6. Pavia always provides the mass of drying agent needed in each procedure. Howe
ID: 946301 • Letter: 6
Question
6. Pavia always provides the mass of drying agent needed in each procedure. However, a good lab skill to have is being able to estimate how much vou will need by using a visual check. What are four common signs that you have added enough drying agent and the solution is now dry? 7. Drying agents are anhydrous salts. Based on the definition of an anhydrous salt, what would happen if the lid of the drying agent jar was not replaced during lab? 8. When choosing an ideal solvent for recrystallization, what must be considered about the compound's solubility in the solvent?Explanation / Answer
6.
Before a drying agent is added, the organic layer has to be separated as thoroughly as possible from the aqueous layer. It does make very little sense to add the drying agent if there is a second layer on the bottom (or the top depending which organic solvent is used). The experimenter has to make sure that the "organic layer" is really the organic layer.
The drying process does take some time to complete. Most students are not patient enough and add too much drying agent right from the start and often lose a significant amount of their product this way. The best protocol is to add a small amount first. The mixture is swirled and then allowed to settle. If the solution is translucent and there is still drying agent floating around in the mixture, the solution is reasonably dry. If this is not the case, the mixture is allowed to sit a couple of minutes and then re-examined. If the mixture is still not translucent, a little bit more drying agent is added and the procedure above repeated. .
Small water droplets cause the mixture to be kind of milky in the beginning. Most of the time, the solution becomes translucent if it is dry. In addition, the drying agent does not clump up anymore and floats in the solution as well when the mixture is swirled.
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