Metallurgical operations-Step 3 - Reduction of oxide(Pyrometallurgy of copper; Hydrometallurgy of copper)

Question 1

How is copper pyrites converted to copper oxide?

Answer 1

The sulphide ores are roasted to give oxides:

2Cu2S + 3O2 → 2Cu2O + 2SO2

Question 2

What is copper matte?

Answer 2

It contains Cu2S and FeS.

Question 3

State the role of silica in the metallurgy of copper.

Answer 3

Silica is the acidic flux added to remove basic gangue FeO.
FeO + SiO2 → FeSiO3
(Slag)

Question 4

Write the reactions that happen in the convertor in the metallurgy of copper

Answer 4

Copper matte is charged into silica lined convertor. Some silica is also added and hot air blast is blown to convert the remaining and hot air blast is blown to convert the remaining FeS2, FeO and Cu2S/Cu2O to the metallic copper. 
Following reactions take place:
2FeS + 3O2 → 2FeO + 2SO2 (6.37)
FeO + SiO2 → FeSiO3 (6.38)
2Cu2S + 3O2 → 2Cu2O + 2SO2 (6.39)
2Cu2O + Cu2S → 6Cu + SO2

Question 5

What is auto reduction?

Answer 5

It is a process in which sulphide ores of less electropositive metals like Hg, Pb, Cu etc., are heated in air so as to convert part of the ore into oxide which then reacts with the remaining of sulphide ore in absence of air to give the metal and sulphur dioxide. Since no external reducing agent is used in this process that is why it is referred as auto reduction.
2Cu2O + Cu2S → 6Cu + SO2

Question 6

What is blister copper?

Answer 6

The solidified copper obtained after auto reduction has blistered appearance due to the evolution of SO2 and so it is called blister copper.

Question 7

What is hydrometallurgy?

Answer 7

The process of extraction of metals by dissolving the ore in a suitable reagent followed by displacement of the metal by a more reactive metal

Question 8

When is hydrometallurgy used for obtaining copper?

Answer 8

Copper is extracted by hydrometallurgy from low grade ores. It is leached out using acid or bacteria. The solution containing Cu2+ is treated with
scrap iron or H2
Cu2+(aq) + H2(g) → Cu(s) + 2H+ (aq)

Question 9

Name the sulphide ore of copper

Answer 9

copper pyrites-CuFeS2

copper glance- Cu2S

Question 10

Name the carbonate ore of copper

Answer 10

malachite- CuCo3.Cu(OH)2

Question 11

Name the oxide ore of copper

Answer 11

Cuprite-Cu2O