The vapor pressure of an organic solvent is 50 mm Hg at 25°C and 200 mm Hg at 45°C. The solvent is the only species in a closed flask at 35°C and is present in both liquid and vapor states. The volume of gas above the liquid is 150 mL. 

(a) Estimate the amount of the solvent (mol) contained in the gas phase. 

(b) What assumptions did you make? How would your answer change if the species dimerized (one molecule results from two molecules of the species combining)?