arranged in increasing order of atomic number.
Q24. How many periods are there in the modern periodic table?
A. 6
B. 7
C. 8
D. 9
View Answer
The modern periodic table consists of 7 horizontal periods.
Q25. How many groups are there in the modern periodic table?
A. 16
B. 17
C. 18
D. 20
View Answer
The periodic table contains 18 vertical groups.
Q26. Which group contains the Noble Gases?
A. Group 1
B. Group 17
C. Group 18
D. Group 16
View Answer
Group 18 elements are known as Noble or Inert Gases.
Q27. Which group contains the Alkali Metals?
A. Group 1
B. Group 2
C. Group 17
D. Group 18
View Answer
Group 1 elements such as lithium, sodium and potassium are called Alkali Metals.
Q28. Which group contains the Halogens?
A. Group 1
B. Group 2
C. Group 17
D. Group 18
View Answer
Fluorine, chlorine, bromine and iodine belong to Group 17 and are called Halogens.
Q29. Which of the following is a metal?
A. Oxygen
B. Sulphur
C. Iron
D. Chlorine
View Answer
Iron is a metal known for its strength, conductivity and magnetic properties.
Q30. Which of the following is a non-metal?
A. Copper
B. Aluminium
C. Sulphur
D. Zinc
View Answer
Sulphur is a yellow-coloured non-metal.
Q31. Which metal is liquid at room temperature?
A. Sodium
B. Mercury
C. Iron
D. Zinc
View Answer
Mercury is the only metal that remains liquid at ordinary room temperature.
Q32. Which non-metal is liquid at room temperature?
A. Oxygen
B. Nitrogen
C. Bromine
D. Sulphur
View Answer
Bromine is the only non-metal that is liquid at room temperature.
Q33. Which gas is essential for respiration?
A. Nitrogen
B. Oxygen
C. Carbon Dioxide
D. Hydrogen
View Answer
Oxygen is required for respiration in humans and most living organisms.
Q34. Which gas is used in fire extinguishers?
A. Oxygen
B. Hydrogen
C. Carbon Dioxide
D. Nitrogen
View Answer
Carbon dioxide helps extinguish fires by reducing the oxygen supply.
Q35. Which gas is known as ‘Laughing Gas’?
A. Nitrogen
B. Nitrous Oxide
C. Carbon Monoxide
D. Sulphur Dioxide
View Answer
Nitrous oxide (N₂O) is commonly called Laughing Gas because of its anaesthetic properties.
Q36. Which gas is known as ‘Marsh Gas’?
A. Methane
B. Ethane
C. Propane
D. Butane
View Answer
Methane is produced in marshes by the decomposition of organic matter and is therefore called Marsh Gas.
Q37. Which gas is known as ‘Dry Ice’ in solid form?
A. Oxygen
B. Hydrogen
C. Carbon Dioxide
D. Nitrogen
View Answer
Solid carbon dioxide is called Dry Ice because it changes directly into gas without becoming liquid.
Q38. Which gas is mainly responsible for acid rain?
A. Oxygen
B. Nitrogen
C. Sulphur Dioxide
D. Hydrogen
View Answer
Sulphur dioxide and nitrogen oxides react with water vapour to form acid rain.
Q39. Which gas is known as the ‘Greenhouse Gas’?
A. Oxygen
B. Carbon Dioxide
C. Hydrogen
D. Helium
View Answer
Carbon dioxide is one of the major greenhouse gases responsible for global warming.
Q40. Which gas is most abundant in Earth’s atmosphere?
A. Oxygen
B. Carbon Dioxide
C. Nitrogen
D. Hydrogen
View Answer
Nitrogen constitutes about 78% of the Earth’s atmosphere.
Q41. A substance with a pH value less than 7 is:
A. Neutral
B. Acidic
C. Basic
D. Salty
View Answer
Acids have a pH value below 7, while bases have a pH above 7.
Q42. A substance with a pH value greater than 7 is:
A. Acidic
B. Neutral
C. Basic
D. Metallic
View Answer
Basic (alkaline) substances have a pH value greater than 7.
Q43. What is the pH value of pure water?
A. 5
B. 6
C. 7
D. 8
View Answer
Pure water is neutral and has a pH value of 7 at room temperature.
Q44. Which of the following is a strong acid?
