texts:
To draw the structure of $\ce{ClO2}$, I tried to find the hybridization of the central atom i.e $\ce{Cl}$. I figured out that there would be two $\ce{Cl - O}$ double bonds, which means $\ce{Cl}$ would have 4 bonding electrons. But this assigns 3 electrons as nonbonding residing on the $\ce{Cl}$ atom. So, $\ce{ClO2}$ is an odd electron species.

Then, how do I find its hybridization and draw its structure?

Can I not just count the number of σ bonds and the number of lone pairs as usual, i.e, considering the 3 non bonding electrons as 1 lone pair, and find the number of hybrid orbitals and thus, find its hybridization? This gives the answer of $\ce{ClO2}$ being $\ce{sp^2}$ hybridized and it's geometry being trigonal planar. Is this the correct answer? Am I right in my determination of bonding and nonbonding electrons of the atom or is there something special in this compound $\ce{ClO2}$?


texts: How will the degree of conjugation effect the light emitted? (glow stick reaction)

texts:
So regarding the chemiluminescence in a glow stick reaction, the glow is due to the unstable compound 1,2-dioxetanedione decomposing into carbon dioxide, releasing energy which is then absorbed by the electrons in the molecules of the dye. This promotes the electron to an ‘excited state’ and when the electrons fall back to their ‘ground state’, they emit photons of light, where the exact energy of the light given off is dependent on the structure of the molecule.

Since I learned in organic chemistry that the more conjugated the molecule, the less energy required to promote the electrons to an excited state, I assume that is the reason why more conjugated systems (in the photo, Rhodamine B) emit lower frequencies of light (red), since lower energy is required to excite the electrons.

Am I correct?

In addition, if that is so, wouldn't the amount of conjugation of dye affect the efficiency of the chemiluminescence reaction? So for example, since more conjugated systems require less energy for the electrons to be excited, they will emit more light with the same amount of energy compared to less conjugated systems that need higher energy (emits higher frequency light).

I have asked my teacher multiple times, but she does not provide me with a satisfying question, I pray for help.

Thank you.


texts: Is steric inhibition of resonance, or of protonation, dominant in 0-substituted anilines?

texts:
There's a question about inhibition of resonance:

Is steric inhibition of resonance or steric inhibition of protonation dominant in o-toluidine?

If you look at Martin's answer he says that CH3 is not bulky enough to cause steric inhibition of resonance. What if I considered a group such as ethyl or propyl or even bulkier, then would we observe SIP (steric inhibition of protonation) as well as steric inhibition of resonance?

What would dominate?


texts: Alfa-Cypermethrin 97% Techwater solubility

texts: Aloha, I am a farmer in Hawaii and have been having problems with fire ants. I recently purchased a kilogram of Alfa-Cypermethrin 97% Tech, a pesticide that I find is not soluble in water. I would really appreciate it if someone could advise me how to make it water soluble in a 5% solution. I have no knowledge of chemistry.  Thanks for any help you can provide.


texts: What is the compound I made from KNO3 and table sugar which subsequently exploded when I exposed it to a flame?

texts:
I mixed 75% $\ce{KNO3}$ and 25% $\ce{C12H22O11}$ (by volume) in boiling water to make slow burn fuses. Some of the product became a thick brown paste.

After drying, a hard cake of an approximate 1 tablespoon amount exploded when lit. What compound did I make?


texts: How does cooling increase the selectivity of a reaction producing the kinetic vs the thermodynamic product?

texts: I know that cooling gives a lower ratio of molecules with sufficient energy to overcome the activation barrier, but I'm not sure how this selects for a kinetic or thermodynamic product. I also know that the kinetic product is favoured if there is not enough energy supplied to reach equilibrium, and the opposite for the thermodynamic product. Can cooling select for either product in different circumstances?


texts:
I am trying to use Open Babel (OB) to compute universal force field (UFF) given an xyz file. I read each xyz file and turn it into a pybel molecule. Here is the code I have so far

def xyz_to_smiles(fname: str) -> str:
    mol = next(pybel.readfile("xyz", fname))
    smi = mol.write(format="smi")

    return smi.split()[0].strip(), mol

def get_qm9_OB(target_index=np.arange(0, 133884)):

    smiles = []
    molecule = []
    for i in target_index:
        mol_idx = f"{i+1:06d}"

        tmp_smiles, tmp_molecule = xyz_to_smiles('../dsgdb9nsd.xyz/dsgdb9nsd_' + mol_idx + '.xyz')

        smiles.append(tmp_smiles)
        molecule.append(tmp_molecule)

    return molecule, smiles

molecules, smiles = get_qm9_OB(target_index=np.arange(100,200))

for i in range(len(smiles)):
    mol = molecules[i].OBMol

    ff = ob.OBForceField.FindForceField('UFF')
    ff.Setup(mol)

    ff.GetAtomTypes(mol)
    ff.GetCoordinates(mol)
    for at in ob.OBMolAtomIter(mol):
        type = at.GetData("FFAtomType") # an OBPairData object
        print(type.GetValue())

Now, I am trying to compute bond stretching interactions. My questions are:

How can I get the UFF constants for bond stretching? (IOW, is there an OB equivalent for RDKit function GetUFFBondStretchParams?)
Is there a function to calculate bond stretching interactions for each bond? (IOW, is there an OB implementation of either harmonic oscillator or the Morse function?)
How can I get coordinates from OBAtom object? I found GetCoordinate() but the output is

<Swig Object of type 'double *' at 0x1a1eb4a9f0>

Alternatively, GetVector() outputs

<openbabel.vector3; proxy of <Swig Object of type 'OpenBabel::vector3 *' at 0x1a1fbddbd0> >

How can I get the actual values?

P.S. I posted the problem on OB mailing list, with no answers.


texts: Hoping for a little help identifying this lab glass , I don't know anything about lab glass , this was in a storage unit I'm purchased at auction,,, there is what I think is called a condense & 2 round beakers or flasks,, one is 50ml & the other is 200ml ,,, all the male & female connector are marked SJ GSA CO 28/15 ...PLEASE is there anything you can tell me about what there are called & what they would be used for.


texts: Why does a tetrahedral molecule like methane have a dipole moment of zero?

texts:
I was studying chemical bonding when I noticed something odd.

