Question

Choose the correct statement for the work done in the expansion and heat absorbed or released when 5 litres of an ideal gas at 10 atmospheric pressure isothermally expands into vacuum until volume is 15 litres :

• A. Both the heat and work done will be greater than zero
• B. Heat absorbed will be less than zero and work done will be positive
• C. Work done will be zero and heat will also be zero
• D. Work done will be greater than zero and heat will remain zero

Answer 1

The Correct Option is C

In an isothermal free expansion into a vacuum, the gas performs no work as the external pressure is zero. Consequently, the internal energy of the ideal gas remains constant \((\Delta U=0)\) due to the isothermal process. Applying the first law of thermodynamics, \(\Delta U = q + w\), where q represents heat absorbed and w represents work done. Given that \(\Delta U=0\) and \(w=0\), it follows that the heat absorbed (q) is also zero.