CN  ChemNexa

Some Basic Concepts of Chemistry — NEET Practice

Practice fundamental NEET chemistry topics — mole concept, atomic mass, stoichiometry — with MCQs, clear explanations, quick revision notes and mock tests.

Register Free for Full Chemistry Practice

Some Basic Concepts of Chemistry Revision Guide for NEET Chemistry

Some Basic Concepts of Chemistry is part of NEET Chemistry preparation. A strong revision plan should combine concept review with exam-style questions so that definitions, relationships, calculations and exceptions are recalled accurately.

Use the sample MCQs on this page to check understanding, then attempt the related ChemNexa tests for broader practice. When an answer is wrong, review the explanation and return to the underlying concept before attempting another set.

Important Topics

  • Core definitions and principles
  • Important equations or relationships
  • Common applications and examples
  • Frequently confused concepts
  • Exam-style multiple-choice questions
  • Error review and targeted revision

Revision Tip

Create a one-page summary of trends, structures, reactions, exceptions and key terminology for Some Basic Concepts of Chemistry, then test recall with mixed MCQs.

What to practise in Some Basic Concepts of Chemistry

Concept Revision

Revise definitions, principles, equations, trends and core ideas from Some Basic Concepts of Chemistry before attempting MCQs.

Exam-style MCQs

Use chapter-focused multiple-choice practice to improve accuracy, recall and application for NEET Chemistry.

Performance Practice

Attempt ChemNexa tests, review results and return to weak areas for another round of targeted revision.

Top 20 Some Basic Concepts of Chemistry MCQs with Answers

These public questions are selected from the exact Some Basic Concepts of Chemistry chapter, screened for topic relevance and deduplicated so repeated versions of the same MCQ are not shown publicly. Use them for quick revision, then sign in to attempt the complete test experience with more questions, results and performance review.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

1. A gaseous mixture contains 8 g of O2, 14 g of N2 and 22 g of CO2. What is the mole fraction of nitrogen?

  • A. 0.20
  • B. 0.40
  • C. 0.50
  • D. 0.60
Answer: B
Explanation: Moles: O2 = 8/32 = 0.25, N2 = 14/28 = 0.50, CO2 = 22/44 = 0.50. Total = 1.25 mol. Mole fraction of N2 = 0.50/1.25 = 0.40.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

2. A sample contains 3.011 × 10^23 atoms of an element and has a mass of 9 g. What is its atomic mass?

  • A. 9 u
  • B. 18 u
  • C. 27 u
  • D. 36 u
Answer: B
Explanation: 3.011 × 10^23 atoms represent 0.5 mol. Molar mass = 9/0.5 = 18 g mol−1, so atomic mass is 18 u.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

3. Which pair is isoelectronic?

  • A. Na+ and Ne
  • B. Mg2+ and Ar
  • C. F− and Na
  • D. Cl− and Ar+
Answer: A
Explanation: Na+ has 10 electrons and Ne also has 10 electrons.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

4. The percentage by mass of oxygen in Al2(SO4)3 is closest to:

  • A. 45.6%
  • B. 56.1%
  • C. 60.2%
  • D. 72.0%
Answer: B
Explanation: Molar mass = 342 g mol−1 and oxygen contributes 192 g. Percentage = 192/342 × 100 ≈ 56.1%.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

5. How many significant figures are present in 0.0045600 × 10^3?

  • A. 3
  • B. 4
  • C. 5
  • D. 6
Answer: C
Explanation: Leading zeros are not significant, but trailing zeros after a decimal are significant. Therefore there are 5 significant figures.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

6. A compound contains 40.0% carbon, 6.67% hydrogen and 53.33% oxygen by mass. Its empirical formula is:

  • A. CH2O
  • B. C2H4O2
  • C. CHO
  • D. CH3O
Answer: A
Explanation: For 100 g: C = 40/12 = 3.33 mol, H = 6.67 mol, O = 53.33/16 = 3.33 mol. Ratio = 1:2:1, so CH2O.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

7. The number of molecules present in 11.2 L of an ideal gas at STP is:

  • A. 6.022 × 10^23
  • B. 3.011 × 10^23
  • C. 1.505 × 10^23
  • D. 12.044 × 10^23
Answer: B
Explanation: At STP, 22.4 L is 1 mol. Therefore 11.2 L is 0.5 mol = 3.011 × 10^23 molecules.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

8. If 4 mol H2 react completely with 2 mol O2, the amount of water formed is:

  • A. 2 mol
  • B. 4 mol
  • C. 6 mol
  • D. 8 mol
Answer: B
Explanation: 2H2 + O2 → 2H2O. Thus 4 mol H2 with 2 mol O2 forms 4 mol H2O.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

