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The boiling point of non-ionic compounds are highly depend on their H-bonding abilities. For example, boiling point of water (molar mass: $\pu{18.02 g/mol}$) is $\pu{100 ^\circ C}$ at $\pu{1 atm}$ while that of ethanol (molar mass: $\pu{46.07 g/mol}$) is $\pu{78.4 ^\circ C}$ at $\pu{1 atm}$, even though ethanol is heavier and have more other intermolecular ...


9

Mathew Mahindaratne has provided analysis based on experimental values of the boiling points of the two compounds. I would like to offer a different view using bonding analysis. Before I begin tackling the question, we shall first clarify the concept of the hydrogen bond. While the popular view of the hydrogen bond is as a particularly strong type of "...


7

Protein dynamics occur in multiple different time scales. I myself is a person using MD simulation for my research. One reason I am not so much interested in ANTON is not it's cost, limited resource etc. It's rather because one extremely long simulation wouldn't help much at least for my research. Protein's thermodynamics as well as kinetics all depend on ...


7

I think you have the causality backwards here. It's not as if we have the vibrations to start with and they happen to be matched by the eigenvectors of the Hessian. We choose to look at these particular vibrations precisely because they are the eigenvectors of the Hessian. Consider the example of water. We know that it has it has $9$ degrees of freedom, ...


7

To start off, you definitely need to use dispersion-corrected density functional methods if you want to obtain reasonable non-bonded interaction parameters. I've seen many cases where B3LYP (with no dispersion) yields a fully-repulsive potential energy scan. I also agree with your assertion about doing a rigid scan. In principal, a relaxed scan is a good ...


6

It does not have much to do with entropy, rather with the way and place of ozone creation. Stratospheric ozone is produced typically at altitude 20-30 km by UVC radiation with $\lambda \lt \pu{280 nm}$: $$\ce{O2 + \nu -> 2 O}$$ $$\ce{O + O2 -> O3}$$ See ozone cycle as courtesy of @M. Farooq. Ozone in lower troposphere troposphere is created by UVB (...


5

The three reasons that you present are not sufficient to explain the high boiling point of pure $\ce{HF}$. There is a fourth reason, that you have not mentioned : the Hydrogen bond. Molecules $\ce{HF}$ are interacting with one another through $\ce{H}$-bonds, exactly like $\ce{H_2O}$ molecules attract one another because of $\ce{H}$-bonds. In the liquid state,...


4

I don't know if anyone is still looking for the answer but here I go anyway because I spent 40 minutes researching this for an assignment TL;DR - The better solubility of potassium salts is the key factor, but not in the way one would initially suspect. Industrial processes and the efficiency of large-scale soap making explains the choice. The reason why ...


4

The upper limit are typically optical light frequencies. That is where the very last plateau is reached in dielectric spectroscopy. The electron shell becomes purely elastic. I wrote a bit more about DES in my answer here: Difference between relaxation and resonance leading to an absorption spectral feature?


4

Anton and its successor Anton2 are highly specialized pieces of machinery. In fact, the computer, the chip, and the only code that can run on the chip are all called Anton. There's a reason why the only Anton computer outside of D.E. Shaw is located in the Pittsburgh Supercomputing Center (Anton now deprecated there, replaced by Anton2): this highly ...


4

No. Steel is a generic term referring to an alloy containing iron and carbon (with iron as the main component) and various types/qualities of steel contain many other additional elements, e.g. nickel, chrome, manganese, etc. to give or enhance different properties in the alloy. If it is not iron-based, it is not steel. As for alloys using metals from the ...


3

There are many ways in which bond lengths can be changed, and these will be accompanied by changes in bond energy. I will give examples for four different classes of substances, though they may not all count as "forcing" the bonds to be shorter in the way in which you mean. You can look these over, and perhaps clarify your question: Glasses: ...


3

The polarizability of molecules determines how a molecule interacts with other molecules (intermolecular interactions and chemical reactions), how it interacts with electromagnetic radiation (optical properties), and how it interacts with electrical fields (electrical properties). Thus, there are multiple ways to compare the polarizability of two molecules ...


