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Questions tagged [physical-chemistry]

Study of macroscopic and microscopic phenomena in chemical systems in terms of physical laws and concepts [thermodynamics, statistical mechanics, kinetic theory, quantum mechanics...].

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77 views

electron shell jumping in Iron?

I understand a "little" about electron shell jumping, I was wondering about "Iron", If iron was heated to a gas, perhaps held in a vacuum maybe even under pressure, would the added energy make the ...
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155 views

Does chemical energy contribute to mass? [duplicate]

Does chemical energy contribute to the mass of an object? I don't mean the bond energy, but the possible energy that could be released (i.e. Does an atom of oxygen and a molecule of hydrogen (H2) have ...
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Is water steam in air a case of liquid in gas solution?

Thinking of this question, I thought that the phenomenon of water evaporation into the air is totally analogous to the solid (say, salt) that is dissolved into a liquid (water). Indeed, in this ...
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118 views

Why don't fire hoops blow out while spinning, but blow out when blown out?

My friend spins fire hoops and we're wondering why they don't blow out while she's spinning them, but do, when she blows them out one by one. I don't imagine there's so much more CO2 (so much less O2)...
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374 views

Energy of a system if the nuclear repulsion increases

I have calculated the optimised geometry for a molecule. I have noticed that the energy of the nuclear repulsion increases with each iteration of optimisation. What is the logic behind this?
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Correlation energy - is it the difference between the Hartree-Fock energy and exact energy, or Hartree-Fock PE and exact PE?

For some reason I can't find anything stating it either way explicitly. What I'm talking about is this. Is this difference referring to potential energies or just energies in general? I assume it's ...
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Question regarding NaCl equilibrium separation

So I am tutoring someone later and one of the problems is from Eisberg/Resnick Ch 12. The potential energy $V$ of NaCl can be described emperically by $$V = \frac{-e^2}{4\pi\epsilon_0 R}+Ae^{-R/\...
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212 views

How to thermodynamically understand process of burning a piece of coal?

Let's imagine that I have a match in hand and nugget of coal on my desk. Then I light up the match and place it for few seconds near the coal so a tiny piece of nugget catches fire. Then another piece ...
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173 views

How does gas pressure increase the lifespan of Halogen tungsten lamps in the Halogen Cycle?

I am curious about this passage "Since quartz is very strong, the gas pressure can be higher,[5] which reduces the rate of evaporation of the filament, permitting it to run a higher temperature (and ...
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706 views

DFT Calculations, Atomic Ionization Potentials — Which Exchange-Correlation Functional to Use, to Preserve Koopmans' Theorem?

I have a program which can perform density-functional calculations for atoms, given a density functional. Of course the simplest form of exchange potential to use is one relevant for a uniform ...
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does there exists a rope such that it takes longer to burn the whole rope from one end? [closed]

And it takes less time to burn from the other end. The rope could be any of materials and structures and asymmetric. EDIT: But the external environment may not change during burning, and the way (eg ...
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594 views

Chemical potential in terms of temperature and pressure

For part (a), I know how to take the partial derivatives of S to get chemical potential, pressure. But there seems that I still need one equation to correctly express chemical potential in terms of T ...
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63 views

Is there any scientific instrument right now to monitor complicated chemical reaction between atom? [closed]

What is some differnt way to use any scientific instrument right now to monitor complicated chemical reaction between atom??
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171 views

Thermodynamics of zinc chloride to zinc

I am trying to deposit zinc metal from zinc chloride using chemical vapor deposition. But it is thermodynamically feasible to obtain zinc from zinc chloride?
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1answer
117 views

Calculate the required water for humidity [closed]

I'm not sure if this is the right place to ask. I have a humidifier, and a closed room. Basically, I want to know the required water to reach a certain level of humidity. My room volume is 42 meter ...
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2k views

Calculating molal depression constant from latent heat of fusion

Calculate molal depression constant of water if latent heat of fusion of ice at $0^\circ \text C$ is $80 \text{ cal/g}$. All I could find was the equation $K_f=\frac{0.002T^2}{L_f(\text{in cal/g})}$ ...
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785 views

Chemical Equilibrium - Why do changes in pressure cause a shift in the ratio of products and reactants?

