Questions tagged [gas]

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Prove that the number density is proportional to the mass fraction divided by the molar mass [on hold]

For a mixture of gases, prove that the number density $(N/V)$ of a gas is proportional to its mass fraction divided by the molar mass. My attempt: $N$ is the number of molecules, $N_A$ is Avogadro's ...
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1answer
75 views

How much air could an activated charcoal bag or baking soda box actually purify / deodorize?

Someone I know recently bought a set of small stylish and expensive cloth bags (roughly paperback book sized) filled with activated bamboo charcoal, that you place in a room and it purportedly ...
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1answer
24 views

How prioritize between conservation of angular momentum and the equipartition theorem?

In most or all description of gas equilibrium the equipartition theorem is used to motivate that energy es equally distributed between rotating and linearly oscillating modes? How can that be since ...
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3answers
76 views

Are there gases that cool down as energy is added?

If there are, please provide examples. Lee Smolin suggests there are such gases in his book, "Time Reborn", but searching on my own, I could not find examples, and it seems hard to accept this is ...
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How is an Isobaric process consistent with the first law of thermodynamics?

Suppose there is an isobaric process whereby the volume of a gas decreases while the pressure of the gas remains constant. Work is done on the gas to compress it. Since the change in internal energy =...
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73 views

In a spinning tube, how low can the vacuum in the center be?

If you put a gas in a tube, and spin the tube [edit: along the axis of the cylinder], you will get a centrifuge. What's the maximum pressure differential between edge and centre? Asked another way: ...
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2answers
64 views

Does the ideal gas law apply to a moving vehicle?

If for example you have a car travelling along a road. There is obviously a high pressure region in front of the car, where the air is forced around the vehicle. Likewise, I understand that cars will ...
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How do gaseous molecules arrange themselves in liquids when they are “dissolved”?

To provide some context, I am trying to understand in better detail how oxygen from the lungs passes through a membrane and enters the vasculature in order to be transported via blood. I have ...
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1answer
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What will happen if my room is half filled with dry ice? [closed]

Suppose we have a sealed room, the room is a cube, half the room is filled with dry ice. What will happen when the dry ice sublimates to CO2, will the pressure of the room increase dangerously as the ...
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3answers
73 views

Sign of $(\partial T /\partial V )_E$

Consider a realistic gas. If it is insulated and then allowed to expand into a vacuum, how does its temperature change? We have to consider the sign of $\left(\dfrac{\partial T}{\partial V }\right)...
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2answers
44 views

Does the total energy in a volume (gas) increase linearly with increases in pressure?

If a volume has a certain pressure, then double that pressure at another time, is the total energy stored doubled? I'm sure this has to do with thermodynamics and if I remember correctly there is a ...
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1answer
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Is it possible to calculate the refractive index of a gas mixture given the pressure, temperature and wavelength?

I am searching for a formula to calculate the refractive index at a specific point in a planetary atmosphere. Given are pressure, temperature, wavelength and the molecular composition of the ...
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1answer
43 views

Predicting pressure of propane gas in container based on temperature

I'm a mathematician and computer scientist, and for this particular problem I would benefit from some physics/chemistry expertise. I've already asked this question on chemistry stack exchange, but I ...
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0answers
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Realistic vacuum boundary conditions in fluid mechanics?

What are some realistic boundary conditions between a fluid and vacuum? Is there an interface or does the fluid kind of spray out into the vacuum?
2
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1answer
93 views

Derive the kinetic gas equation [closed]

I need a proof of high school level I have confusion in taking probabilities in all directions not yet concluded this, and I need a proof using momentum i.e I need a high school level proof
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4answers
107 views

Negative Specific Heat

It is known that the specific heat of a gas is process dependent.So it must be theoretically possible to have a negative value for a gas according to the following equation (for polytropic process): $$...
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1answer
21 views

Does a mixture of two different gases increase in entropy in a thermally isolated system?

I know gas will increase in entropy as it goes toward equilibrium, but what if there are multiple gases of different densities?
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2answers
32 views

What is the volume of liquid propane consumed when measuring gas flow at a given pressure?

