CHEM 0310 Lecture Notes - Filter Paper, General Idea

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28 May 2014

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The crude benzoic acid attained from the previous lab was weighed. The boiling water was slowly added to the crystals. The solution was then filtered via hot gravity filtration as shown in figure 2. The filtrate was then removed and cooled in the hood. the crystals were collected by vacuum filtration, and their mass was recorded. Samples of both crude and pure crystal samples were placed in separate capillary tubes. samples were placed in the melt-temp, as shown in figure 3. A fast run was first conducted, followed by slow accurate run for both samples. The ranges for the melting points were recorded. The starting mass of crude benzoic acid was found to be 6. 25 g. when the solution was filtrated, the filtrate was observed to be slightly pink in color and crystals begin the form almost immediately after filtration began. As the filtrate was placed in the hood, more crystals began to form.

Related Questions

If you were to run the experiment without using any celite, what would happen to the purity of your sample and why?

What practical purpose does the distillation serve in this experiment?

The experiment is below. Just answer the above questions.

Introduction Caffeine is one of three legal, mind-altering drugs available in the U.S without a prescription. Two common sources of this drug are tea and coffee, both of which are prepared via extraction of the solid foodstuff with liquid water. In this lab you will extract caffeine from food samples with liquid solvents and quantify the amount obtained. Laborator Hypothesis: We can rank various tea and coffee samples by caffeine content by performing a solid-liquid extraction from the foodstuff, followed by analysis via thin-layer chromatography. Experiment: In a 50 mL Erlenmeyer flask were placed 2.0 g of black tea. Dichloromethane (15 mL) and 0.2 M NaOH (5 mL) were added successively, and the stoppered flask was swirled gently by hand for 10 minutes (note: avoid vigorous shaking, as it will cause an emulsion to form). The dicloromethane layer was separated from the leaves and the aqueous layer by vacuum filtration through 7 g Celite 545, and the leaves were washed with a further 15 mL dichloromethane. The combined dichloromethane solution was placed in a 50 mL round bottom flask and concentrated to a minimal volume (ca. 1 mL) via simple distillation. The remaining dichloromethane solutions was transferred to a watch glass via pipet, and the solvent was evaporated in a fume hood. The sample was evaluated by TLC (a mixture of methanol and ethyl acetate as the mobile phase, co-spotted with authentic caffeine). Data: What was your crude yield of caffeine? What was the mass percentage of caffeine in your food source'? Given that the materials we are interested in are UV active, compared to the TLC standard how would you characterize the purity of your caffeine extracts? Conclusions: Can you comment on the purity of your caffeine sample? For all samples your class worked with where does your foodstuff rank in terms of caffeine content? How much caffeine is reported for the typical serving of coffee or tea? How did your extraction and isolation compare with the typical serving?

If you were to use THF, or tetrahydrofuran instead of dicholormethane for this experiment, could you still successfully extract your caffeine? Why or why not? (Consider what is necessary for an extraction to work)

If you were to use an acidic water solution for this extraction rather than a basic one, could you still perform the extraction?â

The experiment is below. Just answer the above questions.

To a 125 mL Erlenmeyer flask were added 1.220 g of solid copper (II) nitrate trihydrate, 10.0 mL of water, and a magnetic stirring bar. To the stirred solution was added, in small portions, a total of 2.000 g of sodium carbonate decahydrate. The blue solid that formed was isolated by vacuum filtration, partially dried, and placed in a second 125 mL Erlenmeyer flask. To the flask was added 2.0 mL of 12 M hydrochloric acid. To the resultant yellow solution was added 0.500 g of solid copper; the mixture was heated until the solution became colorless. After cooling the solution to room temperature, addition of 10.0 mL of water caused white, solid copper (I) chloride to separate from the solution. Isolated by vacuum filtration was 0.705 g of solid copper (I) chloride. Calculate the percent yield of copper (I) chloride. The equations for the reactions performed are shown below

Cu2+(aq) + CO32-(aq) â CuCO3(s)

CuCO3(aq) + 2H+(aq) + 4Cl-(aq) â CuCl42-(aq) + H2O(l) + CO2(g)

CuCl42-(aq) +Cu(s) â 2CuCl(s) + 2Cl-(aq)

CHEM 0310 Lecture Notes - Filter Paper, General Idea

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