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Questions tagged [molecules]

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Vibrations in Stones and Crystals

I have read studies done that indicate certain sounds can either disrupt or reinforce the molecular structure (I think this is the terminology used) of living organisms. This is based on the idea that ...
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Incompatibility between the Bohr-Sommerfeld quantization condition and the Dunham expansion

I'm trying to apply the RKR (Rydberg-Klein-Rees) method which computes the classical turning points, $a(E,J)$ and $b(E,J)$ of a diatomic molecule for a rotational-vibrational energy value E, and ...
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How do gaseous molecules arrange themselves in liquids when they are “dissolved”?

To provide some context, I am trying to understand in better detail how oxygen from the lungs passes through a membrane and enters the vasculature in order to be transported via blood. I have ...
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1answer
21 views

Binding energy of a molecular ion?

The protons in the $\text{H}_2^{+}$ molecular ion are $0.106 \, \mathrm{nm}$ apart, and the binding energy of $\text{H}_2^{+}$ is $2.65\,\mathrm{eV} .$ What negative charge must be placed halfway ...
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Why is gaseous carbon dioxide transparent? [closed]

Some carbon-heavy products of combustion, e.g. soot, are black, as is carbon in other forms, e.g. graphite. This seems to suggest that carbon is black. But then how can $\text{CO}$ (carbon monoxide) ...
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Branch of Physics that Examines Atoms Relationships

Is there a specific branch of physics that can examine and calculate the strengths of atomic or molecular bonds and predict how they are going to break, putting into consideration the surrounding ...
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1answer
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When a diatomic ion dissociates, how does the electron density on each atom change?

Let's say, we have a fluorine molecule (F2), and we take 3 electrons from it, so now its bond starts to stretch, and at last the bond breaks and the two atoms are farther and farther away from one ...
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How many degrees of freedom for $\rm N_2O_2$?

From my reading, I have understood examples a diatomic molecule to be $\rm N_2$ or $\rm O_2$, however, the below seems to suggest that $\rm N_2O_2$ is also diatomic. Is this correct and can someone ...
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Selection rules in rotational spectroscopy- water molecule

The University of Liverpool maintains a ChemTube 3D page, where it says http://www.chemtube3d.com/spectrorotcd0-CE-TEST-ROTATE-ALL.html *> Highly symmetric polyatomic molecules, such as carbon ...
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Why don't asymmetric molecular orbitals and lone pairs in linear molecules lead to an additional degree of rotational freedom?

For example, in CO2, the molecule is linear and thus rotation about the intermolecular axis leads to an identical molecule. But if you consider the pi molecular orbitals, which are radially ...
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If one divides the molecular dipole of HCl by the interatomic separation, the result is not a multiple of the electron charge. Why is that?

I'm having some trouble understanding the reasoning behind the final note in the following worked problem: An HCl molecule has a dipole moment of $3.4\times10^{-30}\:\rm C\:m$. Assuming that equal ...
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1answer
68 views

Why hot molecules have higher velocities

I'm looking for a something different than the "T is average KE, heat is energy, so adding heat increases the KE and therefore T" explanation. Let's call that the "thermo" side of the argument, which ...
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1answer
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Bouyancy of ozone gas

If ozone is $O_3$ why is it an outer layer of the atmosphere? It seems $O_3$ would sink in a solution of $O_2$, rather than float on it.
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Van der waals forces interaction

My slides say: A gas with low density in which you can consider the attractive energy the sum of the isolate atoms couple $$ u=\int^S_\sigma{4\pi\frac{N}{V}}\left(\frac{\beta}{r^6}\right)r^2\...
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1answer
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Transparency and visibility of light in tyndall effect

Oil and water are both transparent however, they lose their transparency once they are mixed together. What is the reason for this? The size of the molecules are still the same so why does the ...
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Formulae governing the temperature at which molecules can form

This wikipedia page suggests that since stars are incredibly hot, molecules are unstable, and therefore materials exist primarily in their atomic state. Specifically, it states that "... the ...
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Degrees of freedom of gas molecules

