Questions tagged [physical-chemistry]
The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.
841
questions with no upvoted or accepted answers
14
votes
0
answers
382
views
What is the largest coupled cluster calculation that has ever been done (as of March 2019)?
I am doing some research and trying to make sure the numbers I am reporting are accurate.
I found that the paper by Sylvetsky et. al. says:[1]
We were, however, able to complete a ...
- 141
12
votes
0
answers
243
views
Calculating Triplet-Triplet Spin-Orbit Coupling
According to the Q-Chem manual [1], the singlet-triplet spin-orbit couplings between a singlet excited state $I$ and a triplet excited state state $J$ is:
$$\langle\Phi_\text{singlet}^I|\hat{\mathrm H}...
10
votes
0
answers
163
views
In a molecular dynamics context, is the methyl rotation in propene a symmetric or asymmetric internal rotor?
In a prior question, I asked about the (a)symmetry of the potential energy surface of the methyl rotation of propene. In that context, the kinetic energy of the nuclear motions is of course assumed ...
- 17.3k
10
votes
1
answer
3k
views
Calculation of Atomic weight percentage in AAS
I am currently doing doping studies in a system similar to this ($\ce{A_{x}B_{1-x}}$) and I have to find atomic weight percentage of $\ce{B}$ element using atomic absorption spectroscopy(AAS). I have ...
- 2,740
9
votes
0
answers
251
views
Quenching rates in nucleation MD simulations
I am trying to perform nucleation simulations with molecular dynamics. To prepare the metastable fluid, I am equilibrating at temperatures about 30 K above the melting temperature, and then "quenching"...
- 421
9
votes
0
answers
502
views
multielectron spin-orbit coupling and energy level
For multi-electron atoms for which the Hamiltonian (including the spin-orbit coupling) reads
$$H=\sum_i T_i-Z\sum_i V_i+\sum_i V_i^{\text{s.o.}}+\sum_{i>j}V_{ij}$$
The $T_i$ are the kinetic ...
- 281
9
votes
1
answer
114
views
Will the sulfur-iodine cycle and Haber Method work at lower pressures and temperatures?
I have a year-long research project next year in my senior year of high school, in which we have to make some product or prototype to solve some issue.
My interest was in the Liquid Fluoride ...
- 91
8
votes
0
answers
4k
views
What are the limitations of the Born-Lande' equation?
The Born-Lande' equation is used to theoretically calculate the lattice energy, $\Delta U$, of ionic compounds. It is often cited as such in literature,
$$\Delta U = -\frac{k_Az_1z_2Me^2}{4 \pi \...
- 111
8
votes
0
answers
382
views
Why do chlorinated silanes have lower boiling points than their methane analogs?
The boiling points of the chlorinated silanes and methanes are given below:
$$\begin{array}{ccc}
\hline
\text{Species} & \text{Boiling point (X = Si) / }\mathrm{^\circ C} & \text{Boiling ...
- 3,840
7
votes
0
answers
166
views
Mathematical models of oscillatory chemical reactions
I am a mathematician working on real-life models in ordinary differential equations. I want to know if there are any models of oscillatory chemical reactions that consist of three ordinary ...
- 171
7
votes
0
answers
133
views
Is it possible to calculate electronegativity of surface atoms?
As the title asks, is it possible to calculate the electronegativity (EN) of specific atoms on extended surfaces (slabs), more specifically using computational methods? There are a few issues here I ...
user22967
7
votes
1
answer
2k
views
Beer's law: UV-Vis absorbance values exceeding 2
In classical analytical chemistry, absorbance values in Beer's law can theoretically range from 0 to infinity.
As general rule of thumb neither high, nor very low absorbance are used for ...
- 39.1k
6
votes
0
answers
204
views
How to determine the surface reaction rate and equilibrium constant for a reaction between a solid site species and gas species
Consider the following reaction mechanism 1:
S1: $\ce{C-H (s) + H (g) <=> C^\star (s) + H2 (g)}$
S2: $\ce{C^\star (s) + H (g) => C-H (s)}$
S3: $\ce{C^\star (s) + C2H2 (g) => C-H (s) + H(g) ...
- 71
6
votes
0
answers
137
views
Why is supersaturated sodium acetate so (meta)stable?
Sodium acetate is a common example used in general chemistry lectures to illustrate the idea of supersaturation, and that precipitation of a supersaturated solution can be initiated by a seed crystal. ...
- 161
6
votes
0
answers
372
views
Why is there preferential adsorption of a common ion during preparation of colloids by peptization?
There was a similar question asked here on Chem SE, but the answer was not very satisfactory to me, so I am asking a fresh question.
Peptization is the process of creating a colloid from a precipitate ...
- 503
6
votes
0
answers
178
views
Hund's rule for comparing term symbol energies in excited state
This question was asked in an exam:
The lowest energy electronic state for excited state carbon atom is,
a. $^1D_2$
b. $^3D_1$
c. $^3D_3$
d. $^3D_2$
Although we have been taught Hund's rule for ...
- 61
6
votes
0
answers
158
views
How to model CRISPR/Cas9 binding and cleavage using a generalized Kittel's zipper model?
