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Here are 100 important General Science MCQs on Chemistry, covering key topics commonly asked in UPSC, SSC, and other competitive exams.

General Science - Chemistry (100 Important MCQs)

1. Basic Concepts of Chemistry (1-15)

Which of the following is the smallest particle of an element?

 

a) Molecule

 

b) Atom

 

c) Ion

 

d) Proton

 

Ans:

b) Atom

Who discovered the electron?

 

a) Ernest Rutherford

 

b) J.J. Thomson

 

c) Niels Bohr

 

d) James Chadwick

 

Ans:

b) J.J. Thomson

Which subatomic particle has no charge?

 

a) Proton

 

b) Electron

 

c) Neutron

 

d) Positron

 

Ans:

c) Neutron

The number of protons in the nucleus of an atom is called:

 

a) Atomic number

 

b) Mass number

 

c) Isotope

 

d) Atomic weight

 

Ans:

a) Atomic number

Which element has the lowest atomic number?

 

a) Hydrogen

 

b) Helium

 

c) Oxygen

 

d) Lithium

 

Ans:

a) Hydrogen

The mass of an atom is concentrated in its:

 

a) Nucleus

 

b) Electron cloud

 

c) Outer shell

 

d) None of the above

 

Ans:

a) Nucleus

Which element is a liquid at room temperature?

 

a) Iron

 

b) Mercury

 

c) Lead

 

d) Sodium

 

Ans:

b) Mercury

Which gas is known as "laughing gas"?

 

a) Carbon dioxide

 

b) Nitrous oxide

 

c) Oxygen

 

d) Nitrogen dioxide

 

Ans:

b) Nitrous oxide

Which gas is the most abundant in Earth’s atmosphere?

 

a) Oxygen

 

b) Nitrogen

 

c) Carbon dioxide

 

d) Hydrogen

 

Ans:

b) Nitrogen

What is the chemical symbol for gold?

 

a) Ag

 

b) Au

 

c) Pb

 

d) Pt

 

Ans:

b) Au

Which gas is commonly used in balloons?

 

a) Hydrogen

 

b) Helium

 

c) Oxygen

 

d) Nitrogen

 

Ans:

b) Helium

Which of the following is an alkaline earth metal?

 

a) Sodium

 

b) Potassium

 

c) Calcium

 

d) Iron

 

Ans:

c) Calcium

Who gave the modern periodic table?

 

a) Mendeleev

 

b) Lavoisier

 

c) Dalton

 

d) Avogadro

 

Ans:

a) Mendeleev

What is Avogadro’s number?

 

a) 6.02 × 10²²

 

b) 6.02 × 10²³

 

c) 3.01 × 10²³

 

d) 1.67 × 10²⁴

 

Ans:

b) 6.02 × 10²³

Which of the following is a noble gas?

 

a) Oxygen

 

b) Argon

 

c) Hydrogen

 

d) Nitrogen

 

Ans:

b) Argon

2. Chemical Bonding & Reactions (16-30)

The bond formed by sharing of electrons is called:

 

a) Ionic bond

 

b) Covalent bond

 

c) Hydrogen bond

 

d) Metallic bond

 

Ans:

b) Covalent bond

Which of the following is an ionic compound?

 

a) H₂O

 

b) NaCl

 

c) CO₂

 

d) NH₃

 

Ans:

b) NaCl

The pH of neutral water is:

 

a) 0

 

b) 7

 

c) 10

 

d) 14

 

Ans:

b) 7

Which substance turns blue litmus red?

 

a) Acid

 

b) Base

 

c) Salt

 

d) Alcohol

 

Ans:

a) Acid

Which gas is evolved when an acid reacts with a metal?

 

a) Oxygen

 

b) Carbon dioxide

 

c) Hydrogen

 

d) Nitrogen

 

Ans:

c) Hydrogen

Which of the following is a strong acid?

 

a) Acetic acid

 

b) Hydrochloric acid

 

c) Citric acid

 

d) Carbonic acid

 

Ans:

b) Hydrochloric acid

Which of the following is a base?

 

a) HCl

 

b) NaOH

 

c) H₂SO₄

 

d) CH₃COOH

 

Ans:

b) NaOH

Rusting of iron occurs due to:

 

a) Reaction with CO₂

 

b) Reaction with O₂ and H₂O

 

c) Reaction with N₂

 

d) None of the above

 

Ans:

b) Reaction with O₂ and H₂O

What is the chemical formula of baking soda?

 

a) Na₂CO₃

 

b) NaHCO₃

 

c) K₂CO₃

 

d) CaCO₃

 

Ans:

b) NaHCO₃

Which gas is produced during respiration?

