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1. Which branch of science deals with the study of composition, structure, and properties of matter?
ⓐ. Physics
ⓑ. Chemistry
ⓒ. Biology
ⓓ. Geology
Correct Answer: Chemistry
Explanation: Chemistry focuses on understanding matter at the atomic and molecular level, including its transformations. Physics deals with fundamental laws of nature, biology studies living organisms, and geology studies the Earth’s structure and rocks.
2. Which of the following is not an importance of chemistry in everyday life?
ⓐ. Understanding the structure of DNA
ⓑ. Manufacturing of medicines
ⓒ. Designing of bridges and buildings
ⓓ. Production of fertilizers
Correct Answer: Designing of bridges and buildings
Explanation: Chemistry is crucial for medicines, fertilizers, fuels, and even DNA studies in biology. Designing of bridges is mainly civil engineering, although material science (with chemistry) supports it indirectly.
3. Who is credited with introducing the concept of the “mole” in chemistry?
ⓐ. Avogadro
ⓑ. Dalton
ⓒ. Lavoisier
ⓓ. Gay-Lussac
Correct Answer: Avogadro
Explanation: Amedeo Avogadro proposed that equal volumes of gases at the same temperature and pressure contain equal numbers of particles. This concept later led to the definition of the mole, involving Avogadro’s number $6.022 \times 10^{23}$.
4. Which of the following is the correct SI unit of amount of substance?
ⓐ. Gram
ⓑ. Mole
ⓒ. Atom
ⓓ. Liter
Correct Answer: Mole
Explanation: In the SI system, the mole is the unit for amount of substance. One mole corresponds to $6.022 \times 10^{23}$ particles (atoms, ions, or molecules). Grams measure mass, atoms are particles, and liters measure volume.
5. The law of conservation of mass was first proposed by:
ⓐ. J.J. Thomson
ⓑ. Lavoisier
ⓒ. Rutherford
ⓓ. Bohr
Correct Answer: Lavoisier
Explanation: Antoine Lavoisier, known as the “Father of Modern Chemistry,” proposed that mass can neither be created nor destroyed in a chemical reaction. This principle laid the foundation for chemical equations.
6. Which of the following is an extensive property?
ⓐ. Temperature
ⓑ. Pressure
ⓒ. Mass
ⓓ. Density
Correct Answer: Mass
Explanation: Extensive properties depend on the amount of substance (mass, volume, energy), while intensive properties (temperature, density, pressure) are independent of the amount of matter.
7. The SI unit of molar mass is:
ⓐ. kg
ⓑ. g/mol
ⓒ. kg/mol
ⓓ. mol/g
Correct Answer: kg/mol
Explanation: Molar mass is the mass of one mole of a substance. In SI units, it is expressed as kilograms per mole (kg/mol). However, in practice, chemists often use g/mol because molar masses are more convenient in grams.
8. Which of the following correctly represents 1 mole of oxygen gas?
ⓐ. 16 g of O₂
ⓑ. 32 g of O₂
ⓒ. 6.022 × 10²³ atoms of oxygen
ⓓ. 8 g of O₂
Correct Answer: 32 g of O₂
Explanation: Oxygen gas is diatomic (O₂). The molar mass is $2 \times 16 = 32 \, g/mol$. Thus, 1 mole of O₂ corresponds to 32 g and contains $6.022 \times 10^{23}$ molecules, not atoms.
9. Which law states: “When two elements combine to form two or more compounds, the masses of one element combining with a fixed mass of the other are in the ratio of small whole numbers”?
ⓐ. Law of conservation of mass
ⓑ. Law of definite proportions
ⓒ. Law of multiple proportions
ⓓ. Law of reciprocal proportions
Correct Answer: Law of multiple proportions
Explanation: Proposed by Dalton, this law explains how elements combine in whole-number ratios. For example, carbon and oxygen form CO (12:16) and CO₂ (12:32). The oxygen masses (16 and 32) are in the ratio 1:2.
10. A sample of calcium carbonate (CaCO₃) has a mass of 100 g. What is the number of moles present?
ⓐ. 1 mole
ⓑ. 0.5 mole
ⓒ. 2 moles
ⓓ. 10 moles
Correct Answer: 1 mole
Explanation: Molar mass of CaCO₃ = 40 (Ca) + 12 (C) + 48 (O) = 100 g/mol. Given mass = 100 g.
$\text{Moles} = \frac{\text{Mass}}{\text{Molar mass}} = \frac{100}{100} = 1 \, \text{mol}$.
11. Which chemical is commonly used as an artificial sweetener in food products?
ⓐ. Saccharin
ⓑ. Urea
ⓒ. Glucose
ⓓ. Fructose
Correct Answer: Saccharin
Explanation: Saccharin is a non-nutritive artificial sweetener, about 300 times sweeter than sucrose. Glucose and fructose are natural sugars, while urea is not used as a sweetener.
12. Which compound is the main active ingredient in common painkillers like aspirin?
ⓐ. Acetylsalicylic acid
ⓑ. Paracetamol
ⓒ. Ibuprofen
ⓓ. Citric acid
Correct Answer: Acetylsalicylic acid
Explanation: Aspirin is chemically acetylsalicylic acid. Paracetamol and ibuprofen are also pain relievers but belong to different drug classes. Citric acid is found in citrus fruits and not used as a medicine.
13. Which chemical is responsible for the preservation of food in pickles?
ⓐ. Sodium chloride
ⓑ. Sodium hydroxide
ⓒ. Potassium carbonate
ⓓ. Magnesium chloride
Correct Answer: Sodium chloride
Explanation: Salt (NaCl) preserves food by creating a hypertonic environment that prevents microbial growth. Other listed compounds do not have preservative properties for food.
14. Which of the following is used as an antacid to reduce acidity in the stomach?
ⓐ. Sodium bicarbonate
ⓑ. Sodium chloride
ⓒ. Calcium sulphate
ⓓ. Ammonium chloride
Correct Answer: Sodium bicarbonate
Explanation: Sodium bicarbonate (NaHCO₃) neutralizes excess hydrochloric acid in the stomach, providing relief from acidity. Other options do not act as antacids.
15. Which polymer is commonly used for making plastic bottles?
ⓐ. Polyvinyl chloride (PVC)
ⓑ. Polystyrene
ⓒ. Polyethylene terephthalate (PET)
ⓓ. Nylon
Correct Answer: Polyethylene terephthalate (PET)
Explanation: PET is a strong, lightweight, and recyclable polymer widely used for beverage bottles and food containers. PVC and polystyrene have other applications, while nylon is used for textiles.
16. Which chemical is commonly used as an octane booster in fuels?
ⓐ. Tetraethyl lead (TEL)
ⓑ. Sodium chloride
ⓒ. Potassium permanganate
ⓓ. Ammonia
Correct Answer: Tetraethyl lead (TEL)
Explanation: TEL was historically used to increase the octane rating of petrol and prevent engine knocking. However, due to toxicity, it is now phased out. The other compounds are unrelated to fuels.
