Master Chemical Equation Balancing with These 3 Simple Rules


A chemical reaction presents the scenario of how atoms are wrestling with each other during a chemical reaction. And no matter how much they come to blows, the reactants and products on both sides of a balanced chemical equation will always have equal numbers of atoms. But why do atoms do this? Why don’t one of either side wins the battle? Because a balanced chemical equation always has to satisfy the Law of Conservation of Mass.

According to the Law of Conservation of Mass, one can neither create nor destroy atoms but transform them from one form to another. According to this, even though chemical compounds break while battling and form new compounds during a chemical reaction, atoms in the reactants do not disappear, nor do atoms appear as products. A chemical reaction neither creates atoms nor destroys them. The equal number of atoms present in the reactants are also present in the products- the atoms merely reorganise themselves in different arrangements. In a complete chemical equation, both sides must be present on the reactants and products sides of the equation.

And in this article, we will talk about what a chemical reaction is, the rules for balancing chemical equations, steps for balancing chemical equations and make your understanding easier by providing you with some examples. Stay with us!

What is a chemical equation?

Let us define a chemical equation by moving a step behind- by defining a chemical reaction. A chemical reaction is a process that occurs when two or mole atoms collide with sufficient force and the correct orientation to form a new product. And a chemical equation is a symbolic representation of chemical reactions in which we express the reactants and the products in their respective chemical formulae.

Here is what a chemical reaction looks like:

Fe + o2 ® Fe2o3

The left-hand side of the equation has reactants. These are the materials that you start your reaction with and start the reaction process by reacting them.

The right-hand side of the equation has products. These are the substances formed due to a chemical reaction between the raw materials.

For a chemical reaction to be correct, it requires satisfying the Law of Conservation of mass. As we have already discussed the law, according to it, iron (Fe) and oxygen (O2) will have the same number of atoms before and after the reaction occurs. It is just that the arrangement of iron and oxygen atoms will change. And this will happen because the mass of the entire material taking part in the reaction can’t be changed.

Note: If your chemical reaction has different masses on the right and left sides, you must balance your chemical equation.

Rules for Balancing Chemical Equations

You cannot just add or subtract numbers from either side of an equation to balance it. Instead, you must follow a 3-rule step for balancing your equation which we will discuss here:

Balancing chemical equations means that you correctly write the chemical equation to equate the amount of mass on each side of the arrow.

This section will learn how to balance a chemical equation by using a real-life example.

This is a chemical reaction that occurs when iron rusts:

Fe + o2 ® Fe203

# Rule 1: Recognise the reactants and products

The first step in balancing a reaction recognises your products and reactants.

Remember that your products are on the right side, and the reactants are on the left side of an equation.

For the equation written above, our reactants are Fe and O2. Our products are Fe2 (iron) and O3 (oxide).

# Rue 2: Write the number of atoms 

Next, you must determine the number of atoms of each element on either side of the equation.

You can do this by looking at the coefficients or subscripts. If there is no coefficient present, you just have one atom of something (element).

Fe + o2 ® Fe203

On the product side, you have two iron atoms and three oxygen atoms.

On the reactant side, you have one atom of iron and two oxygen atoms.

So, while writing the number of products, you can see that the equation is not balanced. This is because there are different number of atoms on the products’ and the reactants’ sides. That means we need to add coefficients to balance this equation.

# Rule 3: Add subscripts or coefficients

Earlier, we mentioned that you could tell about the number of atoms of a particular element in two ways: by looking at the coefficients and the subscripts.

While balancing a chemical equation, you never change subscripts. You only change coefficients.

Coefficients and Subscripts

Chemical equations stage two types of numbers, always. One type represents the coefficients placed in front of the formulas. This shows how many molecules of that substance are produced or used. The other type represents subscripts which are part of the chemical formulas of the reactants and products.

The subscripts are part of the formulas, and once the formula for the reactants and products are determined, we may not change the subscripts.

The coefficients show the number of each substance involved in the reaction and may be modified to balance the equation.

