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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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How do they come up with a freezing point of ~-60F for CaCl2 & H20?

What am I missing? I cannot reconcile the difference between what the internet says the freezing point of CaCl2 is vs the calculation, which means my calculation must be off, but I am not sure how. ...
4
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2answers
202 views

Ice Crystal Matrix measurements of H2O molecules?

I want a mathematically generated 3D STL copy of this image, however it's represent algorithmically. If I do all the H2O's as individual pieces with female connections prepared for chopped bike ...
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0answers
100 views

Can every liquid pure substance be compressed to solid?

Apart form the fact that liquid are often misleadingly considered incompressible, fact that I recently find out to be true only as an approximation in specific circumstances. I was curious to know if ...
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2answers
819 views

If melting points and freezing points are the same, what state is pure equilibrium?

If melting points and freezing points are the same, what state is pure equilibrium? I understand melting points and freezing points are the same; adding or removing temperature of melting points for ...
3
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2answers
62 views

Effect of doubling kinetic energy on phase transitions

The kinetic energy of the molecules in a sample of $\ce{H2O}$ in its stable state at $ \pu{–10 ˚C}$ and $\pu{1 atm}$ is doubled. What are the initial and final phases? [US National Chemistry ...
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1answer
71 views

Colloids and Ions

Suppose I have this reaction: $$\ce{3NaOH(aq) + FeCl3(aq) → 3NaCl(aq) + Fe(OH)3}$$ My questions: $\ce{Fe(OH)3}$ doesn't have the (aq) suffix because it isn't separated in water as opposed to $\ce{...
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0answers
113 views

Why does CO2 only exist in gaseous and solid state under STP/SATP?

Why does carbon dioxide only exist in gas and solid state under STP/SATP conditions? $\ce{CO2}$ pressurized to $\pu{5.1 atm}$ can exist in all 3 states: solid, gas, and liquid. However, why couldn't ...
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1answer
204 views

Interpreting from phase diagram whether O2 will float or sink

The normal melting and boiling points of $\ce{O2}$ are $\pu{-218 ^\circ C}$ and $\pu{-183 ^\circ C}$, respectively. Its triple point is at $\pu{-219 ^\circ C}$ and $\pu{1.14 Torr}$, and it's critical ...
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1answer
82 views

Can I supercool and solidify a liquid multiple times?

Let's say that I supercool a bottle of beer and then tap it so it freezes and solidifies. If I were to allow the frozen beer to melt completely, and then freeze the same bottle again, would it still ...
3
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1answer
38 views

Is supercriticality dependent on partial presssure, or total pressure?

Supercritical CO2 is commonly used as a solvent in organic chemistry (notably in industrial processes like decaffeination). I presume that in such cases, the CO2 is typically pure, or very close to it....
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2answers
381 views

Water cooling by evaporation

For many years of drinking water has been cooled in hot climates by evaporating it from the surfaces of canvas bags or porous clay pots. How many grams of water can be cooled from $\pu{35 ^\circ C}$ ...
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1answer
164 views

Lever rule confusion

At point a3, I know the ratio of the liquid phase to the solid phase, but I don't get the highlighted statement which says b3 gives the composition. I thought a3 already gave the composition? Do I ...
2
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2answers
211 views

Given this liquid-liquid phase diagram, is the green line the nitrobenzene-rich phase?

The temperature-composition diagram for hexane and nitrobenzene at 1atm. The region below the curve corresponds to the compositions and temperatures at which the liquids form two phases. The upper ...
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3answers
766 views

If hydrogen bonds are chemical bonds, and these bonds are broken when water changes phases, why doesn't this classify as a “chemical” change?

This is more of a terminology question. How are phase changes considered a physical property, not a chemical property when hydrogen bonds break. A chemical property can only be observed during a ...
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0answers
204 views

Why droplets of water and ethyl alcohol solution freeze weirdly? [closed]

I'm doing a project where I freeze water drops and solutions with water and ethyl alcohol. It's a phenomena where drops create a conical shape at the end of their freezing. But with ethyl drops, with ...
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2answers
314 views

What is the Difference between Menthol Crystal and Menthol Powder?