We say compounds like $\ce{CCl4}$ and $\ce{CH4}$ have a tetrahedral geometry (which is a 3D structure) but when we talk about their dipole moments, we say they have no dipole moment. We give the reason that as the H atoms are opposite each other (hence assuming it to be a 2D structure), they cancel out their bond moments.

But why? In the beginning we saw that they are 3D structures with one H being at the top and other 3 at the bottom, with the bond dipole moment directed from each H towards C. Due to this the component of the bond moment of the 3 downward H atoms along the line of the upper H atom would cause a net upwards bond moment which is not equal to zero.

But certainly I am wrong as these values have been calculated scientifically. So can someone please point out where i am going wrong in my understanding?


texts: Why is a hydroxyl group more activating than a methoxy group in electrophilic aromatic substitution?

texts:
Why is phenol more reactive towards electrophilic substitution than methoxybenzene? Isn't the lone pair on the methoxy group oxygen more available for participating in resonance into the ring than the lone pair on hydroxyl oxygen due to the +I effect of the methyl group? Or is it because of the steric hindrance of the methoxy group that will favour lesser substitution at the ortho- position of the benzene ring?

Does the hydrogen bonding of phenol have anything to do with this?


texts: Do minerals and/or metals found in water tend to settle to the bottom?

texts:
I was reading an article that suggested that if one lets water sit for a day in a bottle or pot, then some of the metals in the water, such as lead, will settle to the bottom.

Does anyone know if this theory has been tested?

The reasoning seems somewhat logical, since particles in water tend to sink to the bottom. However, at the molecular level I know that ionic interactions may cause unintuitive behaviors.

I do have a TDS and pH meter. Perhaps I could let water sit for a day, then check the TDS of the water on top. Then compare that with the TDS of water that has been thoroughly mixed. Does anyone see any flaws with this idea?

  Excessive toxic metals.

  Many city water supplies, especially wells,
  contain some excessive amounts toxic metals or toxic amounts or forms
  of other minerals.  Common toxic metals include arsenic and lead,
  which are found in many pesticides and herbicides and find their way
  into the wells and other water supplies.  At times, these are
  difficult to remove from large amounts of water, so they are just left
  there even if the water violates environmental standards, especially
  in poorer nations.

  Other minerals that often contaminate drinking
  water include too much iron, manganese, boron and copper depending on
  the location. One way to remove some of these easily is to let a
  pitcher or pot full of tap water sit for a day and some of the metals
  will settle to the bottom of the pot.

  You can then pour off the
  water, leaving most of the minerals in the bottom of the pot.  You may
  lose some beneficial minerals this way, but it is one way to remove
  some toxic metals, as well.

-Dr. Lawrence Wilson

http://www.drlwilson.com/ARTICLES/WATER.htm#INTRO


texts:
$\ce{HgCO3.3HgO}$ and $\ce{HgO.Hg(NH2)Cl}$ are called basic mercury carbonate and basic mercury amidochloride, respectively. I found this thread on the former; I've only seen the latter as the product of a qualitative test in one of my textbooks, and Google yields nothing on it.
Is "basic metal salt" a general term for salts of the form $\ce{M_yB_x.M_2O_x}$(M the metal, B some anion with valency y, x the valency of the metal) or is it just for some compounds of mercury? If it's just for mercury, which ones more are there?
Are there any "acidic salt" analogues? If so, what general formula do they have?


texts: Dr. Stone making Acetone from Seashells and Wood vinegar

texts: Could you make Acetone from boiling seashells and wood vinegar as said in Dr. Stone? I haven't found anything online that says whether or not it will work.


texts: Discerning Chemical Relatives: Salicyl salicylate and Methyl salicylate

texts: Oil of wintergreen or methyl salicylate is found in Gaultheria procumbens.  The molecular similarity to salicylic acid strikes me as obvious. The hydrogen is replaced by a methyl group.  But am I jumping to conclusion I wonder.  I've seen plenty of molecules which are said to have the same structure, but fail to see it because my knowledge of chemistry is limited.  How do chemists define structural similarity in molecules?


texts: How does the cathode of an electrolytic cell drive the anode reaction?

texts:
Consider this electrolytic cell:

In this cell, electrons from the anode of the battery travel to the cathode of the electrolytic cell, where hydrogen ions are reduced into hydrogen gas. This drives the oxidation reaction at the anode, where hydroxide ions are oxidized into oxygen gas.

My question is: How does the reduction reaction at the cathode drive the oxidation reaction at the anode? They aren't connected by a wire or anything, so there is no electron flow from the cathode to the anode like in a galvanic cell. Also, since this is an electrolytic cell, the reaction is non-spontaneous.

Some possible hypotheses:

The galvanic cell just gave some of its electrons away, so it is negatively charged and sucks in the electrons from the anode of the electrolytic cell, forcing the oxidation reaction to occur. However, assuming the galvanic cell has a salt bridge, shouldn't ions be able to compensate for this?
The loss of positively charged ions at the cathode causes a buildup of negative charge in the cell; the anode tries to compensate for this. However, how do electrolytic cells involving the reduction of water, which has neither a positive or negative charge, into hydrogen gas occur?


texts:
I'm reading up on molecular modelling and have come across some terms I should probably have learnt a long time ago but always scared me off a bit with the Greek letters. I guess I'm a big boy now so it's probably time to clarify...

The textbook uses the lowercase symbol omega ($\omega$) for torsion (a.k.a. dihedral) angle while Wikipedia gives the uppercase, $\Omega$, plus both upper and lower case phi ($\Phi$, $\phi$) and psi ($\Psi$, $\psi$) in its description which from reading I'm starting to understand designate particular geometrical cases from the article, though it looks like it might be a little difficult to remember at first.

My textbook also gives in the list of symbols and physical constants [lower case] tau, $\tau$, but I can't see any mention of this on the Wiki page.

Firstly I wanted to ask is the use of upper/lower case totally arbitrary, and secondly is tau just a non-specific way of expressing torsion angle compared to the other 3 (which is the only use I can imagine for it?) Or is this use totally confined to molecular modelling?


texts: What are the border definitions in the Ramachandran plot?

texts:
I've heard some people mention that this or that program isn't "up to date" with respect to the borders used in the Ramachandran plots to classify φ/ψ as being in the most favorable/acceptable/disallowed regions.

