A gas expands against a constant external pressure of 1.7 bar until its volume has increased from 5.4 L to 8.9 L. During this process it absorbs 640.0 J of heat from the surroundings. Calculate the energy change of the gas.

Answer 1

delta U = Heat in - Work out = Q - (P*delta V)
= 640 - 1.7*101.3*10^5 N/m^2*3.5*10^-3 m^3
= ? Joules

It looks like it will be a negative number