ICSE Class 10 Answered

Why are carbonate ores are calcined while sulphide ores are roasted?

Asked by pb_ckt | 20 Mar, 2019, 01:29: PM

Expert Answer

Roasting: It is the process in which a sulphide ore is strongly heated in the presence of air to convert it into a metal oxide.

This is done in case of sulphide ores so as to remove sulphur in the form of SO₂ and to obtained corresponding metal oxide.

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But, in the case of carbonate ores, we need to eliminate the carbonate and moisture. this is done by calcination.

Calcination: It is the process in which a carbonate ore is heated strongly in the absence of air to convert it into a metal oxide.

When zinc carbonate is heated strongly in the absence of air, it decomposes to form zinc oxide and carbon dioxide

ZnCO subscript 3 left parenthesis straight s right parenthesis end subscript space space rightwards arrow with 400 to the power of degree straight C on top space space space ZnO subscript left parenthesis straight s right parenthesis end subscript space plus space CO subscript 2 left parenthesis straight g right parenthesis end subscript

So, roasting is not done for carbonate ores, moreover, calcination is more difficult than roasting.

It is easier to obtain metals from their oxides (by reduction) than from carbonates or sulphides.

So before reduction can be done, the ore is converted into metal oxide.

Answered by Ramandeep | 20 Mar, 2019, 02:52: PM

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