Chapter 13

Question 1

Describe the manufacture of lime

calcium oxide (CaO)

Answer 1

Lime is produced from calcium carbonate (limestone (CaO3)) with thermal decomposition. Calcium carbonate decomposes to form calcium oxide and carbon dioxide. The reaction goes as follows CaCO 3 (s) → CaO(s) + CO 2 (g)

Question 2

Name some uses of lime and slaked lime

Answer 2

In treating acidic soil and neutralising acidic industrial waste products, e.g. flue gas desulfurisation. Also in making ceramics and treating water and in producing gypsum, important in plastic making process.

Question 3

Name the uses of calcium carbonate in the manufacture of iron and cement

Answer 3

Calcium carbonate thermally decomposes to form calcium oxide; which is used to remove the acidic impurities from iron by reacting with them to form molten slag CaO(l) + SiO2(s) → CaSiO3(l). They also make cement as powdered calcium carbonate is heated with clay to form cement.

Question 4

How is cement made with calcium carbonates?

Answer 4

1. Limestone is crushed into a fine powder
2. It is mixed with clay and heated
3. Once it has cooled, it is mixed with water and sand to make a paste
4. When dry, cement is a hard, rock-like substance that is used to bind building materials together
5. As cement sets, it reacts with carbon dioxide in the air
6. Concrete is produced when cement is mixed with sand, an aggregate and water

Question 5

Types of calcium

Answer 5

calcium carbonate, calcium oxide and calcium hydroxide