Above a solvent’s flash point temperature, the vapor concentration in the headspace is sufficient  that a spark will initiate combustion; therefore, extreme care must be exercised to avoid ignition sources. Calculate the vapor phase mole fraction for the following liquid solvents using flash points listed, which were obtained from the manufacturer’s material safety data sheets (MSDS). The calculated vapor concentration is an estimate of the lower flammability limit (LFL). Assume that the headspace is an equilibrium mixture of air and solvent at 760 mmHg. The mole fraction of air dissolved in the liquid solvent is negligible for this calculation.

(a) Methane, -187.8°C

(b) Propane, -104.5°C

(c) Pentane, -48.9°C

(d) Hexane, -21.7°C

(e) Ethanol, 12.7°C

(f) 2-butanone, -5.6°C

(g) Toluene, 4.4°C

(h) M-xylene, 28.8°C

(i) Ethyl acetate, -4.5°C