Molality/Molarity - The difference
Molality - number of moles of solute dissolved in one kilogram of solvent. Molality is different from molarity because molality is about concentration in kilograms of solvent and molarity is about concentration in dm3 (liters) of solvent. Molality is represented by a small 'm', whereas molarity is represented by an upper case 'M'.
Molality and Solvents
Water as a solvent: Since water has a specific gravity of 1 (one dm3 = 1kg) , a molal concentration of 1m can be made by adding water to a volumetric flask up to the one liter line and then add the solute.
Other solvents are usually lighter than water and must therefore be weighed before adding the solute.
To make a one molal aqueous solution of potassium chloride,
measure
out one kilogram of water and add one mole of KCl (74.55g/mole) to it.
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