2.2 Group 2 - Alkaline Earth Metals
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Describe the two stages of extracting titanium from its ore.
→ titanium dioxide is heated with carbon & chlorine, forming titanium chloride → titanium is reduced by magnesium, forming magnesium chloride & pure titanium
Explain why the usual method of extracting metals does not work for titanium
• heating titanium dioxide with carbon produces a carbide • this is too brittle to be useful as an engineering material
Write the equation for the reaction between magnesium and steam.
Mg (s) + H₂O (g) → MgO (s) + H₂ (g)
Write an ionic equation, with state symbols, to show the reaction of calcium with an excess of water.
Ca (s) + 2H₂O (l) → Ca²⁺ (aq) + 2OH⁻ (aq) + H₂ (g)
State the role of water in the reaction with calcium.
oxidising agent
State a use of magnesium hydroxide in medicine.
neutralises stomach acid (antacid)
From Mg(OH)₂ to Ba(OH)₂, the solubility in water…
increases
From Mg to Ba, the first ionisation energy…
decreases
From Mg to Ba, the atomic radius…
increases
Write the simplest ionic equation for reaction between acidified barium chloride & a solution containing sulfate ions.
Ba²⁺ + SO₄²⁻ → BaSO₄
Explain why acid should be added before barium chloride when testing for sulphate ions.
to remove any carbonate ions because: → they react with barium chloride to form barium carbonate → barium carbonate will precipitate to give a false positive test for sulphate ions
State why sulfuric acid should not be used to acidify barium chloride.
• sulfuric acid contains sulphate ion • which reacts with barium chloride to form white precipitate • (false positive)
Suggest why magnesium chloride wouldn’t be a suitable test for sulphate ions.
• magnesium chloride would react with sulphate ions to form magnesium sulphate • magnesium sulphate is soluble • will not form a precipitate to give any indication of a positive result
In the extraction of strontium from SrO, what role does aluminium have?
• gains oxygen therefore reducing agent
Explain why the precipitate of silver chloride is washed several times with deionised water.
to remove soluble impurities to remove excess silver nitrate
Other than cost, explain one advantage of using magnesium hydroxide rather than magnesium carbonate to reduce acidity in the stomach.
does not produce CO₂
Magnesium ribbon reacts with hot water. Heated magnesium ribbon reacts with steam. State two differences between these reactions.
• faster with steam • hot water produces hydroxide • steam produces oxide
From MgSO₄ to BaSO₄, the solubility in water…
decreases
What is observed when testing for sulphate ions using barium ions?
white precipitate is formed
State one use of barium sulfate in medicine and why.
• barium meals • insoluble therefore not toxic
Suggest one major reason why extracting strontium using aluminium is expensive.
aluminium is extracted using electrolysis
Write the equation for the reaction between magnesium and titanium(IV) chloride.
TiCl₄ + 2Mg → 2MgCl₂ + Ti
Outline the practical steps that you would take to determine the solubility of calcium hydroxide in this solution.
→ take a known volume of saturated solution → evaporate the filtrate until dry → weigh the residue
Equations to remove Sulfur Dioxide from flue gases
CaO + 2H₂O + SO₂ → CaSO₃ + 2H₂O CaCO₃ + 2H₂O + SO₂ → CaSO₃ + 2H₂O + CO₂