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This quiz contains 12 questions from a mix of 1 subtopics.
What is the term for the technique used to purify organic solids by dissolving them in hot solvent and allowing them to cool slowly?
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Which technique is used to prevent the loss of reagents during organic reactions?
filtration under reduced pressure
reflux
recrystallisation
distillation
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What is the purpose of recrystallisation?
to separate a solid product from liquid impurities
to purify organic solids
to heat organic reactions
to determine the purity of a substance
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What is the first step in the recrystallisation process?
dissolving the impure solid in hot solvent to create a saturated solution
allowing the solution to cool slowly
comparing the observed melting point with known literature values
filtering the crystals and washing them with cold solvent
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What happens to impurities during recrystallisation?
they are filtered out before the solution cools
they evaporate during the heating process
they crystallise out with the pure product
they remain dissolved in the solution
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Which of the following is NOT a characteristic of an ideal recrystallisation solvent?
ensures the maximum amount of product crystallises upon cooling
promotes crystallisation of the solid as the solution cools
has a high solubility for the product when cold
fully dissolves the solid at high temperatures
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What happens if the solubility of the product is too low in the hot solvent during recrystallisation?
impurities stay dissolved in the solution
the product remains dissolved in the cold solution
the product does not fully dissolve, preventing recrystallisation
crystals fail to form, leading to product loss during filtration
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What is the purpose of filtration under reduced pressure?
to purify organic solids
to determine the purity of a substance
to separate a solid product from liquid impurities
to heat organic reactions
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What does the melting point of a compound indicate?
its purity
its solubility
its boiling point
its reactivity
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What does a close match between observed and literature melting points suggest?
high purity
the need for recrystallisation
incorrect measurement technique
the presence of impurities
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What is the most effective condition for distillation?
when the product's boiling point is lower than that of the reactants
when the product's melting point is lower than that of the reactants
when the product's boiling point is the same as that of the reactants
when the product's boiling point is higher than that of the reactants
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Recrystallisation exploits the principle that solubility typically with temperature, leading impurities to stay dissolved while the pure product crystallises.
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