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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How do non-polar substances dissolve in non-polar solvents?
The case of polar solvents is clear to me - we get an attraction between opposite charges. However, how do non-polar substances dissolve in non-polar solvents? How could it be explained on a molecular ...
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Why do dianions (such as malonate) bind cations more strongly than anions?
Why does a dianion (such as malonate) bind cations more strongly than its equivalent anion (acetate)?
Is it simply because of the proximal availability of another $\ce{O-}$ group that can bind to ...
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Is Hydrogen Bonding a Type of Dipole Dipole Interaction?
I understand that dipole dipole forces is due to the attraction of the different partials charges of atoms in different molecules due to their different electro-negativities.
For hydrogen bonding, ...
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How does intramolecular hydrogen bonding cause the molecules to be separated from each other?
I learnt about intramolecular hydrogen bonding today, which occurs between molecules such as ortho-nitrophenol. What I was told is that in case of intramolecular bonding, the molecules separate from ...
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Why do molecules having a higher relative molecular mass have stronger inter-molecular forces?
Why do molecules like alkanes with higher relative molecular
mass ($M_\mathrm r$) have stronger intermolecular forces? For example, methane ($\ce{CH4}$) has a weaker intermolecular force than pentane (...
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What's the relationship between Van der Waals forces and hydrophobic interactions?
A question on a past exam for a course I'm studying for asks:
What's the relation between Van der Waals forces and hydrophobic
interactions?
From what I understand, Van der Waals forces are ...
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Is an ionic bond more like a covalent bond or an intermolecular force?
I have asked a question loosely asking this, where I confused terms and did not specify what I wanted to know here, so I formed a new question.
What are the differences and similarities between ionic ...
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Alkane, alkene, alkyne boiling point comparison
Which of the following has higher boiling points? Alkanes, alkenes, or alkynes? And why?
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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 fluoroalkyl chains hydrophobic/oleophobic?
I'm searching for an answer that explains the hydrophobicity / oleophobicity in terms of intermolecular forces, but can't really find one.
Below is an example fluoro-alkyl nano-particle, F-POSS. It ...
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Can nonpolar molecules exhibit dipole-dipole forces?
Dipole-dipole forces occur when the positive part of a polar molecule is attracted to the negative part of a polar molecule. In a nonpolar molecule, there may still be polar bonds, it's just that the ...
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Why does silicon tetrafluoride have a higher melting point than sulfur tetrafluoride?
So looking at the Wikipedia pages of sulfur tetrafluoride and silicon tetrafluoride, the melting points are −121 °C and −90 °C respectively, and so $\ce{SiF4}$ has the higher melting point. However, ...
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How to identify hydrogen bonds and other non-covalent interactions from structure considerations?
Chemistry is governed by a wide range of interactions, from ionic and covalent bonding, or other types of strong interactions, towards weaker types of bonding, attraction, or repulsion, that typically ...
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Trend in the boiling point of the hydrogen halides
The boiling points of the hydrogen halides are as follows:
$$\begin{array}{cc}
\hline
\text{Species} & \text{Boiling point / }\mathrm{^\circ C} \\
\hline
\ce{HCl} & -85.1 \\
\ce{HBr} & -...
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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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Basis for the hydrophobic effect?
I'm confused about why hydrophobic molecules, which do not have high polarity, would have a tendency to attract and cluster with themselves. It is easier to understand the hydrophilic as long as one ...
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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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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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What are the different types of van der Waals forces?
As per different websites on internet van der Waals force are of
Three types (Keesom force, Debye force and London dispersion force) @ Wikipedia
Two types (Dipole-dipole force/Keesome force and ...
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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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Help understanding how "steric effects" are distinct from "electronic effects"?
@jakebeal's excellent answer to Why do animal cells “mistake” rubidium ions for potassium ions? includes the following passage:
In the case of potassium versus sodium, which are both very important ...
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Why is the pressure correction in the van der Waals equation proportional to (n/V)^2?
The van der Waals equation for real gases is stated as follows:
$$\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT$$
For the coefficient $b$, we can reason out that more the number of molecules, the ...
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Reason for the formation of azeotropes
Why is it that some liquid mixtures (that exhibit positive/negative deviation from Raoult's law) form azeotropic mixtures at certain compositions? What is the physical reason behind this; are there ...
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Why is the boiling point of heavy water higher than normal water?
In class, we learned that London forces become stronger as relative molecular mass increases. Not just in organic chemistry but in things like the halogens.
However, as I understand, the London forces ...
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Van der Waals nonspecific interaction definition
Every definition I see of Van der Waals interactions claim that they are short-range, nonspecific interactions between two chemical species. What does "nonspecific" mean in this context?
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Why do higher-mass isotopes have higher melting and boiling points than lower-mass isotopes?
Different isotopes of the same element have the same number of electrons, so the nature of bonding between different isotopes of the same element should be the same, yet their melting points and ...
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Why do chlorinated silanes have lower boiling points than their methane analogs?
The boiling points of the chlorinated silanes and methanes are given below:
$$\begin{array}{ccc}
\hline
\text{Species} & \text{Boiling point (X = Si) / }\mathrm{^\circ C} & \text{Boiling ...
