The concentration of ions in a solution can also be expressed by the
number of charges they bring to the solution.
The unit used is Electrical Equivalents/liter of solution.
It is calculated with the following equations:
Equivalents/liter of solution of an ion = Equivalents/kg of water of an ion=
molarity of the ion x valence of the ion
molality of the ion x valence of the ion
Thus, "Electrical equivalent" is also another way of saying "mole of positive charges"
or "mole of negative charges".
5 Equivalents/liter of solution" is like saying 5 mole of positive (or negative) charges / liter of solution
8 Equivalents/kg of water is like saying 8 mole of positive (or negative) charges / kg of water.
2 Eq / liter of calcium in a solution means
- that there there are 2 moles / liter of positive charges coming from the calcium
- that the concentration of calcium ions (Ca++) is 1 mole / liter.
The concentration of all the positive charges in a solution is calculated by doing the sum of all the positive charges given by all the cations present in the solution.
The concentration of all the negative charges in a solution is calculated by doing the sum of all the negative charges given by all the anions present in the solution.
The weight in grams of one Electrical Equivalent of an ion
= Molecular Weight of the ion / Valence of the ion
This value is called the Equivalent Weight of the Ion.
It is the quantity of ion in grams that has to be dissolved in water
in order to bring 1 mole of positive (or negative) charges to the solution.
The Equivalent weight of calcium is 40/2 = 20g