Questions tagged [vapor-pressure]
This is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. Apply this tag to questions involving clarification related to vapor pressure.
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vapor pressure of one part of binary compound
Let's say we have a binary compound AB in an enclosed container, and let's say there's a tendency to form B-vacancies so that B atoms/molecules escape and form a vapor. Let's assume there's enough of ...
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The composition of vapour in mass percent [closed]
A solution of benzene and toluene is 50% benzene by mass. The vapour pressures of pure benzene and pure toluene at 25C are 94.2 your and 28.4 tore respectively. Assuming ideal behavior, calculate th ...
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vapor pressure and elevation clarification
I’m a bit confused on why higher elevations/decreased atmospheric pressure wouldn't affect the vapor pressure of a liquid-or have a negligible affect on vapor pressure.
With decreased atmospheric ...
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1answer
30 views
Can a solid have a vapor pressure without the ability to sublimate?
Does sublimation occur when a solid turns into a gas and THEN vapor pressure is produced or does the solid first have a vapor pressue and then when the vapor pressure of the solid equals the ...
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1answer
77 views
Can ideal gas law be applied to water vapour? [closed]
How to accurately estimate the molar concentration of pure water vapour at 298 K? Can ideal gas law be applied to water vapour to calculate the molar concentration?
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32 views
Boiling of a liquid [duplicate]
Consider water as an example. I m really confused when does boiling takes place. When it's vapour pressure equals atmospheric pressure or when it's saturation atmospheric pressure equals atmospheric ...
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1answer
32 views
Boiling temperature of salt water at low pressure
With a hydro aspirator with re-circulating water (see here), the maximum vacuum you can get is set by the water vapor pressure given the temperature.
Can you lower the vapor pressure measurably by ...
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1answer
69 views
Entropy as the driving force for osmosis
How is entropy responsible for osmosis and is movement of solvent possible from its higher concentration to lower concentration?
By concentration, I will be referring to the concentration of solvent ...
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0answers
56 views
Reason for formation of bubbles at boiling point [duplicate]
As I understand it, boiling takes place when the saturated vapour pressure equals to the atmospheric pressure.
But, why does the vapour pressure need to be equal to the atmospheric pressure for ...
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1answer
167 views
Why does freezing point decrease when vapour pressure decreases in dilute solutions?
I was studying colligative properties of dilute solutions, and one of the properties was freezing point depression. The confusion I had was that, if vapour pressure decreases, it should be easier to ...
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1answer
108 views
Is it true that an evaporating molecule has the same kinetic energy as a molecule in a pot of boiling water?
A molecule on the surface of room-temperature water shoots off the surface of said water, or in other words, it "evaporates." It does so because it gained kinetic energy ...
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How does association within vapor or dissociation within liquid affect the ideal nature of a binary solution?
As I understand, when there is positive deviation of a binary solution from Raoult's Law, the equilibrium partial pressure curve approach ideality (i.e a straight line dependence of equilibrium ...
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1answer
41 views
Double surface in the pressure temperature concentration curve for a binary mixture
In the 3 dimensional diagram given, when a constant pressure plane intersects with the double surface, it produces a looped curve without a maxima or minima. What is the double surface and how is the ...
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what is the purpose of steam in 'steam distillation' of aniline?
According to me,steam helps in increase in the vapour pressure so as to reduce the boiling point of the mixture.
In my book,it is given that steam is used to reduce the vapour pressure of the liquid.
...
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1answer
126 views
Why is the equilibrium constant of water with its vapour equivalent to its vapour pressure?
Can someone conceptually explain why the equilibrium constant is equivalent to the vapour pressure of water for the above equilibrium reaction?
For example if $K = x$, then it is said that vapour ...
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1answer
35 views
Can air inside a high temperature (1300C) Kiln cause an explosion?
I saw many kiln designs that lack an opening for hot\pressurized air to come out , or any pressure valve.
But when air is heated to such a high temperature (1300C) inside a closed chamber (the kiln), ...
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1answer
48 views
High vapor pressure cooking
On a Wikipedia article about latent heat, it can be found:
The large value of the enthalpy of condensation of water vapor is the
reason that steam is a far more effective heating medium than ...
