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...].

208 questions with no upvoted or accepted answers
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9
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2answers
897 views

What would be the first compound formed in the early universe?

This may sound like a chemistry problem, but I suspect this would have lot to do with primordial nucleosynthesis. After all physics underlies everything. It is believed that several elements were ...
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1answer
537 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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2answers
68 views

Does salt water melt faster or slower than pure water?

I am trying to conduct an experiment on the melt time time of two ice cubes with a different salt concentration, one with none and one with a lot. Does salt water melt faster than pure tap water? (...
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1answer
201 views

How much air could an activated charcoal bag or baking soda box actually purify / deodorize?

Someone I know recently bought a set of small stylish and expensive cloth bags (roughly paperback book sized) filled with activated bamboo charcoal, that you place in a room and it purportedly ...
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0answers
51 views

Concept of polarization in microwave rotational spectroscopy

I am trying to understand the concept of polarization of molecules after they are excited by a microwave pulse. The context is: The complexes are produced in a pulsed supersonic jet expansion of a ...
3
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0answers
113 views

How did we first discover oxygen exists as $\rm O_2$ and not just $\rm O$?

How did we first discover oxygen exists as $\rm O_2$ and not just $\rm O$ ? (similarly hydrogen as $\rm H_2$ and not $\rm H$) I vaguely remember knowing a story about how the chemical formula of ...
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40 views

Stability of saturated energy levels

In The Feynman Lectures on Physics, Vol. 3, Section 15-5, there's a discussion of the stability of various benzene ions. It turns out that the ions for which the all the energy levels up to a certain ...
3
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144 views

Why are chemical reactions the same at different gravity levels?

Are all chemical reactions the same at a quantum level in different levels of gravity? How does the mass of subatomic particles change atomic behaviour at different gravity, in terms of speed and ...
3
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1answer
244 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\\ &\Rightarrow\;\...
3
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1answer
123 views

In chemical compounds, where does the “magic” come from in atomic “magic numbers”?

It is well known that atoms with a full electron shell are more stable, it is one of the first facts taught in a middle school Chemistry course: "An element whose atoms have no electrons outside ...
3
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1answer
729 views

What's the densest known material that has been made in macroscopic quantities?

I'm aware that the densest stable element is osmium at 22.61 g/cm3. And that there are unstable elements such as hassium and meitnerium which are predicted to have densities of 41 g/cm³ and ...
2
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0answers
30 views

What exactly does it mean for an element to experimentally violate the Madelung ordering rule?

The Madelung ordering rule says that as you increase the atomic number of a neutral atom, the electron orbitals fill up in order of increasing value of $n+l$, and in increasing order of $n$ within a ...
2
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1answer
58 views

Why doesn't lithium form di-lithium crystals? (Calling Mr.Spock)

Hydrogen is in the first column of the periodic table. At STP it is a di-atomic gas. When cooled and/or under pressure it forms a crystalline solid of di-hydrogen molecules. Calculations indicate ...
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0answers
51 views

Chemical potential of a reaction

I often see two various forms of the species $i$ chemical potential $\mu_i$ in a chemical reaction, in terms of enthalpy of formation $\Delta h_{f,i}^0$ and standard state entropy $s_i^0$. My ...
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0answers
69 views

How to determine symmetry of the system from the term symbol?

I'm studying term symbols. I can derive them mechanically from the electron configuration using the complete table of microstates. Let's consider a typical example - an atomic carbon with the ...
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43 views

Under what conditions can molecules exist?

I am curious to know the conditions required for any two or more atoms to bond together and form a stable molecule. Is their a set of rules that should be satisfied?
2
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1answer
67 views

Do discrete symmetries in molecules leave statistical “artifacts” like the Equipartition Theorem?

In statistical mechanics we have the equipartition theorem which can derive heat capacity simply from degrees of freedom. For example, diatomic gases have an increase heat capacity of $ \frac{7}{2} N ...
2
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1answer
67 views

Which superheavy elements have color?

