IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

nishant_delhi

Can some1 plz.. teach me how to find the oxidation no.(O.N.) for a given compound by giving some example or any easy method.

Like in (NH₄)₂SO₄ If we have to calculte O.N. for N 1st we should know the O.N. for H and SO4 ,i know it is +1 for H but how to find O.N. for SO_4.Im totally confused with this topic plz.. help guys. (rates assured)

izzac

SO4 is always 2-
as in H2SO4

madman

for any species ionic or neutral first look at the total charge of the species
the sum of charges on each of the individual atoms of the molecule must be equal to this charge
knowing this you can easily find the oxidation state
in addition to this you must also know the oxidation states of a few elements (which almost always take the same value)
for instance fluorines OS is always -1
oxygens is always -2 except in oxides of alkali metlas like
KO2
Cl,Br,I all have -1 OS (excluding oxygen compounds)
for these rules you can always look at the standard rules for detection of oxidation state given in any book.

lakshmis.kvasn

In H2SO4, the SO4 group has O.N -2. Two H atoms are attached to it! The molecule is neutral. Therefore there must be two positive charges to cancel the the 2 -ve charges. therefore the 2 H atoms will take up one +ve charge each to cancel the -ve charge. The net charge on an atom is called its oxidation number! It is also good to remember that sum of O.N of all atoms in a molecule is 0. In an ion, the sum of O.N. of all atoms is the total charge of ion!

Hope I made u understand, at least a little bit!

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