Examples of Redox Reactions

This section contains a few instances of redox reactions, as well as their oxidation and reduction half-reactions. 

When you recharge a lead storage battery, it becomes an electrolytic cell.

Electrode Processes and Redox Reactions

A redox reaction is a chemical reaction in which electrons are exchanged between two reactants that are involved. Changes in the oxidation states of the reacting species can be used to identify this electron transfer.

Example 1: Reaction Between Hydrogen and Fluorine

In the reaction between hydrogen and fluorine, the hydrogen is oxidised whereas the fluorine is reduced. The reaction can be written as follows.

H2+ F2 → 2HF

The oxidation half-reaction is: H2 → 2H+ + 2e–

The reduction half-reaction is: F2 + 2e– → 2F–

The hydrogen and fluorine ions go on to combine in order to form hydrogen fluoride.

Example 2: Reaction Between Zinc and Copper

This is a type of metal displacement reaction in which copper metal is obtained when zinc displaces the Cu2+ ion in the copper sulphate solution as shown in the reaction below.

Zn (s) + CuSO4 (aq) → ZnSO4 (aq) + Cu (s)

The oxidation half-reaction can be written as: Zn → Zn2+ + 2e–

The reduction half-reaction can be written as: Cu2+ + 2e– → Cu

Thus, copper is displaced from the copper sulphate solution by zinc in a redox reaction.

Example 3: Reaction between Iron and Hydrogen Peroxide

Fe2+ is oxidised to Fe3+ by hydrogen peroxide when an acid is present. This reaction is provided below.

2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O

Oxidation half-reaction: Fe2+ → Fe3+ + e–

Reduction half-reaction: H2O2 + 2e– → 2 OH–

Thus, the hydroxide ion formed from the reduction of hydrogen peroxide combines with the proton donated by the acidic medium to form water.

Oxidation and Reduction Reaction

In order to understand redox reactions, let us first deal with oxidation and reduction reactions individually.

What is Oxidation Reaction?

Oxidation may be defined as loss of electrons from a substance, the other definition of oxidation reactions states that the addition of oxygen or the more electronegative element or removal of hydrogen or the more electropositive element from a substance is called an oxidation reaction.

Following is the example of oxidation reaction:

2S(s) + O2 (g) → SO2 (g) CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l)

What is Reduction Reaction?

Like oxidation reactions, reduction reactions are defined as the gain of electrons. Any substance that gains electrons during a chemical reaction gets reduced.

In other forms, the reduction reaction is stated as the addition of a hydrogen or more electropositive element or removal of a more electronegative element or oxygen from a substance.

Below are some examples of reduction reactions:

2CH2CH2 (g) + H2 (g) → CH3CH3 (g)

2FeCl3 (aq) + H2 (g) → 2FeCl2 (aq) + 2HCl (aq)

Now if we closely examine the above reaction we would find that all the reactions above have both, reduction and oxidation reactions.

The reaction in which FeCl3 is getting reduced as electronegative element chlorine is being removed from it. While hydrogen is getting oxidised due to the addition of chlorine, an electronegative element, in the same reaction.

Oxidising and Reducing Agents

The substance (atom, ion, and molecule) that gains electrons and is thereby reduced to a low valency state is called Oxidising agent.

The substance that loses electrons and is thereby oxidised to a higher valency state is called a reducing agent.

Conclusions

This section we studied a few instances of redox reactions, as well as their oxidation and reduction half-reactions. When you recharge a lead storage battery, it becomes an electrolytic cell. A redox reaction is a chemical reaction in which electrons are exchanged between two reactants that are involved. Changes in the oxidation states of the reacting species can be used to identify this electron transfer.