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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Estimate steam dryness using temperature and pressure [closed]

I have a system of 120 degrees Celcius with 1.5 bar g of H2O, how do I calculate the percentage of liquid phase and gas phase?
2 votes
1 answer
71 views

Calculating the amount of water condensed when cooling below the dew point

I've been given the following question: Calculate the dew point temperature of a 60% humid air at $30^oC$. How much water mass wil condensate out of 1 $m^3$ of such air when the temperature is ...
0 votes
1 answer
28 views

Pressure and temperature relation of Novec 1230

I am working on a concept turbine for a school project which operates at low temperature so it's necessary for me to have a pressure temperature relation of this chemical or novec 7100 also is okay.. ...
10 votes
1 answer
785 views

Are molecules exchanged between a solid and liquid in equlibrium?

In Vapor-Liquid Equilibrium, it is my understanding that molecules exchange between the gas and liquid continuously; even when no difference in temperature or partial pressure exists. Regarding Solid-...
1 vote
1 answer
169 views

Phase rule for a pure substance in vapor-liquid region

I'm confused with how the Gibbs Phase Rule works for pure substances in liquid-vapor mixtures. According to the phase rule, there should only be one degree of freedom for a two-phase mixture with a ...
2 votes
1 answer
64 views

Mathematical models of Vaporization-Condensation dynamics

I am a mathematician now studying an introductory chemistry course. Consider a liquid in a closed container, at (say) room temperature. Then some of the liquid will vaporize. Then some of the ...
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0 answers
38 views

Vapor-Liquid Equilibrium and partial pressure of ammonia

I tried searching the forums for a similar question but I do not think it was entirely answered: Suppose I have a closed system in a container with solvent and a certain concentration of gas, say ...
0 votes
3 answers
108 views

How do water vapor molecules push other air molecules away?

I've read that when water vapor enters the atmosphere, the vapor molecules push the oxygen and nitrogen molecules out of the way and occupy their space. But if water vapor molecules are lighter than ...
1 vote
1 answer
79 views

Can vapor pressure be defined for permanent gases?

Vapor pressure of a substance, in a given temperature, is the pressure exerted the vapor in a system where the gaseous and liquid phases of the pure substance are in equilibrium. But, if for a ...
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1 answer
118 views

How do you derive the boiling point elevation equation using Raoult’s law and Clausius-Clapeyron relation?

I know that Raoult's law is $P_{solution}=X_{solvent}P_{solvent}$ and Clausius-Clapeyron equation is $ln(\frac{P_{2}}{P_{1}})=-\frac{L}{R}(\frac{1}{T_{2}}-\frac{1}{T_{1}})$ But how do you derive the ...
1 vote
0 answers
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Saturation of air within isolated system with water and ethanol

I am planning an experiment in an isolated system that contains two droplets. One droplet is water and the other one is a 40% ethanol-water mixture. The isolated compartment is filled with air at 20°C....
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Vapor pressure in closed systems (2 and multiple components)

Hi there I am currently struggling to understand how vapor/liquid systems work in general. Specifically, I have two qualitative questions. Suppose we had a closed system, half of it filled with just ...
1 vote
1 answer
101 views

Does the vapor pressure of a substance depend on the presence of other gases?

The Clausius-Clapeyron equation (CC equation) can be used to find the (saturated) vapor pressure of a substance ie. the gas pressure at which the two phases (vapor + liquid or vapor + solid) reach ...
1 vote
1 answer
57 views

Why does Raoult's Law have a weighted sum instead of a direct sum?

I'm fully aware of the various questions asked about Raoult's Law, and I'm asking this after having gone through all of them and not finding a suitable answer to my question. I have studied, that at a ...
10 votes
4 answers
15k views

Reason for the formation of azeotropes

Why is it that some liquid mixtures (that exhibit positive/negative deviation from Raoult's law) form azeotropic mixtures at certain compositions? What is the physical reason behind this; are there ...
1 vote
0 answers
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Interpretation of azeotropes from statistical mechanics derivation

In an earlier posted question titled Reason for the formation of azeotropes, @porphyrin presented an elegant derivation from statistical mechanics to interpret partial pressures for the two components ...
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2 answers
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will mercury vaporize in boiling water in a flask?

Will mercury vaporize with the water vapours if boiled in a flask full of water? Also if we store mercury under water in the beaker will it still give vapours? If some mercury is bound to vaporize , ...
2 votes
1 answer
138 views

Is there a vapor pressure equivalent to freezing point?

