Question

During isothermal expansion of an ideal gas, its

• A. Internal energy increases
• B. Enthalpy decreases
• C. Enthalpy remains unaffected
• D. Enthalpy reduces to zero

Answer 1

The correct option is C Enthalpy remains unaffected

During isothermal expansion of an ideal gas,
$\Delta T=0,\Delta E=0$
We know that,
$H=E+PV$
$\Rightarrow \Delta H=\Delta E+\Delta \left(PV\right)\Rightarrow \Delta H=\Delta E+\Delta \left(nRT\right)$
$\therefore \Delta H=\Delta E+nR\Delta T=0+0=0$
Change in enthalpy is zero, means its enthalpy remains same or unaffected.