Timer: Off
Random: Off
101. Who proposed Avogadro’s Hypothesis?
ⓐ. John Dalton
ⓑ. Amedeo Avogadro
ⓒ. Antoine Lavoisier
ⓓ. Joseph Proust
Correct Answer: Amedeo Avogadro
Explanation: In 1811, Amedeo Avogadro proposed that equal volumes of gases under the same conditions of temperature and pressure contain equal numbers of molecules. This hypothesis helped resolve conflicts between Dalton’s atomic theory and Gay-Lussac’s law of gaseous volumes.
102. Avogadro’s Hypothesis states that:
ⓐ. Equal masses of gases contain equal numbers of molecules.
ⓑ. Equal volumes of gases contain equal masses at the same pressure.
ⓒ. Equal volumes of gases at any condition contain equal masses.
ⓓ. Equal volumes of gases at STP contain equal numbers of molecules.
Correct Answer: Equal volumes of gases at STP contain equal numbers of molecules.
Explanation: The hypothesis applies to gases measured under identical conditions of temperature and pressure, not mass. Equal masses do not necessarily mean equal numbers of molecules.
103. According to Avogadro’s Hypothesis, 22.4 L of any gas at STP contains:
ⓐ. $6.022 \times 10^{20}$ molecules
ⓑ. 1 g of molecules
ⓒ. $6.022 \times 10^{23}$ molecules
ⓓ. 1 atom of molecules
Correct Answer: $6.022 \times 10^{23}$ molecules
Explanation: One mole of a gas at STP (0°C and 1 atm) occupies 22.4 L. By Avogadro’s law, this volume contains Avogadro’s number of molecules, i.e., $6.022 \times 10^{23}$.
104. Which experiment supported Avogadro’s Hypothesis?
ⓐ. Rutherford’s gold foil experiment
ⓑ. Gay-Lussac’s law of combining volumes
ⓒ. Lavoisier’s mass conservation experiment
ⓓ. Thomson’s cathode ray experiment
Correct Answer: Gay-Lussac’s law of combining volumes
Explanation: Gay-Lussac showed gases combine in simple volume ratios. Avogadro explained this by suggesting that equal volumes of gases contain equal numbers of molecules. The other experiments are unrelated.
105. Which of the following provides direct evidence for Avogadro’s Hypothesis?
ⓐ. Oxygen and hydrogen combine to form water vapour in a 1:2:2 volume ratio
ⓑ. Carbon dioxide dissolves in water
ⓒ. Sodium reacts with chlorine to form NaCl
ⓓ. Calcium carbonate decomposes to CaO and CO₂
Correct Answer: Oxygen and hydrogen combine to form water vapour in a 1:2:2 volume ratio
Explanation: According to the balanced reaction, 1 volume O₂ + 2 volumes H₂ → 2 volumes H₂O. This is explained by Avogadro’s hypothesis, since equal volumes contain equal numbers of molecules.
106. The molar volume of a gas at STP is:
ⓐ. 11.2 L
ⓑ. 22.4 L
ⓒ. 44.8 L
ⓓ. 6.022 L
Correct Answer: 22.4 L
Explanation: One mole of any gas occupies 22.4 L at STP (0°C, 1 atm). This value is derived directly from Avogadro’s Hypothesis and the ideal gas equation.
107. Which pair of gases would contain the same number of molecules at STP if taken in equal volumes?
ⓐ. H₂ and O₂
ⓑ. H₂ and CO₂
ⓒ. H₂ and N₂
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Avogadro’s Hypothesis states equal volumes of gases under identical conditions contain equal numbers of molecules regardless of type. Thus, 1 L H₂, 1 L O₂, 1 L CO₂, and 1 L N₂ all contain the same number of molecules at STP.
108. Which concept directly arises from Avogadro’s Hypothesis?
ⓐ. Mole concept
ⓑ. Ionization energy
ⓒ. Law of definite proportions
ⓓ. Quantum mechanics
Correct Answer: Mole concept
Explanation: Avogadro’s Hypothesis led to the idea of the mole, defining one mole of any substance as containing $6.022 \times 10^{23}$ particles. This connects the microscopic world of atoms with measurable macroscopic quantities.
109. Which formula is derived from Avogadro’s Hypothesis?
ⓐ. $PV = nRT$
ⓑ. $E = mc^2$
ⓒ. $F = ma$
ⓓ. $Q = mc\Delta T$
Correct Answer: $PV = nRT$
Explanation: The ideal gas equation is built on Avogadro’s hypothesis, relating pressure, volume, temperature, and the number of moles. The other formulas belong to relativity, mechanics, and heat capacity.
110. Why was Avogadro’s Hypothesis initially rejected?
ⓐ. It contradicted Newton’s laws.
ⓑ. Dalton believed atoms of the same element could not combine with each other.
ⓒ. Lavoisier had already disproved it.
ⓓ. It did not explain conservation of mass.
Correct Answer: Dalton believed atoms of the same element could not combine with each other.
Explanation: Dalton’s Atomic Theory suggested atoms of the same element could not combine, conflicting with Avogadro’s idea of diatomic molecules (H₂, O₂, N₂). This led to its initial rejection, though it was later accepted with evidence.
111. Who is credited with proposing the first modern atomic theory?
ⓐ. Joseph Proust
ⓑ. John Dalton
ⓒ. Antoine Lavoisier
ⓓ. J.J. Thomson
Correct Answer: John Dalton
Explanation: John Dalton proposed the first modern atomic theory in 1803. His theory explained the laws of chemical combination using the concept of indivisible particles called atoms. This marked a turning point in chemistry.
112. According to Dalton’s Atomic Theory, matter is composed of:
ⓐ. Electrons and protons
ⓑ. Small, indivisible particles called atoms
ⓒ. Molecules only
ⓓ. Neutrons and nuclei
Correct Answer: Small, indivisible particles called atoms
Explanation: Dalton’s postulates stated that all matter consists of tiny, indivisible particles called atoms. Later discoveries (electron, proton, neutron) showed that atoms are divisible, but Dalton’s idea laid the foundation of atomic structure.
113. Which of the following is not a postulate of Dalton’s Atomic Theory?
ⓐ. Atoms of an element are identical in mass and properties.
ⓑ. Atoms cannot be created or destroyed in a chemical reaction.
ⓒ. Atoms of different elements combine in simple whole-number ratios.
ⓓ. Atoms contain protons, neutrons, and electrons.