I want to buy menthol powder from a chemical supplier but he is selling menthol crystal at half price of menthol powder (he says manufacturing process is the difference) so I am really confused what ...
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0answers
53 views

Can the experimental mole fraction equal one?

I recently did an experiment on the temperature dependence of phase equilibrium acetone $\ce{C3H6O_{(l)}} \to \ce{C3H6O_{(g)}}$ I'm at the stage where I need to find the experimental mole fraction $\...
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0answers
33 views

Do all supercritical fluids dissolve the same substances?

In the case of regular fluids, polar solvents dissolve polar molecules and nonpolar solvents dissolve nonpolar molecules. Is there something analogous for supercritical fluids? In other words, does ...
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5answers
5k views

How does water evaporate completely when at room temperature?

If water evaporates at room temperature because a small percentage of the molecules have enough energy to escape into the air, then why does a kitchen counter with a small amount of water eventually ...
3
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0answers
29 views

What dynamical features allow for the existence of a liquid-liquid transition?

Recently it has been shown theoretically[1] and then experimentally[2] that a liquid-liquid transition (LLT) takes place in pure supercooled water. That is to say, two distinct liquid phases have a ...
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1answer
2k views

How much energy is needed to convert 20.0 grams of water at 15.0 degrees C to steam at 100.0 degrees C? [closed]

How much energy is needed to convert 20.0 grams of water at 15.0 degrees C to steam at 100.0 degrees C?
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2answers
869 views

What is the physical state of a single atom?

Can a single atom on its own be either a solid, liquid, or a gas? Or is it none of them?
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1answer
393 views

Effect of pressure on the freezing temperature of water

A few lines are written in a book by B.H. Mahan regarding the change in freezing point of water on changing the pressure. The vapor pressure of water at triple point of water is 4.579 mm. What ...
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0answers
39 views

Looking for a pressure phase diagram of selenium at large ranges of pressure and temperature

I'm doing undergraduate research and our group is having a lot of difficulty finding a comprehensive pressure phase diagram or phase table for selenium (including most known packing geometries that ...
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1answer
279 views

How does the state of iodine affect its HOMO–LUMO gap?

My teacher told me that the HOMO–LUMO gap in solid iodine is smaller than that in gaseous iodine. When I asked about the reason, he told me that it is due to higher interactions in solid iodine as ...
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2answers
6k views

Clarification of Kinetic Energy during Phase Change

This website states that: During a change of phase the temperature does not change, but the internal energy does. The internal energy is the sum of the kinetic energy of the molecules and the ...
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1answer
117 views

Does aqueous component contribute to the equilibrium constant?

Consider an equilibrium reaction with an aqueous solution $\ce{A(aq)}$ in equilibrium phase with gas: $$\ce{A(aq) + B(g) <=>[$K_\mathrm{eq}$] C(g)}$$ Would the equilibrium constant have aqueous ...
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0answers
63 views

Can anyone explain this condensation pattern?

What is the hair-like polymer that condenses on the caps of the plastic cell vial? Inside vial are cells in a mixture of FBS and DMSO. The vials were frozen slowly in a special isopropanol-filled ...
3
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1answer
152 views

Clausius–Clapeyron relation for states of water and vapor

I've seen many questions about this topic on this site, but I still have some issues trying to understand this aspect. Here's what I believe I understood looking at the phase diagram for a pure ...
4
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1answer
537 views

Why do gases need to be cooled to liquefy/solidify?

My book states: Gases do not liquify on compression only, although molecules come close to each other and Weak forces operate at a maximum. Why is it that we cannot just keep on compressing gas ...
5
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1answer
62 views

Harnessing phase separation to easily make Li film

I want to make a thin, smooth film of pure lithium in a glovebox. In general, I think that I can use a phase separation approach. I will heat a bath of mineral oil above Li's melting point, then ...
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0answers
35 views

Equilibrium involving water and solid component

$$\ce{A + B <=> C(s) + H2O(l)}$$ Why when $\ce{H2O}$ is liquid and $\ce{C}$ is solid, the equilibrium constant of the reaction is $$K_\mathrm{eq} = \frac{1}{[\ce{A}][\ce{B}]} \quad ?$$
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1answer
113 views

