Various chemical reactions take place according to the certain laws,
known as the Laws of chemical combination.
(1) Law of conservation of mass : It was proposed by Lavoisier and
verified by Landolt. According to this law, Matter is neither created nor
destroyed in the course of chemical reaction though it may change from one
form to other. The total mass of materials after a chemical reaction is same
as the total mass before reaction.
(2) Law of constant or definite proportion : It was proposed by
Proust. According to this law, A pure chemical compound always contains
the same elements combined together in the fixed ratio of their weights
whatever its methods of preparation may be.
(3) Law of multiple proportion : It was proposed by Dalton and
verified by Berzelius. According to this law, When two elements A and B
combine to form more than one chemical compounds then different weights
of A, which combine with a fixed weight of B, are in proportion of simple
whole numbers.
(4) Law of equivalent proportion or law of reciprocal proportion : It
was proposed by Ritcher. According to this law, The weights of the two or
more elements which separately react with same weight of a third element
are also the weights of these elements which react with each other or in
simple multiple of them.
(5) Gay-Lussac’s law : It was proposed by Gay–Lussac and is
applicable only for gases. According to this law, When gases
combine, they do so in volumes, which bear a simple ratio to each
other and also to the product formed provided all gases are
measured under similar conditions. The Gay-Lussac’s law, was based
on experimental observation.