3

You are correct in your ideas. The effect is important in the van-der-waals interaction and appears as an additional $1/r^7$ term compared to the usual $1/r^6$ term. (This is sometimes called a retardation effect). It is present only at larger distances (a few nm) and arises only in induced-dipole interactions (dispersion interaction) because of the time it ...


2

Assuming that by air bubble you're referring to the pocket of air now sealed in the bottle above the water surface: Immediately after sealing the bottle, the air pocket is not at all compressed: it's at the same pressure as the surrounding environment (the air outside the bottle). However, because you have a closed container, some water will evaporate, ...


2

It does seem that placing the hydroxyl group at the terminal carbon maximises the hydrogen bonding interactions between alcohol molecules and also the van der Waal forces between them. This is best illustrated with a crude diagram I have made: Finer differences due to the position of the hydroxyl group along the chain, such as the differences between the 2- ...


2

If there were no attractive forces solids and liquids would not exist The very existence of liquids and solids depends on attractive forces. two molecules that don't attract will never form a liquid or a solid. Liquids and solids only form because, under certain conditions of temperature and pressure, the attractive forces between their constituent molecules ...


1

Distance In vacuum, the calculated (classical) interaction between to aligned dipoles decreases with the square of the distance. If the dipoles can't come very close to each other, the interaction will be weak. If you treat hydrogen bonds as a special case of dipole-dipole interaction, you will find that a N-H ... O=C interaction is much stronger than a C-H ....


1

When a $\ce{H}$ atom is bound to an electronegative atom like oxygen, its only electron is mostly placed between the two nuclei. Outside of this $\ce{H}$ atom, the $\ce{H}$ nucleus is nearly "naked". Speaking naively, there is no other electron to occupy the space around the nucleus towards outside. It looks as if the nucleus $\ce{H}$ is not ...


1

So the intermolecular forces would be stronger in glycerol then in acetone. Glycerol can form hydrogen bonds while acetone is not very polar and can’t significantly form h bonds with itself. The surface tension for glycerol is 63.4 $\frac{mN}{m}$ while acetone is 25.2 $ \frac{mN}{m}$ (both @ 20 C) I supposed the error in your experiment arises from using ...


1

I would say that your analysis of first, second and fourth one is correct, as H-bonds are stronger than dipole-dipole interactions. However, you made a mistake while filtering compounds having dipole-dipole interaction. The $1$ and $3$, both have dipoles! The $\ce{C=O}$ bonds in $\ce{CO2}$ are polar and hence they possess dipoles, but unlike a water molecule,...


1

I suggest that an entropic term explains the little difference observed. While this aspect is normally important to justify what isomer melts at lower temperature, in principle it can be invoked to justify why an isomer having a longer - not too much - branch boils at a bit higher temperature. In this case, which might be rare as for a balancing between ...


1

Technically, the concentration and positioning of ozone in the atmosphere likely relates directly to both ozone formation, stabilization and a destruction cycle. While formation creation cycles has already been outlined, I would like to add more detail on the chemistry based on this source: Creation: $\ce{O2 + ℎν → 2 O• }$ $\ce{O• + O2 → O3 }$ which is ...


1

“Branched chain” simply means that the main carbon backbone has other, smaller carbon backbones coming off of it. You’re correct, a hydrogen atom would have to be removed from a carbon atom in order to attach another polymer chain. Generally, branched chains decrease the density of a polymer because they fill space less efficiently than a perfectly straight ...


1

The primary thing to realize is that, although the ozone molecule has a bent structure, it is a homonuclear molecule. This means that between the individual oxygens, the bond moments being formed are quite less, as inherently, both the oxygens have the same Pauling electronegativity values. Only a slight difference in the same will occur, due to the ...


1

I think we are thinking too chemically, i.e., too basically. From my (limited) experience, soft soaps contain more water. The correspondence of viscosity or some other measure of strength or hardness with water content is not exactly identical for the sodium and potassium soaps, but it is fairly close. If you make a potassium soap with low water content, it ...


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