Questions tagged [ideal-gas]

For questions about the ideal gas law or gases which can be well approximated as an ideal gas.

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12 views

Vapor pressure in closed systems (2 and multiple components)

Hi there I am currently struggling to understand how vapor/liquid systems work in general. Specifically, I have two qualitative questions. Suppose we had a closed system, half of it filled with just ...
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21 views

Calculation of dry air density without relative humidity

I would like to estimate the density of dry air at different temperatures and constant pressure (1 bar) just using the densities of nitrogen (79%) and oxygen (21%). I consider the amount of other ...
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8 views

Deviation from Ideal Gas Law: Nonzero volume of a gas (Don't understand how this explains compressibilities>1)

The ideal gase law (PV=nRT) assumes that the volume of a gas is negligible. We know this is not a valid assumption for real gases, and this is particularly pronounced when the container that the gas ...
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53 views

Formula for collision frequency and mean free path

We were studying collision frequency and mean free path today, and in it, we got the equations of collision frequency as: $$Z=\sqrt 2 \pi \sigma^2v_{rms}N$$ where $N$ is the number density, equal to $...
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20 views

Why is my P-T gradient decreasing for increasing radius of spheres when it should be increasing? [closed]

Why is my P-T gradient decreasing for increasing radius of spheres when it should be increasing? I'm simulating some hard sphere collisions with $Radius_{container}=10,$ and varying pressure and ...
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63 views

Is the value for the Boltzmann Constant different in 2D?

So I'm simulating some hard sphere collisions and want to determine the Boltzmann constant in two dimension, using the equation $$PA=Nk_BT$$ where $A=\pi R^2_{container}$, $P=(averageImpulse/time)/(2\...
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1answer
40 views

What happens when $V=Nb$ in the Van der Waals equation (divergent)?

The VdW equation: $$\left(P+a\left(\frac{N^2}{V^2}\right) \right)\left(V-Nb\right)=Nk_BT$$ when the intermolecular forces are zero $a=0$, so $P=\frac{Nk_BT}{V-Nb}$ which diverges at $V=Nb$ for fixed ...
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1answer
72 views

Relation of temperature to effusion and diffusion [duplicate]

We were studying Graham's Law today and its dependence on Temperature, Pressure, Area, etc. However, our teacher said that, for diffusion: $$R \propto \sqrt T$$ and for effusion:$$R\propto1/\sqrt T$$ ...
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1answer
117 views

How can I calculate the density of a gas mixture using the ideal gas?

I am trying to calculate the density of the ideal gas mixture given the following data: The gases are helium and oxygen. There are $\pu{8 g}$ $\ce{He}$ and $\pu{16 g}$ $\ce{O2}$. The temperature is $\...
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1answer
59 views

Converse of ΔU = 0 for isothermal processes: is it true?

For an ideal gas undergoing an isothermal process $\Delta U = 0.$ But is the converse true? Let's say, $\Delta U$ for an ideal gas is zero. Is its temperature constant then? Can we say that it's ...
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74 views

Reversible compression and proving relation with state function

I am currently working on a question I am having problems with. I tried to solve it, but to no avail; it states that this expression is always valid for any three-variable dependent function: It ...
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1answer
43 views

How do I find the volume of a gas when the pressure and temperature changes, given the original volume? [closed]

I am a sophomore in high school, just started honors chemistry this year, and I'm having trouble figuring out what formula to use for this question, and how exactly to do so: If a gas has an original ...
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1answer
67 views

Ideal Gas Equation Extreme Case [closed]

I have recently learned about the Ideal Gas Equation and I have this doubt.....suppose I am in a closed container filled with a gas of fixed volume and definite amount of moles. I am assuming myself ...
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3answers
96 views

Does the amount of a gas increase with pressure? [closed]

The graph of $pV/(RT)$ shows that different gases deviate differently from ideal gas behaviour and that the value of $pV/(RT)$ changes as pressure increases. My question is, if $pV/(RT) = n$ or amount ...
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1answer
43 views

Calculation of the mass of N2 in the container

Two vessels of equal volumes are connected to each other by a valve of negligible volume. One vessel containing $0.1$ mole $\ce {N_2}(g)$ and $0.05$ mole $\ce {I_2}(s)$ at temperature $T_1$. The other ...
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50 views

About Real Gas and Ideal Gas - Select the correct statement(s):

Select the correct statement(s): At Boyle's temperature a real gas behaves like an ideal gas at low pressure. Above critical conditions, a real gas behaves like an ideal gas. At high pressure van der ...
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1answer
94 views

Looking for gas or liquid for story research

I am working on a story for adaptation into animation. Main lead is a chemist in a traditional fantasy setting. The chemist uses her own compound to battle using fire or explosions. I love the ...
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1answer
78 views

How to compute the work Done in an adiabatic irreversible expansion?

