Question

According to the law of conservation of mass, mass cannot be gained or destroyed in a chemical reaction. Why can’t you simply add the masses of two reactants to determine the total mass of product?

Answer 1

Explanation:

The law of conservation of mass states that mass is conserved which also means that it cannot be created or destroyed within the isolated system.

We can add the mass of the reactant and can be equal to the mass of the product. But in some cases, it will not work like:

If reactants are not in the mole ratio, there will be a limiting reagent.

If a gas is one of reactants or products.

Radioactive decay and  nuclear reactions(fission or fusion).