Q.1 Which of the following is not a chemical change?
Rusting of iron
Burning of wood
Melting of ice
Vinegar reacting with baking soda
Explanation - Melting of ice is a physical change as it involves a change in state without altering the chemical composition.
Correct answer is: Melting of ice
Q.2 What is the SI unit of amount of substance?
Mole
Gram
Liter
Newton
Explanation - The SI unit of the amount of substance is mole, which measures the number of elementary entities (atoms, molecules, etc.).
Correct answer is: Mole
Q.3 Who proposed the modern atomic theory?
John Dalton
J.J. Thomson
Ernest Rutherford
Niels Bohr
Explanation - John Dalton proposed the modern atomic theory in the early 19th century, stating that matter is made of indivisible atoms.
Correct answer is: John Dalton
Q.4 Which of the following represents a mixture?
Water
Salt
Air
Carbon dioxide
Explanation - Air is a homogeneous mixture of gases like nitrogen, oxygen, and trace gases.
Correct answer is: Air
Q.5 Which subatomic particle has a negative charge?
Proton
Neutron
Electron
Positron
Explanation - Electrons carry a negative charge, protons are positive, and neutrons are neutral.
Correct answer is: Electron
Q.6 Avogadro's number is approximately equal to:
6.022 × 10^23
3.14 × 10^23
9.81 × 10^23
1.602 × 10^-19
Explanation - Avogadro's number is 6.022 × 10^23, representing the number of particles in one mole of a substance.
Correct answer is: 6.022 × 10^23
Q.7 Which is a pure substance?
Air
Sugar solution
Salt
Milk
Explanation - Salt (sodium chloride) is a pure substance as it has a fixed chemical composition.
Correct answer is: Salt
Q.8 What is the charge of a neutron?
+1
0
-1
+2
Explanation - Neutrons are neutral particles and carry no charge.
Correct answer is: 0
Q.9 Which gas is used to fill balloons to make them float?
Hydrogen
Oxygen
Helium
Carbon dioxide
Explanation - Helium is lighter than air and non-reactive, making it safe for balloons.
Correct answer is: Helium
Q.10 Which element has atomic number 6?
Carbon
Oxygen
Nitrogen
Hydrogen
Explanation - Carbon has atomic number 6, which indicates it has 6 protons in its nucleus.
Correct answer is: Carbon
Q.11 Which of the following is an ionic compound?
NaCl
CO2
H2O
CH4
Explanation - NaCl is an ionic compound formed by the electrostatic attraction between Na+ and Cl- ions.
Correct answer is: NaCl
Q.12 Which law states that mass is neither created nor destroyed in a chemical reaction?
Boyle's Law
Law of Conservation of Mass
Dalton's Law
Avogadro's Law
Explanation - Lavoisier formulated the Law of Conservation of Mass, which is fundamental in chemistry.
Correct answer is: Law of Conservation of Mass
Q.13 Which of the following is a chemical property?
Melting point
Boiling point
Reactivity with acid
Density
Explanation - Chemical properties describe how a substance reacts chemically with other substances.
Correct answer is: Reactivity with acid
Q.14 Which of the following is the lightest atom?
Hydrogen
Helium
Lithium
Oxygen
Explanation - Hydrogen is the lightest atom with only one proton and one electron.
Correct answer is: Hydrogen
Q.15 Which of the following is an example of a homogeneous mixture?
Salt in water
Oil in water
Sand in water
Iron filings in sulfur
Explanation - A homogeneous mixture has uniform composition throughout; salt dissolves completely in water.
Correct answer is: Salt in water
Q.16 Which subatomic particle determines the chemical properties of an element?
Proton
Electron
Neutron
Positron
Explanation - Chemical behavior depends on the arrangement of electrons, especially valence electrons.
Correct answer is: Electron
Q.17 Which of the following is a noble gas?
Oxygen
Nitrogen
Neon
Hydrogen
Explanation - Neon is a noble gas, chemically inert and found in group 18 of the periodic table.
Correct answer is: Neon
Q.18 Which element is represented by the symbol 'K'?
Potassium
Krypton
Calcium
Sulfur
Explanation - The chemical symbol 'K' stands for Potassium, derived from its Latin name 'Kalium'.
Correct answer is: Potassium
Q.19 Which of the following is a diatomic molecule?
O2
CO2
H2O
CH4
Explanation - Diatomic molecules consist of two atoms; O2 is a diatomic molecule of oxygen.
Correct answer is: O2
Q.20 What is the mass of 1 mole of carbon-12?
12 g
6 g
1 g
24 g
Explanation - By definition, 1 mole of carbon-12 has a mass of exactly 12 grams.
Correct answer is: 12 g
Q.21 Which of the following statements is correct?
Atoms are indivisible
Electrons have positive charge
Protons have negative charge
Neutrons are neutral
Explanation - Neutrons have no charge, protons are positive, and electrons are negative. Atoms can be divided into subatomic particles.
Correct answer is: Neutrons are neutral
Q.22 Which of the following is used to represent chemical reactions?
Chemical equation
Physical formula
Atomic number
Valency
Explanation - Chemical equations use symbols and formulas to represent reactants and products of chemical reactions.
Correct answer is: Chemical equation
Q.23 Which scientist discovered the electron?
J.J. Thomson
Ernest Rutherford
John Dalton
Niels Bohr
Explanation - J.J. Thomson discovered the electron in 1897 using the cathode ray tube experiment.
Correct answer is: J.J. Thomson
Q.24 Which type of bond involves the sharing of electrons?
Ionic bond
Covalent bond
Metallic bond
Hydrogen bond
Explanation - Covalent bonds are formed when two atoms share electrons to achieve stability.
Correct answer is: Covalent bond