The question is as follows What is the magnitude of work performed by one mole of an ideal gas when its volume increases eight times in an irreversible adiabatic expansion if initial temperature of ...
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2answers
385 views

Why is the enthalpy change of an ideal gas a function only of temperature?

While teaching us thermodynamics our chemistry teacher told us that enthalpy change of a real gas is a function of temperature, pressure etc. but the enthalpy change of an ideal gas is only a function ...
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1answer
34 views

Why do we use external pressure to calculate work done by a gas in case of compression instead of using internal pressure? [closed]

According to formula work done is (Resisting pressure X dV)? Then in case of compression, isn't the resisting force is internal Pressure? Then why we the formula for compression is same as expansion ...
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40 views

How does volume change as a piston separating two compartments of a thermally insulated container moves to reach thermodynamic equilibrium?

The situation is a thermally insulated container divided into two compartments, which are separated by a diathermic piston. Initially, the left compartment has a volume (V1) of 2L, and a temperature ...
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2answers
88 views

Why does CO2 diffuse out of a cylinder in the absence of a pressure difference?

Suppose I have a thermally insulated cylinder containing carbon dioxide (assuming it is ideal) at 1 atm pressure(atmospheric pressure is 1 atm). Now let's consider two cases: CASE-1: I cut open the ...
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2answers
217 views

Compressibility factor and deviation from ideality

Consider these statements : At Boyle point, real gases show ideal behaviour. Above the Boyle point, real gases show positive deviation from ideality (forces of attraction between the particles are ...
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1answer
64 views

What is the density of nitrogen at standard conditions?

I find diverging answers to what the density of nitrogen at standard conditions is. By standard conditions I mean T=273.15 K and P=1 atm (=1.01325 bar). Different sources state: Wikipedia : 1.2506 g/...
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4answers
3k views

What is the physical significance of the universal gas constant R?

While studying work done in isothermal processes I was told that the universal gas constant $R$ is the work done by the gas per mole per kelvin. I am sure I am missing something basic but I didn't ...
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1answer
72 views

Number of possible microscopic states and their probabilities

I'm having trouble with the following problem: Boltzmann defined entropy as a measure of the number of possible microscopic states of a system, $W$, as: ${S = k_BlnW}$ Here, $k_B$ is the Boltzmann ...
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65 views

Complex formation in water and Henry's law

I've been trying to solve the following problem for a while now. Consider a mixture of two different gases ($A$ and $B$) for which Henry's law holds. When gas molecules $A$ and $B$ do not interact ...
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1answer
102 views

Dissolution of CO2 in water

The following question has troubled me for a while. For gases that are slightly soluble in water, there is a proportional relationship between the partial pressure, $P$, and the mole fraction, $x$, ...
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1answer
69 views

Partial pressure of gases in a container with a piston

I've been having problems with the following problem. Figure 1. A container with a piston like that shown in Figure 1 is filled with $0.10$ $mol$ of Ar and $1.00$ $mol$ of water (liquid and vapor). ...
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1answer
104 views

Finding the mole fraction of nitrogen in a mixture of nitrogen and oxygen

Question The density of a mixture of Nitrogen and Oxygen is $\pu{4.7 g L-1}$. Its given that $P = \pu{4 atm}$, and that $T = \pu{298 K}$. Assuming both gasses are ideal gasses, what is the molar ...
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1answer
71 views

Confusion in solubility expressions in Henry's Law

While reading about Henry's law and solubility I frequently come across two relations: $C = k_{h}P$ (c = concentration of a dissolved gas) $P = k_{h}x$ (x = solubility/mole_fraction) What is the ...
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26 views

How much energy is required to liquify oxygen?

Does anyone know where I can find some documentation of a real-world liquification process, and the energy costs? I can calculate the heat that must be removed from O2 gas to get to liquid, but how ...
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1answer
71 views

How can change in Enthalpy for a reaction be written like this?

