Apparent Molecular Mass

Natural gas is usually a mixture of components, and its molecular mass can be described as Apparent molecular weight. This is defined as the sum of the products of the mole fractions of each component times the molecular weight of that component.

Component	Mole Percent ( % )	Molecular Mass (g/mol)	Fraction (g/mol)
C1	84	16.043	0.84 x 16.043 = 13.476
C2	6	30.070	0.06 x 30.070 = 1.8042
C3	3	44.100	0.03 x 44.100 = 1.3229
i-C4	4	58.12	0.04 x 58.120 = 2.3250
n-C4	3	58.12	0.03 x 58.120 = 1.7437
		Sum =	20.672

The final specific gravity of the gas, based on a molecular mass of 20.672 g/mol is:

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