What is the degrees of freedom of a three dimensional polyatomic molecule when only one vibrational mode is excited?
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64 views

Direction of the permanent dipole moment of the NH$_3$ molecule

What is the direction of dipole moment in a molecule of $\rm NH_3$? Is from hydrogen to nitrogen? Also do we take into account the dipole moment of the lone pair with hydrogen? When we must take into ...
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1answer
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What is quantum molecular movement? [closed]

Q: What is quantum molecular movement? And what are some examples of quantum molecular movement? I’ve been studying a wide arrange of things but one of the top things I don’t understand is quantum ...
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3answers
274 views

Would an $H_2O$ Molecule actually look like this 3D representation if we could see it?

I'm trying to get a much better grasp on atoms and molecules and I am a visual learner. I found the above image here. This intuitively makes sense to me because I can see how the electron orbitals ...
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1answer
38 views

Raman effect and IR absorption

Let's consider a molecule with N atoms, on which is shot a polychromatic IR beam. From the quantum selection rules, we know that in a single event of absorption only one of the 3N-6 oscillators can be ...
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1answer
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What's your favorite textbook on diatomic molecules?

I'm a grad student in AMO physics. I'm looking for another textbook to read on diatomic molecules. Could you please recommend your favorites? I've read 'Spectra of Atoms and Molecules' by Bernath and ...
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1answer
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Interaction between molecules

Does the interaction with enviroment change the geometry of a molecule ? for example in H2O the angle betwen H-O-H is 104.5 degrees. Does this angle change for example if the molecule of water is near ...
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1answer
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Why do low-precision gaskets & seals work?

In lots of applications water or gas-tight seals can easily be formed by tightening two surfaces together. These often consist of crudely made and inexpertly assembled parts, yet they seal so ...
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3answers
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Is “more added heat, more molecular vibration” an universal property? Or are there exceptions?

Is "more added heat, more molecular vibration" an universal property? Or are there exceptions? Do some substances work the other way around? Or do some other ambient properties modify this property? ...
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Degrees of freedom for diatomic molecules [duplicate]

I have a doubt in understanding about the degrees of freedom (dof) ......as I have learned dof is nothing but the necessary parameters to specify the location and configuration of a system.....if that'...
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3answers
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How do “pouring spouts” prevent liquid from escaping through the air intake?

You may be familiar with the types of pouring spout found in many professional cocktail bars, similar to the following: The hole on the top of the spout is an air intake, which connects to the narrow ...
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1answer
98 views

How is temperature related to quantum vibrational states of molecules?

When a molecule of greenhouse gas absorbs a photon of long wave infrared radiation it is boosted to the next allowed vibrational state. The vibrational state, as I understand it, involves deformations ...
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1answer
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Why is the transition from the $3s$ state to $3p$ state in nitrogen observable in the emission spectrum but not in absorption?

Why can one observe an electronic transition of the $3s$ state to the $3p$ state in the emission spectrum of the nitrogen atom, but not in its absorption spectrum? I know that the selection rules ...
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0answers
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Photoreactivity/photofragmentation dependence on pressure

Most of the photofragmentation studies I see are done in vacuum or lower pressure. Is this just because of the experimental limitations or the photofragmentation doesn't matter the surrounding ...
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1answer
87 views

Confusion between molar gas constant and boltzmann constant?

So after reading reading through internet I came to the conclusion that : For gas of any element PV/T = Constant of proportionality and that constant of proportionality can be expressed in ...
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2answers
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Would I be able to feel a single-molecule wide string?

Imagine there is a material that is so strong it can form several meters string while being only a single molecule wide. It is securely attached and can withstand any human pressure. What happens if I ...
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Radiation absorption by $CO_2$ molecule in atmosphere

What kind of radiation (light) does CO2 molecule absorb -UV or IR? I've read that it's infrared however some sources suggest ultraviolet. If so, how might it be possible?
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2answers
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How do $H_2$ lamps work?