I read that gold is colorful because relativistic effects change electronic energy gaps ($5d$ to $6s$) so that some of them absorb photons in the visible range. This effect is apparently due to ...
2
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0answers
262 views

Are $\Delta G = RT \ln{\frac{Q}{K}}$ and $\Delta S = -\frac{RT\ln{\frac{Q}{K}}-q_p}{T}$ legitimate relations?

While messing around with $\Delta G = \Delta G^\ominus + RT\ln{Q}$ and $\Delta G^\ominus = -RT\ln{K}$, I found this relation: $$\Delta G = RT \ln{\frac{Q}{K}}$$ which helped me clarify how $\Delta G$...
2
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0answers
147 views

Entropy production in non-equilibrium systems: physical interpretation?

I have been learning about entropy production in non-equilibrium systems as developed by Prigogine and others, especially in the context of chemical reactions. I now understand that from the first law ...
2
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0answers
66 views

Thermodynamic Estimation of Flame Temperature

I am trying to create a simulation program for the internals of a solid rocket motor, and I would like to know how you can theoretically predict the burning temperature of a propellant based on the ...
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0answers
79 views

In osmosis, how does chemical potential ever balance out?

Chemical poential is modeled by the equation $\mu_i = \mu_{i,0} + RT\ln x_i$. If you have one side with some $x_i$ of NaCl and another side with pure water separated by a semipermeable membrane ...
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0answers
83 views

Are the $+\leftrightarrow+$ and $-\leftrightarrow-$ methanol rotational transitions dipole-allowed?

I am quite confused about the origin and justification of the rotational selection rules of methanol, and I would appreciate any help or references. As far as I understand, there are three irreducible ...
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0answers
1k views

Why human body is not affected on magnetic field?

Electric-current easily cause shock to human body. But magnetic fluxs through human body do-not cause any perceptible change, as-well no invisible-impacts/ health impacts are well-known. We, when hold-...
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562 views

How to calculate the minimum kinetic energy required by a surface molecule to escape the liquid (during evaporation)?

Evaporation occurs when surface molecules have enough Kinetic Energy to escape the surface of the liquid. Given a certain volume of liquid at a certain temperature, is it possible to determine this ...
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0answers
120 views

Why dynamic equilibrium exists?

We know that at equilibrium Gibbs energy is minimum. We also know that at equilibrium both forward and reverse reactions occur simultaneously, and also we know that for a reaction to be spontaneous ...
2
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1answer
90 views

Do antiparticles exhibit different chemical properties?

In my physics class today. My teacher mentioned anti-helium and since I had never heard of anti-atoms (if you get what I mean by that) just antiparticles, this made me think: If we could produce anti-...
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82 views

The underlying chemical interactions behind torque

I did some searching around, and didn't find any previous topics that address torque in this specific way -- here goes: Say I just have a plain ol' piece of wood -- relatively long in one axis, so it ...
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261 views

Why is the activation energy of combustion so large compared with regular bonding?

I wanted to know why combustion requires an activation energy and I found this article (see this too). It says that molecular oxygen ground state is a triplet state (according to Hund's rules), and ...
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159 views

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 ...
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248 views

Confusing Chemical potential of mixtures

I feel that there are very few textbook that treat the chemical potential of mixtures in an understandable clear way, which is why I wanted to ask here about certain things? Although I do not have a ...
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61 views

Approach to model solvent in a lattice: e.g. H2O in NaCl

If a lattice contains a solvent, lets say NaCl and water of crystallisation, what is the condition for a solvent molecule to change it's location? From my current point of view I assume that such a ...
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0answers
69 views

Electrochemical cell potential - Prigogine book

I'm trying to understand equation 10.2.14 from Prigogine book "Moder thermodynamics": $V=\frac{\tilde{A}}{nF}=\frac{1}{nF}\left(\mu_X^R+\mu_Y^L-\mu_{Xred}^R-\mu_{Yox}^L\right) - \left( \phi^R-\phi^L \...
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0answers
209 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 ...
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237 views

