CBSE Sample Paper Class XII, Chemistry 2006



Chemistry – CLASS XII


TIME : 3 Hrs.                                                                     Max.Marks : 70

General Instructions:-

I    All questions are compulsory.

II  Marks for each question are indicated against it.

III Question numbers 1 to 5 are very short- answer questions each of 1 mark. Answer    

     them in one word, phrase or about one sentence each.

IV Question number 6 to 12 are short answer questions of 2 marks each. Answer them in  

     about 30 words each.

V  Question number 13 to 24 are short answer questions of 3 marks each. Answer 

     them in about 40 words each.

VI Question numbers 25 and 27 are long answer questions of 5 marks each. Answer them

    in about 70 words.

VII Use log table, if necessary.

1.  Write the structure of the basic unit of cyclic silicate.


2.  At what temperature is the  entropy of a perfectly crystalline substance  taken as  zero?  


3.  Whichcompound is used as developer in photography ? 


4.  Which is the simplest  optically active amino acid .


5. Define denaturation and reaturation in terms of protein ?   


6. I. Identify X in the following chemical reaction:   NaClO3 + X2              NaXO3 + Cl2.

    II. Arrange the following in the decreasing order of their acidity – 

          HClO, HIO HBrO,     


7 How will you convert:-

     (i) ethanal to  propan-2 ol                                                                        

     (ii) Benzene to Benzoic acid 



8.  (a) Draw the structures of XeOF4 and H2SO5.                                                     

       (b) Oxides of Nitrogen are open chain type while oxide of Phosphorous are caged .why? 


9. Draw  all possible optical isomers of a  for 2,3 dichloro butane.


10. .(a) What are the factors which affect Crystal Field Splitting Energy(CFSE)?

    (b) Write the hydrate  isomer of the comolex: [Cr (en)2 (CN)(H2O)2]Cl .  and name it in IUPAC system.


11. Comment on following :                                                                                        

    (i) Sandmeyer reaction         

   (ii) Reimer Tiemann reaction  


(i) Ortho -nitrophenol is steam volatile while  p-nitrophenols is not steam volatile ?explain the reason.         

(ii) Why does aldehydes can give +fehling ,tollen test while ketone does not ?

12.  (a) Predict the sign of ? H and ?S for the following reaction.

    2 Br(g) ?   Br2(g).


     (b) Some of the exothermic reactions are non spontaneous ,why?   


13. (a) Primary amine is not prepared by ammonolysis of alkyl halide preferably.why?

      (b) What are the products of  reaction of HI with Anisol ? 

       ©. Why does ether has net dipole moment even it is symmetric ether?         

14.(a) What do you mean by chelation effect..

    (b) Which bonds are responsible to stabilise secondary structure of protein?              

     (c) Rate constant of a reaction was found to be 2 x 10-2 mol-1 L s-1.predict the order?

15.  (a) Anilne is more reactive towards electrophilic substitution reaction  . Explain. 

       (b) Aniline on nitration gives m-nitro also aniline ,though amono group is o,p director .why?                     

       (c)  Write the mechanism of cannizaro reaction.


16. (a)Name the alkyl halide and sodium alkoxide used to synthesise tert butylethylether.

     (b) What happens when acidified potassium dichromate react with KI. 

     (c) Why does HCl is not used in place of Sulphuric acid while titratining Pot.Permagnate against  

          Ammonium Ferrous Sulphate.


     (c) What is PHBV?.             


17. (a) The composition of a sample of wustite is Fe0.93 O1.00.What percentage of the iron   is present in the  

             form of Fe (III)? (Atomic mass: Fe=56)


     (b) What are Pyrroelectric  substance ? give example


18. (a) What are CFRC and CFRP?

      (b) “An unknown fibre ‘A’ is stronger than steel, stiffer than titanium and lighter than aluminium”.What  

             could the fibre ‘A’ be?

      (c) what is composition of Dettol?          


19  (a) Draw plot for Langmuir  adsorption isotherm ?

   (b) What is the cause of tydall effect?

   (c) Define a). Micromolecular colloid      b). Macromolecular colloid     

20.(a) Why does Zr and Hf shows same properties ?

   (b) What is the equivalent weight KMnO4  in acidic medium?

   (c) Why does only  F and O  form compounds with inert gas Xe ?                                                            


21. (a) How LiAlH4 is prepared? Write the reaction involved.

     (b). In which point defect the density of an ionic crystal decrease?

     (c) Why does molality is preferred over molarity to express the concentration of a solution?   


22.. (a)Sterene undergo in anionic polymerization to form Buna-S.Why?

      (b)  Explain the term a.reverse transcription  b. Translation ?


23. What mass of non-volatile solute,urea(Mol.mass=60)needs to be dissolved in 100g  of water to decrease 

      the vapour pressure of water by 25%.What will be the  molality of the solution?


24. .(a) Half life period of a radioactive metarial is 2500 years,if the rate of disintegration at  certain moment 

      is  12dps ,find out the number of molecule present in substance at that moment.

25. (a) An electron beam emerges from an accelerator with kinetic energy of 100eV.What    

             is its de Broglie wavelength?(h=6.6×10-24Js,m=9.1×10-31Kg,1eV=1.6×10-19J).



 (b) Why Mg is excellent conductor ,explain in terms of band theory.


26. (a) Write reaction involved  at cathode and anode of fuel cell.                            


      (b) Calculate charge required in coloumb-

 i. To deposite 40 gm of Al from Al2O3.

 ii. To convert 1 mol of MnO4 to Mn+2.

      c. Write the unit of molar conductivity.



27. (a) The rate of decomposition of H2O2  was measured at by it’s titration against KMnO4. solution  

          following results were obtained.

Time (Sec)                                0                     10                    20

Conc of H2O2.                       22.8                 13.8                 8.3

 Show that the reaction is of first order.

           (b) Define the activation energy of a reaction how it is affected by catalyst

           (c) What do you mean by pseudo first order reaction ?

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