17. Which gas is responsible for the carbonation in soft drinks?
ⓐ. Oxygen
ⓑ. Carbon dioxide
ⓒ. Nitrogen
ⓓ. Methane
Correct Answer: Carbon dioxide
Explanation: CO₂ is dissolved under pressure in soft drinks, giving them fizz and a tangy taste. Oxygen and nitrogen are not used for carbonation, while methane is a flammable fuel.
18. Which of the following is a natural antioxidant found in green tea?
ⓐ. Caffeine
ⓑ. Catechins
ⓒ. Saccharin
ⓓ. Tannic acid
Correct Answer: Catechins
Explanation: Catechins are polyphenolic antioxidants found in green tea, known for health benefits like reducing oxidative stress. Caffeine is a stimulant, saccharin is an artificial sweetener, and tannic acid has different uses.
19. Which chemical compound is responsible for the pungent smell of onions?
ⓐ. Allyl propyl disulfide
ⓑ. Methane
ⓒ. Ethanol
ⓓ. Acetic acid
Correct Answer: Allyl propyl disulfide
Explanation: Onions release allyl propyl disulfide when cut, which causes the characteristic smell and eye irritation. Methane is odorless, ethanol is alcohol, and acetic acid gives vinegar its smell.
20. Which of the following fuels is considered the cleanest source of energy?
ⓐ. Coal
ⓑ. Petroleum
ⓒ. Hydrogen
ⓓ. Diesel
Correct Answer: Hydrogen
Explanation: Hydrogen, when used as a fuel, produces only water as a byproduct and no carbon dioxide, making it a clean energy source. Coal, petroleum, and diesel release greenhouse gases and pollutants.
21. Which of the following best explains the relation of chemistry with physics?
ⓐ. Chemistry explains atomic structure using Newton’s laws.
ⓑ. Physics provides laws and models to understand chemical bonding and atomic behavior.
ⓒ. Physics only studies motion, not related to chemistry.
ⓓ. Chemistry and physics are completely independent.
Correct Answer: Physics provides laws and models to understand chemical bonding and atomic behavior.
Explanation: Chemistry and physics are deeply interconnected. Quantum mechanics from physics explains the structure of atoms and molecules, and thermodynamics explains energy changes in chemical reactions. For example, Schrödinger’s wave equation (physics) helps chemists predict molecular orbitals. Newton’s laws are limited to macroscopic objects, while atomic structure requires quantum theory. Hence, chemistry relies on physical principles for microscopic understanding.
22. Which branch of science integrates chemistry and biology to study processes such as enzyme action?
ⓐ. Biochemistry
ⓑ. Geochemistry
ⓒ. Pharmacology
ⓓ. Biophysics
Correct Answer: Biochemistry
Explanation: Biochemistry is the study of chemical processes in living organisms, such as metabolism, DNA replication, and enzyme action. For example, understanding how enzymes lower activation energy involves both chemical kinetics (chemistry) and biological function. Geochemistry studies Earth’s chemistry, pharmacology focuses on drugs, and biophysics applies physics to biology but not specifically to enzyme chemistry.
23. The role of chemistry in engineering is most clearly seen in which example?
ⓐ. Developing stronger alloys for construction.
ⓑ. Designing new mathematical models.
ⓒ. Observing planetary motion.
ⓓ. Writing computer algorithms.
Correct Answer: Developing stronger alloys for construction.
Explanation: Engineering uses chemistry extensively in materials science. For example, stainless steel (iron, carbon, chromium, nickel alloy) is engineered for strength and corrosion resistance. Chemical engineering also uses thermodynamics, kinetics, and catalysis for designing reactors. Options B and D belong to mathematics and computer science, while C belongs to physics and astronomy.
24. Which of the following shows chemistry’s role in understanding the environment?
ⓐ. Explaining Newton’s laws of motion
ⓑ. Studying acid rain formation due to SO₂ and NOx gases
ⓒ. Observing gravitational attraction of planets
ⓓ. Designing digital circuits
Correct Answer: Studying acid rain formation due to SO₂ and NOx gases
Explanation: Chemistry explains environmental problems at a molecular level. Sulphur dioxide (SO₂) and nitrogen oxides (NOx) dissolve in water to form sulphuric and nitric acids, leading to acid rain. This damages crops, buildings, and aquatic life. Physics explains planetary attraction, digital circuits involve electronics, while Newton’s laws are unrelated.
25. Which interdisciplinary area combines chemistry and physics for medical imaging technologies like MRI?
ⓐ. Physical chemistry
ⓑ. Nuclear chemistry
ⓒ. Biophysics
ⓓ. Radiochemistry
Correct Answer: Radiochemistry
Explanation: Radiochemistry and nuclear chemistry apply principles of both chemistry and physics. MRI and PET scans use isotopes and nuclear spin, requiring knowledge of quantum mechanics, magnetism, and isotopes. Physical chemistry deals with energy and bonding, biophysics studies biological physics, and radiochemistry specifically explains radioactive substances used in medicine.
26. Why is chemistry considered central among sciences?
ⓐ. Because it explains only living systems.
ⓑ. Because it connects physics, biology, geology, and environmental science.
ⓒ. Because it is completely separate from other sciences.
ⓓ. Because it focuses only on laboratory work.
Correct Answer: Because it connects physics, biology, geology, and environmental science.
Explanation: Chemistry is often called the “central science.” It connects physics (quantum models), biology (biochemical processes), geology (minerals, soil chemistry), and environmental science (pollution, climate chemistry). For example, photosynthesis is explained chemically (chlorophyll, CO₂ fixation), physically (light absorption), and biologically (plant growth).
27. Which of the following best describes chemistry’s link with biology in medicine?
ⓐ. Chemistry studies motion while biology studies life.
ⓑ. Chemistry explains the molecular basis of drugs and metabolism.
ⓒ. Biology depends on Newton’s laws, not chemistry.
ⓓ. Chemistry has no role in drug development.
Correct Answer: Chemistry explains the molecular basis of drugs and metabolism.
Explanation: Modern medicine relies on chemistry. Pharmacology uses organic and inorganic chemistry to design drugs that bind specific enzymes or receptors. For instance, penicillin inhibits bacterial cell wall synthesis at a chemical level. Without chemistry, the understanding of how drugs work inside the body would not be possible.
28. The Haber process for ammonia synthesis demonstrates chemistry’s role in which field?
ⓐ. Astronomy
ⓑ. Agriculture and industry
ⓒ. Computer science
ⓓ. History
Correct Answer: Agriculture and industry
Explanation: The Haber process uses N₂ and H₂ gases to produce NH₃, a vital component of fertilizers. This industrial-scale reaction is a clear example of chemistry supporting agriculture. Physics contributes pressure and temperature control, while chemistry provides catalysis and equilibrium theory. The other options are unrelated.
