(a) What is meant by corrosion? Name any two methods used for the prevention of corrosion.
(b) Suppose you have to extract metal M from its enriched sulphide ore. If M is in the middle of the reactivity series, write various steps used in extracting this metal.
(a) The eating up of metals by the action of air, moisture or a chemical (such as an acid) on their surface is called Corrosion.
Prevention of corrosion:
- Corrosion or rusting of iron can be prevented by painting, oiling, greasing, galvanising, crome plating, anodising etc.,
- Corrosion of metals can also be prevented by alloying them with suitable metals or non-metals in a required proportion.
(b) M is in the middle of the reactivity series. Various steps which can be used to extract to form its enriched sulphide ore are as follows:
- Roasting: The enriched sulphide ore of ‘M’ is strongly heated in the presence of air to convert it into metal oxide.
- Reduction: The metal oxides obtained by roasting is converted to free metal ‘M’ by reducing agents like carbon, aluminium, sodium or calcium.
- Refining: The metal ‘M’ obtained by reduction contains some impurities. Thus, this impure metal ‘M’ undergoes purification. The process of purifying impure metal is called refining. The most widely used method for refining is electrolytic refining.