Question

Which thermodynamic parameter is not a state function ?

• A. q at constant pressure
• B. q at constant volume
• C. W at adiabatic
• D. W at isothermal

Answer 1

The correct option is D W at isothermal

$W$ and $q$ are not state functions

$H$ and $U$ are state functions

$\Delta H=\Delta U+\Delta PV$

At constant pressure, $\Delta H=\Delta U+P\Delta V$ $\Delta P=0$ $\Delta H=q_p$

At constant volume, $\Delta H=\Delta U+V\Delta P$ $\Delta V=0$ $\Delta U=q_v$

So, the first two options are state function.

$\Delta U=q-W$ $(\because q=0)$ $[\therefore$ Adialentic process$]$

$\Delta U=-W$ (state function)

Work done in isotheromal process is not a state

function

$W=-q(\because \Delta T=0,q\ne 0)$

$\therefore$ option D is correct.