In step one, I apply the formula for a change in entropy. That is, change in entropy surroundings is equal to change in energy over temperature, as seen here. Step two remember when we talk about free energy, or gifts free energy, we talk about a closed system, constant pressure and constant temperature. And what this basically means, according to the ideal gas law, is that volume is constant. So change in volume is zero. So the PV work done is zero.