preparatory exam-23/11/19

12th Standard EM

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Chemistry

SECTION-A

Time : 01:15:00 Hrs
Total Marks : 50

    I.Choose the correct answer:

    5 x 1 = 5
  1. Which of the following is incorrect for physisorption?

    (a)

    reversible

    (b)

    increases with increase in temperature

    (c)

    low heat of adsorption

    (d)

    increases with increase in surface area

  2. Hair cream is

    (a)

    gel

    (b)

    emulsion

    (c)

    solid sol

    (d)

    sol.

  3. The phenomenon observed when a beam of light is passed through a colloidal solution is

    (a)

    Cataphoresis

    (b)

    Electrophoresis

    (c)

    Coagulation

    (d)

    Tyndall effect

  4. Collodion is a 4% solution of which one of the following compounds in alcohol – ether mixture?

    (a)

    Nitroglycerine

    (b)

    Cellulose acetate

    (c)

    Glycoldinitrate

    (d)

    Nitrocellulose

  5. If x is the amount of adsorb ate and m is the amount of adsorbent, which of the following relations is not related to adsorption process?

    (a)

    x/m=f(P) at constant T

    (b)

    x/m=f(T) at constant P

    (c)

    P = f(T) at constant x/m

    (d)

    x/m = PT

  6. II.Answer the following questions in short:

    6 x 2 = 12
  7. Give two important characteristics of physiscorption

  8. Differentiate physisorption and chemisorption

  9. Which will be adsorbed more readily on the surface of charcoal and why; NH3 or CO2?

  10. Heat of adsorption is greater for chemisorptions than physisorption. Why?

  11. Thermal decomposition of KClO in presence of MnO2 proceeds as follows.
    Steps in the reaction 2KClO → 2KCl+3Ocan be given as

  12. Formation of water due to the reaction of H2 and O2 in the presence of Cu can be given as

  13. III.Answer the following questions:

    6 x 3 = 18
  14. What happens when a colloidal sol of Fe(OH)3 and AS2O3 are mixed?

  15. What is the difference between a sol and a gel?

  16. Why are lyophillic colloidal sols are more stable than lyophobilc colloidal sol.

  17. Addition of Alum purifies water. Why?

  18. What are enzymes? Write a brief note on the mechanism of enzyme catalysis.

  19. Describe some feature of catalysis by Zeolites.

  20. IV.Answer the following questions in detail:

    3 x 5 = 15
  21. Explain any one method for coagulation

  22. Explain intermediate compound formation theory of catalysis with an example

  23. Describe adsorption theory of catalysis

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