Definition

1. Noun:
   • A measure of concentration: Molality is a specific way to express the concentration of a solution. It is defined as the number of moles of a solute dissolved in one kilogram of solvent.

Usage

• Molality is used primarily in chemistry, especially in contexts involving colligative properties (like boiling point elevation and freezing point depression) because, unlike molarity, it is not affected by changes in temperature or pressure.
• It is denoted by the symbol m or b (e.g., a 0.5 m solution).
• The key distinction is that molality uses the mass of the solvent, not the total volume of the solution.

Examples

• Noun:
  • The molality of the sodium chloride solution was calculated to be 1.50 m.
  • Because the experiment required precise temperature studies, the chemist chose to use molality instead of molarity.

Advanced Usage

• "Molal" (adjective): Pertaining to or measured in molality.
  • The molal concentration remained constant despite the temperature change.

Variants and Related Words

• Molarity (n): A different concentration measure defined as moles of solute per liter of solution.
• Mole fraction (n): The ratio of the number of moles of one component to the total number of moles in a mixture.

Synonyms

• Molal concentration: A direct synonym for molality.

Notes

• Key Formula: Molality (m) = (moles of solute) / (kilograms of solvent).
• It is crucial to distinguish molality from the more common molarity. Molarity changes with temperature because it depends on solution volume, which expands or contracts. Molality does not.

Noun

1. concentration measured by the number of moles of solute per kilogram of solvent