# Questions tagged [kinetic-theory-of-gases]

Questions about the assumptions, equations, and properties of gases derived from kinetic theory. For questions pertaining to rates of reactions, please use the kinetics tag instead.

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### Why don't gases escape Earth's atmosphere?

Some gases are lighter than others and rise. Why don't they continue going up, leave the atmosphere, and then enter outer space?
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### Does the Maxwell-Boltzmann distribution apply to gases only?

The Maxwell-Boltzmann distribution can be used to determine the fraction of particles with sufficient energy to react. I know that the curve applies to gaseous reactants and would like to know whether ...
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### Does gravity affect the trajectory of gas particles?

We're studying the kinetic theory of gases in school, and one of the points that was brought up was that: "Gases consist of particles in constant, random motion." How is it possible for gas particles ...
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### Reason for negative Joule Thomson coefficient of Helium and Hydrogen at NTP conditions

Recently, while reading my textbook I came to know that Helium, Hydrogen and Neon are the only gases which have negative Joule Thomson coefficient at NTP conditions, i.e heating effect is observed ...
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### Why does gas particle velocity affect rate of effusion?

I understand why smaller particles have more velocity, but I don't understand what velocity has to do with the rate of effusion: My reasoning is thus: Pressure is the number of impacts of particles ...
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### Derivation of mean speed from Maxwell–Boltzmann distribution

I found that if a velocity of a gas follows the Maxwell–Boltzmann distribution, the mean velocity is given by $$\langle v \rangle = \sqrt{\frac{8RT}{\pi M}}$$ where $R$ is the gas constant, $T$ is ...
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### Is air made 100% from atoms?

I know air is made up of roughly 78% nitrogen, 20% oxygen, etc.. but I would like to know what percentage of air is just space and has no atoms at all.
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### Derivation of mean kinetic energy

I read from a book that average kinetic energy is equal to $3kT/2$ where $k$ is Boltzmann's constant and $T$ is the kelvin temperature. I don't know how the formula was derived. Any help to gain ...
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### Equalization of pressure in heat exchanger

I was solving numericals on Kinetic Theory of Gases when I came across this question Two closed vessel of equal volume contain air at 105 kPa, 300 K and are connected through narrow tube. If one of ... 119 views

### How was it possible to accurately measure the mass of gases in the 19th century?

I have seen periodic tables of Mendeleev (1834-1907) and Newland (1837-1898) in which masses of gases such as oxygen and nitrogen were shown. I don't think there were instruments to measure mass of ...
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### What is the relation between absolute temperature, and rates of diffusion and effusion of a gas?

According to Graham's diffusion law, rate of diffusion is directly proportional to square root of temperature but rate of effusion is inversely proportional to square root of temperature. Why is this ...
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### Can someone walk me through this gas mixture question?

Argon $(\ce{Ar})$ and helium $(\ce{He})$ are initially in separate compartments of a container at $\pu{25 °C}.$ The $\ce{Ar}$ in compartment A which has a volume $V_\ce{A}$ of $\pu{9.00 L}$ and a ...
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### Question regarding $Z$ (Compressibility factor)

Oh! This problem has been bugging me for a long time. According to Wikipedia, the Compressibility factor $Z$ is defined as the ratio of the volume occupied by a real gas to the volume occupied by an ...
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### Compressibility factor (Z) of a real gas [closed]

I was wondering whether the compressibility factor of a real gas (given by $Z = V_{\mathrm{real}}/V_{\mathrm{ideal}}$) is supposed to be measured while keeping pressure constant? I was attempting to ...
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### The distance that CO2 molecules travel in the air before they collide with each other

Well the title covers most. But further at 410 ppm, 1 atm and 23 °C. I believe they call it the mean free path of CO2-CO2 collisions. So not just the mean free path of CO2 in air colliding with every ...
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### Temperature in the Maxwell-Boltzmann Distribution

I am attempting to generate the probability for the specific speed of a molecule using the Maxwell-Boltzmann distribution, but I cannot decide on which temperature I should use in the equation. For ...
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### Speed distribution of lighter vs heavier gases

I cannot understand why the range of molecular speed is not always wider for a lighter gas as compared to a heavier gas . If the same energy is supplied to both gases then wouldn't the molecular ...
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### How to calculate the final temperature of a gas when it undergoes adiabatic expansion?

The question is as follows: A sample of $\pu{4.0 moles}$ of a gas ($C_{v,m} = \pu{21 J mol-1 K-1}$) has an initial pressure of $\pu{304.4 kPa}$ and an initial volume of $\pu{20 dm3}$ at $\pu{270 K}$... 465 views

### What happens when a super-critical fluid is compressed?

Suppose that I have some substance with a critical temperature of 20°C. That means above that temperature, the substance exists neither as a gas nor a liquid, but instead as a super-critical fluid. ...
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The ratio of the heat capacities $\frac{C_\mathrm p}{C_\mathrm v}$ for one mole of a gas is $1.67$. The gas is: a) $\ce{He}$ b) $\ce{H2}$ c) $\ce{CO2}$ d) $\ce{CH4}$ I know how to answer ...
I have having difficulty in understanding the liquefaction of gases.In the graph of isotherms of $\ce{CO2}$ I cannot understand how can gas coexist as liquid and vapour under area of $\mathrm{XCEBY}$....