14.7 Chapter summary

14.7 Chapter summary (ESCSV)

Presentation: 283F

• The growth of South Africa's chemical industry was largely due to the mining industry, which requires explosives for their operation. One of South Africa's major chemical companies is Sasol. Other important examples of chemical industries in the country are the chloralkali and fertiliser industries.

• The fertiliser industry is very important in providing fertilisers with the correct nutrients in the correct quantities to ensure maximum growth for various plants and crops.

• All plants need certain macronutrients (e.g. carbon, hydrogen, oxygen, potassium, nitrogen and phosphorus) and micronutrients (e.g. iron, chlorine, copper and zinc) in order to survive. Fertilisers provide these nutrients.

• In plants, essential nutrients are obtained from the atmosphere or from the soil.

• Animals also need similar nutrients, but they obtain most of these from plants or plant products. They may also obtain them from other animals, which may have fed on plants during their life.

• Fertilisers can be produced industrially using a number of chemical processes: the Haber process reacts nitrogen and hydrogen to produce ammonia; the Ostwald process reacts oxygen and ammonia to produce nitric acid; the Contact process produces sulfuric acid; sulfuric acid then reacts with phosphate rock to produce phosphoric acid, after which phosphoric acid reacts with ground phosphate rock to produce fertilisers such as triple superphosphate.

• Potassium is obtained from potash through a mineral salt extraction process.

• Fertilisers can have a damaging effect on the environment when they are present in high quantities in ecosystems. This can lead to eutrophication. A number of preventative actions can be taken to reduce these impacts.