MHS AP Chemistry
Molecular Weight Of Bunsen Burner Gas
Version 02

In this experiment we will determine the molecular weight of the gas used in our lab Bunsen burners.  We will do this by comparing the mass of a known volume of burner gas to the mass of an identical volume of air under the same conditions.

The molecular weight of air is the weighted average of the molecular weights of the gases that make up air.  Look up the composition of dry air.  Ignoring water, and gases present only in trace amounts, determine the molecular weight of dry air.

Look up and read Avogadro's Hypothesis.  Look up and read the definiation of "buoyancy."

Discuss with your lab partner(s) what information you would need to determine the molecular weight of burner gas.  How could you measure this information?

Procedure: Mass of A Gas

  1. OK, now get this information, and determine the molecular weight of burner gas.
  2. Decide whether the burner gas is most likely CH4, C2H6, or C3H8.  Explain the basis for your decision.
  3. The gas in the burner is actually a mixture of two of the gases listed above.  There are three possible pair combinations.  Given the calculated molecular weight, what is the percentage of each gas in each possible mixture?
What to Pass In
For this lab you will pass in a LEGIBLE sheet of paper with the following: [Syllabus 10][MHS AP Chem page]