Chemistry 2011 JAMB Past Questions - Question 32: The effect of the presence of impurities such as carbon and sulphur on iron is that they

Correct Answer

D

Explanation

The presence of impurities such as carbon and sulfur in iron has various effects, but they do not generally give it high tensile strength. Instead:

1. **Carbon**: The presence of carbon in iron can increase its tensile strength and hardness by forming iron carbide (cementite) in the iron matrix. This process is known as carbonization or carburization. However, excessive carbon content can make iron brittle, reducing its ductility and malleability.

2. **Sulfur**: Sulfur, on the other hand, tends to have a detrimental effect on the mechanical properties of iron. It can form iron sulfides, which are brittle compounds that can weaken the metal. Sulfur impurities can make the iron more brittle and less ductile.

So, to directly answer your question, impurities such as carbon and sulfur do not give iron high tensile strength. Instead, carbon can increase tensile strength (to a certain extent) while sulfur tends to decrease it by making the iron more brittle. Additionally, impurities like sulfur do not make iron more malleable or ductile, nor do they increase its melting point. Instead, they can lower the melting point and affect the mechanical properties negatively.