Before learning how to balance a chemical equation, let’s learn how to write a chemical equation. To write an equation, first, you have to write down the chemical formulas of the reactants and products in the chemical reaction. Since a chemical equation represents a chemical reaction, the accuracy of formulas is important. Let’s understand using an example.

Magnesium + Oxygen  Magnesium oxide

Mg + O₂ MgO

Now let us move on to balancing a chemical equation. To balance an equation, you should keep two things in mind:

• The law of conservation of mass suggests that mass can neither be created nor destroyed. Hence the mass of reactants combined must be equal to the final product of the reaction.
• The number of atoms of reactants must be equal to the number of atoms of the product.

Let’s go back to the equation we referred to in the introduction.

NaOH + H₂SO₄ Na₂SO₄+ H₂O (unbalanced equation)

2NaOH + H₂SO₄ Na₂SO₄+ 2H₂O (balanced equation)

Steps to balance a chemical equation:

1. Count the number of atoms on the left side of the equation as well as on the right side.
2. The left side (LHS) consists of reactants. The right side (RHS) consists of products.
3. Make a table of the number of atoms in LHS and RHS as shown below.
4. Wherever the numbers of atoms are less, we can add a coefficient mentioning the number of atoms.
5. In the above example since RHS has 2 ‘Na’ and LHS has 1 ‘Na’. Add the coefficient 2 to the NaOH reactant. Now when the LHS has 2 ‘Na’ the number of H and O increases in LHS.
6. To balance that, add the coefficient 2 for the H2O in the RHS. Now both LHS and RHS have an equal number of atoms.

 

Elements	LHS	RHS
Sodium (Na)	1	2
Hydrogen (H)	3	2
Oxygen (O)	5	5
Sulphur	1	1

The most important thing to note here is, don’t change the formula of chemical reactants and products. You can only add coefficients, not the chemical formula of the components.

Our environment harbors millions of components and each chemical interaction results in different types of reactions. Broadly, chemical reactions can be divided into five types. Let’s learn what different chemical reactions and equations are:

1. Combination Reaction: A type of reaction when two or more reactants combine together to produce a single product. The product may have different properties from the reactants.

Example: 2H₂(g) + O₂(g) 2H₂O(l)

Hydrogen and oxygen combine to produce water.

2. Decomposition Reaction: A type of reaction when 1 reactant under the presence of external environmental factors breaks into 2 or more products. It is the opposite of a combination reaction. Temperature, sunlight, electricity are some factors favoring this reaction.

Example: 2FeSO₄(s) +Heat  → Fe₂O₃(s) + SO₂(g) + SO₃(g)

Ferrous Sulphate breaks down into Ferric oxide, Sulphur dioxide, and Sulphur trioxide.

3. Displacement Reaction: A type of reaction when the relatively high reactive metal displaces the low reactive metal from its salt. Depending on which metal is more reactive, the metal with high reactivity displaces the metal with low reactivity to form its salt.

Example: Zn(s) + CuSO₄ (aq) →  ZnSO4 (aq) + Cu(s)

Zinc replaces Copper from Copper Sulphate to form Zinc Sulphate and Copper.

4. Double-Displacement Reaction: It is also known as a precipitation reaction. In this type of reaction, exchange of ions takes place between the reactants to product 2 or more different products.

For example: Na₂SO₄ (aq) + BaCl₂ (aq) → BaSO₄(s) + 2NaCl (aq)

Sodium Sulphate reacts with Barium Chloride to give Barium Sulphate and Sodium Chloride.

5. Redox Reaction: A type of reaction in which one reactant is oxidized and the second one is reduced to produce the final product. Oxidation is gaining oxygen whereas reduction is losing oxygen or gaining hydrogen atoms.

For example: CuO +H₂ →Cu+H₂O

Copper Oxide reacts with Hydrogen to produce Copper and water.

During the COVID-19 pandemic, Dabbawalas of Mumbai (world-famous Tiffin Catering Service) complained about how the moist weather tampered with their bicycles. The chemical reason behind their rusted cycles was corrosion. The humidity of Mumbai cost them heavy corrosion. Whenever a metal such as iron or copper is left unattended for days without maintenance, they develop a colored coating. Iron rusts with red color, silver metal turns black, copper metal turns green, etc. This phenomenon is called corrosion. Due to the moisture or acid present in the atmosphere, metals get corroded and damage their strength and other properties.

Whenever oily/ fatty food items are out in the open they develop a stale and sour smell and taste; very unpleasant to savor. The chemistry behind it is oxidation. When the oil-containing food items are left open, they get oxidized and turn rancid. This phenomenon is known as rancidity. Adding preservatives and keeping food in closed containers can prevent rancidity.

1. How do you write a balanced chemical equation?

Answer: Just like mathematics, check if the LHS is equal to RHS. If it is unequal, tally the ions of products and reactants to obtain a uniform number on both sides.

2. What is a balanced chemical equation? Explain with an example.

Answer: 2NaOH + H₂SO₄ Na₂SO₄+ 2H₂O

The above mentioned equation is balanced since the LHS components are equal to RHS components.

3. What are the 5 types of chemical equations?

Answer: 5 types of chemical equations are

•   Combination reaction
•   Decomposition reaction
•   Displacement reaction
•   Double displacement reaction
•   Redox reaction

4. What is a balanced chemical equation and why should it be balanced?

Answer: A balanced chemical equation is a simpler representation of chemical reaction where both LHS and RHS components (ions, charges, and molecules) are equal in number. A reaction should be balanced because if it is not balanced, only partial information is available to interpret, the reader doesn’t know if the reaction is correct or not.

5. What are two reasons for balancing chemical equations?

1. Mass can neither be destroyed nor created hence, total mass of elements of reactants must be equal to the total mass of products.
2. Number of atoms remains the same for the reactants and products of a balanced equation.