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How are pencil marks "adhered" to the paper?
Pencils create marks by physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface. Wikipedia
Normal paper is mainly composed of cellulose ...
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Relation between molar mass and van der Waals force
In the book that I'm reading, it is mentioned that higher molar mass results in stronger van der Waals force but didn't continue why.
I wonder why is that so? Molar mass actually depends on the number ...
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For two compounds that are symmetrical, why does the more compact one have a higher melting point?
In this post, I refer to two molecules B (Di-tert-butyl ether) and C (Dibutyl ether).
Wikipedia: Di-tert-butyl ether (B)
b.p. 107.2 C
m.p. - 61 C
...
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Why do alkenes with more surface contact have greater London forces?
Why is it that alkenes with greater surface contact have greater London forces? I thought greater London forces were dependent on the size of the molecules, or the number of electrons, rather than the ...
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What is the connection between vapor pressure and intermolecular force explanations of boiling?
I've had boiling explained to me in two ways, and I'm having trouble understanding how they connect.
The first way is that a liquid is held together by the intermolecular forces, and boiling involves ...
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How does a water molecule bond to an anhydrous salt to form a hydrate?
Some sites suggest that water molecules bong to anhydrous salt via a "loose bond". What does that even mean? $\ce{H2O}$ is a polar molecule and salts are made up of ionic bonds. Is it a hydrogen bond ...
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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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Does oxygen gas form hydrogen bonds?
I learned that hydrogen bonding is formed from a 'sandwich' of hydrogen and either oxygen, nitrogen, or fluorine where nitrogen, fluorine, or oxygen is the bread.
Will oxygen gas and water form ...
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Trying to understand the causes and implications of kinks in fatty acid chains
I watched this video (The Deal with Fat by SciShow):
https://www.youtube.com/watch?v=mvvx2yQRbzQ
To summarize the main points I want to discuss:
Saturated fats are chains without any double-bonds ...
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What is the exchange interaction?
As the wikipedia article for the exchange interaction so aptly notes, exchange "has no classical analogue."
How wonderful.
Exchange shows up essentially while enforcing the condition that two ...
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Why are equations of state for a non-ideal gas so elusive?
The ideal gas equation (daresay "law") is a fascinating combination of the work of dozens of scientists over a long period of time.
I encountered Van der Waals interpretation for non-ideal gases ...
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Which intermolecular interaction is dependent on the inverse cube of distance?
The intermolecular interaction that is dependent on the inverse cube of distance between molecules is:
hydrogen bond
ion-ion interaction
ion-dipole interaction
London force
Inverse ...
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Arrange these compounds: CO2, CH3OH, RbF, CH3Br in order of increasing boiling points
Arrange these compounds: $\ce{CO2}$, $\ce{CH3OH}$, $\ce{RbF}$, $\ce{CH3Br}$ in order of increasing boiling points.
I think I should consider the forces between them, that is:
$\ce{CO2}$: dispersion ...
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What is the underlying chemistry behind the triboelectric effect?
I remember briefly studying the triboelectric effect in Physics but as I now approach the domain of Chemistry, I'd like to know what processes are involved (at the molecular level) when the the ...
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Why do single, double and triple bonds repel each other equal amounts?
I'm here to share with you something that totally confuses me, as I can't see the logic behind it, and my teacher doesn't know either.
Let's take a set of bonds that's trigonal pyramidal, with a lone ...
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At what frequency does a non-polar molecule acquire a dipole able to participate in London Dispersion forces?
London Dispersion forces are forces between non-polar non-ionic molecules that the random fluctuation of their electrons makes them temporarily dipoles.
What is the frequency that this occurs?
Every ...
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What forces hold ink on paper?
On regular paper, ink is absorbed, while on photopaper ink stays at the surface and dries for a longer time. What forces act in these two different cases?
(see also related questions about pencil ...
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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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Significance of single point energy when calculating interaction energies
I am currently investigating about the interaction behavior of a few atoms in certain conditions.
Is it possible to use the concept of single point energy to represent the atomic interaction energies ...
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Why is tetrafluoromethane non-polar and fluoroform polar?
Consider the Lewis dot structures of the molecules fluoroform, $\ce{CHF3}$, and tetrafluoromethane, $\ce{CF4}$:
My first line of thought is that both of these molecules are symmetrical (the ...
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How to calculate which ionic compound has the highest melting point?
Which of the following compounds has the highest melting point: $\ce{PCl5}$, $\ce{H2O}$, $\ce{NaCl}$, $\ce{SrCl2}$, $\ce{CaF2}$?
In general, ionic compounds will have higher boiling points than those ...
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How to calculate Lennard-Jones potential with quantum mechanical methods
I want to know the procedure to calculate the Lennard-Jones potential for a metal-halogen pair (specifically vanadium-chlorine). Is it possible to calculate using any QM packages like Mopac, NWChem, ...
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Do amines or alcohols have stronger intermolecular hydrogen bonds?
Which has stronger hydrogen bonding, $\ce{CH3OH}$ or $\ce{CH3NH2}$
I think it comes down to which has more dominance; number of hydrogens, number of lone pairs, or electronegativity.
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