Skip to content
Related Articles
Get the best out of our app
GFG App
Open App
geeksforgeeks
Browser
Continue

Related Articles

How to Balance Chemical Equations?

Improve Article
Save Article
Like Article
Improve Article
Save Article
Like Article

A chemical equation is a way of explaining a chemical reaction using symbols and equations for the chemicals involved in the process. A balanced chemical equation has an equal number of different elements in the reactants and products, whereas an unbalanced chemical equation has an unequal number of one or more elements in the reactants and products. Unbalanced chemical equations are not possible. The reason for balancing chemical equations, as well as the method of balancing chemical equations, are discussed further below.

What is the need to Balance a Chemical Reaction?

According to the law of conservation of mass, matter can be converted from one form to another, mixtures can be separated or created, and pure substances can be disintegrated, but the total amount of mass remains constant. This crucial law can also be stated in other words that, within quantifiable limitations, the total mass of the universe is constant, anytime matter experiences a change, the total mass of the products of the change is the same as the total mass of the reactants. The mass of products in a reaction must match the mass of reactants, according to the law of conservation of mass, thus equations must be balanced to comply with this law. 

Since the law of conservation of mass states that matter cannot be created or destroyed, a chemical equation must always be balanced. This means that the total mass of reactants must equal the mass of products formed, i.e. the total number of atoms of each element must be equal on both sides of the equation. Hence, to satisfy the law of conservation of mass, the chemical reactions must be balanced.

Balancing of Chemical Equations

Balancing the chemical equation is the process of making the number of different types of atoms on both sides of an equation equal. The hit-or-trial method is used to balance the simple equations. Let’s use one example to demonstrate how to balance equations using the hit-and-trial method.

  • Water is formed when hydrogen reacts with oxygen. This reaction can be expressed as,

H2    +         O2         →       H2O

  • H2 and O2 are reactants in this reaction, whereas H2O is the product. Let’s count how many hydrogen and oxygen atoms there are in the reactants and products.

 

In reactants

In products

No. of H atoms

2

2

No. of O atoms

2

1

  • On both sides, the number of hydrogen atoms is the same. However, the number of oxygen atoms on both sides is not equal. On the left side, there are two oxygen atoms, but only one on the right. Multiply H2O by 2 to get 2 oxygen atoms on the right side, and so the reaction becomes.

H2       +          O2         →          2H2O

  • The total number of atoms on both sides is now,

 

In reactants

In products

No. of H atoms

2

4

No. of O atoms

2

2

  • Despite the fact that the number of oxygen atoms on both sides has equalized, the number of hydrogen atoms has now become uneven. On the left side, there are two hydrogen atoms, whereas, on the right side, there are four hydrogen atoms. Multiply H2 by 2 to get 4 hydrogen atoms on the left side, and the reaction becomes.

2H2       +         O2        →           2H2O

 

In reactants

In products

No. of H atoms

4

4

No. of O atoms

2

2

This chemical equation is balanced because it contains an equal number of hydrogen and oxygen atoms on both sides.

Points to keep in mind for Balancing Chemical Equations

The following considerations should be made while balancing a chemical equation.

  1. The law of conservation of mass governs all chemical equations, stating that matter cannot be generated or destroyed. As a result, each element must have the same number of atoms on both sides of a chemical equation.
  2. To balance the number of atoms of an element on both sides of a chemical equation, use coefficients of products and reactants.
  3. A chemical equation is balanced when there is an equal number of atoms of the same element on both sides.

Consider another example of balancing a chemical equation while considering these points.

Sodium chloride is formed when sodium combines with chlorine.

Na      +         Cl2         →        NaCl

  • The reactants in this reaction are Na and Cl2, whereas the product is NaCl. Let’s count how many nitrogen and chlorine atoms there are in the reactants and products.

 

In reactants

In products

No. of Na atoms

1

1

No. of Cl atoms

2

1

  • The subscript 2 next to chlorine indicates that there are two chlorine atoms on the reactant’s side. However, because the ratio of Na to Cl is one to one, there is only one Cl atom on the product’s side. As a result, a coefficient must be added to the NaCl on the product side to balance the reaction.
  • Never try to balance a reaction by modifying a molecule’s subscripts. The subscripts indicate a specific molecule; altering the subscripts would define a new molecule and not the desired product.
  • Add a 2 in front of the NaCl to balance the reaction.

Na        +        Cl2         →        2NaCl

 

In reactants

In products

No. of Na atoms

1

2

No. of Cl atoms

2

2

  • On each side of the process, there are now two chlorine atoms. On the reactant’s side, there is now one sodium atom and two sodium atoms on the product’s side. As a result, on the reactant’s side, multiply the sodium atom by 2.

2Na        +        Cl2       →          2NaCl

 

In reactants

In products

No. of Na atoms

2

2

No. of Cl atoms

2

2

On each side, two sodium atoms and two chlorine atoms are now present. As a result, the reaction is in balance.

Sample Questions

Question 1: The given reaction between hydrogen and oxygen to form water is balanced here, but is this a correct equation?

H2  +  O   →   H2O

Answer:

Since oxygen is found in the form of O2 molecules rather than atoms, this equation is incorrect. To balance an equation, all of the elements have definite equations that cannot be changed.

Question 2: Is the given equation balanced or not?

H2  +        Cl2          2HCl

Answer:

In the given equation H and Cl are the reactant and HCl is the product. There are 2 hydrogen atoms in the reactant and 2 hydrogen atoms in the product. Similarly, there are 2 chlorine atoms in the reactant and 2 chlorine atoms in the product. This chemical equation contains an equal number of atoms of hydrogen and chlorine on both sides, so this is a balanced equation.

Question 3: Balance the given equation. 

NH3             N2      +         H2

Answer:

There is one nitrogen atom in the reactant and 2 nitrogen atoms in the product. Also, there are three hydrogen atoms in the reactant and two hydrogen atoms in the product. In order to make the number of nitrogen atoms equal on both sides, multiply the reactant NH3 by 2, so the reaction becomes.

2NH3     →        N2      +         H2

Now the number of nitrogen atoms is balanced. But there are 6 hydrogen atoms in the reactant and two hydrogen atoms in the product. In order to make the number of hydrogen atoms equal on both sides, multiply H2 in the product by 3, so the reaction becomes.

2NH3     →        N2      +         3H2

This chemical equation is balanced because it contains an equal number of nitrogen and hydrogen atoms on both sides.

Question 4: Which rule mandates the chemical equations to be balanced?

Answer:

To satisfy the law of conservation of mass, the chemical equations are balanced.

Question 5: What distinguishes a balanced from an unbalanced chemical reaction?

Answer:

The reactants and products in a balanced chemical equation have an equal number of different elements, whereas the reactants and products in an unbalanced chemical equation have an unequal number of one or more elements.


My Personal Notes arrow_drop_up
Last Updated : 21 Nov, 2021
Like Article
Save Article
Similar Reads
Related Tutorials