LAB 10: SYNTHESIS AND ANALYSIS OF SOAP
- Page ID
- 506031
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)PURPOSE
The purpose of this experiment is to
• Synthesize soap using the saponification reaction.
• Test the synthesized soap against a commercial liquid soap.
INTRODUCTION
We use soap daily when we shower, wash our hands, or clean various materials. It consists of a polar (hydrophilic) head and a nonpolar (hydrophobic) tail. When soap is used, oils and greasy dirt bond to the hydrophobic end, and rinsing with water washes everything away. Soap can be prepared through a process known as saponification. In this reaction, a triglyceride (or fat) reacts with a base, such as sodium or potassium hydroxide, to produce glycerol and the sodium or potassium salts of the acids.
Figure 1: Glycerol and sodium or potassium salts of the fat, known as crude soap. Image taken from General, Organic, and Biological Chemistry (Ball et. al) CC BY-NC-SA
In this experiment, you will first synthesize crude soap by reacting to an oil with sodium hydroxide. Then, the synthesized soap will undergo various tests, and the results will be compared with a commercial liquid soap.
SAFETY PRECAUTIONS
1) During this experiment, wear chemical splash goggles while working with chemicals.
2) Take care when handling hot equipment. Use hot mitts to remove equipment from the hot plate or ask your instructor to do so.
3) Do not test any soap products synthesized during this experiment on your body.
4) When you are finished with the experiment, clean your work area and dispose of waste as indicated by your instructor.
EQUIPMENT* AND CHEMICALS NEEDED
• 100 mL graduated cylinder
• Stirring rod
• Spatula
• Deionized water
• 50 mL beaker
• 250 mL beaker
• 400 mL beaker
• Hot plate
• pH paper
• Two medium-sized test tubes with rubber stoppers
• Hot mitts
• Cheesecloth
• Saturated sodium chloride solution
• Ethanol
• 3.0 M NaOH
• Vegetable oil, olive oil, and/or coconut oil (Note: Perhaps separate groups could be assigned different oils)
• Solid fat (such as vegetable shortening)
• Watch glass
• Commercial liquid soap
• Halogenated organic waste container
* Images of equipment needed in this lab can be found in the appendix (the equipment may differ a little or be subject to changes, follow your instructors’ directions).
EXPERIMENTAL PROCEDURE
1) Using a graduated cylinder, measure out 10.0 mL of vegetable oil, olive oil, or coconut oil. Pour the oil into a 250.0 mL beaker.
2) Add 10.0 mL of ethanol and 15.0 mL of 3.0 M NaOH to the 250. mL beaker. Stir the resulting mixture with a stirring rod for 2 minutes.
3) Gently heat the mixture on a hot plate, stirring occasionally for 20 minutes. If, after 20 minutes, more than one layer is still present in the beaker, continue to heat and stir until only one layer remains.
4) Using hot mitts, remove the beaker from the hot plate and allow it to cool on the bench top.
5) Once the mixture is cool, add 50. mL of saturated sodium chloride to 250. mL beaker. Continuously stir the mixture for 5 minutes. This will cause the soap to precipitate from the mixture.
6) Cover the beaker with cheesecloth and pour the mixture into a 400. mL beaker. The crude soap will remain in the original 250. mL beaker. Pour the contents of the 400. mL beaker into the halogenated organic waste container.
7) Using a spatula, add some of your soap to a 50 mL beaker and dissolve it in deionized water.
8) Pour your soap solution into a medium-sized test tube. Using pH paper, determine the pH of the soap.
9) Cover the test tube with a rubber stopper and vigorously shake it. Record the foaming test results in the data table.
10) Spread a solid fat (such as vegetable shortening) onto a watch glass. Then, wash this off with your soap solution and record the results. Clean and dry the watch glass and save it for step 14.
11) Dispose of your soap and solution into the halogenated organic waste container or as directed by your instructor.
12) Add 5 mL of commercial liquid soap and 5 mL of deionized water to a medium size test tube. Stir the mixture for 2 minutes. Using pH paper, determine the pH.
13) Cover the test tube with a rubber stopper and vigorously shake it. Record the foaming test results in the data table.
14) Spread a solid fat (such as vegetable shortening) onto a watch glass. Then, wash this off with the commercial soap solution and record the results.
15) Thoroughly clean your work area and return all glassware/equipment to the appropriate place when finished.
PRE-LAB QUESTIONS Name ____________________________________
1) In your own words, what is soap? How is soap used as a cleansing agent?
2) What organic functional group is present in a triglyceride?
3) Draw the structure of glycerol. What organic functional group is present in glycerol?
4) In your own words, describe what happens during the saponification reaction.
DATA AND OBSERVATIONS
Oil used in Soap Synthesis:
Write observations for each of the following steps in the synthesis of soap:
Step 2: Add 10 mL of ethanol and 15 mL of 3 M NaOH to the 250 mL beaker. Stir the resulting mixture with a stirring rod for 2 minutes.
Step 3: Gently heat the mixture on a hot plate, stirring occasionally for 20 minutes. If, after 20 minutes, more than one layer is still present in the beaker, continue to heat and stir until only one layer remains.
Step 5: Once the mixture is cool, add 50 mL of saturated sodium chloride to the 250 mL beaker. Continuously stir the mixture for 5 minutes. This will cause the soap to precipitate from the mixture.
Step 6: Cover the beaker with cheesecloth and pour the mixture into a 400 mL beaker. The crude soap will remain in the original 250 mL beaker.
Testing Synthesized Soap and Commercial Liquid Soap
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Test |
Synthesized soap |
Commercial soap |
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pH test (record pH) |
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Foam test (record observations)
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Cleaning of oil off watch glass (record observations)
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POST-LAB QUESTIONS
1) In the safety precautions section, it was advised not to use synthesized soap on your body. Explain why.
2) Briefly describe how your synthesized soap solution compares with the commercial soap solution regarding the pH, foaming, and cleaning ability.
3) If a different oil is used to synthesize the soap, would you expect the results of the pH test, foaming test, and cleansing test to be different?
4) In this experiment, you synthesized crude soap. What additional steps would need to be taken to commercialize the soap?