Quick lime

Quicklime is the compound which is used commonly for whitewashing houses. The chemical name of quick lime or lime is calcium oxide. The chemical formula of quicklime is CaO.

Manufacture of Quicklime

The raw material used for the manufacture of quicklime is calcium carbonate (CaCO₃). Lime is manufactured by heating the calcium carbonate to a temperature of 1273 K in a lime kiln. After getting heated to such a high temperature calcium carbonate decomposes into lime and carbon dioxide gas. The carbon dioxide gas produced escapes from the lime kiln leaving behind lime.

The diagram of the lime kiln used for the decomposition of calcium carbonate is shown in figure to manufacture lime calcium carbonate is fed into the lime kiln through the hopper situated at the upper end of the lime kiln. The calcium carbonate in the lime kiln is then heated by passing in hot air from the sides of the lime kiln, due to which calcium carbonate decomposes into lime and carbon dioxide. The lime produced is then collected at the bottom of the lime kiln and carbon dioxide produced during the decomposition of calcium carbonate is allowed to escape from the lime kiln.

Properties of Lime

1. Lime is a white solid having very high melting point of 2273 K.
2. When lime is heated in oxy-hydrogen flame, it produces brilliant white light called ‘lime light’.
3. When lime is added in water then it produces a hissing sound and forms slaked lime. This reaction is exothermic in nature.
4. Slaking of Lime:- When lime is added into water then a sound of hissing is produced along with heat and it cracks to form a white powder. This white powder is actually calcium hydroxide which is also called slaked lime.
5. Lime is very stable which means that it doesn’t decompose easily even at high temperatures.
6. Lime can react with moist hydrogen chloride gas to form calcium chloride.

Uses of Lime

1. Lime is used in white washing the buildings and houses.
2. It is used in manufacture of many other important compounds such as glass, cement, calcium chloride and calcium nitrate.
3. It is used in the extraction of iron from its ore haematite.
4. It is used as drying agent for drying gases and alcohol.
5. It is also used in tanning industry.
6. It is also used in manufacture of sodium carbonate, bleaching powder and calcium carbide.
7. It is used as a basic lining in furnaces.

Test your understanding and answer these questions:

1. What is chemical name and formula of quick lime?
2. How quicklime is manufactured?
3. What are uses of quick lime?