4-preparing copper sulfate

• what is a base?

  any substance which reacts with an acid to form a salt and water only#
• what is the general reaction of aqueous solution reacting with metal oxides


  metal hydroxide
• what is a neutralisation reaction?


  a reaction between an acid and a base
• Explain why, if soluble salts are prepared from an acid and an insoluble reactant: a excess of the reactant is added


  to ensure there is a complete reaction
• Explain why, if soluble salts are prepared from an acid and an insoluble reactant: a excess of the reactant is removed

  ensure the purity of the product
• Explain why, if soluble salts are prepared from an acid and an insoluble reactant: the solution remaining is only salt and water


  ensuring a high quality, pure product
• what is the aim of the experiment?

  to investigate the preparation of pure, dry hydrated copper sulfate crystals starting from copper oxide.
• what apparatus is needed?

  • measuring cylinder
  • beaker
  • glass rod
  • spatula
  • evaporating basin
  • conical flask
  • filter
  • water bath
  • bunsen burner
• what is step 1?

  place some sulfuric acid in a conical flask and warm it in a water bath
• what is step 2?

  add a spatula of copper oxide powder to the acid and stir with a glass rod
• what is step 3?

  keep adding copper oxide until it is in excess
• what is step 4?

  filter the mixture to remove excess copper oxide
• what is step 5?

  pour the filtrate (copper sulfate solution) into an evaporating basin
• what is step 6?

  heat copper sulfate solution to evaporate half the water
• what is step 7?

  pour the solution into a watch glass and leave to allow all of the water to evaporate
• What safety precautions should you take when carrying out this experiment and why?

  • use dilute sulfuric acid because concentrated acid is corrosive and damages skin and clothes
  • ensure your wearing protection eg. goggles as the hot copper sulfate solution spits out during crystallisation whcih causes damage to our eyes and skin
  • ensure the boiling water bath is stable because skin can burn by boiling the water bath
• why is it important that the sulfuric acid is warmed in a water bath?

  warm acid will react faster than cold acid, ensuring all the acid reacts with the copper oxide
• what colour was the copper sulfate solution that formed?

  blue
• why was it necessary to add copper oxide until it was present in excess?

  to ensure there is a complete reaction and all the copper oxide has reacted with the sulfuric acid
• how did you separate the excess copper oxide from the copper sulfate solution?


  filtration
• what is meant by the filtrate?


  liquid that has passed through a filter.(copper sulfate)
• what is meant by the residue?

  material left behind (copper oxide)
• why is a water bath used to evaporate the water from the copper sulfate solution instead of heating the evaporating basin directly with a Bunsen burner?


  more controlled and gentle heating, reduces risk of splattering
• why should you not evaporate all of the water from the copper sulfate solution?

  removing all the water would cause the crystals to lose their blue colour and instead be hydrated copper sulfate crystals