Dilution of whisky – the molecular perspective

Not a chemist. I'm trying to understand this abstract. In particular: We found that guaiacol is preferentially associated with ethanol, and, therefore, primarily found at the liquid-air interface ...
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1answer
490 views

Freezing point of oxygen-18 water

The freezing points of heavy water (3.8 °C) and tritiated water (4.49 °C) both seem to be well-known. I can't find anywhere that gives the freezing points of $\ce{H2^18O}$, $\ce{D2^18O}$, or $\ce{T2^...
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0answers
152 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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0answers
501 views

State symbol for electron

Is it correct to write a state symbol of "g" or "l" for an electron? In the textbook I am currently reading, the state symbol "g" was used for the electron when it described the electron gain by a ...
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6answers
5k views

Is there a cheap, safe liquid that evaporates EXOthermically around room temperature?

The heating and AC system in the building where I occasionally work, works like this (basically a thermostat): The administrators set some temperature that is maintained automatically. Say, in the ...
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1answer
243 views

How to calculate the latent heat when there is a boiling temperature range?

I have a DME (dimethyl ether)- methanol - water mixture with the mol fraction composition: DME 0.4295, methanol 0.1353, water 0.4351. This mixture has a boiling temperature range: dew point 141.6 °C ...
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0answers
164 views

Reforging tungsten/tungsten carbide temperatures

I was wondering about the reforging of tungsten and the temperature needed. As I understand it, tungsten melts at $\pu{3442 ^\circ C}$ and tungsten carbide at $\pu{2870 ^\circ C}$. However, once a ...
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2answers
117 views

Assigning labels and answering questions using given DSC graph

I'm currently working through past exam papers in preparation for my upcoming Inorganic Chemistry exam and I got to this question. We really haven't looked at DSC graphs, so I'm not completely sure ...
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5answers
22k views

A glass of water with ice-cubes in it. Where's the water the coldest; at the top or bottom?

Suppose that I fill a glass with ice water. As the ice melts, it cools the water around it. Given that cold water is denser than hot water, I would presume that the cold water would sink to the ...
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1answer
38 views

Does simmering sparkling water change/decrease its mineral composition significantly?

I know that heating sparkling water will cause it to lose $\ce{CO2}$. Does this have any other effects on the water that remains, such as reducing its mineral content? I understand when non-...
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2answers
1k views

Can I pour a solution into another vessel with no air bubbles?

I have been trying to create a method to create a homogeneous agar solution. What are appropriate techniques to ensure homogeneous solidification of an agar-based aqueous solution? The new solution ...
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1answer
974 views

What are the boiling points of DMSO-water concentrations?

What are the boiling points of DMSO-water concentrations with respect to wt% DMSO? I have found extensive information on the freezing point change of wt% DMSO but nothing regarding boiling.
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1answer
3k views

Graph between PV & P, Boyle's Law and its interpretation

My text book says: At higher constant temperature, the volume increase and value of product PV should increase due to increase of volume at same pressure, but PV remains constant at this new ...
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0answers
401 views

How to measure chemical potential

I wonder if there is a way to measure the chemical potential of a substance in a two-component mixture and also to account for its dependence on the number of moles. Explaining it further, suppose ...
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1answer
131 views

What are appropriate techniques to ensure homogeneous solidification of an agar-based aqueous solution?

I am making a T1 weighted phantom for an MRI project. I'm trying to see if I can calculate how much a persons head heats up during an MRI scan. It consists of distilled boiling water, $\pu{7 g/L}$ ...
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54 views

Literature values for NaCl Eutectic - Calculating the eutectic

For the NaCl eutectic I've seen two values widely used: 23.3wt% NaCl - James G. Speight: Lange's Handbook of Chemistry 2017) 5.1 M NaCl (Marion + Kargel 2008 - Cold Aqueous Planetary Geochemistry ...
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153 views

How do phase transfer catalysts bring anions to organic phase?

Many anions are quite stable in the aqueous phase, but not so much in organic solvents where its necessary to perform some reaction (usually nucleophilic substitutions). I have heard that crown ethers ...
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1answer
2k views

Why is the melting point of a substance is the same as its freezing point? [closed]

Melting point = Freezing Point Why is the melting point of a substance is the same as its freezing point?