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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6k 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, ...
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1answer
65 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 ...
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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 ...
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250 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 ...
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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 ...
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2answers
133 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 ...
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1answer
58 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 ...
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1answer
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 ...
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2answers
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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 ...
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1answer
8k 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 ...
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1answer
51 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 (...
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1answer
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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 ...
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1answer
50 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). ...
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1answer
102 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 ...
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4answers
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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 ...
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1answer
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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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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 ...
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1answer
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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 $P°_\mathrm{B} = \pu{900 torr}$...
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2answers
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Why is latent heat of vaporization not exactly proportional to boiling point?

Latent heat of vaporization and boiling point are both chemical properties related to the bond strength of the molecule. In general, the higher the boiling point is, the higher the heat of ...
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1answer
42 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 ...
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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 ...
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1answer
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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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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 ...
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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 $\ce{HF}.$
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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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2answers
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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 ...
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1answer
59 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 ...
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1answer
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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 ...
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3answers
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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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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, ...
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1answer
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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 ...
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2answers
201 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 ...
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3answers
309 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 $P^0\chi_{solvent}$. ...
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1answer
189 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 ...
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1answer
420 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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1answer
58 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 ...
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0answers
75 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 ...
4
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1answer
656 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 ...
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1answer
43 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 ...
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0answers
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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 ...
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4answers
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Is vapour pressure of a liquid solution constant at a given temperature, no matter the size of closed container and amount of liquid taken?

Does vapour pressure of a liquid solution depend on the size of closed container, amount of solution taken, given that, temperature is kept constant? Or will it change, if some extra gas is added to ...
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1answer
361 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 ...
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1answer
143 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 ...
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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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4answers
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General rules for deciding volatility

Given an organic compound, is there any way to decide if it is volatile (or compare volatility--everything is volatile in the end)? Volatility is due to the tendency to evaporate. The conclusion I ...
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1answer
166 views

Vapour Pressure of A Solution

I study in class 12, and have a doubt in vapour pressure that my school teacher and my friends are not able to clarify. My doubt is the reason why the partial vapour pressure of each individual ...
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0answers
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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 ...
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1answer
98 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 ...
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1answer
44 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 ...
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0answers
83 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 ...

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