Correct Answer: Atoms contain protons, neutrons, and electrons.
Explanation: Dalton did not know about subatomic particles; he believed atoms were indivisible. Protons, neutrons, and electrons were discovered later by Thomson, Rutherford, and Chadwick.
114. Which law of chemical combination is directly explained by Dalton’s Atomic Theory?
ⓐ. Law of definite proportions
ⓑ. Law of conservation of mass
ⓒ. Law of multiple proportions
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Dalton’s theory provided atomic-level explanations for all major chemical laws. Definite proportions arise from atoms combining in fixed ratios, multiple proportions from different ratios of atoms, and conservation of mass from atoms being neither created nor destroyed.
115. Which of the following statements from Dalton’s theory is still valid today?
ⓐ. Atoms are indivisible.
ⓑ. Atoms of the same element have identical properties.
ⓒ. Atoms combine in simple whole-number ratios.
ⓓ. Atoms cannot change their mass.
Correct Answer: Atoms combine in simple whole-number ratios.
Explanation: Modern atomic theory modified Dalton’s ideas. Atoms are divisible into subatomic particles, isotopes disprove identical properties, and mass can change in nuclear reactions. But atoms still combine in whole-number ratios in chemical reactions, which remains valid.
116. Which discovery challenged Dalton’s idea that atoms are indivisible?
ⓐ. Discovery of isotopes
ⓑ. Discovery of electrons
ⓒ. Discovery of Avogadro’s number
ⓓ. Discovery of the periodic table
Correct Answer: Discovery of electrons
Explanation: J.J. Thomson’s discovery of the electron in 1897 showed that atoms are divisible, contradicting Dalton’s postulate. Later, protons and neutrons further proved internal structure within atoms.
117. Which discovery proved Dalton wrong about atoms of an element being identical?
ⓐ. Isotopes
ⓑ. Neutrons
ⓒ. X-rays
ⓓ. Proton
Correct Answer: Isotopes
Explanation: Isotopes of the same element have the same atomic number but different mass numbers. For example, carbon-12 and carbon-14 differ in mass, proving Dalton wrong. This was discovered by F. Soddy in the early 20th century.
118. Which experiment supported Dalton’s idea that atoms combine in whole-number ratios?
ⓐ. Electrolysis of water
ⓑ. Rutherford’s gold foil experiment
ⓒ. Thomson’s cathode ray experiment
ⓓ. Photoelectric effect
Correct Answer: Electrolysis of water
Explanation: Electrolysis splits water into hydrogen and oxygen gases in the ratio 2:1 by volume, confirming that atoms combine in simple whole-number ratios (2 H atoms with 1 O atom).
119. Dalton’s Atomic Theory helped in the development of:
ⓐ. The periodic table
ⓑ. The mole concept
ⓒ. The law of reciprocal proportions
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Dalton’s theory influenced later developments like the periodic classification of elements, Avogadro’s hypothesis (mole concept), and understanding of chemical laws. It is one of the most influential theories in chemistry.
120. Why is Dalton’s Atomic Theory still important today despite its limitations?
ⓐ. It introduced the concept of subatomic particles.
ⓑ. It was the first theory to explain chemical laws using the concept of atoms.
ⓒ. It described quantum mechanics.
ⓓ. It explained radioactivity.
Correct Answer: It was the first theory to explain chemical laws using the concept of atoms.
Explanation: Even though some postulates are outdated, Dalton’s theory remains historically significant. It introduced the atomic model, linking chemical laws to atomic structure, and paved the way for modern atomic and molecular science.
121. Which of the following is the first postulate of Dalton’s Atomic Theory?
ⓐ. All matter is made up of indivisible particles called atoms.
ⓑ. Atoms of the same element have identical properties.
ⓒ. Atoms combine in whole-number ratios.
ⓓ. Atoms can be created or destroyed in chemical reactions.
Correct Answer: All matter is made up of indivisible particles called atoms.
Explanation: Dalton’s very first postulate stated that matter consists of extremely small, indivisible particles called atoms. Later discoveries of subatomic particles proved that atoms are divisible, but the idea of atoms as the basic building blocks of matter remains valid.
122. According to Dalton’s postulates, atoms of a given element are:
ⓐ. Different in mass and properties
ⓑ. Identical in mass and properties
ⓒ. Identical in mass but not in properties
ⓓ. Divisible into smaller parts
Correct Answer: Identical in mass and properties
Explanation: Dalton proposed that all atoms of a given element are identical in mass, size, and chemical properties. This postulate was later modified when isotopes (atoms of the same element with different masses) were discovered.
123. Which postulate explains the Law of Multiple Proportions?
ⓐ. Atoms cannot be destroyed or created.
ⓑ. Atoms of the same element are identical.
ⓒ. Atoms combine in simple whole-number ratios to form compounds.
ⓓ. Atoms are indivisible.
Correct Answer: Atoms combine in simple whole-number ratios to form compounds.
Explanation: Dalton stated that compounds are formed when atoms of different elements combine in fixed, simple, whole-number ratios. This explains why CO and CO₂ differ in oxygen content but still show a 1:2 ratio.
124. Which of the following best represents Dalton’s view of chemical reactions?
ⓐ. Reactions involve creation of new atoms.
ⓑ. Reactions involve rearrangement of atoms.
ⓒ. Reactions involve destruction of atoms.
ⓓ. Reactions involve conversion of mass into energy.
Correct Answer: Reactions involve rearrangement of atoms.
Explanation: Dalton’s postulate stated that chemical reactions involve the reorganization of atoms. The atoms themselves remain unchanged—they are simply rearranged to form new substances.
125. Which postulate explains the Law of Conservation of Mass?
ⓐ. Atoms of different elements combine in fixed ratios.
ⓑ. Atoms are indivisible.
ⓒ. Atoms of the same element are identical.
ⓓ. Atoms cannot be created or destroyed in chemical reactions.
Correct Answer: Atoms cannot be created or destroyed in chemical reactions.
Explanation: This postulate directly supports Lavoisier’s law, as it states that in chemical reactions, atoms are neither created nor destroyed, only rearranged, ensuring mass is conserved.
126. Dalton’s postulates emphasized that compounds are formed by:
ⓐ. Mixing atoms in any proportion
ⓑ. Combining atoms in simple whole-number ratios
ⓒ. Sharing electrons between atoms
ⓓ. Creation of new atoms
Correct Answer: Combining atoms in simple whole-number ratios
Explanation: Dalton explained that compounds always consist of atoms of two or more elements combined in fixed, simple ratios. This was an early explanation for the constant composition of compounds like H₂O and CO₂.
