molal

IPA/ˈməʊ.ləl/
IPA/ˈmoʊ.ləl/

molal — adjective

  • molalpositive
  • more molalcomparative
  • most molalsuperlative

1. describing a solution in which the concentration is expressed as moles of dissol

1.adjectiveC1
Definition

describing a solution in which the concentration is expressed as moles of dissolved substance per unit mass of solvent

Example

The lab technician prepared a 0.5-molal potassium chloride solution because its concentration is unchanged by cooling.

attributive use: [number]-molal solution of [substance]

Professor Amara explained that molal concentration stays the same even when the temperature changes.

collocation: molal concentration

Common collocations
  • molal solution
  • molal concentration
  • [number]-molal
  • molal quantity
  • molal freezing-point depression
Synonyms
  • molality-based

    less common, descriptive compound used when emphasizing the measurement system

Antonyms
  • molar

    refers to concentration per liter of solution rather than per kilogram of solvent

Grammar Patterns

[number]-molal solution of [substance]

molal [noun]

Usage Note

Frequently used attributively before nouns such as 'solution' or 'concentration'. Unlike 'molar', molal values do not change with temperature because they are based on mass rather than volume.

Common Mistakes

We prepared a 1-molal solution by adding one mole of salt to one liter of water.
We prepared a 1-molal solution by adding one mole of salt to one kilogram of water.
Molal concentration uses mass of solvent (kilograms), not volume (liters).
The molal concentration changed when we heated the solution.
The molal concentration stayed the same when we heated the solution.
Molality is based on mass, which does not change with temperature, unlike molarity.

Word family

  • molality
    nounC1
  • mole
    nounB2
  • molar
    adjectiveC1
  • molarity
    nounC1

Synonym discussion

Sense: adjective/1

'Molal' and 'molar' both describe solution concentration but use different units. 'Molal' refers to moles of solute per kilogram of solvent, so the value does not change with temperature. 'Molar' refers to moles per liter of solution, which can shift when temperature changes because liquids expand or contract. The noun 'molality' names the property itself ('the molality is 0.5'), while 'molal' works as an attributive adjective ('a 0.5-molal solution'). 'Concentrated' is a general everyday term meaning 'having a large amount of solute' — it does not indicate any exact numerical measure. For example: 'The team chose a molal solution because the experiment ran at 80 °C and they needed a concentration that would not change with heat.'

molar ↗molalityconcentrated ↗

Common collocations

Nouns

Phrases

  • per kilogram of solvent
  • moles per kilogram

Etymology

LatinGermanEnglish

Coined in the early 1900s in chemistry literature from 'mole' (the SI base unit for amount of substance) and the adjective-forming suffix '-al' (meaning 'relating to'). 'Mole' was introduced by German chemist Wilhelm Ostwald in 1893 as a shortened form of 'Molekül' (molecule), which traces back to Latin 'molecula' meaning 'a small mass'. The adjective 'molal' was created specifically to describe concentration measured per unit mass of solvent, distinguishing the concept from 'molar' (measured per unit volume).

First known use

1905

1905, in the meaning defined above