Introduction to Copper

Copper

Details about copper are given below:

Ores of copper

Malachite → Cu(OH)₂.CuCO₃

Copper-iron pyrite → CuFeS₂

Copper glance → Cu₂S

Cuprite → Cu₂O

Extraction of copper

Copper is mainly extracted from sulphide ore i.e. Copper iron pyrite (CuFeS₂) in following steps.

1. Concentration: The ore is first crushed into pieces and then powdered which is then mixed with water along with pine oil in a large tank and agitated by blowing air. The sulphide ores come to the surface along with froth and impurities settle down.
2. Roasting: The concentrated ore is strongly heated in the presence of air in the reverberatory furnace. This process helps to remove out impurities like phosphorus, sulphur, arsenic etc in the form of volatile oxide.

$$S+O_2\longrightarrow SO_2$$

$$4P+5O_2\longrightarrow 2P_2O_5$$

$$4As+3O_2\longrightarrow 2As_2O_3$$

The copper iron pyrite reacts with air to form cuprous sulphide and iron sulphide and later on the compound are further oxidized to their oxides.

$$2CuFeS_2+O_2\longrightarrow Cu_2S+2FeS+SO_2$$

$$2Cu_2S+3O_2\longrightarrow 2Cu_2O+2SO_2$$

$$2FeS+3O_2\longrightarrow 2FeO+2SO_2$$

• Smelting: the roasted ore is mixed with coke(C) and sand (SiO₂) and then it is heated strongly in the blast furnace. The coke burns and this leads to a temperature of 1273 K. the formed FeO combines with SiO₂ to give easily fusible silicate slag.

$$FeO+SiO_2\longrightarrow FeSiO_3$$

The copper oxide is also converted into copper sulphide.

$$Cu_2O+FeS\longrightarrow Cu_2S+FeO$$

The molten mass below the slag consists of the mixture of the sulphide of copper and iron known as matte.

• Basemerization:

The molten matter is mixed with silica and a blast of hot air is introduced into Bessemer converter and fine sand is also introduced then the following reaction occurs.

$$Cu_2S+3O_2\longrightarrow 3Cu_2O+2SO_2$$

$$2FeS+3O_2\longrightarrow 2FeO+2SO_2$$

$$FeO+SiO_2\longrightarrow FeSiO_3$$

When whole iron is removed the slag thus formed is removed and then cuprous sulphide reacts with cuprous oxide to form copper.

$$Cu_2S+Cu_2O\longrightarrow 6Cu+SO_2$$

The molten mass is then cooled. Then it slowly gives dissolved the SO₂ gas in the form of bubbles. So, the copper thus formed is also known as blister copper.

• Purification: purification is done by electrolysis method in which blister copper is taken as the anode and is placed in acidified copper sulphate(CuSO₄) solution and pure copper is taken as the cathode. On passing current pure copper is deposited at the cathode and the impurities are collected at the bottom of the anode as an anode mud.

Chemical properties of copper

• Action with air: copper when exposed to moist air forms a green colored compound due to the formation of basic carbonate of copper.

$$Cu+H_2O+CO_2+O_2\longrightarrow Cu(OH)_2.CO_3$$

On heating with air below 1100 cupric oxide is formed and above 1100 cuprous oxide is formed.

$$4Cu+O_2\longrightarrow 2Cu_2O (on\space heating\space with\space air\space below\space 1100)$$

$$2Cu+O_2\longrightarrow 2CuO (on\space heating\space with\space air\space above\space 1100)$$

• Action with acid

1. With nitric acid (HNO₃): Moderately concentrated nitric acid gives nitric oxide gas whereas concentrated nitric acid gives nitrogen dioxide gas.

$$8HNO_3+3Cu\longrightarrow 3Cu(NO_3)_2+2NO+H_2O (with\space moderately\space concentrated\space HNO_3)$$

$$4HNO_3+Cu\longrightarrow Cu(NO_3)_2+2NO_2+H_2O(with\space concentrated\space HNO_3)$$

1. With sulphuric acid (H₂SO₄): Copper react with the sulphuric acid in the presence of air to form copper sulphate.

$$2Cu+2H_2SO_4+O_2\longrightarrow 2CuSO_4+2H_2O (with\space dil.\space H_2SO_4)$$

$$Cu+2H_2SO_4\longrightarrow Cuso_4+2H_2O+SO_2 (with\space conc.\space H_2SO_4)$$

2. With hydrochloric acid: copper react with hydrochloric acid in the presence of air to form CuCl₂.

$$2Cu+4HCl+O_2\longrightarrow 2CuCl_2+2H_2O$$

• Displacement reaction: copper displaces less electropositive metal like Ag, Pt, Au from their salt.

$$Cu+2AgNO_3\longrightarrow Cu(NO_3)_2+2Ag$$

Uses of copper

• Used for making conducting wire.
• Used for making utensils.
• Used for making alloys like brass {Cu + Zn}, bronze [Cu +Sn}.
• Corrosive resistant: Copper is low in the reactivity series. This means that it doesn't corrode. It is used for pipes, electrical cables, and radiators.
• As jewelry: It also means that it is well suited to decorative use. Jewelry, statues and parts of buildings can be made from copper, brass or bronze and remain attractive for thousands of years.
• Anti-bacterial: Copper is a naturally hygienic metal that slows down the growth of germs such as E-coli, MRSA (the hospital “superbug”).
• This is important for applications such as food preparation, hospitals, coins, doorknobs and plumbing systems.

Reference

poulse, tracy. Introduction to chemistry.u.s.a: flexbook, 2010.

Pathak, Sita Karki. The Text Book of Chemistry. Kathmandu: Vidhyarthi Pustak Bhandar, 2012.