Oxidation and Reduction Reactions

What is Oxidation?

Addition of Oxygen to a Substance or removal of Hydrogen from a substance is called Oxidation.

Example

Copper, when heated in presence of Oxygen, turns black (as black copper oxide is formed)

Copper + Oxygen → Copper Oxide

2Cu + O ₂   →    2CuO

      Heat 

In this reaction, Oxygen is added to Copper , therefore oxidation occurs .

What is Reduction?

Removal of Oxygen from a substance or addition of Hydrogen to a substance is called Reduction

Example

If Hydrogen Gas is passed over Copper Oxide, Carbon and Water are obtained

Copper Oxide + Hydrogen → Copper + Water

CuO + H ₂     →   Cu + H ₂ O

 Heat 

Oxygen is removed from Copper and hydrogen is added to it in the reaction, therefore reduction occurs .

What are Redox Reactions?

‘Red' Stands for Reduction

‘Ox' stands for Oxidation

Sometimes Oxidation and Reduction occurs simultaneously .

In a reaction of two substances, one substance may lose Oxygen and other may gain Oxygen

OR

One substance may gain Hydrogen and other may lose Hydrogen.

Such reactions are called Redox Reactions

Examples of Redox Reactions (Oxidation and Reduction Reactions)

Example 1

If Hydrogen Gas is passed over Copper Oxide, Carbon and Water are obtained

Copper Oxide + Hydrogen → Copper + Water

In this case, Copper loses oxygen , it is Reduction Reaction

Hydrogen gains Oxygen , it is Oxidation Reaction

NOTE (for the graphic designer) : Insert NCERT eq 1.30 as an image

Example 2

Zinc Oxide Reacts with Carbon to produce Zinc + Carbon Monoxide

ZnO + C →  Zn + CO

In this case, Zinc loses oxygen , it is Reduction Reaction

Carbon gains Oxygen , it is Oxidation Reaction

NOTE (for the graphic designer) : Insert an image similar to NCERT eq 1.30 for this equation.

Sometimes, losing Hydrogen is also called Oxidation

Gaining Hydrogen is also called Reduction

Example 3

Manganese Oxide reacts with Hydrochloric acid to form Manganese Chloride , water and chlorine

MnO ₂ + 4HCl →  MnCl ₂ + 2H ₂ O + Cl ₂

In this case, HCl turns into H 2 O

It means there is gain of Oxygen

So this is Oxidation.

Also MnO 2 turns into MnCl 2  

There is loss of Oxygen

So this is Reduction.

NOTE (for the graphic designer) : Insert an image similar to NCERT eq 1.30 for this equation.

So, Oxidation and Reduction can defined as,

• Addition of Oxygen to a substance or Loss of Hydrogen to a substance is called Oxidation

• Loss of Oxygen by a substance or Gaining of Hydrogen is called Reduction

QUESTION

Activity 1.1 Burning of Magnesium  in Presence of Air to Produce Magnesium Oxide

Is Magnesium Oxidized or Reduced in this activity?

Answer: 

            The reaction for this is

2Mg(s) + O 2 (g) → 2MgO(s) + energy

In this case

Magnesium gains oxygen , so this is Oxidation reaction.

What are Reducing and Oxidizing Agents?

Substance which gets oxidized is called Reducing Agent. In other words, a substance that reduces another substance is called a Reducing agent.

Substance which gets reduced is called Oxidizing Agent. In other words, a substance that oxidizes another substance is called a Oxidizing agent.

Example

If Hydrogen Gas is passed over Copper Oxide, Carbon and Water are obtained

Copper Oxide + Hydrogen → Copper + Water

In this case, Copper loses oxygen , it is Reduction Reaction

Hydrogen gains Oxygen , it is Oxidation Reaction

Substance which gets Reduced is called Oxidizing Agent

So, Oxidising Agent is Copper Oxide (CuO)

Substance which gets Oxidized is called Reducing Agent

So, Reducing agent is Hydrogen (H ₂ )

Intext Question - Page 13 Q3

NCERT Exercise - Q1, Q16, Q17

Effects of Oxidation Reaction in Everyday Life

There are 2 main effects that we will study in this chapter:

• Corrosion
• Rancidity

Let us learn about them in detail