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#### Chemical Kinetics Model Questions

12th Standard EM

Reg.No. :
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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50
10 x 1 = 10
1. For a first order reaction A ⟶ B the rate constant is x min−1. If the initial concentration of A is 0.01M , the concentration of A after one hour is given by the expression.

(a)

001. e−x

(b)

1 x 10-2(1-e-60x)

(c)

(1x10-2)e-60x

(d)

none of these

2. A zero order reaction X ⟶ XProduct, with an initial concentration 0.02M has a half life of 10 min. if one starts with concentration 0.04M, then the half life is

(a)

10 s

(b)

5 min

(c)

20 min

(d)

cannot be predicted using the given information

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. 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

5. In a first order reaction $x\longrightarrow y$ if k is the rate constant and the initial concentration of the reactant x is 0.1M, then, the half life is

(a)

$\left( \cfrac { log2 }{ k } \right)$

(b)

$\left( \cfrac { 0.693 }{ (0.1)k } \right)$

(c)

$\left( \cfrac { In2 }{ k } \right)$

(d)

none of these

6. 2N2O5 ⟶ NO2 + O2$\frac { d\left[ { N }_{ 2 }{ O }_{ 5 } \right] }{ dt }$ = k1[N2O5], $\frac { d\left[ { NO }_{ 2 } \right] }{ dt }$k2[N2O5] and $\frac { d{ O }_{ 2 } }{ dt }$ = k 3[N2O5], the relation between k1, k2 and k3 is

(a)

2k1 = 4k2 = k3

(b)

k1 = k= k3

(c)

2k1 = k2 = 4k3

(d)

2k1 = k2 = k3

7. What would be the rate of disappearance of oxygen, if the rate of formation of nitric oxide (NO) is 3.6 xl0-3mol L-1 s-1?

(a)

4 x10-3mol L-1s-1

(b)

4 x10-3mol-1 L-1s-1

(c)

4.5 x 10-3mol L-1s-1

(d)

4.5 x 10-3mol-1 L-1s-1

8. 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

9. In pseudo-order reactions

(a)

The actual order of reaction is different from that expected using rate law expression

(b)

The concentration of at least one reactant is taken in large excess.

(c)

The concentration of reactant taken in excess may be taken as constant

(d)

All of these

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

(a)

First order

(b)

second order

(c)

Third order

(d)

zero order

11. 5 x 1 = 5
12. k1

13. (1)

$\frac { 0.693 }{ { k }_{ 1 } } sec$

14. t1/2

15. (2)

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

16. n = 2

17. (3)

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

18. Arrhenius

19. (4)

II Order

20. N2O5(g) ⟶2NO2(g) + $\frac { 1 }{ 2 }$ O2(g)

21. (5)

1

5 x 2 = 10
22. Define average rate and instantaneous rate

23. Define rate law and rate constant

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

25. For a reaction A + B ⟶ C, the rate of the reaction is denoted $\frac { -dA }{ dt }$ or $\frac { -dB }{ dt }$ or $\frac { +dC }{ dt }$. State the significance of plus and minus sign.

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

27. 5 x 3 = 15
28. Explain briefly the collision theory of bimolecular reactions

29. The decomposition of Cl2O7 at 500K in the gas phase to Cl2 and O2 is a first order reaction. After 1 minute at 500K, the pressure of Cl2O7 falls from 0.08 to 0.04 atm. Calculate the rate constant in s-1

30. Give examples for first order reaction.

31. Give the characteristics of first order reaction.

32. 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 ⟶ ∞?

33. 2 x 5 = 10
34. A zero order reaction is 20% complete in 20 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?

35. State the characteristics of order of reactions. (OR) Give the characteristics of order of reactions.