Chemistry · Sample Paper 1

General instructions

Section A · Objective

1. Question 11 mark

   Which of these is a colligative property?

   1. A.vapour pressure
   2. B.osmotic pressure
   3. C.density
   4. D.viscosity
2. Question 21 mark

   The van 't Hoff factor for $K_2SO_4$ (complete dissociation) is

   1. A.1
   2. B.2
   3. C.3
   4. D.4
3. Question 31 mark

   The standard electrode potential of the standard hydrogen electrode is

   1. A.1 V
   2. B.0 V
   3. C.−1 V
   4. D.0.059 V
4. Question 41 mark

   On dilution, the molar conductivity of a weak electrolyte

   1. A.decreases
   2. B.increases sharply
   3. C.stays constant
   4. D.becomes zero
5. Question 51 mark

   The unit of the rate constant of a first-order reaction is

   1. A.mol L$^{-1}$ s$^{-1}$
   2. B.s$^{-1}$
   3. C.L mol$^{-1}$ s$^{-1}$
   4. D.mol
6. Question 61 mark

   The half-life of a first-order reaction is 20 min. Its rate constant is about

   1. A.0.0347 min$^{-1}$
   2. B.0.693 min$^{-1}$
   3. C.13.86 min$^{-1}$
   4. D.0.05 min$^{-1}$
7. Question 71 mark

   Which ion is colourless?

   1. A.$Cu^{2+}$
   2. B.$Zn^{2+}$
   3. C.$Fe^{3+}$
   4. D.$Mn^{2+}$
8. Question 81 mark

   The coordination number of Co in $[Co(en)_2Cl_2]^+$ is

   1. A.4
   2. B.6
   3. C.2
   4. D.3
9. Question 91 mark

   Which reacts fastest by the SN2 mechanism?

   1. A.$(CH_3)_3CBr$
   2. B.$CH_3Br$
   3. C.$(CH_3)_2CHBr$
   4. D.$CH_3CH_2Br$
10. Question 101 mark

    Phenol gives a violet colour with

    1. A.Tollens' reagent
    2. B.neutral FeCl₃
    3. C.Fehling's solution
    4. D.NaHCO₃
11. Question 111 mark

    Which compound gives the iodoform test?

    1. A.methanal
    2. B.propanal
    3. C.ethanal
    4. D.benzaldehyde
12. Question 121 mark

    Deficiency of vitamin C causes

    1. A.rickets
    2. B.scurvy
    3. C.beriberi
    4. D.night blindness
13. Question 131 mark

    Assertion (A): Aniline is a weaker base than methylamine.

    Reason (R): The lone pair on nitrogen in aniline is delocalised into the benzene ring.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
14. Question 141 mark

    Assertion (A): Benzaldehyde undergoes the Cannizzaro reaction.

    Reason (R): Benzaldehyde has no α-hydrogen atom.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
15. Question 151 mark

    Assertion (A): Zr and Hf have almost identical atomic radii.

    Reason (R): Lanthanoid contraction offsets the expected increase in size.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
16. Question 161 mark

    Assertion (A): Maltose is a reducing sugar.

    Reason (R): In maltose, the anomeric carbon of one glucose unit is free.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.

Section B · Very short answer

1. Question 172 marks

   18 g of glucose is dissolved in 1 kg of water. Find the elevation in boiling point. ($K_b = 0.52$ K kg mol⁻¹)

2. Question 182 marks

   Calculate $\Delta G^\circ$ for a cell with $E^\circ_{cell} = 1.1$ V and $n = 2$.

3. Question 192 marks

   Differentiate between order and molecularity of a reaction (two points).

4. OR

   Question 192 marks

   For a first-order reaction, show that the time for 99% completion is twice the time for 90% completion.

5. Question 202 marks

   Write the IUPAC names of (i) $[Co(NH_3)_6]Cl_3$ (ii) $K_3[Fe(CN)_6]$.

6. Question 212 marks

   Why are haloarenes less reactive than haloalkanes towards nucleophilic substitution? (Two reasons.)

Section C · Short answer

1. Question 223 marks

   State Raoult's law. What are positive and negative deviations? Give one example of each.

2. Question 233 marks

   Write the Nernst equation and calculate the emf of the cell $Zn|Zn^{2+}(0.1\,M)\,||\,Cu^{2+}(0.01\,M)|Cu$ at 298 K. ($E^\circ_{cell} = 1.10$ V)

3. Question 243 marks

   The rate constant of a reaction doubles when the temperature rises from 300 K to 310 K. Calculate the activation energy.

4. Question 253 marks

   Give reasons: (i) Transition metals form coloured ions. (ii) They show variable oxidation states. (iii) Mn²⁺ is more stable than Fe²⁺ towards oxidation.

5. Question 263 marks

   Using valence bond theory, explain the hybridisation, shape and magnetic nature of $[Ni(CN)_4]^{2-}$.

6. OR

   Question 263 marks

   Explain crystal field splitting in an octahedral complex. What decides whether a complex is high spin or low spin?

7. Question 273 marks

   Write equations for: (i) Kolbe's reaction (ii) Reimer–Tiemann reaction (iii) Williamson ether synthesis.

8. Question 283 marks

   How will you distinguish: (i) primary, secondary and tertiary amines (Hinsberg test)? (ii) aniline from ethylamine?

Section D · Case-based

1. Question 294 marks

   Case study — Fuel cells. Hydrogen–oxygen fuel cells powered the Apollo missions and today drive some buses. Hydrogen and oxygen are fed continuously to porous carbon electrodes in hot aqueous KOH; the only product is water.

   (i) Write the reactions at the anode and the cathode. (2 marks)

   (ii) Give one advantage of fuel cells over ordinary batteries. (1 mark)

   (iii) Why is the efficiency of a fuel cell higher than that of a thermal power plant? (1 mark)

   OR

   (iii) What is corrosion? Give one method to prevent it. (1 mark)

2. Question 304 marks

   Case study — Proteins and enzymes. Proteins are polymers of α-amino acids. Their structure has four levels; heating or changing pH can destroy the higher levels without breaking peptide bonds. Enzymes are proteins that catalyse specific reactions in the body.

   (i) What is a peptide bond? (1 mark)

   (ii) What is denaturation? Give one example. (1 mark)

   (iii) Distinguish between fibrous and globular proteins with one example each. (2 marks)

   OR

   (iii) What are essential amino acids? Name two. (2 marks)

Section E · Long answer

1. Question 315 marks

   Define osmotic pressure. A solution of 0.5 g of a protein in 100 mL of water shows an osmotic pressure of 0.0124 bar at 300 K. Find its molar mass ($R = 0.083$ L bar K⁻¹ mol⁻¹). Why is osmotic pressure preferred for macromolecules?

2. OR

   Question 315 marks

   Derive the integrated rate equation for a first-order reaction. A first-order reaction is 25% complete in 30 min. Find the rate constant and half-life. ($\log\tfrac43 = 0.125$)

3. Question 325 marks

   An organic compound A (C₂H₄O) gives a silver mirror with Tollens' reagent and a positive iodoform test. On oxidation it gives B (C₂H₄O₂), which liberates CO₂ with NaHCO₃. A undergoes aldol condensation. Identify A and B and write all the reactions.

4. Question 335 marks

   Explain the S_N1 mechanism of hydrolysis of tert-butyl bromide. Why does it proceed with racemisation for optically active substrates? Write the Wurtz–Fittig reaction.

5. OR

   Question 335 marks

   Write the preparation of benzenediazonium chloride and give four reactions in which the diazo group is replaced or coupled.