 

a) Oxygen

 

b) Carbon dioxide

 

c) Nitrogen

 

d) Hydrogen

 

Ans:

b) Carbon dioxide

3. States of Matter & Solutions (26-50)

Which state of matter has a definite shape and volume?

 

a) Solid

 

b) Liquid

 

c) Gas

 

d) Plasma

 

Ans:

a) Solid

Which state of matter has the highest energy?

 

a) Solid

 

b) Liquid

 

c) Gas

 

d) Plasma

 

Ans:

d) Plasma

Which of the following can exist in all three states of matter?

 

a) Water

 

b) Iron

 

c) Mercury

 

d) Gold

 

Ans:

a) Water

Which law states that at constant temperature, the volume of a gas is inversely proportional to pressure?

 

a) Charles’ Law

 

b) Boyle’s Law

 

c) Avogadro’s Law

 

d) Dalton’s Law

 

Ans:

b) Boyle’s Law

Which law states that the volume of a gas is directly proportional to temperature?

 

a) Charles’ Law

 

b) Boyle’s Law

 

c) Avogadro’s Law

 

d) Dalton’s Law

 

Ans:

a) Charles’ Law

Which of the following is a homogeneous mixture?

 

a) Sand and salt

 

b) Air

 

c) Oil and water

 

d) Iron and sulfur

 

Ans:

b) Air

Which component is called the universal solvent?

 

a) Alcohol

 

b) Water

 

c) Benzene

 

d) Ether

 

Ans:

b) Water

Which process is used to separate liquids based on their boiling points?

 

a) Filtration

 

b) Distillation

 

c) Crystallization

 

d) Sublimation

 

Ans:

b) Distillation

Which separation technique is used to separate dyes in ink?

 

a) Filtration

 

b) Chromatography

 

c) Sedimentation

 

d) Distillation

 

Ans:

b) Chromatography

Which property of a liquid determines its resistance to flow?

 

a) Surface tension

 

b) Viscosity

 

c) Density

 

d) Pressure

 

Ans:

b) Viscosity

What is the boiling point of pure water at standard atmospheric pressure?

 

a) 0°C

 

b) 50°C

 

c) 100°C

 

d) 200°C

 

Ans:

c) 100°C

Which gas turns limewater milky?

 

a) Oxygen

 

b) Carbon dioxide

 

c) Nitrogen

 

d) Hydrogen

 

Ans:

b) Carbon dioxide

Sublimation is a process in which:

 

a) A solid changes into a gas directly

 

b) A liquid turns into a gas

 

c) A gas turns into a solid

 

d) A liquid turns into a solid

 

Ans:

a) A solid changes into a gas directly

Which of the following substances undergoes sublimation?

 

a) Ice

 

b) Common salt

 

c) Naphthalene

 

d) Sand

 

Ans:

c) Naphthalene

What is the process of a gas turning into a liquid called?

 

a) Condensation

 

b) Evaporation

 

c) Sublimation

 

d) Melting

 

Ans:

a) Condensation

What is the density of water at 4°C?

 

a) 0.5 g/cm³

 

b) 1 g/cm³

 

c) 2 g/cm³

 

d) 10 g/cm³

 

Ans:

b) 1 g/cm³

Which of the following has the highest density?

 

a) Oxygen

 

b) Hydrogen

 

c) Water

 

d) Gold

 

Ans:

d) Gold

Which property of a liquid is responsible for the formation of droplets?

 

a) Density

 

b) Viscosity

 

c) Surface tension

 

d) Compressibility

 

Ans:

c) Surface tension

Which element is used in thermometers due to its high expansion rate?

 

a) Mercury

 

b) Lead

 

c) Sodium

 

d) Iron

 

Ans:

a) Mercury

Which gas is responsible for the fizz in soft drinks?

 

a) Oxygen

 

b) Carbon dioxide

 

c) Hydrogen

 

d) Nitrogen

 

Ans:

b) Carbon dioxide

Which component of air is essential for combustion?

 

a) Nitrogen

 

b) Oxygen

 

c) Carbon dioxide

 

d) Argon

 

Ans:

b) Oxygen

What is dry ice?

 

a) Frozen oxygen

 

b) Solid carbon dioxide

 

c) Frozen nitrogen

 

d) Crushed ice

 

Ans:

b) Solid carbon dioxide

Which state of matter is lightning composed of?

 

a) Solid

 

b) Liquid

 

c) Gas

 

d) Plasma

 

Ans:

d) Plasma

Which of the following is NOT a colloid?

 

a) Smoke

 

b) Milk

 

c) Sugar solution

 

d) Fog

 

Ans:

c) Sugar solution

The Tyndall effect is observed in which of the following?

