(TURN IN BEFORE LAB) Student Name: Section: Date: Boric acid has a very temperat
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(TURN IN BEFORE LAB) Student Name: Section: Date: Boric acid has a very temperature sensitive solubility (in 100 mL water) of about 2.5 g at 0°C, about 15 g at a very hot to touch temperature of 60-70 °C , and about 27 g at 100 °C you i. How can make use of these solubility properties to purify boric acid? 2. In part I, why is it important to filter the boric acid solution while it is still very hot? Why is it not "fair" to compare the weights of the dry impure boric acid to the wet purified boric acid? 3. If a contaminant had exactly the same temperature related solubilities that boric acid has, do you think this procedure would remove it? Why, or why not? 4. Experiment 4 Separation and Purification: What's In It? 63Explanation / Answer
1. Boric acid can be purified by taking boric acid in hot water first. About 27 g would dissolve at 100 oC in 100 ml water. The hot solution is filtered to remove any insoluble impurities and then cooled to 0 oC, upon which pure crystals of boric acid forms in solution.
2. It is important to filter ghot solution to remove any insoluble impurities in solution at that temperature.
3. The impure boric acid sample would have weight of impurities added to it and does not tell you exactly how much actual boric acid is present in the sample. Therefore the mass of pure boric acid is alaways adviced to be taken when running an experiment.
4. If contaminant has same solubility properties as boric acid, the procedure described abobe would fail to purify boric acid as both would dissolve equally and crystalize out similarly.
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