Question

What is the Law of Conservation of Mass?

Answer 1

Simply that mass is conserved in every chemical reaction.

Explanation:

Given the conservation of mass, if I start with `10*g` of reactants from all sources, at most I can get `10*g` of products. In practice, I am not even going to get that, because losses occur on handling and purification. Every chemical reaction that has ever been observed obeys this law.