Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry MCQs

Here are some multiple-choice questions (MCQs) with answers for Class 11 Chemistry Chapter 1, “Some Basic Concepts of Chemistry.” These questions are aligned with the CBSE board curriculum and cover topics from the latest Class 11 chemistry syllabus. By going through these MCQs, you can easily brush up on the concepts discussed in the chapter and get ready for your Class 11 Annual exams, along with other entrance exams like NEET and JEE.

MCQs Class 11 Some Basic Concepts of Chemistry

Section A: Laws of Chemical Combination
Q1. Law of conservation of mass was given by:
a) Dalton
b) Lavoisier
c) Proust
d) Gay Lussac
Answer: b) Lavoisier

Q2. Law of definite proportion was proposed by:
a) Proust
b) Dalton
c) Gay Lussac
d) Avogadro
Answer: a) Proust

Q3. Law of multiple proportion is illustrated by:
a) CO and CO₂
b) H₂ and O₂
c) H₂O and NaOH
d) NH₃ and HCl
Answer: a) CO and CO₂

Q4. Which law is the basis of Dalton’s Atomic Theory?
a) Law of reciprocal proportion
b) Law of conservation of mass
c) Law of definite proportion
d) Law of multiple proportion
Answer: d) Law of multiple proportion

Q5. Equal volumes of gases under similar conditions contain equal number of molecules. This is:
a) Boyle’s Law
b) Dalton’s Law
c) Avogadro’s Law
d) Gay Lussac’s Law
Answer: c) Avogadro’s Law

Section B: Atomic & Molecular Mass
Q6. Relative atomic mass is defined as the ratio of average mass of atom to:
a) One atom of H
b) 1/16th of O atom
c) 1/12th of C-12 atom
d) One atom of He
Answer: c) 1/12th of C-12 atom

Q7. Molecular mass of H₂SO₄ is:
a) 49
b) 98
c) 196
d) 32
Answer: b) 98

Q8. Equivalent mass = (Molar mass) ÷ (n-factor). The n-factor for H₂SO₄ in neutralisation is:
a) 1
b) 2
c) 3
d) 4
Answer: b) 2

Q9. Which has highest equivalent mass?
a) HCl
b) H₂SO₄
c) NaOH
d) HNO₃
Answer: b) H₂SO₄

Q10. The molecular mass of CH₃OH is:
a) 30
b) 32
c) 34
d) 36
Answer: b) 32

Section C: Mole Concept
Q11. 1 mole of any substance contains:
a) 6.022 × 10²² atoms
b) 6.022 × 10²³ particles
c) 22.4 particles
d) 1 g of atoms
Answer: b) 6.022 × 10²³ particles

Q12. 1 mole of CO₂ weighs:
a) 22.4 g
b) 32 g
c) 44 g
d) 28 g
Answer: c) 44 g

Q13. 22.4 L of any gas at STP contains:
a) 1 molecule
b) 1 mole
c) 44 g
d) None
Answer: b) 1 mole

Q14. Number of atoms in 16 g of O₂ is:
a) 6.022 × 10²³
b) 12.044 × 10²³
c) 3.011 × 10²³
d) 9.033 × 10²³
Answer: b) 12.044 × 10²³

Q15. Molar mass of Na₂CO₃ is:
a) 106 g
b) 44 g
c) 62 g
d) 142 g
Answer: a) 106 g

Section D: Percentage Composition & Empirical Formula
Q16. % of nitrogen in NH₃ is:
a) 82.35%
b) 17.65%
c) 50%
d) 70%
Answer: a) 82.35%

Q17. % of carbon in CO₂ is:
a) 12%
b) 27.3%
c) 44%
d) 33%
Answer: b) 27.3%

Q18. Empirical formula of C₆H₆ is:
a) CH
b) CH₂
c) C₂H₄
d) CH₃
Answer: a) CH

Q19. If empirical formula mass = molecular mass, then molecular formula is:
a) Half of empirical formula
b) Double of empirical formula
c) Same as empirical formula
d) Cannot be predicted
Answer: c) Same as empirical formula

Q20. A compound contains 40% C, 6.7% H, 53.3% O. Its empirical formula is:
a) CH₂O
b) C₂H₄O₂
c) C₆H₁₂O₆
d) CHO
Answer: a) CH₂O

