9 Group 2

Cards (44)

  • Atomic radius going down Group 2
    Atomic radius increases down the group.
    As one goes down the group, the atoms have more shells of electrons making the atom bigger
  • Melting points going down Group 2
    Melting points decrease down the group
    The metallic bonding weakens as the atomic size increases
    The distance between the positive ions and delocalized electrons increases
    electrostatic attractive forces between the + ions and the delocalized electrons weaken
  • Reactivity of Group 2 metals
    Increases down the group
  • Magnesium will react slowly in oxygen without a flame
  • Reaction of magnesium with oxygen
    2 Mg + O22 MgO
  • Reaction of magnesium with hydrochloric acid
    Mg + 2 HClMgCl2 + H2
  • Reaction of magnesium oxide with hydrochloric acid
    MgO + 2 HClMgCl2 + H2O
  • The group 2 metals will burn in oxygen
  • Magnesium oxide (MgO)
    A white solid with a high melting point due to its ionic bonding
  • Reaction of magnesium with steam
    Mg(s) + H2O(g)MgO(s) + H2(g)
  • The other group 2 metals will react with cold water with increasing vigour down the group to form hydroxides
  • Reaction of calcium with water
    Ca + 2 H2O (l) → Ca(OH)2 (aq) + H2 (g)
  • Reaction of strontium with water
    Sr + 2 H2O (l) → Sr(OH)2 (aq) + H2 (g)
  • Reaction of barium with water
    Ba + 2 H2O (l)Ba(OH)2 (aq) + H2 (g)
  • Reaction of magnesium with warm water
    Mg + 2 H2OMg(OH)2 + H2
  • The reaction of magnesium with warm water is much slower than the reaction with steam and there is no flame
  • Titanium cannot be extracted with carbon because titanium carbide (TiC) it is formed rather than titanium
  • Titanium is extracted by reaction with a more reactive metal (e.g. Magnesium)
  • Steps in extracting titanium
    1. TiO2 (solid) is converted to TiCl4 (liquid) at 900°C
    2. The TiCl4 is purified by fractional distillation in an argon atmosphere
    3. The Ti is extracted by Mg in an argon atmosphere at 500°C
  • Calcium oxide can be used to remove SO2 from the waste gases from furnaces (e.g. coal fired power stations) by flue gas desulfurisation
  • Reaction of calcium oxide with sulfur dioxide
    SO2 + CaOCaSO3
  • The calcium sulfite which is formed can be used to make calcium sulfate for plasterboard
  • Group II sulfates become less soluble down the group, with BaSO4 being the least soluble
  • Barium chloride solution acidified with hydrochloric acid
    A reagent used to test for sulfate ions
  • Reaction of barium chloride with a solution containing sulfate ions
    Ba2+ (aq) + SO4
    1. (aq) → BaSO4 (s)
  • Barium sulfate is used in medicine as a 'Barium meal' given to patients who need x-rays of their intestines
  • Barium sulfate is safe to use because its low solubility means it is not absorbed into the blood
  • Reaction of barium metal with sulfuric acid
    Ba + H2SO4BaSO4 + H2
  • The same effect happens to a lesser extent with metals going up the group as the solubility of the sulfates increases
  • Hydrochloric acid is needed to react with carbonate impurities that are often found in salts which would form a white barium carbonate precipitate and so give a false result
  • Formation of a precipitate when barium chloride is added to a solution containing sulfate ions
    SrCl2(aq) + Na2SO4 (aq) → 2NaCl (aq) + SrSO4 (s)
  • Simplified ionic equation for the formation of the precipitate
    Sr2+ (aq) + SO4
    1. (aq) → SrSO4 (s)
  • Group II hydroxides become more soluble down the group
  • All Group II hydroxides when not soluble appear as white precipitates
  • Calcium hydroxide
    Partially soluble in water, appears as a white precipitate, used in agriculture to neutralise acidic soils
  • Lime water
    An aqueous solution of calcium hydroxide, can be used as a test for carbon dioxide
  • Reaction of lime water with carbon dioxide
    Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O(l)
  • Barium hydroxide
    Easily dissolves in water, making the solution strongly alkaline
  • Magnesium hydroxide
    Insoluble in water, appears as a white precipitate, slightly alkaline (pH 9)
  • medical use for magnesium hydroxide
    used in medicine in milk of magnesia to neutralise excess stomach acid and to treat constipation