Consider the following gas phase reaction being carried out in a closed vessel at $25°C$. $2A(g) \rightarrow 4B(g) + C(g)$ time (min) total pressure of the system (mm Hg) $30$ $300$ $\infty$ $600$ The pressure of $C(g)$ at $30$ minutes time interval would be _______ mm Hg. (nearest integer)

JEE Main 2026 — Chemistry Physical Chemistry

2026integermedium

Consider the following gas phase reaction being carried out in a closed vessel at $25°C$ .

$2A(g) \rightarrow 4B(g) + C(g)$

time (min)	total pressure of the system (mm Hg)
$30$	$300$
$\infty$	$600$

The pressure of

C(g)

30

minutes time interval would be _______ mm Hg. (nearest integer)

Official previous-year question

Held on 2 Apr 2026 · Verified 6 Jul 2026.

Did you get this right?

Solution

For the given gas phase reaction:

$2A(g) \rightarrow 4B(g) + C(g)$

Let the initial pressure of $A(g)$ be $P_0$ .

At $t = 0$ : $P_A = P_0$ , $P_B = 0$ , $P_C = 0$

At $t = t$ : $P_A = P_0 - 2p$ , $P_B = 4p$ , $P_C = p$

Total pressure at time $t$ , $P_t = P_0 - 2p + 4p + p = P_0 + 3p$

At $t = \infty$ , the reaction is complete, so $P_A = 0 \Rightarrow 2p = P_0 \Rightarrow p = \dfrac{P_0}{2}$

Total pressure at $t = \infty$ , $P_{\infty} = 4\left(\dfrac{P_0}{2}\right) + \dfrac{P_0}{2} = \dfrac{5P_0}{2}$

Given $P_{\infty} = 600$ mm Hg:

$\dfrac{5P_0}{2} = 600 \Rightarrow P_0 = 240$ mm Hg

At $t = 30$ min, $P_t = 300$ mm Hg:

$P_0 + 3p = 300$

$240 + 3p = 300 \Rightarrow 3p = 60 \Rightarrow p = 20$ mm Hg

The pressure of $C(g)$ at $30$ minutes is $p = 20$ mm Hg.

Answer: $20$

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JEE Main 2026 — Chemistry Physical Chemistry

2026integermedium

Consider the following gas phase reaction being carried out in a closed vessel at $25°C$ .

$2A(g) \rightarrow 4B(g) + C(g)$

time (min)	total pressure of the system (mm Hg)
$30$	$300$
$\infty$	$600$

The pressure of

C(g)

30

minutes time interval would be _______ mm Hg. (nearest integer)

Official previous-year question

Held on 2 Apr 2026 · Verified 6 Jul 2026.

Did you get this right?

Solution

For the given gas phase reaction:

$2A(g) \rightarrow 4B(g) + C(g)$

Let the initial pressure of $A(g)$ be $P_0$ .

At $t = 0$ : $P_A = P_0$ , $P_B = 0$ , $P_C = 0$

At $t = t$ : $P_A = P_0 - 2p$ , $P_B = 4p$ , $P_C = p$

Total pressure at time $t$ , $P_t = P_0 - 2p + 4p + p = P_0 + 3p$

At $t = \infty$ , the reaction is complete, so $P_A = 0 \Rightarrow 2p = P_0 \Rightarrow p = \dfrac{P_0}{2}$

Total pressure at $t = \infty$ , $P_{\infty} = 4\left(\dfrac{P_0}{2}\right) + \dfrac{P_0}{2} = \dfrac{5P_0}{2}$

Given $P_{\infty} = 600$ mm Hg:

$\dfrac{5P_0}{2} = 600 \Rightarrow P_0 = 240$ mm Hg

At $t = 30$ min, $P_t = 300$ mm Hg:

$P_0 + 3p = 300$

$240 + 3p = 300 \Rightarrow 3p = 60 \Rightarrow p = 20$ mm Hg

The pressure of $C(g)$ at $30$ minutes is $p = 20$ mm Hg.

Answer: $20$

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

Work through every JEE Main Physical Chemistry PYQ, year by year.

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JEE Main 2026 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

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JEE Main 2026 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

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