The Law of Conservation of Mass

The fundamental principle at play is the Law of Conservation of Mass. This law states that in a closed system, the total mass of the reactants before a chemical reaction must equal the total mass of the products after the reaction.

Decomposition of Water

The decomposition of water (H₂O) into hydrogen (H₂) and oxygen (O₂) can be represented by this equation:

2H₂O → 2H₂ + O₂

Calculating Product Mass

Since the total mass must remain constant, the total mass of the products (hydrogen and oxygen) will be 10 grams, the same as the mass of the water reactant.