# Chemical Equation

#### Learning Goals

• Balance chemical equation
• Examples of balanced equation

According to Law of Conservation of Mass, mass can neither be created nor destroyed in a chemical reaction. To obey this law, the total mass of elements present in reactants must be equal to the total mass of elements present in products.

## Balancing a chemical equation:

To balance the given or any chemical equation, follow these steps:

Fe + H2O ⇨ Fe3O4 + H2

Write the number of atoms of elements present in reactants and in products in a table; as shown here.

Name of atom No. of atoms in reactant No. of atoms in product
Iron 1 3
Hydrogen 2 2
Oxygen 1 4

Balance the atom which is the maximum in number; on either side of chemical equation.

In this equation, the number of oxygen atom is the maximum on the RHS.

To balance the oxygen one needs to multiply the oxygen on the LHS by 4; so that the number of oxygen atoms becomes equal on both sides.

Fe + 4 × H2O ⇨ Fe3O4 + H2

Now, the number of hydrogen atoms becomes 8 on the LHS; which is more than that on the RHS. To balance it, one needs to multiply the hydrogen on the RHS by 4.

Fe + 4 × H2O ⇨ Fe3O4 + 4 × H2

After that number of oxygen and hydrogen atoms becomes equal on both sides. The number of iron is one on the LHS, while it is three on the RHS. To balance it, multiply the iron on the LHS by 3.

3 × Fe + 4 × H2O ⇨ Fe3O4 + 4 × H2

Now the number of atoms of each element becomes equal on both sides. Thus, this equation becomes a balanced equation.

Name of atom No. of atoms in reactant No. of atoms in product
Iron 3 3
Hydrogen 8 8
Oxygen 4 4

After balancing, the above equation can be written as follows.

3Fe + 4H2O ⇨ Fe3O4 + 4H2

#### Balance the given equations.

1. H2 + O2 ⇨ H2O
Answer: 2H2 + O2 ⇨ 2H2O
2. Fe + H2O ⇨ Fe2O3 + H2
Answer: 2Fe + 3H2O ⇨ Fe2O3 + 3H2
3. CO2 + H2O ⇨ C6H12O6 + O2
Answer: 6CO2 + 6H2O ⇨ C6H12O6 + 6O2
4. Fe2O3 + C ⇨ Fe + CO2
Answer: 2Fe2O3 + 3C ⇨ 4Fe + 3CO2

#### Writing the symbols of Physical States of substances in Chemical equation:

By writing the physical states of substances a chemical equation becomes more informative.

• Gaseous state is represented by symbol ‘g’
• Liquid state is represented by symbol ‘l’
• Solid state is written by symbol ‘s’
• Aqueous solution is written by symbol ‘aq’

Writing the condition in which reaction takes place: The condition is generally written above and/or below the arrow of a chemical equation.

Thus, by writing the symbols of physical state of substances and condition under which reaction takes place, a chemical equation can be made more informative.