29. Which chemical principle helps engineers design batteries for electric vehicles?
ⓐ. Quantum mechanics
ⓑ. Electrochemistry
ⓒ. Thermodynamics
ⓓ. Nuclear fission
Correct Answer: Electrochemistry
Explanation: Electrochemistry, a branch of chemistry, explains how chemical reactions produce electricity. In electric vehicle batteries, lithium-ion movement between electrodes is based on redox reactions. Thermodynamics and quantum mechanics also play roles, but the key applied principle is electrochemistry. Nuclear fission is unrelated.
30. Which example shows chemistry’s role in climate studies?
ⓐ. Newton’s second law of motion
ⓑ. Bonding in CO₂ molecules and their infrared absorption
ⓒ. Calculating orbital speed of satellites
ⓓ. Designing microchips
Correct Answer: Bonding in CO₂ molecules and their infrared absorption
Explanation: Chemistry explains how CO₂ and other greenhouse gases absorb IR radiation due to vibrational modes of their molecular bonds. This traps heat and leads to global warming. Physics helps in energy transfer analysis, but molecular-level absorption is chemistry’s domain. Newton’s law, satellites, and microchips are unrelated.
31. Which branch of physics directly supports chemistry in explaining atomic orbitals?
ⓐ. Classical mechanics
ⓑ. Quantum mechanics
ⓒ. Thermodynamics
ⓓ. Electromagnetism
Correct Answer: Quantum mechanics
Explanation: Quantum mechanics explains the behavior of electrons in atoms, leading to the concept of orbitals, quantum numbers, and probability distributions. Chemistry uses these models to describe bonding and molecular structure. Classical mechanics cannot explain atomic stability, thermodynamics deals with energy, and electromagnetism describes charge interactions but not electron orbitals fully.
32. Which of the following processes demonstrates the combined role of chemistry and biology?
ⓐ. Photosynthesis in plants
ⓑ. Reflection of light in mirrors
ⓒ. Tides in the ocean
ⓓ. Sound propagation in air
Correct Answer: Photosynthesis in plants
Explanation: Photosynthesis is a biochemical process where chlorophyll absorbs sunlight (physics), converts it into chemical energy (chemistry), and produces glucose and oxygen (biology). It is a perfect example of interdisciplinary integration. Reflection, tides, and sound are purely physical phenomena.
33. Which engineering material is designed using chemical knowledge of polymers?
ⓐ. Concrete
ⓑ. Nylon
ⓒ. Steel
ⓓ. Glass
Correct Answer: Nylon
Explanation: Nylon is a synthetic polymer developed through organic chemistry. Its properties like strength, elasticity, and resistance make it useful in textiles and engineering applications. Concrete and glass are inorganic, while steel is a metal alloy, but nylon’s design is rooted in polymer chemistry.
34. Which atmospheric process is explained through chemistry?
ⓐ. Coriolis effect
ⓑ. Acid rain formation
ⓒ. Gravitational attraction
ⓓ. Seasons on Earth
Correct Answer: Acid rain formation
Explanation: Acid rain forms when SO₂ and NOx gases react with atmospheric water to produce H₂SO₄ and HNO₃. This is a chemical reaction explaining environmental pollution. Coriolis effect and gravity are physical phenomena, while seasons depend on Earth’s tilt and orbit.
35. The study of enzymes acting as catalysts in biochemical reactions is an overlap of:
ⓐ. Chemistry and physics
ⓑ. Chemistry and biology
ⓒ. Physics and geology
ⓓ. Engineering and astronomy
Correct Answer: Chemistry and biology
Explanation: Enzymes are biological catalysts that accelerate chemical reactions in cells. Their function can only be explained by combining biological processes with chemical reaction mechanisms (kinetics and catalysis). Physics and geology or engineering and astronomy have no direct link here.
36. Which concept of physics is essential to understand spectroscopy in chemistry?
ⓐ. Wave-particle duality
ⓑ. Ohm’s law
ⓒ. Hooke’s law
ⓓ. Law of inertia
Correct Answer: Wave-particle duality
Explanation: Spectroscopy involves the interaction of electromagnetic radiation with matter. Chemistry uses wave-particle duality from physics to explain absorption, emission, and quantum transitions in atoms. Ohm’s law (electric circuits), Hooke’s law (spring force), and inertia are unrelated.
37. The concept of alloys like brass and bronze shows the relation of chemistry with:
ⓐ. Physics and astronomy
ⓑ. Engineering and materials science
ⓒ. Geology and geography
ⓓ. Botany and zoology
Correct Answer: Engineering and materials science
Explanation: Alloys are chemical mixtures of metals (e.g., brass = Cu + Zn, bronze = Cu + Sn). Their design requires chemical knowledge of bonding and engineering knowledge of strength, hardness, and corrosion resistance. The other options are unrelated to alloy development.
38. Which environmental issue is directly related to chemical use of chlorofluorocarbons (CFCs)?
ⓐ. Global warming
ⓑ. Ozone layer depletion
ⓒ. Deforestation
ⓓ. Soil erosion
Correct Answer: Ozone layer depletion
Explanation: CFCs release chlorine atoms in the stratosphere, which catalytically destroy ozone molecules. This allows harmful UV radiation to reach Earth’s surface. While global warming also involves chemistry, CFCs are more directly responsible for ozone depletion.
39. Which branch of chemistry is most relevant for developing renewable energy technologies like solar cells?
ⓐ. Organic chemistry
ⓑ. Electrochemistry
ⓒ. Physical chemistry
ⓓ. Nuclear chemistry
Correct Answer: Electrochemistry
Explanation: Solar cells and fuel cells are based on redox reactions and electron transfer, which are explained by electrochemistry. Organic chemistry designs polymers for solar panels, but the direct principle is electrochemical. Nuclear chemistry deals with radioactivity and not solar energy.
40. The study of pollutants in rivers and their effect on aquatic life shows the connection of chemistry with:
ⓐ. Botany
ⓑ. Environmental science
ⓒ. Astronomy
ⓓ. Meteorology
Correct Answer: Environmental science
Explanation: Chemistry helps identify pollutants (like nitrates, phosphates, heavy metals) and explains their effects, such as eutrophication. Environmental science integrates this with ecology and conservation. Botany studies plants, astronomy studies celestial objects, and meteorology focuses on weather.
41. Which of the following chemicals is widely used in the fertilizer industry to enhance nitrogen content in soil?
ⓐ. Ammonium nitrate
ⓑ. Sodium chloride
ⓒ. Calcium carbonate
ⓓ. Potassium permanganate
Correct Answer: Ammonium nitrate
Explanation: Ammonium nitrate $(NH₄NO₃)$ is a nitrogen-rich fertilizer, boosting crop growth. Sodium chloride is common salt, calcium carbonate is used to neutralize acidic soil but not as a nitrogen fertilizer, and potassium permanganate is an oxidizing agent used in laboratories and water treatment.