How are the accepted regions defined?  What is the current accepted paper that covers this?


texts: Sodium and potassium produce a strange liquid, why the liquid explode when it gets contact with water?

texts:
I saw an experiment sodium and potassium mixed together to produce a liquid alloy  but when the liquid get contact with water then some kind of explosion occur.

Why the explosion occur when the liquid  made contact with water?

Same explosion will occur if it would get contact with other form of liquid?


texts: So I have this molecule shown up here and I need to give its systematic name according to the UIPAC and need to give its R/S configuration in the name. I suspect the name to be 3-tert-butyl-2-methylheptan-4-one but I don't know the R/S thing however.


texts: Why don't polar and non-polar compounds dissolve each other?

texts: Dipoles can also be induced in polar and non polar compounds, then why don't they dissolve?


texts: How reliable would commercially available starch be as a standard for an experiment?

texts:
I am conducting a student experiment of finding the amylose to amylopectin ratio of certain samples using an iodine colorimetry method. In order to calculate the actual ratios, I need a standard to base my calculations on.
Ideally I would use a pure amylose standard, but due to practical limitations, am not able to obtain this. Instead, I am considering using a few different commercially available starches (potato, tapioca, wheat), and treating literature values for amylose : amylopectin ratio as a standard.
My concerns are whether the ratios of the starches I purchase would be consistent with literature values, and possible discrepancies between species; I am hoping that tapioca starch at the least would be reliable, as it is the only species of Manihot esculenta.
Would this method be reliable at all, and are there any alternatives?
Thanks


texts: Are there any hazardous products that would come from mixing glass cleaner with lubricant?

texts:
Are there any known safety issues if you mix:

Mr.Muscle glass cleaner
GT85 spray lubricant


texts: What's the difference between demixing temperature and cloud point?

texts: I am learning something about polymer solution which has LCST phenomenon. But I met researchers used demixing temperature and cloud point to describe the transformation of this kind of solution from solutable into insolutable state. But for me, they seem the same. So I ask it here to learn what is the difference between these two concepts?


texts: How do I isolate calcium from calcium carbonate?

texts: I have the ability to use many kinds of reactions, and the use of most common acids/bases.


texts: An aqueous solution of sodium hydrogen carbonate corrodes aluminum foil quite readily. How do you explain this?


texts: Best Cheminformatics API for drawing SMARTS reactions?

texts:
I have a need to automatically draw SMARTS reactions. Rdkit's drawings are suboptimal. OpenBabel's drawings don't work properly on macOS. Indigo's drawings are cut off half the page.
I would love to use ChemDraw, but I can't seem to find an API for it to draw reactions with SMILES/SMARTS. I would absolutely be willing to write a wrapper to do this if there is a nice API to actually programmatically do drawings headlessly.


texts: Why do heavy metals like mercury and lead have an affinity for sulfur or sulfur compounds?

texts: Many of the heavy metals such as mercury, lead, thallium, cadmium, and arsenic exert toxic effects largely by binding to or otherwise interfering with organic sulfur compounds or groups in the body. What is the chemical reason that many of these heavy metal elements and their compounds seem to bind easily to sulfur and sulfur compounds?


texts: Stabilisation of carbocations through hyperconjugation

texts:
Our teachers told us that greater the number of alpha H, greater is the stability of carbocation.

But consider this:

$\ce{CH3CH2+}$      and.      $\ce{CH3CH2CH2+}$

The first one has 3 alpha H while the second one has 2. So first one is more stable, as our teachers say. But even C-C sigma bond can participate in hyperconjugation, isn't it?

Going with that, second one has equal no bond resonating structures and even higher inductive effect of ethyl group. So second one should be more stable (without overruling the dominance of hyperconjugation).


texts: Is it two isomers with at least one stereogenic center each but the corresponding center on the other isomer will rotate the plane of polarized light in the opposite direction. Is this applicable to meso compounds which aren't chiral overall but have stereogenic centers?


texts: What will be the major product in the following reaction?

texts:
My approach-
Since a base is added the compound will release hydrogen ion.

My problem is from where will the ion be released?
Benzene ring containing bromine is more activated than the other benzene ring. So it should be difficult to extract hydrogen ion from it. But I am getting my answer right by doing so. Shouldn't hydrogen be removed from the other benzene ring?
Also how do we know how many hydrogen ions will release? Is it necessary that only one hydrogen ion is released?


texts: How to calculate the rate of formation of a product when given the rate law?

texts:
The following data are given for the reaction of $\ce{NO} \text{ and } \ce{Cl2}$:

$$\ce{2NO + Cl2 -> 2NOCl}$$
The reaction is second order in $[\ce{NO}]$ and first order in $[\ce{Cl2}]$,
and the  initial rate equals $\pu{1.43E-6 mol L^-1 s^-1}$ at the instant when $[\ce{NO}]_0 = [\ce{Cl2}]_0 = \pu{0.25 mol L^-1}$.

The problem then says:

Calculate the rate of formation of $\ce{NOCl}$ when $[\ce{NO}] = [\ce{Cl2}] = \pu{0.11 mol L^-1}$.

I thought it's just $(2) × (\pu{9.152E-5})× [0.11]^2[0.11]$, which is $\pu{2.44E-7}$,  but the answer provided is half that $(\pu{1.22E-7})$, so I must have gotten the rate equation incorrect.
Is the rate of formation of $\ce{NOCl}$ equal to twice the rate of the reaction, as when I consider this reaction equation: $\ce{2NO + Cl2 -> 2NOCl}$?
Or is the rate of formation of  $\ce{NOCl}$ directly equal to the rate of the reaction, as when I consider this reaction equation: $\ce{NO + 1/2Cl2 -> NOCl}$?
I'm really confused how to tell which of these two approaches to use.


texts: Why are spherical compounds with a half filled HOMO concidered aromatic?

texts: In planar annulenes, huckel's rule effectively states that compounds with a full HOMO for their conjugated $\pi$ systems are considered aromatic while those with a half filled outer shell are antiaromatic. Aromatic compounds are stabilized both by delocalization across their $\pi$ complex and possessing a full HOMO spread across the ring. On the other hand, antiaromatic compounds break degeneracy among their orbitals, preventing resonance, as it would only result in a half filled outer shell. Despite this, according to this source, a half filled HOMO in a spherical compound will result in aromaticity on a sphere. Is this because there is so much potential for delocalization in spherical compounds, since they contain so many conjugated pi bonds, or can this be explained with something else?


texts:
I have been considering building a fluid dynamics demonstration.  Basically, it would be a thin plexiglass box, with some turbulence inducing elements attached to the back face, and a pump to move the fluid around.

