chemistry required practical paper 1

• Salt


  A compound containing a positive ion (metal ion) and a negative ion (from an acid)
• Sources of metal ions for salts

  • Metal
  • Metal oxide
  • Metal hydroxide
  • Metal carbonate
• Negative ion in a salt

  Comes from the acid
• Making a soluble salt using an acid

  1. Use dilute acid as limiting reactant

  2. Heat acid to almost boiling

  3. Add small amounts of metal oxide and stir

  4. Stop adding oxide when solution is blue

  5. Filter to remove unreacted oxide

  6. Evaporate solution to form crystals

  7. Dry the salt crystals
• Cannot make copper sulfate by reacting copper metal with dilute sulfuric acid, as copper is not reactive enough
• The solution turns blue when making copper sulfate, indicating the formation of copper sulfate
• The reaction stops when all the acid has reacted, leaving a neutral solution
• Filtering removes the unreacted insoluble metal oxide
• Evaporating the solution allows copper sulfate crystals to form
• Drying the crystals gives pure, dry copper sulfate
• a burette has a tap at one end which can be opened or closed by turning it, this allows the liquid to flow out when open
• the apparatus used to measure the volume of gas produced is called a burette
• when measuring the volume of gas using a burette, the gas must be bubbled through water as air contains carbon dioxide which will react with limewater producing white precipitate
• titration involves adding a known amount of standard solution (titrant) until an indicator changes colour