Question

Unit mass of a liquid with volume $V_1$ is completely changed into a gas of volume $V_2$ at a constant external pressure P and temperature T. If the latent heat of evaporation for the given mass is L, then the increase in the internal energy of the system is

• A. Zero
• B.
• C.
• D. L

Answer 1

The correct option is C

$△Q=△U+P△V\Rightarrow mL=△U+P(V_2-V_1)$

$\Rightarrow △U=L-P(V_2-V_1)$ $(\because m=1)$