Question

Phosphorus forms two oxides \[{{\text{P}}_2}{{\text{O}}_3}{\text{ and }}{{\text{P}}_2}{{\text{O}}_5}\] . Which law can be proved by the weights of P and O?
A.Constant proportion
B.Multiple proportion
C.Reciprocal proportion
D.Definite proportion

Answer 1

Hint: Various laws were given to describe chemical composition of a compound but there laws have certain limits and applications. Such chemical composition of a compound can be described by a particular law.

Complete answer:
Various laws of chemical combination are:
Law of indestructibility of matter or conservation of mass was given by Lavoisier. This law states that in all chemical changes the total mass of the system remains constant or we can say in a chemical reaction mass is neither created nor destroyed.
Law of constant proportion was given by Louis proust. This law states that chemical composition of a compound remains constant whether it is obtained by any method or taken from any source. This can simply be understand by taking example of carbon dioxide as it is observed that carbon and oxygen are always combined in the ratio of \[\left( {12:32} \right){\text{or}}\left( {3:8} \right)\] . A pure chemical compound always contains a fixed ratio by weight or mass of its constituent element irrespective of the source from which it is obtained.
Law of multiple proportions was given by Dalton. This law states that if two elements combine to form more than one compound, then the different masses of one element which combine with a fixed mass of the other element bear a simple ratio to one another. For example Nitrogen and Oxygen combine to form five stable oxides:

Compound	Parts of nitrogen	Parts of oxygen
\[{{\text{N}}_2}{\text{O}}\]	28	16
\[{{\text{N}}_2}{{\text{O}}_2}\]	28	32
\[{{\text{N}}_2}{{\text{O}}_3}\]	28	48
\[{{\text{N}}_2}{{\text{O}}_4}\]	28	64
\[{{\text{N}}_2}{{\text{O}}_5}\]	28	80

The masses of oxygen which combine with the same mass of nitrogen in the five compounds bear a ratio \[16:32:48:64:80\] or \[1:2:3:4:5\] . Similarly, Phosphorus and Oxygen combines to form two oxides \[{{\text{P}}_2}{{\text{O}}_3}{\text{ and }}{{\text{P}}_2}{{\text{O}}_5}\] and here masses of oxygen which combines with same mass of phosphorus bear a simple ratio of \[3:5\] .
Thus, the correct option is B.
Note:
However, law of multiple proportions fails to work with non stoichiometric compounds and also does not work or apply with polymers and oligomers.