Chapter 3 PHYSICAL SCIENCE : Atoms and Molecules — Online MCQ Test
SCIENCE · CLASS 9th · Andhra State Board
Practice Chapter 3 PHYSICAL SCIENCE : Atoms and Molecules with a free chapter-wise online MCQ test.
This chapter covers: This chapter covers laws of chemical combination Dalton atomic theory atoms molecules atomic mass molecular mass chemical formulas and mole concept..
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Chapter 3 PHYSICAL SCIENCE : Atoms and Molecules — Important Questions & Answers
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.
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.
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.
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.
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):
- A. 7g
- B. 14g
- C. 28g
- D. 56g
Answer: B. 14g
Molar mass of N2 is 28g/mol. Mass = 0.5 mol * 28g/mol = 14g.
Molar mass of N2 is 28g/mol. Mass = 0.5 mol * 28g/mol = 14g.