The given chemical equation is for reaction between phosphorus (P) and oxygen (O2). The product is phosphorus pentoxide (P2O5).
The reaction is : P + O2 -> P2O5
A well-balanced chemical equation contains equal number of each species on both reactant and product side. In the given equation, there is only 1 atom of phosphorus on the reactant side, while there 2 atoms on the product side. Similarly, the number of oxygen atoms are 2 and 5 on reactant and product side, respectively. Hence this equation is not balanced.
Let us first balance phosphorus by using a coefficient of 2 on the reactant side. That is,
2P + O2 -> P2O5
Now let us balance oxygen atoms with a coefficient of 2.5 (or 5/2) on the reactant side. That is,
2P + 5/2 O2 -> P2O5
We can also multiply the entire equation with 2 to get another form of the equation:
4P + 5O2 -> 2P2O5
Thus, the well-balanced form of chemical equation is:
`2P + 5/2 O_2 -> P_2O5`
`4P + 5O_2 -> 2P_2O_5`
Hope this helps.