A gas is allowed to expand in a well insulated container against a constant external pressure of `2.5 atm` from an initial volume of `2.50 L` to a final volume of `4.50 L`. The change in internal energy `Delta U` of the gas in joules will be:

Options

A. 1136.25J`
B. `-500J`
C. `-505J`
D. `+505J`

Answer

c

Explanation

`DeltaU =q+w`
For well insulated container, process is adiabatic , `q=0`
`:. DeltaU =w= - P DeltaV`
`= - 2.5 atm ( 4.5 - 2.5) L`
`=- 5L atm`
`= 5 xx 101.3 J = - 506.5 J `
`= -505J`