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Mole Fraction

Mole Fraction

Author: Jose Popoff

Express the concentration of a solution in terms of mole fraction.

The concentration of a solution can also be expressed in terms of the amount of moles of solute and solvent present.  The concept of mole fraction is a rather simple one that expresses the ratio of either the solute or the solvent to the other components of the solution.



X = mole fraction

n = number of moles


For instance, a solution composed of three moles of water and one mole of methanol (CH3OH) contains the following mole fraction of water:

If we were to compute the mole fraction methanol, we would get 


Notice that the sum of both mole fractions is equal to 1.


Please take a look at the following video examples:

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Mole Fraction Example 1

Mole Fraction Example 2