JEE Main 2022 · ChemistryMultiple choiceSingle correctEasyCalculation

JEE Main 24 June 2022, Shift 2, Chemistry Q65

Question 65 of 90 in this shift, Chemistry question 5 of 30, Section A.

For a first order reaction, the time required for completion of 90% reaction is 'x' times the half life of the reaction. The value of 'x' is (Given: ln 10 = 2.303 and log 2 = 0.3010)

(1)1.12
(2)2.43
(3)3.32Official answer
(4)33.31

Official answer

Option 3

NTA final key.

Chapter: Chemical Kinetics
Topic: Integrated Rate Equations
Idea tested: First Order Fractional Completion Shortcuts

Same idea in other shifts

Asked 6× in all

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28 Jun 2022, Shift 1 · Q88For a first order reaction A $\rightarrow$ B, the rate constant, k = $5.5 \times 10^{-14}$ $\mathrm{s^{-1}}$ . The time required for 67%…MediumNumerical value
24 Feb 2021, Shift 1 · Q58Gaseous cyclobutene isomerizes to butadiene in a first order process which has a ‘k’ value of $3.3\times10^{-4}\ \mathrm{s^{-1}}$ at 153°C.…MediumNumerical value
18 Mar 2021, Shift 2 · Q57A reaction has a half life of 1 min. The time required for 99.9% completion of the reaction is __________ min. (Round off to the Nearest…EasyNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.