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Chemical Kinetics Model Question Paper 1

12th Standard EM

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50
5 x 1 = 5
1. For the reaction, 2NH3 ⟶ N2 + 3H2, if $\frac { -d[NH_{ 3 }] }{ dt }$=k1[NH3], $\frac { d[N_{ 2 }] }{ dt } =k_{ 2 }[NH_{ 3 }],\frac { d[{ H }_{ 2 }] }{ dt }$=k3[NH3] then the relation between k1, k2 and k3 is

(a)

k1=k2=k3

(b)

k1=3k2=2k3

(c)

1.5k1=3k2=k3

(d)

2k1=k2=3k3

2. For a reaction Rate = kacetone[]32 then unit of rate constant and rate of reaction respectively is

(a)

(mol L-1 S-1),(mol1/2L1/2S-1)

(b)

(mol-1/2L1/2s-1),(mol L-1s-1)

(c)

(mol1/2L1/2s-1),(molL-1s-1)

(d)

(molLs-1),(mol1/2L1/2s)

3. 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

4. For the reaction, 2N2O5 ⟶4 NO2+O2, select the correct statement.

(a)

Rate of formation of O2 is same as rate of formation of NO2

(b)

Rate of disappearance of N2O5 is two times the rate of formation of NO2.

(c)

Rate of formation of O2 is 0.5 times rate of disappearance of N2O5

(d)

Rate of formation of NO2 is equal to rate of disappearance of N2O5

5. The depletion of ozone involves the following steps:
Step 1: O2 +O $\overset { { k }_{ 1 } }{ \underset { { k }_{ 2 } }{ \rightleftharpoons } }$ O3 (fast)
Step 2: O3 +O $\overset { k }{ \longrightarrow }$ 2O2 (slow)
The predicted order of the reaction will be

(a)

I

(b)

II

(c)

III

(d)

Zero

6. 5 x 2 = 10
7. Describe the graphical representation of first order reaction.

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

9. 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.

10. The reaction A + 2B ⟶ C obeys the rate equation. Rate = $K{ \left[ A \right] }^{ \frac { 1 }{ 2 } }{ \left[ B \right] }^{ \frac { 3 }{ 2 } }$ What is the order of the reaction?

11. 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

12. 5 x 3 = 15
13. For a reaction x+y+z$\longrightarrow$ productsthe rate law is given by ratek =k[x]3/2[y]1/2 what is the overall order of the reaction and what is the order of the reaction with respect to z.

14. Explain briefly the collision theory of bimolecular reactions

15. A first order reaction is found to have a rate A constant k = 7.39 x 10-5 S-1. Find the half life of this reaction.

16. What is the effect of temperature on the rate constant of a reaction? How can this temperature effect on rate constant be represented quantitatively?

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

18. 4 x 5 = 20
19. 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?

20. The activation energy of a reaction is 225 k Cal mol-1 and the value of rate constant at 40°C is 11.8X10-6s-1Calculate the frequency factor, A.

21. 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?

22. The decomposition of NH3 on platinum surface is zero reaction. What are the rate of production of N2 and H2 it K = 2.5 X 10-4mol L-1 S-1?