JEE Main 2023ChemistryChemical KineticsHardNumerical

JEE Main 2023 — Chemical Kinetics Question with Solution

JEE Main 2023 (25 Jan Shift 2)

Question

A first order reaction has the rate constant,  k=4.6×10-3 s-1. The number of correct statement/s from the following is/are Given: log 3=0.48.

A. Reaction completes in 1000 s.
B. The reaction has a half-life of 500 s.
C. The time required for 10% completion is 25 times the time required for 90% completion.
D. The degree of dissociation is equal to 1-e-kt.
E. The rate and the rate constant have the same unit.

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Show full solutionCorrect answer: 1
Correct answer
1

Step-by-step explanation

For a first order reaction:
t12 = 0.693k = 0.6934.6×10-3 s-1 = 150.65 s

For a first order reaction,
t10%=1Klnaa-x=1Kln10090

t10%=2.303 K(log 10-log 9)

t10%=2.093 K×(0.04)


Similarly

t90%=1 Kln10010

t90%=2.303 K

t90%t10%=10.04=25


We know,
ekt=aa-x

a-xa=e-kt

x=a1-e-kt

α=xa=1-e-kt

Thus, only option (D) is correct.

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About this question

This is a previous-year question from JEE Main 2023, covering the Chemical Kinetics chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.