Question

Trichloroethane, C2H3Cl3, is the active ingredient in aerosols that claim to stain-proof men's ties. Trichloroethane has a vapor pressure of 100.0 mm Hg at 20.0 C and boils at 74.1 C. An uncovered cup (1/2 pint) of trichloroethane (d=1.325 g/mL) is kept in an 18-ft3 refrigerator at 39 F. What percentage (by mass) of trichloroethane is left as a liquid when equilibrium is established?

Answer 1

Use the Clausius-Claypeyron equation and solve for delta Hvap.(You know p at 20 and you know p is 760 mm at 74.1.) Then use CC equation a second time and one of the other values to solve for vapor pressure at 277 K (39F). Use PV = nRT and solve for n. Convert n to grams, convert the 1/2 pt to grams, and go from there to solve for percent. Note it is percent remaining, not percent evaporated.

Answer 2

I found the first 2 steps, but don't know what to do next. how do i find the volume to plug it into the equation: PV=nRT?