127. Which of the following statements is a limitation of Dalton’s postulates?
ⓐ. Atoms are indivisible.
ⓑ. Atoms of the same element are identical.
ⓒ. Atoms combine in whole-number ratios.
ⓓ. Both A and B
Correct Answer: Both A and B
Explanation: Dalton considered atoms indivisible and identical for each element. These were later disproved with the discovery of subatomic particles and isotopes. However, the whole-number ratio principle still holds true in chemical compounds.
128. Which postulate forms the basis of the Law of Definite Proportions?
ⓐ. Atoms of the same element are identical in mass and properties.
ⓑ. Atoms of different elements combine in fixed, simple ratios.
ⓒ. Atoms are indivisible particles.
ⓓ. Atoms are neither created nor destroyed.
Correct Answer: Atoms of different elements combine in fixed, simple ratios.
Explanation: Proust’s law of definite proportions is explained by Dalton’s postulate that atoms combine in fixed ratios, leading to compounds with constant composition (e.g., water is always H₂O).
129. Which postulate of Dalton’s Atomic Theory helped in introducing the concept of molecular masses?
ⓐ. Atoms combine in simple whole-number ratios to form compounds.
ⓑ. Atoms of the same element are identical.
ⓒ. Atoms cannot be created or destroyed.
ⓓ. Atoms are indivisible.
Correct Answer: Atoms combine in simple whole-number ratios to form compounds.
Explanation: This postulate allowed chemists to calculate relative atomic and molecular masses by analyzing the fixed ratios in which elements combine to form compounds.
130. Why were Dalton’s postulates revolutionary for his time?
ⓐ. They introduced isotopes.
ⓑ. They provided the first scientific explanation for laws of chemical combination.
ⓒ. They discovered the nucleus.
ⓓ. They explained nuclear energy.
Correct Answer: They provided the first scientific explanation for laws of chemical combination.
Explanation: Before Dalton, laws like conservation of mass and definite proportions were experimental observations. Dalton’s theory explained them using the atomic concept, marking the beginning of modern chemistry.
131. Which of the following was a major merit of Dalton’s Atomic Theory?
ⓐ. It explained the Law of Conservation of Mass.
ⓑ. It explained the concept of isotopes.
ⓒ. It explained nuclear reactions.
ⓓ. It explained the existence of protons and electrons.
Correct Answer: It explained the Law of Conservation of Mass.
Explanation: Dalton’s theory stated that atoms cannot be created or destroyed, which directly supported Lavoisier’s Law of Conservation of Mass. Isotopes, nuclear reactions, and subatomic particles were discovered much later.
132. Which merit of Dalton’s theory helped explain the Law of Definite Proportions?
ⓐ. Atoms are indivisible particles.
ⓑ. Atoms of different elements combine in fixed ratios.
ⓒ. Atoms can be subdivided into electrons and protons.
ⓓ. Atoms of the same element may have different masses.
Correct Answer: Atoms of different elements combine in fixed ratios.
Explanation: Dalton’s theory explained why compounds like water always have hydrogen and oxygen in a constant ratio (1:8 by mass). Options C and D were discovered after Dalton, and A alone cannot explain the law.
133. Which contribution of Dalton’s theory led to the calculation of relative atomic masses?
ⓐ. Postulate of indivisible atoms
ⓑ. Postulate of nuclear particles
ⓒ. Postulate of isotopes
ⓓ. Postulate of simple whole-number ratios
Correct Answer: Postulate of simple whole-number ratios
Explanation: By knowing that atoms combine in whole numbers, chemists could determine relative masses of atoms. This laid the foundation for molecular weight and stoichiometric calculations.
134. Which merit of Dalton’s theory laid the foundation for modern chemistry?
ⓐ. It introduced the idea that all matter is made of atoms.
ⓑ. It proved atoms are divisible.
ⓒ. It explained radioactivity.
ⓓ. It explained the periodic law.
Correct Answer: It introduced the idea that all matter is made of atoms.
Explanation: Dalton’s most significant merit was establishing atoms as the fundamental units of matter, which became the cornerstone of modern chemistry. Radioactivity, divisibility, and periodic law came later.
135. Which of the following best describes how Dalton’s theory supported the Law of Multiple Proportions?
ⓐ. Atoms are created in chemical reactions.
ⓑ. Atoms of the same element can combine in different simple ratios with another element.
ⓒ. Atoms of one element are identical.
ⓓ. Atoms have subatomic structure.
Correct Answer: Atoms of the same element can combine in different simple ratios with another element.
Explanation: For example, carbon and oxygen form CO and CO₂. Dalton’s theory explained this by stating atoms can combine in more than one simple whole-number ratio, which became the Law of Multiple Proportions.
136. One key merit of Dalton’s theory was that it provided:
ⓐ. Explanation for nuclear fission
ⓑ. Explanation for isotopes
ⓒ. Explanation for fractional atomic masses
ⓓ. Explanation for chemical reactions as rearrangements of atoms
Correct Answer: Explanation for chemical reactions as rearrangements of atoms
Explanation: Dalton explained that chemical reactions occur due to rearrangement of atoms, not their creation or destruction. This was a huge step forward in understanding reactions. Nuclear fission, isotopes, and fractional atomic masses were discovered later.
137. Dalton’s theory helped chemistry advance because it:
ⓐ. Rejected the atomic idea
ⓑ. Gave a logical basis for experimental chemical laws
ⓒ. Proved electrons existed
ⓓ. Described subatomic particles
Correct Answer: Gave a logical basis for experimental chemical laws
Explanation: Experimental laws like conservation of mass, definite proportions, and multiple proportions already existed. Dalton’s atomic theory tied them together logically, making chemistry more systematic.
138. Which merit of Dalton’s Atomic Theory connects directly with the development of the mole concept?
ⓐ. Atoms are indivisible.
ⓑ. Atoms contain neutrons.
ⓒ. Atoms combine in fixed whole-number ratios.
ⓓ. Atoms can emit radiation.
Correct Answer: Atoms combine in fixed whole-number ratios.
Explanation: Since atoms combine in definite ratios, scientists could later define the mole as a fixed number of atoms or molecules, connecting microscopic particles to measurable masses.
