Reaction A ( g ) rightarrow 2 B ( g )+ C ( g ) is a first order reaction. It was started with pure A t/min Pressure of system at time t/mm Hg --- --- 10 160 ∞ 240 Which of the following option is incorrect?

Rate constant of the reaction is 1.693 min -1

Partial pressure of A after 10 minute is 40 mm Hg

Initial pressure of A is 80 mm Hg

The reaction never goes to completion

Chemistry · Chemical Kinetics

JEE Main 2025 — 7 April, Morning Shift — Question 1

Reaction $\mathrm{A}(\mathrm{g}) \rightarrow 2 \mathrm{~B}(\mathrm{~g})+\mathrm{C}(\mathrm{g})$ is a first order reaction. It was started with pure $A$

t/min	Pressure of system at time t/mm Hg
10	160
$\infty$	240

Which of the following option is incorrect?

Option A:
Partial pressure of A after 10 minute is 40 mm Hg
Option B:
Initial pressure of $A$ is 80 mm Hg
Option C:
The reaction never goes to completion
Option D:
Rate constant of the reaction is $1.693 \mathrm{~min}^{-1}$
Correct

Answer: D

Step-by-step solution

$A \rightarrow 2 B+C$

$t-0 \quad a_{0}$

t-t $a_{0}-x \quad 2 x \quad x$

$t-\infty \quad 0 \quad$ 2ao a0

Now, $a_{0}+2 x=160$

\begin{gathered} 3 a_{0}=240 \mathrm{a}_{0}=80 x=40 \end{gathered}

So, now

A \rightarrow 2 B+C

$\mathrm{t}=0 \quad 80$

$\mathrm{t}=\mathrm{t} \quad 40(2 \times 40) 40$

$\mathrm{k}=\frac{2.303}{10} \times \log \frac{80}{40}$

$=0.0693 \mathrm{~min}^{-1}$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 7 April, Morning Shift
Subject: Chemistry
Chapter: Chemical Kinetics
Topic: Catalysis, Parallel and Sequential Reactions + Miscellaneous Problems