Question Paper Sets of Chemistry

Chapters: Some Basic Concepts of Chemistry & Atomic Structure

🔷 SET – 1

Class XI – Chemistry Question Paper (Set 1)

Chapters: Some Basic Concepts of Chemistry & Atomic Structure
Maximum Marks: 50  Time: 1½ Hours

Section A: Multiple Choice Questions (1 × 10 = 10 marks)

  1. The SI unit of molarity is:
    A. g/mol B. mol/L C. mol/kg D. L/mol
  2. One mole of Na contains how many atoms?
    A. 6.022 × 10²³ B. 23 C. 1 D. 3.01 × 10²³
  3. Limiting reagent is:
    A. Reactant not used at all
    B. Product formed in excess
    C. Reactant that finishes first
    D. Product formed least
  4. Which of the following orbitals is not possible?
    A. 1s B. 2d C. 3p D. 4f
  5. In which shell will the fifth period elements begin to fill electrons?
    A. n=3 B. n=4 C. n=5 D. n=6
  6. Which element has the configuration 1s² 2s² 2p⁶ 3s² 3p¹?
    A. B B. Al C. Si D. Mg
  7. Dalton’s atomic theory could not explain:
    A. Law of conservation of mass
    B. Law of definite proportions
    C. Existence of isotopes
    D. Law of multiple proportions
  8. What is the maximum number of electrons in ‘d’ subshell?
    A. 6 B. 10 C. 14 D. 2
  9. What is the quantum number ‘m’ used for?
    A. Shape B. Orientation C. Spin D. Size
  10. 22.4 L of a gas at STP weighs 44 g. What is its molar mass?
    A. 22.4 g B. 44 g C. 11.2 g D. 88 g

Section B: Assertion & Reason (1 × 2 = 2 marks)

  1.  

Assertion (A): The mass of 1 mole of CO₂ is 44 g.
Reason (R): Molar mass is numerically equal to molecular weight expressed in grams.

(Options: A/B/C/D)

Section C: Case-Based Question (1 × 3 = 3 marks)

  1. A compound contains C, H, and O. On combustion, it produces CO₂ and H₂O.
    (a) Name the law followed during combustion.
    (b) How can you calculate empirical formula from % composition?
    (c) What is the molar mass of CO₂?

Section D: Short Answer Questions (2 × 5 = 10 marks)

  1. Define Avogadro’s constant and write its value.
  2. Write any two limitations of Rutherford’s atomic model.
  3. How many atoms are present in 0.5 mol of O₂ gas?
  4. What is meant by mole? Calculate moles in 9 g of H₂O.
  5. Explain the terms orbit and orbital.

Section E: Numericals and Quantum Concepts (3 × 3 = 9 marks)

  1. Molality: Calculate molality of a solution containing 4.6 g NaOH in 200 g water. (Na=23, O=16, H=1)
  2. Electronic transition: Calculate energy required for transition from n=1 to n=3 in hydrogen atom.
  3. Write quantum numbers for the valence electron in sodium (Z = 11).

Section F: Long Answer Questions (5 × 2 = 10 marks)

  1. Calculate empirical and molecular formula of a compound with 80% C and 20% H, molar mass = 30.
  2. State and explain Bohr’s postulates with limitations.

🔷 SET – 2

Class XI – Chemistry Question Paper (Set 2)

Section A: MCQs (10 × 1 = 10 marks)

  1. One mole of any gas at STP occupies:
    A. 1 L B. 11.2 L C. 22.4 L D. 44.8 L
  2. Relative atomic mass is measured in:
    A. grams B. kg C. amu D. mol
  3. Maximum number of electrons in p-subshell is:
    A. 2 B. 6 C. 10 D. 14
  4. Shape of s orbital is:
    A. Dumbbell B. Spherical C. Elliptical D. Circular
  5. The number of neutrons in ⁴⁰Ca is:
    A. 20 B. 40 C. 0 D. 10
  6. Limiting reagent determines:
    A. The rate of reaction
    B. Time taken
    C. Amount of product formed
    D. Catalyst
  7. 1 mole of H₂O has:
    A. 6.022 × 10²³ molecules B. 1 molecule C. 2 atoms D. 6 g
  8. Atomic number is equal to:
    A. Number of protons B. Number of neutrons C. Mass number D. None
  9. In Bohr’s model, angular momentum is:
    A. Quantized B. Constant C. Zero D. Infinite
  10. Who discovered the electron?
    A. Bohr B. Chadwick C. J.J. Thomson D. Rutherford

Assertion & Reason (1 × 2 = 2 marks)

  1.  

