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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What determines the boiling point of a mixture of two constituents? [on hold]
I’d like to understand what is happening at a molecular level. Does the the more volatile constituent boil off first, leaving the less volatile constituent?
2
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1answer
30 views
Vapor pressure vs. ambient pressure
I've managed to get myself thoroughly confused in thinking about the vapor pressure of a substance at a particular temperature $T$, and how it relates to the pressure of the substance if it is in a ...
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1answer
57 views
How to find the Cp, difference of Cp and heat of fusion from the dependence of vapor pressure on temperature?
The vapor pressure of zinc varies with temperature as
$$\log P(\pu{mm Hg}) = -6850/T - 0.755\log T + 11.24 \label{eqn:1}\tag{1}$$
and that of liquid zinc as
$$\log P(\pu{mm Hg}) = -6620/...
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1answer
29 views
Liquid solutions and vapour pressure
"The vapour pressure of water at 80° C is 355 torr. A 100 mL vessel contained water-saturated oxygen at 80° C, the total gas pressure being 760 torr. The contents of the vessel were pumped into a 50 ...
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1answer
38 views
Applying Raoult's Law in volatile solids–liquid solutions
My textbook explains applying Raoult's Law for the two cases:
liquid–liquid solutions, in which the vapour pressure of the solution is due to both the components
non-volatile solids–liquid solutions, ...
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1answer
82 views
Is it possible to have only liquid in a closed container?
I recently read an answer by Aman Rusia for this question: Is a liquid in a container always in equilibrium with its vapour?
In it, they say that
You can't have a container filled with only ...
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1answer
67 views
At boiling point, is the total pressure twice the atmospheric pressure? [duplicate]
We know that one definition of boiling point is that it's the temperature at which the vapor pressure is same as the atmospheric pressure.
Assuming a closed container, does that mean that at this ...
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0answers
37 views
Issue with evaporation rate of water
The evaporation rate of water (kg/s) is given by:
$$g = \frac{P}{P_o} AΘ$$
Where $P$ is given in Pascals and $A$ is the surface area (in $m^2$) and $Θ$ is the empirical evaporation ...
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Quantitative Transfer of Volatile Standards
(Edited w/ updates) Okay, long story short I work in a lab which has been working on cannabinoid analysis (in the licensed Canadian market) and have had a lot of issues surrounding the standards/...
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1answer
41 views
Microscopic and mechanical approach to boiling point [duplicate]
I am confused as to how I should visualize the boiling process throughout a liquid.
From my understanding, the boiling point of a liquid is when its vapor pressure reaches atmospheric pressure. This ...
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1answer
61 views
Is vapour pressure a surface phenomenon?
As a fact, I know that vapour pressure doesn't depend on surface area.
Does this imply it is not a surface phenomenon also?
It shouldn't be as then it would depend on surface area of molecules and ...
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0answers
62 views
Will evaporation from two immiscible liquids blow up a balloon?
Consider the following setup:
Two immiscible liquids A and B are placed inside a balloon at a temperature where neither one of them boils. The inside of the balloon contains some argon, and the ...
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3answers
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Is it possible to boil a liquid by just mixing many immiscible liquids together?
In open air, when vapour pressure reaches 1 atm, boiling takes place.
I read that if we add two immiscible liquids together, the total vapour pressure of the 'mixture' is close to $p = p^*_A + p^*_b$,...
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0answers
39 views
For azeotropic mixtures, is the total vapour pressure at equilibrium equal to the partial pressure of one of the components?
I know, a ridiculous statement. But here's how I reached at it .
Say we have a solution of two components liquids A and B.
By Raoults law,
$$p_A= p_A^o \times x_A \tag1$$
Also by Dalton's law,
$$...
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2answers
89 views
Question about liquid-phase in P-T Diagram
Currently, I have been learning about P-T diagrams and vapour pressure and I have a question that seems like it should have a simple explanation yet I am not able to understand it.
Taking the P-T ...
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1answer
90 views
Is 99% Isopropyl Alcohol sold in stores really 99%?
My understanding is that an azeotropic mixture of isopropanol and water is 91%. This makes sense as to why there are so many brands of rubbing alcohol sold at 91%. There are also some sold as 99%, ...
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196 views
Volume of dried gas at STP
A $54.0\ \mathrm{mL}$ sample of oxygen is collected over water at $20\ \mathrm{^\circ C}$ and $770\ \mathrm{Torr}$ pressure. What is the volume of the dry gas at STP?
By using the combined gas law, I ...
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2answers
254 views
Volume change in positive deviation from Raoult's Law
Let us take a mixture of ethanol and acetone as an example. When ethanol is mixed with acetone, the hydrogen bonding between ethanol molecules gets disturbed as actone molecules get in between the ...
2
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1answer
117 views
what is actually supercritical fluid? [duplicate]
let’s take an example: if we have a glove-box filled with helium at 5 bars at room temperature which is far beyond its critical point, what actually it would be like ?
would it be like a normal gas ? ...
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2answers
92 views
Calculate Gibbs energy of dinitrogen pentoxide using its vapor pressure and sublimation
I am having trouble with the following problem:
Dinitrogen pentoxide, $\ce{N2O5}$, is a solid with a high vapor pressure. Its vapor pressure at $\pu{7.5 °C}$ is $\pu{100 mmHg}$, and the solid ...
2
votes
1answer
47 views
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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2answers
246 views
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
77 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
382 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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1answer
70 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 ...
2
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1answer
37 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
273 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 ...
0
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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
399 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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2answers
144 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 ${x}$, and ${x}$ was great ...
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0answers
45 views
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 ...
2
votes
1answer
57 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 ...
2
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1answer
313 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
51 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
54 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
105 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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51 views
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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0answers
74 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 ...
2
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1answer
149 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
83 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 ...
3
votes
1answer
92 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
78 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
284 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
30 views
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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0answers
430 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
$$\mu_i=\left(\frac{\partial U}{\partial N_i}\right)...
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213 views
Is my proof valid for the formula of elevation in boiling point? [closed]
Is my proof valid for the formula of elevation in boiling point?
proof
By Clausius clayperon equation,
$$\ln(P)=-\frac{∆H_v}{RT}+c$$
Differentiating,
$$\frac{dP}{...
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0answers
121 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
571 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).
...
4
votes
1answer
647 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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0answers
169 views
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 ...
