Which one of the following reactions does not occur during extraction of copper?

Solution

Chemistry ma’am · 3 steps

Copper's impurity is basic FeO, so its flux is acidic silica. Lime as a flux belongs to iron, not copper.

1. Know the impurity. Copper comes from copper pyrites, CuFeS₂, so iron is the main impurity. Roasting and smelting oxidise iron sulphide to FeO, which is a basic oxide.
2. Choose the flux. A basic impurity needs an acidic flux, so silica is added and FeO leaves as the slag FeSiO₃. Lime (CaO) is a basic flux. It is used in the iron blast furnace to remove silica, so it has no job in copper extraction.

   Reaction	Where it happens	In copper extraction?
   2FeS + 3O₂ → 2FeO + 2SO₂	Roasting and smelting: iron sulphide turned into oxide	Yes
   FeO + SiO₂ → FeSiO₃	Smelting: silica flux removes iron as slag	Yes
   CaO + SiO₂ → CaSiO₃	Iron blast furnace: lime flux removes silica	No
   2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂	Converter: partial oxidation before self-reduction, 2Cu₂O + Cu₂S → 6Cu + SO₂	Yes

3. So. The reaction that does not occur in copper extraction is CaO + SiO₂ → CaSiO₃, option (c).

The idea to keep. Pick the flux from the impurity. A basic impurity like FeO needs acidic silica (copper). An acidic impurity like SiO₂ needs basic CaO (iron).

Answer from the NTA final answer key. Solution by PrepWiser.