Question

Explain the experiment in detail performed by Joseph Proust to validiate the law of definite proportions

Class - 11th
Chapter - Some basic concepts of chemistry

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Answer 1

Explanation :-

The 'Law of Constant/Definite proportions' was given by French Chemist Joseph Proust in the year 1799.

Experiment :-

For this, Proust took two samples of Copper(II) Carbonate [CuCO₃]. One was natural and the another was synthetic.

Experimentally he found that the composition of elements Copper, Carbon and Oxygen was same for both the samples.

→ Copper = (63.5/123.5 × 100) = 51.42 %

→ Carbon = (12/123.5× 100) = 9.78 %

→ Oxygen = (48/123.5 × 100) = 38.8 %

[Percentage compositions are approx].

Conclusion :-

From this, he concluded that whatever is the source of a compound, but it contains same elements combined together in same propertion by mass.

From this we can state the law as :-

"A chemical compound always contains same elements combined together in same proportion by mass".

Some other examples :-

Let us take another compound 'CO₂' [Carbon dioxide] .

Mass ratio :-

= 12 : 16 × 2

= 12 : 32

= 3 : 8

It can be shown experimentally that different samples of Carbon dioxide contain Carbon and Oxygen in a fixed mass ratio of 3 : 8 .

Also in the same way , pure water [H₂O] obtained from different sources such as river, well, spring etc will always contain hydrogen and oxygen combined in the ratio of 1 : 8 by mass.

Answer 2

Required Answer :-

The law of definite proportion was made by Joseph Proust in which he tells about the composition of element in compounds. In it he also tells that every compound has element in fixed ratios.

Let's take example of Carbon dioxide

Carbon dioxide consist of carbon and oxygen

Now

Carbon - 12

Oxygen - 16

C O₂

(12) : (16)(2)

12 : 32

3 : 8

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