42. The Haber process, an industrial application of equilibrium chemistry, is used to manufacture:
ⓐ. Methanol
ⓑ. Ammonia
ⓒ. Sulphuric acid
ⓓ. Nitric acid
Correct Answer: Ammonia
Explanation: The Haber process combines nitrogen and hydrogen under high pressure and temperature in the presence of an iron catalyst to produce ammonia. Ammonia is vital for fertilizers like urea. Methanol, sulphuric acid, and nitric acid are manufactured by other processes.
43. Which chemical process is the basis of the cement industry?
ⓐ. Haber process
ⓑ. Solvay process
ⓒ. Calcination of limestone
ⓓ. Electrolysis of brine
Correct Answer: Calcination of limestone
Explanation: Cement is produced by calcining limestone $(CaCO₃)$ to form quicklime $(CaO)$, which is further processed with silica and alumina. Solvay process produces sodium carbonate, electrolysis of brine gives chlorine and NaOH, and Haber process produces ammonia.
44. Which chemical is used in the agriculture industry as a pesticide?
ⓐ. DDT
ⓑ. Sodium bicarbonate
ⓒ. Glucose
ⓓ. Ethanol
Correct Answer: DDT
Explanation: Dichlorodiphenyltrichloroethane (DDT) is a synthetic pesticide used historically to control insects. Due to environmental hazards, its use is restricted now. Sodium bicarbonate is an antacid, glucose is a sugar, and ethanol is used as a solvent and fuel.
45. Which technology relies on the semiconductor properties of silicon, discovered through chemical purification?
ⓐ. Computers and microchips
ⓑ. Textile dyeing
ⓒ. Food preservation
ⓓ. Paper making
Correct Answer: Computers and microchips
Explanation: Silicon wafers are purified and doped chemically to create semiconductors used in computers, mobiles, and microchips. This is a classic example of chemistry’s role in modern technology. The other options do not rely on semiconductor chemistry.
46. The Solvay process is used in the chemical industry to produce:
ⓐ. Sodium carbonate
ⓑ. Ammonia
ⓒ. Sulphuric acid
ⓓ. Potassium hydroxide
Correct Answer: Sodium carbonate
Explanation: The Solvay process uses sodium chloride, ammonia, and carbon dioxide to produce sodium carbonate (soda ash), an important raw material for glass, detergents, and paper industries. The other chemicals are manufactured by different processes.
47. Which fertilizer provides both nitrogen and phosphorus to crops?
ⓐ. Urea
ⓑ. Ammonium nitrate
ⓒ. Superphosphate of lime
ⓓ. Diammonium phosphate
Correct Answer: Diammonium phosphate
Explanation: Diammonium phosphate (DAP) contains nitrogen and phosphorus, making it a balanced fertilizer. Urea and ammonium nitrate supply only nitrogen, while superphosphate mainly provides phosphorus.
48. In the steel industry, chemistry is crucial for:
ⓐ. Designing building maps
ⓑ. Converting iron ore to steel by controlling carbon content
ⓒ. Explaining gravitational forces
ⓓ. Studying DNA structures
Correct Answer: Converting iron ore to steel by controlling carbon content
Explanation: Steel is produced by reducing iron ore and carefully adjusting carbon and alloy content. Chemistry explains oxidation-reduction processes in blast furnaces and alloy design. The other options are not related to steel production.
49. Which of the following is an industrial use of sulphuric acid, often called the “king of chemicals”?
ⓐ. Used in petroleum refining and fertilizers
ⓑ. Used as a sweetener
ⓒ. Used as a food preservative
ⓓ. Used as a dye in clothes
Correct Answer: Used in petroleum refining and fertilizers
Explanation: Sulphuric acid is one of the most widely used chemicals in industries. It is used in fertilizer production (superphosphates, ammonium sulphate), petroleum refining, dyes, and chemical synthesis. The other options are incorrect.
50. Which of the following shows chemistry’s importance in modern agriculture?
ⓐ. Use of genetically modified seeds only
ⓑ. Application of chemical fertilizers, pesticides, and herbicides
ⓒ. Building irrigation canals
ⓓ. Observing crop patterns from satellites
Correct Answer: Application of chemical fertilizers, pesticides, and herbicides
Explanation: Chemistry provides fertilizers (urea, ammonium salts), pesticides (DDT, malathion), and herbicides that enhance crop yield and protect plants. Irrigation and satellite observation belong to engineering and physics but not directly to chemistry.
51. Who is credited with proposing the Law of Conservation of Mass?
ⓐ. John Dalton
ⓑ. Antoine Lavoisier
ⓒ. Robert Boyle
ⓓ. Joseph Proust
Correct Answer: Antoine Lavoisier
Explanation: Antoine Lavoisier, known as the “Father of Modern Chemistry,” proposed in 1789 that mass is neither created nor destroyed during a chemical reaction. Dalton proposed atomic theory, Boyle studied gases, and Proust introduced the law of definite proportions.
52. According to the Law of Conservation of Mass, in a chemical reaction:
ⓐ. Mass of products is always greater than reactants
ⓑ. Mass of products is always less than reactants
ⓒ. Mass of reactants equals mass of products
ⓓ. Mass is created during reaction
Correct Answer: Mass of reactants equals mass of products
Explanation: The law states that the total mass of substances before and after a chemical reaction remains the same. Atoms are simply rearranged, not created or destroyed. Options A, B, and D contradict this principle.
53. Which of the following reactions best demonstrates the Law of Conservation of Mass?
ⓐ. Burning of magnesium in air forming MgO
ⓑ. Growth of plants
ⓒ. Photosynthesis
ⓓ. All of the above
Correct Answer: All of the above
Explanation: In burning magnesium, the mass of Mg and O₂ equals the mass of MgO formed. In photosynthesis, the combined mass of CO₂ and H₂O equals the mass of glucose and oxygen formed. Even in plant growth, matter is conserved, though transformations occur.
54. In a reaction, 5 g of calcium reacts with 2 g of oxygen to form calcium oxide. The mass of CaO produced will be:
ⓐ. 2 g
ⓑ. 5 g
ⓒ. 7 g
ⓓ. Cannot be predicted
Correct Answer: 7 g
Explanation: According to the Law of Conservation of Mass, mass of products = mass of reactants. Hence, CaO = 5 g (Ca) + 2 g (O₂) = 7 g.
55. In a closed system, 10 g of hydrogen reacts with 80 g of oxygen. What will be the total mass of water formed?
ⓐ. 80 g
ⓑ. 10 g
ⓒ. 70 g
ⓓ. 90 g
Correct Answer: 90 g
Explanation: Mass of reactants = 10 g + 80 g = 90 g. By conservation of mass, the mass of water produced will also be 90 g. None of the other values are consistent with this law.
56. Which experiment did Lavoisier perform to establish the Law of Conservation of Mass?
ⓐ. Heating mercury oxide to form mercury and oxygen
ⓑ. Electrolysis of water
ⓒ. Reaction of hydrogen with chlorine
ⓓ. Dissolving salt in water
Correct Answer: Heating mercury oxide to form mercury and oxygen
Explanation: Lavoisier showed that when HgO decomposed into Hg and O₂, the total mass remained constant. This experiment became the foundation of the conservation principle.
