Question

What is Law of constant proportion?

Answer 1

it was given by Joseph Louis Proust.
the law of constant proportion states that in a chemical substance the elements are always present in definite proportion by mass

eg: in a compound such as water the ratio of mass of hydrogen to the mass of oxygen is always 1:8. thus if 9 grama of water is decomposed we always obtain 1 gram of hydrogen and 8 grams of oxygen.

hope it helps...

Answer 2

It states that,'in a pure chemical substance, the elements are always in definite proportions by mass.'