Molality Calculator

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Molality of a solution is the ratio of number of moles of solute to the weight of solvent in kg. It is denoted by the symbol b or m. It is independent of temperature and pressure. Molality is different from molarity. Molality depends on mass of solvent where as molarity depends on volume of the solution.

Example 1: Find the molality of a solution prepared by dissolving 0.15 moles of with 555 gm of water at 75º C.

Here number of moles of = 0. 15

Mass of water or solvent = 555 gm

Here the temperature is 75º. But Molality does not depend on temperature.

1000gm is equal to 1 kg then 555gm is equal to 0.555 kg

Molality = = = 0.27 m.


Example 2: A sample contains 88gm of ethanol and 200gm of water at 26º C. Find the molality of the concentration.

Given, 88 gm of Ethanol

Number of moles of Ethanol = = 2.05 moles

Mass of water or solvent = 200gm.

Converting gm into kg. 1000gm is equal to 1 kg.

So 200gm is equal to 0.200 kg.

Molality = = = 10.25 m

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