Balancing Chemical Equation

So, in our chemical equation (Fe + o2 ® Fe203), any coefficient you add to the product must reflect the reactants.

Let us look at how to balance this chemical equation.

On the product side, you have two iron atoms and three oxygen atoms. So let us tackle the iron (Fe) first.

When looking at this equation first, you might think that something like this works:

2Fe + o2 ® Fe2O3

While that balances out the iron atoms (leaving two on each side), oxygen remains unbalanced. So that remains, we are not over yet balancing the equation.

Taking iron atoms at first, we know we will work with a multiple of two since there are two iron atoms present on the product side.

Knowing that using two as a coefficient will not work, let us try the next multiple of two, which is four.

4Fe + O2 ® 2Fe2O3

That creates balance for iron. Oxygen is still not balanced, but the product side has six oxygen atoms. Six is a multiple of two, and therefore, we can work with that on the reactant side, where two oxygen atoms are present.

That means we can write the balanced equation this way:

4Fe + 3O2 ® 3Fe2O3

Steps for Balancing Chemical Equations

Let us now put all these wordy steps in 5 simple steps:

  1. Recognise the most complicated substance.
  2. Starting with that substance, select an element or elements that appear in only one reactant and one product. Adjust the coefficients to equate the number of atoms of the element or these elements on both sides.
  3. Balance polyatomic ions (if present on both sides of the chemical equation) as a unit.
  4. Balance the remaining atoms, usually ending with the least complicated substance and using fractional coefficients. If a fraction coefficient has been used, multiply both sides by the denominator to equate the equation.
  5. Count the number of atoms of each kind of element on both sides to ensure that the chemical equation is balanced.

Now let us look at another example to understand the balancing part better.

Example: Combustion of Heptane

Balance the chemical equation for the combustion of Heptane (C7H16)

C7H16 (liquid) + O2 (gas) ® CO2 (gas) + H2O (gas)


Step 1: Identify the most complex substance

The most complex substance in the above reaction is with the most significant number of different atoms, which is C7H16. Therefore, we will first assume that the final balanced equation contains one molecule of this substance.

  1. Because  one molecule of n-heptane contains seven carbon atoms, we require 7CO2 molecules, each of which contains one carbon atom, on the right side:

C7H16 + O2 ® 7CO2 +H2

Seven carbon atoms on both reactant and product sides

Step 2: Adjust the coefficients

  1. Because a molecule of n-heptane contains 16 hydrogen atoms, we require 8H20 molecules, each of which has two hydrogen atoms, on the right side:

C7H16 + O2 ® 7CO2 + 8H2O

16 hydrogen atoms on both reactant and product sides

Step 3: Balance polyatomic ions as a unit

As you can see, there are no polyatomic ions to be considered in this reaction.

The hydrogen and carbon atoms are now balanced. But we have 22 oxygen atoms on the right side and only two oxygen atoms on the left-hand side. So we can balance the number of oxygen atoms by adjusting the coefficient in front of the least complex substance, O2, on the reactant side:

Step 4: Balancing the remaining atoms

C7H16 +11O2 ® 7CO2 + 8H20

Twenty-two oxygen atoms are now present on both reactant and product sides.

Step 5: Check your work

Now you have a balanced equation, and there are factual coefficients. There are seven carbon atoms, 16 hydrogen atoms, and 22 oxygen atoms on either side of the equation. Always check to ensure that a chemical equation is balanced before you move to the next question.

In conclusion,

Balancing chemical equations seem complicated, but it is not that hard!

Your primary goal when balancing equations is to ensure that there are the same amount of reactants and products on either side of the equation arrow. You should keep counting the number of atoms with every step of balancing the equation. And you should also keep following the steps to balance your equation in every way possible.

Author’s Bio: Matt Southern holds a PhD in chemistry who has given his insights into the chemical equation balancer and factoring calculator hosted by In his free time, he will also offer essay editing services. So, all you need to do is tell him, “dissertation help Singapore or essay help” and he will help you out.


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