i had a lab that combined

1/2 cup of H2O2 (118.3 ml)
and 2 tsp of yeast.

is the equation for the reaction
2H2O --> 2H2O + O2

what would the mass be for each product
in the reation? Is the density of
H2O2 1.4g/ml?

Here is some interesting reading on this subject. As to the mass of each product, simply use regular stoichiometric procedures. The density of H2O2 depends upon the concentration.
For a more indepth discussion, read more than just the first response.
http://www.newton.dep.anl.gov/askasci/gen01/gen01340.htm