Question

A gas expands isothermally against a constant external pressures of 1 atm from a volume of $10d{m}^3$ to a volume of $20d{m}^3$. It absorbs 800 J of thermal energy from its surroundings. Calculate the change in internal energy $\left(\Delta E\right)$.

Answer 1

$△T=0$ (isothermal process).

Internal energy change $\left(△E\right)=Q+W=n{C}_V△T$

But as $△T=0$,

Internal energy change $\left(△E\right)=n{C}_V△T=0$

Therefore, for isothermal process, the change in internal energy $\left(△E\right)$ is always $zero.$