Questions tagged [ideal-gas]
A gas that behaves as randomly moving, non-interacting molecules. This allows a simplified equation of state.
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Super pressure balloon but it vents over pressure
There is one substance better than hydrogen for acquiring lift, namely not filling your balloon with anything. After all, the hydrogen is just there as filler, so the walls of your balloon don't cave ...
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146 views
What controls the room pressure?
The following question is here Bidon, Energy of room. Ideal gas law : URL (version: 2018-10-27)
Although my question is a little bit different.
I’m currently studying Thermal Physics and I am ...
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584 views
Why doesn't Helium behave as an ideal gas?
I am a bit confused (might be due to some conceptual misunderstanding) as to why doesn't Helium behave as an ideal gas (it shows a deviation from the $pV$ vs $p$ graph)? (Given the fact that it is ...
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Why can't the molecules of an ideal gas have the same speed?
This question arises from two statements about the kinetic theory of gases in the Indian NCERT chemistry textbook, chapter 5, p. 148.
These are (emphasis by me):
Collisions of gas molecules are ...
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Is free expansion adiabatic
In free expansion the system is thermally isolated so $\Delta Q = 0$ throughout the process. This implies that process is adiabatic and follows its equation:
$$P_1V_1^\gamma = P_2 V_2^\gamma$$
But ...
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How much power is needed to keep ideal gas in a fix volume?
I was playing with the idea of entropy and an interesting thought came out. Imagine a physical cube with side $a$. Inside the cube is $N$ particles of an ideal gas at a temperature $T$. One particle ...
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1answer
12 views
Scattering cross-section of a nano-particle with background gas in high vacuum
Let's say I have a Silica nano-particle trapped with an optical tweezer in high vacuum (pressure ~ $10^{-6} \mathrm{mbar}$). I know the molar mass of the background gas and its temperature.
How would ...
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36 views
does this result require constant ambient density?
I'm posting from my phone, so I can't make this very snazy. My question pertains to the equation following "The derivative of density may in turn be eliminated by using the mass conservation ...
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1answer
120 views
Deriving the pressure exerted by classical particles on the walls of a cubical container (Ideal Gas)
Given that the probability to find a particle in a state $|i\rangle$ is
$$
p_i \propto \exp(-\beta E_i)
$$
one can conclude that for classical particles (:=particles obeying the classical kinetic ...
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842 views
Boyle's law question
X and Y are two gas bottles that are connected by a tube that has negligible volume compared with the volume of each bottle. Initially the valve W is closed. X has a volume 2V and contains hydrogen at ...
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1answer
35 views
Mean value with respect to maxwell's velocity distribution
I don't understand why for an arbitrary $A$, the integral
$$ \int \text{d}^3v \;f(\vec{v})A(\vec{v}) $$
is the mean value $\langle A\rangle_f$ of $A$ with respect to Maxwell's velocity distribution. ...
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494 views
In adiabatic expansion does the internal energy of an ideal gas decrease?
By First Law of thermodynamic, for an ideal gas, if there isn’t heat transfer, work done by the gas is equal to decrease in internal energy of the gas.
Suppose that I have a perfectly-insulated ...
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Why there is no upper limit for speed in Maxwell's speed distribution curve?
There is a lower limit for speed in Maxwell's speed distribution curve I.e. 0 but it doesn't has upper bound.It seems that the molecules of an ideal gas can move with infinite speed.Is it really ...
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183 views
Why does the mean speed of gas particles include $\pi$?
In chemistry we are learning about kinetic molecular theory (KMT) of gasses, and I just couldn't help being surprised when I saw $\pi$ in the equation of mean speed. I know that whenever $\pi$ is ...
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3answers
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Is internal energy a function of pressure?
I read that internal energy is a function of temperature only and not pressure. But say, we compress a volume of gas. Won't the particles start moving more quickly? Meaning an increase in their ...
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214 views
II law of thermodynamics & polytropic process
The polytropic process is defined as such that $pV^m=A$, where $A$ is a constant. Generally, the change in entropy is
$$\Delta S=nR \ln \frac{V}{V_0}+nC_V\ln \frac{T}{T_0}.$$
Using $pV=nRT$ and $pV^m=...
