Chemistry – XI September Test 2025 – SAMPLE PAPER SET 2 Time Allowed: 3 hrs. Maximum Marks: 70

 

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✍️ Chemistry – XI

September Test 2025 – SAMPLE PAPER SET 2
Time Allowed: 3 hrs.
Maximum Marks: 70

Note:

• Q.No. 1 has 20 parts carrying 1 mark each

• Q.No. 2 to 15 carry 2 marks each

• Q.No. 16 to 19 carry 3 marks each

• Q.No. 20 to 21 carry 5 marks each

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SECTION – A (Each question 1 mark)

1. The number of moles in 11.2 L of CO₂ at STP is:
   (a) 0.25
   (b) 0.5
   (c) 1
   (d) 2

2. Which of the following has 4 significant figures?
   (a) 0.00450
   (b) 4.500
   (c) 0.0450
   (d) 0.0045

3. The number of moles of hydrogen atoms in 18 g of water is:
   (a) 2
   (b) 1
   (c) 18
   (d) 36

4. Which of the following does not depend on temperature?
   (a) Molarity
   (b) Molality
   (c) Volume molar
   (d) Vapour pressure

5. The maximum number of electrons in an orbital is:
   (a) 1
   (b) 2
   (c) 4
   (d) 6

6. Which quantum number gives information about the shape of orbitals?
   (a) n
   (b) l
   (c) m
   (d) s

7. The tendency of atoms to complete 8 electrons in their valence shell is called:
   (a) Octet rule
   (b) Doublet rule
   (c) Duplet rule
   (d) Hund’s rule

8. According to Bohr’s theory, energy of an electron in the 3rd orbit is proportional to:
   (a) 1/n²
   (b) n²
   (c) 1/n
   (d) n

9. The wavelength of a particle of mass 10⁻³ kg moving with a speed of 10⁻² m/s is nearly:
   (a) 6.6 × 10⁻²⁹ m
   (b) 6.6 × 10⁻³¹ m
   (c) 6.6 × 10⁻³³ m
   (d) 6.6 × 10⁻³⁵ m

10. The hybridisation of BeCl₂ molecule is:
    (a) sp
    (b) sp²
    (c) sp³
    (d) sp³d

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Comprehension

Read the passage carefully and answer the following:

The noble gases are elements of group 18. They have general configuration ns² np⁶ (except He: 1s²). They are chemically inert due to fully filled orbitals. Their ionisation enthalpy values are very high, and electron gain enthalpies are positive. They exist as monoatomic gases under normal conditions.

11. What is the general electronic configuration of noble gases?

12. Why are noble gases chemically inert?

13. Why do they exist as monoatomic gases?

14. Write one use of helium and argon.

15. Why do noble gases have high ionisation enthalpy?

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True / False

16. Avogadro’s law states that equal masses of gases contain equal numbers of molecules. (T/F)

17. The orbital designation for n=3, l=2 is 3d. (T/F)

18. Covalent bonds are formed by sharing of electron pairs. (T/F)

19. First ionisation energy of alkali metals is very high. (T/F)

20. Group 1 elements are called alkali metals. (T/F)

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SECTION – B (Each question 2 marks)

Q2. Define molecular mass and molar mass with one example each.

Q3. Calculate:
(i) Number of atoms in 0.5 mol of oxygen gas (O₂).
(ii) Mass of 3 × 10²³ molecules of CO₂.

Q4. Calculate mass % of hydrogen and sulphur in H₂SO₄.

Q5. Distinguish between orbital and subshell.

Q6. Draw and describe the shape of s and d-orbitals.

Q7. Why do alkali metals have the lowest ionisation enthalpy in their periods?

Q8. Define electron affinity. Why is it negative for most elements?

Q9. Distinguish between ionic bond and covalent bond.

Q10. According to VSEPR theory, explain the shape of H₂O molecule.

Q11. How many electrons in an atom can have:
(a) n=3, ms = +½
(b) n=2, l=1

Q12. Calculate the frequency of light whose wavelength is 3 × 10⁻⁷ m.

Q13. Define isoelectronic species. Name a species isoelectronic with Na⁺ and O²⁻.

Q14. Define hydrogen bonding. Give two examples where H-bonding plays a role.

Q15. Calculate the formal charge on each atom in the CO₂ molecule.

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SECTION – C (Each question 3 marks)

Q16. Define mole concept. Write relation between mole, volume, and number of particles.

Q17. Write the electronic configuration of K⁺, O²⁻, and Fe³⁺ ions.

Q18. Using Heisenberg uncertainty principle, explain why electron cannot exist inside nucleus.

OR
Calculate the energy associated with the second orbit of hydrogen atom.

Q19. (i) Draw the Lewis structure of CH₄ and C₂H₄.
(ii) Mention the type of hybridisation of C in each case.

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SECTION – D (Each question 5 marks)

Q20. Draw the molecular orbital diagram of O₂. Calculate its bond order and state magnetic behaviour.

OR
What is hybridisation? Explain with diagrams the geometry of sp, sp², and sp³ hybrid orbitals.

Q21. (i) Define molality. Calculate the molality of solution obtained by dissolving 9.8 g of H₂SO₄ in 500 g of water.
(ii) State and explain the law of multiple proportion.

OR
(i) What is limiting reagent?
Calculate the amount of water formed when 8 g of hydrogen reacts with 32 g of oxygen.
(ii) Calculate the mass of one mole of ¹⁶O atoms in grams.

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