Question

Ramesh observed colour change in iron articles when kept in moist atmosphere what could be the reason for all these explain any two same type of situations in daily life

Answer 1

Answer:

Ramesh observed the process of corrosion of iron or commonly called rusting.

Explanation :

When iron is kept out in air for a long time, It reacts with oxygen and water(moisture) present in the atmosphere to acquire a coating of a brown flaky substance called rust (This also results in the fading away of its shiny surface and colour). Rust is a reddish brown substance with a chemical formula- $\bold{Fe_2O_3.xH_2O}$

Corrosion of iron can also be defined as the slow oxidation of iron in the presence of oxygen and moisture.

Chemical equations for rusting of iron:-

• $\bold{4Fe_{(s)}+3O_{2(g)}\longrightarrow{}2Fe_2O_{3(s)}}$

• $\bold{Fe_2O_{3}\xrightarrow{\rm{H_2O}}\underset{\text{Rust}}{Fe_2O_3.xH_2O}}$

$\hrulefill$

Some other cases of corrosion:

• Silver articles become black after some time when they are exposed to air. This is because it reacts with sulphur present in the air to form a coating of silver sulphide.

• Copper reacts with moist carbon dioxide present in the air and slowly loses its shiny brown surface and gains a green coat. This green substance is basic copper carbonate.