Salts

• What is a salt?

  A compound formed when some or all of the hydrogen ions in an acid are replaced by metal or ammonium ions.
• What are the two groups salts can be classified into?

  1. Normal Salts
  2. Acid Salts
• What are normal salts?

  Salts that are formed when all of the hydrogen ions in an acid are replaced by metal or ammonium ions.
• What are acid salts?

  Salts that are formed when hydrogen ions in an acid are only partially replaced by metal or ammonium ions.
• Which types of acids can form acid salts?

  Dibasic and tribasic acids
• What is the rule applying to acid salts?

  All acid salts can form normal salts.
• What is water of crystallisation?

  Salts containing a fixed number of water molecules between the ions in their crystal lattice.
• What name is given to salts containing water of crystallisation?

  Hydrated salts
• What name is given to salts that do not have water of crystallisation?

  Anhydrous Salts
• What physical factors does water of crystallisation give salts?

  1. A Crystalline Structure
  2. Colour
• What is the main factor which decides how salts are prepared?

  Solubility
• What method is used to prepare insoluble salts?

  Ionic precipitation
• What is ionic precipitation?

  Two soluble salts in a solution reacting to form an insoluble salt.
• What are the three main methods of preparing soluble salts?

  1. Direct combination
  2. The reaction between a reactive metal and insoluble carbonate.
  3. The reaction between a soluble base i.e alkali and an acid known as titration
• What is direct combination?

  Reacting two elements, a metal and a non -metal , directly with eachother .
• Why can't you react very reactive metals with acid?

  The reaction is too violent
• What is the final product of a reaction between a reactive metal or insoluble carbonate and an acid?

  A pure solution of the required salt and if the reaction has reached completion not acid will remain.
• What ion salts are titrations used to prepare?

  1. Potassium
  2. Sodium
  3. Ammonium
• Why can't the three salts be prepared other than using titration?

  1. Potassium and sodium react violently with acids
  2. Sodium and ammonium carbonates are soluble when the reaction reaches it's completion.
• What is a titration?

  The technique used to to determine the exact volume of acid needed to neutralise a fixed volume of aqueous alkali.
• What can be used in place of an alkali in the titration?

  A carbonate solution
• What are the 8 steps of preparing of soluble salts using titration?

  1. Choose an appropriate alkali or soluble carbonate to provide the cations and an appropriate acid to supply the anions.
  2. Measure a fixed volume of aqueous alkali or carbonate using a pipette. run into a conical flask and add a few drips of indicator solution, e.g phenolphthalein.
  3. Place acid in a burette and take an initial burette reading
  4. Add the acid to the aqueous alkali or carbonate until the neutralisation point is reached.
  5. Take a final burette reading and determine the volume of acid added.
  6. Repeat the titration until you have three volumes of acid within 0.1 cm3 of each other. Average these volumes to determine the volume of acid needed.
  7. Add this volume of acid to the fixed volume of aqueous alkali or carbonate with the indicator
  8. Evaporate the water from the solution