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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Why is SiO2 solid while CO2 is a gas? [migrated]

I was under the impression that chemistry almost exclusively involves valence electrons because there isn't enough energy to strip off electrons further in. If that is true, and atoms in the same line ...
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1answer
89 views

On Thermodynamics of Spontaneity of the Reduction-Oxidation Chemical Reactions

According to the first and second law for a closed system containing different chemicals we have \begin{align} &\delta Q - \delta W = dU = T dS - p dV +\sum_i \mu_i d N_i\\ ...
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30 views

Visible wavelengths of air fluorescence data - needed for school demo laser telephone design

I'm seeking information about fluorescence in visible wavelengths (390-700nm) of any of the main constituents of air ( $ N_2, O_2, CO_2, H_2O, CO, etc. $) that can be excited with a (hopefully ...
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1answer
23 views

Ammonia Unloading [closed]

The Ammonia Unloading via Ships happens at -33degC, why the temperature don't drop off or increase during unloading or during high heat summers environment? What's make him to maintain the ...
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1answer
165 views

Force field for Calcium ions, potassium ions and water in molecular dynamics

I want to adapt my existing MD simulation so that it can handle these three species. For the interactions of the ions I thought that I would use the coulomb potential, but I don't know what sort of ...
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3answers
393 views

Why does a pitcher with lemon juice have foam, while one with pure water does not?

Whenever I pour water into lemon juice (pouring directly from the tap into the pitcher, not quietly along its edge) I get a foam on top: The same pitcher with water (same water tap, pitcher, time ...
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1answer
19 views

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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26 views

How does fluid velocity affect the dissolution of some solute in the fluid?

Suppose we have a perfect sphere of some solute such as sugar and we place it in a fluid such as water, at a certain temperature, that is not moving. It will dissolve and diffuse into the water due to ...
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1answer
20 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 ...
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2answers
154 views

Extra vibrational mode in linear molecule

When calculating the number of vibrational modes for a molecule, the formulas differ for linear $(n = 3N - 5)$ and non-linear $(n = 3N - 6)$ molecules, where $n$ is number of modes and $N$ is number ...
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3answers
331 views

What force creates ions out of neutral atoms?

Consider the reaction between Na and Cl to form NaCl. Na loses an electron and "gives" it to Cl because this makes both atoms more stable. But what forces "pulls" the electron from Na to Cl? Both ...
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165 views

What happens to gas molecules after ionization?

I know that gas molecules conduct electricity after they get ionized but what will happen if we keep increasing the voltage even after ionization? Will it explode? If it will then how much energy ...
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0answers
19 views

Why our cells don't merge, when their phospholipid membranes touch each other? [migrated]

Membranes of our cells consist of lipid bilayer (with some other components mixed in). Why wouldn't those lipid bilayers glue to each other and our cells won't merge? If you suppose that it's due to ...
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0answers
24 views

Heat Retention of Wine

This may seem odd and lengthy but I am going to attempt to consolidate my thoughts as much as possible. I'm sorry in advance for the length of my post and if this is confusing. I am currently ...
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0answers
36 views

What factors are influencing a woosh rocket?

Not sure if this is too much chemistry, but I'll try: If I fill a plastic bottle with a small amount of rubbing alcohol, shake it around and hold a match to the bottle neck, I'll get a flame wooshing ...
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1answer
112 views

reactions in molecular dynamics simulations

EDIT: Apparently this is called reactive molecular dynamics. It seems that the ReaxFF potential function is used for some reactions like this. I am interested in adding support for reactions to a ...
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1answer
94 views

Physical distribution of salt anions and cations during electrophoresis

If I have a volume of $L$ liters of salt water at a concentration of $\approx N$ mM NaCl and I pour it into an electrophoretic apparatus (like this one: ). Once we turn the apparatus on, and set the ...
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1answer
279 views

Electrical Resistance and chemistry

Can some one describe or explain what happens when too much current is passed through lets say a copper wire, I am looking for an explanation to do with physics and chemistry. For instance we have ...
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1answer
36 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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25 views

Virial equation - Taylor expansion

I don't get how Taylor expansion over $ \frac{1}{\overline{V}} $ of Virial equation of state is carried: $Z = \frac{P\overline{V}}{RT} $ which yields $$ Z = 1 + \frac{B_{2V}(T)}{\overline{V}} + ...
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0answers
19 views

Maxwell relations | U goes down pressure?

Differentiating Helmholtz function $ A = U - TS $ with respect to $V$ we get: $$ (\frac{\partial A}{\partial V})_{\scriptscriptstyle T} = (\frac{\partial U}{\partial V})_{\scriptscriptstyle T} ...
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4answers
722 views

The “binding energy” of bonded particles adds mass?

This is a follow-up my previous question. Several of the answers indicated that the mass of a particle (atom, proton, etc.) increase with the "binding energy" of it's component particles - the energy ...
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2answers
65 views

Electrolysis boat engine

Would it be possible to create a submersible boat engine using the combined principles of electrolysis of water, ramjet propulsion, and hydrogen-oxygen combustion similar to that used in rocket ...
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0answers
35 views

Does a fixed amount of gas have slighty more mass when at a higher temperature?

According to relativity, energy and mass are equivalent. Does this mean that the energy added to a fixed amount of gas when it is heated adds slightly to the mass of the gas? The difference would be ...
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0answers
36 views

Filling an empty box with ambient air

A rigid box has a volume of $V_1$ and is thermally isolated so that it exchanges no heat with its environment. Initially the box is empty, and the air around it has a pressure of $P_0$ and a ...
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5answers
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When I stretch a rubber band, it breaks. When I hold the broken ends together, why doesn't it join again?

