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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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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1answer
39 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
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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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1answer
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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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4answers
70 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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46 views
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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1answer
48 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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3answers
101 views
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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0answers
49 views
Reason for gas constant value
I know that it's derived from experimentation and it's natural but is there a specific reason that the value is $8.31\space J\space mol^{-1}\space K^{-1}\space$?
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1answer
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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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0answers
40 views
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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0answers
22 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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2answers
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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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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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Why is the probability that the collision angle will be in the range of 0 to 60 degrees than in the range of 60 to 180 degrees
Pretty much the title.
It is given that the probability that the collision angle will be in the range of 0 to 60 degrees than in the range of 60 to 180 degrees
I don't remember seeing such statement ...
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1answer
48 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
89 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 ...
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6answers
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Conversion of $R = 8317\ \mathrm{\frac{J}{kg\cdot mol\cdot K}} $ to $ 8317\ \mathrm{\frac{J}{kg\cdot mol\cdot {^\circ C}}}$
I'm trying to understand the unit conversions when one unit is obtained by shifting the value of another one by some constant. In particular, the unit conversions from Kelvin to Celsius scale:
$$T(\...
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1answer
81 views
Why doesn't the equipartition theorem force the rotational energy of a monoatomic molecule to be significant?
I'm reviewing the Feynman Lectures and in them he states that the rotational kinetic energy of a monoatomic molecule in a gas is insignificant due to a small moment of inertia.
But wouldn't the ...
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12 views
Transfer of gas particles during pressure change
There is a room with a known volume. The temperature and pressure are known too (STP). It is given that the window is open and there will be a pressure drop outside due to wind. I need to find the ...
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Collision frequency of ideal gas and velocities of molecule
Is collision frequency of gas molecule
$ = \frac{V_{RMS}}{\lambda}$
where $\lambda$ is mean free path.
Shouldn't it be $\frac{V_{average}}{\lambda}$?
(I often see that in theories books suggest that ...
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2answers
78 views
Thermodynamics problems with a cycle (insufficient data?)
I am having some troubles in solving the following problem a professor gave us, and in my opinion I think that either there are insufficient data or the solutions are infinite.
We have a perfect gas,...
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0answers
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Question about a hand-waving estimation done by Landau
I was reading the book written by Landau on statistical mechanics (Statistical Physics I 3rd Ed). In §1 there is a footnote that Landau wants to illustrate how accurate a statistical average can be ...
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2answers
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Does the ideal gas law apply to a moving vehicle?
If for example you have a car travelling along a road. There is obviously a high pressure region in front of the car, where the air is forced around the vehicle. Likewise, I understand that cars will ...
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21 views
How to calculate the actual pressure in chamber with reduced pressure but at increased temperature?
I would like to find out the actual pressure in a chamber (constant volume) where the pressure within is reduced to 1.5 kPa but with increased temperature to 65˚C. How to calculate this?
Assuming 0....
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1answer
68 views
Kinetic Molecular theory ideal gases, deriving the equation $PV = \frac{1}{3}mN C^2$
The problem I have with this proof is how to acquire the fraction $\frac{1}{3}$. In theory we were taught by taking into consideration a rectangular vessel which obviously has three paths which a ...
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1answer
77 views
Momentum average on phase space for free particle
I'm studying from Greiner statistical mechanics, and he uses an approximation which I don't really understand.
On averaging over many phase-space points we have
$$\langle\vec{p}^2\rangle=3\langle ...
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0answers
61 views
Entropy density (entropy per particle)
How I can get this definition for an ideal gas: $s=C v \ln (Pρ^{−\gamma})+ \text{constant} $ ?
In this answer it is mentioned that there is a connection with the Sackur-Tetrode relation of the ...
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0answers
62 views
Ideal gas equation vs Kinetic theory equation
From the ideal gas equation: $PV = NkT$, since Pressure times Volume = Energy, my understanding is that the total (internal) energy of $N$ molecules of a gas $= NkT$.
However from the kinetic theory ...
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1answer
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What is the PDF of relative collision speeds in an ideal gas?
In the Kinetic theory of gases, the speeds of particles follow a Maxwell-Boltzmann distribution.
