**LEVEL – I **

11. If a reaction with t_{1/2} = 69.3 sec , has a rate constant 10^{–2} sec^{–1} , the order is

(A) 0

(B) 1

(C) 2

(D) 3

12. The specific rate constant for a first order reaction is 60 × 10^{–4} sec^{–1}. If the initial concentration of the reactant is 0.01 mol L^{—1} , the rate is

(A) 60 × 10<sup–6< sup=”” m=”” sec<sup=””>—1

(B) 36 × 10<sup–4< sup=”” m=”” sec<sup=””>—1

(C) 60 × 10<sup–2< sup=”” m=”” sec<sup=””>—1

(D) 36 × 10<sup–1< sup=”” m=”” sec<sup=””>—1

13. The rate constant for a zero order reaction is 2 × 10^{–2} mol L^{–1} sec^{–1}. If the concentration of the reactant after 25 sec is 0.5 M , the initial concentration must have been

(A) 0.5 M

(B) 1.25 M

(C) 12.5 M

(D) 1.0 M

14. A first order reaction is carried out with an initial concentration of 10 ML^{–1} and 80% of the reactant changes into the product. Now if the same reaction is carried out with an initial concentration of 5 ML^{–1}, the percentage of reactant changing to the product is

(A) 40

(B) 80

(C) 160

(D) can’t be calculated

15. What fraction of a reactant showing first order remains after 40 min , if t_{1/2} is 20 min ?

(A) 1/4

(B) 1/2

(C) 1/8

(D) 1/6

16. A substance undergoes a first order decomposition. The decomposition follows two parallel first order reaction as

The percentage distribution of B and C are

(A) 80% B and 20% C

(B) 75% B and 25% C

(C) 90% B and 10% C

(D) 60% B and 40% C

17. A tangent drawn on the curve obtained by plotting concentration of product (mole L^{–1}) of a first order reaction vs. time (min) at the point corresponding to time 20 minute makes an angle to 30° with concentration axis. Hence the rate of formations of product after 20 minutes will be

(A) 0.580 mole L^{–1} min^{–1}

(B) 1.723 mole L^{–1} mi^{–1}–1

(C) 0.290 mole L^{–1} min^{–1}

(D) 0.866 mole L^{–1} min^{–1}

18. For reaction 3A −> products, it is found that the rate of reaction increases 4 – fold when concentration of A is increased 16 times keeping the temperature constant. The order of reaction is ?

(A) 2

(B) 1

(C) 1

(D) 0.5

19. The thermal decomposition of acetaldehyde : CH3CHO −> CH4 + CO , has rate constant

of 1.8 × 10^{–3} mole^{–1/2} L^{1/2} min^{–1} at a given temperature.

How would will change if concentration of acetaldehyde is doubled keeping the temperature constant ?

(A) will increase by 2.828 times

(B) will increase by 11.313 times

(C) will not change

(D) will increase by 4 times

20. The reaction ; 2O_{3} −> 3O_{2} , is assigned the following mechanism.

(I) O_{3} <−> O_{3} + O

(II) O_{3} + O −>(slow) 2O_{2}

The rate law of if the reaction will, therefore be

(A) r ∝ [O_{3}]^{2}[O_{2}]

(B) r ∝ [O_{3}]^{2} [O_{2}]^{–1}

(C) r ∝ [O_{3}]

(D) r ∝ [O_{3}] [O_{2}]^{–2}

__ANSWER:__

**11. B 12. A 13. A 14. B 15. D 16. B 17. B 18. D 19. A 20. D **