 

a) True solution

 

b) Colloidal solution

 

c) Suspension

 

d) Both b and c

 

Ans:

d) Both b and c

4. Chemical Reactions & Metals/Non-Metals (51-75)

Which type of chemical reaction involves the combination of two or more substances to form a new compound?

 

a) Decomposition reaction

 

b) Combination reaction

 

c) Displacement reaction

 

d) Redox reaction

 

Ans:

b) Combination reaction

Which type of reaction involves the breakdown of a compound into two or more simpler substances?

 

a) Combination reaction

 

b) Decomposition reaction

 

c) Displacement reaction

 

d) Redox reaction

 

Ans:

b) Decomposition reaction

Which metal is the most reactive?

 

a) Gold

 

b) Iron

 

c) Sodium

 

d) Copper

 

Ans:

c) Sodium

Which of the following is the least reactive metal?

 

a) Sodium

 

b) Potassium

 

c) Gold

 

d) Aluminium

 

Ans:

c) Gold

Which of the following is a noble metal?

 

a) Copper

 

b) Zinc

 

c) Iron

 

d) Platinum

 

Ans:

d) Platinum

Which of the following is an alloy?

 

a) Copper

 

b) Brass

 

c) Sodium

 

d) Mercury

 

Ans:

b) Brass

Which gas is produced when metals react with acids?

 

a) Oxygen

 

b) Hydrogen

 

c) Carbon dioxide

 

d) Nitrogen

 

Ans:

b) Hydrogen

What is the main metal used in electrical wires?

 

a) Iron

 

b) Copper

 

c) Aluminium

 

d) Lead

 

Ans:

b) Copper

Which metal is commonly used in making aircraft?

 

a) Iron

 

b) Aluminium

 

c) Copper

 

d) Zinc

 

Ans:

b) Aluminium

Which of the following non-metals is a good conductor of electricity?

 

a) Sulfur

 

b) Phosphorus

 

c) Graphite

 

d) Oxygen

 

Ans:

c) Graphite

Which process is used to extract metals from their ores?

 

a) Crystallization

 

b) Distillation

 

c) Smelting

 

d) Evaporation

 

Ans:

c) Smelting

What is the chemical formula of rust?

 

a) Fe₂O₃

 

b) FeO

 

c) FeSO₄

 

d) Fe₂O₃·xH₂O

 

Ans:

d) Fe₂O₃·xH₂O

Which of the following prevents rusting?

 

a) Galvanization

 

b) Heating

 

c) Electrolysis

 

d) Sublimation

 

Ans:

a) Galvanization

Which non-metal is essential for breathing?

 

a) Hydrogen

 

b) Oxygen

 

c) Carbon

 

d) Sulfur

 

Ans:

b) Oxygen

Which of the following is an amphoteric metal?

 

a) Aluminium

 

b) Sodium

 

c) Potassium

 

d) Magnesium

 

Ans:

a) Aluminium

Which metal is liquid at room temperature?

 

a) Lead

 

b) Zinc

 

c) Mercury

 

d) Aluminium

 

Ans:

c) Mercury

Which of the following is a metalloid?

 

a) Sodium

 

b) Boron

 

c) Carbon

 

d) Oxygen

 

Ans:

b) Boron

Which metal is the best conductor of electricity?

 

a) Gold

 

b) Silver

 

c) Copper

 

d) Aluminium

 

Ans:

b) Silver

Which gas is evolved when limestone (CaCO₃) is heated?

 

a) Oxygen

 

b) Hydrogen

 

c) Carbon dioxide

 

d) Nitrogen

 

Ans:

c) Carbon dioxide

Which element is the main component of steel?

 

a) Aluminium

 

b) Iron

 

c) Copper

 

d) Zinc

 

Ans:

b) Iron

Which metal is used in galvanization?

 

a) Zinc

 

b) Copper

 

c) Silver

 

d) Aluminium

 

Ans:

a) Zinc

What is the main component of glass?

 

a) Silica

 

b) Limestone

 

c) Boron

 

d) Aluminium

 

Ans:

a) Silica

Which metal is used in thermometers?

 

a) Iron

 

b) Mercury

 

c) Zinc

 

d) Silver

 

Ans:

b) Mercury

Which element is used as a semiconductor in electronic devices?

 

a) Silver

 

b) Copper

 

c) Silicon

 

d) Gold

 

Ans:

c) Silicon

Which process is used to coat iron with a layer of zinc?

 

a) Electroplating

 

b) Galvanization

 

c) Alloying

 

d) Tempering

 

Ans:

b) Galvanization

5. Acids, Bases, Organic Chemistry & Environmental Chemistry (76-100)

Acids, Bases, and Salts

Which acid is commonly found in lemons?

 

a) Acetic acid

 

b) Citric acid

 

c) Sulfuric acid

 

d) Hydrochloric acid

 

Ans:

b) Citric acid

Which of the following is a strong acid?

