Question

Determine the composition in mole fraction of the following gas.

Component	Composition Weight Fraction	Molecular Weight	Mole Fraction
Methane	0.880	16.04	?
Ethane	0.043	30.07	?
Propane	0.042	44.10	?
n-Butane	0.035	58.12	?

Answer 1

Let total weight of the mixture of all 4 gases be 100 gram.

We can have formula,

Composite weight fraction = (wt. of. a component/ Total wt. of mixture),

Hence, Wt. of a component = Composite wt. fraction x total wt. of mixture,

Therefore, Wt. of. Methane = 0.880 x 100 = 88 g.

Wt. of Ethane = 0.043 x 100 = 4.3 g.

Wt. of Propane = 0.042 x 100 = 4.2 g.

Wt. of n-Butane = 0.035 x 100 = 3.5 g.

Now let’s calculate no. of moles of each component gas.

Formula, No. of mole = Wt. of gas / mol. Wt. hence,

No. of moles of Methane = 88 /16.04 = 5.4862

Of Ethane = 4.3 /30.07 =0.1430

Of Propane = 4.2 /44.10 =0.0952

Of n-Butane = 3.5 /58.12 = 0.0602

Now, total no. of moles = 5.4862 + 0.1430 + 0.0952 + 0.0602 = 5.7846

Mole fraction of a gas = No. of mole of gas / total no. of moles,

So, Mole fraction of Methane = 5.4862 /5.7846 =0.9484

Mole fraction of Ethane = 0.1430 / 5.7846 =0.0247

Mole fraction of Propane = 0.0952 / 5.7846 = 0.0165

Mole fraction of n-Butane = 0.0602 / 5.7846 = 0.0104.