I am thinking about how to model the binding of a CRISPR/Cas9+guide-RNA complex to a double-stranded DNA that cause its cleavage.
This post describes four steps at which a CRISPR/Cas9 system binds and ...
- 914
6
votes
0
answers
129
views
How do bonds rotate in pericyclic reactions?
In Pericyclic reactions, it is shown that the terminal bonds rotate (conrotation or disrotation) to allow for allignment of the FMO's, thereby forming the sigma bond
However, a detail that most of my ...
- 6,218
6
votes
0
answers
198
views
Approximating entropy change in a reaction using Arrhenius equation
Recently my teacher finished teaching the chapter Chemical kinetics in which I have gone through Arrhenius equation.Can we estimate the change in entropy using it? I have done my calculation, ...
- 1,391
6
votes
0
answers
1k
views
Mulliken Spin Density
I would like to know if a Mulliken population analysis to calculate spin densities is in general a valid choice. I see that it is made use of, for example here1. So up to-date researches apparently ...
- 161
6
votes
0
answers
541
views
Predominance of III oxidation state for lanthanides
For most lanthanide metals, the stable oxidation state is III [*]. The general electronic structure is $$\ce{[Xe] 4f^{0}^{-14} 5s^2 5p^6 5d^{0}^{-1} 6s^2}\ \ [**].$$
Elements that have the d-electron ...
- 7,021
6
votes
0
answers
389
views
Density of non-ideal vapor mixtures
I'm looking for a reasonably accurate density of a mixture of two gases that act quite unlike ideal gases (generally steam and water-miscible solvents). We can get a first order estimate by taking a ...
- 1,690
6
votes
0
answers
565
views
Explaining the photoelecton spectrum of krypton
The photoelectron spectrum of krypton is shown below.
(where the x-axis is in electron volts (eV))\
Since both the $3p$ and $3d$ shells are more than half full, based on Hund's rules the lowest-...
- 455
5
votes
0
answers
152
views
Interpretation of Helmholtz energy and Gibbs energy
I know that this question has many other variations on this site, but I'm trying to see if I understood Helmholtz and Gibbs energy properly or not. The material I'm reading from is Physical chemistry ...
- 247
5
votes
0
answers
295
views
Is the formation of nitrogen dioxide spontaneous?
I was studying Thermodynamics from my Chemistry textbook (page 181-182, section 6.6 (a)).
I have a question regarding the following text from my book.
Now let us examine the following reactions:
$$\...
- 125
5
votes
0
answers
85
views
Aren't electrophilic addition reactions of alkenes also nucleophilic addition reactions?
And if they are nucleophilic substitution reactions as well, then why do we not call them "electrophilic and nucleophilic addition reactions of alkenes"?
Consider the reaction between ethene ...
- 151
5
votes
0
answers
210
views
Splitting of atomic orbitals due to Stark effect
I am performing graduate level research on ZEKE Photoelectron Spectroscopy and central to this form of spectroscopy is Rydberg states and the Stark effect. The Stark effect is caused by an electric ...
- 59
5
votes
0
answers
135
views
Does π values vary in Hansch-Fujita equations for a given substituent?
I was reading about Hansch-Fujita equations from Hansch-Fujita paramaters and observed that the $π$ values of substituents (analogous to Hammet $σ$ values) change according to the specific environment ...
- 746
5
votes
0
answers
160
views
Stress-Strain Graph Under Uniaxial and Biaxial Strain
I was going through a recently published journal paper by ACS (Applied Nano Materials) about gas separation using nanoporous Graphene.
DOI No. - https://dx.doi.org/10.1021/acsanm.0c02340
Supporting ...
- 181
5
votes
0
answers
166
views
How is the Born-Lande equation modified when the structure is not NaCl?
Often the Born-Lande equation is quoted (alongwith the calculation of the Madelung constant and Born exponent) with reference to rock-salt structure. But what if we take some other crystal, like ...
- 395
5
votes
0
answers
492
views
Helmholtz double layer
I don't quite understand what is meant by the Helmholtz double layer.
Textbooks states something along the lines of:
the colloidal particles attain charge by selective adsorption, due to
this it ...
5
votes
0
answers
160
views
How to calculate a molecule's oscillator strength?
I was wondering how to calculate a molecule's (e.g. biphenyl) oscillator strength using a very simplified model.
If I want to calculate a molecule's excited states a good start is something like a ...
- 369
5
votes
0
answers
62
views
Computational modeling of steric repulsion between two polymer mediated magnetic Nanoparticle?
Can you recommend any modern article or research papers on steric interactions and forces between two or multiple magnetic nanoparticles with polymer brushes in a nonpolar solvents? something with ...
- 69
5
votes
0
answers
1k
views
What are the factors that affect the redox reactions?
In my work, I used $\ce{Co(OH)2}$ and $\ce{Ni(OH)2}$ as an active materials to fabricate as symmetric supercapacitors in which I used 1-butyl-1-methylpyrrolidinium dicyanamide as an electrolyte.
From ...
