In Recrystallization, 1. Why is it important to add the solvent to the solid, ra
ID: 714671 • Letter: I
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In Recrystallization, 1. Why is it important to add the solvent to the solid, rather than the other way around? 2. Why is it important to have the solvent left in the recrystallization flask after the solution has cooled and before isolating the crystals left by vacuum filtration? In Recrystallization, 1. Why is it important to add the solvent to the solid, rather than the other way around? 2. Why is it important to have the solvent left in the recrystallization flask after the solution has cooled and before isolating the crystals left by vacuum filtration? 1. Why is it important to add the solvent to the solid, rather than the other way around? 2. Why is it important to have the solvent left in the recrystallization flask after the solution has cooled and before isolating the crystals left by vacuum filtration?Explanation / Answer
Recrystallization process is based on the principle of solubility. An appropriate solvent is chosen which when heated can dissolve the compound but when cold do not dissolve it .
So the compound is dissolved in a hot solvent to make up a saturated solution which when cooled slowly saperates out the pure crystals of the compound and the impurities remain in the solution.
1) it is recommend to add hot solvent in small small slots to the sample and not the other way round because for recrystallization we have to prepare a saturated solution . If we add solvent drop by drop to the solute we can stop when all the solute dissolves in mimimum amount of solvent and we can precisely prepare a saturated solution .
2) It is important to have the solvent left in the recrystallization flask because even if we follow all precautions we dont get all the amount of pure compound crystals by recrystallization, some of the sample remain in the solution that has cooled . So after separating the pure crystals we can go for second and third round of recrystallization by boiling the left out solution again and cooling it . This will give us maximum possible sample pure crystals.
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