Questions tagged [intermolecular-forces]
The forces, either attractive or repulsive, that exist between molecules due to electric charges or varying electron cloud distribution. This tag could also include intra-molecular attractions (within one molecule itself) often found in a protein amino acid residues.
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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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Is there any material that, subjected to electricity, extends in size in multiples without substantial change in heat for human use? [closed]
Is there any material that can molecularly restructure so as to expand its intra- or inter-molecular distance by no less than three-fold without substantially losing its structural integrity and ...
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Analog of chemical accuracy in vibronic energy calculation [closed]
Is there any analog of chemical accuracy in vibronic energy calculation? I understand that the unit is /cm however, probably, I shouldn't expect a given number in that unit as the analog.
I am ...
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Are all humectants sticky?
While using a topical lotion based on ethanol, water and propylene glycol, I noticed that it becomes sticky while drying. Propylene glycol is a humectant and is used for this purpose in ...
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Why do atoms make bonds? [duplicate]
I have been studying chemistry for a long time in school till now, but, what I recently realised I do not understand is why do atoms really make bonds, why do they want to gain or lose electrons or ...
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Why does alkylamines have a higher boiling point than ammonia?
Here are the boiling points of ammonia and some amines:
$$ \begin{array}{|c|c|}
\hline
\textrm{Substance} & \textrm{Boiling Point} \\
\hline
\textrm{Ammonia} & \pu{-33.34^\circ C} \\
\textrm{...
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How are London Dispersion Forces generated?
While talking about the gaseous state of matter we came to the topic of London Dispersion Forces caused by the generation of a dipole in one atom which induces a dipole in another. While talking about ...
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Resource estimate for ab initio calculation [closed]
I have recently come across this very intriguing paper “The Fundamental Vibration of Molecular Hydrogen”.
I have asked the authors the following naïve questions directly via email?
What was the ...
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Does water really have strong EM absorption at 3 kHz in solid and 2 GHz in liquid? Why the huge shift?
While writing this answer to the question Transmitter receiver coil separation for Electromagnetic Terrain Conductivity Measurement I ran across this large PDF file of a book Soil and Environmental ...
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Why is the boiling point of fluorine lower than that of oxygen?
Fluorine boils at -188.1 °C and oxygen boils at -183 °C, but shouldn't $\ce{F2}$ boil after $\ce{O2}$?
Despite being electronegative elements, both are nonpolar molecules and posses dispersion forces ...
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Interaction energy of an hydroxide ion with a Pd surface
I need to estimate the interaction energy of a hydroxide ion with a palladium surface of $-0.6$V in water.
I know that the electric field of a charge $e$ is
$$
E = \frac{1}{4\pi\epsilon}\frac{e}{r^2}
$...
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Viscosity and repulsive forces
Suppose we let a ball move in a fluid with initial velocity $u_i$. Then as time goes on its velocity goes down and tends to $0$ after infinite time. I understand viscosity in the following way:
In ...
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Why does tetrachloromethane have a higher boiling point than trichloromethane?
London dispersion forces (LDF) are present in all molecules, whether polar or non-polar. Molecules also exhibiting dipole-dipole interactions (in addition to the LDF) must have stronger forces of ...
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What is the difference between a bond, force, and interaction?
I am trying to explain why some solids are more soluble in water than others.
So the energy released from the formation of bonds between the solid solute molecules and water molecules compensate the ...
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Comparison of hydrogen bond strength
Consider the following sets of H-bonds:
$$
\begin{align}
&\text{P:} &\ce{-O-H\bond{....}N} \\
&\text{Q:} &\ce{-O-H\bond{....}O} \\
&\text{R:} &\ce{-N-H\bond{....}N} \\
&\...
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Incompatibility of Helmholtz Double Layer and Redox electrochemistry
In an electric double layer capacitor(EDLC) (or any situation with a Helmholtz double layer) what prevents the ions from being reduced or oxidized like the ions in an electrochemical cell?
