A gas occupies 2 litre at S.T.P. It is provided 300 joule heat so that its becomes 2.5 litre at 1 atm. Calculate change in its internal energy.

Explanation

Given `V_(1)=2` litre, `V_(2)=2.5` litre, `q=+300 J, P_("external")=1` atm.
`therefore Delta E=q+W`
`W=-P_("extrnal")Delta V=-P_("external")(V_(2)-V_(1))=-1 atm xx (2.5-2)` litre = -0.5 litre atm.
`W=-0.5xx101.3 J=-50.65 J`
`therefore Delta E=q+W300+(-50.65)=249.35 J`