The rate constant of a first-order reaction is\(4 \times 10^{-3} \mathrm{sec}^{-1}.\) At a reactant concentration of \(0.02~\mathrm{M},\) the rate of reaction would be:

1. \(8 \times 10^{-5} \mathrm{M} ~\mathrm{sec}^{-1} \) 2. \(4 \times 10^{-3} \mathrm{M} ~\mathrm{sec}^{-1} \)
3. \(2 \times 10^{-1} \mathrm{M}~ \mathrm{sec}^{-1} \) 4. \(4 \times 10^{-1} \mathrm{M}~ \mathrm{sec}^{-1}\)
Subtopic:  First Order Reaction Kinetics |
 80%
Level 1: 80%+
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For a reaction of the type 2A + B  2C, the rate of the reaction is given by kA2B. When the volume of the reaction vessel is reduced to 14 th of the original volume, the rate of reaction changes by a factor of:

1. 0.25                                                          

2. 16

3. 64                                                             

4. 4

Subtopic:  Definition, Rate Constant, Rate Law | First Order Reaction Kinetics |
 76%
Level 2: 60%+
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For the elementary reaction M  N, the rate of disappearance of M increases by a factor of 8 upon doubling the concentration of M. The order of the reaction with respect to M will be:

1. 4

2. 3

3. 2

4. 1

Subtopic:  First Order Reaction Kinetics |
 78%
Level 2: 60%+
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The rate of a reaction increases 4-fold when concentration of reactant is increased 16 times.

If the rate of reaction is 4 × 10-6 mol L-1s-1 when concentration of the reactant is 4 × 10-4  mol L-1, the rate constant of the reaction will be : 

1. 2 × 10-4 m1/2 L-1/2 s-1                            

2. 1 × 10-2 s-1

3. 4 × 10-4 mol-1/2 L-1/2 s-1                         

4. 25 mol-1L min-1                              

Subtopic:  First Order Reaction Kinetics |
 60%
Level 2: 60%+
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If ‘a’ is the initial concentration of a substance which reacts according to zero-order kinetics and k is the rate constant, the time for the reaction to go to completion will be:

1. a/k 2. 2/ka
3. k/a 4. Infinite
Subtopic:  Definition, Rate Constant, Rate Law | First Order Reaction Kinetics |
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Level 2: 60%+
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For a general reaction A → B, the plot of concentration of A vs time is given below:

The unit of the rate constant would be:

1. \(\mathrm{mol}^{-1} \mathrm{~L}^{-1} \mathrm{~s}^{-1} \) 2. \(s^{-1} \)
3. \(\mathrm{mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1} \) 4. None of the above

Subtopic:  First Order Reaction Kinetics |
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Level 2: 60%+
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Half-life is independent of the concentration of a reactant. After 10 minutes, the volume of N2 gas is 10 L and after complete reaction, it is 50 L. Hence, the rate constant is:

1. 2.30310log 5 min-1

2. 2.30310 log 1.25 min-1

3. 2.30310 log 2 min-1

4. 2.30310 log 4 min-1

Subtopic:  First Order Reaction Kinetics |
Level 3: 35%-60%
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A first-order reaction is 15 % completed in 20 minutes. The amount of time required to complete 60 % of the reaction is:

1. 112.8 min 2. 120.7 min
3. 100.4 min 4. 140.7 min
Subtopic:  First Order Reaction Kinetics |
Level 3: 35%-60%
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If the rate constant of a reaction is \(0.03 s^{-1}\), how much time does it take for \(7.2\text { mol L}^{-1}\) concentration of the reactant to get reduced to \(0.9~\text {mol L} ^{-1}?\)
(Given: log 2=0.301)
1. 210 s
2. 21.0 s
3. 69.3 s
4. 23.1 s
Subtopic:  First Order Reaction Kinetics |
 64%
Level 2: 60%+
NEET - 2025
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Consider the first-order gas-phase decomposition reaction given below.

A(g) → B(g) + C(g)

The initial pressure of the system before the decomposition of A was Pi. After the lapse of time t, the total pressure of the system increased by X units and became Pt. The rate constant k for the reaction is:

1. k=2.303tlogPiPix 2. k=2.303tlogPi2PiPt
3. k=2.303tlogPi2Pi+Pt 4. k=2.303tlogPiPi+x
Subtopic:  First Order Reaction Kinetics |
 66%
Level 2: 60%+
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