Questions tagged [kinetic-theory-of-gases]
Questions about the assumptions, equations, and properties of gases derived from kinetic theory. For questions pertaining to rates of reactions, please use the kinetics tag instead.
151
questions
-3
votes
2
answers
107
views
When a gas is expanded, why doesn't the number of moles of a gas increase despite it's volume increasing (doubt in JEE sample question) [closed]
This question might be elementary, but it is genuine. I realise that some users might downvote the question for being so basic, but I urge them to be a little merciful, and help out a confused high ...
- 95
-2
votes
1
answer
244
views
Can a heated gas leave a container through downwards direction?
If I have a flask full of heated gas, with an opening at the BOTTOM of the flask and connected pipe facing downwards, can the heated gas can leave the flask through that opening?
And for an alternate ...
1
vote
1
answer
93
views
In collision theory why we multiply collision frequency by N/2?
In kinetic theory of gases we know that the average number of collisions, $N_\mathrm{col}$, is given by
$$N_\mathrm{col} = \sqrt{2\pi\sigma^2 \overline{v}_\mathrm{rel}}\ N $$
where $N$ is the number ...
0
votes
1
answer
70
views
Kinetic energy change in reaction
If we consider a reaction occurring at constant pressure and temperature , we know that enthalpy represent the net heat released or absorbed by the system and internal energy accounts for both heat ...
6
votes
1
answer
196
views
Non-Arrhenius temperature dependence of bimolecular reaction rates at very high temperatures
Once I have read that in some cases bimolecular reactions can exhibit a maximum as a function of temperature due to the short lifetime of the activated complex at very high temperatures.
At low ...
- 163
0
votes
1
answer
103
views
RMS Speed of Gases as Standard Deviation
In kinetic molecular theory, the average velocity of gas particle is zero since the molecule move in different directions, and the overall effect is zero. Howeever, you can calculate different speeds.
...
- 173
0
votes
1
answer
101
views
Validly of the equation, du= nCv dt, for an adiabatic process
In an adiabatic process, there is no heat exchange, hence, $Q=0$.
The equation $\mathrm dU=nC_V\,\mathrm dT$ is valid for every type of process given the gas is ideal, where $C_V$ is heat at constant ...
- 1
3
votes
0
answers
96
views
Probability distribution for the momentum of a particle undergoing a collision?
Background
I haven't seen this mauver done before but let's say, I have a thermal gas and I have a molecule with momentum $\vec p$. It undergoes a collision and now has momentum $\vec P$.
Now, due to ...
- 159
3
votes
1
answer
158
views
Is it Rigorous to Derive the Arrhenius Exponential Term from the Boltzmann Distribution?
The Boltzmann distribution is a probability density function which expresses the probability of finding a particle in an energy state $\epsilon$ while in thermal equilibrium given a specific ...
1
vote
1
answer
184
views
Why is the isenthalpic condition required in the Joule–Thomson effect?
I have been struggling to understand how the molecules behave during the Joule–Thomson effect. I would love to get some help on this concept. Here is what I got so far.
Under adiabatic and isenthalpic ...
- 11
-2
votes
1
answer
293
views
Average molecular distance between hydrogen gas [closed]
The whole question goes like this:
Calculate the de Broglie wavelength of hydrogen molecule at 300K (Take the translational energy to be 1.5kT) Compare this to the average intermolecular spacing for ...
- 15
2
votes
0
answers
78
views
What is the average collision duration?
So I've been trying to figure this out: What is the average collision duration of a gas in terms of macroscopic variables?
What I have figured out. Whenever two molecules collide they must reach a ...
- 159
0
votes
0
answers
43
views
What ideal gas behavior is observed by a real gas that observes Boyle's law (at Boyle's temperature)?
Boyle's temperature is a constant for a particular gas. At this temperature the real gas behaves ideally.
So, does the real gas only follow Boyle's law at this temperature, or are all the gas laws ...
- 11
-1
votes
2
answers
514
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 ...
8
votes
1
answer
615
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 ...
- 111
1
vote
1
answer
195
views
Question on Thermodynamics from a recently conducted Examination
This is a question from the recently conducted JEE Main exam (in India). I had solved it myself, but found the answer to be incorrect. Here's the question.
Here is how I solved it:
$\Delta H = \pu{41....
- 556
-2
votes
1
answer
38
views
Isolation is a Consequence of Definition [closed]
Let's consider a ballon, such that it has an adiabatic wall, and there is no exchange of heat with the surroundings. Now, let the balloon wall be completely impermeable to the movement of matter ...