If it is ...
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Exceptions to the molar mass trend in London dispersion forces in molecules: do they exist?
"In general, larger molecules have higher boiling points than smaller molecules of the same kind, indicating that dispersion forces increase with mass, number of electrons, number of atoms or ...
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Physical origin of induction and dispersion energies
I am reading this book on non-covalent interactions. Chapter 1 states that there are 3 types of non-covalent interactions:
Electrostatic interactions, which are just the coulomb interactions between ...
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Reason for the formation of azeotropes
Why is it that some liquid mixtures (that exhibit positive/negative deviation from Raoult's law) form azeotropic mixtures at certain compositions? What is the physical reason behind this; are there ...
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Can Ion-Dipole Force Occur Between Lecithin and Water?
So, ion-dipole force occurs between an ion and a polar molecule. I would like to ask if an ion-dipole force would occur between water molecules and lecithin as seen in the picture, since it has a ...
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Intermolecular Forces in Teflon vs Polyethylene
From Wikipedia, polyethylene has a melting point of around $400K$, while Teflon (polytetrafluoroethylene) has a melting point of $600 K$, which is much higher. Besides the increased London Dispersion ...
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How does cross-linking between polymer chains increase the melting point of the polymer?
https://i.sstatic.net/uUcQr.jpg
Suppose we have this polymer chain. Now, we cross link some chains ( not all ) , so some chains get linked, and others remain as they are. What we now have is a '...
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How is relative interaction energy defined and quantified?
I understand the interaction energy is the energy associated or caused by the interaction between the objects. So, for atoms it has to be the sum of van der Waals interaction and Coulomb interaction.
...
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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 a ...
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What does Partial charge means in Dipole Dipole forces [duplicate]
Dipole-dipole forces act between the molecules possessing permanent dipole. Ends of the dipoles possess “partial charges” and these charges are shown by Greek letter delta (δ). Partial charges are ...
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Should there be a better explanation on Van Der Waals force? [duplicate]
The explanation on how Van der Waals force forms is this: Van der Waals forces consist of induced, temporary dipoles between neighbouring molecules. These are caused by constantly shifting electron ...
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Intermolecular Forces and State Change
I know that intermolecular forces determine the state of a substance at a given temperature and that changing state involves the ability of a substance to overcome those forces. I encountered a ...
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Fugacity vs compressibility
What's the criterion for saying that the forces of attraction are dominant?
f < p or Z < 1
I ask this because there is a situation where
f < p and yet Z > 1 (below Boyle temperature)
if ...
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What happens to the sea of electrons when a metal melts/boils? [closed]
I was taught about metallic solids with the sea of electrons model. My question is how does the sea of electrons function when metal turns into a liquid and a gas. The way I see a liquid is ...
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What are the intermolecular forces between the following compounds in a mixture?
I need to figure out the intermolecular force between the following compounds in a mixture:
acetone-aniline,
acetone-chloroform,
ethanol-acetic acid,
acetone-ethanol,
ethanol-water
Can someone ...
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Charge polarisation in acetamide molecule due to different lithium salts (varying anions)
I am trying to understand how will acetamide molecules behave in the presence of lithium salts with different anions (nitrate, bromide and perchlorate).
Among the three, it is evident that bromide is ...
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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 + ^1_0n}$$
I don't understand how the electrons add up. As alpha ...
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What does "the natural bond angle" mean in the context of Universal Force Field (UFF) potential energy calculation and how are bond angles calculated?
As the title says, what does "the natural bond angle θ0" mean in the context of Universal Force Field (UFF) potential energy calculation? The reference appears in section D. Angular ...
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Why does the PE becomes negative in potential energy versus intermolecular distance graph? [closed]
In the potential energy versus inter molecular distance graph, we know that atoms/molecules/particles want to be at optimum distance from each other ie $r_0$ and to the left of this position in the ...
