LAB 10 - SYNTHESIS OF SOAP
- Page ID
- 506287
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The purpose of this experiment is to:
- Prepare soap via the saponification reaction.
- Observe the properties of soap.
INTRODUCTION
Soap, a salt of fatty acids, is the most common cleaning agent in modern society. Its rich history, dating back thousands of years, can be traced to ancient Babylon around 2800 BCE. This long-standing history underscores the enduring significance of soap in human civilization, connecting us to our ancestors, who also appreciated its cleansing properties.
Soap is a salt derived from a fatty acid. More specifically, it is a sodium or potassium salt of a long-chain carboxylic acid. Soaps exhibit a characteristic amphipathic or amphiphilic structure, which means they possess both hydrophilic (water-loving) and hydrophobic (water-repelling) components:
- The hydrophilic part (head) has an ionic charge and typically features a carboxylate group (carboxylate anion; -COO⁻), which is soluble in water.
- The hydrophobic part (tail) consists of a long hydrocarbon chain and is soluble in oil.
A long-chain soap molecule has an ionic carboxylate end (hydrophilic) that attracts water, while its long hydrocarbon part is nonpolar and hydrophobic. This structure enables soap to form micelles, which emulsify fats and oils for effective cleaning.
Soap molecules surround an oil droplet or grease with their nonpolar tails embedded in the oil and their charged “head” groups facing outward toward the water. If the oil droplets are small enough and there are sufficient soap molecules to cover them, they become dispersed in the water and can be easily washed away. Therefore, using plenty of soap, hot water, and agitation can help clean greasy dishes. Hot water dissolves solid fats, and agitation helps break them into smaller droplets.
Soap production is one of the oldest chemical reactions practiced by humans. It occurs through saponification, a process in which fats or oils (triglycerides) react with a strong base, typically sodium hydroxide (lye) or potassium hydroxide. This reaction produces glycerol and fatty acid salts (soap).
Saponification Reaction
The general equation for saponification is: typical Fat/Oil + Base → Glycerol + Soap.
More specifically:
Types of Soap
The choice of base and fatty acid influences the soap's properties:
• Sodium salts of fatty acids produce hard soaps
• Potassium salts yield soft soaps
• Common types of soap include sodium stearate, oleate, and linoleate.
• Saturated fatty acid salts produce rigid soaps, whereas polyunsaturated fatty acids lead to softer soaps.
The additional ingredients suggested below are often incorporated to enhance the properties of soap.
• Perfumes for scent
• Dyes for color
• Sand or Pumice in scouring soaps for abrasive action
• Air bubbles to create floating soaps
In this experiment, you will engage in the time-honored process of soap-making, testing, and comparative analysis with commercial soap and detergent. This comprehensive experiment will provide hands-on experience with soap chemistry, from production to performance evaluation, deepening your understanding of this essential cleaning agent.
Properties of Soap and Detergent:
- Amphipathic structure: one end is hydrophilic (water-loving) and the other is hydrophobic (water-repelling)
- Emulsifying ability: can mix oil and water
- Surfactant properties: reduces the surface tension of water
- Cleansing action: lifts dirt and oil from surfaces
- Lathering ability: forms foam in water
- pH: Typically, alkaline (pH > 7)
SAFETY PRECAUTIONS
1) Always wear chemical splash goggles, closed-toe shoes
2) You are encouraged to wear gloves while working on this experiment.
3) Work in a well-ventilated area or under the hood
4) Exercise caution when dispensing the 9.0 M NaOH. It is highly corrosive.
5) Never add water to NaOH; always add NaOH to water to avoid violent reactions.
6) If skin comes into contact with NaOH or other chemicals, rinse immediately with plenty of water for at least fifteen minutes and inform your instructor.
7) Dispose of all waste in the designated containers, as instructed by your instructor.
8) Thoroughly clean your workspace after finishing and return all equipment and chemicals to their proper locations.
EQUIPMENT AND CHEMICALS NEEDED
| EQUIPMENT | EQUIPMENT | EQUIPMENT | CHEMICALS | CHEMICALS |
|---|---|---|---|---|
| Safety equipment (goggles, gloves) | Stirring rod | Test tubes | Coconut oil (or other vegetable oil) | stearic acid |
| Thermometer | Beakers (250 mL, 100 mL) | Test tube rack | Sodium hydroxide (NaOH) | 0.5 M calcium chloride solution |
| Hot plate with stirrer | Mold for soap | Glass pipets and pipette bulbs | Distilled water | 0.5 M Iron (III) chloride solution |
| Magnetic stir bar | pH paper | 10 mL graduate cylinder | Assorted fragrances (optional) | 0.5 M Magnesium chloride solution |
EXPERIMENTAL PROCEDURE
A. Synthesis of Soap
1. Soap Synthesis: Measure out 10.0 mL of the provided oil using a 10.0 mL transfer pipette. Transfer 25.0 mL from a graduated cylinder into a 150.0 mL beaker. This is typically one of the following: olive oil, vegetable oil, or coconut oil.
