Questions tagged [intermolecular-forces]

The forces, either attractive or repulsive, that exist between molecules due to electric charges or varying electron cloud distribution.

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Why is the boiling point of ethyl fluoride lower than that of hydrogen fluoride?

The book, Solomons' Organic Chemistry (for JEE Mains and Advance), contains the following question: Hydrogen fluoride has a dipole moment of $\pu{1.82 D}$; its boiling point is $\pu{19.34 ^{\circ} ...
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Formulation chemistry. Can somebody suggest me an introductory book on this subject? [duplicate]

I am looking for an introductory book on formulation chemistry: the book should cover physico-chemical aspects in designing a formulation and also, if possible, the chemometric basic concepts used in ...
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Boiling points of ethylene, formaldehyde and oxygen

The boiling points of ethylene, formaldehyde and dioxygen are $\pu{-103.7 ^\circ C}$, $\pu{-19 ^\circ C}$, and $\pu{−183 ^\circ C}$, respectively. I expect formaldehyde to have the highest boiling ...
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Intermolecular Forces of Attraction [closed]

Imagine a bottle 85% filled with water and the rest is just air, and the cap is closed. Here are now my questions. Since the cap is closed completely, the air bubble is formed. Is that air bubble ...
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Solubility of alcohols in non-polar solvents

The solubility of an alcohol in a non-polar solvent (like hexane) increases with size of the alcohol, as the non-polar chain increases. However, as the chain keeps increasing, will the solubility ...
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How big does an atom need to be to have dispersion forces be greater than other intermolecular forces? [closed]

I know as an atom gets bigger the dispersion forces grow with it. But how big does an atom, e.g methanoic acid, to have dispersion forces that outrank dipole-dipole forces?
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Is Tkatchenko's MBD-NL method self-consistent?

I have a question regarding Tkatchenko's [1] new nonlocal many-body dispersion method (MBD-NL). Does anyone know if it's a self-consistent method? I read this paper many times but I'm still not sure. ...
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Morse interatomic potential

I am working with Morse interatomic potential, I searched through the Internet but I could not find any Morse parameters for Zirconium element. Is there any table, handbook or something like these ...
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Hessian Matrix and Physical directions: Potential Energy Surface

How do the eigenvectors of the Hessian Matrix for potential energy surface correspond directly to the physical directions of translation, rotation and vibration? I see that they might correspond to ...
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How to obtain curve energy and non-bonded interaction parameters (e.g. Lennard Jones parameters) with Gaussian?

I am parameterizing a force field and would need to obtain non-bonded interaction parameters of atoms (e.g., Lennard-Jones parameters). My primary idea is to obtain a potential energy curve using the ...
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When non-polar particles interact through dispersion forces, how fast does a temporary dipole induce a dipole in the neighboring molecule?

The current question is inspired by this existing question: At what frequency does a non-polar molecule acquire a dipole able to participate in London Dispersion forces?. In the comments and answers, ...
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Which has a lower boiling point, Ozone or CO2? Why?

Ozone is a bent molecule, and therefore, Ozone is a polar molecule. Polar molecules have dipole-dipole intermolecular forces. CO2 is a linear molecule, and therefore, CO2 is a nonpolar molecule. ...
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Distance Dependence of Weak Forces [closed]

I am currently taking a Biochemistry course and one of the topics on midterm covers various weak forces and its distance dependence. We covered: charge-charge (ionic) hydrogen bonds van der waals ...
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Why is the pressure correction added in the Van der Waals equation?

Since real gas particles experience attraction to each other, that means the pressure must be less from what we would expect. So why do we have to add a term to correct it? For example, in the ...
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What repulsion keeps non-hydrogen atoms at a distance: between inner shells or between nuclei?

Bonded or not, when two atoms or ions come closer than the bond distance or the van der Waals distance, the energy increases drastically. What is the underlying cause of that repulsion? The repulsion ...
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Why don’t compounds with high boiling points not necessarily have high attraction constants (a) in the Van der Waals equation?

