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Cards In This Set
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How are crude solid compounds isolated from a chemical synthesis or extraction purified?
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By recrystalization. Which is based on the difference of solubility of solids in a given solvent system
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How does the solubility add in recrystallization?
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The solubility of a compound increases with temperature so that a saturated solution of compound is made at an elevated
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How does the solubility add in recrystallization?
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Temperature, the same compound can be recovered in solid form by simply allowing the solution to cool
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What is saturated?
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Being the most concentrated solution possible at a given temperature; unable to dissolve still more of a substance
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How does purification result?
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Because the soluble impurities contaminating the main component are in much smaller concentration
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How does purification result?
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And hence will remain in solution under both hot and cold conditions.
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How does purification result?
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Even if there are many impurities in solution, the growing crystals of the chief component often reject them in recrystalization process
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How does purification result?
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Due to the fact that the impurities do not meet the required geometry of the already forming crystal lattice
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How do we get rid of insoluble impurities?
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These are removed while solution is at elevated temp (hot gravity filtration)
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How are the purified solid crystals separated from surrounding liquid (mother liquid)
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By a procedure called suction / vaccum filtration
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What are the 4 basic requirements of a good solvent for recrystallization?
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1) It must dissolve the compound only sparingly or not at all at room temperature, but readily at its boiling point.
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What are the 4 basic requirements of a good solvent for recrystallization?
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1) Should also dissolve compound in reasonable volume
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What are the 4 basic requirements of a good solvent for recrystallization?
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2) It cannot react chemically with the compound to be purified
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What are the 4 basic requirements of a good solvent for recrystallization?
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3) It should either dissolve impurities exceedingly well (so that they remain in solution even when cooled)
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What are the 4 basic requirements of a good solvent for recrystallization?
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Or not at all (so that they can be mechanically removed from the hot solution
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