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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4 votes
2 answers
76 views

Dalton's law clarification

I'm looking at Elements of Physical Chemistry by Atkins and de Paula. In section 1A.3, they state Dalton's law as The pressure exerted by a mixture of perfect gases is the sum of the pressures that ...
-2 votes
2 answers
56 views

How to define percentage by volume for ideal gas and Why percentage by volume is equal to percentage by mole? [closed]

Why do we define percentage by volume for an ideal gas in a closed container in spite of that we know the ideal gas will occupy the volume of the whole container? I have seen many people who prove ...
-4 votes
1 answer
48 views

What is the Volume occupied by gas at extreme or limiting conditions of volume? [closed]

We know that 1 Mole of an Ideal Gas occupies 22.4 L at STP. [real gases also are also close to this volume , even tho there might be deviation, for this experiment let's take both to be same] But it'...
1 vote
1 answer
52 views

Henry’s Law Pressure Limitations

I’m trying to decide if I can I expect Henry’s Law to be an effective way to estimate how the solubility of a gas in a liquid solution will change if I decrease the pressure. I know Henry’s is best ...
0 votes
0 answers
33 views

Does KE(avg) stay the same for ideal gas if the PV value changes?

We know that Kinetic Energy is a function of Temperature for an ideal gas. So KE (1 Mole of gas) = (3/2)RT = (3/2)PV. So it's said that even if P or V change their change will counteract the other (...
-1 votes
1 answer
96 views

Can we calculate final temperature of two gases in thermal contact? [closed]

This is a question from IIT-JEE - ADVANCE 2018 A closed tank has two compartments A and B, both filled with oxygen (assumed to be ideal gas). The partition separating the two compartments is fixed ...
0 votes
2 answers
114 views

Why do we subtract the volume correction term in the van der Waals gas equation [duplicate]

The following equation is valid for ideal gasses $$pV=nRT$$ Please mind the following notation, any parameter that is related to an ideal gas would be denoted with a subscript $i$ and anything related ...
0 votes
0 answers
44 views

Use the first law of thermodynamics to derive the pressure as a function of T, U, V and N

I am struggling with a thermodynamics question given $$S(U,V,N)=C_VNK_\mathrm b\ln U/U_0+NK_\mathrm b\ln V/V_0$$ (where $U_0$ and $V_0$ are the reference energies and volumes) and the first law of ...
2 votes
1 answer
119 views

Molecular collisions in an ideal gas

(The equation of ideal gas is $pV=NRT$. If p = 1 atm, N = 1 mole, T = 0°K, and R = gas constant, then volume = V = zero. Hence, the volume of an individual molecule of ideal gas is zero). An ...
8 votes
1 answer
430 views

Confusion in Van der Waals Equation

I understand that the behavior of ideal gases deviates largely from that of real gases in terms of pressure exerted by the gas molecules on the container in which it is present, space available for ...
0 votes
1 answer
71 views

Gibbs Free Energy of Ideal Gas in Carnot Cycle

Let's just say we have 2 moles of monoatomic (maybe helium) ideal gas that is doing a Carnot Cycle with reservoir temperature of 300 and 750 K. Now, here's a simple question, what is the Gibb Free ...
1 vote
0 answers
49 views

What is the necessary and sufficient condition for a mixture to be ideal?

I am trying to understand some concepts from solution thermodynamics related to ideal mixtures and fugacity. My main question is what is the necessary and sufficient condition for a mixture to be an ...
0 votes
0 answers
31 views

How do I calculate the temperature change in a gaseous reaction?

So, with $\pu{3 mol}$ of $\ce{H2}$ and $\pu{3 mol}$ of $\ce{Cl2}$ and given the reaction $\ce{H2(g) + Cl2(g) -> 2 HCl(g)}$ with $\Delta H=\pu{-184.6 kJ/mol}$, I am supposed to calculate the work ...
1 vote
1 answer
137 views

If Graham's law doesn't apply to the ammonia and hydrogen chloride diffusion in a glass tube demonstration, is there a law that does?

A comment below What exactly are "white fumes" and why does holding a bottle of ammonia (conc) next to a bottle of HCl (conc) make them? links to The Royal Society Of Chemistry video ...
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-1 votes
1 answer
85 views

Why is Molar Mass of a gas twice the vapour density?

I've seen this relation at a number of places, and I can't get why. A simple Google search doesn't give me a simple answer either. Also, are there any exceptions/conditions for this relation to be ...
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4 votes
0 answers
58 views

Why does the factor of ⅔ come in when we calculate net flux due to diffusion for an ideal gas

As per Atkins' Physical Chemistry (11E) Pg:694. We arrive at a crude estimate for the net flux through an imaginary flux plane. We find it to be $$J_{z}=-\frac{1}{2}v_{mean}\lambda(\frac{d\mathcal{N}}{...
0 votes
0 answers
49 views

Energy change of isentropic expansion of ideal gas

I'm trying to get a better grasp on dealing with different processes thermodynamic, and this one is giving me trouble. The differential of energy is given by $$dU= \delta Q + \delta W~.$$ I'm ...
1 vote
0 answers
105 views

Why 3 and not 6 in U = 3/2RT from the equation for the internal energy of an ideal gas?

Internal energy of an ideal monatomic gas is $$U=\frac{3}{2}RT.\tag{1}$$ While I understand the derivation, I do not understand why we multiply by $3$ rather than by $6.$ According to Khan Academy ...
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0 votes
0 answers
32 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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0 votes
0 answers
14 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 ...
2 votes
0 answers
84 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 $...
0 votes
0 answers
67 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\...
1 vote
1 answer
69 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 ...
2 votes
1 answer
215 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:$$R\propto1/\sqrt T$$ ...
-1 votes
1 answer
696 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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2 votes
1 answer
115 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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1 vote
0 answers
75 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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-1 votes
1 answer
206 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 ...
-1 votes
1 answer
71 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 ...
1 vote
3 answers
103 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 ...
0 votes
1 answer
103 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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3 votes
0 answers
60 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 ...
-2 votes
1 answer
98 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 ...
0 votes
1 answer
168 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 ...
4 votes
2 answers
1k 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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-1 votes
1 answer
72 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 ...
0 votes
0 answers
59 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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1 vote
2 answers
117 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 ...
0 votes
2 answers
311 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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0 votes
1 answer
213 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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13 votes
4 answers
4k 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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2 votes
1 answer
107 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 ...
0 votes
1 answer
372 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, $x$, ...
2 votes
1 answer
124 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). ...
1 vote
1 answer
373 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 ...
0 votes
1 answer
84 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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0 votes
0 answers
33 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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2 votes
1 answer
73 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 ...
4 votes
0 answers
103 views

How much energy is required to operate a Sabatier reactor?

I am trying to model some industrial processes and having a hard time finding information about the Sabatier reaction. The Sabatier reaction combines $\ce{CO2}$ (and possibly $\ce{CO}$) with $\ce{H2}$ ...
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2 votes
1 answer
128 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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