🧪 Molality Calculator | Convert Molarity to Molality Online Tool 📊
Calculate molality from molarity, mass percent, or mole fraction with our free chemistry calculator
🧮 Molality Calculator
Use our free online molality calculator to convert between different concentration units in chemistry solutions.
Calculate Molality
Result
The molality of your solution is:
Molality (m) = moles of solute / kilograms of solvent
Convert From Molarity
🔍 What is Molality?
Molality (m) is a measure of the concentration of a solute in a solution. Unlike molarity, which depends on the volume of the solution, molality depends only on the mass of the solvent. This makes molality particularly useful in situations where temperature changes might affect the volume of the solution.
The formula for molality is:
Molality (m) = moles of solute / kilograms of solvent
Key Features of Molality:
- Temperature-independent (unlike molarity)
- Expressed in moles per kilogram (mol/kg)
- Used in colligative property calculations
- Preferred in precise thermodynamic measurements
⚖️ Molarity vs Molality: Key Differences
Understanding the difference between molarity and molality is crucial in chemistry calculations:
| Feature | Molarity (M) | Molality (m) |
|---|---|---|
| Definition | Moles of solute per liter of solution | Moles of solute per kilogram of solvent |
| Temperature Dependence | Changes with temperature | Remains constant |
| Units | mol/L | mol/kg |
| Preferred Use | General laboratory work | Colligative properties, precise work |
Relation Between Molarity and Molality
The relationship between molarity (M) and molality (m) can be expressed as:
m = M / (density of solution – (M × molar mass of solute / 1000))
This is why our molality calculator with density can accurately convert between these units.
📝 How to Calculate Molality
Follow these steps to manually calculate molality or verify our molality calculator results:
Basic Molality Calculation
- Determine the mass of the solute in grams
- Find the molar mass of the solute (g/mol)
- Calculate moles of solute: mass / molar mass
- Measure the mass of the solvent in kilograms
- Divide moles of solute by kilograms of solvent
Example Calculation
Let’s calculate the molality of a solution containing 58.5g of NaCl in 2kg of water:
1. Molar mass of NaCl = 58.44 g/mol
2. Moles of NaCl = 58.5g / 58.44 g/mol = 1.001 moles
3. Mass of solvent = 2kg
4. Molality = 1.001 moles / 2kg = 0.5005 m
Converting Molarity to Molality
To convert from molarity to molality, you need the density of the solution:
- Determine the molarity (M) of the solution
- Find the density of the solution (g/mL)
- Calculate the mass of 1L of solution: density × 1000
- Calculate mass of solute in 1L: M × molar mass of solute
- Calculate mass of solvent: mass of solution – mass of solute
- Convert solvent mass to kilograms
- Molality = M / (kilograms of solvent)
