Equation and purpose
Concentration per mass solvent, temperature independent.
\[b = \frac{n}{m_{solvent}}\]
Concentration per mass solvent, temperature independent.
REARRANGEMENTS
$n = b·m_{solvent}$
Dimensional check: mol/kg ✓
Variables and units
| Symbol | Quantity | Unit | Notes |
|---|---|---|---|
| b | b | — | — |
| n | n | — | — |
| m_{solvent} | m_{solvent} | — | — |
Conditions and limitations
Solvent mass, not total mass; useful for colligative properties.
Worked example
0.100 mol in 0.250 kg water → 0.400 mol·kg⁻¹.
Molality
Concentration per mass solvent, temperature independent.
Equation
Inline: $b = \frac{n}{m_{solvent}}$$
Variables
| Symbol | Quantity | Unit | Notes |
|---|---|---|---|
| molality | mol·kg⁻¹ | — | |
| amount solute | mol | — | |
| mass solvent | kg | — |
Conditions and limitations
Solvent mass, not total mass; useful for colligative properties.
Rearrangements
Dimensional check: mol/kg ✓
Worked example
0.100 mol in 0.250 kg water → 0.400 mol·kg⁻¹.
Steps: write equation → substitute with units → check dimensional consistency → report with correct significant figures.
Common errors
- Using solution volume
- Swapping m and kg
Related resources
- solutions-concentration topic
- Calculators — linked only when a real calculator implements this formula.
- Constants — sourced constants with version when values are required.
Sources
- NIST Physical Constants 2022 — CODATA.
Reviewed 2026-08-21 by Editorial Team; due 2027-08-21.
Common errors
- Using solution volume
- Swapping m and kg
RELATED FORMULAS
C
Chemistry Fundamentals Editorial TeamAuthor
E
Editorial Review BoardReviewer
Editorial Team — transparent review placeholder
Reviewed August 21, 2026
SOURCES
- [nist-2022]NIST Physical Constants 2022 (2022). NISThttps://physics.nist.gov/constants