- 795
0
votes
1
answer
515
views
Cubic nature of van der Waals' gas equation
$V_m^3-\dfrac{RT+bP}{P}V_m^2+\dfrac{a}{P}V_m-\dfrac{ab}{P}=0$
So, At $T<T_c$ the above equation has three real roots say $V_1,V_2,V_3$, my doubt is what does this mean physically because for some ...
- 129
0
votes
1
answer
132
views
According to Maxwell-Boltzmann distribution, what is probability distribution function proportional to?
If, according to the Maxwell-Boltzmann distribution
$${f(v)}\propto\exp\left(-\frac{\varepsilon}{kT}\right),\tag{1}$$
which is the equation from which the whole final equation is derived, then why is ...
1
vote
1
answer
131
views
Why is the value of $A$, in the expression for Boltzmann's distribution of speeds, not directly calculated?
I've read the proof for the expression for Boltzmann's distribution of speeds on this site. There, $f(v)$ is first factorized into $f(v_x)$, $f(v_y)$ and $f(v_z)$ and $A$ into $A_x$, $A_y$ and $A_z$. ...
1
vote
1
answer
251
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 ...
- 5,742
4
votes
0
answers
69
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 $$J_{z}=-\frac{1}{2}v_{mean}\lambda(\frac{d\mathcal{N}}{...
- 71
2
votes
1
answer
542
views
Relation between concentration and activation energy
Will increasing the concentration of the reactants in a chemical reaction increase the proportion of molecules with an energy greater than the activation energy $E_\mathrm{a}$?
It seems to me that the ...
- 21
0
votes
1
answer
107
views
What is heat bath here?
At the beginning $\pu{1 mol}$ of air is compressed to $\pu{3 atm}$ at a of temperature $\pu{523 K}$. After a random process, the pressure of the air equates to $\pu{1 bar}$ at a temperature of $\pu{...
- 193
1
vote
1
answer
128
views
Density gradient vs. entropy of mixing
I was wondering how real gases would behave when they are released into a closed container with fixed volume.
For example, suppose we use chlorine and nitrogen gas. Obviously, chlorine has a higher ...
- 276
0
votes
1
answer
992
views
Degrees of freedom of a molecule of N atoms [closed]
Apparently a molecule of N atoms has 3N degrees of freedom. How?
Shouldn't it be dependent on the structure of the molecule? How exactly do we derive this?
- 411
3
votes
2
answers
2k
views
Is air made 100% from atoms?
I know air is made up of roughly 78% nitrogen, 20% oxygen, etc.. but I would like to know what percentage of air is just space and has no atoms at all.
- 163
0
votes
1
answer
206
views
Confusion regarding continuity of state
I was reading about Andrew's isotherms and about the continuity of state.
What confused me was the continuous conversion of gaseous state to liquid state.
Now my textbook says that by keeping volume ...
- 79
3
votes
0
answers
434
views
Formula for collision frequency and mean free path
We were studying collision frequency and mean free path today, and in it, we got the equations of collision frequency as:
$$Z=\sqrt 2 \pi \sigma^2v_{rms}N$$
where $N$ is the number density, equal to $...
0
votes
0
answers
79
views
Is the value for the Boltzmann Constant different in 2D?
So I'm simulating some hard sphere collisions and want to determine the Boltzmann constant in two dimension, using the equation
$$PA=Nk_BT$$
where $A=\pi R^2_{container}$, $P=(averageImpulse/time)/(2\...
- 139
1
vote
0
answers
159
views
Virial expansion of real gas equation and volume work
Hi I am currently working on a thermodynamics problem, and it asks me to first find the volume work done on a gas that behaves like the simplified Dieterici equation (see below) predicts on isothermal ...
- 23
2
votes
0
answers
60
views
Is this a valid interpretation of the Mean relative speed between two (Maxwell-Boltzmann) species?
In textbooks, the collision frequency $Z_{ab}$ is always given as something like:
$$Z_{ab} = n_an_b\sigma_{ab} \Bigg(\frac{8 k T}{\pi \mu}\Bigg)^{1/2}= n_an_b\sigma_{ab} \bar{C}_{rel}$$
where the ...
- 21
3
votes
0
answers
183
views
What exactly is a photon gas?
I came upon this question in a JEE Advanced mock test online:
The number of photons of wavelength $\lambda$ required to achieve pressure $P$ in an empty cubical box of edge length $l$ is given by $\...
