Tagged Questions
0
votes
0answers
47 views
Air pressure in balloon
I have to calculate the air pressure inside of an hot air balloon. After some searching I found out that I can use the ideal gas law: PV = nRT (from Wikipedia)
So to get the pressure in the balloon I ...
-1
votes
0answers
23 views
Finding rms velocity in isothermal process [closed]
I think none of these options are correct, I just need someone to confirm. Please, as no option is matching with $V_{rms}$.
2
votes
2answers
44 views
What are the units of these virial coefficients?
I'm reading some papers for calculating the vapor pressure of alkali metals as a function of temperature, and I've come across some familiar-looking virial expansions, but when I tried to work out the ...
0
votes
2answers
78 views
Temperature change inside pressure chamber
Let's say there is a pressure chamber with some sort of sample / specimen (e.g. protein crystal) in it. Now I apply a certain amount of gas pressure, e.g. 10 or 20 atm. Let's say I use xenon as a gas. ...
0
votes
1answer
56 views
In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Say I have an ideal gas that has a known $P_1$, $P_2$, $T_1$, and $T_2$ undergoing a reversible adiabatic process. I want to find the work done so I must use $PV = RT$ to get the change in $V$, so ...
0
votes
1answer
124 views
Ideal gas temperature and pressure gradients?
Consider an ideal gas in a $d\times d\times L$ box with the $L$ dimension in the $x$-direction. Suppose that the opposite $d\times d$ sides of the box are held at temperatures $T_1$ and $T_2$ with ...
3
votes
2answers
177 views
Ideal gas concentration under temperature gradient
I'm trying to calculate the concentration of an ideal gas in an adiabatic container as a function of position where the top and bottom plates of the container are fixed at temperatures $T_1$ and ...
3
votes
2answers
136 views
With ideal gases, varying quantity of moles, and having a constant volume how do temperature and pressure behave?
I'm trying to build a simulation of gases so I ended-up trying to use law of ideal gases ($PV = nRT$).
In my scenario:
volume is constant ($V=1\rm{m}^3$);
a known quantity of moles are being added ...
3
votes
3answers
184 views
Understanding mathematically the free expansion process of an ideal gas
I'm trying to understand mathematically that for the free expansion of an ideal gas the internal energy $E$ just depends on temperature $T$ and not volume $V$.
In the free expansion process the ...
0
votes
0answers
93 views
Is it possible to add heat to a monoatomic ideal gas without increasing entropy? [closed]
The Sackur-Tetrode equation expresses the entropy of a monoatomic ideal gas:
[Equation from HyperPhysics]
0
votes
0answers
59 views
Using thermodynamics and Kinematics together to solve a parachuter problem?
I need to find a parachutist's displacement after a given height (nearly 37000m) and at a given latitude. I have his mass, area, parachute area, drop height, parachute deployment height, data about ...
0
votes
1answer
54 views
Problem evaluating moles in a an isochor transformation
I have a problem with an isochor transformation.
Me and my group of study made an experiment that want to check Gay-Lussac’s law.
We registered the equilibrium states and fitted the $P = nRT / V$, ...
1
vote
1answer
70 views
Thermodynamic process when nebula is heated
The basic thermodynamics problem is stated as follows.
The nebula contains a very tenuous gas of a given number density (atoms per volume) that is being heated to a given temperature. What is the ...
2
votes
2answers
805 views
Calculating work done on an ideal gas
I am trying to calculate the work done on an ideal gas in a piston set up where temperature is kept constant. I am given the volume, pressure and temperature.
I know from Boyle's law that volume is ...
1
vote
1answer
371 views
Adiabatic expansion [closed]
I'll start off by saying this is homework, but I ask because I don't understand how the math should work (I don't just want an answer, I'd like an explanation if possible). I understand if this is ...
0
votes
1answer
49 views
Performing work on a box of gas by lifting it, and first law of thermodynamics
What happens if we lift a box of ideal gas? Work is done to the box but no heat is getting into it. So does it's internal energy increase by the amount of work done? Or is it that lifting is not ...
4
votes
1answer
130 views
Ideal gas and diatomic gas with same temperature
If a box of ideal gas and another box of diatomic gas are in thermal equilibrium,
does it mean that the average translational energy of ideal gas particle (A) is the same as that of diatomic gas ...
