The ideal-gas tag has no wiki summary.
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How slow is a reversible adiabatic expansion of an ideal gas?
A truly reversible thermodynamic process needs to be infinitesimally displaced from equilibrium at all times and therefore takes infinite time to complete. However, if I execute the process slowly, I ...
6
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1answer
593 views
Collision frequency at surfaces
Collision frequency for particles in gases is well known, and collision theory is used to derive chemical reaction rates in gases, (and particles in liquid solutions as well). Using the mean velocity ...
5
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1answer
219 views
Energy formula for separating $O_2$ from mixture of $O_2$, $NH_3$ and $H_2O$
I have a physics problem I'd like to make sure I get correct.
The practical aspect of this problem is that the photosynthetic efficiency of algae is inhibited with dissolved O2 in the growth medium, ...
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3answers
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What type of substances allows the use of the Ideal Gas Law?
I know that I can use the ideal gas law with pure gases or pure liquids. But can I also use the ideal gas law at saturated gases and saturated liquids as long as they aren't two phase substances?
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Differentiating the ideal gas law
In reading Fermi's Thermodynamics, to show that $C_p = C_v + R$, the author differentiates the ideal gas law for a mole of gas ($PV = RT$) to obtain: $PdV + VdP = RdT$. Now, the only way I am able to ...
4
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1answer
130 views
Ideal gas and diatomic gas with same temperature
If a box of ideal gas and another box of diatomic gas are in thermal equilibrium,
does it mean that the average translational energy of ideal gas particle (A) is the same as that of diatomic gas ...
4
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1answer
171 views
speed of sound and the potential energy of an ideal gas; Goldstein derivation
I am looking the derivation of the speed of sound in Goldstein's Classical Mechanics (sec. 11-3, pp. 356-358, 1st ed). In order to write down the Lagrangian, he needs the kinetic and potential ...
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3answers
220 views
Simple question about a gas in a box with a moving wall
David Albert is a philosopher of Science at Columbia. His book "Time and Chance" includes this example (p 36).
A gas is confined on one side of a box with a removable wall. "Draw the wall out, ...
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3answers
477 views
What does it take to derive the ideal gas law in themodynamics?
How can the ideal gas law be derived from the following assumptions/observations/postulates, and these only ?
I'm able to measure pressure $P$ and volume $V$ for gases.
I notices that if ...
3
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2answers
135 views
With ideal gases, varying quantity of moles, and having a constant volume how do temperature and pressure behave?
I'm trying to build a simulation of gases so I ended-up trying to use law of ideal gases ($PV = nRT$).
In my scenario:
volume is constant ($V=1\rm{m}^3$);
a known quantity of moles are being added ...
3
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3answers
184 views
Understanding mathematically the free expansion process of an ideal gas
I'm trying to understand mathematically that for the free expansion of an ideal gas the internal energy $E$ just depends on temperature $T$ and not volume $V$.
In the free expansion process the ...
3
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2answers
163 views
Will ideal gas law apply to plasma?
I have read that plasma is a state of matter that resembles gas but it consists of ions and electrons coexisting. So my question is : If plasma is just ionized gas, will ideal gas law apply for it ?
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1answer
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Which heated, partially filled bottle will explode first?
This is in reference to a pasteurization discussion on a homebrewing forum.
I have four closed bottles which will explode if containing too much pressure. Two of them are 50% full (A and B), and two ...
3
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2answers
176 views
Ideal gas concentration under temperature gradient
I'm trying to calculate the concentration of an ideal gas in an adiabatic container as a function of position where the top and bottom plates of the container are fixed at temperatures $T_1$ and ...
2
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3answers
2k views
How to deduce E=(3/2)kT?
It says in my course notes that a particle has so-called "kinetic energy"
$E=\frac{3}{2}kT=\frac{1}{2}mv^²$
Where does this formula come from? What is k?
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4answers
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Why are volume and pressure inversely proportional to each other?
It makes sense, that if you have a balloon and press it down with your hands, the volume will decrease and the pressure will increase. This confirms Boyle's Law, $ pV=k=nRT $.
But what if the ...
2
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2answers
104 views
May molecules of ideal gases have an inner structure?
