Free expansion of gas within a system is

Free expansion of gas within a system is


a. a reversible process
b. an irreversible process
c. a quasi-static process
d. none of the above

Correct Answer: b. an irreversible process

Free expansion of gas


Consider the above diagram, a system contains gas in the compartment 1 and vacuum is separated by a diaphragm in compartment 2. If the diaphragm is removed then the gas in compartment 1 will expand into the compartment 2 until the pressure in both the compartments will become equal. This is a spontaneous process.

It is not possible to return the gas in the compartment 2 into the compartment 1 with increase in the pressure, without any other effect on the system. To return this process, the external work has to be done on the system. Therefore it a irreversible process.
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