Looking for colder, humidify and pesticides β€œfree” vapor. Do you think the air pressure change is bad for the volcano v.redd.it/4u1wkzq50k881
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πŸ‘€︎ u/Hot_Pie_6212
πŸ“…︎ Dec 29 2021
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Vapor Pressure Confusion

Hi all. I'm a mechanical engineer working with issues related to vapor pressure in underground gasoline storage tanks. I have been trying to refresh myself on vapor pressure issues since I haven't really had to work with this since college. I am performing a pretty simple experiment and completely striking out in trying to understand the results. I am hoping that these are easily explained by someone who understands the physics here.

The experimental setup is as follows. I have placed 300 mL of gasoline (E10 unleaded) in a 1300 mL stainless steel vessel that is then placed in an environmental chamber kept at 20Β°C throughout. The lid of the vessel is tapped for a pressure transducer and a ball valve to vent pressure when desired. For initial conditions, the 300 mL of gasoline was placed in the vessel and the lid sealed. The remaining space is filled with air at 20Β°C and about 40% rh. Over time the pressure in the headspace rises as expected. I didn't let the vapor space reach saturated vapor pressure on the first rise as measuring that wasn't the subject of interest. After a time, the pressure in the vessel was vented through the ball valve, releasing a mixture of the gasoline vapors and the air from the initial conditions. This time I left the vessel undisturbed overnight and the pressure reached an equilibrium pressure roughly half of what it was when I vented. This was expected from prior experience. I thought that this might be explained by the fact that gasoline is a mixture of hydrocarbons with different volatilities and that I had been evaporating off the light ends of the mixture. This procedure of venting and waiting for the vapor pressure to rise was repeated several times with the equilibrium pressure in the headspace dropping each time. I have a graph of the pressure vs. time here. https://imgur.com/5c0mego. The two small upsets in pressure come from injecting a mall 45 mL of air into the chamber (1st upset) and then removing 45 mL of gasoline and replacing with 45 mL of air (2nd upset). The last thing that I did was to open the top of the vessel to allow an exchange of some of the gasoline vapors for air. After this venting and exchange, the vapor pressure again rises rapidly with the curve matching the original.

My reading on vapor pressure suggests that the saturation vapor pressure is an equilibrium between the liquid and vapor phase of the hydrocarbons in the gasoline. My understanding is that this should be

... keep reading on reddit ➑

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πŸ‘€︎ u/madHatch
πŸ“…︎ Jan 08 2022
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Is VPD (Vapor Pressure Deficit) values universal across species or specific to species/localities?

I am not a botanist and reading about VPD. I am trying to find a reference for VPD for cacti but all I find is general tables for plants at different maturities -aimed mostly at growing marijuana or other plants for consumption, which I am not interested in.

From my basic understanding, I would expect that VPD requirements would be a genetic adaptation (ie. arid plants would have different requirements to tropicals).

However, I don't know the fundamental stomata mechanism like you all would and unfamiliar if they behave similarly across all plant species or not.

Thank you in advance! Also if you have any references for various plants, it would be appreciated! I did a few Google scholar searches and came up empty handed, perhaps because I am not using the right search keywords.

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πŸ‘€︎ u/jheins3
πŸ“…︎ Dec 07 2021
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Water vapor imagery this morning from #GOESWest is showing how an atmospheric river is pummeling the Pacific Northwest and Canada with heavy rainfall. We can also see a swirling low pressure system over the North Pacific, near Alaska. mobile.twitter.com/NOAASa…
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πŸ‘€︎ u/Bonus1Fact
πŸ“…︎ Jan 12 2022
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What will be the vapor pressure of a superheated gas?

I was solving material balance for an electrolyser during my final year project plant design. I am sure that during water electrolysis, hydrogen gas leaving the electrolyser entrains some water with it and I have to calculate what is the amount of that entrained water.

I found no equation for amount of entrained water yet but I got the idea that the leaving hydrogen gas will be saturated with water vapors. So if I am able to find the vapor pressure of water in that hydrogen water mixture, I will be able to calculate the composition. I am applying Raoult's law here. I know the total pressure and all I need is to find the saturation pressure of both water and hydrogen. The saturation pressure of water can be known but not of hydrogen at the give conditions. Is there a way to find? Of course hydrogen will be superheated at the conditions.

