✍️ Chemistry – XI
September Test 2025 – SAMPLE PAPER SET 3
Time Allowed: 3 hrs.
Maximum Marks: 70
Note:
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Q.No. 1 has 20 parts carrying 1 mark each
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Q.No. 2 to 15 carry 2 marks each
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Q.No. 16 to 19 carry 3 marks each
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Q.No. 20 to 21 carry 5 marks each
SECTION – A (Each question 1 mark)
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The molar mass of CaCO₃ is:
(a) 40 g
(b) 44 g
(c) 100 g
(d) 60 g -
Which of the following has 2 significant figures?
(a) 0.0032
(b) 0.0320
(c) 3.20 × 10³
(d) 32.00 -
The number of oxygen atoms in 9.0 g of water is:
(a) 3 × 10²³
(b) 6 × 10²³
(c) 1 × 10²³
(d) 18 × 10²³ -
Which of the following concentration terms is independent of both temperature and pressure?
(a) Normality
(b) Molality
(c) Molarity
(d) Volume strength -
A d-orbital can accommodate a maximum of:
(a) 2 electrons
(b) 6 electrons
(c) 10 electrons
(d) 14 electrons -
Which quantum number describes the orientation of orbitals?
(a) Principal quantum number (n)
(b) Azimuthal quantum number (l)
(c) Magnetic quantum number (m)
(d) Spin quantum number (s) -
The tendency of atoms to pair electrons singly before pairing is explained by:
(a) Hund’s rule
(b) Pauli’s principle
(c) Aufbau principle
(d) Octet rule -
In Bohr’s model, the radius of nth orbit of hydrogen atom is proportional to:
(a) n²
(b) 1/n²
(c) n
(d) 1/n -
The de Broglie wavelength of an electron accelerated through potential difference V is proportional to:
(a) √V
(b) 1/√V
(c) V
(d) 1/V -
The hybridisation of carbon in HCN molecule is:
(a) sp
(b) sp²
(c) sp³
(d) sp³d
Comprehension
Read the passage and answer:
Group 1 elements are called alkali metals. They have one electron in their outermost shell with general configuration ns¹. They are highly reactive, form unipositive ions, and show strong metallic character. They have low ionisation enthalpy, large atomic radii, and low density. Alkali metals form colourless ionic compounds and their salts are highly soluble in water.
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What is the general electronic configuration of alkali metals?
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Why do alkali metals show strong metallic character?
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Write one physical property that decreases down the group.
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Why are alkali metal salts generally soluble in water?
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Give one use of sodium or potassium.
True / False
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Dalton’s atomic theory assumes atoms are indivisible. (T/F)
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The orbital designation for n=2, l=1 is 2p. (T/F)
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The bond angle in BF₃ is 120°. (T/F)
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Atomic radius increases from left to right across a period. (T/F)
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Transition metals are generally good catalysts. (T/F)
SECTION – B (Each question 2 marks)
Q2. Define law of conservation of mass and law of constant proportion with examples.
Q3. Calculate:
(i) Number of molecules in 0.25 mol of NH₃.
(ii) Mass of 2.0 × 10²³ atoms of Ca.
Q4. Calculate the mass percent of carbon in glucose (C₆H₁₂O₆).
Q5. Distinguish between isotopes and isobars with examples.
Q6. Write down the shapes of orbitals corresponding to l = 0 and l = 2.
Q7. Why does fluorine have higher electronegativity than chlorine?
Q8. Define electron shielding effect. How does it influence periodic properties?
Q9. Differentiate between ionic radius and atomic radius.
Q10. Explain why CO₂ molecule is linear in shape using VSEPR theory.
Q11. How many electrons can have:
(a) n=4, l=2
(b) n=2, ms = −½
Q12. A light wave has a frequency of 6 × 10¹⁴ Hz. Calculate its wavelength.
Q13. Explain why Na⁺ and Mg²⁺ ions are smaller in size than their parent atoms.
Q14. What is resonance? Explain with reference to carbonate ion (CO₃²⁻).
Q15. Determine the formal charge on each atom of NO₂ molecule.
SECTION – C (Each question 3 marks)
Q16. Define molar volume of a gas. Calculate the volume occupied by 0.5 mol of an ideal gas at STP.
Q17. Write the electronic configuration of Mn²⁺, Cl⁻, and Al³⁺ ions.
Q18. Derive the relation between energy and frequency using Planck’s quantum theory.
OR
Explain the dual behaviour of matter with an example.
Q19. (i) Draw the Lewis structure of SO₂.
(ii) Explain the type of hybridisation involved in SO₂.
SECTION – D (Each question 5 marks)
Q20. Draw the molecular orbital diagram of CO molecule. Calculate its bond order and predict magnetic property.
OR
Explain the concept of resonance energy. Describe resonance in benzene with diagrams.
Q21. (i) Define normality. Calculate the normality of solution obtained by dissolving 4.9 g of H₂SO₄ in 250 mL of solution.
(ii) State and explain the law of reciprocal proportion.
OR
(i) Explain the term equivalent mass.
(ii) Calculate the amount of nitrogen dioxide formed when 4 g of oxygen reacts with excess NO.
