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

learn more… | top users | synonyms (2)

4
votes
1answer
307 views

Can we model Chemical Reactions using Quantum Mechanics? If so, what is the most complex reaction we can model?

Not a physicist or Chemist, just interested in QM and it's applications. I've been reading lately about Quantum Chemistry and it occurred to me that since we can model electron orbitals in QM and ...
4
votes
2answers
655 views

Where does the Pauli Repulsive Force come from that counteracts the attraction between atoms and ions? [duplicate]

I'm learning about such things as ionic and covalent bonds, and the reason given for the ionic bonds is electrostatic attraction. However, if that were true, then the two ions would accelerate toward ...
4
votes
1answer
403 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 ...
4
votes
1answer
247 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 ...
4
votes
1answer
620 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 ...
4
votes
1answer
244 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 ...
4
votes
2answers
229 views

Why are the lighter halogens gases?

In the periodic table of the elements, only a few of the elements are gases at standard temperature and pressure. Those elements include the noble gases some of the halogens, and a few of the elements ...
3
votes
3answers
3k views

Why is the energy density of gasoline so high?

We sometimes play a game in my family whereby we trace the energy for a device back to it's source: The Xbox got power from the wall. The wall got power from the local transformer. The transformer ...
3
votes
3answers
492 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 ...
3
votes
5answers
5k 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 ...
3
votes
2answers
178 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: ...
3
votes
3answers
438 views

How would steel degrade in space

If there is a steel plate floating in space, for ever, within the solar system, how is it going to degrade? Of course without oxygen it is not going to oxidize (rust), but how are cosmic rays, UV ...
3
votes
1answer
291 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 ...
3
votes
1answer
1k views

Chemical potential interpretation

Something that has bothered me for a while regards the interpretation of chemical potential for different statistics. While I understand its meaning in metals (and its relation with the Fermi ...
3
votes
2answers
156 views

How to determine what an object is composed of?

Heads up: This question has never been asked (here) before the way I will ask it here, so let's shed some light on it a bit. Prelude and anecdote(can be skipped): The other day I was walking home, ...
3
votes
2answers
1k 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. ...
3
votes
2answers
99 views

Kinetic proof of law of mass action

Suppose we have a chemical reaction of the form $$n_1 A_1 + \cdots + n_r A_r \leftrightarrow m_1 B_1 + \cdots + m_s B_s$$ where $A_i$ and $B_i$ are molecules, and the $n_i$ and $m_i$ are the integer ...
3
votes
2answers
2k views

Widom-Larsen Theory

Does the Widom-Larsen theory pose a credible underpinning for Low Energy Nuclear Reactions, often incorrectly referred to as "Cold Fusion"? http://arxiv.org/abs/cond-mat/0505026
3
votes
2answers
314 views

When do thermal and chemical equilibrium not coincide?

What is an example for a system, which is in chemical equilibrium, but not in thermodynamical equilibrium? And what about the other way around? It seems to me, that as long as Parameters like ...
3
votes
1answer
707 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 ...
3
votes
1answer
469 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
votes
1answer
241 views

determination of voltaic cell voltage

if i understood this correctly, the determination of voltage for a specific voltaic (gallvanic) cell is determined only by the chemical correlation between the two metals. is this true? for an ...
3
votes
1answer
61 views

What is the origin and nature of the “hydrogen envelope” located on the sun side of a comet coma?

It is tempting to assume the origin of the hydrogen is water vapor from the comet, in which case, what process "breaks up" the water molecule (or perhaps ammonia molecule?)? Is the hydrogen actually ...
3
votes
1answer
583 views

Diffusion of gas in a liquid with changing pressure and solubility (chemical potential)

Modelling the diffusion of a gas dissolved in water in a vertical column of water, several meters deep. Also assuming the water is completely still, so only diffusion plays a role. (Actually a model ...
3
votes
1answer
107 views

Why does Relativity effect the melting point of mercury?

