salts and solubility

• Salt


  Formed when a metal or ammonium ions take the place of some or all of the replaceable hydrogens of an acid
• Normal salts


  • Formed when all the replaceable hydrogens of an acid have been replaced by metal or ammonium hydrogens (monobasic acids form normal salts)
• Acid salts


  • Formed when some of the replaceable hydrogen ions of an acid have been replaced by metal or ammonium ions (Tribasic and dibasic acids can form acid and normal salts)
• Anions


  • Nitrates (NO₃⁻)
  • Chlorides (Cl⁻)
  • Bromides (Br⁻)
  • Iodides (I⁻)
  • Sulfates (SO₄²⁻)
  • Carbonates (CO₃²⁻)
  • Phosphates (PO₄³⁻)
  • Hydroxides (OH⁻)
  • Sulfides (S²⁻)
  • Oxides (O²⁻)
• Salt


  Compound formed when some or all of the hydrogen ions in an acid is replaced by a metal or ammonium ion
• Types of salts


  • Acid salt
  • Normal salt
• Acid salt


  Salt formed when only some of the H+ ions from an acid are replaced
• Normal salt


  Salt formed when all of the H+ ions from the acid are replaced
• Acid salt example


  • NaHSO4 (sodium hydrogen sulfate)
• Normal salt example


  • Na2SO4 (sodium sulfate)
• Solubility of salts


  • All nitrates are soluble
  • All sodium, potassium and ammonium salts are soluble
  • All sulfates are soluble except lead, barium, mercury and calcium
  • All chlorides are soluble except silver, lead (soluble in hot water)
  • All carbonates are insoluble except potassium, sodium and ammonium
  • All metal oxides are insoluble except potassium, sodium and calcium
  • All metal hydroxides are insoluble except potassium, sodium and ammonium
• Preparing an insoluble salt

  1. Add two soluble salts to produce a precipitate

  2. Filter and wash the precipitate

  3. Dry the precipitated salt
• Preparing a soluble sodium, potassium or ammonium salt

  1. Pipette sodium hydroxide into a flask

  2. Add hydrochloric acid from a burette until neutralised

  3. Repeat titration without indicator

  4. Heat to evaporate water and leave to crystallise

  5. Rinse and dry the salt crystals
• Preparing other soluble salts

  1. React an insoluble base or carbonate with an acid

  2. Filter to remove excess reactant

  3. Evaporate the filtrate until saturated

  4. Allow to cool and crystallise

  5. Wash and dry the salt crystals
• Preparing an anhydrous binary salt

  Heat the two elements together
• Water of crystallisation


  Fixed amount of water present in the crystal lattice of a salt, affecting its shape and colour
• Heating a hydrated salt

  Removes the water of crystallisation
• Uses of salts


  • Calcium carbonate in cement
  • Sodium chloride, nitrite, nitrate in food preservation
  • Calcium sulfate in plaster of Paris
  • Magnesium sulfate as Epsom salts