57. The Law of Conservation of Mass is not strictly valid in:
ⓐ. Physical changes
ⓑ. Chemical reactions at normal speeds
ⓒ. Nuclear reactions
ⓓ. Combustion reactions
Correct Answer: Nuclear reactions
Explanation: In nuclear reactions, a small part of mass is converted into energy according to Einstein’s equation $E = mc^2$. Therefore, the law of conservation of mass holds true for ordinary chemical and physical changes but not for nuclear reactions.
58. Which of the following correctly explains why mass is conserved in chemical reactions?
ⓐ. Atoms are destroyed in reactions.
ⓑ. Atoms are rearranged but not created or destroyed.
ⓒ. Atoms are created during reactions.
ⓓ. Atoms vanish in the product state.
Correct Answer: Atoms are rearranged but not created or destroyed.
Explanation: During chemical reactions, atoms simply rearrange to form new bonds. Since the number and type of atoms remain constant, mass is conserved. Creation or destruction of atoms does not occur in chemical processes.
59. In an experiment, 10 g of a hydrocarbon is completely burnt in oxygen to form 30 g of CO₂ and 9 g of H₂O. What is the mass of oxygen consumed?
ⓐ. 39 g
ⓑ. 29 g
ⓒ. 19 g
ⓓ. 10 g
Correct Answer: 29 g
Explanation: Mass of products = 30 + 9 = 39 g. Mass of hydrocarbon = 10 g. Hence, oxygen consumed = 39 – 10 = 29 g, proving conservation of mass.
60. Why is the Law of Conservation of Mass fundamental to balancing chemical equations?
ⓐ. It ensures charge balance.
ⓑ. It ensures equal mass of reactants and products.
ⓒ. It ensures reactions are spontaneous.
ⓓ. It ensures heat loss is minimum.
Correct Answer: It ensures equal mass of reactants and products.
Explanation: Chemical equations are balanced to obey the conservation of mass. Each side must contain the same number of atoms of each element, ensuring the mass remains equal before and after the reaction. This principle underlies all stoichiometric calculations.
61. Who proposed the Law of Definite Proportions?
ⓐ. Antoine Lavoisier
ⓑ. Joseph Proust
ⓒ. John Dalton
ⓓ. J.J. Thomson
Correct Answer: Joseph Proust
Explanation: Joseph Proust proposed the Law of Definite Proportions in 1799. He stated that a chemical compound always contains the same elements in the same fixed proportion by mass, regardless of its source or method of preparation.
62. The Law of Definite Proportions states that:
ⓐ. Mass can neither be created nor destroyed.
ⓑ. A given compound always contains the same elements in the same ratio by mass.
ⓒ. Compounds combine in whole number ratios by volume.
ⓓ. The masses of one element combine with a fixed mass of another in small whole numbers.
Correct Answer: A given compound always contains the same elements in the same ratio by mass.
Explanation: This law states that a pure chemical compound has a definite composition by mass. For example, water always contains hydrogen and oxygen in the ratio 1:8 by mass. Options A, C, and D describe other laws of chemical combination.
63. Which compound is often cited as an example of the Law of Definite Proportions?
ⓐ. Ammonia (NH₃)
ⓑ. Water (H₂O)
ⓒ. Ozone (O₃)
ⓓ. Hydrogen gas (H₂)
Correct Answer: Water (H₂O)
Explanation: Water always contains hydrogen and oxygen in the fixed ratio of 1:8 by mass. Regardless of the source (rain, river, distilled), the composition remains constant. Ammonia also follows this law but water is the classic example.
64. In carbon dioxide (CO₂), the mass ratio of carbon to oxygen is:
ⓐ. 1:2
ⓑ. 3:4
ⓒ. 12:32
ⓓ. 12:16
Correct Answer: 12:32
Explanation: In CO₂, one atom of carbon (12 g) combines with two atoms of oxygen (32 g). Thus, the ratio is 12:32 or 3:8 by mass. This remains constant in all samples of CO₂, proving Proust’s law.
65. Which of the following compounds does not obey the Law of Definite Proportions strictly?
ⓐ. Water
ⓑ. Carbon dioxide
ⓒ. Sodium chloride
ⓓ. Non-stoichiometric compounds (e.g., FeO)
Correct Answer: Non-stoichiometric compounds (e.g., FeO)
Explanation: Non-stoichiometric compounds do not have a fixed ratio of elements due to defects in crystal structures. For example, iron oxide may have composition ranging from Fe₀.93O to Fe₀.98O. Water, CO₂, and NaCl obey the law strictly.
66. A sample of CO₂ obtained from coal combustion contains 27.3% carbon and 72.7% oxygen. Another sample of CO₂ from fermentation contains 27.3% carbon and 72.7% oxygen. This confirms:
ⓐ. Law of multiple proportions
ⓑ. Law of conservation of mass
ⓒ. Law of definite proportions
ⓓ. Dalton’s atomic theory
Correct Answer: Law of definite proportions
Explanation: Both samples of CO₂ have identical composition by mass (C\:O = 27.3:72.7), irrespective of their origin. This is exactly what Proust’s law states.
67. Which statement is true regarding the Law of Definite Proportions?
ⓐ. It is valid for all pure compounds.
ⓑ. It is not applicable to chemical reactions.
ⓒ. It states that compounds always form in equal volumes.
ⓓ. It was proposed by John Dalton.
Correct Answer: It is valid for all pure compounds.
Explanation: Proust’s law applies to all pure chemical compounds, whether naturally occurring or synthesized. It is not related to volume (that’s Gay-Lussac’s law), nor was it proposed by Dalton (he gave atomic theory).
68. Which experimental evidence supported Proust’s Law?
ⓐ. Mercury oxide always decomposes to Hg and O₂ in the same ratio.
ⓑ. Nitrogen combines with oxygen in different ratios forming NO and NO₂.
ⓒ. Equal volumes of gases contain equal number of molecules.
ⓓ. Mass is conserved during reactions.
Correct Answer: Mercury oxide always decomposes to Hg and O₂ in the same ratio.
Explanation: Experiments with mercury oxide showed that it always decomposes into mercury and oxygen in the same mass ratio, regardless of how it was prepared. This strongly supported Proust’s law.
69. In a sample of water, the ratio of hydrogen to oxygen atoms is always:
ⓐ. 2:1
ⓑ. 1:2
ⓒ. 1:8
ⓓ. 8:1
Correct Answer: 2:1
Explanation: Water always has 2 hydrogen atoms and 1 oxygen atom. By mass, the ratio is 1:8 (since oxygen is heavier), but atomically the ratio is fixed at 2:1. This constant composition proves Proust’s law.
70. Why is the Law of Definite Proportions important in chemistry?
ⓐ. It led to the concept of relative atomic masses.
