Which of the following curves represents a first-order reaction?

1. 
2. 
3. 
4. 
Subtopic:  First Order Reaction Kinetics |
 85%
From NCERT
Please attempt this question first.
Hints
Please attempt this question first.

Half-life of substance A following first order kinetics is 5 days. Starting with 100g of A, the amount left after 15 days will be: 

1.  25 g 

2. 50 g 

3. 12.5 g 

4. 6.25 g 

Subtopic:  First Order Reaction Kinetics |
 86%
From NCERT
Please attempt this question first.
Hints
Please attempt this question first.

If 'a' is the initial concentration of a substance that reacts according to zero-order kinetics and k is the rate constant, then the time for the reaction to go to completion is:
1. a/k
2. 2/ka
3. k/a
4. 2k/a

Subtopic:  First Order Reaction Kinetics |
 85%
From NCERT
To view explanation, please take trial in the course.
NEET 2025 - Target Batch
Hints
To view explanation, please take trial in the course.
NEET 2025 - Target Batch

In a first order reaction, time required for completion of 99.9% is X times of half-life (t1/2) of the reaction. When reaction is completed 99.9%, [R]n = [R]0 – 0.999[R]0 .The value of X is-

1. 5
2. 10
3. 15
4. 20

Subtopic:  First Order Reaction Kinetics |
 80%
From NCERT
To view explanation, please take trial in the course.
NEET 2025 - Target Batch
Hints
To view explanation, please take trial in the course.
NEET 2025 - Target Batch

The reaction of hydrogen and iodine monochloride is given as: 
H2(g) + 2ICl(g) → 2HCl(g) + I2(g
This reaction is of first order with respect to H2(g) and ICl(g), for which of the following proposed mechanisms:
Mechanism A: 
H2(g) + 2ICl(g) → 2HCl(g) + I2(g
Mechanism B: 
H2(g) + ICl(g) →HCl(g) + HI(g); slow 
HI(g) + ICl(g) →HCl(g) + I2(g); fast

1. B Only

2. A and B both

3. Neither A nor B

4. A only

Subtopic:  First Order Reaction Kinetics |
 63%
From NCERT
AIPMT - 2007
To view explanation, please take trial in the course.
NEET 2025 - Target Batch
Hints
To view explanation, please take trial in the course.
NEET 2025 - Target Batch

If 75 % of a first-order reaction was completed in 90 minutes, 60 % of the same reaction would be completed in approximately (in minutes):

(Take : log 2 = 0.30 ; log 2.5 = 0.40)

1. 50 min

2. 60 min

3. 70 min

4. 65 min

Subtopic:  First Order Reaction Kinetics |
 83%
From NCERT
Please attempt this question first.
Hints
Please attempt this question first.

The correct graphical representation of first-order reaction is:

(a)  (b)
(c) (d)


 

1. (a) and (b) 2. (b) and (c)
3. (c) and (d) 4. (a) and (d)
Subtopic:  First Order Reaction Kinetics |
 81%
From NCERT
To view explanation, please take trial in the course.
NEET 2025 - Target Batch
Hints
Links
To view explanation, please take trial in the course.
NEET 2025 - Target Batch

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 |
 63%
From NCERT
To view explanation, please take trial in the course.
NEET 2025 - Target Batch
Hints
Links
To view explanation, please take trial in the course.
NEET 2025 - Target Batch

For a first-order reaction A → B the reaction rate at a reactant concentration of 0.01M is found to be 2.0×105 mole L1 s1. The half-life period of the reaction is:

1. 300s 2. 30s
3. 220s 4. 347s
Subtopic:  First Order Reaction Kinetics |
 84%
From NCERT
AIPMT - 2005
To view explanation, please take trial in the course.
NEET 2025 - Target Batch
Hints
To view explanation, please take trial in the course.
NEET 2025 - Target Batch