# What is meant by corrosion? Name any two methods used for the prevention of corrosion.

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(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.

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(a) What is meant by corrosion? Name any two methods used for the prevention of corrosion.

The unwanted reaction of any metal with its surroundings that deteriorate its qualities is called corrosion. Two methods to prevent corrosion is Painting the metal or alloying it with some other metal in an appropriate ratio.

(b) The first step is to separate dust like and other such physical impurities from the ore. The process is called concentration of the ore. Then following steps are carried out:

First of all sulfide ores are subjected to roasting which converts them into metal oxides.

MS + O2 $\overset{Δ}\longrightarrow$ MO + SO2>>> Roasting (heating in excess air)

The metal oxide is then heated with carbon or coke which is a good reducing agent and converts oxide into pure metal.

MO + C $\overset{Δ}\longrightarrow$ CO2 + M>>>> Reduction with coke

The pure metal is then refined to get an ultra-pure metal.

Extraction of moderate reactive metals