Table of contents

Advertisement

What is a redox reaction?

A chemical reaction in which both the processes of oxidation and reduction are proceeding is known as an oxidation-reduction reaction or a redox reaction.

The redox reactions proceed in a way that one of the two reactants are oxidized while the other is reduced.

Balancing redox reactions is somehow more difficult as balancing less complicated chemical equations. The reason is that in such equations, not only the number of atoms but also the oxidation states need to be equalized both in reactants and products.

So here, we will discuss the simplest step-by-step method for how to balance a redox equation.

Related: What are Gas Laws and the role of periodic table along with its importance.

Identifying the nature of the reaction

The very first step is to find out whether the given reaction is a redox reaction or not. For this purpose, you have to analyze the changes in oxidation states both at the left and right sides.

A redox reaction is always neutralized by equal charge distribution at both sides. The reaction must have one oxidizing and one reducing unit.

We used a half-reaction method to identify if oxidizing and reducing species are participating in the reaction.

The agenda of using this technique is to determine which components are acting as reducing and oxidizing agent. To understand it, let's get help from an example

2Ag+ + Cu → 2Ag + Cu2+

So first of all, we will split the given reaction into two hypothetical parts such as

Cu → Cu2+
2Ag+ → 2Ag

The oxidation state of Cu in the first reaction at L.H.S is zero due to its free state. So, its oxidation states changed to +2 at the R.H.S. Thus, it can be seen that Cu, in this reaction, is being oxidized.

Now comes to the Ag, which oxidation state at L.H.S is +2. At the R.H.S, the oxidation state of silver changed to zero which means it is being reduced.

We can see the processes of oxidation and reduction happening together. This proves that the given reaction is redox in nature. After we determine the redox nature of a chemical reaction, the next step is to balance the equation.

Related: Learn about the reaction of sodium and chlorine and what happens when they react with each other along with the information of synthesis reactions in chemistry.

Balancing complex redox reactions

We used the half equation method to identify the nature of the chemical reaction. Now we'll use the same method for balancing complex redox equations.

In chemistry, we can balance complex chemical equations easily by following the process. We can calculate the net equation easily by splitting an equation into two redox parts.

The rules for balancing redox reactions are the same for all kinds of reactions (occurring in neutral, acidic, or basic media).

However, some additional rules are applied, besides the general rules, to balance redox equations in acidic and basic media. Let's make the concept clearer by discussing a redox reaction example occurring in the basic medium.

Related: What is the general chemical equation for an endothermic reaction.

Balancing redox equations in basic solutions

Zn2+ + Ag → Zn + Ag2O

Step #1: Split the Reaction

Split the reaction into two halves such as

Zn2+ → Zn
Ag → Ag2O

Also find the complete process of metal displacement reactions in aqueous medium.

Step #2: Balance Atoms of Elements

Balance the number of atoms for each element in both equations other than hydrogen and oxygen such as

2Ag → Ag2O
Zn2+ → Zn

Ralated: How to determine chemical factors or conversion factors.

Step #3: Balance Atoms of Oxygen

Balance oxygen atoms by adding water molecules on the left-hand side such as

2Ag + H2O → Ag2O
Zn2+ → Zn

Related: What is heat of combustion in organic chemistry?

Step #4: Balance number of Protons

Balance the number of protons by adding H+ ions at the right-hand side such as

2Ag + H2O → Ag2O + 2H+
Zn2+ → Zn

Related: How to find the percent yield of a chemical reaction step by step?

Step #5: Balance Charges

Balance charges at both sides by adding electrons

2Ag + H2O → Ag2O + 2H+
Zn2+ → Zn + 2e-

Step #6: Check Net Charges

Combine both halves to check net charges and cancel them out at both side as follows

2Ag + H2O + Zn2+ → Ag2O + 2H+ + Zn

Step #7: Neutralize the Equation

Since 2H+ are present at the R.H.S, add 2OH- at both side to balance and neutralize the equation

2OH- + 2Ag + H2O + Zn2+ → Ag2O + 2H+ + Zn + 2OH-

Step #8: Combine Elements

Combine proton and hydroxyl units at both sides to form water molecule such as

2OH- + 2Ag + H2O + Zn2+ → Ag2O + Zn + 2H2O

Step #9: Cancel the common terms

On cancelling the common terms on both sides, the final equation would be such as

2Ag + 2OH- + Zn2+ → Ag2O + Zn + H2O

While dealing with redox reactions in acidic solutions, the entire method is just the same except for steps 7 and 8. To balance such acidic redox equations, OH- groups are not added to balance charges on both sides.

Meanwhile, the step of adding hydrogen and hydroxyl groups to form water is also not included in the method.

Besides this method, you can also get quick help from a balancing redox reactions calculator. All you have to do is to insert the equation in the bar and wait for a few seconds for the final equation.

Similarly, there are many online chemical equation product calculators which can be used for balancing chemical equations. The best thing about using such advanced tech tools is that you dont even need to determine the type of reaction or the reaction medium.

Advertisement