Vapor pressure is where liquids are breaking off into the gas phase, below the boiling point. So is there a term where solids break off into the liquid phase, below the freezing point? Vapor pressure ...
1 vote
0 answers
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Saturated vapor and liquid densities (VLC curve) from Helmholtz free energy equation of state

I have been reading about the statistical associating fluid theory (SAFT) which computes the Helmholtz free energy ($A$) from the SAFT EoS (a hell lot of equations) for a molecule of interest, and is ...
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2 answers
535 views

What is the mass fraction of trichloroethene in the liquid phase using vapour pressure and mole fraction in gas phase?

Vapour-liquid equilibrium of a two-component ideal solution of trichloroethene ($\ce{C2HCl3}$) and trichloromethane ($\ce{CHCl3}$) is established at $\pu{25 °C}$. The mole fraction of $\ce{CHCl3}$ in ...
1 vote
1 answer
201 views

Do benzene and hexane form an ideal solution?

My teacher said that benzene and hexane do not form an ideal solution (with reference to Raoult's law) but did not explain any reason for it. My approach: Cyclic hydrocarbons (benzene here) have ...
0 votes
1 answer
57 views

Pressure increase in a chamber with 1 ml of water heated to 200 °C [closed]

For safety reasons I want to know how much pressure will be generated in a sealed chamber with $1~\mathrm{ml}$ of water, pure nitrogen at $1.3~\mathrm{bar}$ at $22~\mathrm{^\circ C}$. This chamber ...
13 votes
2 answers
138k views

How to calculate melting/boiling points at different pressures?

Is there an equation to calculate the melting or boiling points of elements or compounds at a given pressure? I know water boils below room temperature in a vacuum. I'd like to know if gallium, a ...
-1 votes
1 answer
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What is the ∆H_vap when temperature of a given liquid is equal to the boiling point of the liquid?

What is the $∆H_{vap}$ when temperature of a given liquid is equal to the boiling point of the liquid? For the other cases ie (i) T>BP, $∆H_{vap}$ > 0 (ii) T<BP, $∆H_{vap}$ < 0 So what ...
0 votes
1 answer
79 views

Data on Vapour Pressures of Silicone Oils [closed]

I am trying to find specific information on vapour pressure of silicone oils with different viscosities which I have used in some experimental work. Is there a chemical databook where this information ...
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Vapour pressure and boiling [duplicate]

I have come across two definitions for boiling point: It is the temperature at which a liquid gets vaporised It is the point where vapour pressure = external pressure How are they related? How does ...
1 vote
1 answer
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Why does boiling occur when vapor pressure equals ambient pressure?

Here is my understanding of the boiling process: pressure of the atmosphere is pressing down on the liquid and this pressure is propagated throughout the liquid. That is, pressure everywhere inside ...
4 votes
1 answer
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What gas was produced in this orbiting space-balloon from 33 pounds of benzoic acid and anthraquinone? Why these two chemicals?

As pointed out in this answer, on page 4 of NASA Technical Note TND-1366 The Orbital Behavior of the Echo I Satellite and its Rocket Casing During the First 500 Days (June, 1962) says: PHYSICAL ...
2 votes
1 answer
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Some salts lower the vapour pressure of water - do any raise it?

Plain old NaCl salt can slightly lower the vapour pressure of water for a given temperature. Other salts such as CaCl₂ lower the vapour pressure to a larger degree. Do any salts, or compounds of any ...
2 votes
0 answers
52 views

Can different components show different deviations from Raoult's law?

Introduction: Raoult's law is used to calculate the partial pressures of the vapour phases of volatile components of a solution Given that there are two components, A and B, in the liquid-liquid ...
0 votes
1 answer
131 views

Variation of vapour pressure with application of external pressure

Many times study of fact that with pressure of a substance only depends on the temperature and nature of the substance recently I study about dew point and bubble point. Then I came up with this ...
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52 views

How to sustain iodine vapor in a big container (V=200 L)?

I am lost in a quest on how to have a big container in which I can have iodine vapor at a known temperature. We intend send iodine into an air flow, and observe fluorescence of iodine in this flow. ...
1 vote
1 answer
130 views

In an open system, can water vapor escape into the atmosphere before reaching the boiling point? [duplicate]

In a closed system, water vapor would have nowhere to go and atmospheric pressure would not be a factor. It would reach dynamic equilibrium with only water vapor. But in an open system, I think that ...
4 votes
2 answers
366 views

Will addition of inert gas change the vapour pressure of a liquid?

