Question

Which of the following is incorrect regarding isothermal expansion of an ideal gas?

• A. $\Delta H\ne 0$
• B. $\Delta E=0$
• C. $\Delta G=-T\Delta S$
• D. $T_{final}=T_{initial}$

Answer 1

Answer: (A), (D)

The correct options are
A $\Delta H\ne 0$
D $T_{final}=T_{initial}$

By the first law of thermodynamics, $dU=dq+dw$

In an isothermal process, we have $dU=0,dT=0$

By definition : $H=U+PV=U+nRT$

Therefore, $dH=dU+nRdT=0+0=0$

Hence, enthalpy change is also zero for an isothermal expansion of an ideal gas.