Definition

1. Adjective:
   • Relating to molality: The term "molal" specifically describes a solution concentration expressed as moles of solute per kilogram of solvent. It is the adjectival form of the noun "molality."

Usage

• "Molal" is a technical term used primarily in chemistry and physical sciences to specify solution concentration. It is distinct from "molar," which refers to moles per liter of solution. Use "molal" when the concentration measurement is based on the mass of the solvent, not the total volume of the solution.

Examples

• Adjective:
  • The chemist prepared a 0.5 molal sodium chloride solution by dissolving the salt in one kilogram of water.
  • The freezing point depression depends on the molal concentration of the solute.

Advanced Usage

• "Molal" vs. "Molar": A critical distinction in precise scientific work. "Molal" concentration (molality) is temperature-independent because it is based on mass, while "molar" concentration (molarity) can change with temperature as volume expands or contracts.
  • For precise thermodynamic calculations, molal concentrations are often preferred because they do not vary with temperature.

Variants and Related Words

• Molality (n): The physical quantity itself, defined as the number of moles of solute per kilogram of solvent.
  • The molality of the solution was calculated to be 1.2 m.
• Mole (n): The base unit in the International System of Units (SI) for amount of substance.

Synonyms

• None direct: In its specific technical sense, "molal" has no perfect synonym. Descriptive phrases like "expressed in molality" or "based on solvent mass" convey a similar meaning.

Related Phrases

• Molal solution: A solution whose concentration is given in molality.
  • The experiment requires a precisely prepared molal solution.
• Molal concentration: Another way to refer to the molality of a solution.
  • The colligative property is directly proportional to the molal concentration.

Adjective

1. designating a solution containing one mole of solute per kilogram of solvent