Questions tagged [phase]

An entity of a material system which is uniform in chemical composition and physical state. This tag should be applied to question regarding chemical and physical properties of phases, systems of phases and also phase transition processes.

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41 views

can a vapour denser than air evaporate in a closed chamber? [closed]

Imagine a closed container filled with air. There is some liquid substance on a bottle placed on the floor of the container. Let's heat the liquid until it starts to evaporate. Let's say 20% of the ...
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Interpreting phase diagram of mixture of partially-miscible liquid that boils before complete mixing

Source: Atkins' Physical Chemistry, 8th Edition, P.188 This is an example given by the stated reference book. Interpretations on this phase diagram is given. An extract of the interpretations is ...
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Formulation chemistry. Can somebody suggest me an introductory book on this subject? [duplicate]

I am looking for an introductory book on formulation chemistry: the book should cover physico-chemical aspects in designing a formulation and also, if possible, the chemometric basic concepts used in ...
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Does toxicity depend on state of matter? [closed]

Does the toxicity of an element depend on the state of matter (liquid, solid, gas)? Could there be an element, which is totally non-toxic when it is solid, but toxic when it is liquid. Which elements ...
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Is ethane or carbon dioxide easier to liquify? [closed]

Let's say $\ce{CO2}$ and $\ce{C2H6}$ are both in gas form, not vapour. Now which one will be easier to liquify? My take is that the molecule of $\ce{C2H6}$ should be much larger than $\ce{CO2}$ and ...
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Why can't Carbon Dioxide be liquid at 1 atm?

Wikipedia says that Carbon Dioxide cannot be liquid under atmospheric pressure. I thought the phase of an element was related to both pressure and temperature. If that is so, then should you not ...
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Liquid neon freezer?

Liquid nitrogen is approximately -330 degrees Fahrenheit. Liquid neon is approximately -413 degrees Fahrenheit. I want to know about if this type of freezer is easily possible in practice and if such ...
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1answer
79 views

Is there a phase diagram available for hydrogen fluoride?

Has a phase diagram for hydrogen fluoride been published in an article on the internet or in a book ? Or is there a table for HF for different pressures up to 100 atm. and temperatures up to 500$⁰$ C ...
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Is the active mass of every solid and liquid taken to be unity?

I learnt from my textbook and the question/answer - Why is active mass of a pure solid or liquid always taken as unity? that active mass of a solid or liquid is taken to be unity as: $$[A]=\frac n V=\...
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Difference between a species and a phase in a solution? [closed]

Overview: As of my knowledge from metallurgical thermodynamics a phase is a thermodynamically stable and homogeneous entity made up of different species of a given concentration. e.g = 'Austenite' ...
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Is kinetic energy proportional to temperature for non-gases?

If the molecules in a sample of ice at $\pu{-15 °C}$ and $\pu{1 bar}$ all have their kinetic energy doubled, then what is the final phase? The answer is gas, but I am not sure how to get this answer. ...
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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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Isothermal transforamtion diagram - Austentite [closed]

A steel alloy is rapidly cooled to $\pu{600^oC}$, held for $\pu{4 sec}$, rapidly cooled to $\pu{450^oC}$, held for $\pu{10 sec}$ and quenched to room temperature. What phases are produced? Why is ...
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What is the mass fraction of C2HCl3 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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1answer
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Why does eutectic point has three phases, but consolute point has two phases?

At eutectic point, there are three phases: solid A, solid B and homogenous liquid phase containing both A and B. But at consolute point, we are told it has 2 phases: liquid A and liquid B. Why isn'...
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Why when deriving the Clapeyron equation can you assume that dH = dq, as surely the pressure is not constant?

Part of the Clapeyron equation involves replacing $\Delta S$ with $\Delta H/T$. I can see the step from $\Delta S$ to $\Delta q/T$ but I'm not sure why you can replace $\Delta q$ with $\Delta H$. From ...
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1answer
185 views

How is a phase equilibrium defined for a one-component system?