A: Isotopes of an element have the same chemical properties.
R: They have same number of protons and electrons.

Case-Based (3 marks)

  1. 10 g of calcium carbonate was heated to produce calcium oxide and CO₂.
    (a) Name the gas evolved.
    (b) What law is shown by the conservation of mass?
    (c) Write the balanced chemical equation.

Short Answer (2 × 5 = 10 marks)

  1. Define atomic number and mass number.
  2. Calculate number of moles in 28 g of N₂.
  3. What is the relation between molar mass and density?
  4. What is Hund’s rule of maximum multiplicity?
  5. What are orbitals? Name four types.

Numericals & Concepts (3 × 3 = 9 marks)

  1. Molality: 10 g glucose in 90 g water (C₆H₁₂O₆ = 180).
  2. Transition energy: n=2 to n=5 in hydrogen atom.
  3. Write quantum numbers for 15th electron of P (Z = 15).

Long Answer (5 × 2 = 10 marks)

  1. Derive de Broglie’s equation. Mention its significance.
  2. Empirical formula of 75% C, 25% H. Molar mass = 32. Find molecular formula.

🔷 SET – 3

Class XI – Chemistry Question Paper (Set 3)

Section A: MCQs (10 × 1 = 10 marks)

  1. Molar mass of H₂SO₄ is:
    A. 98 g B. 100 g C. 49 g D. 196 g
  2. The SI unit of energy:
    A. Watt B. Joule C. Calorie D. Volt
  3. Who gave the quantum mechanical model?
    A. Bohr B. Schrödinger C. Heisenberg D. Thomson
  4. Maximum number of orbitals in 3rd shell:
    A. 4 B. 9 C. 3 D. 6
  5. Electron configuration of Nitrogen:
    A. 1s²2s²2p³ B. 1s²2s²2p⁶ C. 1s²2s¹2p⁴ D. 1s¹
  6. Avogadro number is used to relate:
    A. Atoms to grams B. Molecules to grams C. Particles to moles D. All of these
  7. Which quantum number is not needed to locate an electron?
    A. n B. l C. m D. Density
  8. Which is not a valid orbital?
    A. 2s B. 3p C. 1d D. 4f
  9. Limiting reagent affects:
    A. Time B. Amount of reactants C. Product formed D. Rate of reaction
  10. In Rutherford’s experiment, most alpha particles passed through because:
    A. Nucleus is dense B. Atom is solid C. Atom is mostly empty D. Alpha rays are small

Assertion & Reason

  1.  

A: Electrons revolve around nucleus in fixed paths.
R: This is according to Heisenberg’s principle.

Case-Based

  1. 2.5 mol of a gas occupies 56 L at constant temperature.
    (a) Find molar volume.
    (b) Name the law used.
    (c) If 1 mol of gas is taken, what volume would it occupy?

Short Answer (2 × 5 = 10 marks)

  1. Define atomicity with examples.
  2. How are isotopes used in medicine?
  3. Difference between orbit and orbital (2 points).
  4. Find mass of 0.25 mol of methane (CH₄).
  5. Define molar mass and equivalent mass.

Numerical/Transition/Quantum (3 × 3 = 9 marks)

  1. Molality: 9.8 g H₂SO₄ in 100 g water.
  2. Transition: Electron from n=5 to n=2, hydrogen atom.
  3. Write quantum numbers for 26th electron of Fe (Z = 26).

