A sample of natural gas is 85.2% methane, CH4, and 14.8% ethane, C2H6, by mass. What is the density of this gas mixture at 18.0°C and 771 mmHg? Assume ideal gas behavior.

Answer 1

I would calculate an "average" molar mass.
Take a 1 g sample you will have 0.852g CH4 and 0.148 g C2H6.
(0.852 x molar mass CH4) + (0.148 x molar mass C2H6) = molar mass of the mixture.
Then P*molar mass = dRT
d = density in g/L.

Answer 2

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