Can anybody recommend a pair of fluids that will:

not mix/dissolve permanently
can be dyed different colors, while respecting (1)
won't react with plexiglas (or, alternatively, polycarbonate)
isn't toxic or particularly flammable
can be pumped with a "very" low power pump at temperatures suitable for humans (say, 60-100F)

The point of the demonstration is to create a "sustainable" chaotic system.  I might even point an HD camera at it, and extract random numbers from the video stream (maybe).


texts: How is a photoelectron spectrum assigned?

texts:
The photoelectron spectrum of a given molecule is commonly used as experimental evidence of the energy ordering of molecular orbitals (See here:
10.4: Photoelectron Spectroscopy, and many other physical chemistry books).
How is the experimental photoelectron spectrum assigned? Depending on the molecule you can do an accurate electronic structure calculation, but can it be correctly assigned using only the information in the spectrum (and selection rules, maybe)?


texts: Why, during aspirin synthesis in acidic conditions, anydride carbonyl oxygen is protonated rather than salicylic acid carbonyl oxygen ?

texts:
The common route for aspirin synthesis (described here) employs acetic anhydride and salicylic acid, in acidic conditions.

The first step of such a reaction mechanism is the protonation of the carbonyl oxygen of acetic anhydride.

Why, instead, protonation of carbonyl oxygen in salycilic acid should not occur ? Of course, such a protonation is not desired, since it won't lead to aspirin: however, can it be neglected and why ?

Thanks for any hints.


texts: Why does this reaction produce an alcohol in one case and an alkene in the other?

texts: Does it have something to do with the fact that the chlorine atom is bonded with the primary carbon, or with higher temperature in the upper reaction?


texts: explanation of why interphase occurs in polymers

texts:
Im new to chemistry network of stackexchange so please be kind to me!
I heard that interphase is created in clay polymer for 2 reasons.
one of the reasons is the insoluble part of the polymer and the second reason is for second TG.
can some one please explain how these 2 factors cause interphase? or can you recommend articles?
thanks in advance


texts: At what temperature (in kelvin) are most of the elements on the periodic table liquids?

texts:
This question is out of pure curiosity.

At what temperature are a majority of the elements on the periodic table in a liquid state/phase of matter? For the purpose of this question, assume the standard pressure (100,000 Pa). Is there some sort of formula or theorem that explains this? Please give a detailed explanation on your conclusion.


texts: What is maximum energy level of molecules?

texts:
I have been reading about the relation of molecular graph spectrum, that is, the set of eigenvalues of the Laplacian matrix of the molecular graph, and molecular properties. Recently, I came across a paper that finds an upper bond for maximum eigenvalue (DOI: 10.1109/ICNC.2012.6234727). To motivate their research, authors state that

  The eigenvalues of adjacency matrix of the graph is used to present
  the energy level of specific electronic. Particularly, spectral radius
  of graphs is the maximum energy level of molecules.

I was wondering if anyone can elaborate on what maximum energy level of molecules is. Is it the maximum energy level among all the atoms of the molecule?


texts: Is a compound composed out of gold, manganese, xenon, krypton, and oxalate possible?

texts:
Please keep in mind while reading this that I do not intend to create this, it is part of the backstory for a video game I am producing.

I created a compound based on knowledge from my chemistry class and Wikipedia.
The formula is: $\ce{AuKr4Xe2C2O4^2-C2O4^2-MnO4-}$

The 2D structure looks like:

And the 3D Structure is:

I believe the IUPAC name would be Aurodixenichexakryptic permanganate dioxalate (please correct me if I am wrong).

I know the molar mass is $\pu{1089.7413 amu}$.

It is a thick, black liquid similar to Vantablack, as in it absorbs $99.99\%$ of the light hitting it, making it seem two-dimensional. It is odorless and tasteless.

I determined the melting point to be $0.01~\mathrm{K}$ and boiling to be $\pu{7538384392 K}$. The density under normal conditions is $\pu{89.45 g mL-1}$.

I was hoping someone could tell me is all the information thus far was valid and if someone could provide me other key facts about the compound (i.e. alternate names, $\mathrm{pH}$, $\mathrm{pOH}$, $\mathrm{p}K_\mathrm{a}$/$\mathrm{p}K_\mathrm{b}$, etc.)


texts: Why is there only little difference between molecular dipole moments in CHX3 compounds (X = Cl, Br, I)?

texts:
Why is there only little difference between molecular dipole moments in $\ce{CHX3}$ compounds ($\ce{X}$ = $\ce{Cl}$, $\ce{Br}$, $\ce{I}$)?

As we can see there is a huge difference in dipole moment of methyl halides $\ce{F}$, $\ce{Cl}$, $\ce{Br}$, $\ce{I}$ excluding $\ce{CHX3}$.

Please explain the reason why is it so only in $\ce{CHX3}$ but not in other methyl halides?


texts: Are bond orders always the same in isoelectronic diatomic species?

texts:
In my textbook of chemistry it is written that:

  In the Lewis description of covalent bond, the Bond order is given by the number of bonds between the two atoms  of a molecule.
   ...
  Isoelectronic molecules and ions have identical bond orders; for example, $\ce{F2}$ and $\ce{O2^{2-}}$ have bond order $1$. $\ce{N2}$, $\ce{CO}$ and $\ce{NO+}$ have bond order $3$.

I tried some more molecules and it turns out that for two diatomic isoelectronic molecules (neutral or charged) the bond orders are always the same.

My question is that :

If the bond order is always same for isoelectronic species (diatomic  molecules and ions) how can I prove it? I tried and got the following result:

  For any diatomic molecule having combination of elements of same period( either period 2 or period 3) isoelectronic molecules and ions have the same bond order.

  Proof: Assume the two atoms $A$ and $B$ ( atoms may be ions also) having valence electrons in their outer shell $x$  and $y$.
  Now if they combine to form diatomic molecule or ion having bond order $m$ then they must satisfy the below two equation( octet rule):
  1) $x+m=8$
  2) $y+m=8$

  Now since they are along same period therefore the total no. of inner electrons( total electrons excluding valence electrons) must be equal( 2 electrons for period 2 elements and 10 electrons for period 3 elements). If we vary the atoms(or ion) $A$ and $B$ the sum of these inner electrons will obviously be constant( equal to 4 electrons for period 2 elements and 20 electrons for period 3 elements).

