Question

An aqueous solution is labeled as 0.25 m NaCl. What is the mole fraction of the solute in this solution?

Answer 1

The aqueous solution is 0.25 m (molality) and not 0.25 M (molarity). Molality m is defined as the number of moles of solute per kilogram of solvent.

molality = number of moles of solute (n) / kg of solvent

Molality is independent of temperature since it depends on mass. In very dilute aqueous solutions the molarity (M) and molality (m) are nearly the same.


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