A. Acetic Acid
B. Hydrochloric Acid
C. Citric Acid
D. Carbonic Acid
View Answer
Hydrochloric acid (HCl) is a strong acid commonly found in the human stomach.
Q45. Which acid is present in lemon?
A. Acetic Acid
B. Citric Acid
C. Formic Acid
D. Oxalic Acid
View Answer
Citric acid gives lemons and oranges their sour taste.
Q46. Which acid is present in vinegar?
A. Citric Acid
B. Lactic Acid
C. Acetic Acid
D. Tartaric Acid
View Answer
Vinegar is a dilute solution of acetic acid.
Q47. Which acid is found in ant stings?
A. Citric Acid
B. Formic Acid
C. Acetic Acid
D. Nitric Acid
View Answer
Ant stings contain formic acid, also called methanoic acid.
Q48. Which acid is present in curd?
A. Acetic Acid
B. Citric Acid
C. Lactic Acid
D. Oxalic Acid
View Answer
Lactic acid is produced during the fermentation of milk into curd.
Q49. Which acid is found in tamarind?
A. Tartaric Acid
B. Lactic Acid
C. Formic Acid
D. Hydrochloric Acid
View Answer
Tamarind is rich in tartaric acid, which gives it its sour taste.
Q50. Which base is commonly known as caustic soda?
A. Sodium Hydroxide
B. Potassium Hydroxide
C. Calcium Hydroxide
D. Ammonium Hydroxide
View Answer
Sodium hydroxide (NaOH) is commonly known as caustic soda.
Q51. Which base is commonly known as caustic potash?
A. Sodium Hydroxide
B. Potassium Hydroxide
C. Calcium Hydroxide
D. Magnesium Hydroxide
View Answer
Potassium hydroxide (KOH) is commonly known as caustic potash.
Q52. Which substance is commonly known as slaked lime?
A. Calcium Oxide
B. Calcium Hydroxide
C. Calcium Carbonate
D. Sodium Carbonate
View Answer
Calcium hydroxide, Ca(OH)₂, is commonly called slaked lime.
Q53. Which substance is commonly known as quicklime?
A. Calcium Oxide
B. Calcium Hydroxide
C. Calcium Carbonate
D. Magnesium Oxide
View Answer
Calcium oxide (CaO) is commonly known as quicklime.
Q54. Which substance is commonly known as baking soda?
A. Sodium Carbonate
B. Sodium Bicarbonate
C. Calcium Carbonate
D. Potassium Carbonate
View Answer
Sodium bicarbonate (NaHCO₃) is used in baking and as an antacid.
Q55. Which substance is commonly known as washing soda?
A. Sodium Chloride
B. Sodium Carbonate
C. Sodium Hydroxide
D. Sodium Sulphate
View Answer
Washing soda is sodium carbonate (Na₂CO₃·10H₂O), commonly used as a cleaning agent.
Q56. Common salt is chemically known as:
A. Sodium Carbonate
B. Sodium Chloride
C. Sodium Hydroxide
D. Potassium Chloride
View Answer
Common table salt is sodium chloride (NaCl).
Q57. Which gas is released when an acid reacts with a carbonate?
A. Oxygen
B. Hydrogen
C. Carbon Dioxide
D. Nitrogen
View Answer
Acids react with carbonates to produce carbon dioxide gas, salt and water.
Q58. The reaction between an acid and a base is called:
A. Oxidation
B. Neutralization
C. Reduction
D. Combustion
View Answer
Neutralization produces salt and water from an acid and a base.
Q59. Which indicator turns red in an acidic solution?
A. Phenolphthalein
B. Blue Litmus Paper
C. Red Litmus Paper
D. Turmeric
View Answer
Blue litmus paper turns red in the presence of an acid.
Q60. Which indicator turns blue in a basic solution?
A. Red Litmus Paper
B. Blue Litmus Paper
C. Phenolphthalein
D. Methyl Orange
View Answer
Red litmus paper changes to blue in alkaline (basic) solutions.
Q61. Which metal is the best conductor of electricity?
A. Copper
B. Aluminium
C. Silver
D. Iron
View Answer
Silver has the highest electrical conductivity among all metals.
Q62. Which metal is commonly used for electrical wiring?
A. Iron
B. Copper
C. Lead
D. Zinc
View Answer
Copper is widely used for electrical wiring because of its excellent conductivity and ductility.
