Question

25 mL of methylene chloride is spilled in a room measuring 15 ft x 12 ft x 10 ft. Assuming that the solvent completely evaporates and fills the space, what is the resulting concentration of methylene chloride in units of mg/m3 and ppm? Is this a hazardous environment? Assume NTP (1 atm, 25o C).

Answer 1

Volume of methylene chloride in the room

= 15*12*10 = 1800 ft3 x 0.0283 m3/ft3 = 50.94 m3

From the ideal gas equation

Moles of methylene chloride = PV/RT

= 1 atm x 0.025 L / 0.0821 x 273K

= 0.001115 mol

Mass of methylene chloride = 0.001115 mol x 84.93 g/mol

= 0.09469 g x 1000mg/1g = 94.69 mg

concentration of methylene chloride

= 94.69 mg/ 50.94 m3

= 1.858 mg/m3

At NTP

V = 0.0821*273/1 = 22.41 L/mol

Concentration in ppm

= concentration in mg/m3 x 22.41 / molecular weight

= 1.858 x 22.41 / 84.93

= 0.49 = 0.5 ppm

PEL limits of methylene chloride = 25 ppm

This is a safe environment