# Tagged Questions

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.

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### Vapor pressure of immiscible liquids

I have read that vapour pressure of a mixture of two immiscible liquids is $$P=P^0_A + P^0_B$$ where A and B are immiscible liquids. My question is, if they are immiscible, they would form separate ...
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### Generalized enthalpy of vaporization for corresponding states

I'm interested in equations for substances at corresponding states that give general relationships between common chemical and physical properties. For example, the Guggenheim equation for saturation ...
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### Liquid phase stability..which is more stable at lab STP (25C and 14 psia) - Butane or Propane?

I know that propane has much lower boiling point that Butane (-43C compared to -1C), but I wanted to know which of these is more stable at room temp and pressure ? I would be keeping both in a Dewar ...
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### Control the pressure of Hydrogen in a small container without the use of a pressure regulator

I had recently asked this question, and due to the comments and general consensus of safety concerns, I decided to re-ask the question, attacking the problem from another angle. The Problem I need ...
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### Challenging modern formula to calculate molecular mass of solute from relative lowering in vapour pressure

According to modified form, $\frac{P-p}{p} = \frac{n}{N}$, where: $p =$ partial pressure of solution, $P=$ partial pressure of pure solvent $N=$ mole fraction of solvent $n=$ mole fraction of ...
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### Vapor-pressure or Vapor-concentration

To summarize from my textbook: rate of evaporation: proportional to surface area but essentially independent from pressure (of surrounding gas) rate of condensation proportional to both surface ...
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### What is the lowest temperature tungsten starts sublimating at?

What is the lowest temperature tungsten starts sublimating at? I've tried to search in Google but without any luck. For example, WO3 starts sublimating roughly at 550 Celcius degree, according to the ...
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### How is volatility useful in the production of acids?

Sulfuric acid because of its low volatility can be used to manufacture more volatile acids from their corresponding salts. How does volatility affect the production of acids? Isn't it that ...
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### Low temperature evaporation of EtOH in Propylene Glycol / EtOH mixture

If I have a mixture of approximately 90% Ethanol and 10% Propylene Glycol, but I am restricted to not allowing the mixture to reach above 40 degrees C, what is the best method to fully evaporate the ...
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### Calculating mass of water removed (vapor pressure)

I cannot figure out how to calculate the mass. "The question is: Suppose the percent relative humidity is 80.0% at 91.4 F (33.0 c) in a house with a volume 245m^3. Then the air conditioner is turned ...
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### Why don't the solute molecules in a volatile solvent also escape to contribute to vapor pressure?

I'm currently studying relative lowering of vapor pressure with the addition of a solid non volatile solute. The book explains it with the notion that some of the non volatile solute also appears at ...
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### Colligative properties

I have some problems with these properties. 1) Lowering vapor pressure and boiling point. It happens because the solute molecules take space in the surface of the liquid so a lower number of the ...
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### Vapor Pressure - Sealed Vessel

I have read that vapor pressure is only affected by temperature, but all of the examples have been in a sealed vessel. I have also read that pressure does not affect vapor pressure. I am looking for ...
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### Boiling point and vapor pressure

Does a liquid having higher vapor pressure have a lower boiling point? I think so because I read in wikipedia that, "A substance with a high vapor pressure at normal temperatures is often referred to ...
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### Why azeotropes boil at constant temperature?

I understand that for an Azeotrope the composition remains same for both the liquid and vapour phase, and it is not possible to distill out a component from it. What I don't understand is why it is ...
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### When water boils at its boiling point how do we call it as an equilibrium?

On boiling, water becomes a vapor, liquid volume decreases and vapour volume increases. Since volumes are not constant, how do we call it as equilibrium?
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### Highest ratio of ethanol to propylene glycol in a solution to still have minimal evaporation under ambient conditions? [closed]

How much ethanol can be added to propylene glycol before significant evaporation would start?
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### Raoult's Law and Mole Fraction

Raoult's Law states that the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the ...
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### Rocket propellants: accuracy of vapor pressure estimation techniques

I would like to determine the vapore pressures of a couple of substances (rocket propellants) over a significant temperature range within a ~10% error margin. For a first test, I tried to ...
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### What is the connection between vapor pressure and intermolecular force explanations of boiling?

I've had boiling explained to me in two ways, and I'm having trouble understanding how they connect. The first way is that a liquid is held together by the intermolecular forces, and boiling involves ...
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### Is menthol an especially volatile molecule?

I have been studying a bit about odors and plant essential oils. Several sources claim that the fragrant terpenes found in these oils, such as menthol, eugenol, limonene, linalool, etc. are volatile ...
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### Why does melting point depend on external pressure?

The melting point of a substance is the temperature at which the solid form's vapor pressure equals the liquid form's vapor pressure. I read that the vapor pressure of something depends ONLY on the ...
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### How to calculate the total pressure in this question?

Here is the question: A container at $78\ \mathrm{^\circ C}$ initially contains $\ce{AB(g)}$ in equilibrium with $\ce{AB(l)}$: $$\ce{AB(l) -> AB(g)}$$ A catalyst (of negligible ...
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### What is the mass fraction of C2HCl3 in the liquid phase?