We have a building with a large propane cylinder that distributes propane to different sources within the building. When the cylinder is filled, the propane is compressed to a liquid, and our bill is ...
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1answer
16 views

How to contain air ions inside a chamber without loosing their charge?

I would like to create an experiment where I would hold ionized air molecules. Most likely negative O2-1 ions. I am looking for the most appropriate enclosure so that the ions do lose as little of ...
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How to calculate energy stored in a hydraulic hybrid system?

My understanding is that hydraulic hybrid systems have two reservoirs - one at high pressure and one at low pressure. I also understand that the working fluid can then be pumped between these two ...
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1answer
21 views

Are particles that are moving at the fermi energy easier to remove if you model a nucleus as a fermi gas?

Due to the Pauli exclusion principle, the nucleons build up the energy states from the bottom up. When talking about binding energy per nucleon, you are talking about how much energy is needed to ...
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1answer
120 views

Why is the $k$-space in multiples of $2\pi/L$?

So when you find the solution to the Schrödinger equation you get that the wave function can have $k=n\pi/L$, $n=1, 2,3 \dots $ The problem I have is that when calculating the density of states of a ...
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1answer
30 views

simple gas flow between regions

How does gas flow between regions of differing pressures? How does the momentum of the gas effect that flow between regions of differing pressures? I am trying to program a simple simulation of gas ...
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2answers
69 views

Expansion of an ideal gas at constant pressure

I approach these expansion problems like so: The gas and the surroundings(piston+outside) are at the same pressure at first. We heat the gas. The pressure rises inside the syringe a bit. The gas ...
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1answer
25 views

Is the pressure in a pipe equal the pressure in the tank?

In my example, there is a tank which is holding gas under pressure. Connected to this tank is an output pipe. Assuming the pipe is the same diameter for the entirety of its length, would the pressure ...
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2answers
72 views

Does a gas canister change temperature as gas is released?

If you have a deodorant can, it is obvious that the gas leaving the can has cooled as it expands. However, is there also a change of temperature of the gas that remains within the canister? My ...
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1answer
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A balloon popped in a room

This question is Question 23 from CAP exam 2017. An inflated balloon, filled with a gas of temperature T, is held in a room with the same temperature. If we make a small hole on the side of the ...
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4answers
59 views

How can I calculate the speed at which a gas flows from one volume to another?

Suppose that there are two rigid Volumes A and B. Each of these contains a gas with know properties (pressure, temperature, number of moles, volume, composition). Suppose also that there is a pipe ...
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0answers
24 views

How does gas convert to liquid?

I am bit confused, how the refrigerant gas gets converted to liquid after being passed via condenser?
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35 views

How long does it take a gas to equilibrate with a container's temperature?

Initial Conditions in a vessel: P~my unknown, but ~100torr, V=5000cc, T=35C, gas is 50/50 N2/He Laser drill a hole in the initial volume of diameter=10mils through a chamber wall thickness of 0.75mm. ...
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1answer
59 views

Can gases be heated by absorbing laser light?

I have a narrow gas jet, with a laser pointed at it. I want to figure out whether the gas will absorb any thermal energy from the laser photons, if they are at a wavelength that the gas can absorb. ...
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1answer
69 views

How to calculate the specific weight of air?

First of all sorry for my bad English ... I have to calculate the specific weight of air knowing that in the air there is actually a small percentage of water vapor. Therefore the specific weight of ...
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0answers
20 views

Why do low concentrations of H2 in He gas exhibit lower thermal conductivity than either?

Thermal conductivity of He+H2 mixtures, as a function of molar concentration of H2, exhibit a minimum at around 14% H2. See Fig. 2 below from "Thermal conductivity of the hydrogen-helium mixture". ...
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1answer
78 views

How to calculate the mass of gas needed to fill a cylinder to a certain pressure?

I m tasked with a tricky situation. I need to calculate the exact amount a tank can take in gas. But I dont know the volume of the tank. I just need to make sure that the tank reaches the right ...
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2answers
95 views

Does $PV\propto T$ apply to a photon gas?