The following question is probably very elementary:
whether molecules of ideal gases may have optic properties?
As far as I understand, when one discusses optic properties, one assumes that molecules ...
2
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1answer
209 views
What would be pressure of 1 kg of photon gas at room temperature put in a volume of 1 liter?
Suppose a number of photons with spectrum corresponding to black body spectrum at 293 K with total energy corresponding to 1 kg put in a box with ideal mirror walls with volume of 1/1000 of a cubic ...
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2answers
801 views
Calculating work done on an ideal gas
I am trying to calculate the work done on an ideal gas in a piston set up where temperature is kept constant. I am given the volume, pressure and temperature.
I know from Boyle's law that volume is ...
2
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2answers
44 views
What are the units of these virial coefficients?
I'm reading some papers for calculating the vapor pressure of alkali metals as a function of temperature, and I've come across some familiar-looking virial expansions, but when I tried to work out the ...
2
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1answer
600 views
Work Done in an Isobaric Process
I am given the information that an air parcel undergoes isobaric heating from 0° C to 20° C, and that's all I'm given. I have to determine the work done by the parcel on its surroundings. I know that ...
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0answers
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How can I interpret negative values of potential evapotranspiration?
If I extract Potential Evaporation (PET, W/m$^2$) from the National Centers for Environmental Prediction (NCEP), climate reanalysis data (downloadable as netCDF files here), there are some negative ...
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1answer
153 views
Canonical partition of a boson gas
I have a 1D gas made of $N$ particles placed in a harmonic potential well, so the Hamiltonian is:
$$ \mathcal H = \sum_{j=1}^N \left ( \frac{p_j^2}{2m} + \frac{1}{2}m\omega^2 x_j^2 \right )$$
The ...
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1answer
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Why does a gas get hot when suddenly compressed? What is happening at the molecular level?
My guess is that the molecules of gas all have the same speed as before, but now there are much more collisions per unit area onto the thermometer, thus making the thermometer read a higher ...
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2answers
597 views
Adiabatic process of an ideal gas derivation
I am working through the derivation of an adiabatic process of an ideal gas $pV^{\gamma}$ and I can't see how to go from one step to the next. Here is my derivation so far which I understand:
...
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1answer
617 views
Calculate mass of air in a tyre from pressure
How can one calculate the mass of air inside a tyre, given a particular tyre size; a pressure, in $kPa = \frac{1000kg}{m\cdot s^2}$; and assuming room temperature, and normal air composition? I can't ...
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2answers
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Is it possible to obtain higher order corrections to the ideal gas law when one allows realistic phenomena to make their way into the equations?
I had an interesting thought today that caused me to ask whether it'd be possible to make corrections to the ideal gas law via introducing terms derived from more realistic phenomena to make their ...
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1answer
367 views
Adiabatic expansion [closed]
I'll start off by saying this is homework, but I ask because I don't understand how the math should work (I don't just want an answer, I'd like an explanation if possible). I understand if this is ...
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1answer
168 views
Difference in vertical stratification of partial pressure due to gravity
Say you have a mixture of two ideal gases in the presence of gravity. There is a vertical pressure gradient on the mixture due to the force balance. This condition is required to prevent the entire ...
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2answers
244 views
Is it Possible to have Adiabatic Processes other than $PV^\gamma$ for the ideal Gas?
Is it possible to represent an adiabatic process for an ideal gas by a formula other than $PV^\gamma=Const$?:
Relevant Considerations:
We always need to connect a pair of arbitrary points/states ...
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1answer
2k views
1
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1answer
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Root Mean Square Speed of Gas
The RMS speed of particles in a gas is
$v_{rms} = \sqrt{\frac{3RT}{M}}$
where $M$ = molar mass; according to this Wiki entry: http://en.wikipedia.org/wiki/Root-mean-square_speed
The gas laws ...
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1answer
70 views
Thermodynamic process when nebula is heated
The basic thermodynamics problem is stated as follows.
The nebula contains a very tenuous gas of a given number density (atoms per volume) that is being heated to a given temperature. What is the ...
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1answer
174 views
Velocity of real gas molecules?
