Extraction of Metals at the middle of the activity Series of Medium Reactivity

Extraction of Metals (At the middle of the activity Series) of Medium Reactivity:

The metals in the middle of the activity series as iron, zinc, lead, copper etc. are moderately reactive. These metals are usually present as sulphides or carbonates in nature. These sulphides or carbonates are first converted into oxides because it is easy to exact metals from its oxide. Sulphides are converted into oxides by roasting and carbonates are converted into oxides by calcinations. The metal oxides thus obtained are then reduced to the corresponding metals by reduction using suitable reducing agents such as carbon. Chemical Reactions involved in the extraction of zinc are as follows:

Roasting: It is the process in which sulphide ore is heated below its melting point in the presence of air to convert it into metal oxide. Sulphur impurities escape as gas.e.g.

$large 2ZnS+3O_2rightarrow 2ZnO + 2SO_2$

Calcination: It is the process in which carbonate ore is heated below its melting point in the absence of air to convert it into metal oxide. For eg:

$large 2ZnCO_3rightarrow 2ZnO + CO_2$

Reduction of oxide: It is the process of conversion of metal oxide ore into metal. It can be done by heating the oxides.Sometimes displacement reactions can also be used to reduce metal oxide.

The highly reactive metals such as sodium, calcium, aluminum etc, are used as reducing agents because they can displace metals of lower reactivity from their compounds, e.g. reaction of manganese dioxide with aluminum powder.

$large 3MnO_2+4Alrightarrow 3Mn + 2Al_2O_3+ Heat$

These displacement reactions are highly exothermic. The amount of heat produced is so high that the metals are produced in the molten state.The reaction of iron (III) oxide () with aluminum to produce iron is used to join railway tracks or cracked machine parts. This process is called thermite welding.

$large Fe_2O_3+2Alrightarrow 2Fe +Al_2O_3+Heat$

This reaction of metal oxide to form metal by using aluminum powder as a reducing agent is known as thermite reaction. The mixture of iron oxide and aluminium powder is called thermite.

Sample Questions

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Question : 1

Which of the following are correct : (a) Sulphides are converted into oxides by roasting. (b) Carbonates are converted into oxides by calcinations. (c) The highly reactive metals such as sodium, calcium, aluminum etc, are used as reducing agents.
A. Only (a) and (b) are correct.	B. Only (b) and (c) are correct.	C. Only (a) and (c) are correct.	D. All of these.
Right Option : D
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