Q63. Stainless steel is an alloy of:
A. Iron, Chromium and Nickel
B. Copper and Zinc
C. Copper and Tin
D. Iron and Carbon only
View Answer
Stainless steel is corrosion-resistant because it contains chromium, usually along with nickel.
Q64. Brass is an alloy of:
A. Copper and Tin
B. Copper and Zinc
C. Iron and Carbon
D. Aluminium and Copper
View Answer
Brass is a widely used alloy made of copper and zinc.
Q65. Bronze is an alloy of:
A. Copper and Zinc
B. Copper and Tin
C. Iron and Nickel
D. Lead and Tin
View Answer
Bronze is a strong alloy of copper and tin used since ancient times.
Q66. Solder is mainly an alloy of:
A. Copper and Zinc
B. Tin and Lead
C. Iron and Carbon
D. Aluminium and Magnesium
View Answer
Solder is a low-melting alloy commonly used for joining electrical components.
Q67. Which metal is extracted from bauxite ore?
A. Iron
B. Copper
C. Aluminium
D. Zinc
View Answer
Bauxite is the principal ore of aluminium.
Q68. Rust is mainly:
A. Iron Sulphide
B. Hydrated Iron Oxide
C. Iron Carbonate
D. Iron Chloride
View Answer
Rust is hydrated iron(III) oxide formed when iron reacts with oxygen and moisture.
Q69. Rusting of iron requires:
A. Oxygen only
B. Water only
C. Oxygen and Moisture
D. Carbon Dioxide only
View Answer
Iron rusts when exposed to both oxygen and water.
Q70. Galvanization is the process of coating iron with:
A. Copper
B. Zinc
C. Silver
D. Aluminium
View Answer
A zinc coating protects iron from rusting by preventing contact with air and moisture.
Q71. Which gas is evolved when zinc reacts with dilute hydrochloric acid?
A. Oxygen
B. Carbon Dioxide
C. Hydrogen
D. Nitrogen
View Answer
Zinc reacts with dilute hydrochloric acid to produce zinc chloride and hydrogen gas.
Q72. Which process involves the addition of oxygen to a substance?
A. Reduction
B. Neutralization
C. Oxidation
D. Sublimation
View Answer
Oxidation is the gain of oxygen or the loss of electrons.
Q73. Which process involves the removal of oxygen from a substance?
A. Oxidation
B. Reduction
C. Combustion
D. Neutralization
View Answer
Reduction is the loss of oxygen or the gain of electrons.
Q74. Which gas supports combustion?
A. Nitrogen
B. Carbon Dioxide
C. Oxygen
D. Hydrogen
View Answer
Oxygen itself does not burn but supports the burning of other substances.
Q75. Which gas is used in the manufacture of ammonia by the Haber Process?
A. Oxygen
B. Nitrogen
C. Carbon Dioxide
D. Chlorine
View Answer
Ammonia is produced by reacting nitrogen with hydrogen in the Haber Process.
Q76. Which gas is commonly used to fill weather balloons?
A. Oxygen
B. Helium
C. Nitrogen
D. Carbon Dioxide
View Answer
Helium is lighter than air and non-flammable, making it suitable for balloons.
Q77. Which gas is used in electric bulbs?
A. Hydrogen
B. Argon
C. Oxygen
D. Chlorine
View Answer
Argon is an inert gas used inside incandescent bulbs to protect the tungsten filament.
Q78. Which gas is commonly used for welding?
A. Oxygen
B. Acetylene
C. Carbon Dioxide
D. Helium
View Answer
Acetylene is used with oxygen in oxy-acetylene welding because it produces a very hot flame.
Q79. Which gas is commonly known as LPG?
A. Methane
B. Propane and Butane
C. Hydrogen
D. Carbon Monoxide
View Answer
Liquefied Petroleum Gas (LPG) mainly consists of propane and butane.
Q80. Which gas is the main component of CNG?
A. Carbon Dioxide
B. Methane
C. Propane
D. Butane
View Answer
Compressed Natural Gas (CNG) mainly contains methane, making it a cleaner fuel.
Q81. Which fertilizer is the richest source of nitrogen?
A. Urea
B. Super Phosphate
C. Potash
D. Gypsum
View Answer
Urea contains about 46% nitrogen and is the most widely used nitrogenous fertilizer.
Q82. Which nutrient promotes root development in plants?
A. Nitrogen
B. Phosphorus
C. Potassium
D. Calcium
View Answer
Phosphorus is essential for root growth, flowering and seed formation.
