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Ores: The minerals from which metals are extracted profitably and conveniently are called ores. 

Examples: Bauxite (Al₂O₃.H₂O), Cinnabar (HgS).

Metallurgy: The process used for extraction of metals in their pure form from their ores, then metals are further purified by different methods of purification. All the process is called metallurgy.

(1) Bauxite – Aluminium

(2) Cassiterite – Tin

(3) Cinnabar – Mercury

Gold and Platinum are the two metals that occur in the free or native state. The metallic compounds which occur in : 

1. Halides – Cryolite[Na₃AlF₆ ], Flurospar[CaF₂ ], Rock Salt[NaCl] 

2. Oxides – Bauxite[Al₂O₃ .2H₂O], Zincite[ZnO], Cuprite[Cu₂O] 

3. Sulphides – Iron Pyrite[FeS₂ ], Zinc blende[ZnS], Gdlena[PbS]

(a) treatment of the ore with water and pine oil

An example of an oxide ore is bauxite

(d) Al₂O₃ .2H₂O

1. Ores 

2. Ellingham diagram 

3. negative 

4. Cu₂O 

5. Hydraulic washing 

6. oxide

 7. Sodium ethyl xanthate

8. Na₂[Zn(CN)₄] – Sodium negative 

9. Cementation 

10. Redox

Brine is a solution of sodium chloride (molten state): The process of electrolysis involves using an electric current to bring about a chemical change and make new chemicals. In the electrolysis of brine, sodium ions migrate to the cathode, where electrons enter the melt and are reduced to sodium metal.

Na + e → Na (at cathode)

Chloride ions migrate the other way toward the anode. They give up their electrons to the anode and are oxidised to chlorine gas.

Cl^- → \(\frac{1}{2}\)Cl₂ + e^- (at node)

Overall reaction: 

2NaCl → 2Na(s) + Cl₂ (g)

For aqueous solution of NaCl:

• H₂O + 2e^- → H₂↑ + 2OH^- (at cathode)
• Cl^- → \(\frac{1}{2}\) Cl₂ + e^- (at anode)

Overall reaction: 

NaCl (aq) + H₂O(1) → Na⁺(aq) + OH^- (aq) + H₂(g) + \(\frac{1}{2}\)Cl₂(g) 

After electrolysis the electrolytic solution becomes basic in nature. [Due to formation of hydroxide (OH^-) ion].

This method is very useful for producing semiconductor and other metals of very highpurity, e.g, germanium, silicon, boron, gallium and indium.

In this method, the metal is converted into its volatile compound and collected elsewhere. It is then decomposed to give pure metal.

• Common salt is an ionic compound. Common salt is solid and hard due to strong electrostatic attraction between oppositely charged Na+ and Cl- ions.
• A large amount of energy is required to break the strong intermolecular attraction (strong ionic bond). Hence, common salt has high melting and boiling points.

(c) A – (iv), B – (ii), C – (iii), D – (i)

(b) Copper pyrite – froth floatation process

(d) Electromagnetic separation

(b) Cu(s) + Zn²⁺ +(aq) → Zn(s) + Cu²⁺(aq)

(b) The graph for the fonnation of CO₂ is a straight line almost parallel to free energy axis.

(b) ∆G° Vs T

(b) Al₂O₃ → Cr₂O₃ + 2Al 

(c)  \(\Big(\frac{\Delta\,G^0}{\Delta\,T}\Big)\)is negative

(a) Silver ore – Acid leaching

During the purification of Nickel by Mond’s process, carbon monoxide (CO) is used to convert impure nickel to nickel carbonyl. Nickel carbonyl is an unstable compound. Heating to higher temperature decomposes it to give pure nickel.

1. The role of silica in the extraction of copper is to remove the iron oxide obtained during the process of roasting as slag. If the sulphide ore of copper contains iron, the silica (SiO₂) is added as flux before roasting. Then, FeO combines with silica to form iron silicate, FeSiO₃(Slag).

2. Cryolite reduces the melting point of Al₂O₃ and increases its electrical conductivity. Aluminium is produced by the electrolytic reduction of fused alumina in the electrolytic cell. Alumina is not an electrolyte. So it is made as an electrolyte by dissolving it in the fused cryolite. The function of cryolite is to lower the fusion temperature.

3. Zirconium crude metal is heated with iodine in an evacuated vapour to separate from impurities and this decomposes at 1800 K to give a pure zirconium metal and iodine. Initially iodine is heated with zirconium to form a volatile compound.

4. Sulphide ores which are concentrated by the froth floatation process. Depressants are used to prevent certain type of particles from forming the froth. NaCN act as a depressant to separate ZnS from PbS.

Applications of Zinc (Zn): 

1. Metallic zinc is used in galvanising metals such as iron and steel structures to protect them from rusting and corrosion. 

2. Zinc is also used to produce die-castings in the automobile, electrical and hardware industries. 

3. Zinc oxide is used in the manufacture of many products such as paints, rubber, cosmetics, pharmaceuticals, plastics, inks, batteries, textiles arid electrical equipment. Zinc sulphide is used in making luminous paints, fluorescent lights and x-ray screens. 

4. Brass an alloy of zinc is used in water valves and communication equipment as it is highly resistant to corrosion.

Electrochemical extraction of aluminium Hall-Herold process: 

In this method, electrolysis is carried out in an iron tank lined with carbon, which acts as a cathode. The carbon blocks immersed in the electrolyte acts as a anode. A 20% solution of alumina, obtained from the . bauxite ore is mixed with molten cyrolite and is taken in the electrolysis chamber. About 10%, calcium chloride is also added to the solution. Here calcium chloride helps to lower the melting point of the mixture. The fused mixture is maintained at a temperature of above 1270 K. 

The chemical reactions involved in this process are as follows:

Ionisation of alumina: 

Al₂O₃ → 2Al₃ + 3OO^2-

Reaction at cathode: 

2Al³⁺ (melt) + 3e^- → Al_(l)

Reaction at anode: 

2O^2- (melt) → O₂ + 3e^-

Since carbon acts as anode the following reaction also takes place on it.

C (s) + O^2- (melt) → CO + 2e^-

C (s) + 2O^2- (melt) → CO₂ + 4e^-

Due to the above two reactions, anodes are slowly consumed during the electrolysis. The pure aluminium is formed at the cathode and settles at the bottom. The net electrolysis reaction can be written as follows:

4Al³⁺ (melt) + 6O^2- (melt) + 3C_(s) → 4A_(I) + 3CO_2(g)