A gas expands according to the equation pv=1000. where p is pressure in kPa and v is specific volume m^3/kg. If the gas pressure drops from 1000 to 500kPa, how much work was done by the gas??

Ok I am new to thermo and given a question and can't figure it out.

Do I use net flow work = p2v2-p1v1??

Answer is 693.1 kJ/kg.

or is it w-p delta v?

I am not sure.

Any help or direction would help thanks