Question

A closed tank having a volume of is filled with 0.30 lb of a gas. A pressure gage attached to the tank reads 12 psi when the gas temperature is There is some question as to whether the gas in the tank is oxygen or helium. Which do you think it is? Explain how you arrived at your answer.

Answer 1

Question:

A closed tank having a volume of 2 ft3 is filled with 0.30 lb of a gas. A pressure gage attached to the tank reads 12 psi when the gas temperature is 80 degree F. There is some question as to whether the gas in the tank is oxygen or helium. Which do you think it is? Explain how you arrived at your answer.

Answer:

The gas in the tank is oxygen

Explanation:

Here we mass of gas = 0.30 lb =‪ 0.136078 kg = 136.078 g

Volume of gas = 2 ft³ = ‪0.0566337 m³

Pressure reading of tank = 12 psi = ‪82737.08 Pa

Absolute pressure = Atmospheric pressure + Gauge pressure = ‪101325‬ + 82737.08 = ‭184062.08 Pa

Temperature = 80 ° F = ‪299.8167 K

Therefore, from the universal gas equation, we have

$n = \frac{P \cdot V}{R \cdot T} = \frac{184062.08 \times 0.0566337 }{8.3145 \times 299.8167 } = 4.1816 \ moles$

Therefore, since ‭4.181646 moles of the gas weighs 0.136078 kg, the molar mass of the gas is

0.136078/4.181646 = 0.03254 kg/mol = 32.54 g/mol

Therefore, since the molar mass of helium gas is 4.003 g/mol

and the molar mass of oxygen gas = 31.999 g/mol

The gas in the tank is likely to be oxygen.