CBSE Sample Paper Class XII, Chemistry 2006

CBSE SAMPLE PAPER

CHEMISTRY (Theory)

CLASS XII

 

Time allowed: 3 Hours                                                                      Maximum Marks:70

 

General Instructions:

  1. All Questions are compulsory.
  2. Marks for each question are indicated against it.
  3. Question numbers from 1 to 5 are very short answer, carrying 1 mark each. 
  4. Answer these in one word or about one sentence each.
  5. Question numbers 6 to 12 are short answer, carrying 2 marks each. Answer these in about 30 words each.
  6. Question numbers 13 to 24 are short answer, carrying 2 marks each. Answer these in about 40 words each.
  7. Question numbers 25 to 27 are short answer, carrying 2 marks each. Answer these in about 70 words each.
  8. Use log tables if necessary. Use of calculators is not permitted.

 

  1. What type of coordination is possible when the cation-anion radius ratio  is in the range 0.414-0.732?                                                                                                (1)

 

  1. State any two characteristics of ideal solution.                                                                        (1)

 

  1. The rate of decomposition of a substance is doubled when its concentration is doubled. What is the order of the reaction?                                                                   (1)

 

  1. Give one chemical test to distinguish between nitro ethane and ethyl nitrite               (1)

 

  1. Which of the aldehydes undergo Cannizarro’s reaction?                                            (1)

 

  1. The speed of an electron moving at 600 ms-1 is measured to an accuracy of 0.005%. What will be minimum error in determining its position? (me=9.1 x 10-31 kg,          h=6.6 x 10-31).                                                                                                                         (2)

                                                     OR                                                                                                               Discuss the shape of PCl5 and SF6 on basis of hybridization                                          (2)

7.  Define coupled reaction with an example.         (2)

8.  Compare the structures of SO3 and SeO3.        (2)

9.  What are interstitial compounds? Mention their two important properties               (2)

10. What is stereo specific reaction? Give one example.                                           (2)

 

11. How will you prepare Nylon-6? Give one of its uses.                                           (2)

12. Explain the mechanism of acid catalyzed dehydration of ethanol at high temperature.                                                                                                  (2)

 

13. Compare the relative stability of the following species and indicate their magnetic   properties O2,O2+,O2,O22-.                                                                                           (3)

 

OR

How can one non-polar molecule induce a dipole in a nearby non-polar molecule?

                                                                                                                                                            (3)

 

14. Silver crystallizes in fcc lattice. If the edge length of the cell is 4.077×10-8 cm and density is 10.5 g cm-3, calculate the atomic mass of silver.                                           (3)

 

15. Phenol associates in benzene to certain extent to from dimmer. A solution contains 20 x 10-3 kg of phenol in Kf  of benzene has its freezing point decreased by 0.61 K. Calculate the fraction of  phenol that has dimerised.[ Kf =5.12K/m]                      (3)

 

16. State and explain the third law of thermodynamics. Give its application.              (3)

 

17. At 300K a certain reaction is 50% complete in 20 minutes. At 350K the same reaction is 50% complete in 5 minutes. Calculate the activation energy for the reaction.                                                                                                                                                       (3)

 

18.     a.) Differentiate between Physiosorption and Chemiosorption.                                   

  b.) write Short notes on

                        1.) Zeolites                                                                              

                        2.) Selectivity of a catalyst                                                                               (3)

 

19. What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention some of its uses                                                                                   (3)

 

20. a.) Draw geometrical and optical isomers of [CoCl2(en)2]+.

        b.) What do you understand by chelating ligand and ambidentate ligand             (3)

 

21 a.) Write the structural formula of Ethyl 3-bromo 2-methyl butanoate

     b.) Bring out the following conversions

            i.) Propanamide to Ethanamine

            ii.) Nitro-benzene to Phenol                                                                                         (3)

 

 

22.) Account for the following:

        i.) Aniline is a weaker base than cyclohexyl amine.

     ii.) Before reacting aniline with HNO3 for nitration it is converted to acetanilide

    iii.) Tertiary amines do not undergo acylation reaction.                                                       (3)

 

23. a.) Why are neutrons best projectiles as compared to protons ? and ? particles?

     b.) How is C-14 produced in nature? Give equations.

                                                                                                                                                            (3)

 

 

24 a.)State the function along with one example each

        i.) Mordant dye

      ii.) Artificial sweetener

 

    b.) Expand BHT and UDMH                                                                                                           (3)

 

25 a.) What if meant by Faraday’s constant? Give its value.

     b.) State reason why rusting of iron is said to be an electro chemical reaction

     c.) Calculate the equillibrium constant K for the reaction at 298K

Zn(s) + Cu2+ (aq)             Zn2+(aq) + Cu(s)      

       

        (EoZn2+/Zn= -0.76V, EoCu2+/Cu= 0.34V)                                                                               (5)

 

OR

 

a.)    How many coloumbs are required for the following reduction.

i.)                  1 mole of Al3+ to Al.

ii.)                1 mole of Cu2+ to Cu.

b.)    The resistivity of a conducting cell containing 0.001M KCl Solution at 298K Is 1500 ohm. What is the cell constant if conductivity of 0.001M KCl solution at 298K is 0.146 x 10-3 Siemen/cm.                                                                                    (5)

 

26.     a.) What is the most stable Oxidation state of Tl ?

            b.) Arrange the following in increasing order of basic character.

                        NH3,PH3,SbH3,AsH3

                c.) Give the preparation of H2SO4 by contact process

   d.) Draw the Structure of XeOF4s

                                                                                                                                                    (5)

OR

1.)    Assign reason for each of the following:

i.)                 Sulphurvapour exhibit some paramagnetic behaviour

ii.)                Of the noble gases only Xenon is known to form  real compounds

iii.)              Inter-halogens are more reactive than halogens

iv.)              HI in aqueous solution is stronger acid than HCl

v.)                CCl4 is not hydrolyzed with water but SiCl4 is easily hydrolyzed

(5)

 

 

 

27. a.) what are essential and non-essential amino acids

      b.) What type of linkages are responsible for formation of

                        i.) Primary structures of proteins

                        ii.) ?-helix formation

iii.)?-Sheet Structure

iv.) Cross linking of poly peptide chains

c.)    Hormones are chemical messengers. Explain                                                            (5)

 

OR

 

a.)How are lipids classified? Give an example of each

b.) Comment briefly on the chemical nature of insulin and its physiological activity

c.) Name the deficiency disease caused due to lack of vitamin B12 and K                       (5)

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