Grade 12 Chemistry
Name: _____________________________
Inquiry: ______ / 30
Communication: ______ / 10
Lab: Making and Testing Soap
Purpose: to produce soap from the saponification of corn oil, and to test its properties compared to
those of commercial soap.
O
CH2 – O – C – (CH2)14CH3
CH2 - OH
O
O
CH – O – C – (CH2)14CH3 + 3NaOH 
CH2 – OH
+ 3CH3(CH2)14 – C – O - Na+
O
CH2 – O – C – (CH2)14CH3
CH2 – OH
lard
sodium hydroxide
glycerol
a crude soap
Materials: List all the equipment and chemicals you used in the lab. You must wear safety glasses
throughout the lab. Make the list as you go along. Include labeled diagrams of the reaction set up and
the filtration apparatus to avoid long lists of all the separate components. (4 marks)
Safety: Sodium hydroxide pellets are extremely corrosive to eyes and skin. Ethanol is flammable – it
should not be used near an open flame or other ignition source.
Method:
Part 1 – Making Soap
1) Use soluble pens to label a 100 mL beaker with the letter “A”, a 250 mL beaker with the letter “B”
and a second 100 mL beaker with the letter “C”.
2) Measure about 10 mL of water into beaker A using a graduated cylinder.
3) Tare a small piece of scrap paper on a balance. Use a scoopula to find the mass of 18 pellets of
sodium hydroxide. Work quickly, as sodium hydroxide absorbs water from the air quite readily.
Record the mass and describe the NaOH in the observations.
4) Add the NaOH pellets to the water in beaker A and stir with a glass rod until they dissolve. The
solution will get very hot. Set the beaker aside to cool.
5) Tare beaker B on the balance, and measure in 15 g of lard. Record the mass and describe the lard in
the observations. Use a graduated cylinder to add about 15 mL of ethanol to the oil.
6) Put beaker B, supported by a ring clamp on a retort stand, on a hot plate. Clamp a thermometer
(using a thermometer clamp) to the retort stand and immerse it in the mixture. Warm the mixture
gently, constantly stirring with a glass rod, until the lard is thoroughly melted. Allow to cool.
6) Add the contents of beaker A to beaker B. Make observations.
7) Heat beaker B very gently for about 20 minutes, while stirring with a glass rod. Keep the
temperature between 40 °C and 45 °C. If the mixture gets too hot, take it off the hot plate to cool down
(you will have to unclamp the thermometer to do this).
8) While heating, measure 4 g of sodium chloride into beaker C. Add about 20 mL of water, and
dissolve. Also measure out about 10 mL of vinegar using a graduated cylinder.
9) Remove the beaker from the hot plate and place it on a ceramic pad to cool down. You may have to
use beaker tongs to do this. Add a few drops of food colouring at this stage to “colour” your soap.
10) Add the contents of beaker C to beaker B. Stir, and make observations.
11) Add 10 mL of vinegar to the beaker. Stir, and then allow the solid to settle somewhat.
12) Carefully pour off any excess liquid down the sink. Then wash any excess vinegar off the soap
with about 10 mL of water. Once again, carefully pour off excess liquid down the sink.
13) Record the mass of a dry piece of filter paper in the observations. Flute the filter paper, place it in a
funnel, and then wet the paper so it sticks to the funnel. Filter the soap mixture into a 250 mL
Erlenmeyer flask. Take care not to puncture the filter paper.
14) Add a few drops of perfume at this point, if you care to.
15) Carefully transfer the filter paper and soap to a piece of paper towel, and allow it to dry overnight.
The next day, make observations of the dry soap, and record the mass of the filter paper and the soap in
your observations. It is also possible to mold the soap into a specific shape at this stage.
Part 2 – Testing the Prepared Soap
Compare your prepared soap to the commercial soap in the following ways:
-texture
-pH (use a wet stirring rod to transfer some soap suds to a piece of pH paper on a watch glass)
-effectiveness of lathering
Observations: Use a chart to record quantitative observations. Be sure to include units in the headings
only, and to write all numerical values using the correct number of significant digits. Qualitative
observations can be included in the chart, or can be written in full sentences after the chart. (9 marks)
Analysis:
Show all units and chemicals used in your calculations, all steps of your work, including formulas. Be
careful to carry at least four digits throughout all the calculations. Paraphrase your answer with the
correct number of significant digits for full marks.
1a) Calculate which reactant is the limiting reagent. (4 marks)
b) Use the limiting reagent to calculate the theoretical yield of your soap.
c) Calculate the % yield of your prepared soap. (2 marks)
(3 marks)
2) There are probably some differences between the commercial soap and your prepared soap. Suggest
some specific reasons for this. (2 marks)
3) Do you think soap molecules are polar or non-polar? How would this affect their ability to remove
oils from greasy surfaces? (2 marks)
Conclusion:
Summarize the results of your experiment. (2 marks)
Suggest at least two major sources of error that affected the % yield of the prepared soap.
(2 marks)