Chem 142 Lab 5

Molar Mass of a Low Boiling Liquid

Full setup for labThe objective of this experiment is to determine the identity of a compound that boils at a low temperature. The compounds chosen as unknowns change from the liquid state to a gas at fairly low temperatures, so we can use a simple water bath to heat the sample in a gas density flask and apply the ideal gas law:




You will determine the pressure, volume, and temperature of the sample at the moment you cap the flask and can use those values in the gas law to calculate the moles of gas in the flask.  After determining the mass of your sample, you will then combine the mass and number of moles to calculate the molar mass of your sample (MM = g/mol) and identify the unknown from a list of possible compounds.


  • Prelab
    • Intro (pdf 120 KB, rev 5/2/13)
    • Required Prelab Assignment in Canvas (due Tuesday 8/13 at 12:30 pm)
    • Review Materials & Procedure
    • Review Demonstration



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