Final answer:
The mass of any of the reactants or products in the chemical equation wA + xB → yC + zD can be determined from the mass of A and the molar masses of all substances, utilizing stoichiometry and the law of conservation of mass.
Step-by-step explanation:
Based on the chemical equation wA + xB → yC + zD and knowledge of the mass of substance A and the molar masses of A, B, C, and D, one can determine the mass of any of the reactants or products. This is accomplished through a series of mass-mass calculations. First, the known mass of A is converted to moles using its molar mass. Then, using the stoichiometry of the balanced chemical equation as conversion factors, moles of A are converted to moles of B, C, or D. Finally, these mole amounts are then converted back to masses using the respective molar masses of B, C, or D.
Using this process ensures that the law of conservation of mass is obeyed, as the total mass of reactants will equal the total mass of products. The stoichiometric relationships presented in the equation are in terms of moles, which can be easily related to mass using the molar mass. Therefore, the correct answer to the student's question is option (a) the mass of any of the reactants or products.