- 317
9
votes
3
answers
1k
views
Comparing van der Waals constant for gases
How can I compare the van der Waals constant $a$ (the liquefication constant) for different compounds based on my knowledge of bonding in the compound? Let's pick the following sample set:
$$
\...
- 307
0
votes
0
answers
56
views
Which formula for kinetic energy of 1 mol of a gas is universally applicable? [duplicate]
I have read 2 formulas for kinetic energy of 1 mol of gas - 3/2 RT and 1/2fRT . But if I equate them then f comes out to be 3 . But f is different of mono, di, polyatomic gases . Where am I wrong in ...
- 129
-2
votes
1
answer
103
views
Graham's Law of Effusion when Looking at Samples with Equal Mass?
So, I had a question on a chemistry test about two gas samples, one of O2 and one of N2, that had equal masses. We were given the time of effusion for the sample of N2 and then asked to calculate the ...
1
vote
2
answers
1k
views
Change in Enthalpy in Free Expansion of Ideal and Real gas against Vacuum
By free expansion, I am referring to gas allowed to expand freely against vacuum in a Joule Expansion.
If gas is ideal then change in Internal Energy '∆U' and change in Enthalpy '∆H' is zero.
(By ∆H = ...
- 199
3
votes
1
answer
165
views
Question regarding $Z$ (Compressibility factor)
Oh! This problem has been bugging me for a long time. According to Wikipedia, the Compressibility factor $Z$ is defined as the ratio of the volume occupied by a real gas to the volume occupied by an ...
8
votes
5
answers
2k
views
Is the average kinetic energy of evaporating water molecules (at room temperature) equivalent to the average kinetic energy of boiling water?
Purpose:
On new year's eve, after a splendid red and an assortment of sumptuous repasts, I made a bold remark which, on further consideration, may turn out to be incorrect. Unless! Unless I can ...
- 83
-1
votes
2
answers
458
views
Why are some liquids hotter than room temperature gases if liquid and solid molecules move more slowly than gases? [closed]
We learned in school that state change is a matter of molecules moving faster and faster. And we learned "heat em up, speed em up, spread em out". Why then can some liquids have higher ...
- 783
-1
votes
2
answers
2k
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 ...
- 117
1
vote
1
answer
215
views
Ideal gas equation derivation proportionality [duplicate]
While deriving the Ideal gas Equation using Boyle's, Charles', and Avogadro Laws,
how are each of the laws, which have different proportionality constants and different quantities as constant combined?...
- 19
1
vote
1
answer
1k
views
What gas law is involved when your ears "pop" when you are on a plane high in the air? [closed]
When you are up in the air, the air pressure decreases and the altitude increases. What gas law is involved in the situation wherein your ears "pop" because of the difference in pressure.
- 19
1
vote
1
answer
781
views
Adiabatic expansion of gas
If a real gas is adiabatically expanded against constant pressure, then which of the following will definitely increase?
Compressibility factor (Z) or Entropy (S)
Correct answer: Entropy
My answer: ...
- 357
-1
votes
1
answer
148
views
Maxwell's distribution function for mixture of ideal gases
I came across a question demanding relations between the individual distribution functions $f_n$ for the $n$th gas, and the overall $f$ for the entire mixture.
I believe there is no simple way to ...
- 345
4
votes
1
answer
175
views
Rigorous reason behind internal energy change being zero while mixing
A container is divided in two parts: one part contains oxygen gas $(n_1$ moles, at temperature $T_1)$ and the other part contains helium gas $(n_2$ moles, at temperature $T_2).$ The partition ...
- 379
0
votes
2
answers
77
views
Crossing at critical temperature of a gas
This is written in the book 'Treatise on Thermodynamics' by Max Plank-
the crossing of the critical temperature at any pressure other than the critical pressure differs in no way from the crossing of ...
- 57
0
votes
0
answers
72
views
Calculating force and pressure of an ideal gas on a wall [duplicate]
The text below is from a discussion on ideal gases and the kinetic theory of gases:
After the collision the molecule must travel a distance $l$ to the
opposite wall, and then back across this same ...
- 69
0
votes
1
answer
103
views
Relative humidity at constant temperatures [closed]
It’s known that Relative humidity = (water pressure in a certain volume/ saturated water pressure in the same volume)* 100% “at the same temperature”
So my question is why does the amount of water ...
- 11
0
votes
0
answers
24
views
Energy and impurities balance for adsorption with a fixed bed (with description)?
Do you have any suggestion where to look for a source of information about energy and impurities (component) balance for adsorption of mixture CO2/H2O in fixed bed?
I have looked into many articles /...
- 133