Molality

Molality is a unit of concentration used in chemistry and physics, especially when dealing with colligative properties. While the concentration unit molarity (moles/liter) is more useful for chemical reactions, and normality is most useful for acid-base reactions, molality is often the most convenient concentration unit when dealing with physical properties of solutions. It is defined as moles of solute per kilogram of solvent, and is a useful unit when measuring vapor pressure depression, boiling point elevation, freezing point depression and osmotic pressure of solvents.