Question

Calculate the work done when one mole of gas is allowed to expand freely in vacuum?

• A. $20\text{J}$
• B. $0\text{J}$
• C. $10\text{J}$
• D. $\text{None of the above}$

Answer 1

The correct option is B $0\text{J}$

Gas expands in vacuum, so it is a case of free expansion i.e., $P_{ext}=0$ and thus, it is an irreversible process.
Therefore, $W=-P_{ext}(V_2-V_1)=0$
In free expansion, the gas is expanding in vaccuum and the molecules move freely i.e the gas expands against no force.