Question

An ideal gas undergoes isothermal expansion at constant pressure. During the process:

• A. enthalpy remains constant but entropy increases
• B. enthalpy increases but entropy decreases
• C. Both enthalpy and entropy remain constant
• D. enthalpy decreases but entropy increases

Answer 1

The correct option is C Both enthalpy and entropy remain constant

Both enthalpy and entropy remain constant.

During isothermal expansion, temperature, as well as pressure, remains constant. So, enthalpy remains constant,

$\Delta S=\frac{\Delta q}{T}$

where $\Delta q=\Delta H$

$\Rightarrow$

entropy is also constant,

where $\Delta S=\frac{\Delta H}{T}$