9. What mass of CaCO3 is required to produce 11.2 L CO2 at STP on complete decomposition?

  • A. 25 g
  • B. 50 g
  • C. 75 g
  • D. 100 g
Answer: B
Explanation: 11.2 L CO2 = 0.5 mol, so 0.5 mol CaCO3 is needed. Mass = 0.5 × 100 = 50 g.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

10. Which statement is consistent with the law of multiple proportions?

  • A. Elements combine in continuously varying ratios
  • B. When two elements form more than one compound, masses of one combining with a fixed mass of the other are in small whole-number ratios
  • C. Mass is created during reaction
  • D. All compounds have identical composition
Answer: B
Explanation: This is the law of multiple proportions.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

11. A 10.0 g sample of impure CaCO3 gives 1.12 L CO2 at STP. The percentage purity is:

  • A. 25%
  • B. 50%
  • C. 75%
  • D. 100%
Answer: B
Explanation: 1.12 L CO2 = 0.05 mol, requiring 5.0 g CaCO3. Purity = 5/10 × 100 = 50%.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

12. Which quantity is dimensionless?

  • A. Molarity
  • B. Mole fraction
  • C. Molality
  • D. Density
Answer: B
Explanation: Mole fraction is a ratio of moles to total moles and has no unit.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

13. The molality of a solution containing 9.8 g H2SO4 in 100 g water is:

  • A. 0.5 m
  • B. 1.0 m
  • C. 2.0 m
  • D. 9.8 m
Answer: B
Explanation: Moles H2SO4 = 9.8/98 = 0.1 mol; solvent = 0.1 kg. Molality = 1.0 m.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

14. A solution has density 1.20 g mL−1 and is 20% HCl by mass. Its molarity is closest to:

  • A. 3.3 M
  • B. 6.6 M
  • C. 8.2 M
  • D. 12.0 M
Answer: B
Explanation: 1 L solution has mass 1200 g, containing 240 g HCl. Moles = 240/36.5 ≈ 6.58, so molarity ≈ 6.6 M.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

15. The number of oxygen atoms in 0.25 mol Al2(SO4)3 is:

  • A. 3.011 × 10^23
  • B. 9.033 × 10^23
  • C. 1.8066 × 10^24
  • D. 7.226 × 10^24
Answer: C
Explanation: Each formula unit has 12 O atoms. Number = 0.25 × 12 × 6.022 × 10^23 = 1.8066 × 10^24.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

16. For N2 + 3H2 → 2NH3, if 2 mol N2 and 3 mol H2 are mixed, the limiting reagent is:

  • A. N2
  • B. H2
  • C. NH3
  • D. Neither
Answer: B
Explanation: 2 mol N2 requires 6 mol H2, but only 3 mol H2 is available. Therefore H2 is limiting.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

17. The maximum amount of NH3 formed from 2 mol N2 and 3 mol H2 is:

  • A. 1 mol
  • B. 2 mol
  • C. 3 mol
  • D. 4 mol
Answer: B
Explanation: 3 mol H2 reacts with 1 mol N2 to form 2 mol NH3.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

18. Which sample contains the greatest number of atoms?

  • A. 4 g He
  • B. 16 g O2
  • C. 28 g N2
  • D. 44 g CO2
Answer: D
Explanation: 4 g He gives 1 mol atoms; 16 g O2 gives 1 mol atoms; 28 g N2 gives 2 mol atoms; 44 g CO2 gives 3 mol atoms.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

19. The ratio of number of molecules in 16 g O2 and 14 g N2 is:

  • A. 1:1
  • B. 1:2
  • C. 2:1
  • D. 2:3
Answer: A
Explanation: 16 g O2 and 14 g N2 are each 0.5 mol, so the molecule ratio is 1:1.

NEET Chemistry · Some Basic Concepts of Chemistry · Very Hard

20. A hydrocarbon contains 85.7% carbon and 14.3% hydrogen. Its empirical formula is:

  • A. CH
  • B. CH2
  • C. C2H3
  • D. C3H4
Answer: B
Explanation: For 100 g: C = 85.7/12 ≈ 7.14 and H = 14.3. Ratio ≈ 1:2, so CH2.

Login to Start Full Test

Some Basic Concepts of Chemistry Practice Tests

Some Basic Concepts of Chemistry Frequently Asked Questions

How should I prepare Some Basic Concepts of Chemistry for NEET Chemistry?

Revise the core concepts first, make a short list of important relationships or exceptions, and then solve chapter-focused MCQs while reviewing every error.

How can ChemNexa help with Some Basic Concepts of Chemistry practice?

This page provides public sample questions and links to published ChemNexa tests so you can combine quick revision with structured practice.

What should I do after getting an MCQ wrong?

Identify whether the mistake came from a concept gap, calculation, unit, sign, wording or memory error, review that point, and then attempt a similar question again.

Continue with another chapter to build connected concepts and strengthen your overall Chemistry preparation.

Continue NEET Chemistry

View all NEET chapters and testsBrowse all Chemistry PracticeCreate a free account