CBSE Board Class 12 Chemistry Previous Year Question Papers 2011

CHEMISTRY (Theory)
Time allowed : 3 hours ] [ Maximum Marks: 70

Please check that this question paper contains 12 printed pages.
Code number given on the right hand side of the question paper should be written on
the title page of the answer-book by the candidate.
Please check that this question paper contains 27 questions.
Please write down the serial number of the question before attempting it.

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.56/1/1 2 [P.T.O.
(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. What is the number of atoms per unit cell in a body centered cubic structure ? 1

2. Define osmotic pressure. 2

3. For the reaction 1 the rate law is expressed as rate What is the overall order ‘of this reaction ?

4. Write the IUPAC name of the compound: 1

5. Why do nitro compounds have high boiling points in comparison with other
compounds of same molecular mass ? 1

6. State ‘Pauli’s exclusion principle’. Explain giving an example how this principle
limits the maximum occupancy of an energy level in an atom. 2
OR
State ‘Aufbau principle’ and give the order in which the energies of orbitals
increase and hence they are filled in that order. 2

7. A reaction with always has an equilibrium constant value greater than 1. Why ? 2

8. Write balanced chemical equations for the following reactions : 2
(i) Aluminium dissolves in aqueous hydrochloric acid
(ii) Tin  reacts with a hot alkali solution

9. Write the structures of the following species: 2
(i) H3 PO2
(ii) H 2 SO5

10. Identify whether the following pairs of compounds are structural or geometrical
isomers : 2

11. How would you account for the following : 2
(i) Phenols are much more acidic than alcohols.
(ii) The boiling points of ethers are much lower than those of the alcohols of
comparable molar masses.

12. Draw the structure of the monomer of each of the following polymers : 2
(i) Polyvinylchloride (PVC) (ii) Nylon-6

13. Write the molecular orbital configurations of the following species and rearrange
them in the increasing order of their bond lengths: 3

14. Explain each of the following with a suitable example: 3
(i) Paramagnetism
(ii) Piezoelectric effect
(iii) Frenkel defect in crystals

15. In the production of water gas the reaction involved is : 3
For this reaction is + 134 JK _ 1 mol _1
. Find out the spontaneous feasibility of this
reaction at (i) 25°C and (ii) 1000°C.

16. An antifreeze solution is prepared from 222.6 g of ethylene glycol (C 2 H4 (OH) 2 ) and 200 g of water. Calculate the molality of the solution. If the density of this solution be  , what will be the molarity of the solution ? 3

17. The decomposition of NH 3 on platinum surface,  is a zero order reaction with  . What are the rates of production
of N 2 and H 2 ?

18. Explain the following terms giving a suitable example in each case : 3
(i) Emulsification
(ii) Homogeneous catalysis
OR
Define adsorption. Write any two features which distinguish physisorption from
chemisorption. 3

19. How would you account for the following ? 3
(i) The lower oxidation state becomes more stable with increasing atomic number
in Group 13.
(ii) Hydrogen fluoride is much less volatile than hydrogen chloride,
(iii) Interhalogen compounds are strong oxidising agents.

20. Wr i t e   the  name   and dr aw  the   s t ruc tur e  of   e a ch of   the   fol lowing  compl ex
compounds : 3

21. The net nuclear reaction of a radioactive decay series is written as : 3
Write three pieces of information that you get from the above equation.

22. Give chemical tests to distinguish between the following pairs of compounds : 3
(i) Propanal and propanone
(ii) Methyl acetate and ethyl acetate
(iii) Benzaldehyde and benzoic acid

23. How would you achieve the following conversions : 3
(i) Nitrobenzene to aniline56/1/1 9 [P.T.O.
(ii) An  alkyl halide to a quaternary ammonium salt .
(iii) Aniline to benzonitrile
Write the chemical equation with reaction conditions in each case.

24. (i) Give an example of a hybrid propellant. 3
(ii) What are acid dyes ?
(iii) Name a food preservative which is most commonly used by food producers.

25. (a) Describe the general trends in the following properties of the first series of
the transition elements : 3
(i) Stability of +2 oxidation state
(ii) Formation of oxometal ions
(b) Assign reason for each of the following: 2
(i) Transition elements exhibit variable oxidation states
(ii) Transition metal ions are usually coloured
OR
(a) Write the steps involved in the preparation of: 3
(i) K2 Cr2 O7from Na 2 CrO4
(ii) KMnO4 from  K 2 MnO4
(iii) Calomel from corrosive sublimate
(b) What is meant by lanthanoid contraction ? What effect does it have on the
chemistry of the elements which follow lanthanoids ? 2

26. (a) Calculate the emf of the cell 3
Given :
(b) Explain with examples the terms weak and strong electrolytes. 2
OR
(a) The resistance of a conductivity cell containing 0.001 M KC1 solution at
298 K is 1500  Ω. What is the cell constant, if the conductivity of 0.001 M KCl solution at 298 K is  ? 3
(b) Predict the products of electrolysis in the following: 2
A solution of 
with platinum electrodes.

27. (a) Name the three major classes of carbohydrates and give an example of each
of these classes. 3
(b) Answer the following: 2
(i) Wha t   type  of   l inkage   i s   r e spons ibl e   for   the  pr ima ry  s t ruc tur e  of
proteins ?
(ii) Name the location where protein synthesis occurs in our body.
OR
(a) How are lipids classified ? Give an example of each class. 
(b) Explain the following terms : 2
(i) Mutarotation
(ii) Avitaminosis