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2.2.4Inorganic Chemistry

Uses of Group 2

5 min read 5 parts Lesson 7 of 27

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Section 1 of 5Magnesium

2.2.4 Uses of Group 2
Antacid
  • Magnesium hydroxide, in milk of magnesia, neutralises excess stomach acid: Mg(OH)₂(s) + 2HCl(aq) → MgCl₂(aq) + 2H₂O(l).
Safe alkali
  • Its low solubility keeps the pH near 10, so it is not strongly alkaline and does not harm the stomach lining.
Titanium extraction
  • TiCl₄ is reduced by magnesium at high temperature in an inert atmosphere: TiCl₄ + 2Mg → Ti + 2MgCl₂.
Why magnesium
  • It is a strong enough reducing agent to remove chlorine from titanium, and the chloride by-product is easily separated.

Section 2 of 5Calcium Compounds

Limestone
  • Impure calcium carbonate, CaCO₃, is used in construction and to make quicklime.
Quicklime
  • Calcium oxide, CaO, is made by heating calcium carbonate: CaCO₃ → CaO + CO₂.
Slaked lime
  • Calcium hydroxide, Ca(OH)₂, is made by adding water to quicklime and neutralises acidic soil in agriculture.
Iron extraction
  • Calcium oxide removes acidic silicon dioxide impurities as slag: CaO + SiO₂ → CaSiO₃.

Section 3 of 5Environmental and Medical Uses

1
Calcium carbonate or calcium oxide is used in flue-gas desulfurisation, reacting with sulfur dioxide from power stations.
2
A typical reaction is CaO(s) + SO₂(g) → CaSO₃(s), which removes acidic gas before it reaches the atmosphere.
3
Calcium hydroxide is spread on fields to raise soil pH where acidity limits crop growth.
4
Barium sulfate is used in barium meals because it is insoluble and absorbs X-rays.
5
Soluble barium compounds are poisonous, so only the insoluble sulfate can be given to patients.

Section 4 of 5Why Properties Matter

Why Properties Matter
Basicity
  • Group 2 oxides and hydroxides are bases, so they neutralise acids in medicine, soil and industry.
Solubility
  • Low solubility of Mg(OH)₂ makes it a gentle antacid, while the insolubility of BaSO₄ makes it safe to swallow.
Reducing power
  • The strong reducing power of magnesium allows it to produce titanium that carbon cannot produce well.

Section 5 of 5Exam Checklist & Tips

2.2.4 – Key Points for the Exam

  • Quicklime Calcium oxide, produced by thermal decomposition of limestone.
  • Slaked lime Calcium hydroxide, formed when quicklime reacts with water.
  • Slag Molten waste produced when a basic oxide combines with impurities in a furnace.
  • Flue-gas desulfurisation Removing sulfur dioxide from waste gases using a basic calcium compound.

Common Mistakes

  • Confusing quicklime (CaO) with slaked lime (Ca(OH)₂).
  • Saying soluble barium salts are safe for barium meals.
  • Writing the titanium extraction without an inert atmosphere, where titanium would react with air.
  • Describing limestone as pure calcium oxide.
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