Extraction Sublimation Caffeine Worksheet PDF

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Extraction Sublimation Caffeine Worksheet...

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CH236: Extraction and Sublimation of Caffeine Names: Hannah Strickland, Mary Yant, Cierra Young! ! Date: 10/20/2016 OBJECTIVE (1 PT) In 1-3 sentences, what will you determine from the results of this experiment? This experiment will determine the amount of caffeine in an amount of tea leaves through the process of extraction and sublimation.

TECHNIQUES (2 PTS) Briefly describe the techniques used in this experiment. Extraction with organic solvents: What is extraction? Why is it used? How does the rule of thumb “like dissolves like” come into play in extraction? What equipment is used for this type of extraction? • Extraction: Extraction is a way to separate a substance from a mixture. Extraction is useful for separating liquid-liquid mixtures, typically ones that are immiscible. • “Like dissolves like” is important in extraction because you want to choose a solvent that has an opposite polarity than the solute. This will cause for an easier extraction process. • This type of liquid-liquid extraction will use suction filtration and a separators funnel apparatus. Sublimation and Deposition: Define each of these terms. What is the purpose of subliming caffeine in this experiment? • Sublimation: sublimation is when a substance goes directly from the solid to the gas phase, skipping the liquid phase • Deposition: deposition is when a substance goes directly from the gas phase to the solid phase, skipping the liquid phase • The purpose of subliming caffeine in this experiment is to remove the pure caffeine from the crude caffeine, thus removing any impurities that could be in the caffeine EQUIPMENT AND MATERIALS (1 PT)

CH236: Extraction and Sublimation of Caffeine Names: Hannah Strickland, Mary Yant, Cierra Young! ! Date: 10/20/2016 List all equipment (including size of glassware) and reagents used in this experiment. Extraction: • 100 mL beaker • Hot plate • Large beaker • Suction filtration apparatus • Ring stand with clamp • 125 mL separatory funnel • 25 mL Erlenmyer flask • Tea leaves • H2 O • Na2CO3 • NaCl • CH2Cl2 • Na2SO4 Sublimation: • Thermometer • Sand bath • 2 140 mL beakers • 25 mL suction Erlenmyer flask • 2 pipets • 9800 size test tube • Metal scoop • Rubber bulb • Mel-Temp apparatus • Parafilm • Watch Glass • Rubber filter adapter • Clamps • Ring stand • H2 O • C8H10N4O2 DATA/RESULTS (5 PTS)

CH236: Extraction and Sublimation of Caffeine Names: Hannah Strickland, Mary Yant, Cierra Young! ! Date: 10/20/2016 Fill in the blanks using the data from your lab notebook. Include units where appropriate. Extraction: -

Initial mass of tea leaves: 7.03 g

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Mass of empty side arm flask: 31.692 g

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Mass of side arm flask with crude caffeine: 31.773 g

- Mass of crude caffeine: 0.081 g Extraction (continued) Calculate the caffeine extraction yield (percent of caffeine in starting mass of tea leaves). SHOW ALL MATH. ! Is this a reasonable extraction yield? Why or why not? The extraction yield is reasonable because 74% of the caffeine was recovered, this means that the percent error was only 26%. Draw TLC plate of crude caffeine and caffeine standard. Include solvent front, distances with units, and label all spots. Did not perform Rf value of caffeine standard:_____________ How many spots are present on TLC from crude caffeine sample? _________ Can you identify one spot on crude sample TLC plate as caffeine? ___________ Sublimation -

Mass of crude caffeine: 0.081 g

- Mass of pure caffeine: 0.033 g Calculate the caffeine sublimation yield (percent of pure caffeine obtained from crude caffeine). SHOW ALL MATH. ! Is this a reasonable extraction yield? Why or why not? Since the percent recovered was 40.7% this means that the percent error would be 59.3%. The percent recovered is fairly small. This could be due to a number of errors that occurred during the course of the experiment. QUESTIONS (FROM HILL & BARBARO, T5-11, Q1-4 & E4-4, Q1-4) (6 PTS)

CH236: Extraction and Sublimation of Caffeine Names: Hannah Strickland, Mary Yant, Cierra Young! ! Date: 10/20/2016 Answer the following questions on your own paper and attach to this worksheet. T5-1. You are given a substance that is equally soluble in water and hexane (two immiscible solvents). a) What is the KD? ! b) If you start with 10 g of the substance dissolved in 100 mL of water and are given 100 mL of hexane to extract with, algebraically show that it is better to do two smaller extractions using 50 mL of hexane for each extraction than one it is to do one extraction using 100 mL of hexane. SHOW ALL MATH.

! Since the K value is between 1 and 10 then it would be best to do two smaller extractions with 50 mL of hexane because with two extractions it gives you a higher amount of grams, 5.55, rather than just 5 grams.

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CH236: Extraction and Sublimation of Caffeine Names: Hannah Strickland, Mary Yant, Cierra Young! ! Date: 10/20/2016 T5-2. You have a solution that contains 4.0 g of oxalic acid dissolved in 100 mL of water. This solution is placed in a separatory funnel, and then 100 mL of diethyl ether is added to the separatory funnel and an extraction is performed. (Diethyl ether and water are immiscible solvents.) Use the following constants to calculate how much oxalic acid is in each solvent after the extraction. -

Solubility of oxalic acid in water = 9.5 g / 100 mL

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Solubility of oxalic acid in diethyl ether = 16.9 g / mL

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y = 0.37: water: 0.36 x 4 g = 1.44 g in water layer

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x = 1 - 0.36 = 0.64: diethyl ether: 0.64 x 4 g = 2.56 g in diethyl ether layer

CH236: Extraction and Sublimation of Caffeine Names: Hannah Strickland, Mary Yant, Cierra Young! ! Date: 10/20/2016 T5-3. Briefly describe how you can tell which layer is the aqueous phase after performing an extraction. The aqueous phase will dissolve in water because they are both polar. Densities could also be compared. The layer with the density closest to water would be the aquas phase. T5-4. Could you use methanol instead of methylene chloride to do a liquid-liquid extraction of an aqueous solution? Briefly explain why or why not. You could not use methanol because methanol is polar and water is polar, therefore the two substances would mix well and it would be difficult to separate them with the method of extraction because they would not separate into layers. E4-1. Why was sodium chloride added to the tea solution before extracting with ethyl acetate? Sodium chloride is added to the tea solution before extracting because it prevents emulsions and allows for a better separation of the mixture. E4-2. Could you have used ethanol instead of ethyl acetate to extract the caffeine? Why or why not? Ethanol could not be used because it is not miscible with water. E4-3. What is the purpose of adding calcium carbonate to the flask in the brewing step? The acids, tannic and gallic, form in the tea solution and calcium carbonate is added because it is a base. This addition of calcium carbonate allows the acids to bond to it which makes them easier to remove, thus easier to remove impurities and obtain a pure form of caffeine. E4-4. At 25 °C, 1.0 g of caffeine will dissolve in 47 mL of water, in 8.1 mL of chloroform, in 86 mL of benzene or in 370 mL of diethyl ether. Calculate in the solubility (in g / 100 mL) of caffeine in these four solvents. Calculate the partition coefficient between water and each of the other three solvents. Which of these three organic solvents would be the best choice for extracting caffeine from an aqueous solution?

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Partition coefficient:

CH236: Extraction and Sublimation of Caffeine Names: Hannah Strickland, Mary Yant, Cierra Young! ! Date: 10/20/2016

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! Chloroform would be the best choice for extracting caffeine in an aqueous solution of water because the partition coefficient is the highest, which is 12....