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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Gas confined in a box
I have a gas with $N$ particles in $D$ dimensions confined in a box, I have written the Hamiltonian as
$$
H = \sum_{p=1}^N\sum_{d=1}^D\frac{p^2_{pd}}{2m}+V_0[\theta(-q_{pd})+\theta({q_{pd}-L_d})]
$$
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Why am I getting a different answer than my book?
Problem:
$1 mol$ helium gas is kept at $2\times10^5Pa$ pressure and $600K$ temperature in a heat-insulating cylinder on top of which a frictionless piston is attached. Then the cylinder's pressure was ...
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Physics 1 HW Problem: Finding the relative humidity given change in temperature [closed]
Air that is at its dew point of $5°C$ is drawn into a building where it is heated to $25°C$ .
What will be the relative humidity at this temperature? Assume constant pressure of $1.0 \ \mathrm{atm}$. ...
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1answer
43 views
Maxwell-Boltzmann distribution as the most probable [closed]
In Statistical Physics: An Introduction, by Daijiro Yoshioka, there's a neat derivation of the Maxwell-Boltzmann distribution as the most probable distribution of an Ideal Gas. He uses the method of ...
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Elastic potential of a balloon and pressure equilibrium
There are two different pressures acting on the surface of a balloon, the external one is clearly weaker than the internal one, so there must be a force that create equilibrium and avoid the balloon ...
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Deriving a formula for the pressure exerted on a container wall due to a single particle colliding on it/bouncing off it
I am writing a python script to simulate ideal gas particles in a circular container (in 2 dimensions only).
One thing I need to do is add code to calculate the pressure on the container due to a ...
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Does the compressibility factor of a gas depend on the number of moles of a gas?
$$\text{Compressibility factor}, Z=\frac{PV}{nRT}$$
Apparently, $Z$ depends on $n$. However, I suspect that $Z$ doesn't depend on $n$ because according to wiki, "It (Compressibility factor, $Z$) ...
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Does root mean square velocity depend on the number of moles of a gas?
$$PV=\frac{1}{3}mNc^2$$
$$[\text{P=Pressure,V=Volume,m=molecular mass in gram, N=number of molecules, c= rms velocity}]$$
If $N=N_A=6.022\times10^{23}$, $mN_A=M=\text{Gram molecular mass}$:
$$PV=\frac{...
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2answers
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RMS velocity of a gas vs RMS velocity of a gas molecule, which is a more appropriate term?
I'm a bit confused by the terminology. Is it the RMS velocity of a gas, or the RMS velocity of the gas molecules or of a gas molecule?
Similarly, is it the mean velocity of a gas, or the mean velocity ...
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1answer
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What will happen when a gas cylinder is taken to space (vacuum)?
Inside the atmosphere, I guess the atmospheric pressure negates the pressure exerted by the gas that's inside a gas cylinder. However, when taken to a vacuum (space), Will the gas cylinder burst due ...
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Why am I getting different values here by using different units? [closed]
Problem 1:
At $27^{\circ}C$ and $\frac{77}{76}atm$ pressure, how many moles of methane gas are present in $20L$ methane?
Using SI units:
$$n=\frac{PV}{RT}$$
$$n=\frac{101325\times\frac{77}{76}\times ...
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1answer
29 views
If saturated vapor does not obey ideal gas laws then how is mass of the saturated vapor proportional to the saturated vapor pressure?
My textbook mentions that unsaturated vapor obeys ideal gas law but saturated vapor does not. I could understand that air/vapor are not ideal so they won't obey ideal gas laws. But how can unsaturated ...
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1answer
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Has this problem about Boyle's law been done by my book accurately?
Problem:
The volume of an automobile engine's cylinder is $410mL$. A mixture of gasoline and air is present in it. The pressure exerted by the cylinder on the mixture is increased from $1atm$ to $9....
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2answers
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Adiabatic temperature increase given work done on (ideal) gas
I'm playing around with a Euler's method simulation of an adiabatic compression/decompression process on an ideal gas.
If I have a volume of gas and I contract its volume slightly, I will be doing ...
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Why is the the temperature change due to the combustion of paraffin wax so high (10000 Kelvin)?
I'm trying to work out the temperature change (I got something like 10k Kelvin,hotter than the Sun's core...) caused by the combustion of paraffin wax which has a molar enthalpy of combustion $E^{wax}...
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1answer
56 views
Temperature increase needed to make pistons not move - where is my calculation wrong? [closed]
I feel like I'm missing something here.
