Chemistry · Sample Paper 3

General instructions

Section A · Objective

1. Question 11 mark

   Which concentration unit is temperature-independent?

   1. A.molarity
   2. B.normality
   3. C.mole fraction
   4. D.formality
2. Question 21 mark

   The osmotic pressure of a solution is given by

   1. A.π = CRT
   2. B.π = RT/C
   3. C.π = C/RT
   4. D.π = nR/T
3. Question 31 mark

   In a galvanic cell, oxidation takes place at the

   1. A.cathode
   2. B.anode
   3. C.salt bridge
   4. D.electrolyte
4. Question 41 mark

   The Nernst equation relates electrode potential to

   1. A.temperature only
   2. B.concentration of ions
   3. C.pressure only
   4. D.time
5. Question 51 mark

   The rate of a reaction generally increases with

   1. A.decrease in temperature
   2. B.increase in concentration of reactants
   3. C.removal of catalyst
   4. D.decrease in surface area
6. Question 61 mark

   The half-life of a first-order reaction

   1. A.depends on initial concentration
   2. B.is independent of initial concentration
   3. C.doubles each time
   4. D.is zero
7. Question 71 mark

   Which of these is NOT a transition element?

   1. A.Fe
   2. B.Cu
   3. C.Zn
   4. D.Cr
8. Question 81 mark

   The oxidation state of Fe in $[Fe(CN{)}_6{]}^{4-}$ is

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

   The product of the reaction of an alkyl halide with alcoholic KOH is mainly an

   1. A.alcohol
   2. B.alkene
   3. C.ether
   4. D.alkane
10. Question 101 mark

    Which alcohol reacts fastest with Lucas reagent?

    1. A.primary
    2. B.secondary
    3. C.tertiary
    4. D.methanol
11. Question 111 mark

    Fehling's solution is reduced by

    1. A.ketones
    2. B.aldehydes (aliphatic)
    3. C.carboxylic acids
    4. D.esters
12. Question 121 mark

    The bond linking amino acids in proteins is the

    1. A.glycosidic bond
    2. B.peptide bond
    3. C.ester bond
    4. D.hydrogen bond
13. Question 131 mark

    Assertion (A): Copper does not liberate hydrogen from dilute HCl.

    Reason (R): Copper has a positive standard reduction potential.

    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): Transition metals are good catalysts.

    Reason (R): They show variable oxidation states and can form intermediate complexes.

    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): Aniline does not undergo Friedel–Crafts reaction.

    Reason (R): The amino group forms a salt with the Lewis acid AlCl₃, deactivating the 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.
16. Question 161 mark

    Assertion (A): Sucrose is a reducing sugar.

    Reason (R): Sucrose on hydrolysis gives glucose and fructose.

    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

   Calculate the freezing point of a solution of 3.42 g of sucrose ($C_{12}{H}_{22}{O}_{11}$) in 100 g of water. ($K_f=1.86$ K kg mol⁻¹)

2. Question 182 marks

   State Faraday's first law of electrolysis. How much charge is needed to reduce 1 mol of Cu²⁺ to Cu?

3. Question 192 marks

   For a reaction $A\to B$, the rate becomes four times when [A] is doubled. What is the order of the reaction? Write the rate law.

4. Question 202 marks

   Why do transition metals have high melting points?

5. OR

   Question 202 marks

   What is the lanthanoid contraction? Give one consequence.

6. Question 212 marks

   Why is phenol more acidic than ethanol?

Section C · Short answer

1. Question 223 marks

   State Henry's law. Give two applications.

2. Question 233 marks

   Calculate the emf of the cell $Mg|M{g}^{2+}(0.001M)||C{u}^{2+}(0.0001M)|Cu$. ($E_{M{g}^{2+}/Mg}^{\circ }=-2.37$ V, $E_{C{u}^{2+}/Cu}^{\circ }=+0.34$ V)

3. Question 243 marks

   What is activation energy? How does a catalyst affect it? Explain with an energy diagram (described).

4. Question 253 marks

   Give the IUPAC name, type of hybridisation and shape of $[Co(N{H}_3{)}_6{]}^{3+}$. Is it paramagnetic or diamagnetic?

5. OR

   Question 253 marks

   Explain the spectrochemical series. Why is [Ti(H₂O)₆]³⁺ violet?

6. Question 263 marks

   What is a racemic mixture? Explain optical activity with an example of a chiral molecule.

7. Question 273 marks

   How will you distinguish between: (i) propanal and propanone (ii) benzoic acid and phenol (iii) ethanal and benzaldehyde?

8. Question 283 marks

   Give one chemical test to distinguish between (i) methylamine and dimethylamine (ii) aniline and benzylamine (iii) ethylamine and aniline.

Section D · Case-based

1. Question 294 marks

   Case study — Saline drips. Doctors give patients 0.9% (mass/volume) sodium chloride solution intravenously. This solution has the same osmotic pressure as blood. If red blood cells are placed in a more concentrated salt solution, they shrink; in pure water, they swell and burst.

   (i) What are solutions with the same osmotic pressure called? (1 mark)

   (ii) Why do red blood cells shrink in a concentrated salt solution? (1 mark)

   (iii) Explain reverse osmosis and one of its uses. (2 marks)

   OR

   (iii) Why is osmotic pressure the preferred method for finding the molar mass of proteins? (2 marks)

2. Question 304 marks

   Case study — Alcohol as fuel. Ethanol, made by fermenting molasses, is blended with petrol in India (E20 fuel). Methanol is highly poisonous; even small quantities can cause blindness. Ethanol meant for industrial use is made unfit for drinking by adding substances like copper sulphate and pyridine.

   (i) Name the enzyme that converts glucose into ethanol. (1 mark)

   (ii) What is denatured alcohol? (1 mark)

   (iii) Write the equations for (a) dehydration of ethanol to ethene (b) oxidation of ethanol to ethanoic acid. (2 marks)

   OR

   (iii) How can methanol and ethanol be distinguished chemically? (2 marks)

Section E · Long answer

1. Question 315 marks

   (a) Derive the expression for the half-life of a first-order reaction. (b) A first-order reaction takes 40 minutes for 30% decomposition. Calculate its rate constant and half-life. (log 7 = 0.845)

2. OR

   Question 315 marks

   (a) What is a fuel cell? Describe the H₂–O₂ fuel cell with electrode reactions. (b) Calculate the standard Gibbs energy change for the reaction $Zn+C{u}^{2+}\to Z{n}^{2+}+Cu$, given $E_{cell}^{\circ }=1.1$ V.

3. Question 325 marks

   An aromatic compound A on treatment with aqueous ammonia and heating forms B, which on heating with Br₂ and KOH forms C (C₆H₇N). Identify A, B and C and write the reactions. Give one test for C.

4. OR

   Question 325 marks

   Explain with equations: (i) Gabriel phthalimide synthesis (ii) Hofmann bromamide degradation (iii) coupling reaction of benzenediazonium chloride with aniline. Why can't aromatic primary amines be prepared by Gabriel synthesis?

5. Question 335 marks

   (a) What are the structural differences between DNA and RNA? (b) What are essential and non-essential amino acids? Give one example of each. (c) What is the primary structure of a protein?