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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Can I calculate the maximum concentration of sucrose that will dissolve in water at STP using physical constants?
I am interested in identifying the maximum solubility of sucrose in water. Can this value be estimated based on the physical properties of sucrose?
Eventually I will need this in degrees Brix (%w/w).
...
3
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1answer
147 views
Why do hydrogen atoms attract?
That is, why is the potential energy with the orbitals overlapping less than with the Hydrogen atoms 'independent'.
Similarly, why is a noble gas configuration stabler than if an electron were to be ...
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4answers
1k views
Could the Periodic Table have been done using group theory?
These three questions are phrased as alternative-history questions, but my real intent is to understand better how well different modeling approaches fit the phenomena they are used to describe; see 1 ...
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2answers
437 views
How do I integrate the Poisson equation to determine the electric potential along a particular direction (e.g., $z$)?
This question is a sequel of sorts to my earlier (resolved) question about a recent paper. In the paper, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, ...
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0answers
85 views
Handling halogen lamps
When consulting manuals, electricians, online sources, etc., they always instruct you to handle halogen light bulbs with gloves.
The "explanation" that usually accompanies this statement is that oils ...
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1answer
41 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
100 views
How to measure electrical resistance?
Is it possible to theoretically measure the resistance of passing of electrical current through liquid electrolyte (distilled water + NaOH) ?
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1answer
504 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
2k views
What makes the difference between ionic and covalent bonds?
Backstory: When I learned about chemical reactions, there were two types of molecular bonds: Ionic, where an atom or compound molecule with a low valence number loses those valence electron(s) to one ...
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2answers
221 views
In condensed matter simulations, how is particle number density computed in practice?
I have been reading a recent paper. In it, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, in which liquid resides between the parallel-plate electrodes. ...
3
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2answers
169 views
What physical forces give rise to the peculiar bond angle of hydrogen peroxide?
In one of the Periodic Table videos, Prof. Poliakoff shows a model of a hydrogen peroxide molecule and claims that the H-O bonds will always be at right angles to each other. I have a rudimentary ...
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1answer
1k views
What is the approximate electrical conductivity $\sigma$ of graphene in S/m or S/cm?
I am trying to find an approximate value of the electrical conductivity $\sigma$ of graphene in units of S/m or S/cm. This table on Wikipedia gives $\sigma$ values for a variety of materials ...
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3answers
835 views
Why is the canonical ($NVT$) ensemble often used for (classical) molecular dynamics (MD) simulations?
Molecular dynamics (MD) simulation is a common approach to the (classical) many-body problem. It relies on integration of Newton's equations of motion to simulate the trajectories of many (e.g., ...
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5answers
3k views
How was Avogadro's number first determined?
I read on Wikipedia how the numerical value of Avogadro's number can be found by doing an experiment, provided you have the numerical value of Faraday's constant, but it seems to me that Faraday's ...
5
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2answers
208 views
The AntiBonding Orbital with Shrinking Interatomic Distance
I guess this is more of a chemistry question, but whatever. I think it's interesting.
Suppose you had two bare atomic nuclei. For concreteness, lets assume the nuclei are the same with atomic ...
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1answer
120 views
Searching the point group of symmetry
I am engaged in the field of quantum-chemical calculations using programs written by myself. I have found out that I have a problem in finding the point group symmetry of the molecule.
The first idea ...
2
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1answer
147 views
Man on treadmill and energy/mass conservation
Suppose we put a very obese man inside a large air tight isolated room with a treadmill and he runs on the treadmill for 24 hours and at the end of the day he sees his weight has come down (mostly ...
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2answers
109 views
What would make the bottom of my cocktail glass develop a fractured pattern like this?
I left out the remnants of my Long Island Iced Tea. This was a mixture of various liquors, lemon juice, Splenda, and water from the melted ice. It was left on my kitchen counter for several days:
...
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1answer
399 views
Energy per particle vs. chemical potential vs. evaporation energy
There is a system of N particles. They interact and are bound together with a binding energy Eb (or potential energy). To characterize the system there are multiple terms
Energy per particle Eb(N)/N
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1answer
193 views
How much water is destroyed in photosynthesis, relative to the world's supply?
Water is involved in the photosynthesis. How much water are we talking about compared with the total amount on water on Earth? Is it enough to have an effect on the average age of water molecules?
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3answers
360 views
Is Uranium renewable, or will this science fiction scenario become reality?
In my imagination, nuclear power could disapear when we use up all the uranium generating electricity, or exploding nuclear bombs.
Is uranium a renewable resourse? if not, can we prove that this ...
2
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0answers
85 views
Dissipation when the temperature is not constant
Consider a process where some chemical species diffuses from one part of a system (which I'll call $A$) to another ($B$) at a rate $r$ $\text{mol}\cdot \mathrm s^{-1}$. If the system's temperature is ...
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1answer
116 views
what gives the vermiculite it's insultative properties
i know that vermiculite is used in insulation applications.
i found this notion of the R-value of vermiculite, that i don't know if its true.
basically i want to know if the attribute of the ...
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2answers
791 views
Is the Mendeleev table explained in quantum mechanics?
Does anybody know if there exists a mathematical explanation of Mendeleev table in quantum mechanics? In some textbooks (for example in "F.A.Berezin, M.A.Shubin. The Schrödinger Equation") the authors ...
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1answer
180 views
Electric dipole transitions/expectation value of position
Part of a homework question asks to show that for $\ell=0$ in both $\Psi_i$ and $\Psi_f$, we have
$$
\int \Psi_i^\ast \vec{r} \Psi_f \; d\tau = 0
$$
for the position vector $\vec{r}$. (This is for ...
