i) What is the principle behind the zone refining of metals?

ii) What is the role of Silica in the extraction of Copper?

iii) How is ‘cast ion’ different from ‘pig iron’?

i) Principle of Zone refining - It is based on the fact that the impurities present in the metals are more soluble in the melt than in the solid state of the metal.

•The impure metal bar is heated with the help of circular coils fitted around this bar and slowly moved longitudinally from one end to another of impure metal. As the bar is heated the impurities move/pass to the other side while the metal crystallises.

•As the heating is stopped and the molten is allowed to cool, it crystallizes leaving behind the impurities in the molten metal portion.The process is repeated several times to get pure metal of

•99.99% purity.

ii) The role of Silica in the extraction of Copper is used in the removal of Iron oxide from the copper ore which is formed during the process of roasting.

iii) Pig iron is defined as the iron obtained from the blast furnaces. It contains around 4% of Carbon along with many different impurities. While cast iron is extracted by melting the pig iron and coke using hot air blast. Cast iron contains about 3% Carbon and it is hard.