Chapter Exam

Chapter 3 PHYSICAL SCIENCE : Atoms and Molecules — Online MCQ Test

Q: Which law states that matter can neither be created nor destroyed in a chemical reaction?

Answer: A. Law of Conservation of Mass — The Law of Conservation of Mass states that mass is neither created nor destroyed during a chemical change.

Q: What is the standard unit used to express the atomic mass of an element?

Answer: B. Atomic mass unit (u) — The atomic mass unit (amu or u) is defined as 1/12th the mass of one carbon-12 atom.

Q: What is the molecular mass of O2 if the atomic mass of oxygen is 16u?

Answer: B. 32u — Molecular mass is calculated by multiplying the atomic mass by the number of atoms: 16 x 2 = 32u.

Q: In a reaction, 10g of reactant A reacts with 5g of reactant B to produce 15g of product C. Which law does this demonstrate?

Answer: B. Law of Conservation of Mass — Total mass of reactants (10+5=15g) equals the total mass of products (15g), satisfying the Law of Conservation of Mass.

Q: The mass of 0.5 moles of N2 gas is (Atomic mass of N=14u):

Answer: B. 14g — Molar mass of N2 is 28g/mol. Mass = 0.5 mol * 28g/mol = 14g.

SCIENCE · CLASS 9th · Andhra State Board

Practice Chapter 3 PHYSICAL SCIENCE : Atoms and Molecules with a free chapter-wise online MCQ test for Andhra State Board CLASS 9th SCIENCE. This chapter covers: This chapter covers laws of chemical combination Dalton atomic theory atoms molecules atomic mass molecular mass chemical formulas and mole concept.. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 3 PHYSICAL SCIENCE : Atoms and Molecules — Important Questions & Answers (FAQ)

Frequently asked questions from Andhra State Board CLASS 9th SCIENCE — Chapter 3 PHYSICAL SCIENCE : Atoms and Molecules, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which law states that matter can neither be created nor destroyed in a chemical reaction?

A. Law of Conservation of Mass ✓
B. Law of Constant Proportions
C. Law of Multiple Proportions
D. Avogadro's Law

Answer: A. Law of Conservation of Mass
The Law of Conservation of Mass states that mass is neither created nor destroyed during a chemical change.

What is the standard unit used to express the atomic mass of an element?

A. Gram
B. Atomic mass unit (u) ✓
C. Kilogram
D. Mole

Answer: B. Atomic mass unit (u)
The atomic mass unit (amu or u) is defined as 1/12th the mass of one carbon-12 atom.

What is the molecular mass of O2 if the atomic mass of oxygen is 16u?

A. 16u
B. 32u ✓
C. 8u
D. 48u

Answer: B. 32u
Molecular mass is calculated by multiplying the atomic mass by the number of atoms: 16 x 2 = 32u.

In a reaction, 10g of reactant A reacts with 5g of reactant B to produce 15g of product C. Which law does this demonstrate?

A. Law of Definite Proportions
B. Law of Conservation of Mass ✓
C. Law of Multiple Proportions
D. Dalton's Atomic Theory

Answer: B. Law of Conservation of Mass
Total mass of reactants (10+5=15g) equals the total mass of products (15g), satisfying the Law of Conservation of Mass.

The mass of 0.5 moles of N2 gas is (Atomic mass of N=14u):