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πŸ‘€︎ u/AftabAdeel12
πŸ“…︎ Dec 04 2021
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ELI5 Why does high pressure air form a white vapor cloud when it's released?

I'm sure this is a simple answer but it's one of those questions that's hard to Google. I noticed this most recently watching Smarter Every Day's baseball cannon footage and every time the cannon fires a huge white cloud that looks like smoke comes out of the barrel, but the only thing inside of it is pressurized air. Why does that air form vapor like that when it's released back out into the atmosphere?

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πŸ“…︎ Dec 08 2021
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Can someone explain what's vapor pressure and what we need to know from it? Do we just got to know how it relates to water in regards to the forces or the phase changes?

I'm a bit confused about it.

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πŸ‘€︎ u/doneeithit
πŸ“…︎ Dec 26 2021
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Vapor Pressure Deficit - An Important Factor in Plant Health

A new post is up on my blog. I do these things when I feel it will add to someone's knowledge and when, frankly, I feel the need to reinforce my own understanding. And there's no better way to do that than trying to explain it.

Join me on the journey if you like. The more you know, the more you grow.

Redwing Farm Blog

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πŸ‘€︎ u/IntheHotofTexas
πŸ“…︎ Nov 17 2021
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Just one mile from the creepy red light district, and under weird urban settings lit by High Pressure Sodium and Mercury Vapor, this retro train still holds on to its original speed and power racing by the camera. v.redd.it/2gazbb4dg0i71
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πŸ‘€︎ u/LongTimeChinaTime
πŸ“…︎ Aug 18 2021
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My first aid/asthma kit I carry around. my boyfriend is asthmatic so have a first aid kit, his inhaler, vapor rub, hand warmers, eye drops and the blood pressure cuff so I can make sure his heart rate goes back down if he has an attack. I think I maybe be to paranoid but better safe then sorry😁 reddit.com/gallery/m4ojdr
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πŸ‘€︎ u/ambydeer
πŸ“…︎ Mar 14 2021
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Eppendorf concentrators: what exactly does the 'high vapor pressure' program do differently?

I just got a new eppendorf concentrator plus.

There are settings for aqueous, alchohol, and high vapor pressure.

Normally I am drying solvents like acetone. Sometimes I dry methanol or water.

My previous concentrator didn't have such settings; you simply set the temperature and turned it on. I'm wondering exactly what the different programs do differently and which I should use for what. Any ideas?

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πŸ‘€︎ u/sciensteve
πŸ“…︎ Aug 02 2021
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95 Nissan Sentra GLE Vapor Pressure In The Gas Tank

I have a wierd problem with vapors building up in my gas tank. If I run the A/C or it's a hot day out (usually both things seem to factor into this), the car will cut off and refuse to start til I unscrew the gas cap, and vent the vapor that's built up in there.

I'm not sure why it's not venting this vapor build up on it's own, I'm fairly sure it's supposed to, right?

What can I do to narrow down what's going on and fix it? Is this dangerous to my car/engine?

The car runs perfectly other than this one issue.

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πŸ‘€︎ u/HeartToSky
πŸ“…︎ Aug 21 2021
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Atmospheric drying will lead to lower crop yields, shorter trees across the globe. A global observation of an ongoing atmospheric drying -- known by scientists as a rise in vapor pressure deficit -- has been observed worldwide since the early 2000s. twin-cities.umn.edu/news-…
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πŸ‘€︎ u/MistWeaver80
πŸ“…︎ Mar 09 2021
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Fuel vapor pressure in tank possibly forcing excessive fuel into carb when I open the petcock on hot days.

I recently replaced the tank on my 2003 Hugger 883 with a lowbrow frisco tank. It does not retain the stock overflow line and I’m using a gravity fed petcock. When the bike sits on hot days vapor is building up in the tank so when I open my petcock fuel in flooding my carb and dumping out onto the ground. Does this mean that my gas cap isn’t venting properly? I was under the impression vented caps only let air IN to prevent vapor lock or worse tank collapse. Do I just have to remember to pop my cap off to let the pressure out before I open the petcock? Any ideas would be greatly appreciated.