You can find a list of constants $a$ and $b$ for the van der Waals equation in a Wikipedia website. Accordingly, hexane has a higher attraction constant ($a$) than that for water (24.71 vs 5.536), but ...
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Why aren't the Anton computers used more widely?

The Anton computers are purpose-built by DE Shaw research for molecular dynamics simulations. They achieve performance up to an order of magnitude faster than can be achieved with commodity hardware, ...
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Reason for the generation of London Dispersion Forces

While talking about gaseous state of matter we came to the topic of London Dispersion Forces while are caused by the generation of dipole in one atom which induces a dipole in another. While talking ...
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Can a gas have a boiling point?

For each of the following pairs, choose the member with the lower boiling point. Explain your reason in each case. HI(g) or HCl(g) If they were both aqueous solutions, I would know that HCl has ...
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Van der Waals forces [duplicate]

What exactly are Van der Waals forces? How do they arise and how can an instantaneous dipole cause another dipole? Shouldn't this make a chain reaction that causes all matter to eventually become ...
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Stability of alkenes

The following question was asked on myPAT website: I started with the solution by counting the hyper-conjugative structures available to each alkene. Based on this concept only, order is: I > ...
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DNA pairs (adenine-thymine, guanine-cytosine) [closed]

Well I was wondering why adenine pairs with thymine and cytosine pairs with guanine. From those pictures: Thymine has the lowest acidity and adenine has the biggest acidity. So it is logical that ...
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Why does chlorine gas have a higher boiling point than hydrogen iodide

Hydrogen iodide, $\ce{HI}$, is a dipolar molecule much larger than chlorine, $\ce{Cl2}$. The melting point of $\ce{HI}$ $(222.35\ \mathrm K)$ is definitely higher than that of $\ce{Cl2}$ $(171.6\ \...
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Does water really have strong EM absorption at 3 kHz in solid and 2 GHz in liquid? Why the huge shift?

While writing this answer to the question Transmitter receiver coil separation for Electromagnetic Terrain Conductivity Measurement I ran across this large PDF file of a book Soil and Environmental ...
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Why does roasting requires lower temperature than melting point

Why do processes like roasting and calcination require a temperature lower than the melting point? Since intermolecular forces are lower in a liquid won't it be easier to oxidise (roasting) / ...
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Freezing point vs Intermolecular forces

Water has a higher boiling point (100°C) than cyclohexane (81°C). This is probably because of stronger intermolecular forces between water molecules as compared to cyclohexane molecules. Then, why is ...
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How can we find out the type of bonding present in a compound or a molecule?

For example, if the bonding in diamond, ice, MgO or CO2 is to determine, how can I find it out? How to determine van der Waals forces?
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As you heat up a substance will it's bonds begin to dissipate?

As you heat something up does it slowly start to dissipate? Water, for instance, boils at 100 degrees Celsius, but if you are heating it up at 90 degrees will its bonds be weaker?
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dipole–dipole interactions: OCR Sample Paper wrong? [closed]

I was doing OCR A Level Chemistry A, H432/01 Periodic table, elements and physical Sample Question Paper. Question 6 was: The boiling point of hydrogen bromide is –67 ºC. The boiling point of ...
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Which has a high melting point, cocoa powder or cocoa butter?

I have been doing some research into chocolate, and after looking at the chemical compositions of cocoa butter and cocoa powder, struggled to determine which had a formula/structure that would have a ...
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Why are the dispersion forces in CS2 stronger than the dipole-dipole forces in COS?

London dispersion forces supposedly have the least strength out of all the intermolecular forces. But $\ce{CS2}$, which has only dispersion forces, has a higher boiling point (and thus stronger ...
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Why does CH2F2 have such a low melting point?

The molecule is highly polar but the melting points are way lower than non polar compounds such CCl4 or other similar non polar compound. Do even dipole dipole have an affect on boiling point or is ...
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Condensation point of molecule compounds?

