Question

Which of the following is the most impure form of Iron?
A) Bessemer iron
B) Steel
C) Pig iron
D) Wrought iron

Answer 1

The different forms of iron have a different amount of carbon content. Impure form of iron means we have to find the form of iron which has a minimum content of iron and high amount of impurities. The form having high carbon content will be the impure form of the iron.

Complete answer:
Iron is extracted from its ore in the form of different alloys such as pig, wrought, cast and steel. The iron separated at a different level of the iron extraction process has a different composition. All the alloys of iron mainly differ based on carbon content.

The pig iron contains almost $3 - 4\,\%$ carbon and some impurities such as sulphur.
The cast iron contains almost $2 - 3\,\%$ carbon.
The wrought iron contains the lowest, almost $0.08\,\%$ carbon.
Steel contains almost $98 - 99\,\%$ iron and the rest is carbon.
The steel and wrought iron contain the lowest amount of carbon so, they are not impure form.The pig iron contains the high amount of carbon so, it is the impure form of iron. It separated at the initial level of extraction. The pig iron is known as the cheapest form of iron that contains the highest amount of impurities.

Hence, the correct answer is option (C), the most impure form of Iron is “Pig iron”.

Note: Ore of the iron are magnetite, hematite, limonite, and siderite. The ore having a high amount of iron are magnetite and hematite, so these are commercially important. The purest form of the iron is the form that has the highest amount of iron and the lowest amount of carbon. As the number of processes and steps increases in the extraction method, the impurities remove and purity increase. The pig iron is known as the cheapest form of iron that contains the highest amount of impurities. Wrought iron is the purest form of iron.