Long Answer (5 × 2 = 10 marks)

  1. Derive relationship between molar volume and Avogadro’s number.
  2. 40% C, 6.7% H, 53.3% O, molar mass = 60 → find empirical & molecular formula.

✅ SET – 1 Answer Key

Section A – MCQs:

  1. B
  2. A
  3. C
  4. B
  5. C
  6. B
  7. C
  8. B
  9. B
  10. B

Section B – Assertion & Reason:

  1. A – Both A and R are true, and R is the correct explanation.

Section C – Case-Based:

  1.  

(a) Law of Conservation of Mass
(b) By converting % composition into moles and finding simplest ratio.
(c) 44 g/mol

Section D – Short Answer:

  1. Avogadro’s number: 6.022 × 10²³ mol⁻¹
  2. Limitation: electrons should collapse into nucleus (not explained).
  3. 0.5 mol O₂ = 0.5 × 6.022 × 10²³ = 3.011 × 10²³ molecules
  4. 9 g H₂O: Molar mass = 18 → moles = 9/18 = 0.5 mol
  5. Orbit = path; Orbital = region of high probability

Section E – Numericals:

  1. Molality = (4.6 / 40) / 0.2 = 0.575 mol/kg
  2. ΔE = 13.6 × (1 – 1/9) = 12.09 eV
  3. Na (Z = 11): n=3, l=0, m=0, s=+½

Section F – Long Answer:

  1. Empirical: CH₃; Molecular = C₂H₆
  2. Bohr’s postulates with equations + limitations: elliptical orbits, multi-electron atoms not explained.

✅ SET – 2 Answer Key

Section A – MCQs:

  1. C
  2. C
  3. B
  4. B
  5. A
  6. C
  7. A
  8. A
  9. A
  10. C

Section B – Assertion & Reason:

  1. A – Both A and R are true and R explains A.

Section C – Case-Based:

  1.  

(a) CO₂
(b) Law of Conservation of Mass
(c) CaCO₃ → CaO + CO₂

Section D – Short Answer:

  1. Atomic number = protons, Mass number = protons + neutrons
  2. Moles = 28 / 28 = 1 mol
  3. M = dRT/P
  4. All orbitals in a subshell are singly occupied before pairing
  5. Orbitals are regions; s, p, d, f

Section E – Numericals:

  1. Molality = (10 / 180) / 0.09 = 0.617 mol/kg
  2. E = 13.6 × (1/4 – 1/25) = 2.856 eV
  3. 15th electron of P: 3p¹ → n=3, l=1, m=0, s=+½

Section F – Long Answer:

  1. de Broglie: λ = h/mv
  2. Empirical: CH₄, Molar = 16 → CH₄

✅ SET – 3 Answer Key

Section A – MCQs:

  1. A
  2. B
  3. B
  4. B
  5. A
  6. D
  7. D
  8. C
  9. C
  10. C

Section B – Assertion & Reason:

  1. C – A is true but R is false

Section C – Case-Based:

  1.  

(a) Molar volume = 56/2.5 = 22.4 L/mol
(b) Avogadro’s law
(c) 22.4 L

Section D – Short Answer:

  1. Atomicity = number of atoms in molecule, O₂ → 2
  2. Cobalt-60 in cancer therapy
  3. Orbit = path, Orbital = probability region
  4. 0.25 mol × 16 = 4 g
  5. Molar mass = mass per mole; Eq. mass = mass/valency

Section E – Numericals:

  1. Molality = (9.8 / 98) / 0.1 = 1 mol/kg
  2. E = 13.6 × (1/4 – 1/25) = 2.856 eV
  3. Fe (Z=26) → 3d⁶, 26th e⁻ = 3d↑, n=3, l=2, m=0, s=+½

Section F – Long Answer:

  1. Volume of 1 mol gas = 22.4 L, use N = n × NA
  2.  
  • %C = 40/12 = 3.33
  • %H = 6.7/1 = 6.7
  • %O = 53.3/16 = 3.33
    → Empirical = CH₂O; Molar = 60
    → Molecular formula = C₂H₄O₂

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