High School

A tank contains [tex]$2 \, \text{m}^3$[/tex] of air at -93 ∘C and a gauge pressure of 1.4 MPa. Determine the mass of air in kg. The local atmospheric pressure is 1 atm.

Answer :

To determine the mass of air in the tank, we need to first find its absolute pressure and then use the Ideal Gas Law:

PV = nRT, where P is the absolute pressure, V is the volume, n is the number of moles, R is the universal gas constant, and T is the temperature in Kelvin.

First, let's convert the temperature to Kelvin: -93 + 273.15 = 180.15 K.

Next, we need to find the absolute pressure, which is the gage pressure plus the atmospheric pressure. In this case, the absolute pressure is 1.4 MPa + 1 atm = 2.4 MPa.

Now, we can plug in the values and solve for n:

2.4 MPa * 2 m^3 = n * 8.31 J/mol * 180.15 K

n = (2.4 MPa * 2 m^3) / (8.31 J/mol * 180.15 K)

Finally, we can use the molar mass of air (about 28.97 g/mol) to convert n to mass:

mass = n * molar mass = (2.4 MPa * 2 m^3) / (8.31 J/mol * 180.15 K) * 28.97 g/mol

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