Chapter Exam

Chapter 7: Atoms and Molecules — Online MCQ Test

Q: What is the standard reference used to calculate the relative atomic mass of an element?

Answer: A. Carbon-12 isotope — The relative atomic mass is defined as the ratio of the average mass of one atom of an element to 1/12th of the mass of a carbon-12 atom.

Q: The number of atoms present in one molecule of an element is known as its ________.

Answer: B. Atomicity — Atomicity is the number of atoms present in one molecule of an element.

Q: Calculate the molecular mass of Water (H2O). (Given: Atomic mass of H=1, O=16)

Answer: B. 18 amu — Molecular mass = (2 * 1) + (1 * 16) = 18 amu.

Q: How many moles are there in 5.6 liters of Oxygen gas at STP?

Answer: A. 0.25 moles — Number of moles = Given volume / 22.4. So, 5.6 / 22.4 = 0.25 moles.

Q: An element X has a vapour density of 14. What is the atomicity of the element if its atomic mass is 7?

Answer: C. 4 — Molecular mass = 2 * Vapour density = 28. Atomicity = Molecular mass / Atomic mass = 28 / 7 = 4.

SCIENCE · CLASS 10th · Tamil Nadu State Board

Practice Chapter 7: Atoms and Molecules with a free chapter-wise online MCQ test for Tamil Nadu State Board CLASS 10th SCIENCE. This chapter covers: This chapter covers atomic mass molecular mass Avogadro hypothesis and mole concepts. Students learn relative atomic mass calculation atomicity and gas volume relationships.. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 7: Atoms and Molecules — Important Questions & Answers (FAQ)

Frequently asked questions from Tamil Nadu State Board CLASS 10th SCIENCE — Chapter 7: Atoms and Molecules, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the standard reference used to calculate the relative atomic mass of an element?

A. Carbon-12 isotope ✓
B. Hydrogen-1
C. Oxygen-16
D. Nitrogen-14

Answer: A. Carbon-12 isotope
The relative atomic mass is defined as the ratio of the average mass of one atom of an element to 1/12th of the mass of a carbon-12 atom.

The number of atoms present in one molecule of an element is known as its ________.

A. Valency
B. Atomicity ✓
C. Molarity
D. Molecular mass

Answer: B. Atomicity
Atomicity is the number of atoms present in one molecule of an element.

Calculate the molecular mass of Water (H2O). (Given: Atomic mass of H=1, O=16)

A. 17 amu
B. 18 amu ✓
C. 32 amu
D. 34 amu

Answer: B. 18 amu
Molecular mass = (2 * 1) + (1 * 16) = 18 amu.

How many moles are there in 5.6 liters of Oxygen gas at STP?

A. 0.25 moles ✓
B. 0.5 moles
C. 1 mole
D. 2 moles

Answer: A. 0.25 moles
Number of moles = Given volume / 22.4. So, 5.6 / 22.4 = 0.25 moles.

An element X has a vapour density of 14. What is the atomicity of the element if its atomic mass is 7?

A. 2
B. 3
C. 4 ✓
D. 1

Answer: C. 4
Molecular mass = 2 * Vapour density = 28. Atomicity = Molecular mass / Atomic mass = 28 / 7 = 4.

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