Laws of chemical combination

Laws of chemical combination

(1)Laws of conservation of mass-

 This law is given by the French scientist A. Lavosier in 1774. 

          According to this law-

In any physical or chemical change the total mass of the products is always equal to the total mass of the reactants.

This law is also represents as -

Matter is neither be created nor be destroyed in any physical or chemical change but it transformed into one form to another form.

  

For example-

   2H2O  ------> 2H2  + O2

  36 gram      4 gram   32 gram

(2)Law of constant proportion-

This law is given by the French scientist Proust in 1799. 

          According to this law-

In any chemical compound , the elements presents in the compound are always present in a fixed proportion by mass.

  For example-

(a)In the compound CO2 the ratio of Carbon and Oxygen is always found in the 3:8 by mass.

(b) In the compound H2O the ratio of Hydrogen and Oxygen is always found in the 1:8 by mass.

(3)Law of Multiple proportion-

 This law is given by the scientist John Dalton in 1804. 

          According to this law-

When two elements are combined to each other and form two or more than two compound then mass of one element which is combined to the fixed mass of other element,is found in a simple ratio.

For example-

Two elements Carbon and Oxygen formed Carbon mono oxide(CO) and carbon dioxide (CO2) after the combination of each other. In the carbon monoxide the ratio by mass of C and O is 12:16. On the other hand the ratio of C and O in CO2 is 12:32. So the fixed mass of carbon (12part) is reacts with different - different mass of Oxygen. So in the both compounds the ratio by mass of the oxygen is 16:32 or 1:2 .

(4) Law of Reciprocal proportion-

This law is given by the German scientist Ritcher in 1792. 

          According to this law-

When the two elements are combined with different ways by the fixed mass of the third element then the same ratio or its a multiple ratio by mass is found in which they are combined to each other.

For example-

Let in the three elements Hydrogen (H) , Sulpher(S) and Oxygen (O) , H and O formed H2O , S and O formed SO2 , H and S formed H2S.

         The ratio of H, O in H2O is 2:16 or 4:32 whereas the ratio of S and O in the SO2 is 32:32.

              So ratio of H and S which is combined with the fixed mass (32 part) of oxygen is 4:32 or 1:8.   ....................(i)

            When H and S formed H2S ,then the ratio of H and S is 2:32 or 1:16  ................................(ii)

 So the ratio of (i) and (ii) is-

   1        1

  ----  :  -----   Or   2:1

    8       16

So, they are present in the simple ratio.

(5) Gay Lussac's Law -

This law is given by the scientist Gay Lussac in 1808.

          According to this law-

When the gasses are chemically combined with each other then the volume of reactants and the volume of the products are found in the simple ratio when the temperature and pressure are fixed.

For example-

 H2(g)   +     Cl2(g)  ------->  2HCl(g)

1volume   1 volume       2 volume