# 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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### Is Internal Energy = (3/2)nRT for a ideal monoatomic gas?

Internal Energy is a state variable and its value at a particular state cannot be measured; only the change in internal energy can be measured. So how come we write that $$U=\frac32nRT$$ where $U$ = ...
996 views

### Why do gases need to be cooled to liquefy/solidify?

My book states: Gases do not liquify on compression only, although molecules come close to each other and Weak forces operate at a maximum. Why is it that we cannot just keep on compressing gas ...
7k views

### 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 ...
4k views

### 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?
5k views

### 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 ...
1k views

### 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 rate of effusion: My reasoning is thus: Pressure is the number of impacts of particles in a ...
482 views

### Why is the rate inversely proportional to the square root of temperature in Grahams Law of Diffusion?

In my book it is given that: The general form of the Grahams Law of Diffusion can be stated as follows when one or all of the parameters are varied: $$\text{rate} \propto \frac{PA}{\sqrt{TM}},$$ ...
21k views

### 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 ...
3k views

### Kinetic energy of molecules in liquid state?

My book (book link) has this question: The kinetic energy of molecules at constant temperature in gaseous state is: more than those in the liquid state less than those in the liquid ...
43k views

### 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 $\pu{270 K}$...
382 views

### Volume of gas in containers

If gases occupy all the volume in a container then how can we define 'volume percent' as all different gases will have same volume?
326 views

### Why is the speed of ideal gases mass dependent while the kinetic energy is not?

The rms speed of an ideal gas is $v_{\text{rms}}$ = $\sqrt{\frac{3RT}{M} }$ and the kinetic energy is $E_\text{k} = \frac32RT$. From this, it is concluded that the speed is mass dependent, while the ...
676 views

### Is oxygen above the critical point always supercritical fluid? Would it still appear to roughly follow the ideal gas law?

In this answer I've asserted (without a "Chemist's license") that as long as oxygen is above it's critical point in both temperature (154.5 K) and pressure (50.4 bar) it's going to be a supercritical ...
2k views

### How to interpret the Maxwell-Boltzmann distribution to find the activation energy?

I understand activation energy to be the relative difference in energy between that of the activated complex/transition state (at some temperature) and the average energy of the reactants like shown ...
In the general equation of the compressibility factor $Z$, we define $Z$ as $$Z=\frac{pV}{nRT}$$ Here, what is $p$? Is it $p_\text{real}$ or $p_\text{ideal}$? Also, what is $V$? $V_\text{real}$ or $V_\... 0answers 73 views ### Estimating Surface Reactions - Liquid, Turbulent Flow So, I need a method of estimating the influence of a surface (rate constant would do for a start), the idea is to estimate just Reactant + Surface -> Product in a turbulent liquid flow. Now I am ... 2answers 438 views ### How to get the first step of the derivation of the Maxwell-Boltzmann distribution To derive the Maxwell-Boltzmann distribution the first step requires the knowledge that the equation will take the form $$f(v)=Ke^{-\epsilon/ kT}$$ where$\epsilon$is the sum of the kinetic energies ... 1answer 535 views ### Interpreting straight lines in a graph of isotherms of carbon dioxide I am having difficulty in understanding pressure-volume graphs of$\ce{CO2}$at different temperatures which describes liquefaction of$\ce{CO2}$. I know that at the critical temperature of$\pu{31.1^...
$(P + an^2/V^2)(V - nb) = nRT$ I understand that the term $nb$ is subtracted from the volume term as the available volume for the gas molecules to move around decreases in the case of a real gas ...