The two important laws of chemical combination are:

i) Law of constant proportion:

The law states that “in a chemical substance, the elements are always present in definite proportions by mass.

For example: In ammonia (NH₃), nitrogen and hydrogen are always present in the ratio of 14:3 by mass, whatever the method

or source from which it is obtained.

In water, hydrogen and oxygen are always present in the ratio of 1:8 by mass, whatever the method or source from which water is obtained.

ii) Law of conservation of mass:

According to the law of conservation of mass states, atoms are neither created nor destroyed in a chemical reaction. This means that the total mass of the products formed in a chemical reaction must be equal to the mass of reactants consumed.

For example:

Sum of mass of reactants = Sum of masses of prodcuts