Uses of Group 2 Elements (AQA AS Chemistry) : Revision Note

Stewart Hird

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Uses of Group 2

Uses of Calcium

  • Three different calcium compounds are used commonly in agriculture, construction and iron extraction:

    • Limestone - this is impure calcium carbonate

    • Quicklime - this is calcium oxide, formed by the thermal decomposition of calcium carbonate

    • Slaked lime - this is calcium hydroxide formed when water is added to quicklime

      • Ca(OH)(s) + 2H(aq) → Ca2+ (aq) + 2H2O (l)

  • All three materials are used in agriculture to raise the pH of the soil

  • Over time, the soil becomes more acidic while the optimum pH for many crops to grow is at around 6-6.5

  • The compounds are all bases and react with the acids in the soil and raise the pH of the soil

  • Calcium carbonate is more commonly used in agricultural lime as it is cheaper and safer to handle

    • However, due to calcium carbonate being largely insoluble, it acts more slowly than calcium hydroxide

  • Calcium compounds are also used to remove sulfur dioxide from flue gases in a process known as sulfur scrubbing

Uses of Barium

  • Barium is used in medicine in the form of barium sulfate, BaSO4

  • A barium meal or barium swallow containing BaSO4 is given to a patient who needs an X-ray on their intestines

  • Barium absorbs X-rays which means the gut shows up white on the image

  • Barium is toxic though can be used in this form because

    • Barium sulfate is insoluble so is not absorbed into the blood

    • The barium meal or swallow is only a small amount for the patient to ingest

  • Barium chloride or barium nitrate solution can be used in the test for sulfate ions, SO42-

Uses of Magnesium

  • Magnesium hydroxide, Mg(OH)2, is partially soluble in water and is used in suspension (known as 'milk of magnesia') to neutralise excess acid in the stomach and treat constipation

Mg(OH)(s) + 2HCl (aq) → MgCl(aq) + 2H2O (l)

  • It is safe to use as the magnesium hydroxide is only partially soluble making the solution only slightly alkaline (pH ≅ 10) due to the low OH- concentration

  • Magnesium is also used in the extraction of titanium from its ore, TiO2

  • TiO2 is heated in a stream of chlorine, in the presence of coke, to produce TiCl4

TiO2 (s) + 2C (s) + 2Cl2 (g) → TiCl4 (g) + 2CO (g)

  • The titanium is extracted from its chloride by reduction with magnesium (sodium can also be used)

TiCl4 (g) + 2Mg (l) → Ti (s) + 2MgCl2 (l)

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Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

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