I know there is a related question, that references the Dirac Equation, that relies on relativity, but I've just watched this video: http://www.youtube.com/watch?v=NtnsHtYYKf0 Which seems to say ...
3
votes
1answer
305 views

What is a chemical potential good for?

I read that the definition of the chemical potential is, that it is the partial derivative of the Free energy with respect to the number of particles, $$\mu=\frac{\partial F}{\partial N}.$$ ...
3
votes
1answer
169 views

What's the underlying particle physics of endothermic reactions?

I don't just mean reactions that require heat to proceed, storing surplus energy in chemical bonds. I wonder about strongly endothermic reactions that suck heat out of environment. You take some ...
3
votes
1answer
248 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 ...
3
votes
2answers
322 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 ...
3
votes
1answer
982 views

How does a stronger magnet affect the MRI image quality?

In which ways is a stronger magnet better for magnetic resonance imaging? I read that: The field strength of the magnet will influence the quality of the MR image regarding chemical shift ...
3
votes
1answer
543 views

Energy levels in disordered organic semiconductors?

Now in disordered organics, the band picture is thrown out the window, from what I can tell (due to lack of symmetry). But don't HOMO/LUMO levels basically take the place of conduction/valence bands ...
3
votes
0answers
65 views

What is a covalent bond?

What is a covalent bond, quantum mechanically? How does it hold the two atoms together, and at one point can you qualify the electron as being shated between two atoms, versus feeling attractive ...
3
votes
1answer
42 views

Why is the objective function used in Nudged Elastic Band method reasonable?

In Nudged Elastic Band (NEB) method, which is used to find reaction pathways when both initial and final states are know, an objective function is first constructed and then minimized to find reaction ...
3
votes
1answer
79 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 ...
2
votes
2answers
72 views

Is there anyway to use a scientific instrument to measure the density of electron around the atomic orbital?

Is there anyway to use a scientific instrument to measure the density of electron around the atomic orbital? Please list both old way and more modern ways.
2
votes
2answers
110 views

Can a liquid shrink as something is dissolved into it?

Not much more to add. By shrink, I mean become more dense at the same pressure and temperature. And I don't mean vol(A+B) < vol(A) + vol(B). I'm sure this is possible. Is it possible to ...
2
votes
1answer
266 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?
2
votes
2answers
65 views

Is every material able to exist in every state of matter?

I was shocked while reading Kittel's "Introduction to Solid State Physics", that the solid state of noble gases is a well described and makes one of the fundamental achievements of solid state ...
2
votes
2answers
3k 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 ...
2
votes
2answers
3k 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 ...
2
votes
1answer
174 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?
2
votes
1answer
216 views

Are valence electrons located solely in the s and p subshells?

Or are they in all subshells??
2
votes
1answer
77 views

Does salt $NaCl$ as a solid float in molten salt?

I know ice floats in water because it's crystalline structure causes $H_20$ solid to be less dense than $H_20$ liquid. Is the same true for salt because it is crystalline? If not why?
2
votes
1answer
225 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 ...
2
votes
1answer
4k 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 ...
2
votes
4answers
103 views

role of entropy in gibbs free energy intuition

I have looked at various derivations of the Gibbs free energy equation and the underlying definition of the gibbs free energy. However I have been unable to attain direct insight/intuition over the ...
2
votes
1answer
82 views

Apparent color of flame as superposition of spectral lines?

In some cases one can identify a substance by the color emitted as it burns in a flame. A green flame might indicate the presence of copper. So here is the question. If we know wavelength and ...
2
votes
2answers
62 views

How do you know which atoms are in a specific piece of matter?

If you have a piece of matter in front of you, how can you know of which atoms it consists? And starting from nothing, how can I discover all the elements (or just a lot of them) of the periodic ...
2
votes
2answers
165 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 ...
2
votes
1answer
224 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 ...