Acids, bases and salts

• How can you make soluble salts?

  By reacting an acid with an insoluble base
• What is the role of the acid in making soluble salts?

  It provides one of the ions needed for the salt
• What is the role of the insoluble base in making soluble salts?

  It provides the other ion needed for the salt
• What is the first step in the process of making soluble salts?

  Heat the acid in a water bath
• What should you do after heating the acid?

  Add the base to the acid gradually
• What indicates that the reaction between the acid and base is complete?

  When no more solid base reacts
• What should you do with the excess solid after the reaction?

  Filter it off to obtain the solution
• What is the purpose of gently heating the solution after filtering?

  To evaporate some of the water slowly
• What happens after the solution is heated and some water evaporates?

  Leave it to cool for salt crystallization
• What should you do with the solid salt after crystallization?

  Filter it off and leave it to dry
• What is an example of making a soluble salt?

  Add copper oxide to warm sulfuric acid
• What is the word equation for the reaction between copper oxide and sulfuric acid?

  Copper oxide + sulfuric acid → copper sulfate + water
• Why was the mixture warmed at the start?

  To speed up the reaction between acid and base
• Why was more copper oxide added than needed?

  To ensure all the acid reacted
• How can you tell when the base is in excess?

  The excess solid sinks to the bottom
• Why was the water not all boiled off from the copper sulfate solution?

  To create hydrated copper sulfate solution
• Why are the crystals dried with filter paper?

  To prevent water loss from the crystals
• What forms when two solutions are mixed in a beaker?

  A precipitate
• What is the purpose of filtration in making insoluble salts?

  To separate the precipitate from the solution
• What should you rinse the salt with after filtration?

  Distilled water
• What is the final step after scraping the salt?

  To dab it dry
• What is the purpose of titrations?

  • To determine the exact amount of acid needed to neutralise alkali
  • Or vice versa
• What equipment is used to add alkali in a titration?

  A pipette and pipette filler
• What indicator is used in the titration process?

  Phenolphthalein
• What should you do when you think the end-point is near during titration?

  Go more slowly with the acid addition
• What colour indicates that the alkali has been neutralised?

  Colourless
• What colour is the solution before the acid is added?

  Pink
• What colour does phenolphthalein turn in an alkali solution?

  Pink
• What colour does phenolphthalein turn in an acid solution?

  Colourless
• What should you do after recording the volume of acid used in titration?

  Repeat the process for accuracy
• How does the colour of the solution change during titration?

  From pink to colourless