Module 6 Week 2 - Group Worksheet (1)

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M ODULE 6 W EEK 2 - S OAP AND B IODIESEL G ROUP W ORKSHEET (20 POINTS ) W EEK 2 G ROUP A SSIGNMENT The background for this module is in Module 6 Week 2 Overview page. Please refer to that page for context. S AFETY 1. For each substance listed in questions 3, 10, and 12, look up the relevant safety information ( https://chemicalsafety.com/sds-search/ ), and complete the table below. (2 pts) Chemical name (not formula) Flammable? Reactive? Health Hazard? First Aid Measures Needed protective equipment [ arachidic acid ] Skin and eye irritation If gets on hands or eyes wash thoroughly, if pain persists get medical attention Goggles and gloves [sodium hydroxide ] May be corrosive to metals and may cause respiratory irritation. Corrosive to metals and skin. If swallowed, rinse your mouth and do not induce vomiting. If on clothes, remove all contaminated clothing and wash before reuse. Wear protective goggles, gloves, and clothing. [ sulfuric acid ] Skin Corrosion Wash thoroughly after handling, if in eyes or on skin wash thoroughly, if inhaled go to fresh air Wear protective goggles gloves and clothing [ carboxylic acid ] Highly flammable liquid and vapor. If it is on skin or hair remove contaminated clothing immediately and wash skin (shower). Wear protective gloves/protective clothing/eye protection/face protection 2. After watching the videos below, come back to this question and consider what kinds of procedural hazards you will encounter when you do this activity live (hot glass, containers which could spill, glass which could be dropped and shatter, etc.). For each possible hazard, identify ways that the risk could be minimized. You should add

additional rows to the table if needed. (1 pt) Procedural Hazard What could go wrong? If it does go wrong? What should you do? What can you do to proactively prevent this from happening? Glass stirring rod If the glass stirring rod is left in the beaker, it has a higher possibility of tipping over and then the chemicals could spill. When using the stirring rod, make sure to take it out before proceeding so it doesn’t tip over. Bunsen Burner Could burn someone or something if it isn’t used properly/carefully. Do not leave anything on or around the burner without watching over it. Do not touch the beaker on the burner with gloves or safety ware. S OAP Soap is the sodium or potassium salt of an organic acid. An organic acid has an alkyl group (R) attached to a carboxylic acid group (COOH). The carboxyl group can vary widely to form different acids. Figure 1 below, is an example of arachidic acid (R-COOH) where R has 19 saturated carbons. Figure 1 : Three representations of arachidic acid. (source: Wikipedia, October 26, 2020) Soaps can be formed by reacting an organic acid with a base such as sodium hydroxide (NaOH). This reaction is similar to the reaction of an inorganic acid with a base, where the H of the acid is exchanged for the cation from the base to form a salt and water.

3. Write the balanced chemical equation for the reaction of arachidic acid (C 19 H 39 COOH or CH 3 (CH 2 ) 18 COOH) with sodium hydroxide to form a salt (a soap). (0.5 pts) [C 19 H 39 COOH+NaOH=C 19 H 39 COONa +H2O] For industrial production of acids, the primary source of acids is crude oil. Wanting a more environmentally friendly and readily available source of organic acids, many small scale producers of soap have turned to natural fats and oils. This method they use for making soap using triglycerides (oils and fats from plants and animals) is similar to the method that has been used for thousands of years as described in the overview module. Fats and oils have similar chemical properties. Watch this YouTube video (or this one ) about the chemical structure of triglycerides and answer the questions below: 4. What is triglyceride? Below is a drawing of the products of the saponification reaction which produces soap, the rightmost molecule in the equation. Draw the triglyceride reactant molecule which would react with NaOH to form these products. (1 pt) [ ] What non-alkane functional group(s) are present in your triglyceride drawing? (0.25 pt) Ester

