Topic: Unit VII: Chemical Kinetics (Test 2)



Topic: Unit VII: Chemical Kinetics
Q.1
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 mol1K1
B. 434.65 kJ mol1K1
C. 434.65 J mol1K1
D. 334.65 J mol1K1
Answer : Option C
Explaination / Solution:

T1 = 200K ; k = k1

T2 = 400K ; k = k2 = 2k1



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Q.2
 This reaction follows first order kinetics. The rate constant at particular temperature is 2.303 × 102 hour1 . The initial concentration of cyclopropane is 0.25M.  What will be the concentration of cyclopropane after 1806 minutes? (log 2 = 0.3010)
A. 0.125M
B. 0.215M
C. 0.25 × 2.303M
D. 0.05M
Answer : Option B
Explaination / Solution:



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Q.3
For a first order reaction, the rate constant is 6.909 min-1.the time taken for 75% conversion in minutes is
A.
B.
C.
D.
Answer : Option B
Explaination / Solution:




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Q.4
In a first order reaction x → y ; if k is the rate constant and the initial concentration of the reactant x is 0.1M, then, the half life is
A.
B.
C.
D. none of these
Answer : Option C
Explaination / Solution:




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Q.5

Predict the rate law of the following reaction based on the data given below

2A + B → C + 3D



A. rate = k [ A]2 [B]
B. rate = k [ A][B]2
C. rate = k [ A][B]
D. rate = k [ A]1/2 [B]3/2
Answer : Option B
Explaination / Solution:




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Q.6

Assertion: rate of reaction doubles when the concentration of the reactant is doubles if it is a first order reaction.

Reason: rate constant also doubles
A. Both assertion and reason are true and reason is the correct explanation of assertion.
B. Both assertion and reason are true but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Both assertion and reason are false.
Answer : Option C
Explaination / Solution:

For a first reaction, If the concentration of reactant is doubled, then the rate of reaction also doubled.

Rate constant is independent of concentration and is a constant at a constant temperature,


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Q.7
The rate constant of a reaction is 5.8 × 10−2 s−1 . The order of the reaction is
A. First order
B. zero order
C. Second order
D. Third order
Answer : Option A
Explaination / Solution:

The unit of rate constant is s-1 and it indicates that the reaction is first order.

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Q.8
For the reaction  N2O5(g) → 2NO2 (g) + ½ O2(g), the value of rate of disappearance of N2O5 is given as 6.5 × 10-2 mol L-1 s-1. The rate of formation of NO2 and O2 is given  respectively as
A. ( 3.25 × 102 mol L1s1 ) and (1.3 × 102 mol L1s1 )
B. (1.3 × 102 mol L1s1 ) and ( 3.25 × 102 mol L1s1 )
C. (1.3 × 101 mol L1s1 ) and ( 3.25 × 102 mol L1s1 )
D. None of these
Answer : Option C
Explaination / Solution:




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Q.9
During the decomposition of H2O2 to give dioxygen, 48 g O2 is formed per minute at certain point of time. The rate of formation of water at this point is
A. 0.75 mol min1
B. 1.5 mol min1
C. 2.25 mol min1
D. 3.0 mol min1
Answer : Option D
Explaination / Solution:


no of moles of oxygen = (48/32) = 1.5 mol

rate of formation of oxygen = 2 ×1.5 = 3 mol min-1


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Q.10
If the initial concentration of the reactant is doubled, the time for half reaction is also doubled. Then the order of the reaction is
A. Zero
B. one
C. Fraction
D. none
Answer : Option A
Explaination / Solution:

For a first order reaction t1/2 is independent of initial concentration .i.e., n ≠ 1; for such cases



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