We have a synthesis reaction for the formation of ammonia. We have as reactans hydrogen and nitrogen.
These two gases are diatomic gases, that is, in their natural state they are united with themselves. Therefore, the molecular formula of these gases is:
Hydrogen: H2
Nitrogen: N2
Now, the ammonia has the following molecular formula: NH3
The reaction will be:
We have to balance the equation of the reaction.
We stat with nitrogen. We have 2 atoms of nitrogen on the reactants side, so we put coefficient 2 on NH3 molecules.
Then, we have 6 atoms of H on the products side, so we put coefficient 3 on H2 molecule to have the same quantity of H atoms