4 grams of a saturated liquid are converted to a saturated vapor by being heated in a weighted piston–cylinder device arranged to maintain the pressure at 200 kPa. During the phase conversion, the volume of the system increases by 1000 cm3, 5 kJ of heat are required, and the temperature of the substance stays constant at 80°C. Estimate the sfg of the substance when its temperature is 80°C.

Asteam is contained in a rigid tank with a volume of 1 m3. initially, the pressure and temperature are 7 bar and 500 oc, respectively. the temperature drops due to cooling process. determine: (1) the temperature at which condensation begins in °c, (2) the fraction of the total mass that has condensed when the pressure decreased to 0.5 bar. (3) the volume in m3 occupied by saturated liquid at the final state?