Recrystallisation of a sample of benzoic acid

Key steps and observations in the procedure to recrystallise a sample of benzoic acid:

• a known mass of benzoic acid crystals are dissolved in a minimum amount of hot water

• the solution is filtered use a heated funnel to remove insoluble impurities

• the solution in cooled in ice, and a seed crystal is added to speed up the process

• the crystals are collected by vaccuum filtration which separates benzoic acid from soluble impurities

• crystals air dry and their mass is obtained

Why is the minimum amount of hot water used

• benzoic acid is very soluble in hot water

• the more solvent the less crystals will be obtained

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