139. Which merit of Dalton’s theory helped establish chemical formulae?
ⓐ. Atoms of different elements combine in whole numbers to form compounds.
ⓑ. Atoms are divisible into protons and electrons.
ⓒ. Atoms of the same element may vary in properties.
ⓓ. Atoms can transmute in nuclear reactions.
Correct Answer: Atoms of different elements combine in whole numbers to form compounds.
Explanation: Dalton’s idea made it possible to represent compounds like H₂O, CO₂, and NH₃ with definite chemical formulae showing fixed atomic ratios.
140. Why was Dalton’s Atomic Theory considered revolutionary at the time?
ⓐ. It explained atomic structure using quantum mechanics.
ⓑ. It unified chemical laws under a single theoretical framework.
ⓒ. It discovered isotopes and subatomic particles.
ⓓ. It described nuclear reactions.
Correct Answer: It unified chemical laws under a single theoretical framework.
Explanation: Dalton’s biggest merit was unifying existing chemical laws under a single idea of atoms. This gave chemistry a solid scientific foundation and inspired later discoveries in atomic structure and molecular chemistry.
141. Which observation directly contradicts Dalton’s claim that “atoms of the same element are identical in mass and properties”?
ⓐ. Law of definite proportions
ⓑ. Gay-Lussac’s law of volumes
ⓒ. Existence of isotopes (e.g., $^{35}\mathrm{Cl}$ and $^{37}\mathrm{Cl}$)
ⓓ. Law of reciprocal proportions
Correct Answer: Existence of isotopes (e.g., $^{35}\mathrm{Cl}$ and $^{37}\mathrm{Cl}$)
Explanation: Isotopes are atoms of the same element with the same atomic number but different mass numbers. Chlorine exists mainly as $^{35}\mathrm{Cl}$ and $^{37}\mathrm{Cl}$, so atoms of chlorine are not identical in mass. This directly violates Dalton’s postulate of identical atoms for a given element.
142. Which discovery first showed that atoms are divisible, contradicting Dalton’s “indivisible atom” postulate?
ⓐ. Radioactivity by Becquerel
ⓑ. Proton by Rutherford
ⓒ. Neutron by Chadwick
ⓓ. Electron by J.J. Thomson
Correct Answer: Electron by J.J. Thomson
Explanation: Thomson’s cathode ray experiments (1897) established the electron as a universal subatomic particle, proving atoms contain internal structure. Hence, atoms are divisible—contrary to Dalton’s postulate. Protons and neutrons were discovered later.
143. Dalton assumed atoms of different elements have different masses. Which concept shows different elements can have the same mass number?
ⓐ. Isotopes
ⓑ. Isobars
ⓒ. Isotones
ⓓ. Allotropes
Correct Answer: Isobars
Explanation: Isobars (e.g., $^{40}\mathrm{Ar}$ and $^{40}\mathrm{Ca}$) are atoms of different elements with the same mass number. This weakens Dalton’s idea that atoms of different elements necessarily differ in mass.
144. Dalton’s fixed-composition view of compounds is limited because some solids are non-stoichiometric. Which is a classic example?
ⓐ. $\mathrm{NaCl}$
ⓑ. $\mathrm{H_2O}$
ⓒ. $\mathrm{CO_2}$
ⓓ. $\mathrm{FeO}$ (often $\mathrm{Fe}_{0.95}\mathrm{O}$)
Correct Answer: $\mathrm{FeO}$ (often $\mathrm{Fe}_{0.95}\mathrm{O}$)
Explanation: Many transition-metal oxides show variable composition due to lattice defects (metal/excess vacancies). $\mathrm{FeO}$ commonly exists near $\mathrm{Fe}_{0.95}\mathrm{O}$, contradicting Dalton’s strict fixed whole-number atomic ratios.
145. Dalton did not distinguish clearly between atoms and molecules (e.g., he treated elemental gases as monatomic). Which idea resolved this?
ⓐ. Avogadro’s hypothesis (equal volumes ⇒ equal molecules)
ⓑ. Law of multiple proportions
ⓒ. Law of conservation of mass
ⓓ. Law of reciprocal proportions
Correct Answer: Avogadro’s hypothesis (equal volumes ⇒ equal molecules)
Explanation: Avogadro proposed that equal volumes of gases at the same $T$ and $P$ contain equal numbers of molecules, allowing diatomic formulas for $\mathrm{H_2}, \mathrm{O_2}, \mathrm{N_2}$. This corrected Dalton’s atom–molecule confusion.
146. Which phenomenon (same molecular formula, different properties) Dalton’s theory could not explain?
ⓐ. Electronegativity
ⓑ. Polar covalency
ⓒ. Isomerism (e.g., ethanol vs dimethyl ether, both $\mathrm{C_2H_6O}$)
ⓓ. Hydrogen bonding
Correct Answer: Isomerism (e.g., ethanol vs dimethyl ether, both $\mathrm{C_2H_6O}$)
Explanation: Isomers share a molecular formula but differ in structure and properties. Dalton’s model lacked structural ideas and thus could not account for how identical atomic ratios yield distinct compounds.
147. Dalton’s postulate that atoms are indestructible fails in which processes?
ⓐ. Neutralization reactions
ⓑ. Nuclear reactions (fission/fusion)
ⓒ. Precipitation reactions
ⓓ. Combustion reactions
Correct Answer: Nuclear reactions (fission/fusion)
Explanation: In nuclear processes, atoms can transmute into different elements and a small mass converts to energy ($E = mc^2$). Dalton’s chemical-level indestructibility does not hold at the nuclear scale.
148. Which example shows a variable composition compound that challenges Dalton’s fixed whole-number ratios?
ⓐ. $\mathrm{CO_2}$
ⓑ. $\mathrm{NaHCO_3}$
ⓒ. $\mathrm{CaCO_3}$
ⓓ. $\mathrm{TiH}_{1.7}$ (interstitial hydride)
Correct Answer: $\mathrm{TiH}_{1.7}$ (interstitial hydride)
Explanation: Many metal hydrides accommodate hydrogen in interstitial sites, giving non-integer stoichiometries (e.g., $\mathrm{TiH}_x$ with variable $x$). This is beyond Dalton’s simple whole-number combination picture.
149. Which observation about isotopes exposes a limitation of Dalton’s “identical properties” postulate?
ⓐ. Isotopes have different atomic numbers.
ⓑ. Isotopes have identical physical properties.
