group 2
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why does atomic radius increase down the group
• as there are more electron shells so they’re bigger atoms
why does the melting point decrease down the group
• weaker metallic bonding • as metal ions are bigger so sea of delocalised electrons are further from the nucleus leading to lower melting points • Mg does not follow the trend as it has a different lattice structure making it easier to melt
why does the first ionisation energy decrease down the group
• atoms get bigger so outer electron further from the nucleus • more shielding • therefore weaker attraction from nucleus to electron in outer shell
what is the basic reaction for a group 2 element and water
M(s) +2H20(l) -> M(OH)2(aq) + H2(g)
what is the trend with the reaction of water going down the group
it gets more vigorous down the group
what is the trend of solubility with the group 2 hydroxides
they’re increasingly soluble down the group
what is the equation for Mg and hydroxide ions
Mg{2+}(aq)+2OH{-}(aq) –> Mg(OH)2(s)
what is the equation with calcium and hydroxide ions
Ca{2+}(aq)+2OH{-}(aq) –> Ca(OH)2(s) slightly soluble
what is the equation for strontium and barium ions with hydroxide ions
they do not form a precipitate
what is the trend of solubility going down the group for group 2 sulphates
sulfate solubility decreases down the group, with barium sulphate (BaSO4) being completely insoluble
is there an equation of Mg and Sulphate ions
no as no precipitate is formed
what is the equation for Ca and sulphate ions
Ca²⁺(aq) + SO₄²⁻(aq) → CaSO₄(s) slightly soluble
what is the equation for Sr and sulphate ions
Sr²⁺(aq) + SO₄²⁻(aq) → SrSO₄(s)
what is the equation for Ba and sulphate ions
Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)
what is the use of Mg(OH)2
• neutralises excess stomach acid that causes heartburn
what is the use of Ca(OH)2
treats acidic soil
what is the use of CaO
in flue gas desulfurisation • CaO + SO2 –> CaSO3
what is the use of CaCO3
• limestone/ calcium carbonate • treats heartburn
what is the use of BaSO4
as a barium meal to go into your intestines for x-rays
BaSO4 is toxic but why do we still use it for medical x-rays
it’s toxic but safe to use because it is so insoluble it can’t be absorbed into the body
how do you test for Sulphate ions
• acidify the solution using nitric acid or hydrochloric acid (to remove any carbonate impurities that would interfere with the test), and then a solution of barium chloride is added. • if sulphate ions are present a white ppt is formed • Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)
what are the two equations to form Ti from TiO2
• TiO2 +2C +2Cl2 –> TiCl4 +2CO • TiCl4 +2Mg –> Ti + 2MgCl2