Disproportionate Reactions:

A redox reaction in which a same element present in a particular compound in a definite oxidation state is oxidized as well as reduced simultaneously is a disproportionate reaction.

            Disproportionate Reactions

            n factor of overall reaction = n1 × n2 / n1 + n2



MnO4 + 8H+ + 5e → Mn+2 + 4H2O
n factor of KMnO4 = 5


Find the n factor of Na2S2O3 in the following reactions.
(a)  Na2S2O3 + I2 → NaI + Na2S4O6
Sodium thio         sodium tetra
Sulphate                thionate
(b)  Na2S2O3 + I2 → NaI + Na2SO4


(a) Change in oxidation number of sulphur=|+2-2.5|=0.5
Change in oxidation number per molecule =0.5×2
∴ n factor of Na2S2O3 = 1

(b)  Change in oxidation number of sulphur=|2-6|=4
Change in oxidation number per molecule =4×2
∴ n factor of Na2S2O3 = 8

 => Consider the salt Ax By to undergo a reaction so that the element A undergoes a change in O.S. but is present in more than one product with the same oxidation state i.e. A+cxBy → A+faBy + A+fgH
(the superscripts denote the oxidation state of the respective elements).

∴ n=|xc-xf|

=> Salts that react in such a way that more than one type of atom in the salt undergoes oxidation state Change.
A+cxBy → A+faE + JxB-1

In this case both A and B are changing their O.SO. ‘s and both of them are either getting oxidized or reduced. In such a case n factor of the compound is the sum of the individual n factors of A and B. i.e.|xc-xf| + |-xC- (-yi)|. Then n factor of A can be understood which is |xc-xf|. The n factor of B is |-xc-(-yi)|


Law of Chemical equivalence:

It states that in any chemical reaction the equivalents of all the reactants and products must be same.


Eq. of A=Equivalents of ‘B’=Equivalents of ‘C’

Equivalents of ‘A’ = (Weight of ‘A’)/Equivalent weight of ‘A’

Or Equivalents of ‘A’ = no. of moles of ‘A’ x n-factor

A + B + C → product

If A & B do not react with each other but C react with both A & B then

Gm eq. of A + Gm eq. of B= gm eq. of C


Meq. Of A + Meq. Of B = gm Meq. Of C

« Click Here for Previous Topic Click Here for Next Topic »

Click Here for Class XI Classes Chemistry All Topics Notes

You wish to report grammatical or factual errors within our online articles, you can let us know using the article feedback form.