The Ideal Gas Law: Molar Mass Video Lessons

Concept: Molar Mass

# Problem: The molar mass of a volatile substance was determined by the Dumas-bulb method. (In the Dumas-bulb technique for determining the molar mass of an unknown liquid, you vaporize the sample of a liquid that boils below 100oC in a boiling-water bath and determine the mass of vapor required to fill the bulb (see drawing ). The unknown vapor had a mass of 0.847 g, the volume of the bulb was 355 cm3, pressure was 753 torr, and temperature was 100 oC.Calculate the molar mass of the unknown vapor.

###### FREE Expert Solution

We are asked to calculate the molar mass of the unknown vapor.

Given:

m = 0.847 g

V = 355 cm= 0.355 L

P = 753 torr = 0.991 atm

T = 100 oC +273.15 = 373.15 K

R = 0.08206 L-atm/mol-K

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###### Problem Details

The molar mass of a volatile substance was determined by the Dumas-bulb method. (In the Dumas-bulb technique for determining the molar mass of an unknown liquid, you vaporize the sample of a liquid that boils below 100oC in a boiling-water bath and determine the mass of vapor required to fill the bulb (see drawing ). The unknown vapor had a mass of 0.847 g, the volume of the bulb was 355 cm3, pressure was 753 torr, and temperature was 100 oC.

Calculate the molar mass of the unknown vapor.