A container is divided into two equal portions. One portion contains an ideal gas at pressure P and temperature T while the other portion is a perfect vacuum. If a hole is opened between two portions:
Correct answer: C. There will be no change in internal energy
- A. There will be a change in internal energy
- B. There will be a change in temperature
- C. There will be no change in internal energy
- D. The external pressure will increase
Explanation
This describes a free expansion process into a vacuum. Since no external pressure is overcome, the work done (W) is zero. As the container is insulated, heat transfer (Q) is also zero. According to the first law (ΔU = Q - W), the change in internal energy (ΔU) must also be zero.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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