Asample of liquefied natural, lng, from alaska has the following molar composition: 3.9% c2h6, 1.1% c3h8, 1.1% co2, and the rest ch4. determine (a) the average molecular weight of the lng mixture. (b) the weight fraction of ch4 in the mixture. (c) the lng is heated to 422 k and 148 kpa, and vaporizes completely. estimate the density of the gas mixture under these conditions.

a) 17,20

b) 87,57%

c) 0,7259

Explanation:

a) With molar composition of LNG the average molecular weight is:

3,9%×30,07 + 1,1%×44,1 +1,1%×44,01 + 93,9%×16,04 = 17,20

b) The weight fraction of CH₄ is:

×100 = 87,57%

c) It is possible to use ideal gas law thus:

= δ

Where:

P is pressure: 148 kPa

MW is molecular weight: 17,20

R is gas constant: 8,31

T is temperature: 422K.

And δ is density. Replacing you will obtain:

δ = 0,7258

I hope it helps!