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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How does nitrogen narcosis occur?

I'm confused as to how the partial pressure of nitrogen inhaled from an air tank while scuba diving increases as you descend deeper. Obviously the pressure of the water above you increases the deeper ...
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How does the partial pressure of oxygen relate to its concentration in water?

I've read that the partial pressure of oxygen in water will be the same as the partial pressure of oxygen in the atmosphere, but that the saturation of oxygen in water is dependent on factors like ...
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How does the density of the air affect our perception of temperature?

The classic experiment where you have someone put one hand in a bowl of hot water and the other in a bowl of cold for a while then move their hands to a warm bowl is a classic demonstration that our ...
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Why isn't the free expansion of a gas in an adiabatic container isentropic?

If you expand a gas adiabatically using a piston, the process is isentropic. However, if you simply remove the piston and let the gas expand freely, the process is now not isentropic. What makes these ...
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Quality of ideal Gas approximation?

I know that modeling gases as ideal gases includes two approximations: approximating Particles as points regarding the collisions with macroscopic objects neglecting inter-particle interactions The ...
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Power To Compress Ideal Gas In A Piston

I am familiar with isothermal and adiabatic ideal gas compression problems where a force is exerted on a piston of area A to move it some displacement in order to calculate work done. However I am ...
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Does pressure decay exponentially for a mixture of gases?

According to this answer, the partial pressure of a gas decreases exponentially in height, when placed in gravity. For a mixture of gases, the partial pressures of each component follows this law ...
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Adiabatic Transformations and ideal gas relations

For an adiabatic transformation of an ideal gas I know that from equation, $C_v=\frac{dU}{dT}$ I can rewrite it using the relations, $dU=dQ-dW$ which can give us $dU=-pdV$ to rewrite the first ...
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Free energy for ideal gas: constant in logarithmic expression

I'm working on an equation of state implementation based on the free energy minimization. This method had be hugely popularized in astrophysical community by D"appen, Hummer and Mihalas (hence ...
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What is the useful limit for ground effect on an object? [closed]

What the maximum size an object can benefit from ground effect? Also known as riding a cushion of air created from flying close to the ground, some birds can use this effect to fly with less energy ...
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What is the difference between an equation of state, and a state function?

Wikipedia seems to list them as two different things, (Equation of State, State Function); however, it seems like both pages are describing the same thing. Is there really any difference between the ...
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Motion of 'temperature-measuring device' w.r.t. to the object

A few days ago I had a discussion on the notion of temperature coming from the Kinetic theory of gas (KTG). I am applying the idea in below two cases. Case-I: Take the example of an ideal gas in a ...
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Stress-energy tensor for ideal gas (not perfect fluid)

If I understand correctly, an ideal gas has viscosity (i.e. shear stress) whereas a perfect fluid does not. So I am right in thinking that the stress-energy tensor for an ideal gas should not be ...
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Diffusion of gas mixtures through a membrane

Suppose we have a mixture of gases $k = 1,2 \ldots$ in a large volume with constant pressure and temperature (via external pressure and temperature control). We immerse a small volume separated via a ...
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Distribution of collision point position of an ideal gas particle

Assuming a system consists of N identical particles in gas phase and very dilute. Particles are assumed to be hard-sphere with elastic collision. At instance only the particles with a speed of μ is ...
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Does it become harder to compress a gas beyond a certain point?

While I was reading a book, I came across the following: Real gases show deviations from ideal gas law because molecules interact with each other. At high pressure molecules interact with each other. ...
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Why does symmetry reduce heat capacity?

For monatomic gasses, the heat capacity approaches $3R/2$ because there are three degrees of freedom (DOF) of translational motion. For diatomic gasses it approaches $7R/2$ because the symmetry about ...
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How can $dQ=nC_mdT$ be used in various thermodynamic proofs?

