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.
236
questions
0
votes
0answers
23 views
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
1answer
67 views
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 ...
2
votes
1answer
71 views
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
0answers
42 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
1answer
57 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
1answer
43 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 ...
0
votes
0answers
49 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
1answer
105 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 ...
0
votes
0answers
92 views
Relation between vapour pressure and boiling point
In my childhood I was very happy with the following definition of boiling point
The temperature at which a substance changes from liquid phase to gaseous phase is known as boiling point.
But with ...
1
vote
0answers
35 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 ...
-1
votes
2answers
53 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 ...
0
votes
1answer
73 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 ...
4
votes
1answer
71 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 ...
1
vote
0answers
30 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 ...
4
votes
2answers
181 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 ...
3
votes
1answer
68 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 (...
2
votes
1answer
57 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). ...
3
votes
1answer
117 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
1answer
53 views
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 ...
15
votes
6answers
4k views
What is the difference between "vapour" and "gas"?
I have read the definition of vapour on Wikipedia, but I don't seem to have a clear idea about the difference between a vapour and a gas. I know what it means when it says, "gas at a temperature ...
3
votes
1answer
326 views
To calculate total vapour pressure of a solution
Question:
1 mole each of A and B were mixed to obtain an ideal solution of which one mole went to the vapour phase at equilibrium.
If $P°_\mathrm{A} = \pu{100 torr}$ and $P°_\mathrm{B} = \pu{900 torr}$...
-1
votes
1answer
45 views
Why doesn't relative humidity tend to 100%?
Relative humidity is defined as:
$$\frac{\text{pressure of $\ce{H2O}$ vapours}}{\text{vapour pressure of $\ce{H2O}$ at that temperature}} \times 100$$
Suppose the temperature is fixed and I apply Le ...
2
votes
0answers
31 views
Why does refrigerant condense in oil?
In a closed system (think of a typical AC system) why does refrigerant tend to condense and settle in oil?
I’ve heard that the vapor pressure of the oil is very low so that causes a pressure ...
3
votes
1answer
76 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 ...
0
votes
0answers
20 views
Is saturated vapor pressure equals to saturated vapor partial pressure?
I got confused for this two things, the first pressure is the pure water vapor in a certain temperture, and the second vapor partial pressure is the water vapor existed along with other gases, so my ...
1
vote
0answers
35 views
Does aqueous ammonium fluoride solution release hydrogen fluoride vapors?
Can $\ce{HF}$ vapors be released from $\ce{NH4F}$ solution in water $(w(\ce{NH4F}) = 40\,\%)$ at room temperature?
I assume that dissolving $\ce{NH4F}$ in water produces small amount of $\ce{HF}.$
-1
votes
2answers
244 views
What affects the vapor pressure of a pure liquid? [closed]
So pretend we have two samples of pure benezene in equilibrium with its vapor. One sample containing 0.5 mol and one containing 1 mol. They're also both at the same temperature. Let's pretend they're ...
1
vote
1answer
73 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 ...
0
votes
1answer
60 views
XSteam IF97 tables (MS Excel version) lack of inputs [closed]
I am using XSteam IF97 to evaluate steam power plant cycles.
However, I miss some important input options such as pressure as a function of entropy and temperature ("p_st()") - when I assume ...
5
votes
1answer
348 views
Why exactly does high pressure (72 bar) nitrous oxide's pseudocritical¹ temperature drop so far when oxygen is added to make 50%v/v mixture? (Entonox)
This answer to Can precipitation occur in states of matter other than liquids? mentions the unusual case of Entonox.
The effects of temperature on nitrous oxide and oxygen mixture homogeneity and ...
2
votes
0answers
26 views
Working out energies of hydrogen bonds by comparing chemical potential of vapour and condensed phase - equation derivation
I want to ask a question about working out the energy of a hydrogen bond between two water molecules, $w_{AA}$ using the chemical potentials of vapour and condensed phases.
I was reading K. Dill, ...
0
votes
1answer
30 views
opening valve separating two volatile solutions [closed]
Let there be two containers A and B containing two volatile solutions (ideal) of pure liquids P and Q respectively. The containers are connected by a tube such that only vapours can travel through ...
0
votes
2answers
230 views
Why is water transferred from a beaker of pure water to a beaker of sugar solution when placed in the a closed container?
I know that there is something to do with the vapour pressure of pure water being higher than the vapour pressure of the sugar solution, but I still can’t really explain what happens on a molecular ...
