#### 12th Standard Chemistry Chemical Kinetics English Medium Free Online Test One Mark Questions with Answer Key 2020 - 2021

12th Standard

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Chemistry

Time : 00:20:00 Hrs
Total Marks : 20
20 x 1 = 20
1. 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

2. 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

3. 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

4. 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

5. 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) x 103Jmol-1

6. For a first order reaction, the rate constant is 6.909 min-1.the time taken for 75% conversion in minutes is

(a)

$\left( \cfrac { 3 }{ 2 } \right) { log }^{ 2 }$

(b)

$\left( \cfrac { 2 }{ 3 } \right) log2$

(c)

$\left( \cfrac { 3 }{ 2 } \right) log\left( \cfrac { 3 }{ 4 } \right)$

(d)

$\left( \cfrac { 2 }{ 3 } \right) log\left( \cfrac { 4 }{ 3 } \right)$

7. The rate constant of a reaction is 5.8 x 10-2. The order of the reaction is

(a)

First order

(b)

zero order

(c)

Second order

(d)

Third order

8. The half life period of a radioactive element is 140 days. After 560 days , 1 g of element will be reduced to

(a)

$\left( \cfrac { 1 }{ 2 } \right) g$

(b)

$\left( \cfrac { 1 }{ 4 } \right) g$

(c)

$\left( \cfrac { 1 }{ 8 } \right) g$

(d)

$\left( \cfrac { 1 }{ 16 } \right) g$

9. After 2 hours, a radioactive substance becomes $\left( \cfrac { 1 }{ 16 } \right) ^{ th }$ of original amount Then the half life ( in min) is

(a)

60 minutes

(b)

120 minutes

(c)

30 minutes

(d)

15 minutes

10. What would be the rate of disappearance of oxygen, if the rate of formation of nitric oxide (NO) is 3.6 x 10-3mol 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

11. 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

12. For an exothermic chemical process occurring in 2 steps as
(i) A +B ⟶ X (slow) ;
(ii) X ⟶  AB (fast)
The progress of the reaction can be best described by (x- intermediate).

(a)

(b)

(c)

(d)

None of these

13. Nitric oxide (NO) reacts wtih oxygen to produce nitrogen dioxide
2NO(g) + O2(g) ⟶ 2NO2(g)
If the mechanism of reaction is
NO + O2 $\overset { K }{ \rightleftharpoons }$ NO3 (fast)
NO3 + NO $\overset { { K }_{ 1 } }{ \rightleftharpoons }$ NO2 + NO2 (slow)

(a)

Rate = K' [NO] [O2]

(b)

Rate = K' [NO] [O2]​​​​​​​2

(c)

Rate = K' [NO]2 [O2​​​​​​​]

(d)

Rate = K' [NO]3 [O2]

14. A reaction having equal activation energies for forward and reverse reactions has

(a)

ΔG = 0

(b)

ΔH = 0

(c)

ΔH = ΔG = ΔS = 0

(d)

ΔS = 0

15. 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

16. Which of the above graphs is correct for first order reactions?

(a)

I, II

(b)

II, III

(c)

I, IV

(d)

I, III

17. During decomposition of an activated complex

(a)

energy is always released

(b)

energy is always absorbed

(c)

energy does not change

(d)

products may be formed.

18. Concentration is expressed in?

(a)

$\frac { number\ of\ moles/litre }{ time\ in\ sec }$

(b)

$\frac { time\ in\ sec }{ number\ of\ moles/litre }$

(c)

$\frac { number\ of\ moles/litre }{ volume }$

(d)

$\frac { volume }{ number\ of\ moles/litre }$

19. For the second order reaction ${ t }_{ \frac { 1 }{ 2 } }\alpha$

(a)

$\frac { 1 }{ { a }^{ 2 } }$

(b)

$\frac { 1 }{ { a } }$

(c)

Constant

(d)

a

20. The excess energy which a molecule must possess to become active is known as

(a)

kinetic energy

(b)

threshold energy

(c)

potential energy

(d)

activation energy