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Chemical Kinetics · Question 16

JEE Main 2026 (Online) 24th January Morning ShiftMCQMedium📈 Topic in 10% papers+4−1
1

A D is an endothermic reaction occurring in three steps (elementary). (i) A B, Hi = +ve (ii) B C, Hii = -ve (iii) C D, Hiii = -ve Which of the following graphs between potential energy (y-axis) vs reaction coordinate (x-axis) correctly represents the reaction profile of A D?

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

Answer

(4) [figure]

Solution

In a potential energy profile, the level after each hump is the energy of the product of that step.

Step (i) endothermic E(B) > E(A)

Step (ii) exothermic E(C) < E(B)

Step (iii) exothermic E(D) < E(C)

Overall endothermic E(D) > E(A)

E(B) > E(C) > E(D) > E(A)

Graph (1): E(C) > E(B), wrong. Graph (2): E(D) > E(C), wrong. Graph (3): E(B) < E(A), wrong.

Graph (4): the minimum after each hump is lower than the previous one, but the final level D is still above the initial level A. Correct.

Answer: (4)

JEE Main 2026 (Online) 24th January Morning Shift

Keep practising — Chemical Kinetics

2

At 27 in presence of a catalyst, activation energy of a reaction is lowered by 10 kJ mol-1. The logarithm of ratio of k (catalysed)k (uncatalysed) is.... (Consider that the frequency factor for both the reactions is same)

  1. 1.741
  2. 0.1741
  3. 17.41
  4. 3.482
JEE Main 2026 (Online) 24th January Morning Shift
3

The half-life of 65Zn is 245 days. After x days, 75\% of original activity remained. The value of x in days is . (Nearest integer) (Given: 3 = 0.4771 and 2 = 0.3010)

JEE Main 2026 (Online) 24th January Evening Shift
4

For the thermal decomposition of reactant AB(g), the following plot is constructed. [figure] The half-life of the reaction is 'x' min. x = min. (Nearest integer)

JEE Main 2026 (Online) 23rd January Morning Shift
5

[figure] Given above is the concentration vs time plot for a dissociation reaction : A nB. Based on the data of the initial phase of the reaction (initial 10 min), the value of n is .

  1. 2
  2. 5
  3. 4
  4. 3
JEE Main 2026 (Online) 23rd January Evening Shift
6

Observe the following reactions at T(K). I. A products. II. 5Br-(aq) + BrO3-(aq) + 6H+(aq) 3Br2(aq) + 3H2O(l) Both the reactions are started at 10.00 am. The rates of these reactions at 10.10 am are same. The value of - [Br-] t at 10.10 am is 2 10-4 mol L-1 min-1. The concentration of A at 10.10 am is 10-2 mol L-1. What is the first order rate constant (in min-1) of reaction I?

  1. 4 10-3
  2. 2 10-3
  3. 10-3
  4. 10-2
JEE Main 2026 (Online) 23rd January Evening Shift
7

A product (First order reaction). Three sets of experiments were performed for a reaction under similar experimental conditions: Run 1 100 mL of 10 M solution of reactant A Run 2 200 mL of 10 M solution of reactant A Run 3 100 mL of 10 M solution of reactant A + 100 mL of H2O added. The correct variation of rate of reaction is

  1. Run 1 = Run 2 = Run 3
  2. Run 3 < Run 1 < Run 2
  3. Run 1 < Run 2 < Run 3
  4. Run 3 < Run 1 = Run 2
JEE Main 2026 (Online) 22nd January Morning Shift
8

The temperature at which the rate constants of the given below two gaseous reactions become equal is K. (Nearest integer) X Y, k1 = 106 e -30000T P Q, k2 = 104 e -24000T Given : 10 = 2.303

JEE Main 2026 (Online) 22nd January Morning Shift
9

Correct statements regarding Arrhenius equation among the following are : Choose the correct answer from the options given below :

  1. A and B Only
  2. B and D Only
  3. B and C Only
  4. A and C Only
JEE Main 2026 (Online) 22nd January Evening Shift
10

Consider A k1 B and C k2 D are two reactions. If the rate constant (k1) of the A B reaction can be expressed by the following equation 10 k = 14.34 - 1.5 104T/K and activation energy of C D reaction (Ea2) is 15th of the A B reaction (Ea1), then the value of (Ea2) is kJ mol-1. (Nearest Integer)

JEE Main 2026 (Online) 22nd January Evening Shift
11

Pre-exponential factors of two different reactions of same order are identical. Let activation energy of first reaction exceed the activation energy of second reaction by 20 kJ mol-1. If k1 and k2 are the rate constants of first and second reaction respectively at 300 K, then k2k1 will be . (nearest integer) [R = 8.3 J K-1 mol-1]

JEE Main 2026 (Online) 21st January Morning Shift

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