For questions seeking generalised answers deduced from or composed of theories regarding the chemical reactions involved.

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8
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0answers
59 views

What would follow in the series sigma, pi and delta bonds?

I realise, that this question is a stretch, but I was wondering, how would a bonding orbital be called if it was formed from two $f_{x(x^2−3y^2)}$ or $f_{y(3x^2−y^2)}$ orbitals. Have there been any ...
1
vote
1answer
55 views

Is this a possible explanation as to why sigma bonds are stronger than pi bonds?

Sigma bonds form due to the axial overlap of two orbitals whereas pi bonds form due to their lateral overlapping. Since the former is more effective, we can say that sigma is stronger than pi. We mean ...
1
vote
2answers
78 views

Can we really beat the speed of light? [closed]

This is a rather physics question but I wanted to get an insight from a chemistry perspective. I heard from some that you can beat the speed or go faster than it but is that really true. Physicists as ...
4
votes
2answers
200 views

Why are sp hybridized carbocations high energy?

You don’t see carbocations on double bonds very much, and here’s a good reason: compared to sp3, there is more s character in the orbitals, so the empty orbital is held more closely to the ...
6
votes
4answers
101 views

Is there a field of chemistry that doesn't do experiments?

In other words, a field of chemistry that is all theoretical? I have heard of theoretical chemistry, but my chemistry professor said you can't really major in theoretical chemistry. He said the ...
5
votes
3answers
196 views

London dispersion forces and distance relationship

Why is the London dispersion force inversely related to distance but not to the second power but the sixth power? Why is there not an inverse square relationship as there is for Coulombic forces? Is ...
0
votes
0answers
30 views

Reducing NOx with Ammonia. Practical in a gasifier?

Sorry if this is an outright stupid question. I am no chemist... For Nitric Oxide: $2{NH_{3}} + 2 NO => 2 {N_{2}} + {H_{2}} + 2{H_{2}O}$ For Nitrogen Dioxide: $2{NH_{3}} + 2{NO_{2}} => ...
1
vote
1answer
26 views

What are the possible concentration pathways for a 3-species system?

Inspired by this question, which asks if a multi-species system could oscillate around its equilibrium, I thought about the possible concentration pathways the following more narrow specified system ...
1
vote
3answers
54 views

Why do molecular orbitals in solids merge to bands?

Why do molecular orbitals in solids merge to bands? For example: In silicon every atom is sp3 hybridised, but when I merge two of these orbitals then it yields a bonding and an antibonding MO. When a ...
3
votes
1answer
70 views

Unitary Transformation of the HF equations

I am working on a code to preform a HF procedure and I am a bit confused about the unitary transformation of the basis. My instructions are as follows. specify the basis and geometry (done) ...
1
vote
0answers
50 views

How can I contribute to the chemistry with mathematical theories?, what kind of math is most used in chemistry? [closed]

I'm curious in how mathematics can contribute to chemistry. I know that in theoretical chemistry is very useful the Group Theory and Symmetries. If I'm wrong in something, please let me know. By ...
1
vote
1answer
100 views

Does the ammonium ion hydrogen bond with water?

What about oxonium ions, such as hydronium ion? Do these hydrogen bond with water? If we see hydrogen bonding as a purely electrostatic phenomenon, then why not? Ammonium ion still has nitrogen ...
0
votes
1answer
72 views

Molecular Orbital Theory and No. of bonds

The order of filling of molecular orbitals $\ce{O2}$ by MOT is this : But from it, how can I deduce that there is one sigma and one pi bond in an oxygen molecule ?
6
votes
2answers
70 views

Dissociation of water into H+ and OH-: Does the law of mass action hold at nanoscale?

Suppose water under neutral conditions is confined in a virtual spherical nanocontainer with a radius of 25 nm. To calculate the number of hydronium ions, one uses water dissociation constant which is ...
1
vote
1answer
47 views

Elastic scattering of x rays in 3D: the principle for XRD analysis

I have some trouble visualising scattering of x-rays in 3D, since all textbooks and examples present it in 2D. Under I will share some reflections (no pun intended) about the elastic scattering of x ...
0
votes
0answers
25 views

How to calculate the amount of a polymer (PCL) in the chloroform:dimethyl sulfoxide (7:3) to get 9% solution?