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What non-alkane functional group(s) are present in the product molecules? (0.25 pt) Carboxylic acid, Alcohol 5. Consider the structure of soap below. This soap is based on the structure of linoleic acid. a. Circle the portion of the molecule that is water-soluble. Put a square around the portion of the soap that would be fat-soluble. (0.5 pts) b. Why is the circled portion water-soluble? What kind of intermolecular forces are involved? (0.5 pts) Polar Bonds, Dipole Dipole. This part is water soluble due to the hydrogen bonding present. c. Why is the portion you put a square around not soluble in water? What kind of intermolecular forces can it form with other molecules? (0.5 pts) Non polar, LDF. It is not soluble because there is no possible H bond. It is hard for interactions because they do not bond together properly. d. On the structure below, add in three water molecules and how they would interact or orient around the portion of the structure that you circled in part a. (0.5 pts) e. How will the strength of the intermolecular forces in part c change with (1) the length of the chain and (2) the presence of unsaturated bonds? (0.5 pts)

IMFs increase with molecular weight, unsaturated bonds means less IMFs 6. Watch this Youtube video that discusses how soap works and answer the questions below. a. When soap is added to water a micelle is formed. Draw a sketch of a crosssection of micelle in water using a circle with a stick to represent a soap molecule. Include in your drawing the names of the IMFs between the soap and water and the soap and soap molecules. (1 pt)-- b. Explain how soap acts as an emulsifying agent, allowing nonpolar substances to be dissolved in water. (0.5 pts). [a. IMFs between the soap and soap: LDF/IMFs between the soap and water: hydrogen bonding] [b. Soap acts as an emulsifying agent by the micelle forming around the nonpolar substance due to interaction between its hydrophilic head with water and hydrophobic tail with the nonpolar substance. The hydrophilic head reacts with the water to then capture the nonpolar substance and repel it out of water.] c. Below are representations of a lipid bilayer. Discuss one similarity and one difference between these structures below and the formation of soap micelle in water. (1 pt) Source: Science, 2019, 6(4): 509-548. doi: 10.3934/matersci.2019.4.509

[Similarity: they both hydrophilic heads Difference: the interactions are different. The lipid bilayer and the hydrophobic tails interact instead of the bilayer interacting with the nonpolar molecules. 7. Fats and oil are a convenient source of organic acids . However, they provide a mixture of acids. Examine the table on the Week 2 overview page. The table gives the percentage composition for a number of fats and oils (listed in the 1st column). In the heading row, you are given the acid present, the number of carbons in the acid, and the number of unsaturated bonds. For example, palmitic acid has 16 carbons and no double bonds. (C16:0). Linoleic acid has 18 carbons and 2 double bonds (C18:2). Consider capric acid and linoleic acid. (Hint: You may watch this or this video for more on triglycerides). a. How would the density of soap produced from a linoleic acid differ from the property of the oil that contains linoleic acid? First, list the (a) chemical differences (functional groups and packing of backbones) between a soap and linoleic acid and then list (b) any physical differences (density, freezing point, boiling point, viscosity) between the two. (0.5 pts) a. The density of soap produced from a linoleic acid differs from the property of the oil that contains linoleic acid because the density of the soap would increase while the oil would decrease. The soap has stronger IMFs due to the difference in functional groups and size causing the density to increase. The soap has the carboxylate acid functional groups due to the ions which causes it to ignore the water and have stronger IMFs between itself. The oil has weaker IMFs due to different groups and properties causing the dentistry to decrease. It also has the ester functional group and alkaline long carbon chains which do not stack well making the IMFs in oil weak because they are all repelled. b. Melting/freezing point: 1. Linoleic acid : 23 degrees F 2. Soap : 120-145 degrees F Boiling Point: 1. Linoleic acid : 230 degrees C 2. Soap : 1000 degrees C Viscosity: 1. Linoleic acid: viscous / movable 2. Soap : not viscous / movable b. How would the chemical and physical properties of a soap made from capric acid differ from a soap made from linoleic acid? (0.5 pts) London dispersion forces are higher in capric acid soap molecules than in linoleic acid soap

