Question:medium

Calculate the work done in joule if 1 mole of an ideal gas compressed from volume 24 dm$^3$ to 13 dm$^3$ at constant external pressure 3 bar.

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Sign convention is crucial!
- Expansion ($V_2 > V_1$): System does work, $W$ is negative.
- Compression ($V_2 < V_1$): Work is done on the system, $W$ is positive.
Updated On: Jun 19, 2026
  • 3300 J
  • 2250 J
  • 4400 J
  • 4870 J
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The Correct Option is A

Solution and Explanation

Step 1: Understanding the Concept:
Work done in a chemical process under constant external pressure is called pressure-volume work ($PV$ work). When a gas is compressed, work is done on the system, so the sign of work is positive ($W > 0$).

Step 2: Formula Application:

The formula for work done is $W = -P_{ext} \Delta V = -P_{ext}(V_2 - V_1)$. To convert the result from $bar \cdot dm^3$ to Joules, we use the conversion factor: $1 \text{ bar} \cdot dm^3 = 100 \text{ J}$.

Step 3: Explanation:

Given: $P_{ext} = 3$ bar, $V_1 = 24$ dm$^3$, $V_2 = 13$ dm$^3$. $\Delta V = V_2 - V_1 = 13 - 24 = -11$ dm$^3$. $W = -(3 \text{ bar}) \times (-11 \text{ dm}^3) = 33 \text{ bar} \cdot dm^3$. Converting to Joules: $W = 33 \times 100 \text{ J} = 3300 \text{ J}$.

Step 4: Final Answer:

The work done is 3300 J.
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