I have seen the equation $dQ=nC_mdT$ for ideal gases often used in certain proofs in thermodynamics(such as $C_m$ for polytopric process). However, I feel this expression is wrong as a general ...
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Query about average velocity of gas molecule

When we can say that gas molecule average velocity is 0 and in which case it is not possible?
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Maxwell's distribution curve for different gases

I have studied Maxwell's velocity distribution curve for same gas in different temperatures. I tried to plot the graph for gases of different molar mass. I understood that the most probable speed will ...
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Can I solve this problem using Gay Lussac's law of pressure? [closed]

This question came in the Khulna University admission exam 13-14 Q) When a tire is pumped at temperature $27^{\circ}C$, it bursts abruptly after its pressure becomes $2atm$. What is its final ...
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Why don't we use the "degree of freedom" as a factor in the ideal gas equation?

For an adiabatic process, the ideal gas follows the equation $$ PV^{\gamma}= constant$$ The equation above implies that the pressure of an ideal gas (under adiabatic process) depends on the "...
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Variation of Relative Humidity (RH) in closed room vs outside

I have an insulated garage room with the doors closed, and I am interested to monitor the Temperature + Relative Humidity (RH) inside the room, compared with outside. I have taken some readings ...
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Does there exist a generalized 'ideal gas law' for every pair of thermodynamic variables, e.g. $$ \gamma A = NkT$$ vs $$PV=NkT$$ for surface tension?

Does there exist a generalized 'ideal gas law' for every pair of thermodynamic variables, e.g. $ \gamma A = NkT$ for surface tension? The first law or thermodynamic relation says: $$ dE = \delta Q + \...
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Entropy of real substances - Is it possible to decompose arbitrary $p$-$V$ cycles of real substances in small Carnot cycles of an ideal gas?

In physics textbooks it is proved that $\oint\frac{δQ_{rev}}{T}=0$ by decomposing an arbitrary cycle in the $p$-$V$ diagram into infinitesimal Carnot cycles. Does the arbitrary cycle have to be a ...
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Does $U(S,V,N) = \alpha e^{\frac{S}{N c_v}} V^{\frac{c_v-c_p}{c_v}} N^{\frac{c_p}{c_v}}$ really imply zero entropy?

According to this question, for some ideal gas $$U(S,V,N) = \alpha e^{\frac{S}{N c_v}} V^{\frac{c_v-c_p}{c_v}} N^{\frac{c_p}{c_v}}$$ From this, $$T = \frac{\partial U}{\partial S} = \frac{1}{Nc_v}U \...
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Why doesn't $dU=nC_{v}\,dT$ hold for all substances?

Consider the following proof for change in internal energy of real gases, liquids and solids(assuming Non-$PV$ work $=0$): Let X denote real gases, liquids, and solids The First law of thermodynamics ...
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Doubt with partial pressures

I have a conceptual doubt about partial pressures. Suppose you have a closed system composed of a gas mixture, say Argon and Helium. If they behave according to Ideal Gas Law, then the molar fraction ...
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Does $PV=nRT$ hold for the endpoints of an irreversible process? [closed]

I have read the following:- $PV=nRT$ holds throughout a reversible process $PV=nRT$ does not hold throughout an irreversible process because the ideal gas law is only applicable for gases in ...
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Heat Transfer by Conduction for Ideal Gases

I've recently read some chapters on heat transfer, and I was confused by an equation that described the thermal conductivity for ideal gases. $$k=\frac{9\gamma-5}{4}\frac{c_{\nu}}{\pi d^{2}}\sqrt{\...
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Is the pressure-gradient force that causes hydrostatic equilibrium entropic, contact, or both?

This question considers classical fluid mechanics, particularly the kinetic theory of gasses. In the simple one-dimensional gravitational setting, a fluid is in hydrostatic equilibrium if $\frac{dP}{...
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Unsure about whether CO2 significantly displaces Oxygen?

Caves can have high concentration of CO2 and cause suffocation. I thought it's because the denser CO2 displaces Oxygen in lower ground. However, in a typical daily condition where both are nearly ...
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Calculating the required volume of Helium to put in a weather balloon [closed]

Question I am working on a project where we will launch a weather balloon with some scientific instruments tied beneath the balloon. We fill the balloon with helium from tanks of compressed helium. ...
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Collecting gas over water -- is the textbook explanation wrong?

