Name:
Lab #17: Fermentation (production of alcohol)
Introduction:
Fermentation is the biological process through which sugars react to create
cellular energy for plants, bacteria or fungi like yeast, while producing ethanol and
carbon dioxide as waste. The unbalanced reaction for ethanol fermentation is shown
below:
Equation 1: Ethanol Fermentation
__C6H12O6(s)  __C2H5OH(l) + __CO2(g)
glucose
ethanol carbon dioxide
Ethanol fermentation is what causes bread to rise, is used in the production of alcohol
beverages and is used for the production of ethanol for fuel. Ethanol is useful as a fuel
because when it combusts, it forms energy:
Equation 2: Ethanol Combustion
__C2H5OH(l) + __O2(g)  __CO2(g) + __ H2O(g) + ____________kJ energy
Pre-Lab Tasks:
1) Balance Equations 1 and 2
2) Use Table I to identify the quantity of energy emitted from the combustion of
1 mole of ethanol and write it in the blank space in Equation 2
Purpose: To ferment ethanol using yeast and experimentally confirm that the
expected products were formed.
Procedure:
Set up the following equipment and materials to use yeast for ethanol
fermentation, conducting the experiment in order of the numbers in the labels
below:
Observations:
OBSERVATIONS:
Glucose
Yeast
bromothymol blue
solution
Before experiment
flask with glucose and yeast inside
bromothymol blue
solution
contents remaining in flask 24 hrs later
bromothymol blue
solution
During Experiment
After Experiment
Research to be done On-Line or Using Class Texts/References:
1) Describe two chemical or physical properties of ethanol that you could use to
test if ethanol is present in the flask:
2) Explain what bromothymol blue can be used to indicate and how it could
inform your assessment of whether or not ethanol fermentation occurred:
Conclusions: What evidence do you have that ethanol fermentation occurred?