I need to calculate the amount of the polymer [mg] in the chloroform/dimethyl sulfoxide with the ratio 7:3 relatively for producing 9% solution. I was using this formula for dissolving the polymer ...
7
votes
2answers
172 views

Carbon-Sulfur Bond Lengths; Resonance Effects (Or Lack Thereof)

Why is the C-S bond in $\ce{CH_2SH^-}$ longer than in $\ce{CH_3SH}$? Wouldn't there be resonance in the former, forcing the C-S bond to contract? ...
5
votes
1answer
157 views

Orbital overlap and size “mismatch”

Why is atomic size mismatch a sign of poor bond strength? Wouldn't orbital overlap be proportional whether the two atoms are small or the two atoms are big? For example I heard someone comment that ...
7
votes
1answer
478 views

Is cyclobutadiene anti-aromatic?

Cyclobutadiene is very unstable. But, some sources claim that this instability can be attributed to other factors such as ring and angle strain rather than antiaromaticity. Cyclobutadiene is simply ...
6
votes
1answer
135 views

Why F replaces axial bond in PCl₅?

Why does $\ce{F}$ replace an axial bond in $\ce{PCl5}$? I realize that it would be more stable there than at equatorial bond, but what is the reason of its stability? Similarly in $\ce{AB4}$ type of ...
0
votes
0answers
39 views

Conical intersections - phase

Can anyone explain why at a conical intersection the wavefunction changes sign? My understanding is that it is a test to see if the crossing IS indeed a conical intersection or just a coincidence of ...
6
votes
2answers
477 views

How does a Frost diagram reproduce the solutions to the wave equation?

I came across a Frost diagram for cyclic compounds in my book, and all my book had to offer was that it geometrically reproduces the solutions of the wave equation, and can therefore determine the ...
7
votes
3answers
331 views

Is the transformation of pi bonds to sigma bonds always energetically favorable?

Is the move from pi bonds to sigma bonds always favorable? My professor claims so, except in the case of conjugated pi bonds. I can see how pi bonds going to sigma bonds might be favorable; I know ...
13
votes
2answers
736 views

How many molecules does it take to have a phase?

A single molecule can't be solid, liquid or gas. It's just a molecule. A mole of something can be any of the three. So, how many molecules does it take for phases to be meaningful? I realize that ...
64
votes
3answers
9k views

Why is gold golden?

Bulk gold has a very characteristic warm yellow shine to it, whereas almost all other metals have a grey or silvery color. Where does this come from? I have heard that this property arises from ...
2
votes
1answer
25 views

Corrosiveness of Acid

Is the corrosive nature of acid relative to some substance quantifiable like acid dissociation constant (Ka)? If yes, what can be used to describe the corrosive nature of an acid? For example, it is ...
5
votes
1answer
178 views

Steric effects of a lone pair and piperidine

I know that in piperidine, the lone pair on the nitrogen can occupy either an axial or a equatorial position in the two chair forms. I also read that the axial position for the lone pair is preferred ...
1
vote
1answer
131 views

How can I presume what dissolves what?

Regarding solvents, the only thing I remember from school is my teacher saying: "The same dissolves the same." regarding the polar/non-polar solvents. From this I understand that water is polar ...
-3
votes
1answer
111 views

The stability of a “Di-onol” - carbonic acid - and analogies to cis-nitrous acid

to all the downvoters, if you could provide some constructive criticism, that would be helpful The reaction of carbon dioxide with water yields carbonic acid to some extent (0.4%) depending on ...
3
votes
1answer
106 views

Unequal ionization energies of methane

Why does methane have two different ionization potentials? How does this work? I understand that MO theory predicts C-H bonds of differing strength, while hybridization predicts C-H bonds of varying ...
5
votes
1answer
153 views

What is charge shift bonding?

Can someone explain to me charge shift bonding? I recognize that it is proposed as another domain of bonding - one different from ionic and covalent bonding. I am also told that C-F exhibits charge ...
0
votes
1answer
33 views

Which is the most intuitive to perform Dynamic Monte Carlo calculations?

I'm trying to find a (free is possible) code to perform Dynamic Monte Carlo calculations over chemistry systems. Which one is the most intuitive one?
0
votes
1answer
152 views

Dihedral angle of gaseous and crystalline HOOH

Why does hydrogen peroxide exhibit a dihedral angle of 111.5 degrees in the gaseous state? And a dihedral angle of 90.2 degrees in the crystalline phase? I know that in general, there is likely to ...
1
vote
0answers
142 views

Which d orbitals of sulphur take part in the pi bonds of SO3?

