# 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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### Why does an isothermal expansion require more energy?

Let's say we have two completely identical cylinders of some ideal gas (same $P,V,T,n$, etc...), and we just want to double each one's volume. First Cylinder The first cylinder undergoes a simple ...
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### Calculation of humidity ratio by vapor partial pressure

I've been looking around for a way to calculate the humidity ratio by the partial vapor pressure and the atmospheric pressure of the environment. I found a procedure for such calculation on ...
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### $pV=nRT$: Is this rudimentary proof correct in its assumptions?

I had a quick check in the help page (there wasn't much info on these types of questions). It looks to be allowed I know this doesn't technically constitute as proof (since it assumes other equations ...
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### Why do some gases have fewer degrees of freedom at same temperature?

I am trying to understand the degres of freedom for gases. Air has 5 degrees of freedom at room temperature but why does Argon, $Ar$ have 3 degrees of freedom while $O_2$ has 5 at the same temperature ...
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### How long does it take for 1 mole $H_2$ at STP to diffuse to a density of one $H_2$ molecule per $m^3$ in interstellar space?

One can read here: The molar volume, or volume of one mole of gas, depends on pressure and temperature and is 22.4 liters - at 0 °C (273.15 K) and 1 atm (101325 Pa), or STP (Standard Temperature and ...
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### Can you reach higher efficiencies of the Otto cycle by changing the sequence slightly?

If we take the common Otto cycle we have two isochoric and two adiabatic processes, plus exhaust & intake stroke. Would it be more efficient to do the following: Instead of cutting off the ...
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### Calculating Temperature of boiling water using constant volume gas thermometer

Why different gases give slightly different temperature at same pressure in a constant volume gas thermometer? My book says we should lower the amount of gas in the thermometer to get perfect result
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### Pressure - temperature relationship in constant volume with high temperature and density

For the coating, it is necessary to pour 40 ml of liquid in a closed container with a volume of 80 ml and place it in an oven at a temperature of 200-300 °C .My question is whether, given the high ...
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### Understanding the physical process that takes place in this problem about ideal gases

I am faced with the following problem: A cylinder containing $n_{0} = 4$ moles of ideal monoatomic gas, at temperature $T_{0} = 280\ \mathrm{K}$ and pressure $p_{0} = 150\ \mathrm{kPa}$, is equipped ...
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### Small $N$ ideal gas entropy and extensive entropy: Finite $N$ Sackur-Tetrode and Gibbs Paradox

In the standard derivation for Sackur-Tetrode, the accounting for the indistinguishability of ideal gas molecules adds an extra factor of $N!$ in the partition function. This is usually approximated ...
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### How to derive that $\delta w = - PdV$?

I am not understanding how to derive this particular expression, which relates the inexact differential of work to the exact differential of volume, $$\delta w = -PdV$$ My attempt: Reversible work ...
354 views