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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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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0answers
151 views

Leakage rate Calculation

I have to calculate leak rate for helium/air from an enclosure which is made of fabric. This is similar to helium balloons. There are small holes in the fabric. How should i proceed ?
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0answers
25 views

Solution of multiple materials

Introduction I'm trying to make some strawberry liqueur. The recipe I got says I should put alcohol, strawberries and sugar in a bowl and leave it soaking for 4-5 weeks. I read that making liqueur is ...
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38 views

Half-Life Question [duplicate]

Possible Duplicate: How do we know that some radioactive materials have a half life of millions or even billions of years? I understand how to calculate decay, but it seems to me that the ...
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49 views
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1answer
497 views

What's the common consensus on the meaning of “physical change”?

I'm doing a textbook problem that shows a "molecular level" view of some matter, little colored balls, before and after, and there are, among the four questions, two that say: 1) Did a physical change ...
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99 views

Calculating the required amount of acid/base to reach a pH [closed]

Bit stuck on working this out - or if it is even possible. I have a reservoir of solution (water/plant feed/dead flies) that is pH 6 and I want to get it to pH 6.25. Here is the information I have: ...
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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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5answers
6k 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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3answers
176 views

Is duplication of nucleus, electron and proton (sub-atomic particles) possible? [closed]

usually a single cell develops into a huge mass to form a substance or an organism. is this happening because of multiplication of sub-atomic particles? if yes, then is it possible to multiply the ...
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3answers
211 views

Atoms and electrons?

Consider a copper atom. If you place an electron near it, the protons in the nucleus would attract it like they attract the existing electron in the valence shell. However the electron you placed ...
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1answer
1k views

Burning VS Melting: What is the relation in the atomic/molecular structure?

This has never been asked before on this site, so I thought I would ask this to help future searchers, passerbys, or others understand this better. What are the key differences between burning ...
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1answer
38 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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2answers
60 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 ...
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1answer
52 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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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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1answer
45 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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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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2answers
19 views

Exothermic heat release mechanism in gases

How is heat released when bond formation occurs in gases? For example, when atomic oxygen and molecular oxygen combine to form ozone?
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138 views

why do we Carbonate drinks not any other gas

Carbonation is done in all fizzy drinks. Also it forms a small amount of carbonic acid which we feel on our tongue. We can diffuse oxygen as well in the water at higher level. Except for acid ...
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2answers
62 views

A question on lewis model [closed]

Electron affinity of chlorine = -349 kJ per mole. And, first ionization energy of sodium = 496 kJ per mole while energy required for combining= 147 kJ per mole. Isn't it a contradiction against ...
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2answers
119 views

What is “species” in the context of an electrochemical cell?

From the Wikipedia entry on Electrochemical cell (http://en.wikipedia.org/wiki/Electrochemical_cell): An electrochemical cell consists of two half-cells. Each half-cell consists of an electrode, ...
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1answer
273 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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2answers
367 views

Why are the alkali and alkaline earth metals present in the ashes of burnt wood? [closed]

The alkali earth metals form the two left-most column of the periodic table of the elements, other than hydrogen. See wikipedia articles: http://en.wikipedia.org/wiki/Alkali_metal ...
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1answer
34 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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2answers
45 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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1answer
52 views

Is Boltzmann constant $k_B$ constant?

I heard in a lecture that Boltzmann constant $k_B$ is not constant in some special cases. Do you know the title of the article which contains this one? Do you think this idea is true?
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50 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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1answer
47 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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2answers
67 views

Could we describe acids and bases using electromagnetism?

Why don't we use Maxwell's equations in acids and base theory? Surely the interaction between two charged species is readily described by this. The theory I have so far come across is HASB theory. ...
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1answer
147 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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1answer
41 views

bimolecular reaction master equation

I was wondering how to write down the deterministic rate equation for a bimolecular reaction with similar particles. e.g. $A \rightarrow^{k_+} B +B$ and $B +B \rightarrow^{k_-} A$ now the rate ...
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1answer
66 views

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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1answer
88 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 ...
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1answer
49 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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79 views

What is this form of notation called?

$$^{14}_6C \rightarrow ^{14}_7N + E^{-} + \bar{\nu}_e$$ Just curious!
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1answer
416 views

Are valence electrons in nonpolar molecules localized/delocalized?

Are valence electrons in non-polar molecules localized or delocalized? I'm quite confused about the whole electron localization and delocalization business. I'd love a simplified explanation that a ...
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1answer
82 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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1answer
128 views

How fair is it to say that all chemistry arises from failures of the ideal gas law?

I was reading here about how the ideal gas law assumes point masses and non-interaction. Is it fair to say that all chemistry arises from failures of that? Of course, such a sweeping generalization ...
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1answer
486 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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1answer
394 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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1answer
58 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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1answer
50 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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1answer
267 views

Circulate smoke in a closed system

Hey i am by no means a scientist but i have a idea for a art work using smoke. Basically what i want to know is whether it is possible to circulate smoke by means of a pump through a transparent box. ...
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0answers
24 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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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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2answers
63 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
29 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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35 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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1answer
38 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 ...