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πŸ‘€︎ u/Samsquanch49
πŸ“…︎ Jun 03 2021
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Water Vapor Pressure map in US2 glitched...
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πŸ‘€︎ u/DustWorlds
πŸ“…︎ Jul 07 2021
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The Sebesha Vapor Canyon: Pressure-Contained Alien Biosphere reddit.com/gallery/mb61e4
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πŸ‘€︎ u/LORDGHESH
πŸ“…︎ Mar 23 2021
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I'm having trouble understanding the context. May you explain Vapor, Partial vapor, partial pressure briefly? How should I model in my imagination? A liquid in a closed box? An open box? What does the author try to say by emphasizing ''if there is no liquid". I also couldn't get the last sentence.

"The partial pressure of a vapor must be less than or equal to the vapor pressure if there is no liquid present. However, when both vapor and liquid are present and the system is in phase equilibrium, the partial pressure of the vapor must equal the vapor pressure, and the system is said to be saturated. The rate of evaporation from open water bodies such as lakes is controlled by the difference between the vapor pressure and the partial pressure."

Thank you. Edit: That’s why I love this community. Everyone is eager to have me understand the topic. I wish I could give awards to all of you.

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πŸ‘€︎ u/ZedveZed
πŸ“…︎ Feb 17 2021
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S. 2339: A bill to amend the Clean Air Act with respect to the ethanol waiver for Reid vapor pressure limitations under such Act.

Introduced: Sponsor: Sen. Deb Fischer [R-NE]

This bill was referred to the Senate Committee on Environment and Public Works which will consider it before sending it to the Senate floor for consideration.

2 cosponsors are on that committee.

Govtrack.us Summary

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πŸ‘€︎ u/congressbot
πŸ“…︎ Jul 15 2021
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Does Atmospheric pressure affect Vapor Pressure?

This question my teacher gave us basically asks if there is a decrease in atmospheric pressure, will the vapor pressure of some substance A) Increase B) Decrease or C) Stay the same. Any help would be greatly appreciated!

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πŸ‘€︎ u/LuckyTruth6049
πŸ“…︎ Jun 01 2021
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[College Chemistry: Clausius-Clapeyron Equations] Solving for vapor pressures - I got 2.826, but I don't understand what steps they used to get 45.0 torr. Everything I've attempted produces the wrong answer.
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πŸ‘€︎ u/banshithread
πŸ“…︎ Jun 22 2021
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Terragenesis logic: 0 atm pressure with 600000cm (vapor in atmosphere) 🀷 reddit.com/gallery/nem1jz
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πŸ‘€︎ u/Shiori-Itsuka
πŸ“…︎ May 17 2021
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Vapor Pressure Clarification

I'm a bit confused about vapor pressure. I know when vapor pressure = ambient pressure, boiling occurs. But when a substances undergoes evaporation, the remaining solution loses energy so as to get the molecule in the gas phase. This would lower the temperature of the solution? while also increasing vapor pressure, as now there's more gas particles. But as there's increased gas particles it's increasing the pressure above the solution making it harder to evaporate/boil. So then as evaporation occurs, causing a vapor pressure increase, how does that make it closer to boiling as the solution has decreased in temperature and there's an increased pressure being exerted above the solution? Or is the increased vapor pressure just preventing evaporation in closed environments? Isn't this the premise of humid vs dry environments. Like sweating is harder in humid environments b/c there's a greater vapor pressure and so the sweat molecules can't evaporate? But this is an "open container"? Would love any clarification on this!

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πŸ‘€︎ u/leilanang4
πŸ“…︎ Jun 09 2021
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VPD (Vapor Pressure Deficit) New Growers go look it up!!! 🌱🌱

I just learned a lot about VPD. I’m relatively new to indoor growing. I’m currently on my second grow. My first time growing in an actual tent and I’m just now hearing about VPD. I just want any new growers to read this and do some research. Anyone with good resources, links, or just some helpful advice please share in the comments!!!

