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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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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132 views

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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662 views

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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52 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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621 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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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 ...
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152 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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174 views

Alternative to mercury bubbler for increasing boiling temp?

A common reaction for forming the octachlorodirhenate(III) anion is to heat tert-n-butylammonium perrhenate in benzoyl chloride at 209 ºC. If you look up the info for benzoyl chloride, one sees that ...
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77 views

Chemically generating a high vacuum?

Suppose I fill a vacuum chamber with 99% oxygen, then pull a vacuum on it down to 10 pascal absolute. If I then vaporize aluminum (for vapor deposition), will the aluminum bind with the remaining ...
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519 views

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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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) http://www....
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869 views

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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1answer
123 views

Is every substance in equilibrium with its vapours?

In one of my previous questions, I got an answer from user Jan: The smell of a compound as we perceive it usually depends on which receptors in the nose will bind the molecule (or not). These ...
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Algae Cultivation Using Polyethylene Film Reactor Vessel Floating In Pool with Algicidal ClO2 Concentration

I'm attempting to grow chlorella algae in a polyethylene film bag (which contains the growth medium) submerged in a temperature-moderating, above-ground swimming pool. This presents a challenge in ...
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49 views

How to find relative lowering of vapour pressure from phase diagrams in terms of temperature?

Problem Answer My question Does a tie rule exist for solution solvent phase diagram to express relative lowering of vapour pressure in terms of temperature? The phase diagram is the one ...
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45 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 coefficient: $$Θ = ...
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637 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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49 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 ...
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84 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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179 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 ...
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752 views

Predicting the vapor pressure of water ammonia solution

I am working on a project that involves the compressors for a vapor compression refrigeration cycle of R717 (ammonia) and came across something that has been boggling my mind a little bit for no good ...
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711 views

Rate of evaporation of mercury

A restorer of antique barometers reported in a blog post that he has had a barometer on his wall that has shown no "visible" loss of mercury in 15 years. I was kind of curious about this, wondering ...
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370 views

Identifying T1 and T2 in the Claperyon equation

Is there a way to identify T1 and T2 in the two point form of the claperyon equation? I suspect that the greater temperature is T1 and the smaller temperature is T2.
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108 views

how to find pressure of a liquid when given volume (1 and 2) and one pressure?

A 5 mL sample of an unknown liquid is placed into a 250 mL flask that has had all of the air removed. The pressure measured in the flask is found to be 35.4kPa. In a seperate trial the student puts ...
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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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1answer
117 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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44 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 ...
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28 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 ...
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How to compute the pressure potential of the fermentation of sugar into carbon dioxide?

I'm doing an experiment to ferment table sugar with yeast to capture the resulting carbon dioxide. Suppose I put $x$ grams of sugar in a closed 1 liter bottle with yeast. How can I compute the ...
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28 views

Is the evaporation (liquid to gas conversion) of ethanol dependent on how full you fill it up in a sealed bottle?

It seems intuitive to think that in a bottle (which is air-tight), if you fill up ethanol (or any other volatile liquid) to very full extent, thereby leaving very little headspace, the amount of ...
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17 views

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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28 views

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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85 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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55 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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612 views

Water vapor equilibrium calculations

The question had two parts. The first part said: Calculate the amount of water required to saturate a vessel of volume 82 L at 300 K given that the vapor pressure of water is 38 torr at 300 K. The ...
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121 views

vapour pressure above 2 separate beakers containing liquids which form ideal solution

Suppose we have A moles of liquid 1 in one beaker and B moles of liquid 2 in the other. Beakers are placed together in a biger closed container. Both have different vapour pressure when isloated. Now ...
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1answer
38 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 ...
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20 views

Vapour Pressure of solutions and mol fractions

From a solution (ideal) which contains the components A and B ,the vapours over the solution at a temperature T are collected and condensed into liquid and again brought to the same temperature T. ...
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1answer
776 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). ...
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1answer
106 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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696 views

Interpreting the phase diagram of a minimum boiling azeotrope

Exactly what does the line AB signify in the above phase diagram? Also, why is the curve divided at the azeotropic point?