If a gas expands in a container with constant external pressure then: $W=-P_{ext}\Delta V$ Instead of $P_{ext}$ if we use $P_{int}$ then we will not get the same value because $P_{int}$ is constantly ...
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51 views

How much energy is required to operate a Sabatier Reactor?

I'm trying to model some industrial processes and having a hard time finding information about the Sabatier reaction. The sabatier reaction combines CO2 (and possibly CO) with H2 to produce H2O and ...
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1answer
106 views

Find gas pressures of injection knowing mixture pressure without knowing volume

Let's say we have a gas 1 moving inside a pipe (we don't know the geometry) at mass flow rate $Q_1$ and temperature $T_1.$ We inject a gas 2 at some point inside the pipe with gas 1 at mass flow rate $...
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3answers
311 views

Specific Heats for Non-Constant Processes

Why can the specific heat at constant Pressure ($C_p$) be used to calculate the change in enthalpy as $\text{d}H = C_p\text{d}T\newcommand{\d}{\text{d}}$ for processes that are not even at constant ...
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1answer
104 views

Volume of ideal gas molecule [closed]

Is there any reason as to why we assume the volume of ideal gas to be negligible in comparison to the container? What is the underlying reason to assume that the ideal gas molecules are point ...
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1answer
49 views

How does an irreversible process maintain internal energy while dissipating excess heat? [closed]

From my understanding, if you were to look at a pressure-volume graph of a reversible, isothermal expansion, the area under it would represent reversible work. Similarly, if you were to graph an ...
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1answer
267 views

How does one prove Avogadro's law from Gay-Lussac's?

To understand Gay-Lussac's law, Amedeo Avogadro said In equal volumes of air under constant temperature and pressure, there are equal number of atoms (or molecules). Let's take a hydrogen and an ...
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1answer
45 views

Particules speed in ideal gasses [closed]

According to Graham's law, we can calculate de average speed of gasses by using the formula $$v^2=\frac{3RT}{M}$$ I tried to use this simulation and got these data by keeping same particles amount and ...
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1answer
72 views

Work done by system of ideal gas in isobaric expansion

Consider a system of ideal gas in a container with piston and the isobaric expansion of gas takes place. As the process is isobaric, so initially the pressure of gas is equal to atmospheric pressure ...
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1answer
35 views

Consider difference of pressures as weight of piston [closed]

Let us say there is a container with two ideal gases in it divided by a piston.Volume of ideal below the piston is 2L and above is 8L.Total volume of container is 10L. n of both is 1 mole and T is 300 ...
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79 views

Volume of compressed helium gas needed for FE test on ball valves

I'm currently doing a case study to find out the exact volume of helium gas required for FE tests on ball valves regards to the valves' volume and pressure class and the number of helium tanks needed ...
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1answer
630 views

Will entropy increase in adiabatic expansion? [closed]

The formula for entropy change states that change in entropy is not possible if heat change is nil. ∆S=∆Q/T But what if we adiabatically expand a gas? Won't the molecules get more space to vibrate in, ...
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51 views

Why is the concentration term in van der Waals correction for ideal gas squared? [duplicate]

In van der Waals correction for ideal gas equation, the pressure term has a correction where concentration term is squared. I saw derivations for this and they say that the concentration is squared ...
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1answer
112 views

interconverting Van Der Waal's equation for real gases from number of molecules to density

I want to ask a question about Van Der Waal's equation for real gases. I was shown the following formula for real gases (VDW) which accounts for the liquification of water vapour which is not possible ...
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2answers
1k views

Under what conditions does Real Gases show Ideal Behaviour? [closed]

MY textbook says : Real gases show Ideal Behavior under low pressure ,high temperature. So I wanted to know what happens to real gases at high pressure ,low pressure Do they also show ideal behavior ...
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0answers
91 views

Why is vapor pressure constant at boiling point?

At non-boiling point, I understand that when you add heat, temperature increases and also the amount of gas increases, so by using $PV=nRT$ at constant volume, the increase in $n$ and $T$ would ...
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1answer
154 views

Specific Heat Ratio for a perfect gas mixture

I am reading Rocket Propulsion Elements by George P. Sutton & Oscar Biblarz, 9th Edition. In the fifth chapter, I was introduce to the specific heat ratio k for the perfect gas mixture, Eq. 5-7. ...
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1answer
54 views

describing in words a primitive heated water vapor lift

The primitive lift illustrated in the left hand side of the following figure operates using heated water vapor ("gas") that pushes on a sealed piston. During its operation, the vapor ...