Which of the following gasses will condense at the lowest pressure (Assuming temperature is held constant)? $\ce{CBr4}$ $\ce{CH2Br2}$ I believe that compound 2 will condense at the lower pressure ...
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Why does bromine increase the viscosity of olive oil? [closed]

Does bromine bond to the carbon in unsaturated fatty acids and break the double bonds between oxygen and carbon? Does this increase the viscosity of olive oil? Could someone give an elaborated ...
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Why does energy need to be “compensated” in order for solvation to occur?

I am currently learning about the physical properties of alcohols. I understand that the main intermolecular forces between alcohols and water are hydrogen bonds. When these two are mixed, the ...
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Why is casein hydrophobic?

According to this source hydrophobic behaviour occurs when a molecule does not have a charge or is neutral and therefore cannot be attracted to the negative nor positive parts of water. Casein has an ...
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How and why does glycerin have the highest dispersion forces between isopropyl alcohol and water?

How do dispersion forces affect the intermolecular forces by means of strength despite the hydrogen bonds? My teacher told that the structure of glycerin limits the hydrogen bonds but the dispersion ...
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Why is the Van der Waals constant of water lesser than benzene?

Van Der Waals constant of water and benzene ($a$) are $5.537$ and $18.82$ respectively. I have read that the value of Van Der Waals constant indicates the extent of attractive forces. By this, ...
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Boiling point of ethanamide vs propanamide

I just have a question regarding the boiling points of some primary amides. Ethanamide has a boiling point of 222 °C, while propanamide has a lower boiling point of 213 °C. Both amides are capable of ...
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Why does the exchange interaction in Hartree-Fock theory lower the total energy?

In Hartree-Fock theory, the expectation value of the total energy can be written as $$E = \langle\Psi| H |\Psi\rangle = \sum_{a} \langle a| h |a \rangle + \frac{1}{2}\sum_{ab} \big( [aa |bb] - [ab|ba]...
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What effect on boiling and melting points does intramolecular hydrogen bonding have? [duplicate]

I know that intermolecular forces increase the boiling and melting point of a compound, but what is the effect of intramolecular forces on boiling and melting points? I found contradicting answers ...
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Is the 12-6 Lennard Jones potential a good description of van der Waals interaction energy?

It seems to me that the Lennard Jones potential oversimplifies the more complex nature of van der Waals forces. However, in most of the MD simulation package, this is generally accepted.
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Can a long polymer chain interact with itself via van der Waals forces?

It is known that van der Waals interaction is an intermolecular forces. So is it possible that a long polymer chain interacting with itself via non-bonded interactions (such as van der Waals forces / ...
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What is a good resource for learning about the intermolecular bonding in water beyond high school? [closed]

I'm writing a paper for school on boiling water at various temperatures and pressures, but only noting cases wherein high temperatures were achieved without boiling under low pressure (metastable ...
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Radial pair distribution function (VMD). How to define it for a water NaCl system with multiple Na and Cl?

I'm struggling to understand a paper in which someone has presented radial distribution functions (RDFs) for a system that contains multiple Na, Cl, and water atoms/molecules. I don't know exactly ...
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How can I determine the highest boiling point given a list of molecules? [closed]

I know that the highest boiling point has to do with which has the strongest intermolecular force. I also know that the strongest would be ionic, then hydrogen bonding, then dipole-dipole, then london ...
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Ionic compounds and van der Waals forces

I'm having trouble understanding exactly what intermolecular forces occur in ionic compounds. What I understand is that ionic compounds are held together by electrostatic interactions between ...
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Complementary base pairing

In the molecular structure of a DNA it is seen that purines (adenine and guanine) bind with pyrimidines (cytosine, uracil and thymine) through hydrogen bonds, and this is always between a purine and a ...
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Why does graphite have a high melting point even though its intermolecular forces are weak?

From what I've read online, when a substance undergoes a state change, the intermolecular forces are broken. The covalent bonds are not broken (http://www.bbc.co.uk/schools/gcsebitesize/science/...
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What is the maximum distance over which van der Waals forces act?

The VDW radius places a lower limit on the distance between atoms mutually attracted to one another. I am looking for the upper limit: what is the name of the concept or theory that describes the ...

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