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Gas Transport Problem
I have a question that I thought would be a very simple effusion calculation that sent me down a massive rabbit hole after I tried to look it up in Landau's Physical Kinetics and so now I'm coming to ...
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201 views
The force exerted by a single molecule
In the chapter of the kinetic theory of gases in a basics undergraduate physics book, it says the force exerted by a single molecule on a wall is calculated as $F = \frac{\Delta p}{\Delta t} = \frac{...
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What would be the distances between compressors part of a gas pipeline from Earth to the Moon?
This paper, acquired from this question about tethers on the Moon, describes LADDER, a mission to deploy a Lunar Space Elevator [LSE].
The space tether, made of Zylon fiber, would be 264,000 km long, ...
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36 views
Is it possible for temperature to cause a change in the density of air in a closed isochoric system?
I am taking a meteorology chair as part of a airline transport pilot course and while discussing atmospheric pressure and density the professor claimed that an increase in the temperature of the air ...
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How to get equations of state by differentiating a thermodynamic potential?
For an ideal gas in a closed system, the thermodynamic potential U, the internal energy, is given by
$$ U(V,S) = U_0 \left( \frac{V_0}{V} \right)^{2/3} \text{e}^{\frac{S-S_0}{C_V}},\quad C_V = \frac{...
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Does the entropy of a real gas increase or decrease as compared to the entropy of ideal gas when the gas compartment is expanded so $V_f > V_i$
so i know the derived equation for change in entropy of a real gas but im struggling to understand how to compare that to the change in entropy for an ideal gas to answer the above question
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Re: Charles' Law: Is there a real world or laboratory example of an increase in volume under constant pressure CAUSING an increase in temperature?
Re: Charles' Law:
V/T = Constant, i.e., V and T are directly proportional; that is, assuming a constant pressure and amount of an 'ideal' gas.
It is easy to understand that the volume of a gas ...
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2answers
579 views
Gibbs theorem and partial molar volume
In the above, it's mentioned that any quantity other than MOLAR VOLUME can be written that way.
But how can we say generalize it with certainty when molar volume itself doesn't fit in or to say any ...
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2answers
214 views
Deriving simple equation for volume and pressure, adiabatic exponent
I have
$$VT^\frac{f}{2}=\text{constant}\tag1$$
and
$$V^{\gamma}P=\text{constant}.\tag2$$
Where $V=\text{volume}, \ P=\text{pressure} , \ T=\text{temperature},$
$f=\text{number ...
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1answer
546 views
Potential energy of an ideal gas
According to equipartition theorem, for ideal gas in thermal equilibrium, each vibrational mode will get $kT/2$ for kinetic energy and $kT/2$ for potential energy.
But at the same time, we assume ...
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1answer
131 views
Converting Gas volume to Liquid Volume
For a test setup, I need to set CO2 flowrate as 130 L/h but I do not have a flow measuring device to set it. So I made one device as mentioned below.
Once I set the flowrate, I will remove containers/...
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93 views
Internal energy of ideal gas in terms of sound speed and pressure
In thermodynamics two state variables can be treated as independent and any other variable can be determined from these two variables. We can assume sound speed and pressure as independent variables ...
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1answer
55 views
Particle in kinetic gas theory without collision
Hello I have a (Gedankenexperiment) question about the kinetic gas theory. As far as I understand temperature corresponds to kinetic energy. Assume now there would be one particle that does not ...
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Is there a word for the availability of a gas, normalized for pressure?
As a bit of background of what I'm getting at, consider that for the purposes of humans breathing and getting oxygen into their blood, 20% oxygen at 1 atm is equivalent to 100% oxygen at .2 atm. ...
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Is internal energy frame-dependent? [duplicate]
In the realm of kinetic theory of gases, the internal energy of gas is solely due to the sum of kinetic energies of all particles, since kinetic energy is frame dependent I was thinking whether a ...
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389 views
(SOLVED) Calculate the velocity of a gas inputted in pressure difference
I'm trying to make a generally simple calculation but I'm not sure if I'm approaching this correctly. So as I'm making assumptions solving this problem, please comment or correct me wherever I'm wrong ...
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2answers
122 views
On internal energy conservation in a gas system
I have seen multiple questions which talk about a tank with a partition in the middle and different ideal gases on either side at some different value of pressure,volume and temperature and then they ...
