Page 16 - Pharmaceutical analytical chemistry |

Concentration of standard solutions

1. Molar concentration
The molar concentration of a solution of a chemical species is the
number of moles of that species contained in one liter of the solution.
The unit of molar concentration is molarity (M) which has the
dimensions of mol L-1. Molarity also expresses the number of millimoles
of a solute per milliliter of solution:

Analytical Molarity
The analytical molarity of a solution gives the total number of moles of a
solute in one liter of the solution. It describes how a solution has been
prepared. For example, a sulfuric acid solution that has an analytical
concentration of 1.0 M can be prepared by dissolving 1.0 mole or 98 g of
H2SO4 in water and diluting to 1.0 L.
Equilibrium (or species) Molarity
It expresses the molar concentration of a particular species in a solution at
equilibrium. It is necessary to know what happens to the solute when it is
dissolved in a solvent. For example, the species molarity of H2SO4 in a
solution with an analytical concentration of 1.00 M is 0.00 M because the
sulfuric acid is entirely dissociated into ions.

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