The normal boiling point and H _ vap of a liquid ' X ' are 400 K and 40 ~kJ ~mol ⁻¹ respectively. Assuming H _ vap to be constant, which of the following is correct? I. S _ vap >100 ~J ~K ⁻¹ ~mol ⁻¹ at 400 K and 0.5 atm II. S _ vap < 100 ~J ~K ⁻¹ ~mol ⁻¹ at 400 K and 1 atm III. S _ vap < 100 ~J ~K ⁻¹ ~mol ⁻¹ at 400 K and 2 atm IV. S _ vap =100 ~kJ ~K ⁻¹ ~mol ⁻¹ at 400 K and 1 atm