Mole Fraction Formula
What is Mole fraction?
Mole fraction represents the number of molecules of a particular component in a mixture divided by the total number of moles in the given mixture. It’s a way of expressing the concentration of a solution.
The molar fraction can be represented by X. If the solution consists of components A and B, then the mole fraction is,
Therefore, the sum of mole fraction of all the components is always equal to one.
Please note that mole fraction represents a fraction of molecules, and since different molecules have different masses, the mole fraction is different from the mass fraction.
A tank is charged with a mixture of 1.0 x 103 mol of oxygen and 4.5 x 103 mol of helium. Calculate the mole fraction of each gas in the mixture.
The given parameters are
NHe = 4.5 x 103 mol and nO2 = 1.0 x 103 mol
Mole fraction can be calculated as
XHe = 4.5 x 103 mol / 4.5 x 103 mol + 1.0 x 103 mol
4.5 mol / 5.5 mol
XO2 = 2.0 x 103 mol / 4.5 x 103 mol + 1.0 x 103 mol
= 1.0 x 103 / 5.5 x 103
Determine the mole fraction of methanol CH3OH and water in a solution prepared by dissolving 4.5 g of alcohol in 40 g of H2O. M of H2O is 18 and M of CH3OH is 32.
Moles of CH3OH = 4.5 / 32 = 0.14 mole
Moles of H2O = 40 / 18 = 2.2 moles
Therefore, according to the equation
mole fraction of CH3OH = 0.14 / 2.2 + 0.14
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