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πŸ‘€︎ u/nassinator
πŸ“…︎ Feb 09 2021
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When radar shows rain storms moving across land (green blobs), is the actual water vapor in the air moving with it , or is the pressure/whatever system moving independently and making the water vapor sitting still in the respective areas fall as the system moves over
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πŸ‘€︎ u/Fit-Ad4365
πŸ“…︎ May 13 2021
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Why Does Vapor Pressure Need To Be Equal to Ambient Pressure at Boiling Point?

Hey guys,

What is a connection between phase change from liquid to gas and equality of vapor pressure with ambient pressure? Why should equality of vapor pressure above liquid and ambient pressure determine when boiling happens? I know that when ambient pressure is higher, molecules in liquid require more energy to spread out to form bubbles of vapor since vapor has lower density than liquid, so higher temperature is needed to reach this point. But, why should vapor pressure above liquid determine when this point happens?

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πŸ‘€︎ u/Dario56
πŸ“…︎ Mar 24 2021
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ELI5: So I know that for water to boil the vapor pressure has to be equal to atmospheric pressure. Does this mean that as the pressure increases, a substance becomes more gaseous? Then why is CO2 liquid at high pressures?
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πŸ‘€︎ u/fatjazzy
πŸ“…︎ Feb 08 2021
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Vapor pressure equilibrium of formic acid and water

Good day to you all. I am looking for a graph (and preferably a table with it) that shows the temperature and the percentage (weight or volumetric) of water and formic acid for different concentrations of formic acid in water.

r/chemistry helped me as a start of and suggested that combining antoine's law and raoults law might work but I ended up with a linear progression.

The problem I ran into so far is that formic acid doesn't behave like an ideal gas. As it has a negative azeotrope.

Anybody that can help me find this or help me calculate this.

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πŸ‘€︎ u/Bodly1
πŸ“…︎ Jun 11 2021
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help re: vapor pressure

how does vapor pressure relate to the rate of evaporation, boiling point temperature, and IMFs?

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πŸ‘€︎ u/mc-coffee
πŸ“…︎ Apr 12 2021
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Contrary to popular belief, the equation for vapor pressure established 150 years ago by Lord Kelvin is not only valid on a macroscopic level, but also on a molecular level. Even in capillaries, only a few water molecules thick, the equation correctly describes the condensation of water vapor. nature.com/articles/s4158…
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πŸ‘€︎ u/Q_Ahmad
πŸ“…︎ Dec 15 2020
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VPD - Vapor Pressure Deficit - Para alΓ©m do par temperatura e umidade.

Salve jardineiros. Pra quem tem problemas com calor excessivo nesse paΓ­s tropical, recomendo MUITO dar uma lida sobre o VPD. Existem vΓ‘rias fontes e artigos, mas esse achei bem completo e em PTBR: https://thepuffhub.wordpress.com/2020/03/02/vpd-vapor-pressure-deficit-deficit-de-pressao-de-vapor/

Fui juvenil no meu primeiro cultivo e nΓ£o quis investir num termohigrΓ΄metro. Tive vΓ‘rios problemas como hermafroditismo, fungo, deficiΓͺncia e excesso de nutrientes, etc. Tomei vergonha na cara e acabei comprando um medidor desses para o segundo ciclo de cultivo. Descobri que as vezes faz 34ΒΊC na minha tenda, ou seja: considerando a temperatura recomendada para a vega, a plantinha estava sofrendo muito. Fiz o que pude em relação a exaustΓ£o mas as temps continuavam altas pois moro numa parte bem quente do BR. Depois que andei lendo sobre esse Γ­ndice, descobri que posso manipular a umidade para alΓ©m da faixa recomendada e proporcionar conforto para a plantinha mesmo em temperaturas extremas. Farei isso pois alΓ©m da temperatura alta, o medidor tambΓ©m apontava baixa umidade (porΓ©m dentro da faixa geralmente recomendada), o que parece ser pΓ©ssimo para o desenvolvimento das meninas.

Resumindo: COMPREM UM TERMOHIGRΓ”METRO. E leiam sobre esse negΓ³cio aΓ­. Sou leigo mas me parece ser essencial o entendimento dessa relação entre temperatura e umidade para um grow bem sucedido.

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πŸ‘€︎ u/diambagrower
πŸ“…︎ Feb 09 2021
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