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Chemical Kinetics

JEE Main 2025 (Online) 2nd April Evening ShiftMCQMedium📈 Topic in 11% papers+4−1
Ques. 1JEE Main 2025, 2 April (Evening Shift)

Reactant A converts to product D through the given mechanism (with the net evolution of heat): A B slow; H = +ve B C fast; H = -ve C D fast; H = -ve Which of the following represents the above reaction mechanism?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]

Answer

(4) [figure]

Solution

Read the energy profile from the data:

(i) A B is endothermic intermediate B lies above A.

(ii) A B is the slow (rate-determining) step it has the highest transition state (the tallest barrier).

(iii) B C and C D are fast and exothermic small barriers, and C lies below B, D below C.

(iv) Net evolution of heat product D lies below reactant A.

Graph (1): D is above A (net endothermic). Graph (2): the last barrier is the highest. Graph (3): C is above B and the later barriers are higher.

Only graph (4) satisfies all four conditions.

Answer: (4)

Keep practising — Chemical Kinetics

Ques. 2JEE Main 2025, 2 April (Evening Shift)

For the reaction A B the following graph was obtained. The time required (in seconds) for the concentration of A to reduce to 2.5 g L-1 (if the initial concentration of A was 50 g L-1) is . (Nearest integer) Given : 2 = 0.3010 [figure]

Ques. 3JEE Main 2025, 29 January (Morning Shift)

The reaction A2 + B2 2AB follows the mechanism: A2 k-1 k1 A + A (fast) A + B2 k2 AB + B (slow) A + B AB (fast) The overall order of the reaction is:

  1. 3
  2. 2.5
  3. 1.5
  4. 2
Ques. 4JEE Main 2025, 29 January (Evening Shift)

Drug X becomes ineffective after 50\% decomposition. The original concentration of drug in a bottle was 16 mg/mL which becomes 4 mg/mL in 12 months. The expiry time of the drug in months is . Assume that the decomposition of the drug follows first order kinetics.

  1. 12
  2. 3
  3. 6
  4. 2
Ques. 5JEE Main 2025, 28 January (Morning Shift)

array|c|c| [A]0/ mol L-1 & t1/2/min \ 0.100 & 200 \ 0.025 & 100 \ array For a given reaction R P, t1/2 is related to [A]0 as given in table. Given: 2 = 0.30 Which of the following is true? Choose the correct answer from the options given below:

  1. A and C Only
  2. A, B and D Only
  3. A and B Only
  4. C and D Only
Ques. 6JEE Main 2025, 28 January (Evening Shift)

Consider an elementary reaction A(g) + B(g) C(g) + D(g) If the volume of reaction mixture is suddenly reduced to 13 of its initial volume, the reaction rate will become 'x' times of the original reaction rate. The value of x is :

  1. 3
  2. 9
  3. 13
  4. 19
Ques. 7JEE Main 2025, 28 January (Evening Shift)

For bacterial growth in a cell culture, growth law is very similar to the law of radioactive decay. Which of the following graphs is most suitable to represent bacterial colony growth? Where N - Number of bacteria at any time, N0 - Initial number of bacteria.

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 8JEE Main 2025, 24 January (Morning Shift)

For a reaction, N2O5(g) 2NO2(g) + 12O2(g) in a constant volume container, no products were present initially. The final pressure of the system when 50\% of reaction gets completed is

  1. 5/2 times of initial pressure
  2. 7/2 times of initial pressure
  3. 7/4 times of initial pressure
  4. 5 times of initial pressure
Ques. 9JEE Main 2025, 24 January (Evening Shift)

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Both Statement I and Statement II are false
  2. Statement I is true but Statement II is false
  3. Statement I is false but Statement II is true
  4. Both Statement I and Statement II are true
Ques. 10JEE Main 2025, 24 January (Evening Shift)

Consider a complex reaction taking place in three steps with rate constants k1, k2 and k3 respectively. The overall rate constant k is given by the expression k= k1k3k2. If the activation energies of the three steps are 60, 30 and 10 kJ mol-1 respectively, then the overall energy of activation in kJ mol-1 is . (Nearest integer)

Ques. 11JEE Main 2025, 23 January (Morning Shift)

For the thermal decomposition of N2O5(g) at constant volume, the following table can be formed, for the reaction mentioned below. 2N2O5(g) 2N2O4(g)+O2(g) [figure] x= 10-3 atm [nearest integer] Given : Rate constant for the reaction is 4.606 10-2 s-1.

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