# Tag Info

Accepted

### Reason for negative Joule Thomson coefficient of Helium and Hydrogen at NTP conditions

Note: You can skip section I, and go straight to section II and/or the end of section III (specifically the conclusions subsection), if you are already familiar with the basic mathematical machinery/...
• 8,495
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### Is oxygen above the critical point always supercritical fluid? Would it still appear to roughly follow the ideal gas law?

Yes. Any fluid with a temperature is above critical temperature and the pressure above the critical pressure is by defintion a supercritical fluid. Don't be mislead by all the claims that ...
• 22k
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### According to KMT, is the velocity of an ideal gas always sqrt(3RT/M)?

$E=\frac 12mv^2 \implies v=\sqrt{\frac{2E}{m}}$ is valid for translational kinetic energy and the speed of the centre of mass. Vibrational or rotational energy does not count. An object may vibrate ...
• 43k
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### Does gravity affect the trajectory of gas particles?

Yes gravity pulls on gas molecules. That is why the atmosphere doesn't just float off into space. The gist is that the time between collisions is very short in the lower atmosphere, and the ...
• 22.3k
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### Kinetic energy of molecules in liquid state?

The average translational kinetic energy of a molecule is $3kT/2$ irrespective of whether the molecule is in the gas, liquid, or solid phase. In the liquid the motion giving rise to kinetic energy is ...
• 30.9k
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### Confusion in Van der Waals Equation

The van der Waals equation is represented as such: $$\left(P + \frac{an^2}{V^2}\right)(V-nb) = nRT$$ Here, $P$ is the pressure of the container and $V$ is indeed the volume of the container. All the ...
• 1,247
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### Is internal energy equal to (3/2)nRT for an ideal monoatomic gas?

Molecules have internal energy due to intermolecular interactions, as well as translational kinetic energy, rotational energy, vibrational energy, electronic energy (and if you care to include them, ...
• 40.9k
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### Does the Maxwell-Boltzmann distribution apply to gases only?

I'm going to go against the grain here: the Maxwell distribution does describe the distribution of molecule speeds in any (3-D) matter, regardless of phase. Suppose we have a system of $N$ molecules ...
• 1,269

### Is air made 100% from atoms?

One way to answer this is to compare nitrogen gas at standard pressure and temperature to liquid nitrogen at 1 atm. The density ratio is about 1500. In the liquid, space is nearly filled by the N2 ...
• 432
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### Derivation of mean kinetic energy

A simple validation The result you quoted is the average translational kinetic energy for an ideal gas. First, let's sketch out a rough derivation for the average kinetic energy of a particles of an ...
• 8,495
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• 7,260

### Does gravity affect the trajectory of gas particles?

To add to previous answers, all molecules and atoms are affected by gravity and so the density of the atmosphere is greater at the surface of the earth compared to higher up, which is why climbing on ...
• 30.9k

### Uranium enrichment via effusion through a porous membrane

The second approach looks more correct to me. The first approach is using raw percentages without converting to a ratio between isotopes, and the ratio rates is going to be directly related to the ...
• 17.5k
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• 41.1k
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### Degrees of freedom of a molecule of N atoms

Bonds in a molecule are flexible. Thus, each atom can move in any possible direction in 3D space. Note that they can't necessarily move any possible distance; indeed, if the molecule is stationary, ...
• 12.2k