Question

state law of conservation of masses and law of constant proportion

Answer 1

Law of Conservation of Mass. The law of conservation of mass states that the net change in mass of the reactants and products before and after a chemical reaction is zero. This means mass can neither be created nor destroyed. In other words, the totalmass in a chemical reaction remainsconstant.

Answer 2

given by french chemist Lavoisier law of conservation of mass states that
"mas can neither be created nor be destroyed in a chemical reaction"
given by Proust .law of constant promotion states that
" in a compound, the constituent elements are always present in a definite proportion by weight "