Sciencemadness Discussion Board

Molar Mass from BP Elevation

Hexavalent - 22-2-2012 at 14:52

I have recently decided to carry out an experiment in The Illustrated Guide to Home Chemistry Experiments by Robert Bruce Thompson, specifically lab 8:1.

Quick question - how does one determine the molar mass of a compound if you know its molality in solution, its measured boiling point and the boiling point of pure solvent?

For example, if I had 100ml of a solution of NaCl of 6M/kg, knew its boiling point and also knew the boiling point of pure water, how would I get to it's known Mr (58.44g/mol) or near about using a calculation?

Thanks
-Hexavalent

bahamuth - 22-2-2012 at 15:24

By god, first hit on Google after search phrase "molar mass boiling point", Determining Molar Mass From Boiling Point Elevation

Think you need a intricate glassware instrument for this, saw one at the university when I worked there, but it was useless w/out its short range ultra accurate thermometers.

The one I saw was similar as the last picture on this page, atleast IIRC the way it worked was precisely the same.