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 A diagram shows a flask of boiling water on a hot surface. A Dumas bulb filled with a vaporized unknown substance is immersed in the boiling water.). 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.

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