For an ultrarelativistic ideal gas, I know that $p=\frac{u}3$; $TV^3 =$ constant; $pV\propto T$. For a photon gas, I know that the first two results apply as well. However, I am unsure if the third ...
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1answer
24 views

Temperature excursion energy on Mars [closed]

Could we use the high range of temperature excursion on Mars, for example applied on gases or liquids, to produce some usable energy? Let's assume that the day-night excursion is +20 Celsius (day) and ...
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1answer
55 views

Applying ideal gas law to every day problems

Three classical examples of seeing the ideal gas law in action: crumpled water bottle in cold car crumpled water bottle after your flight lands fridge door harder to open a second time after first. ...
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1answer
35 views

Maintained local concentration of suspended particulates [closed]

Is it possible for suspended particulates to maintain gradient or aggregate into stable clouds due to some interactions between individual particles, or interactions with surrounding gas molecules? ...
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1answer
162 views

van der Waals equation of state plot limitations

When I plot the van der Waals equation of state in terms of Pressure (bar) versus density (mol/L) for propane at 400 K, $$P=\frac{RT}{\big(V_m-b\big)}-\frac{a}{V_m^2}$$ in terms of density, $$P=\...
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1answer
22 views

Affect of temperature on carbonation loss

When opening a bottle of soda (any carbonated drink) some of the 'fizz' rushes out. When you replace the cap, CO2 from the soda migrates to fill the empty space in the bottle and eventually an ...
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2answers
138 views

How to write equation of state in terms of partition function?

While studying quantum gases (fermions, bosons), equation of state written were $PV = k_B T Z_{gr}$, where $Z_{gr}$ is the partition function of grand canonical ensemble. $P$ and $V$ are pressure and ...
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T-s diagram of hydrogen

I'm searching for a T-s chart of hydrogen in the range (0 .. 200 degC, 0 .. 300 bar). (example for nitrogen see here https://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect#/media/File:...
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2answers
313 views

Could the cosmic fluid be better described as a kind of van der Waals gas, or a kind of foam, instead of a dust gas?

In cosmology, it is usually assumed that the cosmological fluid made of galaxies could be described as a gas of "particles" without any pressure (the dust gas), of density $\rho_{\text{matter}} \...
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1answer
38 views

Constant pressure

When we refer to constant pressure like in Charles law what is this pressure? The pressure of the gas or the pressure that the container (the piston maybe) exert on the gas? Also does atmospheric ...
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1answer
66 views

Carrying 10 liter dewar in elevator advisable? [closed]

I am using liquid nitrogen a lot at university and frequently have to carry a 10 l dewar from the storage container into my lab. On this way I have to walk down 4 stories with the heavy dewar. ...
0
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1answer
38 views

Does the amount/speed a balloon rises vary with the temperature of the gas inside, given a constant type and amount of gas?

I'm attempting to conduct an experiment with a balloon. I fill it up with some amount of helium. If I cool the balloon down (say with liquid nitrogen), the balloon's volume will decrease (because of ...
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1answer
31 views

How does flatulence travel through the room when opening a window? [duplicate]

When the smell in my room seems to be full of flatulence(it wasn't me), what happens with the gases when I open a window? Detail: It is winter and the air outside is cold whereas the air in the room ...
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Does Avogadro's law only apply to ideal gases?

I know the ideal gas law may change a little when for real gases or diatomic ones does Avogadro's law change too or does it stay the same?
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Effect of total pressure on the component condensation in a gas mixture

Suppose we take two gases in a vessel with a movable piston. We compress the mixture until first drop of condensate appears. Suppose temperature remains constant during compression. Therefore when you ...
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1answer
33 views

What keeps small mobile bubbles at the bottom of a kettle from rising

We have a glass jug water kettle with a flat heat plate as the bottom. It boils water quite vigorously in 2-6 minutes depending on how full with a 1000+W element. Just today I noticed that very ...