ⓒ. Isotopes have nearly identical chemical but different physical properties (e.g., $\mathrm{D_2O}$ vs $\mathrm{H_2O}$)
ⓓ. Isotopes cannot form compounds
Correct Answer: Isotopes have nearly identical chemical but different physical properties (e.g., $\mathrm{D_2O}$ vs $\mathrm{H_2O}$)
Explanation: Heavy water has higher boiling point and density than ordinary water—clear physical differences due to mass. Dalton’s claim of identical properties fails once isotopes are recognized.
150. Which of the following is not a limitation of Dalton’s theory (i.e., it is actually a strength/merit)?
ⓐ. It explained laws of chemical combination using atoms.
ⓑ. It assumed atoms are indivisible.
ⓒ. It could not explain isomerism.
ⓓ. It failed to account for non-stoichiometric compounds.
Correct Answer: It explained laws of chemical combination using atoms.
Explanation: Dalton successfully unified conservation of mass, definite proportions, and multiple proportions via atoms. The other options are well-known shortcomings of his original framework.
151. Which of the following is the best definition of an atom?
ⓐ. The smallest particle of matter that can exist independently and take part in chemical reactions.
ⓑ. A particle that can be divided into electrons and protons.
ⓒ. The heaviest particle of an element.
ⓓ. A substance made by combining two or more elements.
Correct Answer: The smallest particle of matter that can exist independently and take part in chemical reactions.
Explanation: An atom is the smallest unit of an element that retains its chemical identity and can participate in reactions. Option B mentions subatomic particles but atoms themselves are the basic units of chemical processes, not the “heaviest particle.” Option D defines a compound.
152. Which scientist first introduced the modern concept of the atom?
ⓐ. J.J. Thomson
ⓑ. John Dalton
ⓒ. Ernest Rutherford
ⓓ. Niels Bohr
Correct Answer: John Dalton
Explanation: Dalton introduced the modern atomic theory in 1803, defining atoms as indivisible particles that combine in whole-number ratios. Later scientists refined the structure of the atom, but Dalton’s work laid the foundation.
153. Which of the following correctly lists the three fundamental subatomic particles in an atom?
ⓐ. Proton, neutron, electron
ⓑ. Proton, positron, neutrino
ⓒ. Proton, electron, photon
ⓓ. Electron, meson, neutron
Correct Answer: Proton, neutron, electron
Explanation: Atoms are composed of protons (positive), neutrons (neutral), and electrons (negative). Positrons and neutrinos are special particles in nuclear reactions, not part of ordinary atomic structure.
154. Where are protons and neutrons located in an atom?
ⓐ. In the nucleus at the center of the atom
ⓑ. In the electron cloud
ⓒ. Orbiting outside the atom
ⓓ. Randomly distributed in space
Correct Answer: In the nucleus at the center of the atom
Explanation: The nucleus contains protons and neutrons, while electrons move around it in regions of space called orbitals. This arrangement was demonstrated in Rutherford’s nuclear model.
155. Which particle is responsible for the chemical behavior of an atom?
ⓐ. Protons
ⓑ. Electrons
ⓒ. Neutrons
ⓓ. Nucleus
Correct Answer: Electrons
Explanation: The outermost (valence) electrons determine bonding and reactivity. Protons define the identity of the element, neutrons affect stability, but electrons control chemical reactions.
156. Which of the following correctly represents the atomic composition of oxygen-16?
ⓐ. 8 protons, 8 neutrons, 8 electrons
ⓑ. 16 protons, 8 neutrons, 8 electrons
ⓒ. 8 protons, 16 neutrons, 8 electrons
ⓓ. 16 protons, 16 neutrons, 8 electrons
Correct Answer: 8 protons, 8 neutrons, 8 electrons
Explanation: Atomic number of oxygen = 8 → protons = 8, electrons = 8. Mass number = 16 → neutrons = 16 − 8 = 8. Hence the composition is 8p, 8n, 8e.
157. Which statement about atoms in chemical reactions is correct?
ⓐ. Atoms are destroyed.
ⓑ. Atoms are created.
ⓒ. Atoms are rearranged to form new substances.
ⓓ. Atoms change their identity into new elements.
Correct Answer: Atoms are rearranged to form new substances.
Explanation: In chemical reactions, bonds break and new bonds form, rearranging atoms into new compounds. Atoms are not created or destroyed (except in nuclear reactions).
158. Which equation best illustrates a chemical reaction at the atomic level?
ⓐ. $2H_2 + O_2 \rightarrow 2H_2O$
ⓑ. $E = mc^2$
ⓒ. $F = ma$
ⓓ. $PV = nRT$
Correct Answer: $2H_2 + O_2 \rightarrow 2H_2O$
Explanation: This balanced chemical equation shows how atoms of hydrogen and oxygen rearrange to form water molecules. Other formulas represent physical laws, not chemical reactions.
159. Why are atoms considered neutral?
ⓐ. They contain only electrons.
ⓑ. The number of protons equals the number of electrons.
ⓒ. They contain equal numbers of neutrons and protons.
ⓓ. Their nucleus has no charge.
Correct Answer: The number of protons equals the number of electrons.
Explanation: Protons are positively charged and electrons are negatively charged. In a neutral atom, their numbers are equal, cancelling out charges. Neutrons are neutral and do not affect charge balance.
160. Which discovery disproved Dalton’s postulate of indivisible atoms?
ⓐ. Neutrons by Chadwick
ⓑ. Protons by Rutherford
ⓒ. Electrons by Thomson
ⓓ. Atomic nucleus by Rutherford
Correct Answer: Electrons by Thomson
Explanation: Thomson’s cathode ray experiments in 1897 proved that atoms contain smaller particles (electrons), showing they are divisible. Rutherford later discovered the nucleus, and Chadwick discovered neutrons, but the first contradiction came with electrons.
161. Which of the following best defines a molecule?
ⓐ. The smallest particle of an element or compound that can exist independently and retain chemical properties.
ⓑ. The smallest charged particle in an atom.
ⓒ. A particle found only in solids.
ⓓ. A cluster of nuclei without electrons.
Correct Answer: The smallest particle of an element or compound that can exist independently and retain chemical properties.
Explanation: A molecule is a group of two or more atoms chemically bonded together, representing the smallest unit of a substance that retains its chemical properties. Options B and D describe subatomic particles, not molecules.