2. Use the glass stirring rod to mix the ingredients. Pour 3.0 mL of 20% sodium hydroxide solution into the beaker. Stir for 20 to 45 minutes; you may alternate with your lab partner. The mixture will gradually become smoother and more opaque, eventually thickening to a pudding-like consistency.
3. After receiving approval from your instructor, add 2-3 drops of your preferred food coloring. Stir thoroughly.
4. Add a dash (about 1/8 teaspoon or the tip of a spatula) of stearic acid. This will help solidify the liquid soap. Stir it well. Pour the mixture into the selected mold shape. Clearly label it with your name and lab section number.
5. The process will continue after the soap is poured into the mold (small beaker). It will heat up and liquefy again, then cool slowly, harden, and dry. Therefore, the soap must remain undisturbed for at least 12 hours.
B. Properties of Soap and Comparative Analysis
a) pH Test:
- Dissolve a small amount of soap in water and test with pH paper.
- Compare with commercial soap and detergent, repeating the above step.
b) Foam Test:
- Shake a soap solution in a test tube and observe the formation of foam.
- Compare with commercial soap and detergent, repeating the above step.
c) Reaction with Oil:
- Add a drop of oil to water in one test tube and soap solution in another.
- Shake both and observe the difference in mixing.
- Compare with commercial soap and detergent, repeating the above steps.
d) Hard Water Test:
- Prepare a soap solution in distilled and hard water (containing Ca2+ or Mg2+ ions).
- Compare lather formation in both.
- Compare with commercial soap and detergent, repeating the above steps.
e) Emulsifying Properties:
- Mix equal parts of oil and water in a test tube.
- Add soap and shake vigorously.
- Observe the formation of an emulsion.
- Compare with commercial soap and detergent, repeating the above steps.
PRE-LAB QUESTIONS
Name ____________________________________
1. What are soaps? What is saponification?
2. What is the difference between soap and detergent? What determines whether the final soap product is solid or liquid?
3. Why is NaOH added to water and not vice versa?
4. Identify the primary safety hazard in this experiment.
5. Why is sodium chloride solution used after the reaction?
DATA AND OBSERVATIONS
Name _________________________Lab Partner(s) ______________________________
Part A: Synthesis of Soap
1. Identity of oil/ fat used:
2. Volume of oil/ fat used:
3. Volume of NaOH used:
4. Fragrance (if any) used:
5. Coloring (if any) used:
Describe the color, texture, and appearance of synthesized soap. Does it smell like any soap you've used?
Part B: Properties of Soaps and Detergents
Tests |
Soap |
Commercial Soap |
Commercial Detergent |
|---|---|---|---|
pH Test |
|||
Foam Test |
|||
Reaction with Oil |
|||
Hard Water Test |
|||
Emulsifying Properties |
POST-LAB QUESTIONS
1. What role does the amphipathic structure of soap play in its cleaning action? Why does soap produce less lather in hard water?
2. Write the complete ionic equation for the saponification reaction. In this chemical process used to synthesize soap, what is the ester, and what is the base? Which bases are commonly used for this reaction?
3. Describe what happens when soap can emulsify fats and oils. How does the emulsifying property of soap help in cleaning?
4. Suggest ways to modify this experiment to make different types of soap.
5. During the lab section, why did the saponification reaction require a long period of stirring? Why do we age the soap after it has been made?
6. Do you think the type of fat will make a difference in the product? Why or why not?
Please click here to access the Pre-Lab, Data Tables, and Post-Lab in Word or PDF format. Complete them and upload the lab report according to your instructor's instructions.
References:
1. https://saylordotorg.github.io/text_...-and-oils.html
2. 27.2 Soap - Organic Chemistry | OpenStax (https://openstax.org/books/organic-chemistry/pages/27-2-soap)
3. 6.3: Glycerolipids - Chemistry LibreTexts (https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Introduction_to_Organic_and_Biochemistry_(Malik)/06%3A_Lipids/6.03%3A_Glycerolipids)