  Therefore, For species to be isoelectronic:
  $x+y=constant$( say $k$)
  Adding equation 1) and 2) we get:
  $x+y+2m=16$ or
  $k+2m=16$ or
  *Bond order*$=m=(16-k)/2$ which is constant.  Q.E.D.

If the result given in my textbook is not true (since it looks like the fact is universal! compare $\ce{HCl}$ and $\ce{F2}$ which are isoelectronic having same bond order but elements in $\ce{HCl}$ involves period 1 and period 3 elements) then please state any counter examples.


texts: Yama Cold Brew Tower: what are these lab parts / components?

texts: When viewing this on a shopping web site, one of the reviewers indicates "This is about 50-60 [dollars] worth of pyrex glass and another 20 [dollars] worth of wood."  The company charges $499 for this setup, so I'd like to find out if there is any truth to this statement by identifying the parts and seeing how much they cost.  Image of the setup below:


texts: How can I find out the concentration of chlorine in an acid bath?

texts:
A professor I have gave the class this question, can anyone help? This is the first part of the question. (Also, my professor is from Bangladesh...so yea...)

It's the year 2395, and the world is in chaos. Two nations have conquered the world, USA and Bangladesh. You have been hired by Bangladesh's government to monitor acid baths used to remove oxidation on aerospace metallic material desperately needed for the new   F-95 fighter jet engine.

The acid bath is made up of three components:

25-30% HNO3
4-5% HF
Balance H2O

Unfortunately, a spy has broken into your facility and added large amounts of Chlorine to the acid bath. As the lead chemist, it is your job to determine how much Chlorine was added to the acid bath.

During sample collection, it is uncertain what any of the concentrations are, however once a sample is obtained you may manipulate it with any method you wish. Devise a method to determine the concentration of chlorine in the solution.


texts: Rotovibrational selection rules for symmetric tops

texts:
The selection rules for symmetric top molecules are

$\Delta J = 0, \pm1$ and $\Delta K = 0$ for $K \neq 0$ (parallel transition)

$\Delta J = \pm1$ and $\Delta K = 0$ for $K = 0$ (parallel transition)

$\Delta J = 0, \pm1$ and $\Delta K = \pm1$ for $K = 0$ (perpendical transition)

My question concerns the possibility of a $\Delta J=0$ transition. For example, the only way how $\Delta J =0$ is possible for linear molecules is with degenerate normal modes (e.g. $\ce{CO2}$ bend), as these can "evolve" into one another and give rise to vibrational angular momentum, which ensures that conservation of angular momentum can still hold regardless of $\Delta J$.

The fact that $\Delta J =0$ is allowed for all transitions of symmetric tops means that there is vibrational angular momentum associated with all of them. My questions are:

What is the origin of vibrational angular momentum if the normal modes involved are not degenerate? Can you help me visualise it, for example for the $\ce{C-Cl}$ stretch of $\ce{CH3Cl}$ (a parallel non-degenerate transition)?
Why is the selection rule different for $K=0$ and $K\neq0$?


texts: Non stationary effects of molecular orbitals

texts:
We have been learning a bit about molecular orbitals in class.

However, we have always considered things under a quasistatic approximation.

What are some effects that can only be explained by not using the quasistatic approximation ?


texts: Why doesn't water wash off the coronavirus alone?

texts: So the coronavirus has a lipid bilayer where the hydrophilic heads are facing outward. So why can't water just stick to these ends and flush out the virus particles from our hands? Is it because our hands stick better to the virus? If so, why and how does the virus stick better to our hands than water?


texts: I am trying to construct all the matrices for the point group D3d operations.   I find that the matrices of E, i, S6, inverse of S6, C3, and inverse of C3 are easy,  but I do not know how to construct the matrices of the three C2s and the three dihedral reflections.   When I construct these matrices,  they do not look like those of usual reflections or rotations.   I cannot find any resources about finding these more complicated matrices.   Any help would be appreciated.


texts:
In "The Greatest Show On Earth", author Richard Dawkins spends a chapter discussing radiometric dating. I find myself confused by the following lines, though I'm sure the reason is elementary. (excellent pun and emphasis both mine)

  Among all the elements that occur on Earth are 150 stable isotopes and
  158 unstable ones, making 308 in all. Of the 158 unstable ones, 121
  are either extinct or exist only because they are constantly renewed,
  like carbon-14.

What is meant by "occur on Earth" and "extinct" here? I take "extinct" to mean "decayed to the point that it cannot be detected". If I am using that word correctly, then in what sense does an extinct element "occur on Earth"?


texts:
My grandparents stumbled on some cheap  Heinz Apple Cider Vinegar while cleaning their house.

  Ingredients: Made from the juice of apples diluted with water to a uniform pickling and table strength of 5% (50 grains) acidity.

Barring the origin and 1% difference in acidity, how does it differ from Heinz® All Natural Cleaning Vinegar? Is Apple Cider Vinegar equally as potent for cleaning clothes and the house?

  Ingredients:
  Made from select sun-ripened grain, diluted with water to a special cleaning strength of 6% acidity.

Beverly Leestma purports that the brand beneath at Walmart didn't indicate "the acidity but did state it was “Not For Food Consumption." Some vinegars (like this Industrial Strength Cleaning Vinegar) are still 5% but aren’t refined or purified to be food quality."

Assuming that the industrial strength cleaning vinegar's acidity is also 5%, then why can't it be consumed?
Why must raw vinegar be refined or purified for human consumption?
Is Beverly Leestma correct in her wariness beneath?

