A gas present in a cylinder fitted with a frictionless pistion expands against a constant pressure of `1atm` form a volume of `2L` to a volume of `6L`. In doing so, it absorbs `800J` heat form the surroundings. Determine the increases in internal enegry of process.

Options

A. 698.7 J
B. 1205.2J
C. 394.8 J
D. 597.4 J

Answer

C

Explanation

Work is done against constant eternal force and thus process is irreversible.
Given `Delta V = (10-6) = 4 ` litres `=4 xx 10^(-3) m^3`
P= 1 atm `=1.013xx 10^5 Nm^(-2)`
`therefore W =- P xx Delta V =- 2.5 xx 1.013 xx 10^(5) xx 4 xx 10^(-3) =- 1013 J`
This work is used in heating 1 mole water.