Chemistry · Thermodynamics & Thermochemistry

JEE Main 2025 — 2 April, Morning Shift — Question 10

Two vessels $A$ and $B$ are connected via stopcock. The vessel A is filled with a gas at a certain pressure. The entire assembly is immersed in water and is allowed to come to thermal equilibrium with water. After opening the stopcock the gas from vessel A expands into vessel B and no change in temperature is observed in the thermometer. Which of the following statement is true?

Option A:
$\mathrm{dq} \neq 0$
Option B:
$d w \neq 0$
Option C:
$d U \neq 0$
Option D:
The pressure in the vessel $B$ before opening the stopcock is zero
Correct

Answer: D

Step-by-step solution

The pressure in the vessel B before opening the stopcock is zero because $\mathrm{dT}=0$ . Therefore,

$\mathrm{dq}=0$

$dw$ $=0$

$\mathrm{dU}=0$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 2 April, Morning Shift
Subject: Chemistry
Chapter: Thermodynamics & Thermochemistry
Topic: Internal Energy and the First Law