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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 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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40 views

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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61 views

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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51 views

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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124 views

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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44 views

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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171 views

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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1answer
47 views

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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152 views

Does gas chromatography follow the “like interacts with like” rule of thumb?

The "like interacts with like" rule of thumb works well when there are polar and non-polar molecules that are mobile (liquid-liquid extraction, membrane vs cytosol, questions of solubility). Polar ...
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2answers
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What would be the intermolecular forces between the molecules of methanetetrol?

Methanetetrol has the following chemical formula: $\ce{CO4H4}$. It is also referred to as orthocarbonic acid. Since the molecule has a molecular geometry of a tetrahedron, similar to that of a ...
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Why is boron or carbon solids and chlorine a gas at room temperature

I know different compounds have different states at room temperature because of inter-molecular forces ( dipole-dipole force, hydrogen bonding, and London dispersion forces). But how do they act on ...
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2answers
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Do molecules with polar bond, but with no dipole moment experiences a greater effect from the london dispersion forces?

Do molecules that have polar bonds and a structure that makes the polarity of those bonds cancel each other out, experience a greater effect from the London dispersion force, than molecules with a ...
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Non-covalent interactions

According to Keesom, Debye and London effect, the non-covalent reactions should be stronger, the bigger are electric charge differences between two interacting particles. E.g. Ion-induced dipole are ...
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What type of interactions occur when CH4 dissolves in CCl4 [duplicate]

When ionic compounds dissolve in polar solvents many types of factors come into play determining their solubility. Some of them may be: ion- dipole interactions, lattice energy, high dielectric ...
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Why do higher intermolecular forces lead to a higher change in temperature?

We performed an experiment in chemistry where tissue paper soaked in various chemicals was wrapped around the end of a temperature probe. The chemicals with stronger intermolecular forces had a lower ...
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63 views

Why does atomic charge not balance in nuclear reactions?

In the discovery of neutron, the bombardment of beryllium with alpha particles is well known. $$\ce{^9_4Be + ^4_2He^2+ -> ^12_6C + ^0_1n}$$ I don't understand how the electrons add up. As alpha ...
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1answer
61 views

Understanding water models?

I generally work on fluid flow, so some basic concepts in chemistry are new to me. Work I'm doing requires use of molecular dynamics (MD) to do classical potential simulations of water–NaCl systems ...
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51 views

How can I define a torsion force field for $n$ points in space?

I would like to define a model for torsion force field between $n$ point in space. I thought to generalize the OPLS model: $$ \sum_\mathrm{dihedrals} \left( \frac {V_1} {2} \left [ 1 + \cos (\phi-\...
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1answer
66 views

Calculate force on atoms given the energy of configuration, trajectory of simulation and position of atoms in each frame

Background I am using a neural network to calculate the potential energy of atoms in a configuration and then adding energy of all atoms to compare it with the true energy of the configuration(label) ...
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3answers
203 views

If all intermolecular forces are electrostatic in nature, why don’t large non polar molecule dissolve in water?

If I have a large non-polar substance A that forms strong dipole-induced dipole force (DIDF) with water, with strength comparable to that of H-bonds between water molecules, will A dissolve in water?
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Relative magnitudes of intermolecular forces from phase diagrams

Is it possible to say whether or not a system A or B has stronger intermolecular forces from a phase diagram according to which: The $T_{\text{b}}$ of A is lower than the $T_{\text{b}}$ of B. The $T_{...
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192 views

Intermolecular interaction between aniline and dichloromethane

Short background As it is known there are interactions between: Charges Charge and dipole Hydrogen bonding van der Waals (VDW) forces From stronger (1) to weaker (4). VDW forces are divided into ...
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1answer
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Relating properties and structures of polymers

Why would it be more favorable for a polymer designer to design copolymers with irregular chain structures, rather than design homopolymers? Hint: Discuss intermolecular bonds I understand that ...
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95 views

What are the intermolecular forces between polychloroethylene?

Does polychloroethylene have only van der Waals/London forces between its molecules? Surely, if all the chlorine atoms are on one side, due to the fact that chlorine is more electronegative than ...
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1answer
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Help with Carbon Fibre

I'm having trouble finding articles about carbon fibre that don't contradict other articles. I just have a few questions about the atomic structure and the intermolecular and intramolecular forces. ...
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1answer
65 views

Is the electrical conductivity only measurable in aqueous solutions? [closed]

I have been looking for other ways to measure it, but all I've found is through aqueous solutions. So I want to know if there's another way to do it, or why it isn't possible through other means.
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Why don't all atoms stick together due to dispersion forces if these forces are ubiquitous? [duplicate]

If dispersion forces are always there wherever there are electrons, why don't two pieces of copper for instance meld together when put next to each other? Or why don't other substances stick to each ...
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1answer
1k views

Why does Xe have a higher boiling point than Ne? [duplicate]

I am certain that the reason involves intermolecular forces, but since both $Xe$ and $Ne$ are noble and non-polar gases, shouldn't these forces have a much smaller effect or negligible on boiling ...
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Why do intramolecular forces weaken due to heat?

In my most recent research into thermoplastics, I was unable to find any information regarding what actually happens to intramolecular forces when heat is applied.
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83 views

Experimental bond lengths and binding energies of diatomic molecules

Is it possible to find the experimental values of the bond length and the binding energy of the diatomic molecules $\text H_2$, $\text{Be}_2$, and $\text{Ar}_2$ in one source? I found a lot of ...
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1answer
159 views

Will ice be cold or not when formed using pressure? [closed]

We know that ice can be formed either by lowering the temperature of water or by applying more pressure. If we lower the temperature of water the ice so formed will be cool which is obvious. If ice ...
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2answers
97 views

What makes a diatomic bond strong? [closed]

What are the factors affecting the strength of bonds? Ex:- why, we need less amount of energy to break Br-Br bond than Cl-Cl bond?
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1answer
120 views

electronegativity and hydrogen bonding [duplicate]

I have a basic idea why, but can someone just confirm, why chlorine isn't able to hydrogen bond despite the fact that it has the same electronegativity value as nitrogen.
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How to know if a sample suffered descomposition during melting point? [closed]

If I take a sample in order to determine its melting point, how do I know if that sample suffered a descomposition?
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What is “time-dependent evolution of the complex noncovalent interaction networks” and why this is important?

From Maximilian Scheurer, Peter Rodenkirch, Marc Siggel, Rafael C. Bernardi, Klaus Schulten, Emad Tajkhorshid and Till Rudack Biophysical Journal, Volume 114, Issue 3, 577-583: One of the most ...
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371 views

London Dispersion Forces and Dipole-Dipole forces together? [closed]

How do London Dispersion Forces and Dipole-Dipole forces exist at the same time between polar molecules?
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1answer
80 views

Van der Waals interaction and magnetic dipole dipole interaction

I have a conceptual question that bothers me. From what I understand, van der Waals forces are the primary source of inter-molecular interaction. There are three different possible origins for van ...
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2answers
2k views

Why do alkanes have higher boiling point than their ether counterparts?

Based on my understanding of inter-molecular forces, I expect dipole-dipole interactions to be significantly stronger than van der Waal's interactions. Hence, I expect ethers (which obviously have ...