# 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 ...
1 vote
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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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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 $... • 323 15 votes 7 answers 4k views ### Why is there a maximum humidity? Recently I've been browsing humidifiers for my room. Everyone "knows" that humidity is measured in percentages, and 100% humidity is the maximum humidity that the air "can hold" - ... • 6,468 2 votes 0 answers 38 views ### In kinetic theory of gases, in finding connection between pressure and molecular kin. energy, why$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$molecules is assumed to be enclosed in a cubical box ... • 923 1 vote 1 answer 45 views ### Can a cold gas be considered as ideal at a very high speed? Considering a plane flying in the atmosphere, my book uses the perfect gas law$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}... 