If a gas absorbs `200J` of heat and expands by `500 cm^(3)` against a constant pressure of `2 xx 10^(5) N m^(-2)`, then the change in internal energy is

Options

A. `-300` J
B. `-100` J
C. `+100` J
D. `+300 J`

Answer

C

Explanation

`DeltaE = q+W, q=+200 J`
`W=-PDeltaV = -2 xx 10^(5) Nm^(-2) xx 500 cm^(3) xx ((1M)/(100 cm))^(3)`
`=-2 xx 10^(-5) xx 500 xx 10^(-5) Nm^(-2) xx m^(3)`
`=-100 Nm = -100 J`
`DeltaG = 200-100=+100 J`