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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Can the ideal gas law be rewritten to include the entropy instead of either temperature, pressure, or volume?
The equation of state for and ideal gas states, $PV = mRT$. Since entropy is a state variable, can the equation of state be rewritten in terms of entropy?
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How can I find the Heat capacity in this problem? [closed]
There is a cylinder with a piston with initial volume $V_0$ filled with gas. The piston is with area $S$ and is connected to the wall of the cylinder with a spring that has coefficient $k$. There is ...
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In a polytropic process, how can I prove the validity of this equation: $v_1 = v_2 (\frac{T_2}{T_1})\exp{\frac{1}{1.1-1}}$?
in this exercise, I have hydrogen and it follows this thermodynamics cycle,
1-2 } --> polytropic process with exponent $n = 1.1$,
2-3 } --> adiabatic process,
3-1 } --> isobaric process,
my ...
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Will the ideal gas equation change if we consider non equillibrium condition and then use kinetic approach and thermodynamic approach? [closed]
My teacher said that in equilibrium no matter what approach we use we arrive to same result i.e. in this case ideal gas equation. So if we were to use the two approaches (thermodynamics and kinetic ...
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The combined gas law and the ideal gas law
This might sound a bit weird, but I do not understand what I am missing!
We have the combined gas law:
$$PV/T$$
And the ideal gas law:
$$PV/nT$$
My first question is that why didn't French physicist ...
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Why does R. Feynman states that in a low-density gaseous enviornment, the pressure exerted by the molecules is proportional to density?
I was reading Dr. Feynman's Physics Lectures Vol 1 and in the first chapter about the atomic theory, he gives the example of a piston-type container where he explains the proportionality of force and ...
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Boyle's law ( Volume and Pressure )
I am confused about the fact that (The volume is inversely proportional to the pressure)
I understand that when the atmospheric pressure increases the volume of our object decreases.
But why should it ...
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How the temperature used in second law of thermodynamics and ideal gas law equivalent? [closed]
I was reading Theory and Problems of Thermodynamics by Schaum's Outline series and there the author starts from some axioms (which are the thermodynamic laws, excluding the zeroth and third). Then he ...
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Beyond the energy equipartition, what is the uneven law?
There is a celebrated energy equipartition theorem, it works fine for many systems. But it requires the dense filling of the surface of constant energy. What if there are other conserved quantities, ...
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Can you use the ideal gas law for flow in pipes?
Or is it limited to gas in a container?
This would be in a low temp and pressure, say 70F and 1atm.
The only assumption I can think that might be violated is:
The gas molecules are assumed to be in ...
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How can we explain expanding gas temperature at the microscopic level?
An insulated piston and cylinder contains an ideal gas. We pull the piston and expand the gas volume inside the cylinder.
I understand the temperature drops due to this expansion. But, how can we ...
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Gas temperature in a constant volume
An insulated container (constant volume, adiabatic) contains an ideal gas.
We open the container's hatch for a few seconds and let some particles escape from the container, then we close the hatch. We ...
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What is the theoretical limit of adiabatic lapse rate as derived in introductory books?
In meteorology, the Earth's atmosphere up to the stratosphere is subject to processes that are, to a good approximation, adiabatic in nature.
Based on the state equation of an ideal gas, the adiabatic ...
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Balancing forces in a movable piston
I need to balance forces on the "plate" of a piston situated in a closed container of a given spring constant k and area A with a compression x. It is also given that the initial pressure ...
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Peng-Robinson and specifc molar volume
We have the Peng-Robinson EOS
$p = \frac{R\cdot T}{V_{m}-b} - \frac{\alpha \cdot a}{V_{m}^{2} + 2 \cdot b \cdot V_{m} - b^{2}}$
with
$a = \frac{0.457235 \cdot R^{2} \cdot T_{c}^{2}}{P_{c}}$, $b = \...
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Why is the ideal gas law said to be classical when it assumes quantized energy states? [duplicate]
We are told in my thermodynamics class that the ideal gas law is a classical law that follows from classical mechanics. However, when we derived it as follows, we computed the partition function $Z_1$ ...
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Mercury In a J tube
This is a doubt on question 5.3 from the 5th chapter of the book Heat and Thermodynamics by Zemansky and Dittman. The problem statement is as follows:
Mercury is poured into the open end of a j-shaped ...
