Class XII: Chemistry – 2008 (Set I – Delhi)

February 7, 2009 by  
Filed under Class XII Question Papers

1. What is the coordination number of each type of ions in a rock-salt type crystal structure ?

2. Define the term ‘order of reaction’ for chemical reactions.

3. What causes Brownian movement in a colloidal solution ?

4. In which one of the two structures, NO2+ and NO2, the bond angle has a higher value ?

5. Write the IUPAC name of the following compound:

Image: Question 05

6. Arrange the following compounds in an increasing order of their acid strengths:

(CH3)2CHCOOH, CH3CH2CH(Br) COOH, CH3CH(Br)CH2COOH

7. Write a chemical reaction in which the iodide ion replaces the diazonium group in a diazonium salt.

8. Name a substance that can be used as an antiseptic as well as a disinfectant.

9. Explain as to why haloarenes are much less reactive than haloalkanes towards nucleophilic substitution reactions.

OR

Which compound in each of the following pairs will react faster in SN2 reaction with -OH ? Why ?

(i) CH3Br or CH3I

(ii) (CH3)3CC1 or CH3C1

10. (a) State the IUPAC name of the following compound:

Image: Question 10

(b) Complete the following chemical equation:

CH3CH2CH=CH2 + HBr –> (Presence of Peroxide)

11. State Henry’s law correlating the pressure of a gas and its solubility in a solvent and mention two applications for the law.

12. A first order decomposition reaction takes 40 minutes for 30% decomposition. Calculate its t½ value.

13. What is meant by the ‘rate constant, k’ of a reaction ? If the concentration be expressed in mol L-1 units and time in seconds, what would be the units for k (i) for a zero order reaction and (ii) for a first order reaction ?

14. Define the following terms in relation to proteins:

(i) Peptide linkage

(ii) Denaturation

15. List the reactions of glucose which cannot be explained by its open chain structure.

16. Assign a reason for each of the following statements:

(i) Ammonia is a stronger base than phosphine.

(ii) Sulphur in vapour state exhibits a paramagnetic behaviour.

17. Draw the structures of the following molecules:

(i) SF4

(ii) XcF4

18. What are biodegradable and non-biodegradable detergents ? Give one example of each class.

19. What is a semiconductor ? Describe the two main types of semiconductors and explain mechanisms for their conduction.

20. Calculate the temperature at which a solution containing 54 g of glucose, (C6H12O6), in 250 g of water will freeze.

(Kf for water = 1.86 K mol-1 kg)

21. What are lyophilic and lyophobic sols ? Give one example of each type. Which one of these two types of sols is easily coagulated and why ?

22. State briefly the principles which serve as basis for the following operations in metallurgy:

(i) Froth floatation process

(ii) Zone refining

(iii) Refining by liquation

23. Write chemical equations for the following processes:

(i) Chlorine reacts with a hot concentrated solution of sodium hydroxide

(ii) Orthophosphorous acid is heated

(iii) PtF6 and xenon are mixed together

OR

Complete the following chemical equations:

(i) Ca3P2 (s) + H2O (l) –>

(ii) Cu2+ (aq) + NH2 (aq) –>

(iii) F2 (g) + H2O (l) –>

24. (a) What is a ligand ? Give an example of a bidentate ligand.

(b) Explain as to how the two complexes of nickel, [Ni(CN)4]2- and Ni(CO)4, have different structures but do not differ in their magnetic behaviour.
(Ni = 28)

25. Name the reagents which are used in the following conversions:

(i) A primary alcohol to an aldehyde

(ii) Butan-2-one to butan-2-ol

(iii) Phenol to 2, 4, 6-tribromophenol

26. Account for the following observations:

(i) pKb for aniline is more than that for methylamine.

(ii) Methylamine solution in water reacts with ferric chloride solution to give a precipitate of ferric hydroxide.

(iii) Aniline does not undergo Friedel-Crafts reaction.

27. Write the names and structures of the monomers of the following polymers:

(i) Buna-S

(ii) Neoprene

(iii) Nylon-6

28. Conductivity of 0.00241M acetic acid solution is 7.896 × 10-5 S cm-1. Calculate its molar conductivity in this solution. If Λm0 for acetic acid be 390.5 S cm2mol-1, what would be its dissociation constant ?

OR

Three electrolytic cells A, B and C containing solutions of zinc sulphate, silver nitrate and copper sulphate, respectively are connected in series. A steady current of 1.5 ampere was passed through them until 1.45 g of silver were deposited at the cathode of cell B. How long did the current flow ? What mass of copper and what mass of zinc were deposited in the concerned cells ? (Atomic masses of Ag = 108, Zn = 65.4, Cu = 63.5)

29. Assign reasons for the following:

(i) The enthalpies of atomisation of transition elements are high.

(ii) The transition metals and many of their compounds act as good catalyst.

(iii) From element to element the actinoid contraction is greater than the lanthanoid contraction.

(iv) The E0 value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.

(v) Scandium (Z = 21) does not exhibit variable oxidation states and yet it is regarded as a transition element.

OR

(a) What may be the possible oxidation states of the transition metals with the following d electronic configurations in the ground state of their atoms:

3d34s2. 3d54s2 and 3d64s2. Indicate relative stability of oxidation states in each case.

(b) Write steps involved in the preparation of (i) Na2CrO4 from chromite ore and (ii) K2MnO4 from pyrolusite ore.

30.

(a) Complete the following reaction statements by giving the missing starting material, reagent or product as required:

Image: Question 30

(b) Describe the following reactions:

(i) Cannizaro reaction

(ii) Cross aldol condensation

OR

(a) How would you account for the following:

(i) Aldehydes are more reactive than ketones towards nucleophiles.

(ii) The boiling points of aldehydes and ketones are lower than of the corresponding acids.

(iii) The aldehydes and ketones undergo a number of addition reactions.

(b) Give chemical tests to distinguish between:

(i) Acetaldehyde and benzaldehyde

(ii) Propanone and propanol

Table of contents for CBSE XII Papers 2008

  1. Class XII: Chemistry – 2008 (Set I – Delhi)

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