Answer: There are 8 hydrogen atoms on the product side in the reaction.
Step-by-step explanation:
Every balanced chemical equation follows law of conservation of mass.
This law states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form. This law also states that total number of individual atoms on the reactant side must be equal to the total number of individual atoms on the product side.
For the given reaction, the balance chemical equation follows:

On reactant side:
Number of Phosphorus atoms = 1
Number of Chlorine atoms = 5
Number of Hydrogen atoms = 8
Number of Oxygen atoms = 4
On Product side:
Number of Phosphorus atoms = 1
Number of Chlorine atoms = 5
Number of Hydrogen atoms = 8
Number of Oxygen atoms = 4
Hence, there are 8 hydrogen atoms on the product side in the reaction.