Question

A gas present in a cylinder fitted with a frictionless piston expands against a constant pressure of 1 atm from a volume of 4 litres to a volume of 14 litres. In doing so, 800 J of heat is absorbed from surroundings. Determine change in internal energy of the process.

• A. - 213 J
• B. 213 J
• C. 1813 J
• D. -1813 J

Answer 1

The correct option is A - 213 J

$W=P\Delta V=P(V_2-V_1)$
$=(14-4)=10\text{litre atm}=1013J$
As 1 latm = 101.3 J
Since the gas expands, $W=-1013\text{J}$
$\therefore$ According to first law of Thermodynamics
$\Delta E=q+W=800-1013$
$=-213\text{J}$