# Application of the ideal gas law

• I

## Main Question or Discussion Point

Hi,

I want to calculate the amount of liquid nitrogen (at boiling temp.) needed to build a pressure of 10.1 bar in a vessel of volume 66 m3. The liquid will be poured slowly into the vessel, boil off and fill the volume with gas at the specified pressure. I make the assumption that the process is isothermal (T = 300 K); is this a valid assumption? If so, the ideal gas law gives that the needed amount of N2 is n ≈ 27000 moles.

Given that the molar mass is m = 14.0067 g/mol, we get a total mass of M = 378 kg. The density of liquid nitrogen at boiling temp. is 0.808 kg/l, so this gives the needed amount 468 liters.

Is this reasonable, or are there any major flaws in the calculation?

Thanks

Related Classical Physics News on Phys.org
The assumption might be valid for a homework problem. It's hard (not impossible) to imagine a physical situation where there was sufficient heat to boil the LN2 and not also heat the gas. There is also a major flaw - check your molar mass.

Chestermiller
Mentor
Hi,

I want to calculate the amount of liquid nitrogen (at boiling temp.) needed to build a pressure of 10.1 bar in a vessel of volume 66 m3. The liquid will be poured slowly into the vessel, boil off and fill the volume with gas at the specified pressure. I make the assumption that the process is isothermal (T = 300 K); is this a valid assumption? If so, the ideal gas law gives that the needed amount of N2 is n ≈ 27000 moles.

Given that the molar mass is m = 14.0067 g/mol, we get a total mass of M = 378 kg. The density of liquid nitrogen at boiling temp. is 0.808 kg/l, so this gives the needed amount 468 liters.

Is this reasonable, or are there any major flaws in the calculation?

Thanks
Isn't the molar mass of N2 28 g/mole?