In $\ce{SO3}$ 2 $p\pi-d\pi$ bonds are present. But which 'd' orbitals of sulphur take part in these $\pi$ bonds ? The answer says $d_{xy}$ and $d_{yz}$, someone also told me that crystal field ...
2
votes
1answer
455 views

Why do we need acid when making acetone peroxide?

Acetone peroxide is a very dangerous explosive, easily detonated by mild heating, friction or shock. It appears in form of small white crystals. This compound forms from the mixture of hydrogen ...
7
votes
2answers
409 views

Utility of Bent's Rule - What can Bent's rule explain that other qualitative considerations cannot?

Does Bent's rule have any utility? I got a vehement earful for "NO." Points raised by my professor: Coulombic considerations can be used to rationalize bond angles, strengths, and lengths without ...
2
votes
0answers
65 views

Examples of intramolecular hydrogen bonding closing bond angles

Okay, we've established that intramolecular hydrogen bonding can exist in molecules, and doesn't always serve the purpose of closing the bond angle at least relative to other stereoisomers of the same ...
1
vote
1answer
188 views

How many empty orbitals do elements have?

A student was contemplating a question regarding elements with "no empty valence orbitals." An argument was made that elements all have infinite number of valence orbitals. Every atom basically ...
8
votes
1answer
221 views

Why is there sulfur in black powder / gun powder?

Black powder is composed of charcoal, sulfur and a nitrate salt. The charcoal and sulfur serve as fuel and the nitrate is the oxidizing agent. However, wouldn't it be cheaper to leave out the ...
3
votes
1answer
484 views

Energetic Placement of Atomic Orbitals in the HCl Molecular Orbital Diagram

How are the 3p orbitals of chlorine lower in energy than the 1s orbital of hydrogen?
1
vote
1answer
1k views

Hybridization in PH3

Does $\ce{PH3}$ exhibit $\ce{sp^3}$ hybridization? Arguments against hybridization: $\ce{PH3}$ is less basic than $\ce{NH3}$. This jibes with the supposition that $\ce{PH3}$ keeps its lone pair ...
4
votes
1answer
96 views

IBrF2 - van der Waals repulsions - and number of unique bond angles

I understand that the molecule $\ce{IBrF2}$ is T-shaped, with three ligand atoms and two non-bonding pairs. However, how many unique bond angles can this molecule exhibit? My professor argues for ...
7
votes
2answers
339 views

Are there any full worked examples of DFT calculations?

I just started learning DFT and now I am totally confused. Assuming I want to use B3LYP: \begin{align} v_s\left(\textbf{r}\right) &= v_\text{ext}\left(\textbf{r}\right) + \int d^3r\frac{n\left( ...
4
votes
1answer
61 views

How to obtain product ratio from energy differences via Boltzmann statistics

I am currently calculating some reactions and I would like to express the ratio of the products in per cents. I am using the Boltzmann statistic in the following way: The probability $p_j$ of a ...
6
votes
3answers
371 views

Do filled Orbitals also hybridize?

Recently I was watching a video on Valence Bond Theory, on the MIT Open-Course youtube channel. The teacher there said that for hybridization to occur, electron promotion from fully filled orbitals to ...
14
votes
1answer
623 views

When is it true that more nodes equals higher energy?

Consider all the MOs of some isolated molecule. (It could be a single atom too; I'll use MO to refer to AOs as well.) Number them in increasing order of the number of nodes (node = surface where the ...
5
votes
1answer
134 views

What stable arrangements of hydrogen-bonded water exist in the range of 4-20 water molecules?

Water clusters made up of various numbers of water molecules have been described. Are all of these structures theoretical? What experimental evidence supports any of these structures? How does the ...
2
votes
1answer
244 views

Schrödinger equation and wave function

What is the Schrödinger wave equation? What are radial probability functions, nodes-angular and radial and electron cloud? I am really confused with all these terms and all my book seems to offer me ...
1
vote
1answer
95 views

Molecular orbitals and “generalized” aufbau principle for heteronuclear molecular configurations

Is there any general ordering or rule for heteronuclear molecules like $\ce{AX_2}$, $\ce{AX_{n}}$, and their molecular bonding/antibonding configurations ($\sigma/\pi$ orbitals) accordingly to some ...
6
votes
1answer
202 views

How to make approximation of rotational partition function of diatomic linear molecules?

Using the rigid rotor approximation to the level energies, and such other appropriate assumptions, we can approximate rotational partition function, $Q_{\mathrm{rot}}$, of linear molecules as follows: ...