MHS AP Chemistry
Molecular Weight Of Bunsen Burner Gas
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
Discuss with your lab partner(s) what information you would need to
determine the molecular weight of burner gas. How could you measure
Procedure: Mass of A Gas
What to Pass In
OK, now get this information, and determine the molecular weight of burner
Decide whether the burner gas is most likely CH4, C2H6,
or C3H8. Explain the basis for your decision.
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
For this lab you will pass in a LEGIBLE sheet of paper with the following:
[Syllabus 10][MHS AP Chem page]
A heading that includes your name, your partnerís name, the date, and the
title of the lab.
A data table that includes every measured quantity. Remember that
every value should be described in English AND labeled with the proper
units (for example, Mass of Cheeseburger 118.2 g )
A calculations/results section that describes and clearly shows every calculation.
Make sure I know what you are thinking.
A decision about which formula most likely applies to the burner gas.
A decision about which combination of gases is most likely.
A discussion that includes any opinion about the lab or results, any possible
errors, and any suggestions for getting better results.