Chemistry concentration unit · BEGINNER LESSON
Millimolar
Millimolar means millimoles per liter (mmol/L), a molar concentration unit. It tells how many thousandths of a mole of a substance are present in one liter of solution.
What it is
Millimolar is a way to report concentration, which is a measurement of how much of a substance is present in a given volume. In this unit, the amount is counted in millimoles and the volume is measured in liters. The prefix milli means one-thousandth, so 1 millimole is 10^-3 mole. The mole is a counting unit for amount of substance.
[1] Masses and masses [3] 1.4 Measurements - Chemistry 2e | OpenStax
Why scientists use it
Molar units are useful when the number of molecules matters more than the substance’s mass. The sources note that pharmacologists often prefer molar units because interactions between substances can be easier to understand when concentrations are written this way. In one example, plasma osmolarity became simpler to calculate when electrolytes, glucose, and urea were expressed in mmol/L.
How it is used in measurements
A measurement includes a number, a unit, and an uncertainty. Millimolar provides the unit part of a concentration measurement, usually alongside a numerical value such as 2 mM. The standard reference volume is the liter, so millimolar always describes amount per liter rather than a bare amount by itself.
[3] 1.4 Measurements - Chemistry 2e | OpenStax [1] Masses and masses
Limits and cautions
Millimolar is useful, but it is not always the best unit for every problem. The sources contrast molar units with mass units such as mg/L, which may be preferred when the exact molecular weight is unknown or when a mass-based description is more practical. The same concentration can also be written in different unit systems, so the unit must be read carefully.
SEE THE IDEA
How millimolar works
Count the substance in moles; millimolar uses millimoles, which are 10^-3 mole.
Use liters as the reference volume.
Divide millimoles by liters to get mmol/L, written as mM.
Shows how much substance is present in each liter of solution.
The amount is counted first, then compared with one liter of solution to express concentration.
Millimolar combines a small amount unit with a standard volume unit to describe concentration.
TRY IT YOURSELF
Test your understanding
Choose an answer, then check the explanation.
PUT IT TOGETHER
Match each concept to its meaning
Drag a label onto its description, or select a label and then select a description. This also works with a keyboard.
4 pairs to match
Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.