. 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.
i. A metal which is found abundantly in the Earth's crust is Aluminium
ii. Differences between calcination and 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
Anhydrous oxide ferric
|Brown Haematite||Hydrated ferric oxide||2Fe2O3.3H2O|
Ores of aluminum
Hydrated aluminium oxide
Sodium oxide aluminium
v. Constituents of the electrolyte for the extraction of aluminium are pure alumina (Al3O3), cryolite (Na3AlF6) and fluorspar (CaF2).