Question

The main difference between cast iron and pig iron is that:
(A) Cast iron is purest form of iron while pig iron is impure
(B) Cast iron has lower carbon content (3%) as compared to pig iron (4%) and is extremely hard and brittle
(C) Pig iron contains many impurities like S, P, Si and Mn while cast iron does not contain any impurity and can be cast into any shape
(D) Cast iron is soft and malleable while pig iron is extremely hard and brittle

Answer 1

Hint: In the process of extraction of pure iron, from ores, cast iron is obtained from pig iron. The less pure form of the iron among these two is malleable. The iron obtained from blast furnaces has more carbon content than other types of iron mentioned in the question.

Complete step by step solution:
- Let’s see what pig iron and cast iron are.
- Pig iron is the iron obtained from the blast furnace and it contains about 4% of carbon as impurity. Along with carbon, Si, P and Mn are also present in pig iron as impurity. Pig iron is malleable and can be moulded into a variety of shapes.
- Cast iron is the iron obtained by melting of the mixture of pig iron and scrap iron and coke by hot air blast. It has around 3% of carbon content. So, it is more pure than pig iron. Cast iron is extremely hard and brittle.
- In option (A), it is said that cast iron is the purest form of iron, that is not true. The purest form is wrought iron.
- In option (C), it is mentioned that cast iron can be moulded into any shape, This is not true because cast iron is extremely hard and brittle.
- In option (D), cast iron is said to be malleable and pig iron is said to be brittle , both of these statements are wrong.
- So, only option (B) is right.
Therefore, correct answer of this question is (B) Cast iron has lower carbon content (3%) as compared to pig iron (4%) and is extremely hard and brittle

Note:
Do not consider cast iron as the purest form because wrought iron is the purest form iron. Remember this confusing statement so that no mistake occurs: Cast iron is very hard and brittle so it is not malleable and cannot be moulded into shapes while Pig iron is relatively softer and malleable so it can be moulded into desired shapes.