CBSE Class XII Model Paper for 2010 by Amar Ujala - Chemistry

1. Point defect Decreases the density of a crystal? (1)

2. What is the primary structural feature necessary for a molecule to make it useful in a condeusation pdymesisation reaction? (1)

3. What is the number of atoms in a unit cell of FCC crystal? (1)

4. Arrange the following compaunds in an increasing order of basic strength in their aqueaus solutions  (1)
    NH₃ , CH₃NH₂ , (CH3)₂ NH , (CH₃)₃ N

5. Write the IUPAC name of (CH₃)₂ CH-CH₂,-C-CH(CH₃)₂  (1)

6. Why is electrolytic reduction preferred over chemical reduction for the isolation of certain metals? (1)

7. What is the role of depressant in froth floatation process? (1)

8. What is the percentage efficiency of packing in case of a metal crystal for body centred cubic structure? (1)

9. A copper-silver cell is set up. The copper ion concentration in it is 0.10 M the silverion canc. is not known. the cell potential mearured 0.422 V. Determine the conc. of silver ion in the cell, Given E⁰Ag⁺=0.80v, E⁰cu²⁺/cu=+0.34v (2)

10. Describe the role of the following :-  (2)

    (i.) NaCN in the extraction of silver from a silver ore
    (ii.) Cryolite in the extraction of aluninium from pure alumina

11. Differentiate between condensation and addition polymerisation. Give one example each of the resulting polymers. (2)

12. Explain the mechanism of aid dehyhration of ethanol to yield ethene. (2)

13. Draw the structures of (i) Xef₂  (ii)H₃Po₄ (2)

      (i) Rusting of iron in saline water

      (ii) Iron does not rust even if zinc coating is broken

14. Describe the following with on example of each. (2)

      (i) Reimer-Themann Reaction

      (ii) Sandmeyer Reaction

OR

      Describe the follwing reactions with one example of each

      (i) Friedal- Craft reaction

      (ii) Cannizzaro Reaction

15. Complete the following chemical reaction equations (2)

      (i) Xef₂+H₂O

      (ii) PCl₅+H₂O

16. Complete the following chemical reaction equation:- (2)

      (i) MNO₄+ C₂O₄^2-+ H⁺

      (ii) Cr₂O₇^2-+ Fe²⁺+ H⁺

17. Enumerate the reactions and facts of D-glucose which cannot be explained by its open chain structure. (2)

18. A first order reaction has a rate constant of 0.0051 min^-1 If we begin with O.10M Canc. of reactant, What conc. of the reactant will be left after 3 hours. (2)

19. Calculate the cell emf and Drg^o for the following at 25^oc Zn(s)/Zn²⁺(0.1M) 11 Cd²⁺ (0.01M)/ Cd(s) Given E^oZn²⁺/Cd=-0.763 Volt, 1F=96500 C mol^-1, R=8.314 JK^-1 Mol^-1

OR

Calculate the standard electrode potential of Ni²⁺/Ni electrode if emf of the cell Ni(s)/Ni²⁺/Ni²⁺_{(0.01 m)}II Cu²⁺ (0.1M)I Cu(s) is 0.59volt Given E^o Cu²⁺/Cu = +0.34 Volt

20. Explain the following

     (i) Electrophoresis   (ii) Dialysis   (iii) Tyndall effect

21. (i) What is spectro chemical series  1x3=3

     (ii) Show the splitting of degenerate d-crbitals occarding to crystal field theory.

     (iii) How the configuration of d-orbitals is decided on the basis of pairing energy?

22. Explain the following observations :-

     (i) These are two -NH₂ groups in semi carbazide but only one is involved in the formation of semicarbazone

     (ii) Phenols are more acidic than alcohols

     (iii) Alkyl halider when react with alcohlic KOH, forms alkenes.

23. Give reason for the following observation :-

     (i) Of the d4 species, Cr²⁺ is strongly reducing where as Mn (III) is strongly oxidising.

     (ii) The enthalpies of atomization of the transition metals are quite high.

     (iii) Interstitial compounds are well known for transition metals.

24. Compound a C₆H₁₂O₂ on reduction with liA₂H₄ yields two compounds B and C. The compound B On oxidation gave D which on treatment with aqueous alkali and subsequent heating furnished E. The latter on catalytic hydrogenation gave C. The compound D on further oxidation gave CH₃COOH Deduce the structure of A,B,C,D and E.

25. Define the following and give one example of each

     (i) Antihistamine   (ii) Antacids   (iii) Antibiotics

26. Calculate the freezing point of a solution containing 18 g glucose C₆H₁₂O₆ and 68.4 g sucrose C₁₂H₂₂0₁₁ in 200g of water the freezing point of pure water is 273 K and Kf for water is 1.86 K Kg mol^-1

OR

     What conc of nitrogen should be present in a glass of water at room temperature? Assume a temperature of 25^oC, a total pressuse of 1 atm and mole fraction of nitrogen in air of 0.78 (K_H for nitrogen=8.42X10^-7M/mm Hg)

27. The half life for a first order reaction is 5 x 10⁴s. What percentage of the initial reactant will react in 2 hours.  (3)

28. (a) Draw the structure of (i) H₂S₂O₈ (ii) HCLO₄  (2+3)

      (b) How would you account for the following :

           (i) NH₃ is a stronger base than PH₃

           (ii) Sulphur has a greater tendency for catenation than oxygen.

           (iii) F₂ is a stronger oxidising agent than Cl₂

OR

      (b) Arrange the following in the increasing order of property indicated.

           (i) H-F H-Cl H-Br H-I acidic nature.

           (ii) NH₃ PH₃ AsH₃ SbH₃ B1H₅ Basic nature.

           (iii) H₂O H₂S H₂Se H₂Te H₂Po Boiling point.

29. (a) Write the chemical reaction to illustrate the following : (2+3)

      (i) Rosenmund reduction (ii) Aldol condensation.

      (b) Distinguish between the following pairs :

      (i) Propanal and propanone

      (ii) Acetophenone and Benzophenone

      (iii) Phenol and Benzoic acid.

OR

      (a) Convert the following

      (i) Ethanol to 3-hydroxybutanal

      (ii) Benzaldehyde to Benzophenone

      (b) An Organic compound A has the molecular formula C₈H₁₆O₂ It gets hydrolysed with dil sulphuric acid and gives a carboxylic acid B and on alcohol C. C,on oxidation with chromic acid also produced B C on dehydration given but-1end write equation for the reactions involved.

30. (i) Write the preporation of potassium permanganate crystals from its ore. How KMnO₄ act as an oxidising agent in acidic medium

      (ii) What happens when acidic KMNO⁺ reacts with a (a)HI (b) FeSo₄ (c) C₂H₂O₄

OR

      (i) Write the preparation of potassium dichromate is crystals for its are.

      (ii) What happens when potassium dichromate is treated with acid and with base.

      (iii) Draw the structure of chromate and dichromate ion.

      (iv) Write the ionic equation when potassium dichromate reacts with SnCl₂ and with FeCl₂ in acidic medium.

     (a.) What are transition elements? What is the difference between the electronic configurations of transition and inner transition elements?

Courtesy:- Amar Ujala