The concentration of acid (or base) in a solution can also be expressed by the maximum number of H+ (or OH-) it can give. The unit used is Equivalents/liter of solution. It is calculated with the following equations:
Equivalents/liter of an acid solution =
molarity of the acid in the solution x # of all the H+ it can give
Equivalents/liter of a basic solution =
molarity of the base in the solution x # of all the OH- it can give
As you can see, "Equivalent" is also another way of saying
"mole of all the H+ (or OH-) the acid (or base) can give".
Equivalents/liter of solution"
is like saying mole of all H+ (or OH-) / liter
of solution that can be given by the acid (or the base)
This quantity expressed in Equivalents/liter of solution is also called NORMALITY (N) of a solution
A 0.100M solution of Phosphoric acid (H3PO4)
can release 0.100 x 3 = 0.300 mole of H+ / liter of solution.
The concentration of this solution is 0.300Eq/L: its normality
is 0.300 N.
The weight in grams of one Equivalent of acid (or base)
= Molecular Weight of the acid (or base) / # of H+ (or OH-) this molecule can give
This value is called the
Equivalent Weight of the acid (or base).
It is the quantity of acid (or base) in grams that has to be dissolved in water
in order to provide 1 mole of H+ (or OH-) to the solution.
The Equivalent weight of H3PO4 is 98/3 = 32.7g