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Chemical Kinetics · Question 4

JEE Main 2026 (Online) 5th April Morning ShiftMCQEasy📈 Topic in 29% papers+4−1
1

First order gas phase reaction A B + C pi = initial pressure of gas A, pt = total pressure of the reaction mixture at time t Expression of rate constant (k) is

  1. 1t pi2pi - pt
  2. 1t 2pipi - pt
  3. 1t pi3pi - 2pt
  4. 1t 3pi4pi - pt

Answer

(1) 1t pi2pi - pt

Solution

Let the pressure of A decrease by x at time t:

A(g) B(g) + C(g)

t = 0: pi, 0, 0

t: pi - x, x, x

⇒ pt = (pi - x) + x + x = pi + x ⇒ x = pt - pi

⇒ pA = pi - x = 2pi - pt

For a first order reaction, k = 1t pipA

∴ k = 1t pi2pi - pt

Answer: (1)

JEE Main 2026 (Online) 5th April Morning Shift

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2

If the half life of a first order reaction is 6.93 minutes then the time required for completion of 99% of the reaction will be minutes. (Given : log 2 = 0.3010)

JEE Main 2026 (Online) 5th April Morning Shift
3

For a reaction A → P at T K, the half life (t1/2) is plotted as a function of initial concentration [A]0 of A as given below. [figure] The value of x in the given figure is s (Nearest integer)

JEE Main 2026 (Online) 5th April Evening Shift
4

Consider the first order reaction R P. The fraction of molecules decomposed in the given first order reaction can be expressed as

  1. 1 - ek1t
  2. 1 + ek1t
  3. 1 + e-k1t
  4. 1 - e-k1t
JEE Main 2026 (Online) 4th April Morning Shift
5

Consider the given graph showing variation of reactant concentration with time. Three different reactions were started with identical initial concentration of reactants. Which of the following statement is correct? [figure]

  1. The order of all the three reactions is same.
  2. The rate constant of reaction 3 is larger than the rate constant of reaction 2 if the order of reaction is same for both.
  3. The SI unit of rate constant of reaction 1 is s-1.
  4. Thermal decomposition of HI on gold surface is an example of reaction 2.
JEE Main 2026 (Online) 4th April Evening Shift
6

For a first order reaction A B arrayll t/min & [A]/M \ 0 & 0.6500 \ x & 0.0650 \ 20 & 0.00065 array x = min. (Nearest integer)

JEE Main 2026 (Online) 4th April Evening Shift
7

t100\% is the time required for the 100% completion of the reaction while t1/2 is the time required for 50% of the reaction to be completed. Which of the following option correctly represents the relation between t100\% and t1/2 for zero and first order reactions respectively ?

  1. t100\% = (t1/2)2 and t100\% = (t1/2)-
  2. t100\% = 2t1/2 and t100\% = (t1/2)
  3. t100\% = 2t1/2 and t100\% = (2t1/2)2
  4. t100\% = (t1/2) and t100\% = 2t1/2
JEE Main 2026 (Online) 2nd April Morning Shift
8

For reaction A P, rate constant k = 1.5 103 s-1 at 27°C If activation energy for the above reaction is 60 kJ mol-1, then the temperature (in °C) at which rate constant, k = 4.5 103 s-1 is . (Nearest integer) Given : log 2 = 0.30, log 3 = 0.48, R = 8.3 J K-1 mol-1, ln 10 = 2.3

JEE Main 2026 (Online) 2nd April Morning Shift
9

Consider the reaction aX bY, for which the rate constant at 30°C is 1 10-3 mol-1 L s-1. Which of the following statements are true? Choose the correct answer from the options given below:

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

Consider the following gas phase reaction being carried out in a closed vessel at 25°C. 2A(g) 4B(g) + C(g) array|c|c| time (min) & total pressure of the system (mm Hg) \ 30 & 300 \ & 600 \ array The pressure of C(g) at 30 minutes time interval would be mm Hg. (nearest integer)

JEE Main 2026 (Online) 2nd April Evening Shift
11

An organic compound undergoes first order decomposition. The time taken for decomposition to ( 18 )th and ( 110 )th of its initial concentration are t1/8 and t1/10 respectively. What is the value of t1/8 t1/10 10? ( 2 = 0.3)

  1. 30
  2. 9
  3. 3
  4. 0.9
JEE Main 2026 (Online) 28th January Morning Shift

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