162. Which of the following is a diatomic molecule?
ⓐ. CO₂
ⓑ. H₂
ⓒ. NH₃
ⓓ. CH₄
Correct Answer: H₂
Explanation: H₂ consists of two atoms of hydrogen bonded together, making it diatomic. CO₂ is triatomic, NH₃ is tetra-atomic, and CH₄ is penta-atomic.
163. Which of the following is a heteronuclear molecule?
ⓐ. O₂
ⓑ. H₂
ⓒ. N₂
ⓓ. HCl
Correct Answer: HCl
Explanation: HCl consists of two different atoms (H and Cl), hence heteronuclear. O₂, H₂, and N₂ are homonuclear molecules (same atoms).
164. Which of the following is a polyatomic molecule?
ⓐ. O₂
ⓑ. CO₂
ⓒ. N₂
ⓓ. H₂
Correct Answer: CO₂
Explanation: CO₂ has three atoms (one carbon and two oxygen) and is considered a polyatomic molecule. O₂, N₂, and H₂ are diatomic.
165. Which statement correctly describes molecular composition?
ⓐ. Molecules are made of protons and neutrons only.
ⓑ. Molecules are combinations of atoms held together by chemical bonds.
ⓒ. Molecules contain only electrons.
ⓓ. Molecules exist only in solid form.
Correct Answer: Molecules are combinations of atoms held together by chemical bonds.
Explanation: Atoms bond via covalent or ionic interactions to form molecules. These molecules can exist in solid, liquid, or gaseous states. Options A and C confuse molecules with subatomic particles.
166. Which equation illustrates a molecular chemical reaction?
ⓐ. $2H_2 + O_2 \rightarrow 2H_2O$
ⓑ. $PV = nRT$
ⓒ. $F = ma$
ⓓ. $E = mc^2$
Correct Answer: $2H_2 + O_2 \rightarrow 2H_2O$
Explanation: This reaction shows molecules of hydrogen and oxygen combining to form molecules of water. Other formulas are from physics and not chemical reactions.
167. Why do molecules of noble gases (He, Ne, Ar) exist as single atoms?
ⓐ. They cannot form bonds due to stable electronic configuration.
ⓑ. They lack electrons.
ⓒ. They contain only neutrons.
ⓓ. They are highly reactive.
Correct Answer: They cannot form bonds due to stable electronic configuration.
Explanation: Noble gases already have complete outer shells, making them chemically inert. Therefore, they exist as monoatomic molecules.
168. Which of the following is a molecule and not a compound?
ⓐ. H₂O
ⓑ. CO₂
ⓒ. O₂
ⓓ. NaCl
Correct Answer: O₂
Explanation: O₂ is a molecule but not a compound because it consists of only one element. Compounds like H₂O, CO₂, and NaCl have two or more different elements.
169. Which particle is directly rearranged during molecular chemical reactions?
ⓐ. Nuclei
ⓑ. Electrons
ⓒ. Neutrons
ⓓ. Protons
Correct Answer: Electrons
Explanation: Chemical reactions involve the breaking and forming of bonds through electron rearrangement in the outermost shells. Nuclei and protons remain unchanged in ordinary chemical reactions.
170. Which reaction shows molecular decomposition?
ⓐ. $2KClO_3 \rightarrow 2KCl + 3O_2$
ⓑ. $2H_2 + O_2 \rightarrow 2H_2O$
ⓒ. $NaCl \rightarrow Na^+ + Cl^-$
ⓓ. $CaCO_3 + 2HCl \rightarrow CaCl_2 + CO_2 + H_2O$
Correct Answer: $2KClO_3 \rightarrow 2KCl + 3O_2$
Explanation: This is a decomposition reaction where one molecular compound breaks down into simpler substances. The other equations represent combination, dissociation, or neutralization reactions.
171. What does the term atomicity refer to?
ⓐ. Number of protons in an atom
ⓑ. Number of atoms present in a molecule
ⓒ. Number of molecules in one mole
ⓓ. Number of neutrons in a nucleus
Correct Answer: Number of atoms present in a molecule
Explanation: Atomicity is defined as the total number of atoms constituting a molecule. For example, O₂ has atomicity 2, P₄ has atomicity 4, and S₈ has atomicity 8. It does not refer to protons, neutrons, or mole count.
172. Which of the following gases is monoatomic in nature?
ⓐ. Oxygen
ⓑ. Helium
ⓒ. Hydrogen
ⓓ. Nitrogen
Correct Answer: Helium
Explanation: Noble gases like He, Ne, Ar, Kr, and Xe exist as single atoms, hence monoatomic. O₂, H₂, and N₂ are diatomic gases.
173. Which of the following molecules is diatomic?
ⓐ. O₂
ⓑ. P₄
ⓒ. S₈
ⓓ. H₂SO₄
Correct Answer: O₂
Explanation: Oxygen exists naturally as a diatomic molecule (O₂). P₄ has atomicity 4, S₈ has atomicity 8, and H₂SO₄ has atomicity 7.
174. Which element exists as a polyatomic molecule under normal conditions?
ⓐ. Helium
ⓑ. Oxygen
ⓒ. Phosphorus (P₄)
ⓓ. Nitrogen
Correct Answer: Phosphorus (P₄)
Explanation: Phosphorus commonly exists as a tetra-atomic molecule (P₄). Oxygen (O₂) and nitrogen (N₂) are diatomic, and helium is monoatomic.
175. What is the atomicity of sulphur in its most stable molecular form?
ⓐ. 1
ⓑ. 2
ⓒ. 4
ⓓ. 8
Correct Answer: 8
Explanation: Sulphur exists as cyclic octa-atomic molecules (S₈) in its most stable form. Hence, its atomicity is 8.
176. Which of the following is a triatomic molecule?
ⓐ. O₃
ⓑ. H₂
ⓒ. Cl₂
ⓓ. Ne
Correct Answer: O₃
Explanation: Ozone (O₃) contains three oxygen atoms, making it a triatomic molecule. H₂ and Cl₂ are diatomic, and Ne is monoatomic.
177. Which statement is correct about monoatomic molecules?
ⓐ. They are made of one proton only.
ⓑ. They are single atoms that behave as molecules.
ⓒ. They are compounds made of one atom.
ⓓ. They are unstable in nature.
Correct Answer: They are single atoms that behave as molecules.
Explanation: Monoatomic molecules are individual atoms (like noble gases) that exist independently and retain all chemical properties. They are stable, not unstable.
