Chemistry · Chemical Kinetics

JEE Main 2025 — 3 April, Morning Shift — Question 9

In a reaction $A+B \rightarrow C$ , initial concentrations of $A$ and $B$ are related as $[A]_{0}=8[B]_{0}$ . The half lives of $A$ and $B$ are 10 min and 40 min , respectively, If they start to disappear at the same time, both following first order kinetics, after how much time will the concentration of both the reactants be same?

Option A:
40 min
Correct
Option B:
20 min
Option C:
80 min
Option D:
60 min

Answer: A

Step-by-step solution

$\underset{8 B_{0}}{A} \xrightarrow{10} 4 B_{0} \xrightarrow{10} 2 B_{0} \xrightarrow{10} B_{0} \xrightarrow{10} \frac{B_{0}}{2}$

$\underset{\mathrm{B}_{0}}{\mathrm{~B}} \xrightarrow{40} \frac{\mathrm{~B}_{0}}{2}$

$\mathrm{t}=40$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 3 April, Morning Shift
Subject: Chemistry
Chapter: Chemical Kinetics
Topic: Integrated Rate Laws