Molar Solution vs. Normal Solution — What's the Difference?

A molar solution is based on the concept of molarity, which involves the number of moles of a substance dissolved in one liter of solution. It is a measure of the concentration of a solute in a solution. In contrast, a normal solution refers to the concentration of equivalents per liter of solution, where an equivalent is the amount of substance that reacts with or supplies one mole of hydrogen ions in an acid-base reaction, or one mole of electrons in a redox reaction.

The molarity of a solution is independent of the chemical reaction in which it is used. It only depends on the number of moles of solute. However, normality varies with the context of the chemical reaction because it depends on the equivalence factor, which changes based on the reaction.

Molar solutions are commonly used in stoichiometric calculations in various chemical reactions, where the concentration of the solute is of interest. Normal solutions are specifically useful in titrations and reactions where the reacting capacity of the solute is a key factor, such as acid-base titrations or redox reactions.

Preparing a molar solution requires knowledge of the molecular weight of the solute and the desired volume of the solution. To prepare a normal solution, one must consider the solute's equivalence factor in addition to its molecular weight.

In practice, molarity is a more universally applicable unit since it does not change with the type of chemical reaction. Normality, being reaction-specific, can be more complex to calculate and less consistently applied across different types of chemical analyses.