Question

A laboratory group measures an excess of a volatile liquid. They add this to an empty flask with a volume of 29 mL. They heat the sample to 100.7 degrees Celcius until all the liquid is vaporized. The pressure in the lab is 0.987 atm. If 0.229 grams of volatile liquid were left in the flask, what was the molar mass of the compound? Record your answer to 2 decimal spaces.

Answer 1

Given data,

Temperature = 100.7 + 273

= 373.7 K

Pressure = 0.987 atm

Mass = 0.229 g

Volume = 29mL

= 0.029L

Let us consider a relation,

P V = n RT

0.987 x 0.029 = n x 0.0821 x 373.7

n = (0.987 x 0.029 )/ (0.0821 x 373.7)

= 0.0286 /  30.68

= 0.0009322 moles

Mass / Molar mass = No.of moles

0.229 / Molar mass = 0.0009322 moles

Molar mass = 0.229 / 0.0009322

= 245.65 g/mol