Metals & Non-metals

Metals low in activity series

Extraction of Metals Low in the Activity Series

Metals falling in low reactivity series are found in free states or in the form of sulphides ores in nature.

The ores which are found in the form of sulphide are first heated in the presence of oxygen. By heating sulphides are converted into oxides of metals and sulphur is separted out in the form of sulphur dioxide gas. This process is called roasting.

Roasted ore in then heated again. Heating of roasted ores is called reduction. The oxides of metals are reduced to metals in this process of reduction.

Example:

Extraction of Mercury

Cinnabar (HgS) which is an ore of mercury, found as sulphide of mercury. Cinnabar is first heated in the presence of air. This roasting converts cinnabar into mercury oxide. Then oxide of mercury is heated to reduce into mercury metal.

When cinnabar (mercury sulphide) is heated in the presence of air, it is converted into mercury oxide. And when mercury oxide is heated, it gives mercury metal.

The mercury (II) oxide obtained after roasting is heated again strongly which turns mercury (II) oxide into mercury metal.

Extraction of copper

Copper is found in the form of its sulphide. This ore of copper is called Copper glance (Cu₂S). Copper glance is heated in the presence of air. This process of heating in the presence of air is called roasting. This roasting converts copper glance into copper (I) oxide.

Copper (I) oxide so obtained is further reduced to copper metal by heating.

Extraction of Metals in the Middle of the Activity Series

Metals fall in the middle of the reactivity series are moderately reactive, i.e. more reactive than metals fall in the low reactivity series.

Example: Iron, zinc, lead, etc. are moderately reactive and falls in the middle of the reactivity series.

Metals fall in the middle of the reactivity series are found in the form of their sulphides or carbonates in the nature.

Roasting of Sulphide ores

Ores of metals found in the form of Sulphide are first roasted to convert them into respective oxides.

Calcination of Carbonate Ores

Ores of metals found in the form of carbonates are first heated in the presence of limited air to convert them into their respective oxides. This process is called calcinations.

Reduction

Oxides of metals which are obtained after roasting or calcination are then reduced to their respective metals by heating. This process is called reduction.

Example:

Extraction of Zinc metal

Zinc metal is found in the form of zinc blende [ZnS (Zinc sulphide)] and in the form of Calamine [Zn(CO)₃(Zinc carbonate)].

Extraction of zinc metal from Zinc Blende Ore

Roasting of Zinc Blende

Zinc blende [ZnS (Zinc sulphide)] first converted into zinc oxide by the process of roasting. In the process of roasting, zinc blende [ZnS (Zinc sulphide)] is heated strongly in the presence of excess of air, i.e. oxygen, this converts zinc blende into zinc oxide.

Calcination of Calamine Ore

Calamine [Zn(CO)₃(Zinc carbonate)] is heated in the presence of limited air. This convert calamine into zinc carbonate [Zn(CO)₃]. This process is called calcinations of calamine.

Reduction of Zinc Oxide to obtain zinc metal

Zinc oxide obtained after the process of roasting or calcinations is reduced to zinc metal. In this process, zinc oxide is heated with a reducing agent, such as carbon to convert zinc oxide into zinc metal.

Reduction of metals oxide to respective metal by using reducing agent other than carbon (coke)

Apart from carbon (coke) many other reducing agents are used to obtain metal from respective oxides. Many times displacement reaction is used to obtain metals from respective oxides. In displacement reaction more reactive metals displaces less reactive metals for their compounds. In displacement reactions, highly reactive metals, such as sodium, calcium, alumininium, etc. are used as reducing agent.

Example:

Reduction of Manganese dioxide (MnO₂) to Manganese

When manganese dioxide is heated with aluminium metal, aluminium, which is more reactive than manganese, displaces manganese from manganese dioxide and gives manganese.

In this reaction manganese oxide is reduced to manganese metal and aluminium is oxidized to aluminium oxide.

This process is highly exothermic. In these types of displacement reaction amount of heat evolved is so large that the metal produced in such reactions is in molten state.

Thermit Reaction

When ferric oxide [Iron (III) oxide] is heated with aluminium metal, iron (III) oxide is reduced to iron metal.

In this reaction iron (III) oxide is reduced to iron metal and aluminium is oxidized to aluminium oxide. In this reaction also heat produced is so large that iron metal is obtained in the form of molten state.

This reaction is known as Thermit Reaction.

Thermit reaction is used in joining of railway tracks or cracks in machine parts.

Reduction of copper oxide with aluminium

Copper oxide when heated with aluminium, it is reduced to copper metal and gives lot of heat.

Since, in this reaction also huge amount of heat is produced, thus copper oxide is also used instead of ferric oxide for thermit welding, i.e. joining of railway track or cracks in machines.