ⓑ. It proved that atoms exist as indivisible particles.
ⓒ. It explained the conservation of energy.
ⓓ. It introduced the concept of molecular speeds.
Correct Answer: It led to the concept of relative atomic masses.
Explanation: Since compounds always contain elements in fixed proportions, chemists deduced that elements combine in fixed atomic ratios. This paved the way for calculating relative atomic and molecular masses, a cornerstone of modern chemistry.
71. Who proposed the Law of Multiple Proportions?
ⓐ. Joseph Proust
ⓑ. Antoine Lavoisier
ⓒ. John Dalton
ⓓ. Robert Boyle
Correct Answer: John Dalton
Explanation: John Dalton, in 1803, proposed the Law of Multiple Proportions as part of his Atomic Theory. He explained that when two elements form more than one compound, the masses of one element combining with a fixed mass of the other are in ratios of small whole numbers.
72. Which of the following best illustrates the Law of Multiple Proportions?
ⓐ. H₂O and H₂O₂
ⓑ. NaCl and KCl
ⓒ. CO and CO₂
ⓓ. Both A and C
Correct Answer: Both A and C
Explanation: In H₂O and H₂O₂, the ratio of oxygen masses is 1:2 for the same mass of hydrogen. In CO and CO₂, the oxygen mass ratio is 16:32 = 1:2 for the same mass of carbon. Both cases show small whole-number ratios, proving Dalton’s law.
73. According to the Law of Multiple Proportions, the ratios must always be:
ⓐ. Fractional numbers
ⓑ. Large numbers
ⓒ. Small whole numbers
ⓓ. Irrational numbers
Correct Answer: Small whole numbers
Explanation: Dalton’s law clearly states that the masses of one element combining with a fixed mass of another element are in small whole-number ratios. Examples include 1:2, 2:3, but never fractions or irrational numbers.
74. Which of the following pairs of compounds does not follow the Law of Multiple Proportions?
ⓐ. CO and CO₂
ⓑ. NO and NO₂
ⓒ. SO₂ and SO₃
ⓓ. NaCl and NaBr
Correct Answer: NaCl and NaBr
Explanation: NaCl and NaBr are different compounds but involve different elements (Cl and Br). Dalton’s law applies only when the same two elements form more than one compound, like CO/CO₂, NO/NO₂, SO₂/SO₃.
75. In CO and CO₂, 12 g of carbon combines with 16 g and 32 g of oxygen, respectively. The ratio of masses of oxygen combining with the same mass of carbon is:
ⓐ. 1:1
ⓑ. 1:2
ⓒ. 2:3
ⓓ. 3:4
Correct Answer: 1:2
Explanation: In CO, 12 g C combines with 16 g O. In CO₂, 12 g C combines with 32 g O. Ratio = 16:32 = 1:2. This simple whole-number ratio validates Dalton’s law.
76. In NO and NO₂, 14 g of nitrogen combines with 16 g and 32 g of oxygen, respectively. The ratio of masses of oxygen is:
ⓐ. 2:3
ⓑ. 1:2
ⓒ. 7:16
ⓓ. 3:4
Correct Answer: 1:2
Explanation: For NO, 14 g N combines with 16 g O. For NO₂, 14 g N combines with 32 g O. Ratio = 16:32 = 1:2, a small whole number ratio, proving Dalton’s law.
77. Which experimental evidence supports Dalton’s Law of Multiple Proportions?
ⓐ. Water and hydrogen peroxide composition
ⓑ. Nitrogen oxides (NO, NO₂, N₂O₃, N₂O₅)
ⓒ. Carbon monoxide and carbon dioxide composition
ⓓ. All of the above
Correct Answer: All of the above
Explanation: All these examples show fixed mass of one element combining with varying masses of the other in small whole-number ratios. This universal validity confirms Dalton’s law.
78. Which statement best describes the Law of Multiple Proportions?
ⓐ. Atoms are indivisible particles.
ⓑ. Equal volumes of gases contain equal molecules.
ⓒ. Elements combine in simple ratios by mass when forming multiple compounds.
ⓓ. Mass is conserved during reactions.
Correct Answer: Elements combine in simple ratios by mass when forming multiple compounds.
Explanation: This is the direct statement of Dalton’s law. Options A, B, and D refer to atomic theory, Avogadro’s law, and conservation of mass, respectively.
79. Two oxides of nitrogen contain 30 g of nitrogen each. In one, oxygen is 34.3 g, and in the other, oxygen is 68.6 g. The ratio of masses of oxygen combining with nitrogen is:
ⓐ. 1:1
ⓑ. 1:2
ⓒ. 2:3
ⓓ. 1:3
Correct Answer: 1:2
Explanation: For the same nitrogen mass, oxygen is 34.3 g and 68.6 g. Ratio = 34.3:68.6 = 1:2. This whole-number ratio proves Dalton’s law.
80. Why is the Law of Multiple Proportions important in chemistry?
ⓐ. It helped establish the existence of protons.
ⓑ. It gave strong evidence for Dalton’s Atomic Theory.
ⓒ. It introduced the concept of isotopes.
ⓓ. It explained the conservation of mass.
Correct Answer: It gave strong evidence for Dalton’s Atomic Theory.
Explanation: Dalton’s law showed that elements combine in fixed whole-number ratios, which is only possible if matter is made up of indivisible particles (atoms). This law strongly supported the atomic theory of matter.
81. Who proposed the Law of Reciprocal Proportions?
ⓐ. John Dalton
ⓑ. Antoine Lavoisier
ⓒ. Joseph Proust
ⓓ. Jeremias Benjamin Richter
Correct Answer: Jeremias Benjamin Richter
Explanation: The Law of Reciprocal Proportions was proposed by J.B. Richter in 1792. He showed that if two elements combine separately with a fixed mass of a third element, then the ratio of the masses in which they combine with each other is either the same or a simple multiple.
82. The Law of Reciprocal Proportions states that:
ⓐ. Mass is neither created nor destroyed.
ⓑ. A compound always contains the same proportion of elements.
ⓒ. Elements combine in simple whole-number ratios with a third element.
ⓓ. Equal volumes of gases contain equal numbers of molecules.
Correct Answer: Elements combine in simple whole-number ratios with a third element.
Explanation: According to Richter’s law, when two elements combine separately with a fixed mass of a third element, the masses in which they combine with each other are either the same or simple multiples.
83. Which set of compounds illustrates the Law of Reciprocal Proportions?
ⓐ. H₂O, CO₂, CH₄
ⓑ. H₂O, H₂S, SO₂
ⓒ. NaCl, KCl, MgCl₂
ⓓ. CO, CO₂, NO
Correct Answer: H₂O, H₂S, SO₂
Explanation: Oxygen and sulphur separately combine with hydrogen forming H₂O and H₂S. Oxygen and sulphur also combine with each other forming SO₂. The ratio of masses of oxygen and sulphur in SO₂ corresponds to the ratio observed in their compounds with hydrogen, thus verifying Richter’s law.
