Final answer:
To find the correct subscripts x and y for the aluminum-containing compound Mgx(ClO4)y, we need more information or analytical methods, since the data provided, primarily involving limiting reagents and reaction stoichiometry, do not directly pertain to the problem at hand.
Step-by-step explanation:
The question involves analyzing the composition of an aluminum-containing compound to determine the subscripts in its chemical formula. Given the information that the compound contains 44.98% oxygen by mass, we can start by considering the molecular weight contributions of oxygen in the perchlorate ion (ClO4) and balance it with magnesium (Mg). Since perchlorates have one chlorine and four oxygen atoms, and we know the atomic mass of oxygen (16 g/mol approximately), the total mass of oxygen atoms in one mole of ClO4 is 64 g. But magnesium does not directly bond with oxygen, and instead bonds with the ClO4 as a whole, indicating that subscripts x and y correspond to the stoichiometry of Mg with ClO4, not individual oxygen atoms.
The provided details for reactions and limiting reagents are not directly helpful for solving the given problem. To determine the correct subscripts for x and y, empirical experimentation, spectroscopic analysis, or more detailed compositional data would be needed.