EQUIVALENT MASS

 


EQUIVALENT MASS 

Equivalent mass of a substance is the number of parts by mass of a substance which combines with 1.008 parts by mass of hydrogen,8 parts by mass of oxygen.

Equivalent mass of an element=Atomic mass/valency

EQUIVALENT MASS OF ACID 

Equivalent mass of an acid is the number of parts by mass of it which can supply one part by mass of replaceable hydrogen.

1 gram equivalent mass of an acid is that mass of it which contains one gram equivalent mass of replaceable hydrogen atom.

Equivalent mass of acid = molecular mass /basicity

Eg-(I) The numberof replaceable hydrogen atoms in HCl is 1. Thus ,the basicity of HCl is 1 or is it monobasic.

         

        
(ii)The basicity of H2SO4 is 2,since it contains 2 replaceable H2 atom,so it is called dibasic.

 
EQUIVALENT MASS OF A BASE

Equivalent mass of base is that mass of it which can neutralise 1 gram equivalent mass of the acid.

Eg:-The no.of hydroxyl group in NaO+ is 1.
Thus,it's acidity is 1 , so it is monoacidic base.




Equivalent mass of base = molecular mass/ acidity

Molecularass of Ca(OH)2 =74
Eq.mass=74/2=37

EQUIVALENT MASS OF SALT

Equivalent mass of simple salt is that mass of it which contains one gram equivalent of the metal or a radical.
Eg.  One Molecule of potassium chloride (KCl) contains 35.5 parts by mass of chlorine since 35.5 is the equivalent mass of chlorine.

Therefore,the equivalent mass of KCl is equal to its molecular mass that is 74.5 .

EQUIVALENT MASS OF SOME OXIDISING AND REDUCING AGENTS

Equivalent mass of an oxidizing agent or reducing agent is defined as the number of parts by mass of it which combines with or displace 8 parts by mass of oxygen or 35.5 parts by mass of chlorine.


EQUIVALENT MASS OF OXIDANTS

Equivalent mass of Oxident is equal to the mole molecular mass divided by number of electrons lost of gained by one Molecule of the substance in a redox reaction.

equivalent mass of oxidising agent=Molecular mass/no.of electron gain.




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