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molecules. This is due to the longer, more linear structure of capric acid molecules, which enables them to come together more firmly. Compared to linoleic acid soap, capric acid soap has a higher melting point and a stronger consistency due to stronger London dispersion forces. Because the fatty acid chain of linoleic acid soap has a hydroxyl group (-OH), it can establish hydrogen bonds with other molecules. Still, it is challenging for the hydroxyl groups on various molecules to align closely enough to generate hydrogen bonds due to the kink in the linoleic acid molecule. As a result, linoleic acid soap has a lower melting point than capric acid soap and weaker hydrogen bonding. 8. After answering questions 4 -7, give two reasons why soaps are more soluble in water than their starting triglyceride building block. (0.5 pts) One reason why soaps are more soluble in water is because they are more polar. Since triglycerides contain an even distribution of electrons, they are nonpolar molecules. They become insoluble in water as a result. Conversely, soaps are polar compounds. Because of the charged functional group's ability to attract water molecules, soap molecules become soluble in water. The second reason is that soap can form hydrogen bonds with water molecules. Soap molecules have hydrogen atoms bonded to oxygen atoms in their carboxylate groups. This makes them capable of forming hydrogen bonds with water molecules. The starting triglyceride building block is not soluble in water because the sodium is not present and triglycerides are nonpolar chains which are insoluble. 9. List at least two desirable attributes for a soap. (0.5 pt) One desirable attribute of soap is that it has a nonpolar tail and a polar head which allows it to interact with nonpolar and polar parts of a molecule. Soap also has hydrophobic and hydrophilic structures which makes the soap interact with water and surfaces.The soap is also hard and lather. 10. Watch the videos at https://youtu.be/m3VPNo8yJfA and https://youtu.be/VmQV3Qs9Qzk . Using these videos and the balanced equation from Question 2, what is this type of organic mechanism reaction called? (0.25 pts) Saponification 11. The side product formed in the synthesis of soap is a common ingredient found in commercial soaps. What is the name of the side product formed? How does the presence of this molecule contribute to the desirable attributes of soap that you listed in question 9? (0.5 pts)

The side product formed during the synthesis of soap is glycerol. The glycerol reacts with the water to keep the moisture of the soap in the body and prevent any damage. 12. Watch this video on the cleaning capacity of soap. Use scientific argumentation (Claim- Evidence-Reasoning) to discuss the effects of non-soap solutes in water on the ability of a soap solution to produce suds and to form micelles? (1.25 pts) Claim : Adding non soap molecules into the water will decrease the ability of soap to produce suds. Evidence : In the video 3 beakers are used, one with 20 mL of DI water, 20 mL of well water, and 20 mL DI water with 2g of CaCl. When adding 1g of soap into the 20 mL of DI water and 20 mL of well water soap dissolved completely, for the 20 mL DI water with 2g of CaCl the soap precipitate formed. When placing the solution in test tubes to measure the height of the solutionThe solution with DI water had the most suds, well water had slightly less and the CaCL tube produced the least When testing with ink DI water ink spot is almost gone, Well water is slightly gone, and CaCl beaker barley removed any ink once again.It is clear that molecules in the water have an effect on the ability of a soap to do its job. Reasoning : As is well known, soap functions by having both hydrophilic and hydrophobic properties. It is possible that the molecules interacting with the soap cause the molecule's hydrophilic/phobic characteristics to be disrupted, preventing it from functioning. That being stated, the hydrophilic head of the soap molecule will interact with the ions in the contaminated water as well as water itself, whereas the non-soap solutes would typically interact with the hydrophobic tail of the soap molecule. These interactions will limit the number of micelles that can form, forming a "barrier" between the soap and the water, disrupting the IMFs that are trying to form and, in the end, decreasing the soap's ability to make suds. B IODIESEL Watch the following video before answering the questions:

