Answer Happy

A piston, initially completely filled with water vapor, compresses the gas until it is completely liquid (connecting the marked positions in Fig. 1). The piston is held at temperature T = 550K at all times. 2.0 x 108 1.5x 108 Pressure (dynes/cm2) 1.0 x 108 5.0 x 107 0 50 100 150 200 250 300 Volume per mole (cm^3) Fig. 1 Pressure vs. volume for the van der Waals model applied to one mole of H20 at T = 550K. The red line shows the vapor pressure P, at this temperature. (a) Draw the path on Fig. 1 taken if the piston moves slowly enough that the system remains in thermal equilibrium at all times. (b) Sketch a path on Fig. 1 taken if the piston moves fast enough so that the pressure rises past the vapor pressure (say, to 1.2 x 108 dynes/cm²) before a liquid water drop nucleates, but slowly enough so that the subsequent condensation of vapor into the water stays in equilibrium.