I understand Le Chatelier's principle and how every change to an equilibrium system causes an opposing reaction from the system. I also understand how, when pressure is increased, the equilibrium ...
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782 views

What's the vapor pressure and evaporation enthalpy of a saline solution?

Suppose you dissolve an amount of salt in water. Because of the attraction between the ions and the water molecules, you'd expect lower vapor pressure and higher enthalpie, both depending on the ...
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88 views

Action on Lard Oil

If water is mixed with lard oil and heated (creating some super-critical liquid with water), how does this affect the volatility of the mixture in comparison with its purity..? So, My question is: ...
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63 views

Is it possible to make use of paper/bill permeate by chemical compound to became a paper-made bullet-proof vest?

Is it possible to make use of paper/bill permeate by chemical compound to became a paper-made bullet-proof vest? This is inspired by Greece and Italy tend to have more riot than rest of the Europe ...
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17 views

reverse osmosis membrane

We are second year cram schoolers , we are currently working on a project tackling water desalination by reverse osmosis and are required to do an experience. During the process, we encountered some ...
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What is the behaviour of excited state spins in an intermolecular context?

This question is about luminescence. UV excited molecules can relax emitting light or by vibrations. The relaxation process can occur fast if there is spin conservation between the excited and ground ...
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19 views

What causes ${\rm Si}$ to expand when lithiated?

Looking at research into Si-based lithium-ion batteries, the main issue seems to be that the Si increases size by a factor of 4 when lithiated. I'm interested in understanding what actual forces are ...
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89 views

Why doesn't NASA try using high-explosives to fuel rockets?

For a smoothly burning liquid-vapor mixture, I understand that burning hydrogen and oxygen is the best possible solution, not just for now but even theoretically. (?) But I read about ideas, that ...
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52 views

On an atomic level is energy only transferred through phonons and photons?

On an atomic level is energy only transferred through phonons and photons - there's no other means atoms can absorb or give off energy & all chemical phenomena & physical transitions arise ...
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What are first and second order phase changes?

In my thermodynamics lecture course, the Ehrenfest equation for a second order phase transition was derived from considering the following graphs, however there was little context in the section for ...
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63 views

What was the pressure generated in Fat Man to compress the fissile material?

Fat Man was an implosion-type nuclear weapon. What was the pressure generated by the chemical explosive?
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Why is $\Delta_r G^0$ temperature dependent in the van 't Hoff equation?

One can derive for a equilibrium reaction between ideal gases $$\sum_i \nu_i R_i \leftrightarrow \sum_i \nu_i P_i $$ the expression $$ \Delta_r G^0=-RTln(K) \quad \textrm{where} \quad K=\frac{\Pi_{\...
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27 views

Do different ways of vaporizing water have different efficiencies?

Question Are some ways of vaporizing 1kg of pure water at ATP more efficient? Specifically cold vs hot methods of vaporizing water. Background There are many ways of vaporizing water. Some ways ...
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34 views

High boiling-point oil

What is the highest boiling point oil in the world? I mean oil with a boiling temperature above 300 ° C. How can I find its physical property?
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Atoms with energy differences corresponding to wavelengths 19.05 cm, 24.45 cm and 25.48 cm

I was just wondering whether there are any known atomic transitions in Oxygen, Nitrogen, Hydrogen or Helium atoms/ions which emits wavelengths in any of the regions: 19.05 cm, 24.45 cm and 25.48 cm. ...
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How can a chemical substance explode, producing only solid products?

Silver acetilyde, like some other salts of silver, is unstable and explodes with great force. However, unlike almost all other explosive compounds, it doesn't produce any gases - it only produces ...
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5answers
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Does oxygen and carbon dioxide separate in a closed box?

