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Chemistry sample CBSE Exam paper
Posted by Admin on 15-03-2014 at 3:37 pm Under Chemistry Cafe

                                               CHEMISTRY

                                                      

                                                 CLASS – XII

 

Time : Three Hours                                                                             Max. Marks : 70

 

General Instructions

1. All questions are compulsory.

2. Question nos. 1 to 8 are very short answer questions and carry 1 mark each.

3. Question nos. 9 to 18 are short answer questions and carry 2 marks each.

4. Question nos. 19 to 27 are also short answer questions and carry 3 marks each

5. Question nos. 28 to 30 are long answer questions and carry 5 marks each

6. Use log tables if necessary, use of calculators is not allowed.

1. Give preparation reaction for Terylene.                                                                                                               1

2. What is chemical adsorption?                                                                                                                                1

3.Write the IUPAC name of [Pt(NH3)2Cl(NO2)]                                                                                                         1

4.Write  an example of analgesic  and antipyretic drug .                                                                                      1

5. Out of maltose and sucrose, which is reducing sugar?                                                                                      1

6. What are ambident  nucleophiles ?                                                                                                                      1

7. What happen when benzaldehyde react with aniline in acidic medium?                                                      1

8.Give an example of Hoffman bromamide reaction?                                                                                           1

9. Silver forms ccp lattice and x ray studies of its crystals show that the edge length of its unit cell is 408.6 pm. Calculate the density of silver.(Atomic mass of silver =107.9 u )                                                      2

10.Explain the following:                                                                                                                                               1.F –centre

 2.A hole

11.Explain the chemistry of lead storage battery  while charging .                                                                     2

12.How is disproportionation  takes place in chemical  reactions? Write a chemical reaction to show

  disproportionation.                                                                                                                                                    2

13.Explain the formation of Bakelite .                                                                                                                       2

14.Give the reasons for

    1.Haloalkanes though polar ,are insoluble in water

    2.Grignard reagents should be prepared under anhydrous conditions.                                                         2

15.Describe the functions of antibiotics or  antimicrobials. Give an example.                                                  2

16.Using valency bond theory predict the shape and magnetic behavior  of [Co(NH3)6]3+ion.                       2

17.How will you distinguish between the following chemically:

     1. Chloroethaneane  and  Bromoethane         

     2. Chlorobenzene and  Chlorocyclohexane                                                                                                         2

18. State Henry‘s law and mention its two important applications .                                                                  2                                 

                                                           OR

Calculate the freezing point of a solution containing 18 g of C6H12O6 ,and 68.4 g of C12H22O11 ,in 200 g water. The freezing point of pure water is00C and Cryoscopic Constant of water is 1.86 K/m.                                                               

19. Complete the following :

1. CH3CH2 CH2NH2 +HCl  ------------    

2. C6H5N2Cl  +H3PO2+H2O -------------  

3. C6H5N2Cl  +   C2H5 OH-----------------                                                                                                                         3

20. 1.Write the IUPAC name of  OHCH2CH =CHCH2OH   

      2.Explain the mechanism of hydration of ethene .                                                                                           3

 21. 1.What is nucleoside ?

       2. What are water  soluble vitamins?

       3. Give deficiency diseases of vitamin C and D.                                                                                                3

22. Complete and balance the following equations :

       1. F2+H2O(cold) ------------

       2. BrO3- +F2+OH----------------

       3. Ca3P2+ H2O---------------

                                                                                          OR

       1. PCl5 +H2O-------------

       2. KMNO4 +HCl-------------

       3. S +HNO3----------------                                                                                                                                         3

23. Explain

1. Freundlich adsorption isotherm .

2. shape selective catalysts?Give an example of such catalyst .                                                                          3

24. Calculate the emf of the following cell at 298 K:

    Cu(s)I Cu2+(0.130M) II Ag+(1.00x10-4M) IAg(s)

    Given E0   Cu2+ /Cu =+0.34 V and E0   Ag+ /Ag =+0.80 V.                                                                                        3

25. Explain the role of

1. Cryolite in the electrolytic reduction of alumina

2. CO  in the purification of nickel

3. Zinc in recovery of silver.                                                                                                                                        3

26. Calculate the depression in freezing point of water when 20.0 g of CH3CH2CHClCOOH is added to 500 g of water.( given Ka=1.4X10-3,Kf=1.86 Kkg/mol                                                                                                     3

27.What is meant by lanthenoid contraction ? Discuss the important consequences of lanthenoid contraction.                                                                                                                                                                  3                                                                                                                               

28. a.Convert the followings

          1. Benzene to Benzoic acid

          2.benzoic acid to benzamide

       b.Describe the following with suitable chemical reactions:

        1. Aldol condensation

        2. Cannizzaro reaction                                                                                                                                          5

       c. Write the IUPAC name of  C6H5CH2COCH3

                                                                        Or

    a.    1.Benzaldehyde to benzophenone

           2.Ethanol to propanone

    b.    Describe the following with suitable chemical reactions:

                  1.Stephen reduction

                  2.Gattermann Koch  reaction.

     c. Write the IUPAC name of  CH3CHCH3CH2C(CH3)2COCH3  .

29. a.Complete  and balance the following chemical equations:

 1. Br2 +F2 ------------------

2.U + ClF3 ------------------

3.XeF6+ H2O-----------------

b.Write the reaction for thermal decomposition of sodium azide.

c.Why does PCl3 fume in moisture?                                                                                                                           5

                                                                       OR

Give the answer of the following:

      1.Draw the structure of XeF4.

      2.Do all bonds in PCl5 alike ?

      3.Why ammonia is a stronger base than phosphine?

      4.White phosphorous is more reactive than red phosphorus.Why?

      5. Thermal stability of water is much higher than that of H2S.Why?                                                                                                

30. a.How can  temperature effect on rate constant be represented quantitatively?

b. The rate constant for a first order reaction is 60/sec.How much time will it take to reduce the initial concentration of the reactant to its 1/16th value?                       

                                                                        OR

a.Define order of reation .Derive integrated rate law for 0 order reaction.

b.A first order reaction takes 40 min for 30% decomposition.Calculate t1/2 for  first order reaction.

 
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