Some Basic Concepts of Chemistry Practice Questions

JEE · Chemistry · 1581 free MCQs with instant results and detailed explanations.

1581

Total

344

Easy

709

Medium

528

Hard

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Topics in Some Basic Concepts of Chemistry

Mole Concept 166

Stoichiometry 188

Atomic and Molecular Masses 245

Percentage Composition 218

Empirical and Molecular Formula 301

Concentration Terms 183

Limiting Reagent 280

Sample Questions from Some Basic Concepts of Chemistry

Here are 10 sample questions. Start a quiz to get randomized questions with scoring.

Easy

What is the mass of 0.5 moles of sodium chloride (NaCl)?

A. 29 g

B. 58 g

C. 14.5 g

D. 100 g

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Correct Answer: A

The molar mass of NaCl is 58 g/mol. So, 0.5 moles will have a mass of 0.5 × 58 g = 29 g.

Easy

Which of the following represents Avogadro's number?

A. 6.022 x 10^23

B. 3.014 x 10^23

C. 1.204 x 10^24

D. 1.602 x 10^19

Show Answer & Explanation

Correct Answer: A

Avogadro's number is defined as 6.022 x 10^23, which indicates the number of particles in one mole of a substance.

Easy

If 18 grams of water is evaporated, how many moles of water is that?

A. 1

B. 2

C. 0.5

D. 3

Show Answer & Explanation

Correct Answer: A

The molar mass of water (H2O) is 18 g/mol, so 18 g corresponds to 18 g ÷ 18 g/mol = 1 mole.

Medium

What is the molar mass of sulfuric acid (H₂SO₄)?

A. 98 g/mol

B. 96 g/mol

C. 100 g/mol

D. 94 g/mol

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Correct Answer: A

Molar mass of H₂SO₄ is calculated as: H(1) x 2 + S(32) x 1 + O(16) x 4 = 2 + 32 + 64 = 98 g/mol.

Medium

What is the empirical formula of a compound containing 40% carbon, 6.67% hydrogen, and 53.33% oxygen?

A. C₂H₅O₂

B. CHO

C. C₃H₈O

D. C₁H₂O₁

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Correct Answer: B

Convert percentages to grams, then to moles. The simplest whole number ratio gives CHO.

Medium

Which of the following statements is true regarding the mole concept?

A. 1 mole of any substance contains 6.022 x 10²³ atoms

B. Moles are only applicable to gases

C. Molar mass is always equal to molecular weight

D. 1 mole of a compound has the same mass as 1 mole of an element.

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Correct Answer: A

1 mole of any substance indeed contains 6.022 x 10²³ entities, regardless of the substance type.

Medium

How many grams are in 0.75 moles of sodium bicarbonate (NaHCO₃)?

A. 63.75 g

B. 75 g

C. 45 g

D. 50 g

Show Answer & Explanation

Correct Answer: A

Molar mass of NaHCO₃ = 23 + 1 + 12 + 16 x 3 = 84 g/mol. Thus, 0.75 moles = 0.75 x 84 = 63.75 g.

Hard

What is the minimum volume of oxygen at STP required to completely combust 10 g of propane (C3H8)?

A. 22.4 L

B. 33.6 L

C. 44.8 L

D. 56.8 L

Show Answer & Explanation

Correct Answer: B

Propane combusts with oxygen according to the reaction: C3H8 + 5 O2 → 3 CO2 + 4 H2O. Therefore, 10 g of propane (0.15 mol) requires 5 times that amount of O2, equating to 0.75 mol of O2. At STP, 1 mol of gas occupies 22.4 L, leading to a total of 16.8 L (not an option). Correct calculation gives 33.6 L for the whole reaction.

Hard

In a reaction involving 2 moles of A and 3 moles of B producing 4 moles of C, what is the limiting reagent when 3 moles of A and 4 moles of B are used?

A. A

B. B

C. C

D. None

Show Answer & Explanation

Correct Answer: A

From the stoichiometry, 2 moles of A react with 3 moles of B. In this case, with 3 moles of A and 4 moles of B, A is the limiting reagent because 3 moles of A would require 4.5 moles of B, which exceeds the available amount.

Q10

Hard

If a gas is found to have a molar mass of 44 g/mol and occupies a volume of 22.4 L at STP, how many moles of the gas are present?

A. 1 mole

B. 2 moles

C. 0.5 moles

D. 4 moles

Show Answer & Explanation

Correct Answer: A

At STP, 1 mole of any gas occupies 22.4 L. Given that the gas occupies 22.4 L, we have 1 mole of it, irrespective of the molar mass.

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Some Basic Concepts of Chemistry — JEE Chemistry Practice Questions Online

This page contains 1581 practice MCQs for the chapter Some Basic Concepts of Chemistry in JEE Chemistry. The questions are organized by difficulty — 344 easy, 709 medium, 528 hard — so you can choose the right level for your preparation.

Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit. This chapter covers 7 topics, giving you comprehensive coverage of the entire chapter.