  Part of me thinks Heinz is just looking to get in on the popularity of homemakers who want natural cleaning.  I’m not convinced that the 1% of extra acidity warrants the higher price tag and that maybe they’re just trying to cash in on a trend at our expense.


texts: What is the crystal structure of Calcium Acetate?

texts:
I tried conducting an experiment I saw at school with some materials I had at home. The experiment consisted of mixing a solution of Acetic Acid with Calcium Carbonate to yield Calcium Acetate: $$\ce{CaCO3 + CH3COOH -> Ca(CH3COOH)2 + CO3 + H2O}$$ I'm providing as much detailed in a summarized form to show what I did step-by-step if I did anything wrong. I didn't have any lab grade source of $\ce{CaCO3}$, but I found that chalk has a large concentration of $\ce{CaCO3}$, and I used that instead. I worked out a small calculator on Spreadsheets and found the appropriate quantities of each reactant. I then combined both of the ingredients and left the reaction to settle. After a couple days, I stirred and saw little to no fizzing, however, there was a lot of precipitate at the bottom of the beaker which I assumed to have been non-$\ce{CaCO3}$ residue from the chalk. I filtered the solution through a two coffee filters and let the solution evaporate. I should note that the solution was crystal clear after it was filtered. I came back a week later only to see a hard, styrofoam look-a-like on the sides of the beaker, and a layer of cloudy crystals at the base of the beaker. At the center of the base there's a crystal structure sprouting separately from the rest of the crystal layer.

I initially though perhaps my calculations or initial data gathered were incorrect but even after triple-checking them there was no error. Looking for possible structures of Calcium Acetate there was only one image that looked somewhat like the crystal sprouting at the center of the beaker, but still it doesn't explain what all the other substances are. Does Calcium Acetate have multiple crystal structures? Or has there been some sort of contamination from the chalk. Any help would really be appreciated:)


texts: Isopropanol in contact lens solution plastic bottle

texts:
I have a rather large plastic bottle of isopropanol ($99.7\%$), and I wanted to store some of it in a smaller, more handy container. I have two empty plastic bottles from contact lens solution that I wanted to use, but I'm not sure if it is safe for storing them in there for longer periods of time.

One of them has a 01 symbol inside a triangle, from which I concluded that this means PET and it also has a number 3 inside a circle (I'm not sure what that means).

The other one is HDPE (2 in a triangle) and has a number 5 elsewhere. Are both of those safe for long term storage of isopropanol?

I do intend to mark them very clearly.


texts: is dental acrylic dangerous when heated?

texts: I work in a research lab where we use small screws to attach onto hard objects and secure it with dental acrylic, to maintain durability. The screws are expensive, so when we are done with the particular project, we use a soldering iron to melt through the acrylic to get to the screws. I am concerned that when dental acrylic is heated, does it release toxins that can be harmful to my health?


texts: Can a first order reaction change to a second order reaction under specific temperatures?

texts:
I'm studying basic reaction behavior. My question is:

Consider a Continuous Stirred Tank Reactor (CSTR) where an exothermic, first-order, irreversible reaction takes place:

$$
\ce{A ->[k_1] B}
$$

Is there any possibility or (does it make sense in chemistry) that under high and/or low reaction temperature the reaction will switch to a second order reaction? i.e.

$$
\ce{A + A ->[k_2] C}
$$

If yes, can you give an example? Please consider answering in layman's terms.


texts: Does mercury amalgamate with Brass or Steel?

texts:
Does mercury amalgamate with Brass & Steel ?

Details: I am designing a micro pump to dispense mercury in micro quantities ($\mathrm{300-700}\ \pu{mg}$). I am planning to use 2 check valves with syringe to suck mercury from a mercury reservoir and push it for dispensing.
The problem is that all the high quality check valves are mostly Brass & I am not sure if mercury amalgamates with it.


texts: Why is polyethylene not called polymethylene?

texts: I understand that the monomer that polymerises to give polyethylene is an ethylene, but after polymerisation, the smallest repeating monomer in polyethylene seems to be a methyl and not an ethyl. So why don’t we call it polymethylene instead?


texts: How can the number of molecules and atoms be the same in a gas?

texts:
A sample of certain mass of gas was collected and it was found that the number of atoms and the number of molecules in the collected sample are equal. You are required to state the conclusion drawn from this observation.

I am not sure of the answer. I think it is related to the quantity of a mole being constant.


texts: Mechanism of retro aldol condensation of hydroxycyclopropylketone

texts: The reactants were treated with $\ce{NaOH} $. How the product here obtained. Can you show me the reaction mechanism for this. I found this is somewhat  Retro Aldol Condensation. But how?


texts: Understanding the gaff2.dat proper dihedral parameters

texts:
I have a project where I'm trying to program my own force field, and I decided to use the AMBER gaff2.dat force field parameters.
However, I am really struggling parsing the gaff2.dat file when it is about the dihedral angle parameters.
I am now trying to replicate the rotation around -O-C-C-O, for which I know the profile :
$$ V_{std} = 0.25 [1+ \cos 3\omega] + 0.15[1+\cos 2\omega]$$
I read that for gaff you have to take every parameters into account, so for $\ce{-O-CH_2-CH_2-O-}$ I have to use the parameters for O-C-C-O, H-C-C-O and H-C-C-H. In the gaff2.dat file I get :
os-c3-c3-os   1    0.000         0.000          -3          p28,suger5ring,suger6ring,coccoc GA AUE=1.1750 RMSE=1.6708 TorType=2
os-c3-c3-os   1    0.000       180.000          -2
os-c3-c3-os   1    0.170       180.000           1

hc-c3-c3-os   1    0.000         0.0            -3.         Junmei et al, 1999 TorType=1
hc-c3-c3-os   1    0.250         0.0             1.         Junmei et al, 1999 TorType=1

hc-c3-c3-hc   1    0.120         0.000           3          m1 SS AUE=0.2420 RMSE=0.2944 TorType=2

Which I guess would mean that :
$$ V_{gaff} = 0.170[1+\cos (\omega -\pi)] + 0.25[1+ \cos \omega] + 0.12[1+\cos 3\omega]$$
However, this gives this profile :

Which is not what I expected to get.
I have spent the past week reading a lot about the AMBER force field parameters and I ran out of ideas. So if anyone know how these dihedral angle are parametrized I could really use some explanation.


texts: Change in spin angular momentum during transition in one-electron atoms

texts:
I have a really basic qustion about spin and electronic transitions.

In one-electron systems (like H or $\ce{He+}$), will the electron change its spin during an electronic transition? Let's say the electron de-excites from 5p UP to 3s, will the spin be UP or DOWN in the 3s orbital?

