Molality

The Molality calculator computes the concentration of a solution based on the moles of solute and the mass of the solvent.

INSTRUCTIONS: Choose units and enter the following:

• (MSt)  Moles of Solute
• (MSv)  Mass of Solvent

Molality (MT): The calculator returns the molality in moles per kilogram.

The Math / Science

The molality equation is similar to the most commonly used concentration measures, molarity and percent by mass, but can be useful when discussing many physical properties of solutions. The molality equation is:

 
          `MT = MSt / MSv`

 where:

• MT = Molality
• MSt =  Moles of solute, moles of the substance being dissolved
• MSv = Mass of solvent, the kilograms of the substance that dissolved the solute (the solvent is usually water)

Supplemental Material

Khan Academy: Molarity vs. Molality

Related Topics

• For Spanish site click here (Molalidad)

References

Whitten, et al. "Chemistry" 10th Edition. Pp. 516