In order to properly calculate how much reactant needs to be used in a chemical reaction to produce a specific amount of product, what method of chemical calculation must be used

First, a mandatory stoichiometric balance must be made, and second, the degree of purities and impurities that the reagents have must be analyzed to see how many products they would have.

It is essential that this is taken into account since not all chemical compounds (reactants) are 100% pure and therefore their entirety does not become a product.

Explanation:

As for the stoichiometric balance, it is fundamental since if the equation is not balanced all the data will be wrong.

Many times the quantity in grams and another measurement of the products are obtained, taking into account a standard value of how many reactants will give x quantity of products, a simple rule of three could be made and thus be able to determine in a simpler way how many reactants were catalyzed in reaction.

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.