Question:
Calculate the work done, when three moles of an ideal gas expand isothermally from \(16dm^{3}\) to \(20dm^{3}\), at a constant external pressure of \(1.5\) bar.
Calculate the work done, when three moles of an ideal gas expand isothermally from \(16dm^{3}\) to \(20dm^{3}\), at a constant external pressure of \(1.5\) bar.
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Work done against a constant external pressure is minus pressure times volume change; the number of moles does not matter.
Updated On: Nov 12, 2026
- \(600\) J
- \(-600\) J
- \(-400\) J
- \(400\) J
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept
For expansion against a constant external pressure, \(w=-p_{ext}\,\Delta V\).
Step 2: Find the Volume Change
\(\Delta V=20-16=4\,\text{dm}^3=4\times10^{-3}\,\text{m}^3\).
Step 3: Convert the Pressure
\(p_{ext}=1.5\,\text{bar}=1.5\times10^{5}\,\text{Pa}\).
Step 4: Calculation
\(w=-1.5\times10^{5}\times4\times10^{-3}=-600\,\text{J}\), option (B).
Final Answer:
The work done is \(-600\) J. \[ \boxed{\text{(B) }-600\text{ J}} \]
For expansion against a constant external pressure, \(w=-p_{ext}\,\Delta V\).
Step 2: Find the Volume Change
\(\Delta V=20-16=4\,\text{dm}^3=4\times10^{-3}\,\text{m}^3\).
Step 3: Convert the Pressure
\(p_{ext}=1.5\,\text{bar}=1.5\times10^{5}\,\text{Pa}\).
Step 4: Calculation
\(w=-1.5\times10^{5}\times4\times10^{-3}=-600\,\text{J}\), option (B).
Final Answer:
The work done is \(-600\) J. \[ \boxed{\text{(B) }-600\text{ J}} \]
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