https://www.youtube.com/watch?v=sSLulgJ-E00&feature=emb_logo 13. From the video, name two reactants necessary to perform the process of transesterification. What is the main product of this reaction? Please list types of molecules and not specific compounds (example: “acid” not “hydrochloric acid”). (1 point) Reactants: Triglyceride and Alcohol Main product: Biodiesel 14. Biodiesel methyl esters have very low solubility in water. Draw a biodiesel molecule (0.5pts) and list all possible intermolecular forces that can be developed between biofuel molecules. (0.5pts) Use the triglyceride from question 4 (triglyceride made with one glycerol backbone and three 10-carbon side chains) and methyl alcohol to construct your biodiesel molecule. Why does the type of IMFs present in biodiesel explain that biodiesels have very low solubility in water? (0.5pts) [All the possible intermolecular forces: london dispersion forces and dipole dipole a little at the end of the molecule where ester functional group is] [Biodiesel molecules are nonpolar and mostly have london dispersion forces while water molecules are polar and have strong hydrogen bonding so its more favorable for water to keep hydrogen bonding with itself than it is for water to break that strong IMF and then make london dispersion or dipole induced dipole with a biodiesel. Non-polar molecules and polar molecules do not interact well with each other and the weaker the IMF the less soluble it is. So biodiesel is insoluble in water.]

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15. Using the following density values ● methanol 0.79 g cm −3 ● vegetable oil (triglyceride) 0.919~0.925 g cm −3 ● glycerol (1.261 g cm −3 ) ● biodiesel (fatty acid methyl ester) (0.85~0.90 g cm −3 ) a. Identify all four substances in Figure 1. (0.5 pts) [methanol 0.79 g cm −3 ] [biodiesel (fatty acid methyl ester) (0.85~0.90 g cm −3 )] [vegetable oil (triglyceride) 0.919~0.925 g cm −3 ] [glycerol (1.261 g cm −3 )] Figure 1 . Photograph of transesterification (A) before reaction and (B) after reaction. b. Why does glycerol have higher density than biodiesel? (0.5 pts) You must identify the strongest IMF present in glycerol and can refer to the biodiesel IMFs information you have already provided in question 14. [ Glycerol has a higher density than biodiesel because it has stronger IMFs. The strongest IMF present in glycerol is hydrogen bonding. ] 16. Figure 2 (below) presents the transesterification reaction mixture observed at 10 min of running time with the addition of 0, 0.3, 0.5, 0.6, 0.8, and 1.0 % of sodium hydroxide.

Figure 2 . Effect of NaOH amount in transesterification mixture (from left to right: 0, 0.3, 0.5, 0.6, 0.8, 1.0 wt %). a. The formation of glycerol indicates that the reaction is happening. Is the addition of sodium hydroxide necessary for biodiesel synthesis? If so, what minimum amount (weight %) do you need to form the highest yield of glycerol? (0.5 points) [ The addition of sodium hydroxide is necessary for biodiesel synthesis. The minimum amount of sodium hydroxide needed to form the highest yield of glycerol is 3 weight % ] b. What is the role of the catalyst? You will likely have to do some googling to answer this. You can do this in less than 10 words, so please don’t write a paragraph. (0.5 points) [ The role of the catalyst in biodiesel synthesis is to speed up the chemical reaction that converts triglycerides (oils and fats) into biodiesel and glycerol. ] c. Propose another catalyst for the reaction of transesterification. (0.5 pts) [ potassium methoxide ( KOCH3) ] 17. Watch the following video: https://www.youtube.com/watch?v=G7CkMkD2z4c&feature=emb_logo a. What is the cause of soap formation during biodiesel production? (0.5 points) [The cause of soap formation during biodiesel production reaction of free fatty acids with the alkaline catalyst ] b. What is the highest acceptable concentration of soap in biodiesel produced with NaOH as a catalyst? (0.25 points)

[41 ppm] c. How do we separate soap from biodiesel? Use your knowledge about IMFs between soap/water and biodiesel/water molecules to explain why that method is effective. (0.75 pts) [Due to the varying IMFs between the molecules of soap and water and those of biodiesel and water, water washing and ion exchange are efficient ways to separate the two. Biodiesel is a nonpolar molecule that is insoluble in water, whereas soap is a polar substance that dissolves in it. These variations in IMFs are used by ion exchange and water washing to separate the soap from the biodiesel.]

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