RP 10

• What is reflux in chemistry?

  Continuous boiling and condensing of a mixture
• Why is reflux used in organic reactions?

  It prevents loss of reactants or products
• What are anti-bumping granules used for?

  To prevent vigorous or uneven boiling
• How do anti-bumping granules work?

  They create small bubbles instead of large ones
• What is the purpose of a separating funnel in purifying an organic liquid?

  • To separate two layers
  • Higher density liquid is the bottom layer
  • Organic product layer is above
• What should you do with the distillate of an impure product?

  Put it into a separating funnel
• How does sodium hydrogencarbonate solution purify the product?

  It removes acidic impurities by neutralization
• What products are formed when sodium hydrogencarbonate neutralizes acids?

  Water, carbon dioxide, and sodium sulfate
• What is the purpose of using saturated sodium chloride solution?

  It helps separate the organic layer from aqueous layer
• What should you do after allowing layers to separate in a separating funnel?

  Run and discard the aqueous layer
• What is added to the organic liquid to dry it?

  Three spatula loads of drying agent
• What is the role of anhydrous sodium sulfate?

  It acts as a drying agent for organic liquids
• What is the purpose of carefully decanting the liquid into the distillation flask?

  To avoid transferring the drying agent
• What is the final step to collect the pure product after drying?

  Distil to collect the pure product
• What happens to the liquid when anhydrous calcium chloride is used?

  It soaks up any remaining water
• How does the purity of a sample affect its melting point?

  A pure sample has a sharp melting point
• What indicates the presence of impurities in a melting point measurement?

  Lowered melting point and broader range
• How can melting point be measured?

  Using an electronic melting point machine or capillary tube

  
• What is a potential error in melting point measurement?

  Thermometer temperature may differ from sample
• What is the purpose of measuring boiling point?

  To determine the purity of a liquid
• How can boiling point be measured accurately?

  Thermometer should measure saturated vapor temperature
• Why is boiling point not the most accurate identification method?

  Several substances may share the same boiling point
• What are the steps of recrystallisation?

  1. Dissolve impure compound in hot solvent
  2. Hot filter solution to remove insoluble impurities
  3. Cool solution in ice to increase yield
  4. Use Buchner flask for suction filtration
  5. Wash crystals with distilled water
  6. Dry crystals between absorbent paper
• Why is a minimum volume of solvent used in recrystallisation?

  To obtain a saturated solution for crystallization
• What is the purpose of hot filtering in recrystallisation?

  To remove insoluble impurities
• How does cooling the solution in ice affect crystallization?

  It increases yield by ensuring crystallization
• What is the role of a Buchner flask in recrystallisation?

  It speeds up the filtration process
• Why are crystals washed with distilled water?

  To remove soluble impurities
• What is done to dry the crystals after washing?

  They are dried between absorbent paper
• What are the causes of loss of yield in recrystallisation?

  • Crystals lost during filtering or washing
  • Some product remains in solution
  • Other side reactions may occur