0
votes
3answers
409 views
Why does Vapor Pressure decrease on addition of solute? [duplicate]
Consider a vessel with a volatile liquid in it. Let's say it has a vapor pressure $P^0$ when it is pure.
Now a non-volatile solute is added to it. Its vapor pressure decreases as $P^0\chi_{solvent}$.
...
0
votes
1answer
324 views
When is Raoult's Law valid for solid-liquid solution?
Raoult's Law for solid-liquid solution is stated as such in my books that it is applicable for all non-volatile solutes.
However different solutes must have different attractive or repulsive forces ...
-2
votes
1answer
73 views
How do i experimentally determine the vapour pressure of a solution? [closed]
So i wanna dissolve different salts in water and measure the vapour pressure of the resulting solution. I am doing this to compare the freezing point depression of different cations, used with the ...
0
votes
1answer
543 views
Why is the temperature graph sigmoidal in simple distillation of components with very different bps?
I'm writing an organic chemistry lab report on distillation and I thought I understood this, but the more I look at my lab textbook, I realize I don't. My textbook 1 explains that the temperature of ...
0
votes
0answers
81 views
Why is vapor pressure constant at boiling point?
At non-boiling point, I understand that when you add heat, temperature increases and also the amount of gas increases, so by using $PV=nRT$ at constant volume, the increase in $n$ and $T$ would ...
5
votes
1answer
688 views
Detailed kinetic explanation for vapor pressure reduction by dissolved solute?
The following problem was asked in JEE Mains 2020 (Sept 2, Shift 1),
An open beaker of water in equilibrium with water vapor is in a sealed container. When a few grams of glucose are added to the ...
1
vote
0answers
41 views
Calculating the number of volatile molecules in a container of known volume [closed]
Is it possible to calculate the number of volatile molecules (so only those in the gaseous phase) in a container of known volume, if the vapor pressure of the compound is known? So for example, if you ...
3
votes
1answer
45 views
Vapors of Aqueous solutions
I'm dealing with a common photoresist developer TMAH (tetramethylammonium hydroxide) and attempting to design a vapor sensor for a sealed chamber. Now I havent been able to confirm what exactly is ...
0
votes
0answers
32 views
The minima of minimum boiling azeotropes
This is a very basic doubt, so I'll be really brief about it. The discussion I raise is particularly about minimum boiling azeotropes but it's understood that whatever I ask is about the general ...
2
votes
1answer
176 views
Vapour pressure and Raoult's Law
The following question from my textbook assignment reads
A mixture contains $1$ mole volatile liquid $A$ ($P_\mathrm A^\circ = \pu{100 mmHg}$) and $3$ moles of volatile liquid $B$ ($P_\mathrm B^\circ ...
3
votes
1answer
458 views
At what composition is Maximum deviation from Raoult's law observed?
Raoult's law states that in an ideal binary solution of two volatile components, the partial vapour pressure of each component is proportional to its mole fraction in the solution.
A plot of total ...
1
vote
0answers
41 views
What limits supersaturation in the absence of nucleation sites? [closed]
Imagine a scenario where we have a chamber with air that is supersaturated with water vapour. In this ideal scenario there are no nucleation sites (e.g no suspended particles or nucleation on the ...
0
votes
1answer
100 views
Latent Heat, Vapor pressure and Equilibrium [duplicate]
So after reading about this topic i wanted to share what i learned and i wanted you guys to tell me if what i am writting is correct:
A pressure vessel has propane inside and it is pressurized. The ...
0
votes
1answer
51 views
Relative humidity at constant temperatures [closed]
It’s known that Relative humidity = (water pressure in a certain volume/ saturated water pressure in the same volume)* 100% “at the same temperature”
So my question is why does the amount of water ...
2
votes
0answers
88 views
Measuring vapour pressure in a closed system
My experiment requires the determination of vapour pressure from which I will calculate the number density (or number of moles of the molecule) later, for a closed system.
Here's my setup :
Liquid ...
1
vote
2answers
66 views
Shouldn't the pressure of gas above a liquid slightly decrease when some of its molecules dissolves in the liquid? [closed]
Lets say a liquid and gas above are in equilibrium.
(1) Now if I suddenly increase the pressure of the gas it will take some time for some molecules of the gas to enter the liquid and get dissolved. ...
-1
votes
1answer
171 views
Cross checking the fact that gas solubility decreases with temperature increase and Henry's law's validity
It is known that the solubility of gas decreases with increase in temperature which is due to the kinetic energy freeing the solute particles into the vapor phase. Henry's law states that the partial ...