I was revising my chemistry and while doing a problem on collecting a gas over water, I felt like I disagreed with a part of their explanation. Firstly, an illustration to show how I think about ...
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Calculating time it takes to heat water in a microwave and the steam to evaporate

I am stuck on a question in my thermodynamics class. We have studied topics such as heat $Q$, entropy $S$, enthalpie $H$, etc. Bob puts a glass containing 500 grams of water in the microwave. Before ...
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Calculating volume of compressed hydrogen

I am trying to size a hydrogen gas storage cylinder. The parameters are as followed: storage pressure: 35 bar storage amount: 4kg of H2 Temperature: 20 degrees C Volume: ? So I converter 4kg of H2 to ...
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How does free energy change with the given change in a spring system containing an ideal gas?

When an ideal gas in contained in an expandable structure with a moving top fastened by two springs at the sides how does the free energy of the system change when the gas from outside the contraption ...
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Proof of pressure of ideal gas from first principles

Here's a question aimed at a deeper intuitive understanding of statistical physics and the theory of ideal gases, which has bothered me for quite a while. Assume a billiard table 2D. The table has ...
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How many balloons are possible to be bloated up? [closed]

A cylinder of volume $12 L$ is filled up with helium gas. Temperature and pressure of that cylinder are $281 K$ and $13 \ atm$ respectively. If one balloon can consume $1.4 L$ gas and pressure and ...
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A gas immersed in a higher-pressure gas: spherical shape?

I'm considering a bubble of gas of some arbitrary shape immersed in another gas of higher pressure. There is no gravity (and hence no buoyancy), the gases are ideal (so there are no attractive forces ...
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How to derive $ TV^{1-\gamma}$? I get $ \frac{T}{V^{1-\gamma}}$ [closed]

For an adiabatic process we have $dQ=0$, thus the first law gives: \begin{align} \mathrm{d}E &= \mathrm{d}W, \\ nC_V \mathrm{d}T &= - P\mathrm{d}V = - \frac{nRT}{V} \mathrm{d}V, \\ \frac{\...
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Doubts regarding work and pressure during adiabatic compression of a gas in a cylinder

So, I have doubts regarding the work done on the gas in this situation: Let's say I have an ideal gas inside an adiabatic cylinder fitted with a piston of area $A$. The piston has mass $M$. Outside ...
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Work done by a ideal gas

Say you have a big piston and it contains a ideal gas. say the gas expands ( we heated it). so, is the work done by the gas equal to the work done on the surrounding or the work done by the gas the ...
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Temperature of gas in accelerating container

This is a question whose different versions have been asked here a couple of times, but I don't find a clear answer. Does the temperature of a gas increase on accelerating the container? What ...
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Why does temperature remain constant in this case?

Consider two ideal gases of differing heat capacities. They occupy separate compartments of the same total volume. Assume their initial temperatures and that the amount of substance for both are the ...
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How to calculate integrals in Ideal Fermi Gas theory? [closed]

I'm having troubles solving integrals in the Ideal Fermi Gas theory. In particular the ones of the type: $$ \int\frac{d\vec{k}}{(2π)^3}θ(k_F − k)( \vec{k} \cdot \vec{q})^n$$ but I actually don't ...
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How comes, that my book states that internal energy is dependent on volume?

Currently I am reading in the 11 edition of Physical Chemistry, Atkins in the chapter 1st law of thermodynamics. A few pages ago I learned the following: Makes sense for now, as far as I know it ...
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The ideal gas equation is $pV=nRT$. Prove that $p=\frac{\rho RT}{M}$

The ideal gas equation is $$pV=nRT$$ Show that the pressure exerted by a fixed mass of gas is given by the equation $$p=\frac{\rho RT}{M}$$ Where $\rho$ is the density of the gas and $M$ is the mass ...
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How do I determine the relationship between initial and final volume in this case?

Some total volume contains two compartments separated by a wall that allows for mechanical and thermal interaction, each compartment having a different amount of an ideal gas. For the initial ...
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How to predict deviation from ideal gas behaviour?

Molar masses of H2, N2, CO2, and NH3 are 2g, 28g, 44g, and 17g and respectively. The gases deviate from ideal behavior in the following order: $$\require{mhchem} \ce{H2<N2<CO2<NH3}$$ ...

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