Group 2

• Sulphur dioxide can be removed from factory exhaust gases using flue-gas desulphurisation
• Calcium oxide (base) reacts with acidic sulphur dioxide to form calcium sulphite , which is oxidised to calcium suphate, which is used to make plasterboard
• Group 2 metals react with water to form metal hydroxides and hydrogen.
• Give the equation for the reaction of a group 2 metal with water.

  Mg (s) + H2O (l) --> Mg(OH)2 + H2 (g)
• Magnesium reacts very slowly with cold water but reacts rapidly with steam.
• Give the equation for the reaction between magnesium and steam.

  Mg (s) + 2H2O (g) --> MgO (s) + H2 (g)
• As group 2 descends down the group, the metal hydroxides become more soluble.
• Magnesium hydroxide and calcium hydroxide are insoluble in water. The other precipitates are soluble.
• As group 2 descends, the metal sulphates become more insoluble.
• Barium sulphate is the only metal sulphate in group 2 that is insoluble.
• Extraction of titanium:

  1. Ore of titanium TiO2 is converted to TiO4 at 900C
  2. The Ti is extracted by Mg in an argon atmosphere at 1000C
• Give the equations for the extraction of titanium.

  1. TiO2 (s) + 2Cl2 + 2C --> TiCl4 (l) + CO2
  2. TiCl4 + 2Mg --> Ti + 2MgCl2
• Calcium oxide or calcium carbonate to remove sulphur dioxide from flue (chimney) gas. This process is called flue-gas desulphurisation.
• Flue-gas desulphurisation equations:

  1. CaO (s) + 2 H2O (l) + SO2 (g) + ½ O2 (g) --> CaSO4.2H2O
  2. CaCO3 (s) + ½ O2 (g) + SO2 (g) -->`CaSO4 (s) + CO2 (g)