Oxidation and Reduction

When the oxidation states of atoms change, a chemical process is said to be redox, and it is defined as follows: It is characterized by the actual or formal transfer of electrons between chemical species, with the majority of redox reactions involving one species (the reducing agent) going through oxidation (and thus losing electrons) while another species (the oxidising agent) going through reduction (and thus gaining electrons) (gains electrons). This process is referred to as oxidation for the chemical species from which the electron is withdrawn, and reduction for the chemical species to which the electron has been introduced. To put it another way:

• Oxidation is defined as the loss of electrons or a rise in the oxidation state of an atom, an ion, or of particular atoms in a molecule as a result of the presence of oxygen in the system.

• An atom, an ion, or a specific atom or subatomic particle undergoes reduction when it gains electrons and/or decreases the oxidation state of the atom, the ion, or the specific atom or subatomic particle (a reduction in oxidation state).

Many reactions in organic chemistry are redox reactions, which occur as a result of changes in oxidation states but do not involve any separate electron transfer. These reactions include: For example, when the wood is burned with molecular oxygen, the oxidation state of the carbon atoms in the wood increases while the oxidation state of the oxygen atoms drops, resulting in the formation of carbon dioxide and water. The oxygen atoms go through a reduction process, gaining electrons formally, whereas the carbon atoms go through an oxidation process, losing electrons officially. As a result, oxygen serves as the oxidizing agent in this process, while carbon serves as the reducing agent.

However, although oxidation reactions are generally linked with the creation of oxides from oxygen molecules, oxygen is not always required to be present in such reactions because other chemical species can perform the same role as oxygen.

Oxidation

Traditional or previous concepts of oxidation define the process as one in which oxygen or any electronegative element is added, while the removal of hydrogen or any electropositive element occurs.

In electronic theory, oxidation is defined as the process by which an atom or ion loses one or more electrons as a result of a chemical reaction.

Reduction

Reduction, according to the classical or earlier notion, is a process that involves the addition of hydrogen or any electropositive element, as well as the removal of oxygen or any electronegative element.

Reduction, according to the electronic notion, is described as the process by which one atom or an ion receives one or more electrons from another

The classic concept of oxidation and reduction reactions is as follows:

The following are examples of oxidation reactions:

1. Addition of oxygen:

C + O2 → CO2 (oxidation of carbon)

2. Addition of electronegative element:

Fe + S → FeS (oxidation of Iron)

3. Removal of hydrogen from the system:

H2S + Br2 → 2 HBr + S (oxidation of sulphide)

4. Removal of electropositive elements:

2 KI + H2O2 → I2 + 2 KOH (oxidation of iodide)

An oxidising agent is a chemical that causes oxidation to take place. Among the oxidising agents used in the instances above are oxygen, sulphur dioxide, chlorine dioxide, bromine dioxide, and hydrogen peroxide.

Reduction reactions include the following steps:

1. Addition of hydrogen

N2 + 3 H2 → 2NH3 ( reduction of nitrogen)

2. Addition of electropositive element:

SnCl2 + 2HgCl2 → SnCl4 + Hg2Cl2 ( reduction of mercuric chloride)

3. Removal of oxygen

ZnO + C → Zn + CO (reduction of zinc oxide)

4. Removal of electronegative element

2FeCl3 + H2 → 2FeCl2 + 2HCl (reduction of ferric chloride)

A reducing agent is a chemical that has the effect of reducing the amount of something. In the cases above, the reducing agents H2, HgCl2, and C are used.

Oxidation and Reduction in terms of Electron Transfer

• As a general rule, this is the most generally used and most extensively applicable definition of oxidation and reduction.

• In this situation, oxidation is defined as the loss of electrons, and reduction is defined as the acquisition of electrons.

• The oil rig is a particularly effective mnemonic for remembering this subject.

OIL RIG, Oxidation is the loss of a substance. The gain comes from reduction.

Oxidation and reduction reactions are inextricably intertwined in nature. For the reason that electrons are neither generated nor destroyed in a chemical process, the reactions of oxidation and reduction always occur in pairs; it is, therefore, impossible to have one without the other. Using the following process as an example, magnesium is oxidised by giving up two electrons to oxygen, which is then reduced by absorbing two electrons from magnesium.

Because oxidation and reduction cannot occur in isolation, they are referred to as ‘Redox Reactions’ when they occur as a group. The reactant that oxidises the other reactants is referred to as the oxidising agent, while the reactant that reduces the other reactants is referred to as the reducing agent. There is a great deal of ambiguity about the question of whether oxidising agents receive or give away electrons.

Common Redox Reactions

The following are the three most prevalent redox reactions that occur:

1. Combustion reaction — This is a sort of redox reaction that happens between molecular oxygen and a chemical, resulting in the formation of products that include oxygen.

2C8H18+25O2 → 16CO2(g)+18H2O

2.It is a redox reaction in which just one reactant is reduced and then oxidised, which is known as a disproportionation reaction. An auto-oxidation reaction is another term for this phenomenon.

3ClO−(aq) → ClO3−(aq)+2Cl−(aq)

3. single replacement reactions (also known as single substitution reactions) are a type of redox reaction in which two elements transfer places within a molecule. A single displacement reaction is another name for this type of reaction.

Zn(s)+2HCl(aq) → ZnCl2(aq)+H2(g)

Conclusion  

The terms oxidation and reduction can be defined as the addition or removal of oxygen from a substance, respectively. While this is not the most comprehensive definition, as will be described further down, it is the most easily remembered. Oxidation is the process of gaining oxygen. The loss of oxygen is referred to as reduction. Oxidation-reduction reactions (also known as redox reactions) are essential because they are the primary sources of energy on this planet, whether naturally occurring or biologically produced and artificially produced. The oxidation of molecules, either by the removal of hydrogen or the combination with oxygen, typically results in the release of huge amounts of energy.