0
votes
1answer
1k views
Work Done by an Adiabatic Expansion
I am given the information that a parcel of air expands adiabatically (no exchange of heat between parcel and its surroundings) to five times its original volume, and its initial temperature is 20° C. ...
2
votes
1answer
602 views
Work Done in an Isobaric Process
I am given the information that an air parcel undergoes isobaric heating from 0° C to 20° C, and that's all I'm given. I have to determine the work done by the parcel on its surroundings. I know that ...
0
votes
1answer
683 views
Work on ideal gas by piston
Imagine a thermally insulated cylinder containing a ideal gas closed at one end by a piston.
If the piston is moved rapidly, so the gas expands from $V_i$ to $V_f$.
The expanding gas will do work ...
1
vote
2answers
245 views
Is it Possible to have Adiabatic Processes other than $PV^\gamma$ for the ideal Gas?
Is it possible to represent an adiabatic process for an ideal gas by a formula other than $PV^\gamma=Const$?:
Relevant Considerations:
We always need to connect a pair of arbitrary points/states ...
2
votes
2answers
104 views
May molecules of ideal gases have an inner structure?
The following question is probably very elementary:
whether molecules of ideal gases may have optic properties?
As far as I understand, when one discusses optic properties, one assumes that molecules ...
2
votes
4answers
6k views
Why are volume and pressure inversely proportional to each other?
It makes sense, that if you have a balloon and press it down with your hands, the volume will decrease and the pressure will increase. This confirms Boyle's Law, $ pV=k=nRT $.
But what if the ...
1
vote
0answers
154 views
Centrifugal Compressor Flow Rate
For a centrifugal compressor, as found in most turbochargers on internal combustion engines, is there a noticeable change in flow rate versus a naturally aspirated flow rate? In other words, does the ...
-1
votes
1answer
216 views
Black body balloon in vacuum [closed]
The problem statement, all variables and given/known data
There is a perfectly spherical balloon with surface painted black. It is placed in a perfect vacuum. It is gently inflated with an ideal ...
3
votes
3answers
477 views
What does it take to derive the ideal gas law in themodynamics?
How can the ideal gas law be derived from the following assumptions/observations/postulates, and these only ?
I'm able to measure pressure $P$ and volume $V$ for gases.
I notices that if ...
1
vote
1answer
2k views
0
votes
1answer
124 views
Expansion of Helmholtz energy
To get an expansion of Helmholtz energy of
a) an ideal gas
b) a Van der waals gas
we must integrate
$\left ( \frac{\delta A }{\delta V} \right )_{T}=-P$
I saw the solution is :
Can you ...
5
votes
1answer
219 views
Energy formula for separating $O_2$ from mixture of $O_2$, $NH_3$ and $H_2O$
I have a physics problem I'd like to make sure I get correct.
The practical aspect of this problem is that the photosynthetic efficiency of algae is inhibited with dissolved O2 in the growth medium, ...
1
vote
3answers
649 views
When a gas expands against an external pressure of 0, must the stopper on the cylinder be massless?
Basically, I need to conceptually understand why the work a gas does is the integral of pressure external * dv and is 0 when pressure external is 0. I understand why dw = - p external * dv and so ...
4
votes
3answers
1k views
Differentiating the ideal gas law
In reading Fermi's Thermodynamics, to show that $C_p = C_v + R$, the author differentiates the ideal gas law for a mole of gas ($PV = RT$) to obtain: $PdV + VdP = RdT$. Now, the only way I am able to ...
1
vote
1answer
3k views
Why does a gas get hot when suddenly compressed? What is happening at the molecular level?
My guess is that the molecules of gas all have the same speed as before, but now there are much more collisions per unit area onto the thermometer, thus making the thermometer read a higher ...
4
votes
3answers
2k views
What type of substances allows the use of the Ideal Gas Law?
I know that I can use the ideal gas law with pure gases or pure liquids. But can I also use the ideal gas law at saturated gases and saturated liquids as long as they aren't two phase substances?
12
votes
4answers
800 views
How slow is a reversible adiabatic expansion of an ideal gas?
A truly reversible thermodynamic process needs to be infinitesimally displaced from equilibrium at all times and therefore takes infinite time to complete. However, if I execute the process slowly, I ...
