To balance a chemical equation, both sides should have equal mass, or in other words both sides should have same number of atoms as to follow the conservation of mass rule.
P + O₂ = P₄O₆
LHS:
Number of Phosphorus atoms = 1 atom
Number of Oxygen atoms = 2 atoms
RHS:
Number of Phosphorous atoms = 4 atoms
Number of Oxygen atoms = 6 atoms
Also since P₄O₆ has the most number of atoms we will make the LHS equalize to P₄O₆.
Difference between Phosphorous atoms in LHS to RHS = 3
Since phosphorous is a monatomic we need 3 phosphorous atoms extra
Difference between Oxygen atoms is LHS to RHS = 4
But Oxygen is diatomic, so we need 4/2 = 2 Oxygen molecules
Now lets see if it is balanced
P + 3P + O₂ + 2O₂ -------> P₄O₆
4P + 3O₂ ------> P₄O₆
LHS:
Phosphorous atoms = 4 atoms
Oxygen atoms = 3 × 2 = 6 atoms
RHS:
Phosphorous atoms = 4 atoms
Oxygen atoms = 6 atoms
LHS = RHS
Therefore the balanced equation is 4P + 3O₂ = P₄O₆
Happy to help :)
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