Describe the principles underlying recrystallization. What are the five steps used for recrystallization and what does...

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Chemistry

Describe the principles underlying recrystallization. What arethe five steps used for recrystallization and what does each stepaccomplish?

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he principle behind recrystallization is that the amount ofsolute that can be dissolved by a solvent increases withtemperature In recrystallization a solution is created bydissolving a solute in a solvent at or near its boiling point Atthis high temperature the solute has a greatly increasedsolubility in the solvent so a much smaller quantity of hotsolvent is needed than when the solvent is at room temperatureWhen the solution is later cooled after filtering out insolubleimpurities the amount of solute that remains dissolved dropsprecipitously At the cooler temperature the solution is saturatedat a much lower concentration of solute The solute that can nolonger be held in solution forms purified crystals of solute whichcan later be collectedRecrystallization works only when the proper solvent is usedThe solute must be relatively insoluble in the solvent at roomtemperature but much more soluble in the solvent at highertemperature At the same time impurities that are present musteither be soluble in the solvent at room temperature or insolublein the solvent at a high temperature For example if you wanted topurify a sample of Compound X which is contaminated by a smallamount of Compound Y an appropriate solvent would be one in whichall of Compound Y dissolved at room temperature because theimpurities will stay in solution and pass through filter paperleaving only pure crystals behind Also appropriate would be asolvent in which the impurities are insoluble at a high temperaturebecause they will remain solid in the boiling solvent and can thenbe filtered out When dealing with unknowns you will need to testwhich solvent will work best for you According to the adage Likedissolves like a solvent that has a similar polarity to See Answer

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