Question

(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.

Answer 1

Answer:

Corrosion (from the Latin word corrodes, meaning "to gnaw") is the irreversible damage or destruction of living tissue or material due to a chemical or electrochemical reaction. Example: A prime example of corrosion is rusting of iron or steel

Barrier Coatings

One of the easiest and cheapest ways to prevent corrosion is to use barrier coatings like paint, plastic, or powder. ... Plastic and waxes are often sprayed onto metal surfaces. Paint acts as a coating to protect the metal surface from the electrochemical charge that comes from corrosive compounds.

Answer 2

Corrosion

Extraction of metal M

Explanation:

(a) Corrosion is the irreversible damage or destruction of living tissue or material due to a chemical or electrochemical reaction. Example: Rusting of iron.

(b) M is in the middle of the reactivity series and has a sulphide ore. To extract the metal, we do the following:

1. Roasting: Sulphide ore is strongly heated in the presence of air to convert it into metal oxide.
2. Reduction: The metal oxide is converted to free metal by reducing agents like carbon, aluminium, sodium or calcium.
3. Refining: The metal obtained by reduction contains impurities. This impure metal undergoes purification by refining. The most widely used method for refining is electrolytic refining.