High Young's Modulus and Tensile Strength of Carbon Nanotubes

I was recently reading about Carbon Nanotubes having extremely high Young's moduli, as well as high Tensile Strength, making them very interesting fibers. However, when I read this I wondered what was ...
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82 views

generation / destruction of fermions by phonons

my Hamiltonian consists of 1D free fermions coupled to a bosonic bath. The interaction is dictated both by scattering terms $H^{scatt}=\sum_{kq}\alpha^S_{kq}c^\dagger_kc_{k+q}X_q+h.c.$ as well as ...
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0answers
128 views

Are metal modes mixed with molecular modes during surface enhanced Raman effect?

This question is dedicated to Martin Fleischmann (1927-2012). When a molecule is adsorbed on a metal surface, the Raman scattering amplitude from the molecule is enhanced. According to Wikipedia, the ...
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0answers
198 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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3answers
46 views

Why doesn't a chemical reaction occur with the movement of electrons in the context of electricity?

In school it is generally taught that the movement of electrons between two atoms causes a chemical reaction. However, when it comes to electricity why doesn't a chemical reaction occur with the ...
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28 views

How does ski wax (nonpolar liquid) dissolve into polyethylene (nonpolar plastic)?

Ive been reading alot about ski waxing and a reputable source said that when you iron in paraffin wax into the base of a ski or snowboard, the wax melts from the heat of the iron and dissolves into ...
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0answers
24 views

Beryllium Neutron Multiplier

We know that Beryllium is used in blankets of Fusion Systems because it is a neutron multiplier. I was wondering that if Beryllium is a neutron multiplier can it be used in the fission process(of ...
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0answers
25 views

Crystals, symmetries in mixture

What would happen to the crystal structure of ice, if i freeze salt water? What changes in symmetry can i expect? I do not know the terminology for this stuff...but in what 'subclass' or 'subfamily', ...
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1answer
33 views

Can a quadrupole form in a purely organic crystalline material?

I'm a chemist so bear with me here. This is a question about small molecules, such as biphenyls. In the solid-state biaromatic systems without steric hinderance forms planar conjugated structures. By ...
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0answers
34 views

Fires with chlorine

could a fire with it's fuel consisting of mostly carbon like coal or wood use chlorine instead of oxygen. My thinking goes that when fire burns it sucks in oxygen and that bonds with carbon to make ...
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1answer
37 views

How does boiling-point elevation due to a solute affect the steam/gas that is created when boiling?

Consider the following situation: We have a pot of strong brine (for concreteness let's say 25g of NaCl per 100ml of water, at standard conditions) and heat it to a boil. How will the salt content ...
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0answers
46 views

Lagrangian for a concentration field

If I have a field, $\phi(x)$, representing the concentration of particles in a one dimensional space, what is the Lagrangian for this field? My initial guess was $$\mathcal{L} = \int dx[\frac{1}{2}\...
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0answers
87 views

Why does lithium have a total electronic spin of 1/2?

The book I'm reading analyses atoms by only looking at the last eletrons, and saying that their wave function must be anti-symmetric. I understand the case of Helium, the spin function must be anti ...
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1answer
123 views

Knudsen Number and pressure

When computing the Knudsen number to know if the continuum hypothesis can be applied as $\frac{k_B T}{p \sqrt{2} \pi d^2 L}$, do we use the static or total pressure of the free stream? My object is ...
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0answers
38 views

Is the designation “chemical reaction” right for vibrational and electronic excitation of particles?

I'm currently doing my Master's thesis, which focuses on Atmosphere Reentry Thermodynamics and Kinetics. Due to the importance of this work, I would like to use the best terms to describe any ...
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0answers
12 views

Does anyone knows where can I find the phase diagram of oxygen free copper (OFC or OFHC)?

I am having problems with a niobium deposition I made on a substrate. I increased the temperature to 500 degrees celsius and in theory the film should have a better quality. However this wasn't the ...

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