Vapour-liquid equilibrium of a two-component ideal solution of trichloroethene (C2HCl3) and trichloromethane (CHCl3) is established at 25 Â°C. The mole fraction of CHCl3 in the vapour phase is 1. What ...
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### 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 ...
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### Calculate the mole fraction of component B in this solution? (partial pressures)

The vapour pressure of a pure liquid solvent A is 0.80atm. When a non volatile substance B is dissolved in teh solvent, its vapour pressure drops to 0.60 atm. Calculate the mole fraction of component ...
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### Does storing a hygroscopic reagent in a bottle makes it prone to absorb humidity from the air trapped inside?

I've got a full bottle of 99,5% acetone, which I'd really like to keep it as dry as possible, though without using molecular sieves or other dessicants. Once I open the bottle for the first time, use ...
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### Is every substance in equilibrium with its vapours?

In one of my previous questions (How are odor and electronic structure related to aromaticity?), I got an answer from Jan: The smell of a compound as we perceive it usually depends on which ...
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### A question about vapor pressure and boiling point

Question 1: If we have an open container which has water in it and is heated. If there is no lid over the container then how can this water ever boil as there will be no vapor pressure created over ...
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### Get the molar fraction given the vapor pressure of a dissolution

If a dissolution has a vapor pressure of $24.4\rm{torr}$ and the vapor pressure of the pure dissolvent is $25.5\rm{mmHg}$, what is the molar fraction of the solute? Well, I just have to solve ...
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### Minimum amount of water in pressure cooker

When cooking I would like to know the minimum amount of water I can add to my 6.2 L pressure cooker, worst case, so without any food. At second ring cooking the pressure is 0.8 bar. I assume I need ...
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### Why does cooking oil lower the vapor pressure of water?

I added different amounts of oil to different containers with 50mL of water and weighted the containers. Then I heated the containers for 15 minutes in a water bath and weighted again. I noticed that ...
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### Total pressure in a chamber calculation

I have a chamber containing two different gases and a liquid which needs to be heated at a certain temperature to bring it to vapor state. I have worked out that we can calculate the total pressure ...
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### Relating 'temperature' difference to 'vapour pressure'

I am aware of the fact that with the increase in temperature, the number of molecules with more kinetic energy increases and thus, the vapour pressure increases. When we increase the temperature ...
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### Relationship between vapour pressure and saturated vapour pressure

I need clarity on saturated vapour pressure in a closed system at equilibrium. How does saturated vapour pressure relate to vapour pressure?
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### What happens when heating water in a pressure vessel?

Suppose that I take a pressure vessel that can withstand up to 2000 PSI. Now I fill it with water (not completely, but around 90%) and start to heat it with a direct flame. What I want to know is, ...
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### Using vapor mole fraction and pressure to determine liquid mole fraction

I am studying Chemistry by Zumdahl and Zumdahl (9th edition) and I have come across a question in Chapter 11 that I can't figure out the explanation for: Liquid A has vapor pressure x , and liquid B ...
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### Is dew and water vapour the same?

Is it possible to say water vapour and dew is the same? I know that the water vapour is the gaseous phase of water. But what is the dew? I just wonder how can I categorised it. Is it the liquid or ...
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### what is the relation between partial pressure and vapour pressure? [duplicate]

I've read about Raoult's Law, and Henry's Law. So I wanted to know whether there is any relation between partial pressure and vapour pressure? As partial pressure is directly proportional to the mole ...
3k views

### The effect of air pressure on the “melting point”?

a) No effect b) The melting point increases when the air pressure increases c) The melting point decreases When the air pressure increases The boiling point has inverse relation with ...
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### Unable to comprehend graph of aqueous lithium bromide vapour pressure

$\ce{LiBr}$ $Vp$ chart: http://www.mediafire.com/view/x77zc8wj11gthsj/LiBr_Vp.jpg or http://www.mediafire.com/view/u4dnocvbsf3atmu/Useful_Chart_LiBr.pdf Lecture in question (p.13) ...
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### How does composition of air affect vapor saturation limit?

Suppose we hold temperature, pressure, and gas composition (say, a standard atmosphere) constant. Then we know that if we allow the water content of the air to vary it can range between 0 and some ...
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### How can I turn natural gas from liquid to gas?

I hope I am not too off topic. I couldn't find a more suitable stack-exchange site for this, so if there is a better one, please point me to it. My question is the following: I am working on a ...
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### What is the reason for this azeotrope formation?

What is the reason for the formation of an azeotrope? I mean why with certain compositions, one component alone cannot go to vapour phase. Is there any extra force holding the two components together? ...
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### Finding Kp at another temp with /\Hrxn [closed]

Took a pic of the paper I tried it on it on, has the exact problem description written at top, and what I tried. Figured that would be easier then typing all that. The answer is supposed to be 2.0.
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### Applying Raoult's Law to a condensed gas mixture

So, here's the question which I'm having trouble solving : Suppose that we condense a gas mixture. At 25 celsius, what will be the pressure of benzene and of toluene over the obtained liquid. We ...
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### How are pressure vessels heated?

I'm working on a project in which I'll be dealing with pressure vessels. As of now I've drawn/conceptualized everything on theory basis. The diagrams are made on the basis of theory, but then I came ...
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### Pressure over a solution

I was wondering something, if I have the same molar fraction for two different substances for a vapor on top of a solution, will this mean that the pressure of each individual substance will be the ...
$48~\mathrm{l}$ 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 ...