Chemical Reactions and Equations - Class 10th Science

Redox Reaction

Chemical Reaction in which oxidation and reduction takes place simultaneously is called oxidation – reduction reaction. Such reaction also called Redox Reaction.

The word Redox is the combination of two words, i.e. Red + Ox

The word, ‘Red’ comes from ‘Reduction’ and the word, ‘ox’ comes from ‘Oxidation’.

In every chemical reaction oxidation and reduction takes place simultaneously. Thus, every chemical reaction is a redox reaction.

Example: 1:

CuO → Reduced to Cu (Because of loss of oxygen)

H2 → Oxidised to H2O (Because of gain of oxygen)

In this reaction, copper loses oxygen and reduced to copper. On the other hand hydrogen gains oxygen, and oxidized to water. Thus, both oxidation and reduction take here simultaneously, thus this is a Redox Reaction or Oxidation-Reduction Reaction.

Example:2:

When Zinc oxide reacts with carbon, it gives zinc and carbon monoxide.

Here,

ZnO → Reduced to Zn (Because it loses oxygen)

C → Oxidised to CO (Because it gains oxygen)

Here, Zinc oxide is reduced to zinc; as it loses oxygen and Carbon is oxidized to carbon monoxide; as it gains oxygen. Thus, here oxidation and reduction both take place simultaneously. Hence, this is an Oxidation-Reduction Reaction or Redox Reaction.

Example:3:

When Manganese oxide reacts with hydrochloric acid, it gives manganese chloride, water and chlorine gas.

Here,

MnO2 → Reduced to MnCl2 (As it loses oxygen)

HCl → Oxidises to Cl2 (As it loses hydrogen)

Here, in this reaction, manganese oxide reduced to manganese chloride because it loses oxygen. Hydrochloric acid, oxidized to chlorine as it loses hydrogen.

Hence, this is a redox reaction or oxidation reduction reaction.

Loss of oxygenGains of hydrogen

Oxidation Reduction Reaction in Everyday Life

Corrosion

Gradual destruction of metals because of formation of respective oxide, hydroxide, or sulphide, etc. because of chemical reaction with substances present in environment is called corrosion.

Metals react with oxygen, sulphide, moisture, etc. present in environment. A layer of different color of metals oxides, sulphides or hydroxide deposited over them. Because of formation of these layers; metals first lose their lusture and gradually get destroyed. Rusting of iron, tarnishing of copper and silver, etc. are some common examples of corrosion.

Rusting of Iron:

Articles made of iron when exposed to moisture present in air; a layer of iron oxide is formed over them. This layer starts eating or corroding iron gradually. Iron oxide is brown in colour. The formation of iron oxide over the iron articles because of reaction with moisture present in air is called rusting of iron.

Prevention of Rusting:

Rusting can be prevented by keeping articles made of iron separated from moisture. Some methods to keep the articles made of iron separated from moisture present in environment.

By covering a coat of paint over articles made of iron. Coat of paint keep iron articles safe from getting contact with moisture.

Applying a layer of grease over iron aricles, such as cycle chain, ball bearing etc.

Tarnishing of articles made of silver:

Articles made of silver, such as jewellery, got a black coating over them because of sulphide present in environment.

Articles made of copper get dull and finally become greenish because of first formation of oxide and finally formation of carbonate over them.

Corrosion of metals lead to loss of millions of rupees every year as it damage bridges, car’s body, grills, etc. Rust gradually corrodes the articles made of iron and finally damages them completely.

Rancidity

The spoilage of food items especially made of using oils because of hydrolysis and oxidation of fats present in food is called rancidity.

When a food items exposed to air, because of oxidation of fats present in food items food gets rancid. When a food gets rancid, it gives bad taste and starts giving bad smells. Rancidity also degrades the nutrients value of food. Eating of rancid food may leads to health problem.

Prevention of Rancidity

Antioxidant is added to packet of food items to prevent food items to get exposed to oxygen present in air. For example, potato chips are packed with nitrogen in bags to prevent chips from getting oxidized.

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