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12th Standard Chemistry English Medium Chemical Kinetics Reduced Syllabus Important Questions With Answer Key 2021

12th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 100

      Multiple Choice Questions


    15 x 1 = 15
  1. The addition of a catalyst during a chemical reaction alters which of the following quantities? (NEET)

    (a)

    Enthalpy

    (b)

    Activation energy

    (c)

    Entropy

    (d)

    Internal energy

  2. What would be the activation energy of a reaction when the temperature is increased from 27oC to 37oC?

    (a)

    534 kJ mol-1

    (b)

    53.4 kJ mol-1

    (c)

    5.34 kJ mol-1

    (d)

    None of these

  3. Which of the following statement is not correct?

    (a)

    Molecularity of a reaction cannot be fractional

    (b)

    Molecularity of a reaction cannot be more than three

    (c)

    Molecularity of a reaction can be zero

    (d)

    Molecularity is assigned for each elementary step of mechanism.

  4. The given reaction
    2 FeCl3 + SnCl2 ⟶ 2FeCl2 + SnCl4 is an example of

    (a)

    I order

    (b)

    II order

    (c)

    III order

    (d)

    None of these

  5. Activation energy of a chemical reaction can be determined by

    (a)

    Evaluating rate constants at two different temperatures

    (b)

    Evaluating velocities of reaction at two different temperatures

    (c)

    Evaluating rate constant at standard temperature

    (d)

    Changing concentration of reactants

  6. How much time will be taken for 20 gm to reduce 5 g? [R = 2 x 10-3s-1 (I order reaction)]

    (a)

    693.1 s

    (b)

    693.1 s-1

    (c)

    6.931 s

    (d)

    6.931 s-1


  7. Which of the above graphs is correct for zero order reactions?

    (a)

    I, II

    (b)

    I, III

    (c)

    I, IV

    (d)

    II, III

  8. For the second order reaction \({ t }_{ \frac { 1 }{ 2 } }\alpha \)

    (a)

    \(\frac { 1 }{ { a }^{ 2 } } \)

    (b)

    \(\frac { 1 }{ { a } } \)

    (c)

    Constant

    (d)

    a

  9. Which one of the following is an example of pseudo first order reaction?

    (a)

    Acid hydrolysis of ester

    (b)

    Decomposition of HI

    (c)

    Synthesis of NH3

    (d)

    All radioactive transformations

  10. In any unimolecular reaction _______________

    (a)

    Only two reacting species is involved in the rate determining step.

    (b)

    The order and the molecularity of slowest step are equal to one.

    (c)

    The molecularity of the reaction is one and order is zero.

    (d)

    Both molecularity and order of the reaction are one.

  11. Rate law cannot be determined from balanced chemical equation if _____________

    (a)

    Reverse reactions is not involved

    (b)

    It is an elementary reaction

    (c)

    It is a sequence of elementary reactions

    (d)

    All of the reactants is in excess. Rate law can be determined from balanced chemical equation if it is an elementary reaction.

  12. CH3COOCH3 + H2 OH \(\overset { { H }^{ + } }{ \longrightarrow } \) CH3 COOH + CH3 OH is an example of ____________ order reaction.

    (a)

    first

    (b)

    zero

    (c)

    third

    (d)

    pseudo

  13. The magnitude of order of a reaction may be _____________

    (a)

    fractional

    (b)

    zero

    (c)

    integral values

    (d)

    all of these

  14. For a general reaction aA + bB ⟶Products, the rate of the reaction is equal to_____________.

    (a)

    k[A]p [B]q

    (b)

    k [A] [B]

    (c)

    k

    (d)

    \(\frac { 1 }{ k } \)

  15. The time required for 50%completion of the reaction is known as ___________

    (a)

    Average life period

    (b)

    Half-life period

    (c)

    Rate

    (d)

    None of these

    1. 2 Marks


    10 x 2 = 20
  16. Define half life of a reaction. Show that for a first order reaction half life is independent of initial concentration

  17. Describe the graphical representation of first order reaction.

  18. Write the rate law for the following reactions.
    (a) A reaction that is 3/2 order in x and zero order in y.
    (b) A reaction that is second order in NO and first order in Br2.