When a hydrogen ($H_2$) lamp is subject to a high voltage hydrogen atoms release energy in the form of light. Somehow $H_2$ is splitted. But... Why high voltage produce the dissociation? Does ...
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1answer
101 views

Scientific explanation for smell? [closed]

This might be more on the philosophical side. We already know a lot about light. How it is generated and how it interacts with a material. Phenomenon such as Interference, Diffraction, the ...
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2answers
81 views

Commercially available material with highest density to cost ratio? [closed]

What are the top 5 commercially available materials (not limited to just the elements) with the highest density to cost ratio? To point to an application, say that my goal was to mass produce a solid ...
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0answers
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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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1answer
297 views

2 Extra Degree of Freedom in Linear Triatomic Molecules?

Ok, there is a bit problem in understanding Degree of Freedom of Linear Molecules specially of Triatomic Linear Molecules. See, the DOF in general is given as $f=3N-k$. Here, N=Number of atoms in a ...
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1answer
117 views

How does the graph of molar heat capacity point towards quantization of motion?

In the graph below, if we consider that the jumps are stepwise for a molecule, even then, how does it point toward quantization of vibrational and rotational motion? The thing it implies is that (...
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2answers
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For a molecule, does the term 'thermal vibration' mean the same thing as 'molecular vibration'?

When speaking of a molecule, do both terms ('thermal vibration' and 'molecular vibration') describe the same thing, being the one and only periodic motion of the atoms within the molecule? Or, are ...
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Classical theory fails to explain quantization of motions?

I understand everything written here. But the last point, I cannot get, at all. How does it point towards Quantization of the two motions, since the energy change is not sudden, but gradual? And if ...
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2answers
391 views

What is the difference between intermolecular (cohesive, adhesive) and van der Waals force?

I recently learnt that intermolecular force is the force of attraction between molecules and van der Waals force does the same so is there any difference ?
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1answer
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Simple question about molecules leaving a liquid at a temperature below the boiling point

My textbook asks the question why a liquid cools down when partial evaporation occurs just below the surface at a temperature below the boiling point. The answer is of course that only those ...
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1answer
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Equipartition of energy and degrees of freedom in Diatomic gas [duplicate]

Suppose we have a gas of $N$ diatomic molecules (ex $O_2$) with one-molecule hamiltonian being: $$\mathcal{H} = \frac{\vec{p}_1^2}{2m}+\frac{\vec{p}_2^2}{2m} + V(r_{rel}) $$ Where $r_{rel}$ is the ...
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1answer
111 views

How many elementary particles are contained in a molecule of $H_2O$?

I was wondering about how many elementary particles form up one molecule of $H_2O$. What I thought of is the following: Hydrogen : 0 neutrons, 1 electron, 1 proton; electron is elementary and proton ...
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2answers
462 views

Actual Degree of Freedom of Diatomic Molecule

Ok, I have 2 very different values for degree of freedom(DOF) of diatomic molecules arising due to the difference in the vibrational DOF of the diatomic molecules. According to this DOF wiki page:- ...
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O2 molecues speed in air, and their limit

Temperature is the proportional measure of kinetic energy of the random motion of the constituent micro particles in a system as per wikipedia. Now I understand that O2 molecules are randomly moving ...
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2answers
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If I would let something mix in the blender and let time go to infinity, will all molecules be separated eventually?

Just question out of curiosity. If I would let something mix in the blender and let time go to infinity, will all molecules be separated eventually, i.e. if I open up the blender it will be gas? Or ...
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1answer
162 views

Symmetry of ground state electron configuration

Take a molecule, whose atoms have a symmetry $S\in \text{O}(3)$ (i.e. S permutes the atoms). $S$ also acts on the wavefuncion $\psi(x_1,...,x_n)$ of the $n$ electrons in the molecule, by its action ...
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Can we (in principle) obtain molecular bound systems by modelling fundamental particles and their interactions?

Is it possible, at least in principle, to start with the Schrodinger/Dirac/Klein-Gordon equations to model elementary particles and their interactions and to obtain in the end molecular bound systems? ...