Practical 5

• What is reflux?

  Continual boiling and condensing of a reaction mixture preventing reactants/vapour escaping
• What is the use of anti bumping-granules?

  Prevent bumping by forming smaller bubbles and allowing smooth even boiling
• Why can't most organic compounds be heated using a Bunsen burner?

  These compounds are flammable so are hazardous and instead use water bath/electric heating mantle
• How is a liquid product usually separated from a reaction mixture?

  Collected by simple distillation
• How is a solid product usually separated from a reaction mixture?

  Collected by filtration
• How does simple distillation operate?

  Liquids separated by boiling at range close to that of product collected

  Bulb of thermometer must be at height where vapour goes down to condenser to measure boiling point of vapour
• Label the distillation apparatus

  Distillation

  A) Thermometer

  B) Water out

  C) Water in

  D) Heat

  E) Flask

  F) Condenser

  
• Label the reflux apparatus

  Reflux

  A) Water out

  B) Water in

  C) Condenser

  D) Heat

  E) Anti-bumping granules

  
• How does drying a product work?

  Add drying agent to the organic liquid and swirl

  Add more drying agent until liquid changes from cloudy to clear

  Filter liquid into a clean dry flask under reduced pressure using a Buchner apparatus
• How is a product that has been distilled purified?

  Liquid collected placed in a separating funnel for solvent extraction

  Solution added which would react with impurities

  Stopper and shake to form 2 layers with more dense layer at bottom

  Tap opened to remove one layer at a time
• Why may the product be redistilled at the end?

  Use boiling point measured during distillation to indicate identity and purity of the liquid product

  Sharp boiling point = pure product

  Covers a range = impurities present

  Boiling point same as data books = correct product

  Boiling point of reactants and products similar = fractional distillation required
• Why is the percentage yield less than 100% theoretically?

  Side reactions occur so by-products produced instead of expected products

  Reagents used may be impure

  Reaction is incomplete
• Why is the percentage yield less than 100% practically?

  Some product lost in purification steps

  Some product lost in distillation