Molarity, Molality, or Normality? (A Quick Review)

Molarity

Molarity (M) is defined as the number of moles of solute per liter of solution.
molarity = moles of solute / liters of solution

Molality

Molality (m) is defined as the number of moles of solute per kilogram of solvent.
molality = moles of solute / kilograms of solvent
Although their spellings are similar, molarity and molality cannot be interchanged. Compare the molar and molal volumes of 1 mol of solute dissolved in CCl₄ (d = 1.59 g / mL)
By definition, a 1 M solution would contain 1 mol of solute in exactly 1.00 L of CCl₄ , and a 1 m solution would contain 1 mol of solute in 629 mL of CCl₄ .
1 kg of CCl₄ x  (1000 g /  1 kg) x (mL / 1.59 g) = 629 mL CCl₄

Normality

Normality (N) is another ratio that relates the amount of solute to the total volume of solution.
It is defined as the number of equivalents per liter of solution:
normality = number of equivalents / 1 L of solution
There is a very simple relationship between normality and molarity:

N = n × M (where n is an integer)

For an acid solution, n

is the number of H⁺ provided by a formula unit of acid.

example:

A 3 M H₂SO₄ solution is the same as a 6 N H₂SO₄ solution.

For a basic solution, n

is the number of OH^- provided by a formula unit of base.

example:

A 1 M Ca(OH)₂ solution is the same as a 2N Ca(OH)₂ solution.

Remember!The normality of a solution is NEVER less