Molality Calculator
Standard pharmaceutical calculation, laboratory analysis and research tools.
Calculate molality, moles or solvent mass using the standard relationship between the amount of solute and kilograms of solvent.
What Is Molality?
Molality is the number of moles of solute present per kilogram of solvent. It is expressed as mol/kg and differs from molarity because it uses solvent mass rather than solution volume.
Molality Formula
The basic formula is m = n/W, where m is molality, n is moles of solute and W is the mass of solvent in kilograms.
How to Calculate Molality
Enter the known amount of solute and mass of solvent, select the relevant units and calculate the unknown quantity. Convert solvent mass to kilograms when necessary.
Molarity vs Molality
Molarity is based on litres of solution, while molality is based on kilograms of solvent. Because solvent mass does not change with temperature in the same way as solution volume, molality is useful in studies involving colligative properties.
Pharmaceutical Applications
Molality calculations are useful in pharmaceutical chemistry, physical pharmacy and laboratory studies involving solution properties and concentration relationships.
Frequently Asked Questions
What is the formula for molality?
Molality equals moles of solute divided by kilograms of solvent.
What is the unit of molality?
The standard unit is mol/kg, often written simply as m.
Is molality based on solution volume?
No. Molality is based on the mass of solvent, not the volume of the final solution.