84. In H₂O, 2 g of hydrogen combines with 16 g of oxygen. In H₂S, 2 g of hydrogen combines with 32 g of sulphur. According to Richter’s law, the ratio of masses of oxygen and sulphur that combine with each other should be:
ⓐ. 16:32
ⓑ. 1:1
ⓒ. 2:1
ⓓ. 1:2
Correct Answer: 16:32
Explanation: Hydrogen is the common element. In H₂O, O\:H = 16:2, in H₂S, S\:H = 32:2. Hence O\:S = 16:32 = 1:2. When O and S form SO₂, the O\:S ratio is also 32:32 = 1:1, which is a simple multiple of 1:2, confirming Richter’s law.
85. Which of the following laws is directly supported by the Law of Reciprocal Proportions?
ⓐ. Law of conservation of mass
ⓑ. Dalton’s Atomic Theory
ⓒ. Avogadro’s law
ⓓ. Law of gaseous volumes
Correct Answer: Dalton’s Atomic Theory
Explanation: Dalton’s Atomic Theory assumes that atoms combine in simple whole-number ratios. The Law of Reciprocal Proportions confirms this idea by showing that elements combine consistently when linked through a common element.
86. Which element pair and common element verify the Law of Reciprocal Proportions?
ⓐ. Carbon, oxygen, hydrogen
ⓑ. Nitrogen, oxygen, hydrogen
ⓒ. Sodium, chlorine, oxygen
ⓓ. Calcium, magnesium, sulphur
Correct Answer: Nitrogen, oxygen, hydrogen
Explanation: Nitrogen and oxygen each combine with hydrogen to form NH₃ and H₂O, respectively. They also combine with each other to form NO, NO₂, etc. The mass ratios of oxygen and nitrogen in these compounds reflect the law of reciprocal proportions.
87. In NH₃, 14 g of nitrogen combines with 3 g of hydrogen. In H₂O, 16 g of oxygen combines with 2 g of hydrogen. If nitrogen and oxygen combine to form NO, the ratio of oxygen to nitrogen is:
ⓐ. 16:14
ⓑ. 8:7
ⓒ. 1:1
ⓓ. 14:16
Correct Answer: 16:14
Explanation: From NH₃, N\:H = 14:3. From H₂O, O\:H = 16:2 = 8:1. Thus O\:N = (8/1)/(14/3) = 24:14 ≈ 16:14. This ratio corresponds to NO formation, validating Richter’s law.
88. Why was the Law of Reciprocal Proportions important historically?
ⓐ. It introduced the concept of isotopes.
ⓑ. It provided support for atomic theory before atoms were widely accepted.
ⓒ. It explained radioactive decay.
ⓓ. It proved mass-energy equivalence.
Correct Answer: It provided support for atomic theory before atoms were widely accepted.
Explanation: Before Dalton’s Atomic Theory gained full acceptance, Richter’s law gave evidence that elements combine in consistent, predictable ratios, suggesting the existence of indivisible particles (atoms).
89. Which modern concept can be seen as a direct extension of the Law of Reciprocal Proportions?
ⓐ. Mole concept
ⓑ. Quantum mechanics
ⓒ. Periodic law
ⓓ. Conservation of energy
Correct Answer: Mole concept
Explanation: The mole concept extends Richter’s observations by quantifying exact numbers of atoms and molecules. It allows chemists to explain why elements combine in fixed ratios, giving precise numerical values to reciprocal mass relations.
90. Which of the following combinations does NOT illustrate the Law of Reciprocal Proportions?
ⓐ. H₂O, H₂S, SO₂
ⓑ. CO₂, H₂O, CH₄
ⓒ. NO, H₂O, NH₃
ⓓ. CaO, HCl, CaCl₂
Correct Answer: CaO, HCl, CaCl₂
Explanation: In CaO, HCl, and CaCl₂, chlorine and oxygen do not show reciprocal mass relationships through a common element. The other sets involve pairs of elements (like O, H, S or N, H, O) linked through hydrogen, illustrating Richter’s law.
91. Who proposed the Law of Gaseous Volumes?
ⓐ. Joseph Proust
ⓑ. Gay-Lussac
ⓒ. Antoine Lavoisier
ⓓ. John Dalton
Correct Answer: Gay-Lussac
Explanation: Gay-Lussac proposed the Law of Gaseous Volumes in 1808. He stated that when gases react together, they do so in simple whole-number ratios by volume, provided all gases are measured at the same temperature and pressure.
92. The Law of Gaseous Volumes applies only to:
ⓐ. Liquids
ⓑ. Solids
ⓒ. Gases under identical conditions of temperature and pressure
ⓓ. Mixtures of solids and liquids
Correct Answer: Gases under identical conditions of temperature and pressure
Explanation: The law is specific to gases, which are compressible and expandable. Their volumes must be measured at the same temperature and pressure to ensure a valid simple whole-number ratio.
93. In the reaction: $\text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl}$ the ratio of volumes of hydrogen, chlorine, and hydrogen chloride is:
ⓐ. 1:1:1
ⓑ. 1:2:2
ⓒ. 1:1:2
ⓓ. 2:1:2
Correct Answer: 1:1:2
Explanation: One volume of hydrogen combines with one volume of chlorine to form two volumes of HCl. This perfectly illustrates Gay-Lussac’s law of simple volume ratios.
94. When 2 volumes of hydrogen combine with 1 volume of oxygen, the product formed is:
ⓐ. 1 volume of water vapour
ⓑ. 2 volumes of water vapour
ⓒ. 3 volumes of water vapour
ⓓ. 4 volumes of water vapour
Correct Answer: 2 volumes of water vapour
Explanation: The balanced equation is $2H_2 + O_2 \rightarrow 2H_2O$. Thus, 2 volumes of H₂ combine with 1 volume of O₂ to form 2 volumes of water vapour, showing simple whole-number ratios.
95. Which reaction verifies Gay-Lussac’s Law?
ⓐ. $N_2 + 3H_2 \rightarrow 2NH_3$
ⓑ. $2Mg + O_2 \rightarrow 2MgO$
ⓒ. $CaCO_3 \rightarrow CaO + CO_2$
ⓓ. $NaOH + HCl \rightarrow NaCl + H_2O$
Correct Answer: $N_2 + 3H_2 \rightarrow 2NH_3$
Explanation: In this gaseous reaction, 1 volume of nitrogen combines with 3 volumes of hydrogen to form 2 volumes of ammonia. Options B, C, and D involve solids or liquids and are not applicable to Gay-Lussac’s law.
96. In the reaction of carbon monoxide and oxygen: $2CO + O_2 \rightarrow 2CO_2$, the volume ratio of CO : O₂ : CO₂ is:
ⓐ. 2:1:2
ⓑ. 1:2:2
ⓒ. 1:1:2
ⓓ. 2:2:1
Correct Answer: 2:1:2
Explanation: Two volumes of CO combine with one volume of O₂ to produce two volumes of CO₂. The ratio 2:1:2 follows the law of simple volumes.
