Question

1. An iron rod is kept in contact with moisture in open air. And few iron fillings are kept in dry
conditions in a container. What do you think are the changes taking place in the two sets
after a period of 10days?

Answer 1

Explanation:

The iron rod which is kept in contact with moisture in open air will get rust on its surface, while the iron filling which are kept under dry condition in a container will remain unchanged.

Conclusion: Rust need moisture and air to form on the surface of the iron rod which is unavailable in case of iron fillings.

Answer 2

$\Large{\underline{\underline{\red{\tt{\purple{\leadsto } SolutioN:-}}}}}$

Here we are given two conditions in which first case iron rod is kept in moisture in open air and in second case the iron fillings are kept in dry conditions in a container.

$\underline{\purple{\bf \leadsto Case\:\:1:-}}$

When iron rod is kept in contact with moisture in open air then , after few days we will observe that the iron rod get coated with reddish brown powder . this is called rust and is actually hydrated ferric oxide $\sf{Fe_2O_3.xH_2O}$ . this process is called corrosion and the chemical process involved in corrosion is called oxidation. The reaction can be represented as :

$\boxed{\bullet\green{\tt \underset{\orange{Iron}}{2Fe}+\underset{\orange{Oxygen}}{\dfrac{3}{2}O_2}+\underset{\orange{Water}}{xH_2O}\xrightarrow{\red{Oxidation}} \underset{\orange{Hydrated\:Ferric\:oxide}}{Fe_2O_3.xH_2O}}}$

$\tt \bullet where\:x\:is\: number\:of\: water\: Molecules.$

The iron rod get all necessary conditions for rusting to take place that is moisture oxygen and iron . if any one of oxygen or water would have been absent then this process would not have taken place .

___________________________________

$\underline{\purple{\bf \leadsto Case\:\:2:-}}$

When the iron fillings are kept in a closed dry container then in this case no rusting process would take place. Since moisture i.e .water is absent. The physical and chemical properties of iron fillings will be same as that of when they were kept .

___________________________________

$\underline{\purple{ \dag \mathscr{M}\sf{or}\mathscr{E}\:\:\:\: \mathscr{I}\sf{nformatio}\mathscr{N}:-}}$

$\pink{\tt Methods\:to\: prevent\: Rusting.}$

$\red{\bf \blue{\bullet}By\: Painting}$

The most popular and common method of preventing rusting is painting. paint forms a layer over the iron articles and does not allow air on moisture to reach iron .

$\red{\bf \blue{\bullet}By\: Greasing\:or\:Oiling}$

Grease or oil also forms a layer over the iron and prevents share and moisture to reach.

$\red{\bf \blue{\bullet}By\: Galvanisation}$

It is the process of depositing a thin layer of zinc metal on the iron objects the more reactive metal react with atmospheric oxygen forming zinc oxide $\sf ZnO$ in the form of layer over the metal. The oxide layer prevents and protects the iron metal from corrosion due to tendency to get oxidized prior to iron.

$\red{\bf \blue{\bullet}By\: Tin\:Plating\:and\: Chromium\:plating}$

Tin and chromium metals are resistant to corrosion . A thin layer of this metals is deposited on the iron objects by electroplating to prevent rusting.

$\red{\bf \blue{\bullet}By\: Alloying}$

Iron is mixed with chromium metal or nikel to obtain stainless steel which is resistive from rusting.