Normality is a measure of concentrationequal to the gram equivalent weight per liter of solution. is the measure of the reactive capacity of a molecule. The solute's role in the reaction determines the solution's normality. Normality is also known as the equivalent concentration of a solution. In chemistry, the equivalent concentration or normality of a solution is defined as the molar concentrationcidivided by an equivalence factor feq:
The unit symbol "N" is used to denote "eq/L" which is normality. Although losing favor, medical reporting of serum concentrations in "meq/L" still occurs.
Usage
There are three common areas where normality is used as a measure of reactive species in solution:
In redox reactions, the equivalence factor describes the number of electrons that an oxidizing or reducing agent can accept or donate. Here, can have a fractional value.
In precipitation reactions, the equivalence factor measures the number of ions which will precipitate in a given reaction. Here, is an integer value.
A normal solution contains a 1 normal concentration. Decinormal is one tenth of the normal concentration.
Examples
Normality can be used for acid-base titrations. For example, sulfuric acid is a diprotic acid. Since only 0.5 mol of H2SO4 are needed to neutralize 1 mol of OH−, the equivalence factor is: If the concentration of a sulfuric acid solution is c = 1 mol/L, then its normality is 2 N. It can also be called a "2 normal" solution. Similarly, for a solution with c = 1 mol/L, the normality is 3 N because phosphoric acid contains 3 acidic H atoms.
Criticism
Normality is an ambiguous measure of the concentration of a solution. It needs a definition of the equivalence factor, which depends on the definition of equivalents. The same solution can possess different normalities for different reactions. The definition of the equivalence factor varies depending on the type of chemical reaction that is discussed: It may refer to equations, bases, redox species, precipitating ions, or isotopes. Since feq may not be unequivocal, IUPAC and NISTdiscourage the use of normality.
