Unit 13: Carbonates

Question 1

How is lime (calcium oxide) manufactured?

Answer 1

By the thermal decomposition of calcium carbonate (limestone), in other words, it is heated. CaCO3 –> CaO + CO2.

Question 2

What are some of the uses of lime and slaked lime?

Answer 2

1. To neutralise acidic soil.

2. To neutralise acidic industrial waste products.

Question 3

What are some of the uses of calcium carbonate?

Answer 3

1. In the manufacture of cement, limestone is heated with sand and silicates such as clay. Cement is a mix of calcium silicates and aluminates. When water is added, a complex series of reactions occur that make it set.
2. In the manufacture of iron, the calcium carbonate thermally decomposes to calcium oxide and carbon dioxide. The calcium oxide forms a slag with the impurities in the iron ore.

Question 4

Which carbonates are soluble in water?

Answer 4

Only potassium, sodium and ammonium carbonates are soluble in water.

Question 5

Which carbonates are thermally stable?

Answer 5

Potassium and sodium, all carbonates of metals below sodium on the reactivity series are not thermally stable.

Question 6

What is the solubility of bicarbonates?

Answer 6

All bicarbonates are soluble in water.

Question 7

What is the thermal stability of bicarbonates?

Answer 7

No bicarbonates are thermally stable.