5
votes
0
answers
4k
views
Effect of temperature and pressure on structure of solids
What is the effect of these conditions on the structure of solids? My book has the answer that confuses me. I got nothing about it. Can you please explain? The answer of the book is
With the ...
- 161
5
votes
0
answers
1k
views
Why does diamagnetic current induce a downfield while the paramagnetic current induces an upfield shift?
I know that aromatic rings exhibit diamagnetic ring currents which causes the protons outside the ring to go downfield in H-NMR. Antiaromatic compounds exhibit paramagnetic ring currents which have ...
- 14.2k
5
votes
0
answers
809
views
Vapor-pressure or Vapor-concentration
To summarize from my textbook:
rate of evaporation:
proportional to surface area
but essentially independent from pressure (of surrounding gas)
rate of condensation
proportional to both surface ...
- 51
5
votes
0
answers
176
views
Analysis of metal carbonyl bonding in Fe(CO)5 using molecular orbitals
I am really struggling with this question we have been set in class:
Metal-carbonyl bonding: Conceptionally, one can build up $\ce{[Fe(CO)5]}$ from the $\ce{Fe(CO)4}$ fragment plus free $\ce{CO}$ in ...
- 51
5
votes
0
answers
129
views
Raoult's law: is the molar fraction the molar fraction in the entire system?
I have two physical chemistry textbooks, one by Atkins and one by Levine, which seem to differ in their notation used when describing Raoult's law.
Atkins talks about the molar fraction term in ...
- 803
4
votes
0
answers
202
views
Nephelauxetic effect and covalency of metal-ligand bonds
As I was reading about nephelauxetic effects, which is the effect that atomic d-orbitals are bigger in a complex than in gaseous metal ions. The Racah interelectronic repulsion parameter gets smaller, ...
- 276
4
votes
0
answers
61
views
Is there experimental evidence to show boiling point increases with external electric field, and if so, by how much?
I was wondering whether anyone has demonstrated that a liquid will have a higher boiling point if it is placed in a very large electric field. I believe to be the case, since induced dipoles would be ...
- 149
4
votes
0
answers
64
views
What does "acidic" mean in an article on hydrogen boride nanosheets?
From Rojas et al. [1] (emphasis mine):
On the other hand, we found that proton exchange with HB occurs in water with the estimated $\mathrm{p}K_\mathrm{a}$ of $3.5\pm 0.2,$ even after reactive sites ...
- 49
4
votes
0
answers
110
views
How to estimate the mobility constant and the surface energy parameter in the Cahn-Hilliard equation?
As a mathematician, I want to simulate phase separations with the Cahn-Hilliard equation
$$
\frac{\partial c}{\partial t} = M \Delta \bigg(\frac{\partial \mu}{\partial c} - \kappa \Delta c \bigg),
$$
...
- 193
4
votes
1
answer
215
views
Variation of conductance of saturated aqueous solution with temperature
The following question was asked in JEE Mains 2020:
Let $C_{\ce{NaCl}}$ and $C_{\ce{BaSO4}}$ be the conductances (in S) measured for saturated aqueous solutions of $\ce{NaCl}$ and $\ce{BaSO4}$, ...
- 466
4
votes
0
answers
69
views
Why does the factor of ⅔ come in when we calculate net flux due to diffusion for an ideal gas
As per Atkins' Physical Chemistry (11E) Pg:694. We arrive at a crude estimate for the net flux through an imaginary flux plane. We find it to be $$J_{z}=-\frac{1}{2}v_{mean}\lambda(\frac{d\mathcal{N}}{...
- 71
4
votes
0
answers
134
views
Why is there a large increase in volume when an alkali metal is dissolved in liquid ammonia?
My teacher said unexplainedly that when alkali metals dissolves in liquid ammonia, there is a large increase in the volume. I found a paper that confirms this fact [1]:
In the course of recent ...
- 156
4
votes
0
answers
91
views
Dominant factors rendering very low solubility of large aromatic molecules
In terms of structural basis, alkanes are insoluble or immiscible in water because of such presence of C–H...O interactions that are in regime of van der Waals interaction, which tends to be regarded ...
- 639
4
votes
0
answers
80
views
Regarding Ellingham diagrams
In my textbook, the following information is given about Ellingham diagram:
The interpretation of $\ce{\Delta_rG^\circ}$ is based on ${K}$ ($\ce{\Delta G^\circ = -RTlnK}$). Thus it is presumed that ...
- 519
4
votes
0
answers
428
views
Lindemann–Hinshelwood mechanism for a gas reaction
The effective rate constant for a gaseous reaction which proceeds by a Lindemann–Hinshelwood mechanism is $\pu{1.01E-5 s^-1}$ at a concentration of $\pu{4.6E-6 M}$ and $\pu{2.21E-5 s^-1}$ at a ...
- 1,085
4
votes
0
answers
157
views
Why is ruthenium dioxide a conductor while titanium dioxide is an insulator?
Ruthenium dioxide has the same crystal structure as rutile (titanium dioxide), and the metal atoms are in the same oxidation state. Yet ruthenium dioxide is a metal-like conductor (its resistivity is ...
- 213