Question

explain the law of constant proportions?give any two examples.

Answer 1

In chemistry, the law of definiteproportion, sometimes called Proust'slaw or the law of definite composition, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation.

Answer 2

“In a chemical substance the elements are always present in definite proportions by mass”.

Even in earlier days, it was observed that many compounds contain two or more than two elements and each element was present in definite proportion irrespective of its source.

For e.g. If we take water from river or from an ocean, both had oxygen and hydrogen in the same proportion.

An Indicative Example

In this section we shall learn more about the topic with the simple example. Let us consider ammonia, every 17 gram of ammonia contains 14 gram of nitrogen and 3 grams of hydrogen irrespective of source. If we take 34 grams of ammonia, it will contain 28 gram of nitrogen and 6 grams of hydrogen. It’s clear that the ration by mass of ammonia, nitrogen and hydrogen is always 17:14:3. Today with the concept of atom, molecular mass and molar mass already explained, this law of chemical combination is very obvious. But in the early age of chemistry, it was a major breakthrough. On the basis of this theory only, Dalton’s gave its postulates about its atomic theory which became the base for our understanding of the chemistry.

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