The question is simple. When we join the two broken surfaces, what is it that keeps the surfaces from connecting with each other, while earlier they were attached to each other? Also, would the two ...
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4answers
10k views

Is it possible to flow current in open circuit?

As I know a battery is an example of a closed circuit where it can then produce electricity , electrons will flow from negative pole to positive. A chemistry representation of this battery is for ...
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2answers
33 views

Molecules from atoms [closed]

Why does two oxygen atoms combine to form a molecule and not 3 or 4?Also why does one sodium and one chlorine atom combine to form NaCl while two chlorine atoms are required to combine with one ...
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2answers
56 views

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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2answers
8k views

How to estimate the physical size of a molecule?

I'm reading some chemistry-related papers that employ concepts of droplet evaporation. Since I am no chemist, I am wondering: How can I estimate the actual size of a molecule, say succinic acid? An ...
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2answers
2k views

Obtain oxidation numbers from looking at electron configuration?

Suppose I know that Selenium has electron configuration $[Ar] 4s^2 3d^{10} 4p^4$. How can I use this information to then come to the conclusion that its possible oxidation states are 6, 4, 2, 1 and ...
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1answer
46 views

Why water expands when freezes? [duplicate]

I'm sure this is for most of you a basic question, but it really puzzles me: How it is that, even though all materials expand as they get warmer, and contract (maybe these are not the correct terms) ...
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5answers
163 views

What compounds or elements only have one phase or two phases?

Wood appears to be one. I think gases like helium and hydrogen cannot exist in the solid state under normal pressures, correct? And why do those "phase cheaters"-- those elements/compounds which ...
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2answers
80 views

Atomic orbitals

I just studied atomic orbitals in a theoretical QM class, and I'm left with several questions, that are probably more questions in quantum chemistry: Many orbitals seem to have a preferred axis - ...
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1answer
47 views

Why does sunlight cause colors to fade?

If you leave something outside, its colors seem to inevitably fade or bleach due to exposure. Is this due to UV absorption? What sort of mechanism causes this - is it that man-made dyes deform on a ...
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2answers
64 views

Why do corpses come back to water surfaces after sinking at first?

I want to know that why do dead bodies or corpses come back to the water surface after being sunk at first by the use of stones or anything. For what I can understand, I think it's due to water ...
3
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2answers
82 views

Questions about the strange character of antimatter

Its been a few days and i have just been introduced to the concept of antimatter. Every Speck of matter in the world has its anti form basically that we have antimatter whenever we have matter. But I ...
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1answer
39 views

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 ...
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1answer
329 views

Donors/Acceptors in Metal Oxides

Can anyone explain to me why most articles describe chromium as an acceptor in titanium dioxide? In TiO2, titanium has the charge state Ti$^{4+}$ and oxygen has the charge state O$^{2-}$. When Cr ...
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0answers
27 views

What is the work-function of a monolayer metal on a substrate with charge redistribution at the interface?

The work-function on subsrate/metal with nm thick (or above) metal layer generally reveal the intrinsic work-funtion of bulk metal. But what if there is a monolayer thick metal, and there is charge ...
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44 views

Why is the water diamagnetic?

I checked using my permanent magnet that water is diamagnetic. But why is it like that? Does this have any important consequence for life?
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1answer
44 views

Whats the maximum number of electrons that can fit into the outer shell of boron?

Whats the maximum number of electrons that can fit into the outer shell of boron? Like silicon has 4 electrons in the outer shell but the maximum it can hold is 8 electrons so whats the maximum number ...
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1answer
92 views

Does O$^{2-}$ really exist?

In chemistry it is common sense that we have O$^{2-}$. But from a physical point of view, does O$^{2-}$ really exist as a negative ion? I mean, as an isolated ion. It is not apparent that a neutral ...
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2answers
904 views

How is the number of electrons in an atom found?

I was wondering, what type of experiments were held to identify the number of electrons in an atom? (For example, how do we say that carbon has 6 electrons and magnesium 12.) I would like someone to ...
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1answer
30 views

Reaction Energy

Is the energy involved in exothermic and endothermic chemical reactions positive, negative, neutral, or something else? As in, what does it affect/come from (neutrons, protons, electrons)? Does it ...
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1answer
55 views

Have scientists always known that the Sun was not a fuel+air system?

Astronomy is far older than nuclear physics. So there was a long time in which fire was a reasonable explanation for the sun burning. Has any scientist figured out the sun cannot possibly be a normal ...
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5answers
7k views

Why does burning magnesium explode when sprinkled with water?

Magnesium powder burns extremely well and reaches temperatures of 2500°C. However, attempts to extinguish such a magnesium fire with conventional water (e.g. from a garden hose) only make it worse: ...
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1answer
55 views

What happens if a free radical is placed in absolute vacuum?

I'd like to know what happens if a free radical has no material around to interact with. I have asked many people but I am not satisfied with their answer. I know there is nothing like absolute ...
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1answer
50 views

Chemical reaction A+B$\leftrightarrow$C. Equilibrium VS Non Equilibrium

Could you please confirm or say why I am wrong? Let us consider the steady state of the chemical reaction $A+B \leftrightarrow^{k_+}_{k_-} C$, with $k_+$ and $k_-$ the forward and backward rates. ...
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Given the Pair Correlation Functions for a Multi-component Fluid, is There a Simple Way to Obtain the Helmholtz Free Energy?

I think it may not be possible. Given all the pair correlation functions (e.g. calculated from Ornstein Zernike theory), it seems possible to obtain the internal energy (assuming different species ...