Question

The purest form of commercial iron is:
(A) Pig iron
(B) Cast iron
(C) Scrap iron and pig iron
(D) Wrought iron

Answer 1

Hint: Iron as an element is not used for common purposes but the term iron is used for different materials that contain a high percentage of iron in elemental form. These materials are wrought iron, cast iron, pig iron, scrap iron. The purest form of commercially available iron has less than 0.10% carbon content.
Complete step by step answer: There are various materials which are categorized as iron such as:
1. Wrought Iron: It is a form of commercial iron having a very low carbon content (less than 0.10%), the impurities such as sulphur, phosphorus, silicon and manganese are less than 0.25%. It has the largest amount of pure iron in its constituents and is hence known as the purest form of commercial iron.
2. Cast Iron: It is a large family of ferrous alloys. These are multi-component ferrous alloys. The major constituents of cast iron are iron, carbon (2% or more), silicon (1% to 3%), minor elements (less than 0.1%) and often alloying elements (less than 0.1%). The common types of cast iron are (i) white cast iron, (ii) grey cast iron, (iii) ductile cast iron, and (iv) malleable cast iron.
3. Pig Iron: It is an iron-carbon alloy that has other elements such as silicon, manganese, sulphur, phosphorus. It has 3.5% to 4.5%, sulphur less than 0.05 % and phosphorus is up to 0.12%.
Therefore, wrought iron is the purest form of commercial iron. Hence, option (d) is the correct answer.

Note: Properties of wrought iron: it is soft, ductile, magnetic, strong, has high elasticity and tensile strength, and malleable. Due to these properties, wrought iron can be heated and reheated into different shapes. It also becomes stronger as more it is worked upon.