If I have "air" in a closed box, does oxygen and carbon dioxide get separated over time? Does oxygen fill upper part of box and carbon dioxide lower part of box? How about if upper part of box is ...
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8 views

Salt Concentration relationship with specific heat capacity. Theories for linear relationship

I was curious about the relationship between salt concentration of a solution and its specific heat capacity. I've seen research (and made my own graph too) where the data shows there's a negative ...
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18 views

Is it possible to convert carbon soot/ black carbon in mg to CO2-equivalent? If so, how?

Since global warming is expressed in terms of carbon emissions or CO2 equivalent, can the short lived carbon soot/ black carbon that is produced from incomplete combustion be expressed in terms of CO2 ...
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32 views

The dependence of entropy on temperature?

I am wondering why the entropy will increase faster for a gas (when compared to a liquid/solid) when temperature increases? Is it because the heat capacity for a gas is lower than solids and liquids? ...
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1answer
40 views

Activity and radioactive decay

So, I am pretty new to that concept, which i am learning about in the context of physical chemistry. I am a mathematician, so a physicists approach can be confusing at times. I have two questions : ...
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Gas Transport Problem

I have a question that I thought would be a very simple effusion calculation that sent me down a massive rabbit hole after I tried to look it up in Landau's Physical Kinetics and so now I'm coming to ...
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15 views

Does a static-firing rocket engine do work?

Is the "working fluid" doing any work during a static-fire of a rocket engine. Since the rocket is held stationary, there is no work being done on the rocket right? However, is the exhaust doing work ...
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$H_2O$ dissociation by ionization in a discharge tube

As a casual amateur scientist, I wonder if it is efficient to electrolyse water in a discharge tube. I imagine that there would be 4 electrodes arranged perpendicularly. the first set of electrodes ...
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Calculating Simple Ground State Energy Of Hydrogen From Geminal Spin Function

I'm very new to quantum stuff and I'm experimenting, but I'd like a good explanation here if you can give it. Here's the circuit diagram and the results. I'm seeing from this paper that you can get ...
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16 views

Conservative or non conservative convection

I want to describe the convection of a species $B$ by another species $A$. Meaning that $A$ is bringing $B$ with it, and there is no other velocity associated to $B$. So I have 2 conservation ...
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What is the difference between laminar burning velocity and laminar flame speed?

I am trying to understand the difference between laminar flame speed and laminar burning velocity for a flat flame without heatloss and stretch effects. Please help me with this question.
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35 views

What is the static exchange approximation?

In this paper, on the 4th page (and throughout), they talk about studying electron-helium scattering in the "static-exchange approximation". I have scoured the literature and have not been able to ...
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1answer
51 views

My soap produces less lather as it gets old

I don't know it you have encountered this too but I have observed this "phenomenon" from the last few hundred soaps I have used. As the soaps get older they produce less lather than they produced ...
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21 views

Chemical reactions in fluids

The equations of motion of ordinary relativistic hydrodynamics are derived by considering conservation equations of the energy tensor and particle number current, where constitutive relations relate ...
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23 views

Relation between oscillator strengths $\log{gf}$ and the Einstein $A$-coefficient, rotational quantum number, …

I'm analyzing the spectra of M dwarfs. Some authors characterize the lines with the oscillator strengths $\log{gf}$ while others follow different paths with the Einstein $A$-coefficient. I would like ...
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Entropic Restrictions to Water Interfaced with Hydrophobic Molecules

The occlusion of hydrophobic molecules from polar solvent such as water, I have read, is an entropic effect. My question is pretty simple -- at an interface of water and oil, or in the clathrate cage ...
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49 views

Increasing the melting point of metal

I need to know how one can increase the melting point of a metals like steel, tungsten or ... about 500 degrees and without destroying its shape?
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68 views

Why don’t ALL polymers collapse even when their compact state would clearly be favoured in terms of having a lower Helmholtz free energy?

This question is based on example 8.3 in Molecular Driving Forces, Dill and Bromberg (https://books.google.ch/books?id=1gYPBAAAQBAJ&pg=PA136&lpg=PA136&dq=polymer+collapse+a+toy+model&...