Question

I can't understand Normality and Equivalent weight?

Answer 1

@JFraser

Answer 2

i don't use these terms either, they are terribly out-dated.

normality is a term of concentration, and equivalent weight usually means "stoichiometrically equivalent", so if the equivalent reactant is 1 mole, the equivalent weight is the molar mass

Answer 3

Can we take an example here?

Answer 4

For better understanding.

Answer 5

H2SO4 + 2OH-= 2H2O + SO42-

Answer 6

Let us take that as example ^

Answer 7

\(H_2 SO_4 + 2 OH ^{-} \rightarrow 2H_2 O + {SO_4 }^{2-}\)

How to calculate the equivalent weight of \(H_2 SO_4\) here?

@chmvijay and @jfraser

Answer 8

H2SO4
Molecular weight of sulfuric acid (H2SO4) = 98.07 g/mol
Theoretical Equivalent weight of sulfuric acid (H2SO4) = 49.03 g/equivalent of H+

I think I studied in the book like :
Divide the molecular weight of an acid by the number of replaceable H atoms;
Divide the molecular weight of a base by the number of OH groups; and
Divide the molecular weight of a salt by the number of H's or OH's that reacted to form it.

..i.e Equivalent weight = molecular weight/valence ...
For compounds like H2SO4, MgSo4, etc ... the valence =2 !!

Is this what you are looking for ? @mathslover

Answer 9

I am like JFraser: I have never used equivalent weight.

Normality can be useful. I sometimes use it for redox reactions.
If you have the following half reaction:

\(MnO_4^- +8H^++5e^-\rightleftharpoons Mn^{2+}+4H_2O\)

then a 1 M solution of acidic permanganate ions will be considered 5 N because 1 mole of permanganate ions can accept 5 moles of electrons.

The problem with normality is that a given compound can react according to different half equations when the other reactant changes, so a 1 M solution can be 5N with a reactant A and 3N with a reactant B.
This is why we have limited to only a few well-chosen cases the use of this notation.

Answer 10

Thanks a lot for the help @Koikkara and @Vincent-Lyon.Fr !