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1answer
63 views
Thermodynamics energy balance question help
I made the following attempt to solve this question.However I don't know how to find final pressure.I don't know how to find final temperature for both sides.Can you give me a hint?
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Can a droplet of formalin evaporate in midair while falling?
I am designing an evaporator for use in an enclosed environment. Due to the hazardous nature of formaldehyde, I want my evaporator to be wick-free.
The environment in which the evaporator will be used ...
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63 views
What causes both components of a binary gas mix to condensate at the same time for a given composition
Okay, so recently I encountered the temperature - mole fraction diagrams for binary vapour-liquid equilibrium. For now, I only consider two-component systems where the components are very similar and ...
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61 views
Electrolysis under high pressure
Suppose we submerge a bell-shaped electrolysis chamber, flip it under water to have it filled with water, flip it again (so that the top is closed and the bottom is open), and lower it deep into weak ...
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1answer
50 views
Does Langmuir model predict evaporation rates?
Slide #16 of this presentation on amalgams says that "Langmuir's equation" provides a specific "theoretical maximum evaporation rate" for liquid Hg as a function of temperature and surface area.
The ...
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1answer
61 views
When boiling a liquid, how vapour pressure and ambient pressure get equal? [duplicate]
When boiling a liquid, how vapour pressure and ambient pressure get equal?
As vapour pressure will increase, it will lead to increase in ambient pressure also.
let, Initially there would be some ...
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1answer
78 views
Acetic acid odor while testing CO2 sensor; can it be easily removed, is there a better way?
A friend asked me to help test a hobby-quality $\ce{CO2}$ sensor MG-811 (updated link). It uses a solid electrolyte and should provide a sensitivity of something like -40 mV per decade. I though I'd ...
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1answer
63 views
Vapor Pressure, Equillibrium, and Increasing Pressure
I'm trying to make sure my understanding of vapor pressure and transients is correct.
Let's assume I have a thermally-controlled sealed environment which started out as the regular air (i.e. ...
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1answer
277 views
A chamber to control concentration of a vapor: Is there a name for this equipment?
Mechanical engineer here so please excuse me if my question seems dumb to you!
I want to have a chamber $(\approx 40 \times 30 \times \pu{30 cm})$ to control concentration $(\pu{ppm})$ of a flammable ...
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1answer
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Inquiry of the Changing of Canned Liquid’s State [closed]
Could you heat a can of water to 212 degrees Fahrenheit but stay below the aluminum or the can’s metal’s melting point. Either through putting the can in boiling water or heating it up. Would it be ...
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234 views
What is the relation between pressure and chemical potential?
I know that in a two-component gas-liquid system (for simplicity) the chemical potential $\mu_i$ ($i=1,2$) and total pressure $p$ can be defined by
$$\mu_i=\left(\frac{\partial U}{\partial N_i}\right)...
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142 views
Is my proof valid for the formula of elevation in boiling point? [closed]
Is my proof valid for the formula of elevation in boiling point?
proof
By Clausius clayperon equation,
$$\ln(P)=-\frac{∆H_v}{RT}+c$$
Differentiating,
$$\frac{dP}{...
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0answers
74 views
Why does only a single azeotropic composition exist for a mixture of two given substances?
In the image below, which represents a generic composition vs. temperature plot for a mixture, there is a single intersection point between the vapor and liquid curves. This is due to the fact that ...
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1answer
366 views
How can I calculate the concentration of ethanol vapor in an airstream?
How can I calculate the concentration of ethanol vapor in an airstream?
The steady state generation flow rate (of the vapor) is 625 ft^3/min. The ambient temp is 50-60 F (we can use avg temp 55 F).
...
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1answer
384 views
When heat is increased, does water move upward in a straw due to increased capillary action or increased pressure?
I left a water bottle with an internal straw in my car throughout a long, hot day. When I opened the bottle at the end of the day, water immediately splashed out from the straw. This made me wonder if ...
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Anhydrous ammonia vapor-liquid equilibrium
I have been given a anhydrous ammonia vapor liquid system in an air-tight container where the pressure is 30 bar and the temperature is 30 degrees. They claim the system is in equilibrium, which I ...