97. Gay-Lussac’s law of gaseous volumes was one of the foundations for which later concept?
ⓐ. Dalton’s atomic theory
ⓑ. Avogadro’s hypothesis
ⓒ. Law of conservation of mass
ⓓ. Quantum theory
Correct Answer: Avogadro’s hypothesis
Explanation: Gay-Lussac’s observations of simple volume ratios could only be explained if equal volumes of gases under identical conditions contain equal numbers of molecules. This was later proposed by Avogadro.
98. Which condition is necessary to apply Gay-Lussac’s Law of Gaseous Volumes correctly?
ⓐ. The gases must be liquids first.
ⓑ. The gases must be measured at the same T and P.
ⓒ. The gases must be measured at different pressures.
ⓓ. The gases must be measured as solids.
Correct Answer: The gases must be measured at the same T and P.
Explanation: Since gases expand and contract with temperature and pressure, volume ratios are only meaningful when compared at identical conditions.
99. In the synthesis of ammonia: $\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3$, if 10 L of nitrogen is used, what volume of hydrogen is required at STP?
ⓐ. 20 L
ⓑ. 30 L
ⓒ. 40 L
ⓓ. 10 L
Correct Answer: 30 L
Explanation: Volume ratio N₂\:H₂ = 1:3. If 10 L N₂ is taken, hydrogen required = $10 \times 3 = 30 \, L$.
100. Which statement best summarizes Gay-Lussac’s Law of Gaseous Volumes?
ⓐ. Equal volumes of gases contain equal numbers of molecules.
ⓑ. The masses of elements combine in fixed ratios.
ⓒ. Gases combine in simple whole-number ratios by volume under constant T and P.
ⓓ. Mass can neither be created nor destroyed.
Correct Answer: Gases combine in simple whole-number ratios by volume under constant T and P.
Explanation: This is the direct statement of Gay-Lussac’s law. Option A is Avogadro’s hypothesis, B is Proust’s law of definite proportions, and D is Lavoisier’s law of conservation of mass.
Welcome to Class 11 Chemistry MCQs – Chapter 1: Some Basic Concepts of Chemistry (Part 1). This chapter is the true foundation of NCERT/CBSE Class 11 Chemistry and one of the most crucial units for both Board examinations and competitive entrance exams like JEE Main, JEE Advanced, NEET, and state-level tests. It introduces the building blocks of chemical science—concepts without which higher-level physical, inorganic, and organic chemistry cannot be mastered. Practicing these MCQs will give you crystal-clear command over theory and numericals, speed up your problem-solving, and boost your confidence for exams.
These Chemistry MCQs are equally useful for international students and competitive exams worldwide, since the fundamentals of Chemistry remain universal.
Navigation & pages: The complete set contains 394 MCQs divided into 4 parts (100 + 100 + 100 + 94). Part 1 includes the first 100 MCQs, further arranged into 10 pages with 10 questions per page. Use the page numbers above to move through the questions smoothly, and the Part buttons above to continue with later sets.
What you will learn & practice
- Importance of Chemistry and its role in science and daily life
- Atoms, molecules, and their relationship with measurable quantities
- Laws of chemical combination (Law of Conservation of Mass, Law of Definite Proportions, Law of Multiple Proportions, Gay-Lussac’s Law, Avogadro’s Law)
- Dalton’s atomic theory and modern insights into matter
- Atomic and molecular masses and methods of calculation
- Mole concept, molar mass, and use of Avogadro’s number
- Percentage composition of elements in a compound
- Empirical and molecular formula calculations
- Stoichiometry and stoichiometric coefficients
- Limiting reagent concept and its role in determining product formation
- Numerical problems on mass–mass, mass–volume, and volume–volume relations
- Theoretical yield vs actual yield and related calculations
How this practice works
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Real value: These MCQs are tightly aligned with the NCERT/CBSE Class 11 Chemistry syllabus, based on previous-year question trends and supported by clear, exam-focused explanations. Perfect for one-mark questions, practice quizzes, conceptual checks, and last-minute revision.
The full chapter contains 394 solved Chemistry multiple-choice questions in 4 structured parts. This page (Part 1) presents the first 100 MCQs with detailed answers and explanations to strengthen your basics. Explore more with: Class 11 Chemistry – Chapter Index, Class 11 – Subject Index, All Classes – MCQ Library.
- 👉 Total MCQs in this chapter: 394 (100 + 100 + 100 + 94)
- 👉 This page: first 100 multiple-choice questions with answers & explanations (in 10 pages)
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FAQs on Some Basic Concepts of Chemistry ▼
▸ What are Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry MCQs?
These are multiple-choice questions from NCERT Class 11 Chemistry Chapter 1 – Some Basic Concepts of Chemistry. They include important topics like mole concept, atomic mass, molar mass, stoichiometry, empirical and molecular formulas, and limiting reagent.
▸ How many MCQs are available in this chapter?
There are a total of 394 MCQs divided into 4 sets – three sets of 100 questions each and one set of 94 questions. Each question includes correct answers with explanations.
▸ Are these Chemistry MCQs useful for NCERT and CBSE board exams?
Yes, these MCQs strictly follow the NCERT/CBSE Class 11 Chemistry syllabus and are highly useful for state boards and CBSE board exams to improve accuracy and confidence.
▸ Are these MCQs important for competitive exams like JEE and NEET?
Yes, Chapter 1 is very important for JEE and NEET. The mole concept, stoichiometry, and limiting reagent are frequently asked in competitive exams, making these MCQs highly relevant.
▸ Do these MCQs include correct answers and explanations?
Yes, every MCQ is provided with the correct answer along with explanations wherever required. This helps students understand both concepts and problem-solving methods effectively.
▸ Who should practice Chapter 1 Chemistry MCQs?
These MCQs are designed for Class 11 students, CBSE/state board exam aspirants, and candidates preparing for competitive exams like JEE, NEET, NDA, UPSC, and other entrance tests.
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Yes, practicing these MCQs regularly helps in quick revision, strengthens memory recall, and improves exam performance in both board and competitive tests by enhancing speed and accuracy.
▸ Do these MCQs cover both basics and advanced concepts?
Yes, these MCQs cover everything from basics like laws of chemical combination and atomic mass to advanced topics like stoichiometric calculations and limiting reagent problems.
▸ What subtopics are included in Some Basic Concepts of Chemistry MCQs?
The MCQs cover subtopics such as mole concept, molar mass, laws of chemical combination, empirical and molecular formulas, stoichiometry, and numerical problems based on chemical equations.
▸ Why are the 394 MCQs divided into 4 parts?
The MCQs are divided into 4 parts to make practice more systematic and manageable, allowing students to study step by step and track progress easily.
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Yes, teachers and coaching centers can use these MCQs as ready-made assignments, quizzes, and practice sets for students preparing for board and entrance exams.
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