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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The relationship between the temperatures at different times and pressures at different times is? [closed]
At the instant the boiling point is reached, the vapour pressure of the solution should be equal to atm. pressure. And since the boiling is continued the pressure will keep on increasing. Thus the ...
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Two-Phase Pressure Drops in Screen-Plate Bubble Column
I am reading the paper A Correlation of Two-Phase Pressure Drops in Screen-Plate Bubble Column
The goal of the paper is to come up with a regression model for a correction factor (denoted $K$) for a ...
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1answer
176 views
Volatile alkali metal compounds
Most elements are or have compounds that are gases or have a significant vapor pressure at room temperature. Fluoride is a powerful tool for producing highly oxidized covalent and volatile compounds. ...
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Combining two high-VP chemicals to get a low-VP mixture
I'd like to do a class experiment as a metaphor for human relationships. Two people each have a different chemical which evaporates quickly (at STP). There is one glass between them. If only one ...
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1answer
52 views
Is the vapor pressure of a liquid dependent on the pressure of the atmosphere in which it is measured?
The figure below shows how vapor pressure of a liquid is measured. Initially the flask is at atmospheric pressure. Then the liquid is dropped in the flask. Once equilibrium is reached, the pressure ...
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Cases when Raoult's law is unsolvable
Setup
Consider a closed binary mixture of known total molar composition $n_i$, held at volume $V$ and temperature $T$. The equilibrium phase composition is determined by $\mu_i^{vap} = \mu_i^{liq}$. ...
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1answer
39 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
75 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
$$\log P(\pu{mm Hg}) = -6620/...
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1answer
38 views
Liquid solutions and vapour pressure
"The vapour pressure of water at 80° C is 355 torr. A 100 mL vessel contained water-saturated oxygen at 80° C, the total gas pressure being 760 torr. The contents of the vessel were pumped into a 50 ...
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1answer
53 views
Applying Raoult's Law in volatile solids–liquid solutions
My textbook explains applying Raoult's Law for the two cases:
liquid–liquid solutions, in which the vapour pressure of the solution is due to both the components
non-volatile solids–liquid solutions, ...
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1answer
98 views
Is it possible to have only liquid in a closed container?
I recently read an answer by Aman Rusia for this question: Is a liquid in a container always in equilibrium with its vapour?
In it, they say that
You can't have a container filled with only ...
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1answer
71 views
At boiling point, is the total pressure twice the atmospheric pressure? [duplicate]
We know that one definition of boiling point is that it's the temperature at which the vapor pressure is same as the atmospheric pressure.
Assuming a closed container, does that mean that at this ...
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Issue with evaporation rate of water
The evaporation rate of water (kg/s) is given by:
$$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
48 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
93 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
70 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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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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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
113 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
149 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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303 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
375 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
138 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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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 ...
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1answer
50 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
354 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
85 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
600 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
80 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
41 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
406 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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59 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
437 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
160 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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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
59 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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1answer
348 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
55 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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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
123 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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77 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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1answer
181 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
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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
95 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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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
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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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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)...