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1answer
123 views
Bromine monochloride equilibrium
The value of $K_p$ for the reaction
$$\ce{Br2(l) + Cl2(g) <=> 2BrCl(g)}$$
is $\pu{1 atm}$. At equilibrium in a closed container partial pressure of $\ce{BrCl}$ gas is $\pu{0.1 atm}$ and at ...
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1answer
91 views
Metals Vapor Pressure [duplicate]
I know metals like copper, silver and gold for example have vapor pressures at high temperature but do their vapor pressures still exist at standard temperatures (290 kelvin) and pressures (100 ...
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1answer
393 views
Solution to Raoult's Law for a volatile binary solution (no pun intended)
Raoult's Law
In a closed container, $$P_A=P_A^\circ x_A$$ where $P_A$ is the pressure of compound in gaseous phase, and $x_A$ is the mole fraction of the liquid component A in the liquid mixture. If ...
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Predicting the vapor pressure of water ammonia solution
I am working on a project that involves the compressors for a vapor compression refrigeration cycle of R717 (ammonia) and came across something that has been boggling my mind a little bit for no good ...
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1answer
813 views
What would be the vapor pressure of water at above 100 degrees Celsius?
Water boils when it's vapor pressure equals atmospheric pressure (i.e., 760 mm of Hg) which is at 100 degrees Celsius. If the temperature is further increased, would the vapor pressure also increase ...
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230 views
Pressure increase due to thermal increase
I got the following question from a colleague:
We got a certain situation where water gets trapped in a viscous liquid. A lot of energy is added so now we want to know what the pressure becomes inside ...
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Alternative to mercury bubbler for increasing boiling temp?
A common reaction for forming the octachlorodirhenate(III) anion is to heat tert-n-butylammonium perrhenate in benzoyl chloride at 209 ºC. If you look up the info for benzoyl chloride, one sees that ...
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2answers
226 views
Vapor Pressure Paradox
This is quite an interesting situation I had thought of. Consider two beakers, each containing $\pu{180 g}$ of water. Also, suppose one of the two has $\pu{1.8 g}$ of glucose dissolved in it. Let's ...
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Water vapor equilibrium calculations
The question had two parts.
The first part said:
Calculate the amount of water required to saturate a vessel of volume 82 L at 300 K given that the vapor pressure of water is 38 torr at 300 K.
The ...
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60 views
Chemically generating a high vacuum?
Suppose I fill a vacuum chamber with 99% oxygen, then pull a vacuum on it down to 10 pascal absolute. If I then vaporize aluminum (for vapor deposition), will the aluminum bind with the remaining ...
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2answers
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Help me proving Dalton's law of partial pressure formula
How do I prove
$${{\displaystyle p_{i}=p_{\text{total}}y_{i}}}$$
where $y_i$ is the mole fraction of the $i^{th}$ component in the total mixture of $n$ components ?
Here is what I know
...
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1answer
60 views
What is the temperature of evaporating water (not boiling)?
The vapor pressure of water at $\pu{70 ^\circ C}$ is $\pu{233.7torr}$.
If I were to put a temperature probe directly above the liquid water, what would it read?
In other words, does a water molecule ...
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1answer
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Positive deviation from ideal behaviour [closed]
I am confused about Positive behaviour from ideal behaviour as to why it occurs.
1) Molecular attractions plays a dominant role in positive deviation
OR
2) Molecular volume plays dominant role in ...
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2answers
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Why doesn't the vapor pressure of water depend on the humidity?
Correct me if I'm wrong, I'd like to think of vapor pressure of water as the number of water molecules escaping from the water surface per unit area. Greater the leaving number, greater the vapor ...
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3answers
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Is vapour pressure of a liquid solution constant at a given temperature, no matter the size of closed container and amount of liquid taken?
Does vapour pressure of a liquid solution depend on the size of closed container, amount of solution taken, given that, temperature is kept constant? Or will it change, if some extra gas is added to ...
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433 views
Rate of evaporation of mercury
A restorer of antique barometers reported in a blog post that he has had a barometer on his wall that has shown no "visible" loss of mercury in 15 years.
I was kind of curious about this, wondering ...
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1answer
516 views
Is using melting/boiling point good to measure volatility?
I wanted to figure out a way to compare volatility in organic compounds, so I read on many forums on the differing ways to measure volatility, which included enthalpy of vaporization and melting/...
