Question

4. Iron forms rust when it reacts with
(a) Hydrogen and oxygen
(b) Carbon dioxide and hydrogen
(c) Oxygen and moisture​

Answer 1

Answer:

Rust is a general term for a series of iron oxides, usually, red oxides, formed by the reaction of iron with oxygen in the presence of water or air moisture. It is the common term for corrosion of iron and its alloys, such as steel.

Water is usually present in the form of water vapour and oxygen is always present in the normal atmosphere. The oxygen needs moisture as a catalyst and reactant to accelerate the reaction, so in the absence of moisture, iron won't rust.

So both water and oxygen are required to form rust from metal iron.

Hence, option C is correct.