Question

55 kg of liquefied natural gas (lng) are stored in a rigid, sealed 0.17 m3 vessel. in this problem, model lng as 100% methane. due to a failure in the cooling/insulation system, the temperature increases to 200 k, which is above the critical temperature; thus, the natural gas will no longer be in the liquid phase.

Answer 1

I am assuming that the problem ask for the pressure in the system. To be able to calculate this, we first assume that the system acts like an ideal gas, then we can use the ideal gas equation to find for pressure P.

P V = n R T

where,

P = Pressure (unknown)

V = 0.17 m^3

n = moles of lng / methane

R = gas constant = 8.314 Pa m^3 / mol K

T = 200 K

We find for the moles of lng. Molar mass of methane = 16 kg / kmol

n = 55 kg / 16 kg / kmol

n = 3.44 kmol CH4 = 3440 mol

 

Substituting all the values to the ideal gas equation:

P = 3440 mol * (8.314 Pa m^3 / mol K) * 200 K / 0.17 m^3

P = 33,647,247 Pa

P = 33.6 MPa