2 Chemistry -- Heavy Metals: Copper

how is metal copper extracted from its pyrite ore?

1 Answers

It can be extracted from copper pyrite which goes through the following step:

1. Crushing and pulverization: The big size of the ore is crushed and it is changed into a fine powder then it is taken for concentration.

2. Concentration: The obtained powder ore is concentrated by the froth floatation process. Then it is taken for roasting.

3. Roasting: It is then heated strongly in a reverberatory furnace. The volatile impurities such as sulphur, arsenic, etc are removed and pyrite ore is converted into a mixture of cuprous sulphide, iron sulphide and ferrous oxide.

4. Smelting: The obtained ore is mixed with sand and coke then it is heated in a blast furnace then ferrous sulphide is oxidized to give ferrous oxide which combines with SiO2 (sand) to give the fusible silicate slag.

Thus, obtained fusible slag is removed.

Then, cuprous oxide again reacts with carbon (coke) to give few amounts of copper and again it reacts with ferrous sulphide to give cuprous sulphide.

The lower layer is molten mass containing about 40-50% of metal, Cu2S, and some trash amount of FeS is called matte (molten matte) which is transferred to a Bessemer converter for Bessemerization.

5. Bessemerization: The obtained matte is heated. Then FeS (ferrous sulphide) is oxidized to give ferrous oxide. It again reacts with SiO2 to give fusible slag.

Here, the total FeS (fusible slag) is removed.

Then, cuprous sulphide begins to be oxidized. When about two-thirds of the Cu2S is oxidized then the oxide of copper reacts with the remaining Cu2S to give copper and sulphur dioxide.

Then, molten mass is cooled then dissolved SO2 gas is obtained in the form of a bubble. This gives the shape of a blister to the surface of solidified copper. For this reason, it is also called blister copper which contains 2% impurities like Ag, Ni, Zn, etc. Then it is taken for purification.

6. Purification (Electrolytic refining): For this, a thin sheet of impure crude metal is made anode and the thin sheet of another metal (sheet) is made the cathode. Both are replaced in acidified copper sulphate solution when an electric current is passed then impure copper from the anode goes into the solution and then pure copper from the solution gets deposited at the cathode and impurities are collected below the anode.

Why is calcium carbide mixed with sand?

Calcium carbide ( $C a C_{2}$ ) reacts with water to produce acetylene ( $C_{2} H_{2}$ ):

$C a C_{2} (s) + 2 H_{2} O (g) C a (O H)_{2} (s) + C_{2} H_{2} (g)$

When it is used to produce acetylene, however, it is mixed with sand because the reaction between CaC and HO is quite exothermic and this causes two issues:

the as-produced acetylene is very flammable;
the Ca(OH) byproduct.

Both can be circumvented by adding sand to the reaction mixture in order to absorb the heat excess and let calcium hydroxide react with it to form calcium...

Why is the froth flotation method selected for the concentration of sulphide ores?

The surface of sulphide ores is preferentially wetted by heavy oils like turpentine or pine oil while the gangue is wetted by water hence, froth floatation method is selected for concentration of sulphide ores.

What is the composition of ‘Copper matte’?

Copper sulphide contains some amount of iron sulphide as impurities which is called copper matte.
Copper matte mainly consists of cuprous sulphide and little ferrous sulphide.

How is blister copper obtained from copper pyrite?

The molten mass of copper is cooled then dissolved SO2 gas is obtained in the form of a bubble. This gives the shape of a blister to the surface of solidified copper. For this reason, it is also called blister copper which contains 2% impurities like Ag, Ni, Zn, etc. Then it is taken for purification.

Write a note highlighting the important fact about the chemistry of blue vitriol.

USES OF BLUE VITROL

Antiseptic agent

In electroplating processes.

Antifungal agent for topical use

Treatment of copper deficiency

Etching - Copper sulfate is also used to etch zinc plates for intaglio printmaking.

Dyes - Copper sulfate can also be used as a mordant in vegetable dyeing. It often highlights the green tints of the specific dyes.

Copper sulfate is used to test blood for anemia. The blood is tested by dropping it into a solution of copper sulfate of known specific gravity.

Copper sulfate...

Write the action of it upon I)moist air II) conc. H₂SO

i. Action with moist air: After long exposure to moist air, a green layer of its basic carbonate is formed over it.

2Cu + H₂O + CO₂ + O₂ ---------------> CuCO₃.Cu(OH)₂

ii. Action of Conc. H₂SO₄: When heated with conc.H₂SO₄Sulphur dioxide gas is formed.

Cu + 2H₂SO₄-------------------> Cu(NO₃)₂ + 2NO₂ + 2H₂O

When caustic soda is added to an aqueous solution of copper sulphate, a blue precipitate of Cu(OH)2 is obtained. How will you separate Cu(OH)2 from the mixture ?

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