JEE Main 2020 · 7 January · morning · Single correct · +4 / −1
The purest from of commercial iron is :
- (a) pig iron
- (b) wrought iron
- (c) cast iron
- (d) scrap iron and pig iron
Answer and solution
Answer (b) wrought iron
Solution
Chemistry ma’am · 3 steps
Rank the forms of iron by carbon content: the one with the least carbon is the purest.
- What makes iron impure. Commercial iron differs mainly in how much carbon it carries, along with small amounts of S, P, Si and Mn. Less carbon means purer iron.
Form Carbon content How it is made Pig iron about 4% straight from the blast furnace Cast iron about 3% pig iron remelted with scrap iron and coke Wrought iron about 0.1 to 0.25% cast iron refined in a haematite-lined furnace - Refining step. In a reverberatory furnace lined with haematite, the oxide burns off the carbon: Fe₂O₃ + 3C → 2Fe + 3CO. Most of the S, Si and P are also removed, which leaves nearly pure iron.
- So. Wrought iron, also called malleable iron, has the lowest carbon content and is the purest commercial form. The answer is (b).
The idea to keep. For forms of iron, think carbon content: pig iron about 4%, cast iron about 3%, wrought iron about 0.2%. The lower the carbon, the purer and more malleable the iron.
Answer from the NTA final answer key. Solution by PrepWiser.