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Some Basic Concepts in Chemistry JEE Main MCQ & Practice Questions

Practice Some Basic Concepts in Chemistry MCQs for JEE Main Chemistry with answers, explanations, chapter revision and related ChemNexa mock tests.

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Some Basic Concepts in Chemistry Revision Guide for JEE Main Chemistry

Some Basic Concepts in Chemistry is part of JEE Main 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 in Chemistry, then test recall with mixed MCQs.

What to practise in Some Basic Concepts in Chemistry

Concept Revision

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

Exam-style MCQs

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Performance Practice

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Top 20 Some Basic Concepts in Chemistry MCQs with Answers

These public questions are selected from the exact Some Basic Concepts in 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.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

1. 18 g H2O contains how many moles?

  • A. 2
  • B. 18
  • C. 1
  • D. 0.5
Answer: C
Explanation: n=m/M=18/18=1 mol.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

2. 44 g CO2 contains how many moles?

  • A. 44
  • B. 1
  • C. 2
  • D. 0.5
Answer: B
Explanation: n=44/44=1 mol.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

3. 9 g H2O contains how many molecules?

  • A. 3.011×10^23
  • B. 6.022×10^23
  • C. 1.204×10^24
  • D. 1.505×10^23
Answer: A
Explanation: 9 g H2O=0.5 mol, so molecules=0.5NA.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

4. 1 mol O2 contains how many oxygen atoms?

  • A. NA
  • B. 0.5NA
  • C. 4NA
  • D. 2NA
Answer: D
Explanation: Each O2 molecule contains two atoms.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

5. At STP, 11.2 L ideal gas corresponds to:

  • A. 2 mol
  • B. 0.25 mol
  • C. 0.5 mol
  • D. 1 mol
Answer: C
Explanation: Using 22.4 L mol^-1, n=11.2/22.4=0.5 mol.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

6. For 2H2+O2→2H2O, 3 mol H2 requires:

  • A. 6 mol O2
  • B. 1.5 mol O2
  • C. 3 mol O2
  • D. 0.75 mol O2
Answer: B
Explanation: Stoichiometric H2:O2 ratio is 2:1.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

7. For N2+3H2→2NH3, 6 mol H2 can form:

  • A. 4 mol NH3
  • B. 2 mol NH3
  • C. 6 mol NH3
  • D. 3 mol NH3
Answer: A
Explanation: 3 mol H2 gives 2 mol NH3.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

8. For CH4+2O2→CO2+2H2O, 16 g CH4 forms theoretically:

  • A. 22 g CO2
  • B. 88 g CO2
  • C. 16 g CO2
  • D. 44 g CO2
Answer: D
Explanation: 16 g CH4=1 mol and gives 1 mol CO2=44 g.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

9. For 2H2+O2→2H2O, mixing 3 mol H2 and 2 mol O2 gives limiting reagent:

  • A. Neither
  • B. H2O
  • C. H2
  • D. O2
Answer: C
Explanation: 3 mol H2 needs only 1.5 mol O2, so H2 limits.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

10. For N2+3H2→2NH3, mixing 2 mol N2 and 3 mol H2 gives limiting reagent:

  • A. NH3
  • B. H2
  • C. N2
  • D. Neither
Answer: B
Explanation: 2 mol N2 needs 6 mol H2, but only 3 mol is present.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

11. If theoretical yield is 20 g and actual yield is 15 g, percentage yield is:

  • A. 75%
  • B. 25%
  • C. 133.3%
  • D. 80%
Answer: A
Explanation: %yield=15/20×100=75%.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

12. A 90% pure 20 g sample contains pure substance mass:

  • A. 20 g
  • B. 2 g
  • C. 9 g
  • D. 18 g
Answer: D
Explanation: Pure mass=0.90×20=18 g.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

13. Empirical formula represents:

  • A. Exact structure
  • B. Number of isotopes
  • C. Simplest whole-number atom ratio
  • D. Exact molecular mass
Answer: C
Explanation: It gives the simplest integer ratio of constituent atoms.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

14. If empirical formula is CH2O and molar mass is 180 g mol^-1, molecular formula is:

  • A. C3H6O3
  • B. C6H12O6
  • C. CH2O
  • D. C2H4O2
Answer: B
Explanation: Empirical mass=30; multiplier=180/30=6.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

15. A compound containing 40% C, 6.67% H and 53.33% O has empirical formula:

  • A. CH2O
  • B. CHO
  • C. CH4O
  • D. C2H4O
Answer: A
Explanation: Mole ratio is approximately C:H:O=1:2:1.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

16. Mass percent of oxygen in H2O is approximately:

  • A. 11.1%
  • B. 50%
  • C. 16%
  • D. 88.9%
Answer: D
Explanation: 16/18×100≈88.9%.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

17. 0.5 mol solute in 250 mL solution has molarity:

  • A. 1.0 M
  • B. 4.0 M
  • C. 2.0 M
  • D. 0.5 M
Answer: C
Explanation: M=0.5/0.250=2.0 M.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

18. 0.5 mol solute dissolved in 1 kg solvent has molality:

  • A. 0.25 m
  • B. 0.5 m
  • C. 1.0 m
  • D. 2.0 m
Answer: B
Explanation: m=0.5/1=0.5 mol kg^-1.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

19. Which concentration term is essentially temperature independent?

  • A. Molality
  • B. Molarity
  • C. Volume percent
  • D. Normality
Answer: A
Explanation: Molality depends on mass rather than volume.

JEE Main Chemistry · Some Basic Concepts in Chemistry · Very Very Hard

20. For a binary mixture with xA=0.30, xB equals:

  • A. 0.30
  • B. 1.30
  • C. 0
  • D. 0.70
Answer: D
Explanation: xA+xB=1.

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Some Basic Concepts in Chemistry Practice Tests

Some Basic Concepts in Chemistry Frequently Asked Questions

How should I prepare Some Basic Concepts in Chemistry for JEE Main Chemistry?

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