From crystal-field theory I remember that a d-d transition where the electron had to switch to opposite spin was spin-forbidden (although it may still happen due to certain vibrational states). Is this still true for one-electron systems?


texts: Can one reduce solubility of NaCl by adding CO2 under pressure? Will the salt fall out of solution?

texts: One can salt CO2 out of solution by adding salt to carbonated water.  Can one do the reverse?  If one adds more and more CO2 to the water under pressure, can you drive out the salt?


texts: What chemical properties make LSD so psychoactive?

texts:
Lysergic acid diethylamide (LSD) is a well known hallucinogen and (usually) illegal psychoactive drug with the structure below:

The drug is active is doses measured in micrograms in contrast to many other active compounds where the dose is milligrams or even grams. The effective dose of Mescaline, a related psychoactive, is something like 200mg (more than 1,000 times more than for LSD).

Why is LSD so active in small doses? Do we know which features of the structure that contribute to its activity?


texts: Simple every-day-item hydrometer for distinguishing regular soda and diet sodas

texts:
When ordering a diet soda (no sugar soda) in a cafe or restaurant I would like to be sure I am  getting a diet soda and not a regular sugar-infested soda. Because a regular soda, is through all the sugar, far more dense than a diet soda, my idea is to use a simple hydrometer. Ideally this hydrometer would be a simple everyday item that sinks in diet soda but floats in regular soda. I already tested this this idea with some simple items such as coins or small toys. However all tested items either sink in both cases or float in both cases. Anybody has a good idea for a suitable item that sinks in diet soda but floats in regular soda ?

UPDATE although it didn't really answer my question, the experiment suggested by matt_black was too simple not to try out. However what happened when I performed the experiment was that both the can of regular coke and zero coke sank. I discovered there are a lot of video's on youtube showing a can of diet coke floating and only the can of regular coke sinking. So I am quite surprised by my own findings.


texts: When do I use a Grignard reagent such as PhMgBr, instead of an organolithium such as PhLi to react with butanone

texts: Essentially what I am asking is, how do I know whether I should use a Grignard in the place of an organolithium compound or vice versa when reacting it with aldehydes and ketones, or does it not matter as much for these carbonyl compounds?


texts: How would you find the mass in grams, if you only know the number of particles of a portion of the formula?

texts:
If you were given a question like below:

  What is the mass in grams of a sample of $\ce{Fe2(SO4)3}$ that
  contains $3.59 \times 10^{23}$ sulfate ions, $\ce{SO4^{2−}}$ ? The molar mass
  of $\ce{Fe2(SO4)3}$ is $399.91 \, \text{g}/\text{mol}$.

How would you go about solving a question like that?

I'm confused about how to use only the quantity of sulfate ions to find the mass in grams of the whole sample, given it's grams per mole.


texts: I really don't know if it is even logical to ask that $\ce{H3O-}$ doesn't exist but someone asked me and I wasn't clear. Hope that some one will make me clear.


texts: Steam distillation- how it actually works?

texts:
To obtain phenylamine after it is formed from the reduction of nitrobenzene with tin, we carried out steam distillation.

This is what I learned in class:

  "During the process,steam is injected into the flask (containing the reaction mixture) to create artificial vapour pressure on the surface of the liquid. When vapour pressure is equal to atmospheric pressure, the liquid starts to boil at 95 degrees"

This didn't make much sense to me. So I searched it up on the net and I  got another explanation (source):

  As the hot steam passes through the mixture it condenses, releasing heat. This will be enough to boil the mixture of water and phenylamine at 98°C provided the volume of the mixture isn't too great

Here, it is saying that the heat produced from the condensation of the steam will allow the mixture to boil. I am really confused, I mean I carried out steam distillation but how is it different from normal distillation and how is phenylamine collected at a lower temperature through this process?


texts:
What are the resonance structure of thioformate ion and  selenocyanat ion?
Give the structure of each resonance?
With formal charge?


texts: Which ceramic-like material is used in halogen MR16, GU5.3 and so on bulbs?

texts:
I hope this question belongs in here; I cannot think of any other better place to ask it.
Which kind of material is used in dichroic halogen bulbs to attach the bulb itself to the reflector and keep it in there? Looks to me like a ceramic or some kind of terracotta, but I wish to know the exact kind and if it is available for home use or, in case it isn't, a good recommendation as a domestic substitute. Of course, I understand it's main property is, appart from its hardness, the ability to be fireproof and/or refractory, due to the high temperatures being reached in there. For this same reason, something like epoxy resin or anything plastic based probably wouldn't work as it would melt or even burn.


texts: Is using melting/boiling point good to measure volatility?

texts:
I wanted to figure out a way to compare volatility in organic compounds, so I read on many forums on the differing ways to measure volatility, which included enthalpy of vaporization and melting/boiling points.

I am planning on using melting/boiling point to prove that branching of chains in organic compounds causes weaker volatility.


texts: Can Hartree-Fock mix more orbitals than there are electrons?

texts:
I'm trying to understand Hartree-Fock well enough to write my own implementation. A point that I seem to be coming to that I'm not sure is correct: the method only produces one-electron orbitals that are linear combinations of the starting orbitals?

That is, if I have $n$ electrons, I start them off in some $n$ orbitals (say, atomic orbitals). Is it correct that the final result will only mix those $n$?

It seems very natural that I might want to include other orbital shapes -- maybe I want the first $m \gg n$ atomic orbitals in my molecule, and let all of those contribute to building lower-energy one-electron orbitals. As best s I understand it, standard HF does not allow for this, because at each step of diagonalizing the Fock matrix it's just using combinations of the existing orbitals -- with no room for the excited states.

Is my understanding correct? Are there other extensions of HF which allow broader mixings?

One possibility that I could imagine would be starting off with $m$ electrons, so that I have $m$ orbitals available. Then I run HF, and at the end I only use the $n$ lowest orbitals. This runs into the problem that I will still be computing Coloumb terms from the $(m-n)$ extra "fake" electrons, which will disturb the shape of my $n$ lowest orbitals. So perhaps the correct approach would be to use $m$ electrons mixing, but when I compute the Fock matrix $F$, I only include $J$ and $K$ terms from the $n$ lowest modes (but letting these affect the energies of all $n$ modes). But that seems messy, because now $F$ isn't symmetric... in the end this seems like a risky path to go down.

