Mechanical Engineering - Thermodynamics - Discussion

For an ideal gas, temp remains constant during the free expansion process and internal energy & enthalpy both are a function of temperature so it becomes zero.

But this is not true for real gases.

And in question nothing mention about gases.

So, option incorrect should be the answer.

Well known that in free expansion temperature remains constant so internal energy must be constant.

But on another hand, because enthalpy is a point function and in this by considering the only initial and final point. It follows Boyle's law( PV=C). It is already seen that internal energy U is constant and so (U+PV)=C, and hence enthalpy remains constant.

For ideal gases, as we know, internal energy and enthalpy are a function of temperature only, so if internal energy U remains constant, temperature T also remains constant which means enthalpy also remains constant.