Instructions
- Total Marks: 70
- Time: 3 hours
- Part A: 15 × 1 = 15 marks
- Part B: 5 × 3 = 15 marks (attempt any 5 from 8)
- Part C: 4 × 10 = 40 marks (attempt any 4 from 6)
Part A — One Mark Questions
1. Avogadro's number is ____. (a) 6.022 × 10²² (b) 6.022 × 10²³ (c) 6.022 × 10²⁴ (d) 6.022 × 10²⁰ 2. The maximum number of electrons in the 3d subshell is ____. (a) 6 (b) 8 (c) 10 (d) 14 3. Down a group, ionisation energy ____. (a) increases (b) decreases (c) no change (d) first increases then decreases 4. Which of the following is a real gas equation? (a) PV = nRT (b) (P + an²/V²)(V − nb) = nRT (c) PV = RT (d) P = nRT/V 5. A reaction with ΔH = −ve and ΔS = −ve is spontaneous ____. (a) always (b) never (c) at high T (d) at low T 6. In VSEPR, H₂O has ____ lone pairs on oxygen. (a) 0 (b) 1 (c) 2 (d) 3 7. The standard enthalpy of neutralisation of a strong acid and strong base is ____. (a) −57.3 kJ/mol (b) +57.3 kJ/mol (c) −44.0 kJ/mol (d) −285 kJ/mol 8. The IUPAC name of CH₃CH=CH₂ is ____. (a) propene (b) prop-1-ene (c) allyl (d) propylene 9. The bond order in He₂ is ____. (a) 0 (b) 0.5 (c) 1 (d) 2 10. Equilibrium constant K > 1 means ____. (a) products are favoured (b) reactants are favoured (c) equal (d) no reaction 11. Hybridisation of carbon in C₂H₂ is ____. (a) sp (b) sp² (c) sp³ (d) sp³d 12. Which has the highest electron affinity? (a) F (b) Cl (c) Br (d) I 13. Depression in freezing point is a ____ property. (a) physical (b) colligative (c) additive (d) constitutive 14. The common ion effect ____ the ionisation of a weak acid. (a) increases (b) decreases (c) has no effect (d) eliminates 15. In carbocations, the carbon is ____. (a) sp hybridised (b) sp² (c) sp³ (d) sp³d
Part B — Three Mark Questions (answer any 5)
1. Write the electronic configurations of Cr (Z = 24) and Cu (Z = 29). Why are they exceptions to the Aufbau principle? 2. A solution contains 6 g of urea (MM = 60) in 200 g of water. Calculate the boiling point elevation (Kb = 0.52 K·kg/mol). 3. Using bond energies, calculate ΔH for CH₄ + Cl₂ → CH₃Cl + HCl. [C–H: 414, Cl–Cl: 243, C–Cl: 330, H–Cl: 431 kJ/mol] 4. Explain the mesomeric effect. Give examples of +M and −M groups and their effect on ring reactivity. 5. Define solubility product (Ksp). Calculate the molar solubility of AgCl if Ksp = 1.8 × 10⁻¹⁰. 6. Why is the bond angle in NH₃ (107°) less than tetrahedral (109.5°) but greater than H₂O (104.5°)? 7. State Graham's law of diffusion. Compare the rates of diffusion of H₂ and O₂. 8. Explain the anomalous behaviour of lithium among alkali metals (any four points).
Part C — Five Mark Questions (answer any 4)
1. (a) State and explain the three rules (Aufbau, Hund's, Pauli) for filling electrons. Write the electronic configuration of Fe (Z = 26) and Fe²⁺. OR (b) Describe the quantum mechanical model of atom. Define all four quantum numbers with their possible values and significance.
2. (a) Explain the postulates of kinetic molecular theory. Derive the expression for root mean square speed. OR (b) Explain van der Waals equation for real gases. Compare ideal and real gas behaviour at different conditions of T and P.
3. (a) State Le Chatelier's principle. Apply it to explain the optimum conditions for the Contact process (SO₃ synthesis). OR (b) Explain ionic equilibrium. Discuss pH, Ka, and the common ion effect with numerical examples.
4. (a) Explain sp, sp², and sp³ hybridisation with examples. Why is the C–C–C angle in propane 112° rather than 109.5°? OR (b) Explain the types of organic reaction intermediates (carbocation, carbanion, free radical) with hybridisation, stability order, and one example each.
Answer Hints
Part A: 1-b, 2-c, 3-b, 4-b, 5-d, 6-c, 7-a, 8-b, 9-a, 10-a, 11-a, 12-b, 13-b, 14-b, 15-b
Part B key calculations:
- Q2: m = 6/60 / 0.2 = 0.5 mol/kg; ΔTb = 1 × 0.52 × 0.5 = 0.26°C; new BP = 100.26°C
- Q3: ΔH = (414 + 243) − (330 + 431) = 657 − 761 = −104 kJ/mol
- Q5: Ksp = s²; s = √(1.8 × 10⁻¹⁰) = 1.34 × 10⁻⁵ mol/L
- Q7: r(H₂)/r(O₂) = √(32/2) = √16 = 4; H₂ diffuses 4 times faster