Important Solubility Characteristics Of A Solvent Essay examples

777 Words Jan 24th, 2016 4 Pages
1) Important solubility characteristics for a solvent to be used in the crystallization of an organic solid that’s contaminated with impurities is that the organic solid should have low solubility at low temperatures in the solvent, but highly soluble at high temperatures. Also, the solvent should allow the impurities to be either completely soluble or completely insoluble at all temperatures.

2) One way to improve our percent recovery is by making a second crop of crystals by removing the solvent from the mother liquor, or crystallization filtrate, and then recrystallizing the resulting solid. One other way to minimize lost product is by placing our flask on a hot plate to preheat and keep it on there while the hot solution is being gravity filtered.

3) It’s important to cool a hot, supersaturated solution slowly during a recrystallization because rapid cooling can cause rapid precipitation. Rapid precipitation can trap impurities and give impure crystals.

4) Our 20 gram sample:
0.95 of 20g = 19g of A
0.05 of 20g = 1g of B

Minimum amount of toluene @ any temperature to keep 1g of B dissolved = 1g of B * (100ml of toluene/0.5g of B) = 200ml of toluene needed

Amount of A dissolved in 200ml of toluene @ 110 C = 200ml of toluene * (10.0g of A/100ml of toluene) = 20g of A dissolved
20g of A > initial 19g of A

Amount of pure A recovered = 19g of A – [200 ml of toluene * (1.5g of A /100ml of toluene 1.5g of A)] = 19 g of A in initial sample – 3g of dissolved A = 16g of pure…

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