178. Which of the following correctly represents the atomicity of ozone?
ⓐ. 1
ⓑ. 2
ⓒ. 3
ⓓ. 4
Correct Answer: 3
Explanation: Ozone consists of three oxygen atoms (O₃), making its atomicity 3.
179. Which of the following compounds has atomicity 7?
ⓐ. H₂O
ⓑ. HCl
ⓒ. H₂SO₄
ⓓ. NH₃
Correct Answer: H₂SO₄
Explanation: Sulphuric acid has 2 hydrogens, 1 sulfur, and 4 oxygens → total = 7 atoms in a molecule, hence atomicity 7.
180. Why is atomicity an important concept?
ⓐ. It helps calculate molar volume of gases.
ⓑ. It helps determine the number of atoms in a molecule for chemical reactions.
ⓒ. It helps identify isotopes.
ⓓ. It explains nuclear fission.
Correct Answer: It helps determine the number of atoms in a molecule for chemical reactions.
Explanation: Atomicity allows chemists to know how many atoms of each element are present in a molecule, which is essential for writing chemical equations and calculating molecular masses.
181. Which option correctly lists (monoatomic, diatomic, polyatomic) examples in order?
ⓐ. Ne, H₂O, O₂
ⓑ. Ar, O₃, N₂
ⓒ. He, Cl₂, CO
ⓓ. He, O₂, P₄
Correct Answer: He, O₂, P₄
Explanation: Monoatomic gases are noble gases like He; common diatomic molecules include O₂; a classic polyatomic elemental molecule is P₄. A and B mix up triatomic/diatomic; C ends with CO which is triatomic? No—CO has only two atoms (diatomic), not polyatomic.
182. What is the atomicity of glucose $\mathrm{C_6H_{12}O_6}$?
ⓐ. 24
ⓑ. 18
ⓒ. 20
ⓓ. 12
Correct Answer: 24
Explanation: Count total atoms: C = 6, H = 12, O = 6 → $6 + 12 + 6 = 24$. Options B, C, D underestimate by failing to add all atoms; atomicity is always the sum of all atoms in one molecule.
183. Which statement about halogens is correct regarding atomicity at standard conditions?
ⓐ. Only $\mathrm{F_2}$ and $\mathrm{Cl_2}$ are diatomic; $\mathrm{Br}$ and $\mathrm{I}$ are monoatomic.
ⓑ. None of the halogens are diatomic.
ⓒ. $\mathrm{F_2}, \mathrm{Cl_2}, \mathrm{Br_2}, \mathrm{I_2}$ all exist as diatomic molecules (physical state differs).
ⓓ. All halogens are polyatomic.
Correct Answer: $\mathrm{F_2}, \mathrm{Cl_2}, \mathrm{Br_2}, \mathrm{I_2}$ all exist as diatomic molecules (physical state differs).
Explanation: All elemental halogens are X₂: F₂, Cl₂ (gases), Br₂ (liquid), I₂ (solid). Their molecularity is 2 in each case. A and B are false; D is incorrect because halogens are not polyatomic in their standard elemental forms.
184. Which allotrope of oxygen has atomicity 3?
ⓐ. Dioxygen
ⓑ. Ozone
ⓒ. Superoxide
ⓓ. Peroxide
Correct Answer: Ozone
Explanation: Ozone is $\mathrm{O_3}$ (three O atoms) → triatomic. Dioxygen is $\mathrm{O_2}$ (diatomic). “Peroxide” and “superoxide” refer to ions in compounds (e.g., $\mathrm{O_2^{2-}}$, $\mathrm{O_2^-}$), not elemental oxygen molecules.
185. Determine the atomicity of $(\mathrm{NH_4})_2\mathrm{SO_4}$ (ammonium sulfate).
ⓐ. 14
ⓑ. 13
ⓒ. 12
ⓓ. 15
Correct Answer: 15
Explanation: Count atoms: N $= 2$, H $= 8$, S $= 1$, O $= 4$. Total $= 2 + 8 + 1 + 4 = 15$. Options A–C miscount one or more subgroups (commonly forgetting to double the $\mathrm{NH_4}$ group).
186. Which of the following is monoatomic at STP?
ⓐ. Argon
ⓑ. Hydrogen
ⓒ. Nitrogen
ⓓ. Oxygen
Correct Answer: Argon
Explanation: Noble gases (He, Ne, Ar, Kr, Xe) exist as single atoms → monoatomic. $\mathrm{H_2}, \mathrm{N_2}, \mathrm{O_2}$ are all diatomic molecules under standard conditions.
187. Which is a polyatomic elemental molecule?
ⓐ. $\mathrm{H_2}$
ⓑ. $\mathrm{N_2}$
ⓒ. $\mathrm{S_8}$
ⓓ. $\mathrm{F_2}$
Correct Answer: $\mathrm{S_8}$
Explanation: Elemental sulfur commonly exists as cyclic $\mathrm{S_8}$ (octa-atomic). $\mathrm{H_2}, \mathrm{N_2}, \mathrm{F_2}$ are all diatomic. Polyatomic means more than two atoms per molecule.
188. What is the atomicity of calcium hydroxide, $\mathrm{Ca(OH)_2}$?
ⓐ. 4
ⓑ. 5
ⓒ. 6
ⓓ. 7
Correct Answer: 5
Explanation: Atoms: Ca $= 1$, O $= 2$, H $= 2$ → total $1 + 2 + 2 = 5$. Though $\mathrm{Ca(OH)_2}$ is ionic in solids, counting atoms per formula unit gives the same tally for stoichiometric calculations.
189. Which set contains only triatomic molecules?
ⓐ. $\mathrm{CO_2}, \mathrm{H_2O}, \mathrm{O_3}$
ⓑ. $\mathrm{CO}, \mathrm{O_2}, \mathrm{H_2O}$
ⓒ. $\mathrm{CO_2}, \mathrm{N_2}, \mathrm{SO_2}$
ⓓ. $\mathrm{NO}, \mathrm{CO_2}, \mathrm{O_2}$
Correct Answer: $\mathrm{CO_2}, \mathrm{H_2O}, \mathrm{O_3}$
Explanation: Each listed molecule has three atoms: CO₂ (C + 2O), H₂O (2H + O), O₃ (3O). B, C, D each include at least one diatomic molecule (CO, O₂, or N₂), so they aren’t all triatomic.
