Question

For a cyclic process the condition is:

• A. $\Delta U=0$
• B. $\Delta H=0$
• C. $\Delta U>0$ and $\Delta H>0$
• D. Both $\Delta U=0$ & $\Delta H=0$

Answer 1

The correct option is D

Both $\Delta U=0$ & $\Delta H=0$

By definition if a system undergoes a number of different processes and finally returns to its initial state, it is called a cyclic process. Therefore there is no change in internal energy & enthalpy.

$\Delta U=0$ {As the system reaches initial state}

We have $H=U+PV$

$\therefore \Delta H=\Delta U+P\Delta V$ {As the system reaches initial state}

+ $V\Delta P\Delta U=0$, $\Delta V=0$ & $\Delta P=0$

$\therefore \Delta H=0+(P\times 0)+(V\times 0)$

$\therefore \Delta H=0$