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Intermolecular forces between polyatomic ions and water
I was wondering what kind of intermoleuclar attraction exists between nitrate ion $\ce{NO3-}$ and $\ce{H2O}$?
Is it ion-dipole attraction or is it hydrogen bonding? Since there is nitrogen and oxygen, ...
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Do CHF3 and acetone form a hydrogen bond?
I haven't been able to find a reference confirming that fluoroform forms hydrogen bonds with acetone. Do they?
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Sublimation of Iodine
Why does iodine sublime? I have researched it myself and I have got the same answer; it sublimes because it directly converts from solid to gas. But why don't bromine or chlorine also sublime?
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Why are hydrogen bonds in an antiparallel beta sheet stronger than those in parallel beta sheets?
Beta sheets are illustrated as such in most diagrams, where:
In an antiparallel β-sheet, the polypeptide strands are arranged such that a $\ce{C=O}$ and an $\ce{NH}$ from adjacent strands face each ...
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Why Ionic compounds dissolve into water
First, I would like to say that I understand the basic idea of disassociation and solubility. However, as I study intermolecular forces I feel like this basic Idea is being challenged. My ...
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Hydrogen Bond Length and Lattice Density [closed]
The subject of the density of solid water is discussed on Physics Stack Exchange in this post.
In the post, it is said that..
the way the molecule is angled ensures that a specific (energetically
...
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Which of these functional groups is soluble in aqueous HCl and/or NaOH?
http://pastpapers.papacambridge.com/view.php?id=Cambridge%20International%20Examinations%20%28CIE%29/AS%20and%20A%20Level/Chemistry%20%289701%29/2015%20Jun/9701_s15_qp_42.pdf
I need some help to ...
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What are the limits of size differences in a host–guest complex?
We learn in my chemistry course that there must be a snug fit for a host-guest complex to form. So, something like benzene (0.6 nm in diameter) can form a host-guest complex with a β-cyclodextrin host ...
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Strength of the hydrophobic interaction
How strong is the "hydrophobic force"?
Hydrophobic interactions are weak interactions but can have greater strength than hydrogen bonds. I find the strength of the hydrogen bond in ...
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Computational Chemistry: calculation of sterical effects
Is there a way to calculate sterical forces between atoms/groups of atoms (preferably with free and open source tools)? I have heard that this is possible within the framework of NBO. I am using ORCA, ...
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How to model a molecule of benzene surrounded by 100 molecules of water with molecular dynamics?
I have experience calculating molecular properties (mostly DFT). However, I would like to spend some time on molecular dynamics methods. I would like to ask your advice to direct me towards a program ...
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Differences between formulae for dipole–dipole interaction energy
I came across two formulae for dipole-dipole interaction energies on Chemistry LibreTexts — Dipole-Dipole Interactions:
$$V=-\frac{2\mu_1 \mu_2}{4\pi\epsilon_0r^3}\tag{3}$$
and
$$V=-\frac{2\mu^2_\...
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Why the boiling point decreases with increase in branching in alkyl groups?
I found out the answer is that
with increase in branching, the molecules attain a spherical shape with less surface area. As a result, interparticle forces become weaker resulting in lower boiling ...
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How do I figure out the relative polarity of organic compounds?
It's a question on my quiz which I guessed right and couldn't do the reasoning:
Based on the intermolecular forces, predict the boiling points of the following substances and list them in the order ...
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How are intermolecular forces between non-metallic substances affected when the substance is heated to its melting point?
I have 3 main questions that I am unsure of:
Are intermolecular forces acting simultaneously causing attraction between particles in a sample of a substance?
Example: Hydrogen bonding and dipole-...
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Intermolecular interaction Van Der Waals
In the empirical demonstration of the Van der Waals equation at Khan Academy, they made a demonstration of the real volume, for example, it was said that it has to be larger than the ideal volume, ...
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