  19. Rate of chemical reaction is not uniform throughout. Justify you answer:

  20. Why is instantaneous rate preferred over average rate?

  21. The decomposition reaction of ammonia gas on platinum surface has a rate constant R = 2.5 x 10-4mol L-1. What is the order of the reaction.

  22. A first order reaction has a specific reaction rate of 10-3 S-1. How much time will it take for 10gm of the reactant to reduce to 2.5 gm?

  23. If the rate of a reaction gets doubled as the temperature is increased from 27oC to 37oC. Find the activation energy of reaction?

  24. Mention the factors that affected the rate of a chemical reaction.

  25. Consider the oxidation of nitric oxide to form NO2
    2NO(g) + O2(g) ➝2NO (g)
    (a). Express the rate of the reaction in terms of changes in the concentration of NO,O2 and NO2.
    (b). At a particular instant, when [O2] is decreasing at 0.2 mol L−1s−1 at what rate is [NO2] increasing at that instant?

    1. 3 Marks


    10 x 3 = 30
  26. The rate of formation of a dimer in a second order reaction is 7.5 X 10-3mol L-1 s-1 monomer concentration. Calculate the rate constant.

  27. Write Arrhenius equation and explains the terms involved

  28. For the reaction \(2x+y\longrightarrow L\)find the rate law from the following data. 

    [x]
    (min)
    [y]
    (min)
    rate
    (Ms-1)
    0.2 0.02 0.15
    0.4 0.02 0.30
    0.4 0.08 1.20
    0.4 0.08 1.20
  29. A reaction is of second order in A and first order in B.
    (i) Write the differential rate equation. 
    (ii) How is the rate affected on increasing the concentration of A three times?
    (iii) How is the rate affected when the concentration of both A and B is doubled?

  30. Give the characteristics of first order reaction.

  31. The rate constant, the activation energy and frequency factor of a chemical reaction at 25oC are 3.0 x 10-4 S-1; 104.4 kJ mol-1  and 6.0 x 1014 S-1 respectively. What is the value of the rate constant when T ⟶ ∞?

  32. The rate constant k for the first order gas phase decomposition of ethyl iodide, C2H5I ⟶ C2H4 +HI is 1.60 x 10-5 s-1 at 600k and 6.36 x 10-3 s-1 at 700K. Calculate the energy of activation for this reaction.

  33. The decomposition of NH3 on platinum surface is zero order reaction what are the rates of production of N2 and H2 if k = 2.5 x10-4 mol+ L S-1.

  34. A reaction is first order in A and second order in B.
    (i) Write the differential rate equation.
    (ii) How is rate affected on increasing the concentration of B three times?
    (iii) How is the rate affected when the concentrations of both A and Bare doubled?

  35. Write the differences between rate and rate constant of a reaction.

    1. 5 Marks


    7 x 5 = 35
  36. How do nature of the reactant influence rate of reaction.

  37. The time for half change in a first order decomposition of a substance A is 60 seconds. Calculate the rate constant. How much of A will be left after 180 seconds?

  38. A first order reaction is 40% complete in 50 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?

  39. Write an account of the Arrhenius equation for rates of chemical reactions. 

  40. A first order reaction laws on rate constant 1.15 x 10-3 S-1. How long will 5 g of this reactant take to reduce to 3g?

  41. The specific reaction. rates of a chemical reaction are 2.45 x 10-5 sec-1 at 273 K and 16.2 x10-4 sec-1 at 303 K. Calculate the activation energy.

  42. The initial rate of a first order reaction is 5.2 x 10-6 mol lit-1 S-1 at 298 K. When the initial concentration of reactant is 2.6 x 10-3 mol.lit-1, calculate the first order rate constant of the reaction at the same temperature.

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