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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