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In which of the following cases flux is ...

In which of the following cases flux is required?
(i) In the smelting of roasted zinc blende
(ii) In the extraction of iron from haematite in the blast furnace. Explain. Mention the name of the flux with the purpose it serves where it is required.

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Flux is required in the extraction of iron from haematite. Limestone `(CaCO_3)` is used as flux. On heating, it decomposes into quicklime (CaO) and carbon dioxide.
The quicklime produced reacts at high temperature with silicious impurities of the ore to form calcium silicate as an easily fusible slag.
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