Question

Which of the following Solutions is used as an anti-rusting Solution?
A.$N{a_2}S{O_4}$
B.$N{a_3}P{O_4}$
C.$N{a_3}B{O_3}$
D.$N{a_2}S$

Answer 1

Rusting is a chemical process in which a metal degrades due to an orange coating over the surface of the metal which forms in the presence of water and oxygen. It is an oxidation reaction as the metal loses electrons. Phosphates are used in anti-rusting Solutions to form a protective layer on the metal surface which protects the metal from rusting.

Complete answer:
Rusting is an oxidation reaction. When iron reacts with water in the presence of oxygen then an orange coating or film is formed on the metal of hydrated oxide, this film or layer is known as rust which is formed on a metal surface when it comes in contact with moisture and oxygen. Rusting is a chemical process in which ferrous forms ferric oxides. This process slowly degrades iron and its alloys and the metal it forms a layer on. Rust has a chemical formula of $F{e_2}{O_3}$. Water and oxygen are the key elements which cause rusting. Water helps iron to react with oxygen by breaking the bonds of the oxygen molecule. During the process of rusting, iron loses electrons and oxygen gains electrons therefore, it is an oxidation reaction. Thus, it is important to prevent rusting.

Rusting can be prevented by the following ways:
- Apply oil on the surface of the metal as oil slows down the process of rusting and prevents moisture from reaching the metal surface and reacting with it.
- Various alloys like stainless steel can be used to prevent and slow down the rusting process.
- A dry coating or paint can also be applied to prevent the surface of the metal from coming in contact with moisture or oxygen. Coating the metal slows down the rusting process.
- The iron or steel can be covered with zinc which corrodes very slowly as compared to other metals. This process of covering iron with a zinc layer is known as galvanization.
- According to the given question we know that phosphates are used in anti-rusting Solutions. When iron metal is dipped or coated with alkaline phosphate Solutions, a protective layer or film of iron phosphate is formed which prevents the metal surface from rusting.

Thus, the correct option is (B) $N{a_3}P{O_4}$.

Note:
Trisodium phosphate $N{a_3}P{O_4}$ is an inorganic compound which is crystalline solid and white in colour. It is used as a cleaning agent and a lubricant. It is moderately acidic in nature and easily soluble in water. It is also used in reactions as an electrolyte replacement.