Question

Translate the following statement into chemical equation and then balance the equation:

Hydrogen sulphide gas burns in air to give water and sulphur dioxide

Answer 1

Balanced chemical equation:

A chemical equation in which the number of atoms of each element on both sides of the equation is equal is called a balanced chemical equation.

Step 1: Representation of the chemical reaction:

• Hydrogen sulfide gas burns in the air to give water and sulfur dioxide.
• The reaction can be written as:

$\underset{\mathrm{Hydrogen}\mathrm{sulphide}}{{\mathrm{H}}_2\mathrm{S}}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2}\to \underset{\mathrm{Sulphur}\mathrm{dioxide}}{{\mathrm{SO}}_2}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}}$

Step 2: Calculating the number of atoms on both sides of the reaction:

Elements	Number of atoms on the reactant side	Number of atoms on the product side
H	2	2
S	1	1
O	2	3

Step 3: Balancing the uneven number of atoms on the reactants and products side:

1. As the number of atoms on the reactants and products side is different, so balancing of hydrogen, oxygen, and sulfur atoms can be done by multiplying the required coefficient for them in the reaction.
2. This is done by multiplying 2 to hydrogen sulfide and 3 to oxygen on the reactant side and also 2 to sulfur dioxide and 2 to water on the product side, to make the two sides equal.

$\underset{\mathrm{Hydrogen}\mathrm{sulphide}}{2{\mathrm{H}}_2\mathrm{S}}+\underset{\mathrm{Oxygen}}{3{\mathrm{O}}_2}\to \underset{\mathrm{Sulphur}\mathrm{dioxide}}{2{\mathrm{SO}}_2}+\underset{\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}}$

Elements	Number of atoms on the reactant side	Number of atoms on the product side
H	4	4
S	2	2
O	6	6

Now, we can see that the balanced equation is:

$\underset{\mathrm{Hydrogen}\mathrm{sulfide}}{2{\mathrm{H}}_2\mathrm{S}}+\underset{\mathrm{Oxygen}}{3{\mathrm{O}}_2}\to \underset{\mathrm{Sulfur}\mathrm{dioxide}}{2{\mathrm{SO}}_2}+\underset{\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}}$