From this question on Physics SE Thermodynamics of evaporation: Now imagine the experiment is repeated but instead of vacuum conditions, the water is pressurized with nitrogen at 1 atm. According to ...
1 vote
0 answers
39 views

Conditions for a substance to show deliquescent or efflorescent behaviour

I have learnt that deliquescent substances are the ones which absorb moisture from the surroundings and convert them to solution and efflorescent substances are the ones which release moisture into ...
0 votes
1 answer
100 views

What does water saturated oxygen mean? [closed]

What does water saturated oxygen mean in this question: The vapour pressure of water at 80º C is 355 torr. A 100 ml vessel contained water saturated oxygen at 80º C, the total gas pressure being 760 ...
-1 votes
2 answers
103 views

Why vapor pressure is unaffected by change in atmospheric pressure [duplicate]

I am a high school student and I am very confused in a topic about "vapor pressure of liquid". Why doesn't a change in atmospheric pressure affect vapor pressure? I think intuitively that ...
2 votes
1 answer
95 views

Partial pressure of gases in a container with a piston

I've been having problems with the following problem. Figure 1. A container with a piston like that shown in Figure 1 is filled with $0.10$ $mol$ of Ar and $1.00$ $mol$ of water (liquid and vapor). ...
0 votes
1 answer
1k 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%, ...
3 votes
2 answers
11k views

How much time liquid mercury takes to evaporate?

I asked before about a thermometer that I broke yesterday. To summarize, I broke a mercury thermometer in my bedroom, which is a place where is difficult to have sure that I get rid of all mercury, ...
4 votes
1 answer
186 views

Does pH gets affected by pressure? [closed]

My attempt- I thought that pH is h+ ion concentration and change in volume will change its equilibrium according to le chatelier's principle . But I want to know is it correct or it needs some ...
0 votes
2 answers
393 views

Antoine law and ideal gas law

I have the following question: A $100\ \mathrm{ml}$ sealed flask with $60\ \mathrm{ml}$ acetonitrile is heated to $140\ \mathrm{^\circ C}$. The boiling point of acetonitrile is $82\ \mathrm{^\circ ...
1 vote
0 answers
31 views

Which temperature would allow a molecule to vaporize at ultra-low pressure? [closed]

I must vaporize a molecule with a normal boiling point of 320°C. Now I work with ultra-high vacuum and I need to bring my molecule to the gas phase. Has anyone a rough idea how high the temperature ...
1 vote
1 answer
2k views

Mass of sugar that was added to the water (Raoult's law)

Water has a vapour pressure of $15.5~\mathrm{mmHg}$ at $25~\mathrm{^\circ C}$. An unknown amount of the non-volatile sugar glucose ($\ce{C6H12O6}$) is added to $1.31~\mathrm{kg}$ of water and the ...
2 votes
2 answers
2k views

How to calculate the vapor pressure of water?

$48~\mathrm{l}$ of dry $\ce{N2}$ passes through $36~\mathrm{g}$ $\ce{H2O}$ at $300~\mathrm{K}$, and this results in a water loss of $1.20~\mathrm{g}$. The vapor pressure of water is? The solution ...
2 votes
1 answer
9k views

How to arrange substances in order of increasing vapor pressure?

During the lecture in my chemistry class, my teacher posed the following problem: Arrange in terms of increasing vapor pressure: a) $\pu{0.5m}$ sugar b) $\pu{0.5m} ~ \ce{NaCl}$ c) $\pu{2m}$ ethylene ...
3 votes
1 answer
153 views

Relative humidity and vapor-pressure in equilibrium

I have quite an unclear understanding of relative humidity. I am writing my understanding on the topic and please correct me wherever I'm wrong: What I understood: Let's say $\ce{H2O}$ has a (...
3 votes
1 answer
106 views

Depression of the Freezing Point

Recently we learnt that there is a depression in the freezing point when a non-volatile solute is added to the solvent. Our teacher explained this phenomenon with a graph where the vapour pressure of ...
4 votes
1 answer
247 views

Can we compare the vapour pressure of solutions whose concentrations and temperature is known?

If we have some solutions, in which we know the temperature and concentration of the solute particles, can we compare their vapour pressures? Original question: Which solution has the highest vapour ...
0 votes
1 answer
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Does the composition of a solution keep changing when being boiled? [closed]

The mole fractions of the components of vapours aren't the same as those of the liquid-liquid solution (unless the solution is azeotropic), this implies a change in the composition of the liquid ...

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