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1answer
252 views
What is the purpose of a “protect from light” warning?
Some food or medical items, like rasberry juice concentrate I just bought, have a "protect from light" warning on the label. How can light influence products like milk and what does this warning mean ...
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1answer
947 views
How to know what materials are good conductors of electricity?
I'm not asking a question like "Is the wood conductive?". No. I'm asking what properties do they have to have to be good conductors. Theoretically I mean. Thanks.
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1answer
677 views
How much disolved oxygen is removed by boiling water?
Apologies if this is a chemistry question
I've read that drinking water contains dissolved oxygen to the tune of $10\:\rm{ppm}$.
I've also read that raising the temperature of water will remove some ...
3
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1answer
270 views
The 2011 Nobel Prize in Chemistry
As far as I understand a new pattern of crystal growth has been found experimentally. How does it relate to the known 2D and 3D nucleation and growth of crystals? The dominating theory of crystal ...
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1answer
100 views
Which bonds are the cross-links and which are secondary bonds (in elastomers)? [closed]
Elastomeres are "defined" as:
"linear-chain polymers with widely spaced cross-links attaching each molecule to its neighbours"
Now I found sentences (talking about glass transition):
"This means ...
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1answer
185 views
Vapor pressure higher than equilibrium vapor pressure
Is there any mechanism by which the vapor pressure of a liquid substance (lets say in a vacuum) is measured to be greater than the expected saturated vapor pressure at that temperature?
Specifically, ...
4
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1answer
184 views
Addition of a neutral electrolyte to water— how can it increase conductivity?
Sparked off by Is sea water more conductive than pure water because "electrical current is transported by the ions in solution"?
This question really belongs on chemistry.SE, which is ...
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1answer
2k views
Why is oxygen in a triplet state and what are the consequences?
From Wikipedia here and here:
''Almost all molecules encountered in daily life exist in a singlet state, but molecular oxygen is an exception.''
''The unusual electron configuration prevents ...
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2answers
682 views
What meaning do changes in the absolute value of Gibbs free energy have in a simple expansion process?
Below is a simple representation of the thermodynamics of a steam turbine. Stream kinetic and potential energy changes are neglected and no other type of non-PV work is done besides shaft work. ...
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1answer
458 views
How specifically do emulsifiers work?
I'd like to understand better how emulsifiers prevent droplet coalescence. There must be something more they do than just lower the surface tension between the droplet and the ambient substance. I ...
3
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1answer
345 views
What does activation energy actually do?
Spontaneous (exothermic) chemical reactions often require a push from the addition of externally supplied energy. This energy is often called activation energy. What does activation energy actually ...
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5answers
2k views
Conversion of mass to energy in chemical/nuclear reactions
Is mass converted into energy in exothermic chemical / nuclear reactions?
My (A Level) knowledge of chemistry suggests that this isn't the case. In a simple burning reaction, e.g. $C+O_2\to ...
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1answer
115 views
THT (Tetrahydrothiophene) absorption spectrum
I am looking for the absorption spectrum of THT. What is the best way to find these types of exotic material's spectral characteristics?
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3answers
342 views
Nanorobots. What stops us from producing them yet?
If we can already predicts accuratelly motion on molecular levels, what stops us from developing small robots to, for instance, navigate through our blood vessels looking for cancerous cells and ...
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1answer
95 views
Why don't the actinides start at neptunium?
In their physical and chemical properties, actinium, thorium, protactinium, and uranium are respectively similar to lanthanum, hafnium, tantalum, and tungsten, and thus would seem to belong ...
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2answers
424 views
Is mass-energy conversion in chemical reactions experimentally observable
This is a common point of argument on internet forums. I think it is fairly well established theoretically that there is a very small amount of mass converted to energy in an exothermic chemical ...
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0answers
39 views
Anyone Know Details About the New Nobel Prizes in Physics and Chemistry? [closed]
The physics prize seems to be in astronomy but, I guess, that falls into the realm of physics for the lack of a separate astronomy prize. The chemistry prize, however, seems to also belong to physics ...
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0answers
80 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:
...
4
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1answer
171 views
Voltage drop over a cell membrane
Again, a problem from exam preparation:
[A] cell's membrane allows sodium ions to pass through it, but not chlorine ions. The cell is placed in a salty solution with a ten times higher ...
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1answer
114 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. ...
2
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1answer
164 views
Is it possible to mechanically isomerize an sp3 hybridized carbon center?
Imagine I have an sp3 hybridized carbon attached to four separate polyethylene chains. By pulling on the polyethylene chains in some manner, is it possible for me to mechanically isomerize the chiral ...
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0answers
167 views
In Aerospace Salt Spray tests aluminum often gets covered in slime, what is this slime chemically? [closed]
When conducting MIL-STD-810, Method 509 salt Spray test many metals, but especially aluminum come out covered with slime. The slime usually dries to an easily removed powder. What is this slime? I ...
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1answer
343 views
Why is E85 less efficient than straight gasoline?
Why is straight gasoline (or whetever the mixture was before the introduction of ethanol) more efficient (ie, more miles/gallon) than E85? I've known since it's introduction that E85 was less ...
3
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1answer
200 views
Physical Chemistry: What's the relationship between orbital overlap and barrier shape?
This is a question for the physical chemists out there.
For a given chemical reaction there is a barrier to traverse in order to proceed from reactants to products. Reactants e.g. an organic base ...
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3answers
314 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 ...