However, what if one is interested in the distribution of relative collision speeds, aggregated over ...
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2answers
84 views
Do atoms in an ideal gas ever collide?
According to Wikipedia:
An ideal gas is a theoretical gas composed of many randomly moving point particles whose only interactions are perfectly elastic collisions. The ideal gas concept is useful ...
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1answer
237 views
Derive the kinetic gas equation [closed]
I need a proof of high school level
I have confusion in taking probabilities in all directions not yet concluded this, and I need a proof using momentum i.e I need a high school level proof
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3answers
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Why is $dE = C_V dT$ for an ideal gas, even when the process is not constant volume? [duplicate]
I have come across the following derivation for the "equation of an adiabat for an ideal gas" in many textbooks. The following steps are referenced from a separate question:
dE=dQ+dW
dW=−pdV
dQ=0
...
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3answers
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Thermodynamics : Pressure of a gas
While reading The kinetic Theory of gases in Feynman Lectures , i was hoping for an explanation concerning the factor (2) that shows that only half of the atoms are headed towards a piston, while the ...
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1answer
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How to contain air ions inside a chamber without loosing their charge?
I would like to create an experiment where I would hold ionized air molecules. Most likely negative O2-1 ions. I am looking for the most appropriate enclosure so that the ions do lose as little of ...
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0answers
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How to calculate energy stored in a hydraulic hybrid system?
My understanding is that hydraulic hybrid systems have two reservoirs - one at high pressure and one at low pressure. I also understand that the working fluid can then be pumped between these two ...
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2answers
78 views
Expansion of an ideal gas at constant pressure
I approach these expansion problems like so:
The gas and the surroundings(piston+outside) are at the same pressure at first. We heat the gas. The pressure rises inside the syringe a bit. The gas ...
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1answer
35 views
Is it possible to calculate the mass of gas remaining in a cylinder simply by measuring temperature and pressure?
Given $pV=nRT$, where;
$p$ = Pressure, $V$ = Volume, $n$ = Number of moles of gas, $R$ = Gas constant and $T$ = Temperature in Kelvin.
Also, the mass can be calculated by;
$m = nM \rightarrow n = \...
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0answers
60 views
Derivation of the wind load formula
I am trying to derive the wind load formula:
$F_d = \frac{1}{2} \rho v^2 A C_d$
in which I assume the drag coefficient to be equal to 1.
My starting point is that the momentum of a rectangular wall ...
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3answers
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Partial derivative of $PV=nRT$ with respect to $T$
We all know for an ideal gas $PV=nRT$ then, if we differentiate it partially w.r.t $T$ shouldn't we get
$$\frac{\partial}{\partial T}(PV)=P\left(\frac{\partial V}{\partial T}\right)_P+V\left(\frac{\...
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4answers
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How can I calculate the speed at which a gas flows from one volume to another?
Suppose that there are two rigid Volumes A and B. Each of these contains a gas with know properties (pressure, temperature, number of moles, volume, composition). Suppose also that there is a pipe ...
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Why bulk modulus of air is initial pressure?
So in the definition of bulk modulus the strain part is defined as (∆v/v) where ∆v is change in volume and v is the initial volume and while driving it for air we use the ideal gas law PV= constant ...
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1answer
49 views
Heat transfer of a monatomic ideal gas at room temperature
I have done parts a) and b) but have been stuck on c) for hours I have tried to come up with a formula but can’t come up with a reasonable one - I can’t even see how it is possible. Any help would be ...
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1answer
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How was $C_p-C_v=\left(\frac{\partial P}{\partial T}\right)_{Vn}\left(\frac{\partial \:V}{\partial \:T}\right)_{Pn}$ dervied
I found the following relationship whilest on wiki reading up about heat capacity and cannot figure where the relationship has come from. Would it be possible for someone to maybe outline where it has ...
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1answer
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Thermodynamics - please check my proof that $\partial C_p/\partial p$ = 0 for an ideal gas
Prove
$$\left(\frac{\partial C_p}{\partial p}\right)_T = 0$$ for an ideal gas.
All the $\partial$s are partial derivatives
Please check to see if this makes sense.
We know that
$$C_p = \left(\...