2 pistons are connected like in the picture.I know the area of the big cylinder is 100 $cm^2$ while the one of the small cylinder is 50 $cm^2$ and that the ...
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0answers
24 views
Why do we use the time taken between collisions for the time taken for the collisions to occur when deriving the pressure for an ideal gas
Why do we use the time taken between collisions for the time taken for the collisions to occur when deriving the pressure for an ideal gas $pV=1/3Nmc^2$.
The impulse of the collision is $2mv$. Force = ...
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1answer
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Why Each degree of freedom, (i.e. motion in $x$, $y$ or $z$) has $\frac{1}{2} k_B T$ worth of energy associated with its random motion?
I am trying to interpret the result of
$\frac{3}{2}k_BT=\frac{1}{2}m\langle v^2\rangle$
I understand that temperature is equal to the average kinetic energy associated with particle motion.
$T=\frac{1}...
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2answers
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How does this author conclude that the volume of the gas is zero at -273.15 degree Celsius?
While reading Gaskell and Laughlin's Intro to ThermoD, I was stuck on something. The relevant passage is:
"In 1802, Joseph-Luis Gay-Lussac (1778–1850) observed that the thermal coefficient of ...
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1answer
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The heat capacity of an ideal gas at a constant volume
On the graph:
blue line is the heat capacity of a classical monatomic ideal gas at constant volume;
the red line is the heat capacity of a classical monatomic ideal gas at a constant volume, taking ...
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76 views
Why is the work a function of the mass's pressure?
A gas is confined in a closed container with a movable piston. The container is kept in a hot water bath. Blocks of different known masses are placed on top of the piston one at a time, and the gas is ...
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Why does an elasticity approach for an adiabatically compressed bubble give a different answer?
Problem (inspired by this question): a bubble of ideal gas at pressure $P_0$ and volume $V_0$ is adiabatically compressed to conditions $P_1, V_1$ such that its radius $r$ is reduced by $a$, where $a\...
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Real process connecting two states of a gas?
If we start with an ideal gas at state 1 and perform an isentropic compression, then follow this with an isothermal expansion we could end up in state 2 that has higher temperature, higher pressure, ...
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1answer
42 views
Entropy of perfect gas function of internal energy and number of particles [closed]
In a statistical physics lecture, I found an equation describing the entropy $S$ of an ideal gas and it is said that equation can be obtained thanks to elementary thermodynamics formulae.
The equation ...
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1answer
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Recovering Maxwell-Boltzmann distribution from ideal-gas law
I'm reading the Blundell) Concepts in Thermal Physics_2thed Chap6 Pressure part. Before this, author shows that if we ignore the internal energy of molecules and just consider kinetic energy $\frac{1}{...
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1answer
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Generally will the power output from a heat engine increase as the work from this engine increases?
Generally speaking, does increasing a heat engine's work will essentially increase the power output? Whether this heat engine was a turbine, vechile or whatever.
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2answers
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Doubt in derivation of pressure exerted by ideal gas
In books the derivation of pressure exerted by a gas on a closed container is derived for a cubical geometry, but since it contains number of molecules per volume (denote it by $n$) the books say it's ...
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1answer
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Ideal Gas Law paradox
When volume is not constant and temperature increases, pressure remains constant. ie. Charles Law.
But if you have a manometer and you heat the gas flask, volume of gas in gas flask increases since ...
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1answer
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What kind of intra-particle interactions give rise to heat diffusion in a gas?
I want to consider an $N$ particle gas in a box initialized so that $k < N$ particles have some velocity magnitude $v_\mathrm{hot}$, and the remaining $N-k$ particle have velocities distributed (e....
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1answer
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Physics of filling a tank with compressed air to a certain pressure setpoint
Let's say we have this situation:
There is a known volume tank, that is empty and its pressure is atmospheric. It has an inlet, that lets in compressed air. The goal is to reach 2 bars of absolute ...
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1answer
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Conceptual: Pressure change in closed very long pipe
Let's say I have a very long pipe with a very small diameter with one closed end and a tight fitting piston.
If I pull the piston to increase the volume and/or push the piston to reduce the volume, ...
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2answers
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Ideal gas undergoing linear process on $V$-$T$ graph must be isobaric?
One mole of an ideal gas in initial state A undergoes a cyclic process ABCA, as shown in Fig. Its pressure at A is $P_0$. Choose the correct option(s) from the following.
(A) Internal energies at A ...
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Why doesn't an ideal gas undergoing an isobaric process violate the second law of thermodynamics
I have been stuck on this for the past few hours, and still have got no resolution:
Let's say that we have an isobaric process being done by $1$ mol of a gas. Accordingly, we'll be using gas laws and ...
