Page 224 - Chemistry ICSE Class X

210 ICSE Chemistry – 10

— Calcination. Heating of an ore strongly in limited air below its melting point is called calcination.
— Roasting. The process of heating an ore strongly below its melting point but in the presence of excess air is called
roasting.
— Reduction of metal oxides. The metal oxide present in a calcined /roasted ore is reduced to metal by using a suitable
reducing agent. The choice of the reducing agent depends upon the reactivity of the metal.
 The oxides of moderately reactive metals, such as Fe, Zn, Cu, Ni and Sn, which appear in the middle of the reactivity
series, are reduced by heating with carbon.
 The oxides of metals which react with carbon are reduced by using aluminium powder. Aluminium is used for reducing
manganese dioxide (MnO ) to manganese, iron oxide (Fe O ) to iron and chromium oxide (Cr O ) to chromium.
2 2 3 2 3
 Hydroxides, oxides and halides of highly reactive metals, such as sodium, potassium, magnesium and aluminium, etc.
are reduced to the respective metals by electrolytic reduction method.
— Refining of metals. The process of removing impurities from the metals extracted from their ores is called refining of
metals.
 Metals having low melting points, such as tin, lead, bismuth, etc. are refined by liquation method.
 Most metals are refined by electrolytic method.
 More volatile metals, such as mercury and zinc, are purified by distillation method.
— Extraction of aluminium. Aluminium is extracted from alumina by electrolysing a molten mixture of alumina (20%),
cryolite (60%), and fluorspar (20%).
 The extracted aluminium is purified by electrolytic method.
 Aluminium is used for making electrical wires, domestic utensils, foil for packaging of food materials, and for making
many useful alloys.
— Alloys. A homogenous mixture of a metal with another metal or with a nonmetal is called alloy.
 Alloys of copper – Brass, Bronze, Gun metal, Bell metal
 Alloys of iron – Stainless steel, Nickel steel
 Alloys of aluminium – Duralumin, Magnalium
 Alloys of lead – Solder, Type metal