Molality — Science definition
Moles solute per kilogram of solvent.
Where it is taught
- Electrolytes & Colligative Properties — Solutions & Dissolved Particles, Physical Science: Chemistry, Grade 11
In use
Molality b is moles of solute per kilogram of solvent, unlike molarity which uses liters of solution.
Electrolytes & Colligative Properties
Questions using molality
Problem 1
Find molality of .30 mol solute in .60 kg solvent.
Hints
Write the relationship first; substitute with consistent units.
Answer and explanation
0.5 mol/kg
.30/.60=.50.
Problem 2
Compare molarity and molality denominators.
Answer and explanation
Molarity uses solution volume; molality uses solvent mass in kilograms.
Response criteria
- State a scientifically accurate conclusion.
- Show the calculation or mechanism that supports it.
- Include units, conditions, or limits where relevant.