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preparation and separation techniques 

  • chemists often have to carry out reactions and then separate the products from the initial reactants

  • when deciding which techniques to use the following must be taken into consideration

  • liquid or solid reagents

  • how long the reaction takes

  • amount of heat required and volatility of liquid reagents

  • preparation and separation techniques

    • reflux

    • distillation

    • fractional distillation

    • drying

    • solvent extraction

    • precipitation

    • crystallisation

    • filtration

    • chromatography

  • apparatus

    • condenser

    • round bottomed flask

    • heating mantle

    • lab jack

    • anti bumping granules

  • reflux

    • allow organic substances with low boiling point to be heated for long periods without loss due to evaporation

    • many organic reactions require heating for long periods in order to maximise the yeild

    • the reaction mixture is places in a flask and a lie big condenser is attached

    • the condenser cools the evaporating vapours returning them to the flask

  • precautions

    • use a heating mantle for higher temperatures than boiling water

    • use anti bumping granules to prevent formation of large gas bubbles in the reaction mixture

    • water flow goes in at the bottom of the condenser and out at the top

  • distillation

    • used to separate compounds out from a mixture of liquids

    • relies on differences in boiling points

    • liquids are heated until the vapour pressure equals that of atmospheric pressure where the compound starts to boil

    • components of lower boiling point boil first and are collected first

  • fractional distillation

    • used to separate several liquids from a mixture

  • solvent extraction

    • a way of separating compounds based on their differing solubility in 2 immiscible liquids eg petroleum spirit and water

    • a way of purifying a a substance eg chlorophyll extraction

    • chlorophyll is more soluble in petroleum spirit than water.when it is extracted from pant leaves an acetone/water mixture is used

MT

preparation and separation techniques 

  • chemists often have to carry out reactions and then separate the products from the initial reactants

  • when deciding which techniques to use the following must be taken into consideration

  • liquid or solid reagents

  • how long the reaction takes

  • amount of heat required and volatility of liquid reagents

  • preparation and separation techniques

    • reflux

    • distillation

    • fractional distillation

    • drying

    • solvent extraction

    • precipitation

    • crystallisation

    • filtration

    • chromatography

  • apparatus

    • condenser

    • round bottomed flask

    • heating mantle

    • lab jack

    • anti bumping granules

  • reflux

    • allow organic substances with low boiling point to be heated for long periods without loss due to evaporation

    • many organic reactions require heating for long periods in order to maximise the yeild

    • the reaction mixture is places in a flask and a lie big condenser is attached

    • the condenser cools the evaporating vapours returning them to the flask

  • precautions

    • use a heating mantle for higher temperatures than boiling water

    • use anti bumping granules to prevent formation of large gas bubbles in the reaction mixture

    • water flow goes in at the bottom of the condenser and out at the top

  • distillation

    • used to separate compounds out from a mixture of liquids

    • relies on differences in boiling points

    • liquids are heated until the vapour pressure equals that of atmospheric pressure where the compound starts to boil

    • components of lower boiling point boil first and are collected first

  • fractional distillation

    • used to separate several liquids from a mixture

  • solvent extraction

    • a way of separating compounds based on their differing solubility in 2 immiscible liquids eg petroleum spirit and water

    • a way of purifying a a substance eg chlorophyll extraction

    • chlorophyll is more soluble in petroleum spirit than water.when it is extracted from pant leaves an acetone/water mixture is used

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