User:Vis M/sandox 1

Formality or formal concentration is defined as the number of gram formula masses of solute present in one liter of solution. It is denoted by the symbol F.

A solution with formality equal to one is called a formal solution.

It is commonly used in expressing concentration of ionic solutes and other electrolytes, which when dissolved do not exist in molecular form. Further, the constituents are present as a network of ions in ionic solutes and not as discrete molecules. Hence only empirical formulas are known and concentration has to be expressed in terms of formula mass.

Formality defines the makeup concentration while molarity denotes equilibrium concentration. If the substance dissolves without any dissociation, then molarity and formality will be equal to each other.

Like molarity and normality, formality changes with temperature.

Expression
The mathematical expression for formality, $$F$$ is given by,
 * $$F = \dfrac{n_f}{V}$$
 * where $$n_f$$ is the gram formula mass of the constituent (ratio of mass of the constituent taken to the formula mass of it), and $$V$$ the volume of solution.

i.e., $Formality = Mass of solute present⁄Formula mass of solute × Volume of solution$