Q.1 Which of the following is NOT a fundamental concept of chemistry?
Atom
Molecule
Energy
Gravity
Explanation - Gravity is a physical force, not a chemical concept. Chemistry deals with atoms, molecules, reactions, and energy.
Correct answer is: Gravity
Q.2 Who is known as the father of modern chemistry?
Dmitri Mendeleev
Antoine Lavoisier
John Dalton
Robert Boyle
Explanation - Lavoisier is called the father of modern chemistry for establishing the law of conservation of mass and helping develop a systematic chemical nomenclature.
Correct answer is: Antoine Lavoisier
Q.3 Which of the following is a correct statement of Dalton's Atomic Theory?
Atoms can be created or destroyed in a chemical reaction
All atoms of a given element are identical in mass and properties
Atoms combine in variable proportions to form compounds
An atom is divisible into protons, neutrons, and electrons in chemical reactions
Explanation - Dalton's theory states that atoms of the same element are identical in mass and properties and combine in fixed ratios to form compounds.
Correct answer is: All atoms of a given element are identical in mass and properties
Q.4 Which of the following is NOT an example of a chemical change?
Rusting of iron
Burning of wood
Melting of ice
Combustion of petrol
Explanation - Melting of ice is a physical change as no new substance is formed, only a change in state occurs.
Correct answer is: Melting of ice
Q.5 The mass number of an atom is the sum of:
Protons only
Protons and neutrons
Neutrons and electrons
Protons and electrons
Explanation - Mass number (A) = number of protons + number of neutrons in the nucleus of an atom.
Correct answer is: Protons and neutrons
Q.6 Which of the following represents an element?
H2O
NaCl
O2
CO2
Explanation - O2 is a diatomic molecule consisting of only one type of element, oxygen. Others are compounds.
Correct answer is: O2
Q.7 Avogadro's number is the number of particles present in:
1 gram of substance
1 mole of substance
1 liter of gas
1 kilogram of substance
Explanation - Avogadro's number (6.022 × 10^23) represents the number of atoms, molecules, or particles in 1 mole of a substance.
Correct answer is: 1 mole of substance
Q.8 Which law states that mass is neither created nor destroyed in a chemical reaction?
Law of Constant Composition
Law of Multiple Proportions
Law of Conservation of Mass
Gay-Lussac's Law
Explanation - Lavoisier's Law of Conservation of Mass states that total mass of reactants equals total mass of products in a chemical reaction.
Correct answer is: Law of Conservation of Mass
Q.9 Which of the following represents a compound?
Na
O2
H2O
Cl2
Explanation - H2O consists of two different elements, hydrogen and oxygen, chemically combined in a fixed ratio, hence a compound.
Correct answer is: H2O
Q.10 Which particle in an atom has negligible mass?
Proton
Neutron
Electron
Alpha particle
Explanation - Electrons have very small mass (~1/1836 of a proton) and are considered negligible compared to protons and neutrons.
Correct answer is: Electron
Q.11 Which of the following represents an ionic bond?
H2
NaCl
O2
CH4
Explanation - NaCl is formed by transfer of electrons from sodium to chlorine, resulting in an ionic bond.
Correct answer is: NaCl
Q.12 Which concept is used to explain why gases expand to fill their container?
Kinetic theory of gases
Dalton's atomic theory
Law of definite proportions
Boyle's law
Explanation - The kinetic theory of gases explains gas behavior, including expansion, pressure, and temperature relationships.
Correct answer is: Kinetic theory of gases
Q.13 Which of the following is a mixture?
NaCl
Air
H2O
CO2
Explanation - Air is a physical combination of several gases (mainly N2 and O2), so it is a mixture.
Correct answer is: Air
Q.14 Which of the following is true about isotopes?
Same number of protons and electrons but different neutrons
Same number of neutrons but different protons
Different number of protons and neutrons
Same number of protons and neutrons
Explanation - Isotopes of an element have the same atomic number but different mass numbers due to differing neutron counts.
Correct answer is: Same number of protons and electrons but different neutrons
Q.15 Which law states that a chemical compound always contains its component elements in fixed ratio by mass?
Law of Multiple Proportions
Law of Definite Proportions
Law of Conservation of Mass
Avogadro's Law
Explanation - The Law of Definite Proportions, proposed by Proust, states that a chemical compound contains elements in fixed mass ratios.
Correct answer is: Law of Definite Proportions
Q.16 Which subatomic particle was discovered by J.J. Thomson?
Proton
Electron
Neutron
Photon
Explanation - J.J. Thomson discovered the electron in 1897 using the cathode ray tube experiment.
Correct answer is: Electron
Q.17 Which of the following represents a covalent bond?
NaCl
MgO
H2
KBr
Explanation - H2 consists of two hydrogen atoms sharing electrons, which is a covalent bond.
Correct answer is: H2
Q.18 What is the charge of a proton?
-1
0
+1
+2
Explanation - Protons are positively charged subatomic particles with a charge of +1e.
Correct answer is: +1
Q.19 Which of the following has the smallest mass?
Proton
Neutron
Electron
Alpha particle
Explanation - Electron has a negligible mass (~1/1836 of proton) compared to other particles.
Correct answer is: Electron
Q.20 Which scientist proposed the Nuclear Model of the atom?
Rutherford
Thomson
Dalton
Bohr
Explanation - Rutherford proposed the nuclear model after his gold foil experiment, showing a dense positively charged nucleus.
Correct answer is: Rutherford
Q.21 Which of the following represents a heterogeneous mixture?
Salt solution
Air
Oil and water
Sugar solution
Explanation - Oil and water do not mix uniformly, forming a heterogeneous mixture.
Correct answer is: Oil and water
Q.22 Which of the following is a pure substance?
Air
Salt
Milk
Soil
Explanation - Salt (NaCl) is chemically pure with fixed composition, unlike mixtures like air or milk.
Correct answer is: Salt
Q.23 Which gas law relates pressure and volume of a gas at constant temperature?
Charles's Law
Boyle's Law
Avogadro's Law
Gay-Lussac's Law
Explanation - Boyle's Law states that pressure is inversely proportional to volume at constant temperature (P ∝ 1/V).
Correct answer is: Boyle's Law
Q.24 Which of the following statements about electrons is correct?
Electrons are positively charged particles
Electrons are found in the nucleus
Electrons are negatively charged and move around the nucleus
Electrons have the same mass as neutrons
Explanation - Electrons are negatively charged subatomic particles that orbit the nucleus in various energy levels.
Correct answer is: Electrons are negatively charged and move around the nucleus