Question
Answers

The most impure form of iron is:
A.Wrought iron
B.Mild steel
C.Hard steel
D.Pig iron

Answer
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Hint:
Industrial steel is a widely used material and comes in a variety of constituent configurations. Steels of any type usually have a very high percentage of iron.

Complete step by step answer:
-Any form of steel contains anywhere between 0.05 to 0.3% of carbon. While the majority constituent of steel, i.e. Iron, most contributes more or less 99% to the percentage composition of steel.
-Now for understanding the difference between the different types of steel, we must know that different types of steel are used for different applications all over the industry. There are instances where a softer and more ductile steel is required in comparison to hard and stiff steel. This hardness in the different types of steels is determined by carbon composition.
So both mild steel and hard steel have more or less 99% of Iron with the variation being in the form of carbon and other minor constituents.
-When we consider wrought iron, we must understand that Wrought iron is produced in a process wherein an iron sample is removed from the furnace and worked on directly. This helps in removing molten slag. Hence the percentage of Iron present in Wrought Iron is also very high in the range upwards of 98%.
-Now, while considering the case of Pig Iron, we must know that Pig iron is produced by smelting Iron ore with a high carbon fuel. Chemically speaking, Pig iron is obtained by reducing Iron ore with coke or anthracite in a blast furnace. This significantly increases the percentage composition of Carbon. This indirectly means that the percentage of iron is reduced. Experimentally it is found that iron contributes only about 91-94% to the total composition of Pig iron.

Hence, Option D is the correct option.

Note:
Wrought iron is no longer produced due to the advancement in steel making processes. Although it was considered as the steel of the early ages, it has been replaced by better materials.