Chapter Exam

Chapter 1: Some Basic Concepts of Chemistry — Online MCQ Test

Q: Which of the following is considered a chemical combination of substances?

Answer: B. Water formed from hydrogen and oxygen — Water is a compound formed by chemical combination of hydrogen and oxygen in a fixed ratio. The other options are mixtures.

Q: The SI unit of amount of substance is:

Answer: C. mole — The mole is the SI unit used to express the amount of substance.

Q: How many moles are present in 18 g of water?

Answer: B. 1 mol — Molar mass of water is 18 g mol^-1, so 18 g corresponds to 1 mole.

Q: A sample contains 1.2044 × 10^24 molecules of NH3. The number of moles present is:

Answer: C. 2 mol — Dividing by Avogadro number gives 1.2044 × 10^24 / 6.022 × 10^23 = 2 mol.

CHEMISTRY · CLASS 11 FIRST PUC · Karnataka State Board

Practice Chapter 1: Some Basic Concepts of Chemistry with a free chapter-wise online MCQ test for Karnataka State Board CLASS 11 FIRST PUC CHEMISTRY. This chapter covers: Matter Chemical combination Mole concept Avogadro number Atomic mass Molecular mass Empirical formula Molecular formula Stoichiometry Limiting reagent. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 1: Some Basic Concepts of Chemistry — Important Questions & Answers (FAQ)

Frequently asked questions from Karnataka State Board CLASS 11 FIRST PUC CHEMISTRY — Chapter 1: Some Basic Concepts of Chemistry, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following is considered a chemical combination of substances?

A. A mixture of sand and iron filings
B. Water formed from hydrogen and oxygen ✓
C. Air in a cylinder
D. A solution of sugar in water

Answer: B. Water formed from hydrogen and oxygen
Water is a compound formed by chemical combination of hydrogen and oxygen in a fixed ratio. The other options are mixtures.

The SI unit of amount of substance is:

A. gram
B. litre
C. mole ✓
D. molecule

Answer: C. mole
The mole is the SI unit used to express the amount of substance.

How many moles are present in 18 g of water?

A. 0.5 mol
B. 1 mol ✓
C. 2 mol
D. 18 mol

Answer: B. 1 mol
Molar mass of water is 18 g mol^-1, so 18 g corresponds to 1 mole.

A sample contains 1.2044 × 10^24 molecules of NH3. The number of moles present is:

A. 0.5 mol
B. 1 mol
C. 2 mol ✓
D. 4 mol

Answer: C. 2 mol
Dividing by Avogadro number gives 1.2044 × 10^24 / 6.022 × 10^23 = 2 mol.

A student says that 1 mole of any substance contains 6.022 × 10^23 grams of that substance. Which is the best evaluation?

A. Correct for all substances
B. Correct only for gases
C. Incorrect; 1 mole contains 6.022 × 10^23 entities, not grams ✓
D. Correct only at STP

Answer: C. Incorrect; 1 mole contains 6.022 × 10^23 entities, not grams
One mole refers to the number of entities, while the mass in grams depends on the molar mass of the substance.