190. Sulfur vapour at very high temperature contains $\mathrm{S_2}$. The atomicity of $\mathrm{S_2}$ is:
ⓐ. 8
ⓑ. 4
ⓒ. 3
ⓓ. 2
Correct Answer: 2
Explanation: While solid sulfur is $\mathrm{S_8}$ (polyatomic), at high $T$ the rings crack to smaller units like $\mathrm{S_2}$, which is diatomic. Options A–C confuse other allotropes or counts; atomicity equals the number of atoms per molecule.
191. Which statement about metals in the solid state and atomicity is most accurate?
ⓐ. Metallic sodium is diatomic.
ⓑ. Metallic sodium is a monoatomic molecule.
ⓒ. Metallic solids are extended lattices; “atomicity” (molecules) isn’t strictly applicable.
ⓓ. Metallic sodium is polyatomic with atomicity 8.
Correct Answer: Metallic solids are extended lattices; “atomicity” (molecules) isn’t strictly applicable.
Explanation: Atomicity refers to molecules. Metals form giant metallic lattices rather than discrete molecules, so describing them by molecular atomicity is not meaningful. A, B, D incorrectly force a molecular view on a non-molecular solid.
192. What is the atomicity of ammonium nitrate, $\mathrm{NH_4NO_3}$?
ⓐ. 8
ⓑ. 9
ⓒ. 10
ⓓ. 11
Correct Answer: 9
Explanation: Count atoms: N $= 2$, H $= 4$, O $= 3$. Total $= 2 + 4 + 3 = 9$. Options A, C, D miscount one or more atoms (commonly adding an extra oxygen or missing a hydrogen).
193. Which of the following best distinguishes an atom from a molecule?
ⓐ. Atoms can exist independently, molecules cannot.
ⓑ. Molecules always contain two or more atoms bonded together, while an atom is the smallest unit of an element.
ⓒ. Molecules are smaller than atoms.
ⓓ. Atoms always exist in bonded form.
Correct Answer: Molecules always contain two or more atoms bonded together, while an atom is the smallest unit of an element.
Explanation: An atom is the fundamental unit of matter, while a molecule is a combination of two or more atoms chemically bonded. Atoms can exist independently (e.g., noble gases), while molecules (e.g., H₂O, O₂) represent bonded states.
194. Which of the following is an example of an atom but not a molecule?
ⓐ. O₂
ⓑ. H₂O
ⓒ. He
ⓓ. CO₂
Correct Answer: He
Explanation: Helium is a noble gas that exists as a single atom, making it monoatomic. O₂, H₂O, and CO₂ are all molecules consisting of two or more atoms.
195. Which of the following is true about molecules but not about atoms?
ⓐ. They retain the chemical properties of a compound.
ⓑ. They contain neutrons and protons.
ⓒ. They define the atomic number of an element.
ⓓ. They are indivisible by chemical means.
Correct Answer: They retain the chemical properties of a compound.
Explanation: A molecule is the smallest particle of a compound that can exist independently and exhibit the compound’s chemical properties. Atoms define elements, not compounds. Options B and C refer to atoms, and D is incorrect because molecules can be split into atoms chemically.
196. Which of the following represents a molecule and not a single atom?
ⓐ. N
ⓑ. O
ⓒ. O₂
ⓓ. Ne
Correct Answer: O₂
Explanation: O₂ consists of two oxygen atoms bonded together, making it a molecule. N and O symbols refer to single atoms, while Ne is a noble gas atom.
197. Why are noble gases (e.g., Ar, Ne) classified as atoms rather than molecules?
ⓐ. They are unstable alone.
ⓑ. They exist as single independent atoms due to stable electron configurations.
ⓒ. They contain many protons.
ⓓ. They always bond to other elements.
Correct Answer: They exist as single independent atoms due to stable electron configurations.
Explanation: Noble gases have complete outer shells, so they don’t need to bond with other atoms. Hence, they exist as monoatomic gases, unlike O₂, N₂, or H₂.
198. Which of the following is the correct difference between atoms and molecules?
ⓐ. Atoms are always larger than molecules.
ⓑ. Atoms are charged, molecules are neutral.
ⓒ. Atoms are the building blocks of matter; molecules are groups of atoms chemically bonded.
ⓓ. Atoms cannot exist independently, but molecules can.
Correct Answer: Atoms are the building blocks of matter; molecules are groups of atoms chemically bonded.
Explanation: Atoms are fundamental particles, while molecules are made by joining atoms through covalent/ionic bonds. Atoms like He can exist independently, so D is incorrect. A and B are false generalizations.
199. Which of the following pairs correctly shows “atom vs molecule”?
ⓐ. H vs H₂
ⓑ. O₂ vs O
ⓒ. C vs CO₂
ⓓ. All of the above
Correct Answer: All of the above
Explanation: H is an atom, H₂ is a molecule; O is an atom, O₂ is a molecule; C is an atom, CO₂ is a molecule. Each example distinguishes atom from molecule correctly.
200. Which property belongs to molecules but not to individual atoms?
ⓐ. They can represent both elements and compounds.
ⓑ. They determine atomic number.
ⓒ. They are composed only of protons.
ⓓ. They cannot undergo bonding.
Correct Answer: They can represent both elements and compounds.
Explanation: Molecules may be elemental (O₂, N₂) or compound (H₂O, CO₂). Atoms alone cannot represent compounds, they only represent elements. Options B–D are incorrect descriptions of molecules.
The chapter Some Basic Concepts of Chemistry in Class 11 Chemistry (NCERT/CBSE syllabus) is the backbone for all higher-level concepts. It explains the laws of chemical combination, Dalton’s atomic theory, the concept of moles, Avogadro’s hypothesis, calculation of molar mass, empirical and molecular formulas, stoichiometric coefficients, and limiting reagents. These are not only vital for board exams but are also repeatedly asked in competitive exams such as JEE, NEET, AIIMS, and state-level entrance tests. This chapter consists of 394 MCQs with answers, split into 4 easy-to-use parts for systematic revision. In this section (Part 2), you will find the second set of 100 MCQs, focusing on numericals, mole concept applications, and formula-based problems that strengthen analytical and problem-solving skills.
- 👉 Total MCQs in this chapter: 394.
- 👉 This page contains: Second set of 100 solved MCQs with explanations.
- 👉 Useful for board exams, JEE, NEET, and other competitive tests.
- 👉 To see MCQs of other chapters, subjects, or classes, use the top navigation bar above.
- 👉 To continue practicing, click the Part 3 button above.