Question

Here is the question:

A sample of an unknown volatile liquid was injected into a Dumas flask (mflask=27.0928g. Vflask=.104L) and heated until no visible traces of the liquid could be found. The flask and its contents were then rapidly cooled and reweighed (mflask+vapor=27.4593g) The atmospheric pressure and temperature during the experiment were 0.976 atm and 18.0 °C, respectively. The unknown volatile liquid's molecular mass was __________.

I have not got any concrete homework done on this outside of guessing and checking can someone set up this equation for me or explain how this can be done?

Answer 1

Use n = PV/RT to get the number of moles in sample used.

Divide the grams of sample used by the number of moles to get the grams/mole which is the same as the molar mass. That is numerically the same as the molar mass.

Answer 2

Thank you that was exactly what I was looking for.