Laboratory Techniques in Organic Chemistry
4th Edition
ISBN: 9781464134227
Author: Jerry R. Mohrig, David Alberg, Gretchen Hofmeister, Paul F. Schatz, Christina Noring Hammond
Publisher: W. H. Freeman
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Chapter 10, Problem 5Q
Interpretation Introduction
Interpretation:
The amount of benzoic acid remaining in the water solution after extraction with four 20-mL ether should be determined and the same should be calculated using extraction with one 80-mL ether. Also the more efficient method should be determined.
Concept Introduction:
The formula used to determine the left amount after n extractions remaining in the original water solvent is:
Where
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A student recrystallized some impure benzoic acid and isolated it by filtration. He scraped the purified benzoic acid off the filter paper after it had dried and took the melting point as a test for purity. He was surprised that most of the white solid melted sharply between 121 and 122 0C but that a small amount remained unmelted even at temperatures above 200 0C. Explain this behavior.
A student recrystallized some impure benzoic acid and isolated it by filtration. He scraped the purified benzoic acid off the filter paper after it had dried and took the melting point as a test for purity. He was surprised that most of the white solid melted sharply between 121 and 122 °C but that a small amount remained unmelted even at temperatures above 200 °C. Explain this behavior.
Your employer hands you a heterogeneous mixture and asks you to isolate all of thehexane that you can from it. After some analysis, you determine that the mixture contains toluene, hexane,benzoic acid, water, sodium chloride, and sand. Explain how you would isolate pure hexane from thismixture. Remember that you can use techniques such as filtration, extractions, and acid/base chemistrythat we learned earlier in this course in addition to distillation. You may need to look up solubilities and/orboiling points online to solve this problem. You only need to isolate the hexane?
Chapter 10 Solutions
Laboratory Techniques in Organic Chemistry
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- In addition to a low boiling point and immiscibility with water, why is density important to consider in the selection of an extraction solvent? Would an organic liquid with a density of 1.006 g/mL make a good extraction solvent? Explain.Write the chemical reaction that took place during this experiment.arrow_forwardA compound has a distribution coefficient of 11 for a system of ether and water. 5.0 g of this compound is dissolved in 20 mL of water and 20 mL of ether is used to extract it. How much of the compound will you recover in the ether? (in grams)arrow_forward6.0 mL of cyclohexanol, 8 mL of 85% phosphoric acid, and 10 drops of sulfuric acid are added to a 50-mL round-bottom flask with boiling chips, and the mixture is distilled into an ice-cooled receiver. The distillate is in the form of a colorless bi-phasic mixture. The cyclohexene upper layer is removed from the water layer, and dried over anhydrous calcium chloride. Isolated is cyclohexene as a clear and colorless foul-smelling liquid. Weighing data is given below. Gross mass: 51.24 g Tare mass: 48.04 g Product mass: 3.2g Question: Calculate the theoretical mass of the cyclohexene product, bearing in mind that the cyclohexanol starting material was measured by volume, not by mass (so you must use the density of cyclohexanol to convert milliliters to grams, before calculating the number of moles). Calculate the percent yield of cyclohexene obtained.arrow_forward
- Some procedures include the addition of sodium carbonate before liquid-liquid extraction. What is the purpose of this step?arrow_forwardBased on the resulting chromatograms after visualization with iodine vapor, which between the solvent systems WHITE and MIX resulted in a more effective separation of the pigments of the indigo extract? Explain your answer in terms of the solvent that did not effectively separate the components of the root extract.arrow_forwardWhat is the purpose of using NaOH in an extraction experiment? Mark all that apply. Question options: A To acidify the aqueous layer so the organic acid precipitates out of solution B To remove traces of water from the ether layer so neutral compound is dry C To react with the organic neutral compound and remove it from ether layer D To react with organic acid compound to produce water-soluble salt and extract it into aqueous layer I did put C and D but wrong. I did put only D but also wrong. I put B and D also wrong.arrow_forward
- If 15 mL of dichloromethane was used at one time for extraction, will the amount of the substance extracted be the same as, lesser than, or greater than that if three-5 mL fractions were used? Justify your answer by showing calculations. Assume the mass of the sample to be used is 1.0 g, volume of water is 100 mL and the KD is 5arrow_forwardIf 80% of a desired compound is extracted into the organic phase in each step (leaving 20% in the aqueous layer), how many extractions are necessary to ensure that at least 99% of the compound has been recovered in the organic phase? 1 extraction 2 extractions 3 extractions 4 extractionsarrow_forwardProvide or make a schematic diagram showing the EXTRACTION PROCESSES OF CAFFEINE. please follow instructions. Please note: extraction processes of caffeine only not extraction processes of caffeine from an instant Coffeearrow_forward
- Given 60.00 g of the compound in 60.00 mL water. Calculate amount extracted using multiple (2 x 50.00 mL) extractions with ether.arrow_forwardWrite the equations for the acid-base reactions involved in this experiment. Clearly show the reactants and products for each chemical equation. Experiment: seperation of caffeine and benzoic acid by acid-base extraction Things used in lab: -solid mixture of caffeine and benzoic acid -40mL of dichloromethane -20mL of 1.0 M NaOH -magnesium sulfate as drying agent for caffeine isolation -3.00 M HCl for recovery of benzoic acidarrow_forwardIf you had performed the extraction with dichloromethane (d 1.33 g/mL) as the organic solvent and just water as the aqueous layer, describe what is the top and bottom layer and which layer would each of the three starting compounds (benzil, benzoic acid, and alizarin) would be found in.arrow_forward
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