Final answer:
The mass of ammonium phosphate created is dependent on the amount of phosphoric acid used, and exact quantities require stoichiometric calculations based on a balanced chemical equation.
Step-by-step explanation:
The mass of ammonium phosphate produced by the reaction of phosphoric acid will depend on the amount of phosphoric acid used. Hence, the correct answer to the student's question is: (a) Depends on the amount of phosphoric acid used.
To find out the exact mass of ammonium phosphate that is produced, one would typically use a balanced chemical equation and perform stoichiometric calculations. Remember, the balanced chemical equations provide the mole-to-mole ratios between reactants and products, which can then be used to calculate masses using the reactants' molar masses.