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Cards In This Set
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What is the purpose of recrystallization?
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It is the primary method of purifying crude solid compounds
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What is the recrystallization method based on?
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It is a process based on the differences in solubilities of solids in a given solvent system
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How can you increase the solubility of a compound?
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You can increase it with added heat
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How do you get rid of insoluble impurities?
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They are removed through the method of hot filteration
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How do you seperate the purified solid crystals from the surrounding liq.(called Mother Liquor)
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Suction or Vacuum Filteration
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What is the 1st requirment for a suitable solvent for recystallization?
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It should not dissolve the compound at room temp. but readily at its boiling temp.(of the solvent)
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What is the 2nd requirment for a suitable solvent for recystallization?
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It cannot react with the compound to be purified
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What is the 3rd requirment for a suitable solvent for recystallization?
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It should dissolve the impurities very well so they remain in solution even when cooled
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How should the solvent react with insoluble impurities?
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The impurities should not dissolve at all in the solvent so they can be removed mechanically from Hot Filteration
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What is the 4th requirment for a suitable solvent for recystallization?
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It should have a boiling point lower than the melting point of the solid to be purified
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What should you do if the a single solvent does not fufill all the four requirments?
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You should create a "Solvent Pair" where a second solvent miscible with the first solvent is added
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How should the "solvent pair" work?
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One solvent should dissolve the solvent well while the other should dissolve the solvent poorly
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What is an important factor attributing to good crystal growth?
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Depth in the solution; to maximize depth turn the erlenmyer flask 45 degrees on its side
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What is an advantage of using erlenmyer flasks for recrystillization?
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The narrow neck allows for refluxing to occur and so that surface evaporation is minimized(add a cork, or condenser helps)
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When must a Hot Filtration be done during a recrystallization?
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There are insoluble impurities remaining in the solution and there are colored,soluble impurities which necessitates Norit
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