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1answer
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Pressure Gradient in Astronaut’s Centrifuge?
Status is no progress yet
Intro
Recent questions mentioned pressure gradients in a box. If you weigh a box in a vacuum, the gas contributes its weight with a pressure gradient inside the box. If you ...
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Does farting make the room cooler, or warmer?
It's a hot summer day and you've just had some refreshing salad. Unfortunately all the veggies seem to have caused some... gas. Is this good news, or bad news, as far as the physical temperature of ...
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Is there a pressure gradient in a stationary gas with a temperature gradient?
Consider a gas with ideal equation of state $P = n k_{\rm B} T$, in a fixed rectangular container with two opposite walls maintained at different temperatures, under conditions where there are no ...
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2answers
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Pressure exerted by an ideal gas according to kinetic theory of gases
In my textbook and Wikipedia, I have observed that force exerted on a wall of the container by one molecule is taken into account. Such that $F=\frac{mu} {\Delta t}$ where ${\Delta t}=\frac{2l}{u}$. ...
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1answer
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Can gas in a room rotate a fan with asymmetrical spokes?
I was asked this question in an interview. The figure in first part of the question was drawn as shown.
The question was to draw the angular position of the point marked on the rim with time. It ...
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2answers
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Thermodynamics and enthalapy
In my chemistry book it says that
To quantify the heat flow into or out of system in a constant pressure process we use a property called enthalpy
But they haven't mentioned constant volume. As in ...
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4answers
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Why is the time $\frac{2L}{v}$ in the derivation of $P=\frac{Nm\langle v^2\rangle}{3V}$
In the derivation of $P = \frac{Nm\langle v^2\rangle}{3V}$, why do we take $\mathrm{d} t = \frac{2L}{v}$ for $F = \frac{\mathrm{d} p}{\mathrm{d}t}$ when the particle collides with the wall of the ...
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1answer
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Find the average velocity of gas atoms [closed]
The following problem arose from trying to solve a textbook problem and I don't know if I made some miscalculation or I should assume something that I don't know. I'm given helium in a balloon and I ...
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Vapor Pressure in Heated Pressure Vessel
This question is a bit complex, so thanks in advance for addressing it!
I'm working on a reaction vessel that heats a water solution to 95°C to perform chemical reactions. The design is a ...
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3answers
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What's the difference between a perfect fluid and an ideal gas?
This is how I understand it at the moment:
A perfect fluid is a collection of non-interacting particles, which are as a whole characterised by energy and pressure.
An ideal gas is also a collection ...
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1answer
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Is Ideal gas with $n\gg n_Q$ (Quantum) concentration effectivly at $T = 0$?
For ideal gas with identical spin-½ fermions the fermi energy is:
$${\epsilon_{\text{f}}={\frac {\hbar ^{2}}{2m_{0}}}\left({\frac {3\pi ^{2}N}{V}}\right)^{2/3}}$$
and so we can write:$$\frac{\...
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0answers
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Is it possible to create gases with high rotational temperature and low translation temperature?
Has anyone been able to take a monoatomic gas (ex: Helium) and put it in a state where the individual atoms are moving at extremely low velocity (low "translational" temperature) but the ...
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2answers
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Why does root mean square speed of gases remain constant?
I came across a question in which speed distribution of molecules of an ideal gas trapped in a vessel and the temperature of the gas was given. Then it was given that the molecules of a particular ...
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2answers
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Would the relationship of pressure and volume of gas change if the gas type is changed?
Question. There is an experiment investigating how a gas's occupying volume changes when its exerting pressure alters. As a result, a graph of pressure versus volume has been plotted, which is half of ...
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How much blue sky comes from each altitude; dependence of atmosphere's dielectric constant and isothermal compressibility with altitude?
Background
left: from this answer to Moon during the day with bright blue sky light right: from Why does Unity look transparent? below: from this answer
note Unity is the bit in the middle.
I'm ...
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What does the equation $W=RT(\ln V_1/V_2)$ mean?
I understand how this equation is derived but I do not know what it means. I understand $R$ can be taken to be work done by a ideal gas with a unit temperature increment. $T$ is the temperature (as a ...
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1answer
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Getting different results from modelling the system in probability distribution and physical intuition in statistical mechanics
There is a problem given as -
N molecules of an ideal gas are in a container of volume $V_o$. If a molecule has a same probability of being at any point in the container. The variance of number of ...
