Discuss some of the factors which need consideration before deciding on the method of extraction of metal from its ore.

Explanation

Some of the factors which need consideration before deciding of extraction of metal from its ore are (i) type of impurity, (ii) the type of metal, (iii) available facility.
(i) Type of impurity : The ore is concentrated by the method depending on the type of impurity.
(a) Hand picking : In some cases, the ore and the impurities differ in the size and the shapes of the particles. The impurities can be removed mechanically by simply hand picking.
(b) Gravity separation : This process of concentration is done in these cases in which the gaugue impurities are lighter than the ore and can be simply removed by washing with a stream of running water.
( c) Froth flotation process : This process of concentration is done in removing gangue from sulphide ores of certain metals.
(d) Magnetic separation : This method is used in those cases where either the ore or the impurities are of magntic nature.
The concentrated ore is converted into a form which is suitable for reduction to the metal. If the ore is a hydroxide (hydrated oxide), carbonate, or sulphite, it is subjected to calcination or roasting//smeling and thereby converted to the oxide form.
In general most of the metals which occur in the combined state are present in their positive oxidation states. They must, therefore, be reduced by electronation, providing electrons to become free metals. The nature of reducing agent to be used in a particular case depends on how difficult the reduction process is. If the metal is very reactive like the alkali metals they can be reducing only be by electrolytic method.
Less reactive metals like copper, lead, tin etc. can be reduced by chemical reducing agents. The choice of reducing agent is decided by energetic as well as the economic factors.