Oxidation-Reduction Reactions

Every redox reaction is determined by a change in the oxidation state of two atoms. If the oxidation number does not change, there is no redox reaction. Oxidation reduction processes may be traced all the way back to the dawn of human history, from the first time people came into contact with fire and began to use it in their daily life, especially during the Copper Bronze era of human evolution, some 6000 years ago. The relevance of oxidation-reduction (redox) processes is that they are the principal natural and artificial sources of energy on our planet. When molecules are oxidized by eliminating hydrogen or combining with oxygen, a lot of energy is released.

Brief Inscriptions on Oxidation-Reduction Reactions-

Now we will take a look at what do we mean by redox reactions, balancing redox reactions oxidation number method, balancing redox reactions examples and lastly at balancing redox reactions oxidation number method worksheet.

Redox reaction-

An oxidation-reduction or redox reaction is a kind of chemical reaction in which two species exchange electrons. An oxidation-reduction reaction is a chemical reaction in which the oxidation number of a molecule, atom, or ion changes by acquiring or losing an electron.

Redox reactions are required for photosynthesis, respiration, combustion, and corrosion or rusting, to name a few fundamental life processes.

There are two halves to redox reactions: a reduced half and an oxidized half that always occur at the same moment. As the reduced half acquires electrons, the oxidation number decreases, whereas the oxidized half loses electrons as the oxidation number increases. To remember this, use the mnemonic devices OIL RIG, which stand for “oxidation is loss” and “reduction is gain.” The number of electrons in a redox reaction does not change. Those released in the oxidation half reaction are taken up by another species in the reduction half reaction.

In a redox reaction, the two species that exchange electrons are given unique names-

1.The oxidizing agent is an ion or molecule that receives electrons and oxidizes another species by accepting electrons.

2.The reducing agent is an ion or molecule that transfers electrons- by doing so, it decreases the other species.

Balancing redox reactions oxidation number method-

First, we will learn what we mean by balancing reaction equations or balanced equations.

A chemical equation is a representation of a chemical reaction’s net composition change. It demonstrates how a given number of reactants produces a given amount of products. Both of these quantities are expressed in moles.

Chemical equations often include information regarding the state of the reactants, such as whether they are solid, liquid, gaseous, or aqueous. They also follow the rule of conservation of mass, which states that matter may alter its shape but cannot be generated or destroyed.

This indicates that regardless of the operations taking place within a closed system of substances, the mass of the system will stay constant. In other words, the mass of the reactants must match the mass of the products in any chemical equation in a closed system. As a result, each element must have the same number of atoms on both sides of a chemical equation. This is shown by a correctly balanced chemical equation.

Now we will see what do we mean by oxidation number- An atom’s oxidation number, commonly known as its oxidation state, is used to calculate how many electrons it contains. However, oxidation values may not always correspond to actual molecular charges. As a result, regardless of covalent or ionic interaction, we can calculate oxidation values for atoms of any element.

Coming onto oxidation number method-

The oxidation number approach, also known as oxidation states, maintains track of the electrons acquired and lost as a material is reduced and oxidized. An oxidation number is ascribed to each atom in a neutral molecule or charged species. Oxidation is the process of a rise in the oxidation number. Reduction happens when the oxidation number falls below a certain threshold. The sum of a chemical’s oxidation numbers determines its total charge.

Balancing redox reactions examples-

When balancing redox equations, the oxidation number approach is used to keep track of electrons. Electrons are transported between charged atoms in a generic sense.

An example showing how to balance an equation using this method-

Zn+HCl→ZnCl2+H2

1.Determine which atoms have an oxidation number that changes.

Left side- Zn = 0, H = +1,  Cl = -1
Right side- Zn = +2, Cl = -1, H = +1

The changes in oxidation state are as follow-
Zn- 0 → +2, changed state = +2
H- +1 → 0, changed state = -1

2. Equalize the changes in states- Each Zn atom has two electrons lost, whereas each H atom has one electron gained. For every atom of Zn, you’ll need two atoms of H. We have total changes of +2 and -2 as a result of this.

3. Insert numbers to get result-

Zn+2HCl→1ZnCl2+H2

Final balanced equation is- Zn+2HCl→ZnCl2 +H2

Balancing redox reactions oxidation number method worksheet-

Now we will look at the rules for balancing the reactions by this method-

When an atom joins with other atoms in a compound, its oxidation state (OS) corresponds to the number of electrons, e-, that it loses, acquires, or seems to utilize. There are seven rules to follow when determining an atom’s oxidation state-

1.A single atom’s oxidation state is zero.

2.In a neutral species, the total oxidation state of all atoms is 0, and in an ion, the total oxidation state of all atoms is equal to the ion charge.

3. Group 1 metals have an oxidation state of +1, whereas Group 2 metals have an oxidation state of +2.

4.In compounds, fluorine has an oxidation state of -1.

5.In most compounds, hydrogen has an oxidation state of +1.

6.In most compounds, oxygen has an oxidation state of -2.

7.In binary metal complexes, the oxidation state of Group 17 elements is -1, Group 16 elements is -2, and Group 15 elements is -3.

Example-

HNO₃ + H₃AsO₃(aq) → NO(g) + H₃AsO₄(aq) + H₂O(l)

1.Check each atom’s oxidation state-

Left- H = +1, N = +5, O = -2, As = +3 

Right- N = +2, O = -2, H = +1, As = +5 

2. Measure the difference in oxidation state for each atom that changes- As- +3 +5, Change = +2 N, +5 +2, Change = -3 As- +3 +5, Change = +2 3.

3.Raise the overall oxidation number in proportion to the reduction in total oxidation number. We need two atoms of N for every three as atoms. As a consequence, we have total changes of -6 and +6.

4.Place these values in front of formulas with those atoms as coefficients.

2HNO₃ + 3H₃AsO₃(aq) → 2NO(g) + 3H₃AsO₄(aq) + H₂O(l)

5.Balance the remaining, except H and O.

6.We are good to go now.

Conclusion-

In this article we read about redox reactions, balancing redox reactions, oxidation number method, balancing redox reactions examples. When molecules are oxidized by eliminating hydrogen or combining with oxygen, a lot of energy is released. The species that receives electrons is reduced, and it is typically the oxidizing agent, while the species that loses electrons is usually the reducing agent. Common redox processes include photosynthesis, respiration, combustion, and corrosion. The importance of redox reactions in biological processes cannot be overstated. The electron transport system in cells, for example, and glucose oxidation are examples of redox processes in the human body. Redox reactions are used to generate a variety of chemical compounds that are valuable in industrial activities.