Question 644: Thermodynamics & KTG

Question

In case of free expansion, which one of the following statements is WRONG?

Accepted Answer

Free expansion = expansion of a gas into a vacuum without external pressure.
It happens spontaneously (uncontrolled, irreversible).
During free expansion, the system is not in thermodynamic equilibrium, because pressure and temperature inside may not be uniform.
Since it is highly irreversible, it cannot be represented by a well-defined path on a $P$Ã¢ÂÂ$V$ diagram (only initial and final states are meaningful).
Options analysis:
A. It is an instantaneous change.
Ã¢ÂÂ Yes, practically it happens suddenly (instantaneous). Correct statement.
B. The system is not in thermodynamic equilibrium.
Ã¢ÂÂ Correct, because it's an irreversible and non-equilibrium process.
C. Free expansion can be plotted on a PÃ¢ÂÂV diagram.
Ã¢ÂÂ Wrong. Only equilibrium (quasi-static) processes can be represented as a continuous path. For free expansion, only initial and final points can be marked, not the path.
D. It is an uncontrolled change.
Ã¢ÂÂ Correct, free expansion is uncontrolled and irreversible.
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Answer: Option C is WRONG.

Answer

It is an instantaneous change.

Answer

The system is not in thermodynamic equilibrium.

Answer

Free expansion can be plotted on a P-V diagram.

Answer

It is an uncontrolled change.

Thermodynamics & KTG

In case of free expansion, which one of the following statements is WRONG?

Choose the correct answer: