#### Chemical Kinetics Model Question Paper

12th Standard EM

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Chemistry

Time : 01:30:00 Hrs
Total Marks : 50
9 x 1 = 9
1. For a first order reaction A ⟶ product with initial concentration x mol L-1, has a half life period of 2.5 hours. For the same reaction with initial concentration $\left( \frac { x }{ 2 } \right)$ mol L-1 the half life is

(a)

(2.5 x 2) hours

(b)

$\left( \frac { 2.5 }{ 2 } \right)$hours

(c)

2.5 hours

(d)

Without knowing the rate constant, t1/2 cannot be determined from the given data

2. The decomposition of phosphine (PH3) on tungsten at low pressure is a first order reaction. It is because the (NEET)

(a)

rate is proportional to the surface coverage

(b)

rate is inversely proportional to the surface coverage

(c)

rate is independent of the surface coverage

(d)

rate of decomposition is slow

3. 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

4. In a reversible reaction, the enthalpy change and the activation energy in the forward direction are respectively −x kJ mol-4 and kJ mol-1 Therefore , the energy of activation in the backward direction is

(a)

(y-x)kJ mol-1

(b)

(x+y)J mol-1

(c)

(x-y)KJ mol-1

(d)

(x+y)X103Jmol-1

5. What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200K to 400K? (R = 8.314 JK-1mol-1)

(a)

234.65 kJ mol-1 K-1

(b)

434.65 kJ mol-1 K-1

(c)

434.65 J mol-1 K-1

(d)

334.65 J mol-1 K-1

6. The rate constant of a reaction is 5.8X10-2. The order of the reaction is

(a)

First order

(b)

zero order

(c)

Second order

(d)

Third order

7. For a reaction, 2A + B ⟶ 3C, The rate of appearance of C at time 't' is 1.2 x 10-4 mol L-1s-1. Identify the rate of reaction.

(a)

4 x10-5mol L-1s-1

(b)

4.5 x 10-1mol L-1s-1

(c)

3.6 x 10-4 mol L-1s-1

(d)

None of these

8. 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

9. The Unit of rate constant and rate of reaction are same for

(a)

First order

(b)

second order

(c)

Third order

(d)

zero order

10. 5 x 1 = 5
11. k1

12. (1)

$k={ Ae }^{ -\left( \frac { Ea }{ RT } \right) }$

13. n = 2

14. (2)

$\frac { 2.303 }{ t } \log { \frac { a }{ a-x } }$

15. Arrhenius

16. (3)

cannot be fraction or zero

17. 2HI ⟶ H2I2

18. (4)

2

19. Molecularity

20. (5)

II Order

2 x 1 = 2
21. Which one of the following statements regarding order is correct?
a) Order should be determined only by experiment.
b) Order of complex reaction are less than 3.
c) Order can be determined from Stoichiometric equation.
d) Order must be a whole number.

()

a) Order should be determined only by experiment.

22. Two reactions A ⟶ Band C ⟶ D has the energy of activation 40 kJ and 60 kJ respectively. Which of the following statement is correct?
a) Comparison of rate cannot be determined
b) The reaction A ⟶ B proceeds at a faster rate compared to the reaction C ⟶ D
c) The reaction A ⟶ B proceeds at a slower rate compared to the reaction C ⟶ D.
d) Comparison of rate cannot be determined.

()

b) The reaction A ⟶ B proceeds at a faster rate compared to the reaction C ⟶ D

23. 6 x 2 = 12
24. Define average rate and instantaneous rate

25. Derive integrated rate law for a zero order reaction A$\longrightarrow$ product

26. Explain the rate determining step with an example.

27. Explain the effect of catalyst on reaction rate with an example

28. 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?

29. The rate of the reaction X+2y⇾ product is 4x10-3 mol L-1S-1, if [X]=[Y]=0.2M and rate constant at 400K is 2x10-2s-1, What is the overall order of the reaction

30. 4 x 3 = 12
31. Explain briefly the collision theory of bimolecular reactions

32. Explain pseudo first order reaction with an example

33. (i) A first order reaction takes 8 hours for 90% completion. Calculate the time required for 80% completion. (log 5 = 0.6989 ; log10 = 1)

34. Show that in case of first order reaction, the time required for 99.9% completion is nearly ten times the time required for half completion of the reaction.

35. 2 x 5 = 10
36. 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?

37. From the following data, show that the decomposition of hydrogen peroxide is a reaction of the first order:

 t(min) 0 10 20 V(ml) 46.1 29.8 19.3

Where t is the time in minutes and V is the volume of standard KMnO4 solution required for titrating the same volume of the reaction mixture.