The student originally has 252 grams of water in this experiment.
LAW OF CONSERVATION OF MASS:
The law of conservation of mass explains that matter(mass) can neither be created nor destroyed but can be changed from one form to another.
This means that in a chemical reaction, the sum of the masses of the reactants must equate to the total mass of product(s).
According to this question, a student conducts an experiment to separate water into hydrogen and oxygen. The student collects 28.0 g of hydrogen and 224.0 g of oxygen.
Since hydrogen and oxygen are the constituent elements of water, the sum of their masses must equate the mass of water.
Therefore, 224g of oxygen + 28g of hydrogen = 252g of water.
