Molality Calculator

The Molality Calculator computes molal concentration, defined as moles of solute per kilogram of solvent. Unlike molarity, molality does not depend on temperature because it uses solvent mass, not solution volume.

$$m = \frac{n_{\text{solute}}}{m_{\text{solvent}}}$$

where $m$ is molality in mol/kg, $n_{\text{solute}}$ is moles of solute, and $m_{\text{solvent}}$ is solvent mass in kilograms.

Example: dissolving 70.128 g of NaCl (molar mass 58.44 g/mol) in 1.5 kg of water gives 1.2 mol of solute and molality $m = 1.2 / 1.5 = 0.8$ mol/kg.

Frequently Asked Questions

What is molality?

Molality is the number of moles of solute per kilogram of solvent. Its SI unit is mol/kg, sometimes written as molal.

How is molality different from molarity?

Molarity uses solution volume in liters, while molality uses solvent mass in kilograms. Molality is temperature-independent; molarity changes when solution volume changes with temperature.

How do I calculate molality from mass?

First convert solute mass to moles by dividing by molar mass. Then divide moles by solvent mass in kilograms: m = (mass / molar mass) / kg solvent.

What is the molality if 3 moles dissolve in 0.5 kg solvent?

m = 3 / 0.5 = 6 mol/kg. Divide moles of solute by kilograms of solvent.

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Molality Calculator

Molality Calculator

Frequently Asked Questions

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