Chapter 9, Problem 123A

Interpretation Introduction

Interpretation:

The reason for the formation of rust when nail is exposed to air needs to be explained. Also, the reason for nail to do not rust in the nitrogen environment needs to be explained.

Concept introduction:

Rusting means oxidation of iron. The iron oxide is formed when rusting of iron takes place and it makes iron flaky and brittle and degrades its strength, appearance and permeability.

Answer to Problem 123A

In air, iron reacts with oxygen to produces iron (II) oxide which is known as rust. Pure iron does not react with nitrogen and in pure nitrogen environment oxygen is absent. So, rust is not formed in pure nitrogen environment.

Explanation of Solution

Air contains oxygen. The iron nail reacts with oxygen and produces iron (II) oxide which is the rust. It is formed between the reaction of oxygen and iron. It is a redox reaction where oxidation of iron and reduction of oxygen takes place. If solid iron is exposed to nitrogen then the nail does not react with nitrogen.

Conclusion

The iron rusting reaction causes a rise in iron's oxidation state, accompanied by a loss of electrons. Rust is nothing but oxide of iron.