Top

# Mole Fraction Formula

Mole fraction is the amount of moles of particular component in the mixture to the total number of moles of all the components in the mixture. The symbol for mole fraction is X with the component being studied written as subscript.

Mole Fraction Formula of solute is

Mole fraction of solvent is

Sum of mole fractions are always unity.

Mole fraction has no units.

 Related Calculators Mole Fraction Calculator conversion of grams to moles calculator convert moles to grams calculator

## Mole Fraction Problems

Example problems are given below based on mole fraction concept.

### Solved Examples

Question 1: A gaseous solution contains 3.5 $\times$ 10-3 moles of N2 and 1.5 $\times$ 10-3 moles of CO2. What is the mole fraction of each component present?
Solution:

Moles of N2 = 3.5 $\times$ 10-3
Moles of CO2 = 1.5 $\times$ 10-3

Total number of moles = 3.5 $\times$ 10-3 + 1.5 $\times$ 10-3
Total number of moles = 5 $\times$ 10-3

Mole fraction of N2 = $\frac{3.5 \times 10^{-3}}{5 \times 10^{-3}}$ = 0.7

Mole fraction of CO2 = $\frac{1.5 \times 10^{-3}}{5 \times 10^{-3}}$ = 0.3

Question 2: What is the mole fraction of CH3OH in an aqueous solution which is simultaneously 3.5m C2H5OH and 2m CH3OH?
Solution:

3.5 m C2H5OH means 3.5 moles of C2H5OH in 1 kg water 2m CH3OH means 2 moles of CH3OH in 1 kg water. In 1 Kg of H2O we have

$\frac{1000\ gm}{18.016\ gm\ mole}$ = 55.5 moles of H2O

Total moles in the solution = 3.5 + 2 + 55.5

Total moles in the solution = 61 moles

Mole fraction of CH3OH = $\frac{2\ moles}{61\ moles}$ = 0.0328

*AP and SAT are registered trademarks of the College Board.