# 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.

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### 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: We were, however, able to complete a ...
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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 ... 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 ... 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 ... 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 ... 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) ... 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. ... 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 ... 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 ... 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 ... 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 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, ... 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 ... 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}\ \ [**].$$Elements that have the d-electron ... 6 votes 0 answers 389 views ### Density of non-ideal vapor mixtures I'm looking for a reasonably accurate density of a mixture of two gases that act quite unlike ideal gases (generally steam and water-miscible solvents). We can get a first order estimate by taking a ... 6 votes 0 answers 565 views ### Explaining the photoelecton spectrum of krypton The photoelectron spectrum of krypton is shown below. (where the x-axis is in electron volts (eV))\ Since both the 3p and 3d shells are more than half full, based on Hund's rules the lowest-... 5 votes 0 answers 152 views ### Interpretation of Helmholtz energy and Gibbs energy I know that this question has many other variations on this site, but I'm trying to see if I understood Helmholtz and Gibbs energy properly or not. The material I'm reading from is Physical chemistry ... 5 votes 0 answers 295 views ### Is the formation of nitrogen dioxide spontaneous? I was studying Thermodynamics from my Chemistry textbook (page 181-182, section 6.6 (a)). I have a question regarding the following text from my book. Now let us examine the following reactions:$$\...
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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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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, ...
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### 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 ...
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### What does "acidic" mean in an article on hydrogen boride nanosheets?

From Rojas et al.  (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 ...
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### 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 $$\frac{\partial c}{\partial t} = M \Delta \bigg(\frac{\partial \mu}{\partial c} - \kappa \Delta c \bigg),$$ ...
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### 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 $\ce{BaSO4}$, ...
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### 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}}{...
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### 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 : In the course of recent ...
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### 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 ...
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### 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 ...
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 ...