 

a) Acetic acid

 

b) Hydrochloric acid

 

c) Carbonic acid

 

d) Boric acid

 

Ans:

b) Hydrochloric acid

What is the pH value of pure water?

 

a) 5

 

b) 6

 

c) 7

 

d) 8

 

Ans:

c) 7

Which base is commonly used in soap making?

 

a) Sodium hydroxide

 

b) Calcium hydroxide

 

c) Ammonium hydroxide

 

d) Potassium chloride

 

Ans:

a) Sodium hydroxide

Which indicator turns red in acidic solutions and blue in basic solutions?

 

a) Methyl orange

 

b) Phenolphthalein

 

c) Litmus

 

d) Bromothymol blue

 

Ans:

c) Litmus

Which salt is commonly known as baking soda?

 

a) Sodium chloride

 

b) Sodium bicarbonate

 

c) Sodium carbonate

 

d) Calcium carbonate

 

Ans:

b) Sodium bicarbonate

What is the chemical name of table salt?

 

a) Sodium bicarbonate

 

b) Sodium chloride

 

c) Sodium sulfate

 

d) Potassium chloride

 

Ans:

b) Sodium chloride

Which acid is used in car batteries?

 

a) Nitric acid

 

b) Hydrochloric acid

 

c) Sulfuric acid

 

d) Acetic acid

 

Ans:

c) Sulfuric acid

Which base is commonly known as slaked lime?

 

a) Sodium hydroxide

 

b) Calcium hydroxide

 

c) Ammonium hydroxide

 

d) Magnesium hydroxide

 

Ans:

b) Calcium hydroxide

Which gas is released when acids react with metals?

 

a) Oxygen

 

b) Nitrogen

 

c) Hydrogen

 

d) Carbon dioxide

 

Ans:

c) Hydrogen

Organic Chemistry

Which element is the basis of organic chemistry?

 

a) Hydrogen

 

b) Oxygen

 

c) Carbon

 

d) Nitrogen

 

Ans:

c) Carbon

Which hydrocarbon is used as cooking gas?

 

a) Methane

 

b) Propane

 

c) Butane

 

d) Both b and c

 

Ans:

d) Both b and c

Which of the following is an unsaturated hydrocarbon?

 

a) Methane

 

b) Ethane

 

c) Ethene

 

d) Propane

 

Ans:

c) Ethene

Which compound is commonly known as wood alcohol?

 

a) Ethanol

 

b) Methanol

 

c) Propanol

 

d) Butanol

 

Ans:

b) Methanol

Which compound is used as an antiseptic in hospitals?

 

a) Chloroform

 

b) Ethanol

 

c) Acetone

 

d) Phenol

 

Ans:

d) Phenol

Which polymer is used in making plastic bags?

 

a) Polystyrene

 

b) Polyethylene

 

c) Polyvinyl chloride

 

d) Nylon

 

Ans:

b) Polyethylene

Which type of alcohol is present in alcoholic beverages?

 

a) Methanol

 

b) Ethanol

 

c) Propanol

 

d) Butanol

 

Ans:

b) Ethanol

What is the functional group of alcohols?

 

a) -CHO

 

b) -OH

 

c) -COOH

 

d) -NH₂

 

Ans:

b) -OH

Which hydrocarbon is used in welding?

 

a) Methane

 

b) Ethylene

 

c) Acetylene

 

d) Propane

 

Ans:

c) Acetylene

What is the main component of natural gas?

 

a) Ethane

 

b) Propane

 

c) Methane

 

d) Butane

 

Ans:

c) Methane

Environmental Chemistry

Which gas is mainly responsible for acid rain?

 

a) Oxygen

 

b) Sulfur dioxide

 

c) Methane

 

d) Nitrogen

 

Ans:

b) Sulfur dioxide

Which pollutant is responsible for ozone layer depletion?

 

a) Carbon dioxide

 

b) CFCs (Chlorofluorocarbons)

 

c) Methane

 

d) Nitrogen oxides

 

Ans:

b) CFCs (Chlorofluorocarbons)

Which greenhouse gas has the highest global warming potential?

 

a) Carbon dioxide

 

b) Methane

 

c) Water vapor

 

d) Nitrous oxide

 

Ans:

b) Methane

Which gas is released in large amounts by burning fossil fuels?

 

a) Oxygen

 

b) Carbon dioxide

 

c) Ozone

 

d) Nitrogen

 

Ans:

b) Carbon dioxide

Which element is essential for the process of photosynthesis?

 

a) Nitrogen

 

b) Phosphorus

 

c) Carbon

 

d) Magnesium

 

Ans:

d) Magnesium

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