how can we say that atoms have a definite proportion ?

CBSE Class 9 Answered

how can we say that atoms have a definite proportion ?

Asked by Denith Lekshmi | 30 Oct, 2013, 07:29: PM

Expert Answer

We don't say 'Atoms have definite proportion'. It is defined as - ''In a chemical substance elements are always present in a definite proportion by mass''.

Law of Definite/constant proportion

Chemist, Proust analyzed the chemical composition of a large number of compounds to determine the type of elements present and the percentage of the elements present in them.
He concluded that, each compound had the same elements, in the same proportion irrespective of the source from which it was obtained or the method used for preparation.
Based on these observations, he formulated the law of constant proportions.
According to the law, "In a chemical substance elements are always present in a definite proportion by mass".

For example, water obtained from any source will have the same two elements hydrogen and oxygen present.2 grams of hydrogen and 16 grams of oxygen form a molecule of water. The proportion of hydrogen and oxygen is 1:8 by mass. This proportion will always remain the same irrespective of the source of water.

Similarly, carbon dioxide obtained from any source will contain the same two elements, carbon and oxygen.12 grams of carbon and 32 grams of oxygen from a molecule of carbon dioxide. Carbon dioxide obtained from any source will always have the proportion of carbon and oxygen as 3: 8 by mass.

Answered by Hanisha Vyas | 08 Nov, 2013, 05:40: PM