How is molality defined in a solution?

Molality is defined as the number of moles of solute present in one kilogram of solvent. This measurement is important in chemistry because it provides a way to express concentration that is independent of temperature and pressure, which can affect the volume of a solution. By focusing on the mass of the solvent rather than the total volume of the solution, molality is particularly useful in various calculations involving colligative properties, such as boiling point elevation and freezing point depression.

Using moles of solute rather than grams avoids confusion that can arise from differences in molar mass and allows for direct comparisons between different solutes. Additionally, since molality considers the mass of the solvent, it remains constant regardless of temperature, unlike molarity, which relies on volume and can change with temperature fluctuations. Thus, defining molality in terms of moles of solute per kilogram of solvent provides a consistent and practical measure for laboratory and real-world applications.