CBSE Board Class 12 Chemistry Previous Year Question Papers 2010

CHEMISTRY
CLASS 12
Time allowed : 3 hours Maximum Marks : 70

General Instructions :
(i) All  questions are compulsory.
(ii) Marks for each question are indicated against it.
(iii) Question number  1 to  5 are very short-answer questions, carrying  1 mark each.
Answer these in  one  word or about  one  sentence each.
(iv) Question number  6 to  12 are short-answer questions, carrying 2 marks each.
Answer these in about  30 words each.
(v) Question number  13 to  24 are short-answer questicms of  3 marks each. Answer
these in about  40 words each.
(vi) Question number  25 to  27are long-answer questions of  5 marks each. Answer
these in about  70 words each.
(vii) Use Log Tables, if necessary. Use of calculators is not permitte

1. Find out the number of atoms per unit cell in a face-centred cubic structure having only
single atoms at its lattice points. 1

2. State the condition resulting in reverse osmosis. 1

3. Express the rate of the following reaction in terms of disappearance of hydrogen in the
reaction 1

4. Name the following compound according to IUPAC system : 1

5. Why do amines react as nucleophiles ? 1

6. (a) Write the mathematical expression for the relationship of wavelength  of a
moving particle and its momentum (p).
(b) What physical meaning is attributed to the square of the absolute value of wave
function,     ? 2
OR
State the  Heisenberg Uncertainty  Principle  and explain  as  to  why  it is  not of real
consequence when applied to a macroscopic object, like a cricket ball. 2

7. Define conductivity and molar conductivity for the solution of an electrolyte. 2

8. How would you account for the following : 2
(i) Sulphur hexafluoride is less reactive than sulphur tetrafluoride.
(ii) Of  the noble gases only xenon forms known chemical compounds.

9. On the basis of the standard electrode potential values stated for acid solution, predict
whether Ti 4+  species may be used to oxidise Fe II to Fe III   . 2

10. What are chiral objects ? Indicate the presence of centre of chirality, if any, in the
molecules of 3-bromopent-l-ene. 2

11. How may the following conversions be carried out : 2
(i) Propene to propan-2-ol
(ii) Anisole to phenol

12. Write formulae of the monomers of polythene and teflon. 2

13. Define bond order in a diatomic molecule. Find the bond order in O 2
molecule. State and explain magnetic character of molecular oxygen. 3

14. Assign reasons for the following : 3
(i) Phosphorus doped silicon is a semiconductor.
(ii) Schottky defect lowers the density of a solid.
(iii) Some of  the very old glass objects appear slightly   milky instead of  being transparent.

15. A 0.1539 molal aqueous solution of cane sugar
has a freezing
point of 271 K while the freezing point of pure  water is 273.15 K.  What will be the
freezing point of an aqueous solution containing 5 g of  glucose

16. Calculate the standard cell potential of the galvanic cell in which the following reaction
takes place : 3 Also calculate the
value of the reaction.
(Given :

17. The rate constant for a first order reaction is How much time will it take to reduce the concentration of the reactant to 1/10th   of its initial value ? 3

18. Describe the following types of colloids, giving an example for each : 3
(i) Multimolecular colloids
(ii) Macromolecular colloids
                      OR
Explain the following terms with a suitable example in each case : 3
(i) Shape-selective catalysis
(ii) Dialysis

19. How would you account for the following : 3
(i) The transition elements have high enthalpies of atomisation.
(ii) The transition metals and their compounds are found to be good catalysts in many
processes.

20. Describe for any  two  of the following complex ions, the type of hybridization, shape and
magnetic property : 3

21. Complete the following statements for nuclear reactions : 3

23. Account for any  two  of the following : 3
(a) Amines are basic substances while amides are neutral.
(b) Nitro compounds have higher boiling points than the hydrocarbons having almost
the same molecular mass.
(c) Aromatic amines are weaker bases than aliphatic amines.

24. (a) Describe and illustrate with an example each, a mordant dye and a detergent,
(b)     Give an example of a liquid .propellant. 3

25. (a) Prove that for a system which is not isolated.
b) The decomposition of Fe 2 O3 is a non-spontaneous process Show that the reduction of Fe 2 O3
by CO can be made spontaneous by coupling with the following reaction : 2, 3
OR
(a) Define the following terms :
(i) Entropy
(ii) A  spontaneous process
(b) Given below are the standard Gibbs energy changes for two reactions at 1773 K :
Discuss the possibility of reducing Al 2 O3 with carbon at this temperature. Given that :2, 3

26. (a) Assign reasons for the following :
(i) PbO2 is a stronger oxidising agent than SnO 2
(ii) In  solid state PCl 5 behaves as an ionic species,
(iii) Aluminium chloride (A1C1 3 ) is very often used as a catalyst.
(b) What is the structural difference between orthosilicates and pyrosilicates ? 3, 2
 
27. (a) Answer the following questions briefly :
(i)     What are reducing sugars ?
(ii)    What is meant by denaturation of a protein ?
(iii)   How is oxygen replenished in our atmosphere ?
(b) Define enzymes. 3, 2
                 OR
(a) Answer the following questions briefly :
(i) What are any two good sources of vitamin A ?
(ii) What are nucleotides ?
(iii) Give an example of simple lipids.
(b) How are carbohydrates classified ? 3, 2