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Type of thermodynamic process
This is a doubt on question 5.13 from the 5th Chapter of the book Heat and Thermodynamics by Zemansky and Dittman. The question says we have a cylinder with a movable piston, on either side of which ...
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Gas Volume of compressed oxy/fuel in pressurized cylinder
For one of our projects we are at present using quite large amounts of gas & oxygen.
What I was trying to figure out was how to calculate the total available amount of gas in a cylinder (be that ...
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Why can $\rm CO_2$ significantly displace $\rm O_2$ when both are nearly ideal at ambient?
There are YouTube videos where a person hold a cup of $\rm CO_2$ and pour it on top of burning candles to distinguish them. As far as I know, $\rm CO_2$ and $\rm O_2$ both are almost perfect ideal gas ...
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Temperature of a particle moving in a gravity field
I have a seemingly simple question that is still puzzling to me.
The temperature of an atom is proportional to its kinetic energy. If an atom now moves upwards in a gravity field, its kinetic energy ...
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Finding chemical equilibrium with an application to the Sun
Consider the following reversible reaction: $\rm H_{2}{\rightleftharpoons}2H$. To find chemical equilibrium, we use the chemical equilibrium constant. There are two equations for the chemical ...
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Determining the pressure after an adiabatic compression
(Please avoid explaining it with calculus)
I need to determine the pressure of air after an adiabatic compression. I have been given a low starting temperature T1 and a high final temperature T2 and ...
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Why low volume of atom indicates low attraction forces between atoms which could determine if a gas is ideal or not?
I have the following question about ideal gas.
A helium atom has a volume of 4.9 x 10^-31 m^3. Explain with the reference to the kinetic model, why this sample of helium can be assumed to be ideal (...
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Is it possible to split up air into its parts by something like centrifuging? [duplicate]
Is it possible to centrifuge cases to split them up into their compounds (at least temporarily)?
For instance, the air is composed of 78% nitrogen, 21% oxygen, 0.9% argon, and other gases. Under what ...
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Difference between two Enthalphy equations
I am revising thermodynamics and in the textbook, the enthalpy equations are stated in two forms.
"H=U+pV" and "h=u+pv". What is the difference between the two equations.
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Work done in expanding a gas
Let's suppose a monoatomic gas of $n$ moles has been expanded from $V_1$ to $V_2$ volume keeping pressure constant. Now from the ideal gas law,we have $PV=nRT$. Taking differentials of both sides,we ...
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How to derive Dalton's law of partial pressure for a non-ideal gas?
According to dalton's law,
$$p_i = p_°X_i$$
Where $p_°$ is total pressure of gas mixture and $X_i$ is the mole fraction of the $i^{th}$ component of mixture. This is very easy to derive for an ideal ...
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Is really change in temperature inversely proportional to primary kinetic energy of ideal gas molecules?
I was trying to derive Charles law. While deriving I got two results and one of these was unexpected. Those are,
$$\Delta t \propto \Delta E_k$$
Where, $\Delta t$ is change in temperature and $\Delta ...
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Clausius-Clapeyron relation for high pressures
I can see that the Clausius-Clapeyron relation depends on the change in specific volume $\Delta v = v_g (1 - \frac{v_c}{v_g}) = v_g - v_c$, with $v_c$ equal to the volume of the condensed phase and $...
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Why is there a maximum humidity?
Recently I've been browsing humidifiers for my room. Everyone "knows" that humidity is measured in percentages, and 100% humidity is the maximum humidity that the air "can hold" - ...
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In kinetic theory of gases, in finding connection between pressure and molecular kin. energy, why $N/2$ & not $N/6$ molecules are assumed to hit wall?
In my book While driving a relation between pressure and average kinetic energy of a single molecule [i.e. $P = (Nmv^2)/2$ ], an ideal gas of $N$ molecules is assumed to be enclosed in a cubical box ...
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Can a cold gas be considered as ideal at a very high speed?
Considering a plane flying in the atmosphere, my book uses the perfect gas law $pV=n\bar RT$. Yet, as the plane itself is taken as the reference, the air ($T=-50°C$) has a speed of $800 \ \mathrm{km/h}...
