Definition

1. Noun:
   • Molal concentration: A measure of the concentration of a solute in a solution, expressed as the number of moles of solute per kilogram of solvent (not total solution). It is also known as molality.

Usage

• Noun:
  • Molal concentration is used in chemistry, particularly in contexts where temperature independence is important, as it is based on the mass of the solvent, which does not change with temperature.
  • It is a key concept in calculating colligative properties like boiling point elevation and freezing point depression.

Examples

• Noun:
  • The molal concentration of the sodium chloride solution was 0.5 m.
  • To calculate the freezing point depression, you first need to determine the molal concentration of the solution.

Advanced Usage

• "Molal concentration" vs. "Molar concentration": It is critical to distinguish molal concentration (molality, moles/kg solvent) from molar concentration (molarity, moles/liter solution). Molality is temperature-independent, while molarity is not.
  • For precise thermodynamic calculations, molal concentration is often preferred over molar concentration because the mass of solvent is unaffected by temperature changes.

Variants and Related Words

• Molality (n): The full term for molal concentration. The unit is mol/kg, often denoted by a lowercase 'm'.
  • The molality of the solution was 1.5 m.
• Solute (n): The substance dissolved in a solvent to form a solution.
• Solvent (n): The substance, typically a liquid, in which a solute is dissolved.

Synonyms

• Molality: The direct synonym for molal concentration.

Related Phrases

• Colligative property: A property of a solution that depends on the concentration of solute particles, such as molal concentration, but not on their identity.
  • The extent of boiling point elevation is a colligative property directly related to the molal concentration.

Noun

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