Question

A gas contained in a cylinder fitted with a frictionless piston expands against a constant pressure 1 atmosphere from a volume of 4 liter to a volume of 14 liter. In doing so, it absorbs 800J thermal energy from surroundings. The value of $\Delta U$ for the process is.

• A. -213.7 J
• B. 213.7 J
• C. 113.7 J
• D. -113.7 J

Answer 1

The correct option is B

213.7 J

The thermal energy absorbed by the system can be given as $q=800J$

The work done can be given as $w=-P\times \Delta V$

$w=-P\times \Delta V=-1\times 101.37\times {10}^3\times (14-4)\times {10}^{-3}=-1013.7J$

$\therefore w=-1013.7J$

Now here by applying the first law of thermodynamics we get:

$\Delta U=q+w=800-1013.7$

$\therefore \Delta U=-213.7J$