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# State law of multiple proportions.

Last updated date: 28th May 2024
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Hint: This law is stated by John Dalton and finds its application when more than one compounds are formed from two elements.This law can also be considered as a corollary of the Law of Definite Proportions.

Chemical combinations are measured by 5 laws: known as laws of chemical combination.
The 5 laws are :
(i) law of conservation of mass
(ii) law of definite proportion/composition
(iii)law of multiple proportion
(iv)Gay Lussac’s law of gaseous volume
Law of multiple proportions states that if two elements, combined to form more than one compound, the masses of one of the elements that combined with the fixed mass of the other, is in a simple whole number ratio.

As in the question, it's only referring to stating the law of multiple proportions, it will be better giving you an idea of law of multiple proportions by using an example as well (given below):
For example: Considering the reaction between ${ H }_{ 2 }$ and${ O }_{ 2 }$,
There can be two compounds $\left( { H }_{ 2 }{ { O }_{ 2 }\quad and\quad { H }_{ 2 }O } \right)$ that can be formed from the above two elements (applying different conditions for both the reactions).
First we can have a look at the two reactions and will closely examine the amount of reactants required in the each reaction,
${ H }_{ 2 }\quad +\quad { O }_{ 2 }\quad \rightarrow \quad { H }_{ 2 }{ O }_{ 2 }$ ------ (i)
${ H }_{ 2 }\quad +\quad { \frac { 1 }{ 2 } }{ O }_{ 2 }\quad \rightarrow \quad { H }_{ 2 }{ O }$ -------(ii)
We will now draw a table showing the masses of reactants in both the reactants.

 Equation number ${ H }_{ 2 }$ ${ O }_{ 2 }$ (i) 2 g 32 g (ii) 2 g 16 g

Here in the above two reactions, as we have stated in the law of multiple proportions,we can see that the mass of hydrogen in both the reaction remains fixed . ie, 2 g. And the other element which is combined with the fixed mass of ${ H }_{ 2 }$ is ${ O }_{ 2 }$.
Now, we need to look whether the masses of ${ O }_{ 2 }$in both the reactions (i) and (ii) are in a simple whole number ratio or not.
Masses of ${ O }_{ 2 }$ in reaction (i) and (ii) are 32 and 16 respectively.

Therefore, the ratio is 32:16 = 2:1, which is a simple whole number ratio.

Note: The existence of isotopes of hydrogen like ${ H }^{ 1 }$ or ${ H }^{ 2 }$ causes discrepancies (since they are having different atomic weights) . Hence, the same isotope or mixture of isotope should be used throughout the preparation of a series of compounds.