Section E: Stoichiometry
Q21. Which is a balanced equation?
a) H₂ + O₂ → H₂O
b) 2H₂ + O₂ → 2H₂O
c) H₂ + O₂ → 2H₂O
d) 2H₂ + 2O₂ → 2H₂O
Answer: b) 2H₂ + O₂ → 2H₂O

Q22. 2 moles of H₂ react with O₂ to give:
a) 1 mole H₂O
b) 2 moles H₂O
c) 3 moles H₂O
d) 4 moles H₂O
Answer: b) 2 moles H₂O

Q23. Volume of CO₂ produced from complete combustion of 44 g of CO₂ at STP:
a) 11.2 L
b) 22.4 L
c) 44.8 L
d) 33.6 L
Answer: b) 22.4 L

Q24. 1 mole CaCO₃ decomposes to produce:
a) 1 mole CO₂
b) 2 mole CO₂
c) 0.5 mole CO₂
d) None
Answer: a) 1 mole CO₂

Q25. Mass of NaOH required to neutralise 49 g H₂SO₄ (M=98):
a) 40 g
b) 80 g
c) 120 g
d) 160 g
Answer: b) 80 g

Section F: Limiting Reagent
Q26. Limiting reagent is:
a) Always present in excess
b) Present in minimum number of moles
c) Completely consumed in reaction
d) Does not react
Answer: c) Completely consumed in reaction

Q27. In 2H₂ + O₂ → 2H₂O, if 3 moles H₂ and 2 moles O₂ are taken, limiting reagent is:
a) H₂
b) O₂
c) Both
d) None
Answer: a) H₂

Q28. 2 moles H₂ react with 1 mole O₂. If 5 moles H₂ and 2 moles O₂ are present, moles of H₂O formed =
a) 2
b) 3
c) 4
d) 5
Answer: c) 4

Q29. In C + O₂ → CO₂, 12 g C and 32 g O₂ are taken. Limiting reagent is:
a) C
b) O₂
c) Both
d) None
Answer: d) None (both completely react)

Q30. In Ca + 2H₂O → Ca(OH)₂ + H₂, if 40 g Ca reacts with 36 g H₂O, limiting reagent is:
a) Ca
b) H₂O
c) Both
d) None
Answer: b) H₂O

Section G: Concentration Terms
Q31. Molarity is defined as:
a) Moles of solute / kg solvent
b) Moles of solute / L solution
c) Mass of solute / mass of solvent
d) Moles of solvent / L solution
Answer: b) Moles of solute / L solution

Q32. Molality is defined as:
a) Moles of solute / kg solvent
b) Moles of solute / L solution
c) Mass of solute / mass of solvent
d) Mass of solute / volume solution
Answer: a) Moles of solute / kg solvent

Q33. Normality = Molarity × ____
a) Atomic number
b) Avogadro number
c) n-factor
d) Volume
Answer: c) n-factor

Q34. Mole fraction =
a) Moles of solute / total moles
b) Mass of solute / mass of solvent
c) Moles of solvent / moles of solute
d) None
Answer: a) Moles of solute / total moles

Q35. Mass % =
a) (Mass of solute / Mass of solution) × 100
b) (Moles of solute / Moles of solvent) × 100
c) (Mass of solvent / Mass of solute) × 100
d) None
Answer: a) (Mass of solute / Mass of solution) × 100

Section H: Numerical-based MCQs (Conceptual)
Q36. Number of molecules in 18 g of H₂O is:
a) 6.022 × 10²³
b) 3.011 × 10²³
c) 12.044 × 10²³
d) 9.033 × 10²³
Answer: a) 6.022 × 10²³

Q37. Volume of 0.5 mol of O₂ gas at STP is:
a) 22.4 L
b) 11.2 L
c) 5.6 L
d) 44.8 L
Answer: b) 11.2 L

Q38. Number of moles in 4.4 g CO₂:
a) 0.1 mol
b) 0.2 mol
c) 0.5 mol
d) 1 mol
Answer: b) 0.1 mol