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What happens when ideal gasses are mixed?
I'm sure their temperatures will be equal, but what about their volumes and pressures?How does one approach ideal gas mixing problems?
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What does $C_p-C_v=R$ mean? What are its applications?
So my question is: what does $C_p-C_v=R$ actually mean? It's very straightforward to derive. But my issue is, where and what use does this have in real life applications, and why is it important?
All ...
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530 views
What happens to the pressure and the temperature of a gas compressed adiabatically?
The set-up is basic. There is a piston that goes down, reducing the volume. The process is adiabatic, so the acquired energy is kept inside the gas. The ideal gas law states that as the volume ...
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Is it possible to calculate pressure without a barometer?
For an experiment, I need to pump air into a rocket with varying volumes of water, and thus air. However, I want to keep the pressure the same. Given the amount of air a bicycle pump can pump, the ...
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667 views
Pressure in a 2D Ideal Gas simulation
I am currently creating a 2D ideal gas simulator whereby the user can determine three of the four variables (P, V, n, T) and the gas would adjust accordingly.
I was wondering how I could calculate ...
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Expansion of an ideal gas in an evacuated bottle having nonconducting walls
In the free expansion of ideal gas in a vacuum $dW = 0$ as $p_{ext} = 0$ and $dU = 0$ therefore there is no change in temperature of the ideal gas also. what i want to know that can the following ...
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Finding the temperature of a gas using the $P$-$V$ diagram [closed]
I need to know a way to relate the P-V curve of an ideal gas to its temperature.I found a similar question on stackexchange but couldn't understand how the relationship between a point and the ...
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1answer
531 views
Find the density of air at the given temperature and pressure [closed]
Find the density of air at $99$ kPa and $322.15$ K.
My attempt:
Let's assume that air is $78\%$ nitrogen and $22\%$ oxygen by volume.
Average molar mass of air = $0.78\times 28+0.22\times 32\approx ...
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How do I calculate the pressure on the walls of my MD simulation?
So I've built a simulation in vpython where I have multiple hard balls that collide with each other and with the walls of the cube I've placed them in. I then replaced the values for their radius and ...
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Confused about summing over the velocity squared term
Consider a cubical box, L on each side. The box contains N molecules of ideal gas, each of mass m.
All collisions are elastic. The force exerted by one molecule when it collides with a wall of ...
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29 views
Why maxwells speed distribution law doesn’t violet special theory if relativity [duplicate]
As per maxwells distribution law the molecule of gas will have speed across zero to infinity with some probability function. I want to know that why the speed above speed of light is possible (i know ...
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Ideal gas law when diatomic molecule is about to break into constituents
Suppose we have a diatomic molecule. Its center of mass has an average kinetic energy given by
$$
\frac{1}{2} (m_1 +m_2) v_{cm}^2 = \frac{3}{2}k_BT
$$
and using this we can derive the ideal gas law
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What is the volume occupied?
What is the volume occupied by 1 mole of gas at $10^{−10}$ torr, the pressure inside an “ultra high vacuum” (UHV) chamber.
How do I solve this problem without being given the temperature?
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224 views
How do I simulate an ideal gas?
I wish to write a simple simulation of an ideal gas, but my maths and how I should have a model based the equation isn't quite up to it. I need some help understanding the relationship between ...
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1answer
76 views
Work done by ideal gas under a reversible process which is not isobaric, isochoric, isothermal, adiabatic
First post, sorry for the poor formatting.
Question
Consider a non adiabatic system closed to mass exchange where an ideal gas traverses along a reversible path from state: to . What is the work ...
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3answers
373 views
Infinite entropy in ideal gas
Does it make sense that entropy goes to infinity as temperature goes to infinity?
For an ideal monoatomic 1D gas I have an expression for entropy
\begin{equation}
S=Nk_{B}Ln(\frac{Ve^{\frac{5}{2}}\...
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2answers
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Would setting the ideal gas constant to $1$ yield an attractive natural temperature scale? [closed]
In this recent question, there was a comment 'The "zero point" of Kelvin is natural, but the scale is not'. This led me to wonder whether setting $R = 1$ in the ideal gas law would be an attractive ...
