Mole Fraction Formula – Equation and Problem Solved with Example

At the molecular level, a solution is the homogeneous mixture of two or more substances. The ingredients of a mixture that are available in limited quantity is the solute and the one available in bulk quantity is called the solvent. Take an example, where a little quantity of sugar or solute is mixed along water or solvent then a homogeneous mixture could be produced. In this case, the solute will disperse uniformly in the water solvent.

Let us understand the concept better in terms of concentration. There are a plenty of techniques available to calculate the concentration of a solution. The most common technique is finding the total number of moles of solute dissolved. If there is one solution having very low in concentration then it is called as the dilute solution and a solution with higher energy or concentration is called as the concentrated solution.

The different techniques calculating concentrations are molarity, molality, normality, mole fraction, or percent by weight etc. Each solution has two common substances. These are either solute or solvent. When solute and solvent are mixed together, it will make a solution. Here, comes the term mole fraction that is defined as the ratio of number of moles of solute and total number of moles in solvent. The mole fraction formula in Chemistry is given as below.

Mole Fraction Formula

\[\ X_{solute} =\frac{Mole\;of\;Solute}{Mole\;of\;Solute\;+\;Mole\;of\;Solvent}\]

If n represents moles of the solute and N represents moles of the solvent,

Mole fraction formula/equation:

\[\ X_{solute} =\frac{n}{n\;+\;N}\]

The mole fraction of the solvent, then would be:

\[\ X_{solvent} =\frac{N}{n\;+\;N}\]

There is no unit defined for the mole fraction and the sum of the mole fractions of solute and solvent would be unity as given below;

\[\ X_{solute} + X_{solvent}=\;1 \]