Name: Metal Displacement Reactions
Uploaded: 2019-07-19
Duration: 9 min 12 s
Description: This video describes the displacement reactions based on the reactivity series in which a more reactive element displaces a less reactive one from its aqueou...

Question

What is rust? Write chemical equation of rusting.

Accepted Answer

Rust is hydrated iron oxide. When active metals like aluminium, zinc - react rapidly with oxygen and moisture, they are converted into their respective compounds in a process known as corrosion. The corrosion of iron by oxygen and water is called rusting.

The chemical equation of rusting is as follows:

When metals like iron are placed in air and humid conditions, the negatively and positively charged regions develop on their surface. As a result, it starts behaving like an electrochemical cell.

Anode - $Fe$ moves into the solution as ${Fe}^{2 +}$ .

$Fe \to {Fe}^{2 +} + 2 e^{-}$

Cathode - In the presence of oxygen, these electrons are taken up by water molecules to form ${OH}^{-}$ ions.

$2 H_{2} O + O_{2} + 4 e^{-} \to 4 {OH}^{-}$

The ${Fe}^{2 +}$ ions formed on the anode react with the ${OH}^{-}$ to form $Fe {(OH)}_{2} (s)$ . This iron hydroxide reacts with the oxygen in the atmosphere in the presence of moisture to give hydrated iron oxide.

$2 Fe {(OH)}_{2} + ½ O_{2} (g) + H_{2} O (l) \to {Fe}_{2} O_{3} . {xH}_{2} O (s)$

This hydrated iron oxide is known as rust.

What is rust? Write chemical equation of rusting.

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