Write the names and formulae of two ores of iron.

The mineral from which the metal can be extracted economically and conveniently is called an ore. The two important ores of iron are haematite ( Fe 2 O 3 ) and magnetite ( Fe 3 O 4 ).

How will you extract zinc from zinc blende? Give all the equations involved.

The different steps involved in the extraction of zinc from zinc blende ( ZnS ) are given below: (i) Concentration of ore: The gangue from zinc blende is removed by the froth floatation method. (ii) Conversion to oxide by roasting: Sulphide ore is converted into oxide by the process of roasting. In this process, ZnS is heated in a regular supply of air in a furnace at a temperature, which is below the melting point of zinc. Zinc sulphide is oxidised to zinc oxide. 2 ZnS + 3 O 2 → 2 ZnO + 2 SO 2 (iii) Extraction of zinc from zinc oxide: Zinc is extracted from zinc oxide by the process of reduction using coke. For the purpose of heating, the oxide is made into brickettes with coke and clay. ZnO + C → coke , 1673 K Zn + CO The metal is distilled off and collected by rapid chilling.

State with equations how you will obtain ‘blister’ copper from copper ‘matte’?

The molten mixture of cuprous sulphide and traces of unconverted ferrous sulphide obtained in the smelting process is called copper 'matte'. Then the molten matte is transferred to a silica lined Bessemer converter. A blast of hot air mixed with sand is blown through the molten mass. The last traces of ferrous sulphide is converted to slag. 2 FeS + 3 O 2 → 2 FeO + 2 SO 2 FeO + Si O 2 → FeSiO 3 About two thirds of cuprous sulphide is oxidised by air to give cuprous oxide. This cuprous oxide reacts with the remaining cuprous sulphide to form molten copper. 2 Cu 2 S + 3 O 2 → 2 Cu 2 O + 2 SO 2 Cu 2 S + 2 Cu 2 O → 6 Cu + SO 2 The molten copper is poured into moulds. When it is allowed to cool, sulphur dioxide gas escapes from the surface causing blisters. Hence, it is known as blister copper.

Define roasting of ores. For what type of ores is it used?

Roasting is a process in which the ores are heated to a high temperature below their melting point in the presence of excess of air. During this process, the moisture escapes and the impurities like sulphur, arsenic, phosphorous, etc. are oxidised to their volatile oxides. This method is used to convert the sulphide ores into their oxides.

Discuss the process of leaching with reference to the extraction of aluminium.

The principal ore of aluminium is bauxite Al 2 O 3 . It contains SiO 2 , iron oxides and titanium oxides as impurities. The process of leaching in the extraction of aluminium from bauxite is to remove these impurities from the ore.

Why are metallic ores converted into oxide usually?

The metallic ores are converted to oxide because it is easy to displace oxygen from metal oxide than to displace sulphur or chlorine from the sulphides or chlorides.

What is the principle of zone refining?

Zone refining method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal. Therefore, an impure metal on solidification will deposit crystals of pure metal and the impurities will remain behind in the molten part of the metal.

How would you convert pig iron into cast iron?

The iron obtained from blast furnace contains about 4 % carbon and many impurities like S , P , Si , Mn in smaller amount is called pig iron. When pig iron is melted and mixed with scrap iron and coke using hot air blast, it forms cast iron, which contains about 3 % carbon.

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