A LITTLE LIGHTBULB MOMENT
General chemistry: solutions, gases and equilibrium
Molarity means moles of solute per liter of solution
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Picture sugar dissolving in a marked measuring jug.
The idea behind the cue
Molarity is concentration defined as moles of solute per liter of solution, not per liter of solvent. Because the denominator is total solution volume, adding solute can change the volume and therefore the molarity. It is temperature-sensitive whenever volume changes.
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Short & simple
Picture sugar dissolving in a marked measuring jug.
Acronym
MML — Mischievous Moose Limbo.
Story
A sugar cube dives into a measuring jug, and the line on the glass shows the final volume after dissolving. The drink’s strength depends on how many moles are packed into each liter of the whole mixture.
Connect the pieces
- M (Mischievous) → Molarity: Molarity is moles of solute per liter of total solution, not per liter of solvent.
- M (Moose) → Moles: The amount of solute is counted in moles, and it is divided by solution volume.
- L (Limbo) → Liter: The denominator is liters of solution, so changing solution volume can change molarity and make it temperature-sensitive.
- Mischievous · Molarity: Molarity is moles of solute per liter of total solution, not per liter of solvent.
- Moose · Moles: The amount of solute is counted in moles, and it is divided by solution volume.
- Limbo · Liter: The denominator is liters of solution, so changing solution volume can change molarity and make it temperature-sensitive.
Know the limits
Uses total solution volume, so it differs from molality, which uses mass of solvent.
Further reading · OpenStax science and mathematics textbooks ↗Check your understanding
Which expression correctly defines molarity?
A. moles of solute / liters of solution
B. grams of solute / liters of solvent
C. moles of solvent / liters of solution
D. grams of solution / liters of solute
Reveal explanation
moles of solute / liters of solution
Molarity is moles of solute per liter of total solution.