. Answer the following questions


a. Answer the following questions:

i. Name a metal which is found abundantly in the Earth's crust.

ii. What is the difference between calcination and roasting?

iii. Name the process used for the enrichment of sulphide ore.

iv. Write the chemical formula of one main ore of iron and aluminium.

v. Write the constituents of the electrolyte for the extraction of aluminium.

 

Best Answer

a. 

i. A metal which is found abundantly in the Earth's crust is Aluminium

ii. Differences between calcination and roasting:

Calcination Roasting
1. The ore is heated in the absence of air. 1. The ore is heated in excess of air.
2. Moisture and organic impurities are removed and the ore becomes porous and more reactive. 2. Volatile impurities are removed as oxides (S02, P205, AS203) and the ore becomes porous and more reactive.
3. Carbonate and hydrated ores are calcined and C02 or water vapour is given off. Znoo3 → Zno + oo2 3. Sulphide ores are roasted, so S02 is given off. 2znS+3O2 800° to 900°C →2ZnO+2SO2

iv. Ores of iron

Name Chemical name Formula
Red Haematite
Anhydrous oxide ferric
Fe2O3
Brown Haematite Hydrated ferric oxide 2Fe2O3.3H2O

Ores of aluminum

Name Chemical name Formula
Bauxite
Hydrated aluminium oxide
Al3O32H2O
Cryolite
Sodium oxide aluminium
Na3AlF6

v. Constituents of the electrolyte for the extraction of aluminium are pure alumina (Al3O3), cryolite (Na3AlF6) and fluorspar (CaF2).

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