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Average height of the particles in a monoatomic ideal gas when $T=0$
Consider a classical ideal monoatomic gas (made of $N$ particles in the canonical ensemble) confined in a prism with infinite height. Consider the hamiltonian of a particle as
$$H = \dfrac{p^2}{2m} + \...
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In adiabatic process, is work done in compression is equal to the work done in expansion? Please suggest
Assume a reversible adiabatic process where is there no exchange of heat from cylinder to environment. I assume that the work done on the system will be equal to the work done by the system. So, the ...
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Nature of expansion of an ideal gas [closed]
Consider an ideal gas expanding irreversibly in a piston-cylinder system against a lower external pressure. According to this graph, does the piston move such that the internal pressure changes with ...
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Increase of entropy when mixing two gases [duplicate]
I was reading my textbook and ran into this case: two ideal gases in a container are initially separated by a wall, with the same volume, the same amount (in moles), the same temperature, and the same ...
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How can the combined gas law be derived from the other three if none of the variables remain constant?
In Boyles, Charles and Gay-Lussac's Gas Laws, one of the variables has to remain constant in order for them to be true. Therefore, how is it possible that the Combined Gas Law is true if NONE of the ...
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Why is the final temperature of irreversible adiabatic processes higher than that of reversible adiabatic processes?
Suppose an irreversible adiabatic expansion process and a reversible adiabatic expansion process are starting from the same initial state, say, P1V1. Now, let both of these processes have equal ...
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Linear transformation in $pV$ [closed]
Say ideal gas is in a state $p_1$, $V_1$, $T_1$ (known). I compress this gas such as $\frac{dp}{dV}$ is a constant. I want to reach $T_2$>$T_1$ and I need the values for $\frac{dp}{dV}$. Would it ...
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For an effused gas through a hole that obeys Maxwellian distribution, what is the average energy of the gas molecules hitting the surface?
For the effusion of gas that follow Maxwellian distribution, given the flux
$$
d\Phi(v,\theta)=\frac{1}{2}nv\ f(v)dv\sin\theta \cos\theta\ d\theta
$$ I need to show that the average energy of the ...
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Derivation for ideal gas law in 2d
So it's easy to find the derivation of the ideal gas laws in 3d, however when considering a 2d system, I was wondering if these equations would still apply?
Or would, for example, pressure be $p =\...
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What is the value of $p$ in Isothermal Bulk Modulus? [duplicate]
So after differentiating the ideal gas equation and rearranging a bit, we get:
K=p
This was well and good until I started doing numerical problems and I realized I don't know whether to equate K to ...
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Absolute Zero, Charles's Law [closed]
I think my questions is almost embarresing but anyway: I try to estimate absolute zero (in Celsius) by using Charles's Law. I basically try to reproduce this experiment:
https://www.youtube.com/watch?...
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Joule thompson effect?
Basic question, since $-P$d$V$ is the internal energy of work then how can an expanding gas (i.e. positive d$V$) have an increase in temperature based upon whether it is above or below the "...
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How does temperature constant in isothermal process?
1 mole of an ideal gas (at 25°C and 1 atm pressure) is placed in a cylinder with a piston. Ambient temperature is 25°C and atmospheric pressure is 1 atm. Now if heat is applied to the system (ideal ...
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How work is done by rapid expansion or compression at adiabatic process?
In adiabatic processes, when a gas is compressed rapidly, the internal energy of the gas increases and work is done on the gas. Similarly in expansion the internal energy decreases and work is done by ...
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Does unsaturated vapor obey Pressure law?
My textbook says unsaturated vapor obeys Charles and Boyle's law. So I think it should obey pressure law too. But from a certain temperature to dew point at unsaturated state, the mass of vapor ...
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Why doesn't the number of $\rm H_2O$ molecules evaporated depend on the number of the other gaseous molecules?
I have a conceptual contradiction. Say we remove a partition between liquid water and gaseous nitrogen at constant volume and temperature. The average number of gaseous water molecules will increase ...
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Total entropy generated for a sudden expansion of an ideal gas
Topic: Adiabatic, irreversible expansion of an ideal gas.
Suppose you have an ideal gas in an insulated piston-cylinder arrangement originally at $P_0,T_0,V_0$. The piston is massless and frictionless....
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