It is known that the velocity of ideal gas molecules can be computed using Maxwell-Boltzmann law of distribution of molecular velocities, with average velocity given as:
...
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2answers
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Is it possible to find the number of gas atoms/molecules in a box when the number is small?
Given very low number of particles in a system (e.g. in the 100s), is there a way to accurately measure the number of particles in the system? Assume temperature, pressure and volume is constant and ...
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1answer
281 views
What is the pressure drop in a venturi with a compressible fluid?
I would like to know if there is an equation to predict the pressure drop in a venturi device using a compressible fluid as the working medium. In particular, I'd like to use this equation to predict ...
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1answer
63 views
How fair is it to say that all chemistry arises from failures of the ideal gas law?
I was reading here about how the ideal gas law assumes point masses and non-interaction. Is it fair to say that all chemistry arises from failures of that?
Of course, such a sweeping generalization ...
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1answer
64 views
Volume of gas at which relative fluctuation of gas density occurs
I have the following question:
In what volume of gas occurs 10 % relative fluctuation of gas density
under pressure of $10^5\text{ Pa}$ and temperature of $293.15\text{ K}$?
I don't understand ...
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1answer
54 views
Calculating Air Density Lapse With Altitude (Specifically, pressures)
This might be a bit more of an engineering question, but I'm calculating air density drop-off with altitude, and I'm having some problems calculating the pressure (I'll run through my method). This ...
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0answers
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Centrifugal Compressor Flow Rate
For a centrifugal compressor, as found in most turbochargers on internal combustion engines, is there a noticeable change in flow rate versus a naturally aspirated flow rate? In other words, does the ...
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3answers
646 views
When a gas expands against an external pressure of 0, must the stopper on the cylinder be massless?
Basically, I need to conceptually understand why the work a gas does is the integral of pressure external * dv and is 0 when pressure external is 0. I understand why dw = - p external * dv and so ...
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1answer
124 views
Ideal gas temperature and pressure gradients?
Consider an ideal gas in a $d\times d\times L$ box with the $L$ dimension in the $x$-direction. Suppose that the opposite $d\times d$ sides of the box are held at temperatures $T_1$ and $T_2$ with ...
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1answer
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In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Say I have an ideal gas that has a known $P_1$, $P_2$, $T_1$, and $T_2$ undergoing a reversible adiabatic process. I want to find the work done so I must use $PV = RT$ to get the change in $V$, so ...
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2answers
78 views
Temperature change inside pressure chamber
Let's say there is a pressure chamber with some sort of sample / specimen (e.g. protein crystal) in it. Now I apply a certain amount of gas pressure, e.g. 10 or 20 atm. Let's say I use xenon as a gas. ...
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1answer
49 views
Performing work on a box of gas by lifting it, and first law of thermodynamics
What happens if we lift a box of ideal gas? Work is done to the box but no heat is getting into it. So does it's internal energy increase by the amount of work done? Or is it that lifting is not ...
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1answer
1k views
Work Done by an Adiabatic Expansion
I am given the information that a parcel of air expands adiabatically (no exchange of heat between parcel and its surroundings) to five times its original volume, and its initial temperature is 20° C. ...
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1answer
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Ideal gas law, pressure increase and temperature
If I had a container, full with air, and I suddenly decreased the volume of the container, forcing the air into a smaller volume, will it be considered as compression, will it result in an increase in ...
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1answer
678 views
Work on ideal gas by piston
Imagine a thermally insulated cylinder containing a ideal gas closed at one end by a piston.
If the piston is moved rapidly, so the gas expands from $V_i$ to $V_f$.
The expanding gas will do work ...
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1answer
123 views
Expansion of Helmholtz energy
To get an expansion of Helmholtz energy of
a) an ideal gas
b) a Van der waals gas
we must integrate
$\left ( \frac{\delta A }{\delta V} \right )_{T}=-P$
I saw the solution is :
Can you ...
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0answers
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Find the workdone to increase the temperature of an ideal gas by 300c if gas is expanding under [closed]
Find the work done to increase the temperature of an ideal gas by $30^o C$ if gas is expanding under the condition $V \propto \dfrac{t^2}{3}$.
