Question

Write the difference between calcination and roasting

Answer 1

Answer:

Calcination is done for carbonate ores in the presence of limited air whereas roasting is done for sulphide ores with provision of excess air.

Answer 2

Ways to Obtain Metals of middle reactivity from their respective ores

Metals of middle reactivity generally form carbonate and sulphide ores. There are different ways for both.

1. Carbonate Ore:

Taking the example of Zinc Carbonate (ZnCO₃),

1. It is heated in limited air to obtain Zinc Oxide (ZnO) and CO₂.
2. Then, the metal oxide is reduced using a reducing agent like Carbon, Carbon-monoxide, or a highly reactive metal like Al.

2. Sulphide Ore:

Taking the example of Zinc Sulphide (ZnS),

1. It is first heated in excess of air to form ZnO and SO₂.
2. Then, it is, just like in the previous case, reduced using a reducing agent.

The Answer:

1. * Calcination is defined as heating of a carbonate ore in limited air to obtain metallic oxide.

Roasting is defined as heating of a sulphide ore in excess of air to obtain metallic oxide.

2. * Calcination is done for Carbonate ore.

Roasting is done for sulphide ore.

3. * Carbonate ores are heated in limited air because it already has oxygen present in it while sulphide ores are heated in excess of air because they lack oxygen.