Question

$1\text{kg}$ of a gas does $20\text{kJ}$ of work and receives $16\text{kJ}$ of heat when it is expanded between two states. A second kind of expansion can be found between the initial and final state which requires a heat input of $9\text{kJ}$. The work done by the gas in the second expansion is

• A. $32\text{kJ}$
• B. $5\text{kJ}$
• C. $-4\text{kJ}$
• D. $13\text{kJ}$

Answer 1

The correct option is D $13\text{kJ}$

The change in the internal energy will remain the same, since the initial and final states are the same for both the processes.
So, $U=Q-W$
$16-20=9-W$
$W=13\text{kJ}$