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)2 (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)2 (s) + 2HCl (aq) → MgCl2 (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)
