JEE Main 2020ChemistryChemical KineticsEasyNumerical

JEE Main 2020 — Chemical Kinetics Question with Solution

JEE Main 2020 (07 Jan Shift 1)

Question

During the nuclear explosion, one of the products is 90Sr with half life of 6.93 years. If 1μg of 90Sr was absorbed in the bones of a newly born baby in place of Ca, how much time, in years, is required to reduce it by 90% if it is not lost metabolically ____________.

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Show full solutionCorrect answer: 23.03
Correct answer
23.03

Step-by-step explanation

Radioactive disintegration is always a first order reaction for a first order reaction. Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation.
 
Kt=2.303  log A o A t
 
where A o = initial concentration

A t = concentration at time ‘t’

t 1 2 = 0.693 K K= 0.693 t 1 2 = 0.693 6.93 ⇒0.1 yent s −1 t 90% = 2.303 0.1 log 100 10 t 90% =23.03 years.

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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.