Balancing chemical equation refers to balancing the stoichiometric coefficients on the reactants and products side. This must be done as the chemical equation obeys the law of conservation of mass and momentum.
Steps to balance chemical equation
Following are the easy steps to balance the equation:
Step 1: Write the Unbalanced Chemical Equation
Let us consider the given reaction. That is the reaction between Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
H2S + 02 → SO2 + H2O
Step 2: Write Down Number of Atoms
Write down the number of atoms of each element present on both reactant as well as product side
Atom | Reactant side | Product side |
H | 1 | 2 |
S | 1 | 1 |
O | 2 | 3 |
Step 3: Add Coefficients To Balance the Mass in a Chemical Equation
Note that the coefficients that are to be added must be a whole number and one coefficient added applies to all the atoms present in that one particular molecule.
For example: 2 H2O implies 4 hydrogen atoms and 2 oxygen atoms.
First try to balance the single element o atom and then move n to hydrogen and oxygen.
So here we will first balance Iron and then oxygen
Go by trial and error method. Adding 2 Hydrogen on both sides then it will be 4 on reactants side and on product side 4.
So 2 H works, 2 hydrogen sulphide, making it 2H20
The same trial and error procedure is now followed to balance oxygen
3 O2 then we have 6 oxygen atoms on the reactant side and also 6 oxygen atoms on the product side.
Hence The balanced chemical equation is:
2H2S + 302 → 2SO2 + 2H2O
Now we can rewrite the table and verify
Atom | Reactant side | Product side |
H | 4 | 4 |
S | 2 | 2 |
O | 6 | 6 |
Now the atoms are balanced in both reactant as well as on the product side.
Hence the balanced chemical equation for Hydrogen sulphide gas burns in air to give water and sulphur dioxide is given as
2H2S + 3O2 → 2SO2 + 2H2O
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