Q39. 1 mole of NaCl contains:
a) 6.022 × 10²³ atoms
b) 1.204 × 10²⁴ atoms
c) 3.011 × 10²³ atoms
d) 6.022 × 10²³ ions
Answer: b) 1.204 × 10²⁴ atoms

Q40. Number of moles of electrons in 1 Coulomb charge is:
a) 6.022 × 10²³
b) 1/96485
c) 96485
d) None
Answer: b) 1/96485

Section I: Conceptual Miscellaneous
Q41. Atomicity of phosphorus (P₄) is:
a) 1
b) 2
c) 3
d) 4
Answer: d) 4

Q42. Avogadro number is a:
a) Dimensionless constant
b) Fundamental constant with unit
c) Experimental constant with unit
d) None
Answer: a) Dimensionless constant

Q43. 1 u =
a) 1.66 × 10⁻²⁷ g
b) 1.66 × 10⁻²⁴ g
c) 1.66 × 10⁻²⁴ kg
d) 1.66 × 10⁻²⁷ kg
Answer: d) 1.66 × 10⁻²⁷ kg

Q44. STP means:
a) 0°C, 1 atm
b) 25°C, 1 atm
c) 0 K, 1 atm
d) 273°C, 1 atm
Answer: a) 0°C, 1 atm

Q45. Avogadro’s hypothesis was verified by:
a) Gay Lussac
b) Cannizzaro
c) Dalton
d) Lavoisier
Answer: b) Cannizzaro

Section J: Higher-order MCQs
Q46. 5.6 L of O₂ at STP contains:
a) 0.1 mol
b) 0.25 mol
c) 0.5 mol
d) 1 mol
Answer: b) 0.25 mol

Q47. 2.24 L of N₂ at STP contains molecules:
a) 6.022 × 10²³
b) 1.204 × 10²³
c) 2.688 × 10²²
d) 3.011 × 10²³
Answer: b) 6.022 × 10²² (approx)

Q48. Percentage of oxygen in H₂O is:
a) 16%
b) 33%
c) 50%
d) 88.9%
Answer: d) 88.9%

Q49. Equivalent mass of H₂SO₄ in H₂SO₄ → HSO₄⁻ is:
a) 49
b) 98
c) 24.5
d) 32
Answer: a) 49

Q50. Which has maximum number of atoms?
a) 1 g H₂
b) 16 g O₂
c) 35.5 g Cl₂
d) 12 g C
Answer: a) 1 g H₂

Q51. % of C in CH₄ is:
a) 25%
b) 50%
c) 75%
d) 80%
Answer: d) 75%

Q52. In Na₂SO₄, sodium is:
a) 23%
b) 32.37%
c) 45%
d) 50%
Answer: b) 32.37%

Q53. Which has the highest number of molecules?
a) 2 g H₂
b) 32 g O₂
c) 44 g CO₂
d) 28 g N₂
Answer: a) 2 g H₂

Q54. Volume occupied by 1 g H₂ at STP is:
a) 11.2 L
b) 22.4 L
c) 44.8 L
d) 5.6 L
Answer: a) 11.2 L

Q55. 1 g atom of calcium =
a) 1 mole atoms
b) 6.022 × 10²³ atoms
c) 40 g atoms
d) All of these
Answer: d) All of these

Q56. 0.5 mole O₂ contains how many oxygen atoms?
a) 6.022 × 10²³
b) 3.011 × 10²³
c) 12.044 × 10²³
d) 9.033 × 10²³
Answer: a) 6.022 × 10²³

Q57. Normality of 1 M H₂SO₄ in neutralisation:
a) 0.5 N
b) 1 N
c) 2 N
d) 4 N
Answer: c) 2 N

Q58. 22 g CO₂ contains:
a) 0.25 mole
b) 0.5 mole
c) 1 mole
d) 2 mole
Answer: b) 0.5 mole

Q59. 2.5 mole O₂ weighs:
a) 80 g
b) 60 g
c) 40 g
d) 32 g
Answer: a) 80 g

Q60. Number of atoms in 18 g water:
a) 6.022 × 10²³
b) 12.044 × 10²³
c) 18.066 × 10²³
d) 9.033 × 10²³
Answer: c) 18.066 × 10²³