A question on this site asked whether a one-component system is at equilibrium when melting or boiling, and the disparate answers were somewhat dependent on the definition of phase equilibrium. ...
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228 views

melting and boiling …really equilibrium? [closed]

Why are melting and boiling considered equilibrium processes even though the amount (concentration) of both phases keep changing i.e from solid to liquid and so on?
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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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1answer
85 views

Vapor pressure vs. ambient pressure

I've managed to get myself thoroughly confused in thinking about the vapor pressure of a substance at a particular temperature $T$, and how it relates to the pressure of the substance if it is in a ...
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454 views

Is oxygen above the critical point always supercritical fluid? Would it still appear to roughly follow the ideal gas law?

In this answer I've asserted (without a "Chemist's license") that as long as oxygen is above it's critical point in both temperature (154.5 K) and pressure (50.4 bar) it's going to be a supercritical ...
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How does solidification occur? [closed]

What does it mean that "When vapor pressure of solid is greater than liquid, there is a net conversion from solid to liquid". What exactly occurs in the process of solidification of liquids?
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Why do phase changes occur? [closed]

So I was doing a Gizmo for my Science class and I came across this question: "Why do phase changes occur?" I could not find anything about it in my resources. Does anybody here know the answer?
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How to find the Cp, difference of Cp and heat of fusion from the dependence of vapor pressure on temperature?

The vapor pressure of zinc varies with temperature as $$\log P(\pu{mm Hg}) = -6850/T - 0.755\log T + 11.24 \label{eqn:1}\tag{1}$$ and that of liquid zinc as $$\log P(\pu{mm Hg}) = -6620/...
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How to I find the equilibrium temperature in this problem?

From Castellan's Physical Chemistry, chapter 12 [1, p. 276]: 12.18 At $\pu{25 °C}$ we have for rhombic sulfur: $ΔG_\mathrm{f}^\circ = 0,$ $ΔS^\circ = \pu{31.88 ± 0.17 J K-1 mol-1};$ and for ...
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1answer
92 views

What happens when a super-critical fluid is compressed?

Suppose that I have some substance with a critical temperature of 20°C. That means above that temperature, the substance exists neither as a gas nor a liquid, but instead as a super-critical fluid. ...
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Why are the phase diagrams showing $G_s$ and $G_l$ situated so close on one end and then widens up at the other extremes? [closed]

With reference to the phase diagrams drawn in b and d why are the Gibbs phase lines coming closer from being so further apart?
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What is the degree of freedom of the calcium carbonate dissociation reaction?

Question $\ce{CaCO3}$ dissociated in a closed system according to the reaction: $$\ce{CaCO3(s) -> CaO(s) + CO2(g)}$$ Assuming the reaction is in thermodynamic equilibrium, what is/are ...
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1answer
63 views

How to prove it mathematically that either rhombic or the monoclinic sulfur is denser?

For the transition, rhombic sulfur → monoclinic sulfur, the value of $ΔS$ is positive. The transition temperature increases with increase in pressure. Which is denser, the rhombic or the monoclinic ...
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59 views

Diffusion between phases based on chemical potential

How is the concept of diagram(b) different from that of (e) and (d) from (f)?Someone told me in one of my earlier posts (Why will A atoms diffuse from β phase to α phase and B atoms from α phase to β ...
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What is the reason for phase separation? [closed]

I have seen phase separation as a phenomenon taking place. However I do not understand why this phenomenon occurs as a counter example to the natural laws of diffusion along the concentration gradient....
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How Would A Vast Mixture (Like an Ocean) of Ammonia-Water Behave in Terms of Evaporation and Freezing?

First, I'll go ahead and say I'm not very versed in chemistry. My question comes from my interest in planetary-sciences, specifically the speculation that there are likely exoplanets and moons with ...
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Phase Diagram-Fe-C, and TTT: Hardness Scale

So far I know that the Hardess scale of these materials is this: Martensite> Bainite> Perlite > Cementite> Ferrite Where is Austenite along this scale? I know that Cementite is harder than Austenite....
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What do the horizontal lines in a P-V phase diagram mean?