Q83. Which nutrient improves disease resistance in plants?
A. Nitrogen
B. Potassium
C. Phosphorus
D. Sulphur
View Answer
Potassium helps improve plant strength, disease resistance and fruit quality.
Q84. Which gas is released during photosynthesis?
A. Nitrogen
B. Carbon Dioxide
C. Oxygen
D. Hydrogen
View Answer
Green plants release oxygen as a by-product of photosynthesis.
Q85. Which gas is absorbed by plants during photosynthesis?
A. Oxygen
B. Carbon Dioxide
C. Hydrogen
D. Nitrogen
View Answer
Plants use carbon dioxide and water to produce food in the presence of sunlight.
Q86. Which element is essential for the formation of chlorophyll?
A. Iron
B. Magnesium
C. Calcium
D. Sodium
View Answer
Magnesium is the central element present in the chlorophyll molecule.
Q87. Which vitamin contains the element cobalt?
A. Vitamin A
B. Vitamin B₁₂
C. Vitamin C
D. Vitamin D
View Answer
Vitamin B₁₂ (Cobalamin) contains cobalt in its chemical structure.
Q88. Which metal is used in thermometers?
A. Aluminium
B. Mercury
C. Zinc
D. Iron
View Answer
Mercury was traditionally used in thermometers because it expands uniformly with temperature.
Q89. Which metal is used in galvanization?
A. Copper
B. Zinc
C. Tin
D. Silver
View Answer
Iron is coated with zinc during galvanization to protect it from rusting.
Q90. Which element is used in the filament of electric bulbs?
A. Copper
B. Iron
C. Tungsten
D. Aluminium
View Answer
Tungsten has a very high melting point, making it ideal for bulb filaments.
Q91. Which gas is used for the hydrogenation of vegetable oils?
A. Oxygen
B. Hydrogen
C. Nitrogen
D. Chlorine
View Answer
Hydrogen is added to vegetable oils in the presence of a nickel catalyst to produce vanaspati ghee.
Q92. Which metal is the main constituent of steel?
A. Copper
B. Iron
C. Aluminium
D. Zinc
View Answer
Steel is primarily an alloy of iron with carbon and other elements.
Q93. Which element is required for the manufacture of stainless steel?
A. Chromium
B. Sodium
C. Calcium
D. Sulphur
View Answer
Chromium provides corrosion resistance to stainless steel.
Q94. Which metal is extracted from the ore haematite?
A. Copper
B. Aluminium
C. Iron
D. Zinc
View Answer
Haematite (Fe₂O₃) is one of the most important ores of iron.
Q95. Which ore is the chief source of aluminium?
A. Magnetite
B. Bauxite
C. Galena
D. Cinnabar
View Answer
Bauxite is the principal ore from which aluminium is extracted.
Q96. Which ore is the chief source of copper?
A. Bauxite
B. Chalcopyrite
C. Haematite
D. Zinc Blende
View Answer
Chalcopyrite (CuFeS₂) is the most important ore of copper.
Q97. Which ore is the chief source of mercury?
A. Galena
B. Cinnabar
C. Bauxite
D. Magnetite
View Answer
Cinnabar (HgS) is the principal ore of mercury.
Q98. Which ore is the chief source of lead?
A. Galena
B. Bauxite
C. Magnetite
D. Gypsum
View Answer
Galena (PbS) is the most important ore of lead.
Q99. Which branch of chemistry deals with carbon compounds?
A. Physical Chemistry
B. Organic Chemistry
C. Inorganic Chemistry
D. Analytical Chemistry
View Answer
Organic chemistry is the study of carbon-containing compounds and their reactions.
Q100. Which branch of chemistry deals with compounds other than most carbon compounds?
A. Organic Chemistry
B. Inorganic Chemistry
C. Biochemistry
D. Nuclear Chemistry
View Answer
Inorganic chemistry deals with the study of elements and compounds other than the majority of carbon compounds.
These 100 Chemistry MCQ Questions with Answers cover the most important topics for SSC, Railway, Banking, Police, Defence and other competitive examinations. The questions include atomic structure, periodic table, acids, bases, salts, metals, non-metals, alloys, important gases, fertilizers, ores, chemical reactions and everyday chemistry. Regular practice of these MCQs will strengthen your concepts, improve your accuracy and help you score higher in the General Science section of competitive exams.