JEE Main 2020ChemistryChemical KineticsMediumNumerical

JEE Main 2020 — Chemical Kinetics Question with Solution

JEE Main 2020 (04 Sep Shift 1)

Question

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: log2=0.30 ;log2.5=0.40)

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Show full solutionCorrect answer: 60
Correct answer
60

Step-by-step explanation

T=2.303K log 100100−x%

T75%=2.303K log 10025=90

T60%=2.303K log 10040

T75%T60%=2log2log2.5 ⇒ 90T60%=2×0.30.4

T60%=90×46=60 min.

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About this question

This is a previous-year question from JEE Main 2020, 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.