Steam distillation - Worksheet PDF

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Answer the following to the best of your ability. The point values indicated next to each question should give you insight to the depth of your answer (long/short, fact/opinion, math, etc.). For all questions involving calculations, work must be showed for credit, an answer with no work will receive zero points. Please try and convert this document to a word document and write your responses immediately following the question, and back to a PDF for submission. (Use the guidelines as previously discussed in emails.) Part 1 True or False: 10 points 1. Steam distillation is for two miscible solvents. [2] FALSE 2. We can taste our product from today since it is an essential oil. [2] FALSE 3. Water enters the condenser from the top in this type of distillation. [2] FALSE 4. FTIR only works for liquids. [2] FALSE 5. We don’t have to use DI water today. [2] FALSE 6. Part 2 Method and Procedure: 28 points 7. What is the purpose of the background when using FTIR? [3] To find out that it is completely clean, there is no compound and to eliminate any contributions, we run a background spectrum once. 8. What is the purpose of the Hickman head in this experiment? [3] As the eugenol condenses with the steam that is being distilled, it comes down at the side of the Hickman head. And as liquid gets reserved up it is collected in the Hickman head, we can also open the side port on the Hickman head, using a pipet to remove the collected distillate. Hence, while assembling our glassware, we need to make sure that the side part of the Hickman head is accessible as it collects the distillate that we need to transfer to the centrifuge. A Hickman head can also handle small amounts and low boiling point. 9. How is our recovered product dried initially? [3] The recovered product is dried over anhydrous sodium sulfate. It pulls the moisture out of the methylene chloride. 10. How do we recover the oil from the water today? [3] We open the side port on the Hickman head, using a pipet, we remove the collected distillate. The liquid is cloudy because there is oil. We use methylene chloride as our solvent to extract the oil. Chlorinated solvents are more dense than water. So the oil will dissolve in the methylene chloride which will be the bottom layer. This helps us and makes it easier to isolate the oil from water. So we have two layers after using the vortex machine. We push a little air so there is no water and transfer the methylene chloride in the conical vial.

11. What is the purpose of today’s experiment? What is our goal? [4] The goal of our experiment is to isolate an oil that is eugenol using micro-scale method of distillation. We recovered oil from the clove buds and obtained an IR spectrum from the sample and compared it to the library spectrum. We also learn the method and technique of steam distillation. 10. Briefly explain the assembly of our distillation apparatus today. [4] We use a microscale glassware. We use the O ring and a cap to join each of the joints. We put the cap on and slide the O ring over the glass joint. We do the same with Hickman head as well. We attach the Hickman head to the jacketed conde nser. We join them together, but make sure the joints aren’t very tight that it cramps to O ring. We clamp it by the hot plate so its secure and we can also move it up and down. For round bottom, we use a stir bar. We use a round bottomed flask on an aluminum block on top of a hot plate. The round bottomed flask should be positioned in the center of the hot plate and placed over the large hole in the aluminum block. We clamp the thermometer straight just a little inside the hole but not touching the hot plate. We connect a tube to water tap and over the bar so it does not touch the bar. And the return piece of tubing over the bar and into the sink. The water flow should be very low which will prevent over pressuring. The apparatus should be slightly tilted towards the side port so the liquid collects. We can open the side port on the Hickman head, using a pipet to remove the collected distillate.

11. How do we characterize our product today? Describe the theory behind this instrument in brief. [4] FTIR Spectrometer. There is a zinc selenium diamond below the little window. We film the liquid across the surface. It shows the beam path of the sample thats being taken at the surface. We take a drop of our eugenol sample, enough to cover the little window. We cover the window and wait and observe the spectrum. We obtained an IR spectrum from the sample and compared it to the library spectrum.

12. What is the purpose of using methylene chloride and not a different organic solvent? [4] Chlorinated solvents are more dense than water. So the oil will dissolve in the methylene chloride which will be the bottom layer. This helps us and makes it easier to isolate the oil.

13. Theory and Analysis: 12 points 14. What is the difference between the total pressure expression in steam distillation versus simple/fractional distillation. [4] In simple and fractional distillation of miscible liquids, the total pressure is equal to the sum of partial pressure of the two miscible liquids; cyclohexane and toluene. The partial pressure of cyclohexane is due to the vapor pressure pure cyclohexane times the mole fraction of cyclohexane. In steam distillation, in immiscible liquids, the total pressure is equal to the vapor pressure of pure eugenol plus the vapor pressure of water. There is no mole fraction. 15. Explain why a hot plate is needed when evaporating a solvent. [4] Methylene chloride is very volatile. So using a hot plate would warm it enough to accelerate the vaporization rate. We blow air across the top which will help blow the methylene vapors. 16. What happens when something boils? Briefly describe the physical chemistry behind boiling. [4] Boiling occurs when a liquid turns into a vapor when heated to its specific boiling point. It is a physical change and so molecules are not chemically changed or altered. This change from a liquid phase to a gaseous phase occurs once the vapor pressure of that liquid is equal to that of atmospheric pressure exerted on the liquid....