I have been studying phase diagrams of pure substances, and for a substance such as carbon dioxide for example, it's diagram looks something like this: The horizontal lines in the liquid phase puzzle ...
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What's the definition of multi phase materials? Does it mean the different phases represent different materials?

I'm from a CS background and just trying to understand the real meaning behind multi phase materials. Following is the experiment which drove me towards this question. With the help of DFT and ...
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1answer
120 views

Is it possible to have only liquid in a closed container?

I recently read an answer by Aman Rusia for this question: Is a liquid in a container always in equilibrium with its vapour? In it, they say that You can't have a container filled with only ...
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How are phase transition diagrams calculated?

How are diagrams such as above plotted? Since empirical studies are slightly off from the 'ideal', what is the source for the phase plots?
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Energy absorbed by a system in isothermic process in which the phase changes from liquid to gas

A system contains $x$ mole of material, with surface area $S$ is pressed by a mass $M_1$ (no fraction and no any other outer forces involves). Let $\Delta H_\mathrm{l\rightarrow g}$ be the transition ...
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146 views

Why does ordinary water have a triple point?

Triple points and triple lines for pure substances and mixtures My understanding is that pure substances can have triple points. But mixtures of substances have triple lines, i.e. there isn't a ...
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161 views

Freezing point of solution

It's stated in my textbook that at the freezing point, the vapour pressure of the solid phase equals the vapour pressure of the liquid phase. In a mixture, since the vapour pressure of the solution is ...
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1answer
104 views

Boiling point of liquids [closed]

If we can have liquid - vapour equilibrium at any temperature what is the 'point' behind boiling point.Boiling point is just a special case of liquid - vapour equilibrium where partial pressure equals ...
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285 views

Determine direction of mass transfer

For part a) I don't really know what to look at. Diffusion occurs from low to high concentrations so by looking at $t_1$ I would say that the direction of the mass transfer is from phase II (organic ...
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Can we estimate if a substance will be in gas state at certain temperature?

Sometimes, by ballparking, we can estimate that a certain substance isn't in the gaseous state at room temperature because it has a large molecular weight. There is a direct relation between ...
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1answer
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Predicting pressure inside a container based on temperature

I'm a mathematician and computer scientist, and for this particular problem I would benefit from some chemical expertise. Suppose I fill a container up with some liquid propane. I believe this is ...
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Which “exotic salt” can lower water's freezing point by 70 °C?

The Medium.com article Mars Phoenix Lander, 10 Years Later shows several remarkable images and discoveries on Mars by the Mars Phoenix Lander circa 2008. One image (shown below) shows what looks like ...
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When it rains, it puddles. Spilled salt cycles between wet and dry with humidity. Is this akin to a phase change?

I have some spilled un-iodized table salt (NaCl). It is very humid where I live, and when it gets very humid for a few days, the salt absorbs so much water that it becomes a puddle of (probably) ...
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86 views

How to calculate dew point of air-water system

I want to calculate the maximum water holding capacity of air at a given temperature (as in $\frac{max\ mass\ of\ water}{mass\ of\ dry\ air} $ vs temperature) I looked up online and there are ...
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What happens when para-water ice is suddenly melted?

Background (hydrogen) In the case of recently liquified hydrogen (which is quite cold of course) it must be re-equilibrated before loading on to a rocket as fuel to avoid a sudden exothermic ...
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Use a solid or liquid stationary phase in gas chromatography

In my textbook, they mention that the stationary phase used in gas chromatography is a solid, such as silica or an adsorbed high-boiling-point liquid. My question is that what is the advantage of ...
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Can amorphous polymers have a melting temperature as well as their glass transition transition temperature?

Above the Tg, amorphous polymers are described as viscous liquids. What then would they be likened to above their melting point, should they have one?

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