X

Law of multiple proportion

Law of multiple proportion-

source : pinterest.com

Law of multiple proportion-

This law was given by John Dalton. According to this law,

 

”  When two elements combine to form two or more than two compounds, the weights of one of the element which combine with a fixed weight  of other,bear a simple whole number ratio.”

OR

” When two elements A and B combine to form more than one chemical compounds then different weights of A, which combine with a fixed weight of B, are in a proportion of simple whole numbers.”

Experimental Verification-

Nitrogen and oxygen combine to form five oxides such as nitrous oxide (N2O) ,nitric oxide (NO),nitrogen trioxide (N2O3),nitrogen tetraoxide (N2O4) and nitrogen pentaoxide (N2O5).

Oxides of             Nitrogen           Oxygen               Fixed wt. of nitrogen                    Wt.of oxygen combine with 14 gm. of nitrogen

N2O            28                16                   14                                           8

NO              14                 16                  14                                          16

N2O3         28                 48                 14                                          24

N2O4         28                 64                  14                                         32

N2O5         28                 80                  14                                         40

Ratio of oxygen in different compounds which combine with same weight of nitrogen

8  : 16 : 24 : 32 : 40

1  : 2  :  3 :  4 :  5

The simple whole number ratio favours Law of multiple proportion.

Problem 1 :

   Tin combines with oxygen to form two compounds having the following composition ;

                                   % of  Sn         % of Oxygen

Compound A            78.77               21.23

Compound B            88.12              11.88

Show that the above data follows the law of multiple proportion.

Solution –

In compound A ,

21.23 part of oxygen combines with 78.77 part Sn

1 part of oxygen combines with = 78.77 x 1 /21.23

                                                          = 3.7 part tin

In compound B ,

11.88 part of oxygen combines with 88.12 part Sn

1 part of oxygen combines with = 88.12 x 1 /11.88

                                                          = 7.4 part tin

Ratio of Sn with one part of oxygen = 3.7  :  7.4

                                                                  =  1    :   2

So data follows law of multiple proportion.

Problem 2 :

  Carbon combines with hydrogen to form compounds having the following composition ;

                                   % of  C         % of H

Compound A            75.0               25.0

Compound B            85.7             14.3

Compound C            92.3             7.7

     Show that the above data illustrate the law of multiple proportion.

Solution –

In compound A ,

75.0 part of Carbon  combines with 25.0  part Hydrogen

1 part of Carbon combines with = 25.0 x 1 / 75.0

                                                          = 0.33 part hydrogen

In compound B ,

85.7 part of Carbon  combines with  14.3  part Hydrogen

1 part of Carbon combines with = 14.3 x 1 / 85.7

                                                          = 0.166 part hydrogen

In compound C ,

92.3 part of Carbon  combines with  7.7  part Hydrogen

1 part of  Carbon combines with = 7.7 x 1 /  92.3

                                                           = 0.08 part hydrogen

 

Ratio of Hyrogen  with one part of Carbon = 0.33 :  0.166 : 0.08

                                                                               =  4     :   2  :    1

So data follows law of multiple proportion.

 

lavannya bhatia:
Related Post