Help appreciated, thank you.


texts: Mechanism of ring opening of amine combined with formylation

texts: What is the mechanism for this reaction? The tertiary amine is converted into an amide and the ring gains a double bond. I can't figure out how the C-O double bond would be formed.


texts: Looking for a non-toxic, environmentally safe highly colored or intense dye

texts:
I need a dye that is "highly colored" or intense.  I want to put it in water and flow the water in the form of a liquid sheet that is around 100 microns thick.  A number of spray nozzles use this principle to produce droplets.  The liquid is first formed into a sheet that breaks down after a few milliseconds into droplets.
The issue is that at such thin thicknesses, colors often disappear even if they look very intense in a tank.  I'll be working with around 0.2 gallon per minute to 0.5 gallon per minute flowrates, so something that hopefully can be added in relatively small quantities.  But more important is that the dye is non-toxic and environmentally safe.
Thanks for any suggestions.


texts: Rule of thumb of how much vacuum does lab glass stand?

texts:
Sometimes I have to apply vacuum to all kind of different borosilicate glass equipment like:

round bottom flasks
liebig condensers
fractional distillation apparatus
spiral condensers
chromatography column
and so on...

While I know that a thick walled round bottom flask will pretty much stand any vacuum my vacuum pump can produce, I am not so sure for something as fragile as a spiral condenser.

Is there a kind of rule of thumb how much mBar thin walled glass equipment like spiral condensers or chromatography columns can stand without risk of implosion?


texts: Why wouldn't you consider the [H+] produce from the weaker acid in a mixture of two acid?

texts:
Calculate the pH of a solution that contains $\pu{2.0 M}$ $\ce{HF}$ and $\pu{2.0 M}$ $\ce{C6H5OH}$. Also calculate the concentration of $\ce{C6H5O-}$ in this solution at equilibrium.

In these situation, you are told to first find which is the strongest acid. $\ce{HF}$ is.

Knowing this, you can use the ICE table and the $K_a$ of $\ce{HF}$ ($7.2 \times 10^{-4}$) to find $[\ce{H+}]$ in the dissociation of $\ce{HF}$. This $[\ce{H+}]$ is then use to find the $\mathrm{pH}$ of the mixture, but my question is why wouldn't we add the $[\ce{H+}]$ produced from the dissociation of $\ce{C6H5OH}$? Also the $[\ce{H+}]$ that could be made from $\ce{H2O}$ reacting with itself? Is it because the $[\ce{H+}]$ from $\ce{C6H5OH}$ (weaker acid) and $\ce{H2O}$ is so low that it won't really affect the $\ce{pH}$ number?

This question pours over to when you calculate $[\ce{C6H5O-}]$. Why would we just substitute the $[\ce{H+}]$ we found from $\ce{HF}$ for the $[\ce{H+}]$ in the $K_a$ formula of the dissociation of $\ce{C6H5OH}$:

$$K_a = \frac{[\ce{H+}][\ce{C6H5O-}]}{2.0 - x}?$$

Is it because at equilibrium of the mixture we know $[\ce{H+}]$ must be close to the $[\ce{H+}]$ that would be produce at the equilibrium of a $\ce{HF}$ reaction? So it will somehow affect which way the $\ce{C6H5OH}$ reaction will go (Le Chatelier's principle). So because of the addition of HF $[\ce{H+}]$, the reaction will go left and less $\ce{C6H5O-}$ should be made compare if it was just a solution of $\ce{C6H5OH}$?


texts: Major product of this Hoffman elimination?

texts:
1-methyl-1-quarternary ammonium cation(with methyl groups) cyclohexane is heated with hydroxyl ion. I want to find the major product.

In the solution, it is given that a hydrogen attached to the methyl group is eliminated.

However,
 1. the methyl group and the cation are not placed in an anti-periplanar configuration, so there would be considerable amount of energy needed (just a guess) to distort the ring;
 2. the hydrogen atom attached to the beta carbon on the ring is equally acidic;
 3. The transition state for OH eliminating the hydrogen attached to the beta carbon is not crowded. I don't think sterics play a role here.

So I feel like the hydrogen attached to the beta carbon should be eliminated.
Why am I wrong?


texts:
Terylene is a polyester made from terephthallic acid and ethylene glycol. Even though we use two reagents, they undergo esterification to give bis(2-hydroxyethyl) terephthalate (monomer) which then undergo polymerization.

So, is it correct to consider terylene as a copolymer? My reasoning tells that it should be a homopolymer. Same line of reasoning gives nylon, phenol-formaldehyde resin, bakelite — all as homopolymer.

But majority of questions which I go through considered the above polymers as copolymers. What is correct? Are they homopolymers or copolymers?


texts: What is a rigorous definition of gas volume, and how is the Van der Waals equation derived?

texts:
I am confused about the justification for the corrections to the ideal gas law in the Van der Waals equation: $$p=\frac{nRT}{V-nb}-a\left(\frac{n}{V}\right)^2$$

I understand that the equation attempts to correct for attractive and repulsive forces between molecules, and that at high volumes the corrections are negligible, at intermediate volumes the $V-nb$ correction dominates (since attractions are dominant and this shrinks the volume, as should occur for attractions), and at low volumes the $a(n/V)^2$ correction dominates, since repulsions are dominant.  However, the 7th edition of Atkins' and de Paula's Physical Chemistry justifies part of this equation as follows:

  The repulsive interactions are taken into account by supposing that they cause the molecules to behave as small but impenetrable spheres.  The nonzero volume of the molecules implies that instead of moving in a volume $V$ they are restricted to a smaller volume $V-nb$.  This argument suggests that the perfect gas law $p=nRT/V$ should be replaced by $$p=\frac{nRT}{V-nb}$$ when repulsions are significant.

I am confused by this argument-- what exactly is the definition of 'volume' here?  They seem to be saying that it is the empty space around the gas molecules, but it seems to me that volume should be defined as the space 'taken up' by the gas.  Why should the space taken up by the particles themselves be subtracted?  This isn't done for solids or liquids as far as I know.

These thoughts have also made me realize that I'm not quite sure what it means for a gas to 'take up' space.  Does anyone have a rigorous definition of gas volume?

EDIT: The exchange with Chris in comments has raised further questions.  It now seems to me that the $V-nb$ correction actually accounts for repulsions rather than attractions.  I think I was incorrect in thinking that the $V-nb$ correction dominated at intermediate volumes and $a(n/V)^2$ at low volumes.  If $V-nb$ is for repulsions, then it should dominate at low volumes, but I can't tell from the equation which correction will actually be dominant.  Also I am now wondering whether it even makes sense to connect one correction with repulsions and one with attractions.

EDIT: Follow-up questions for F'x:
- I thought that 'density' meant mass/volume.  Is the use of it to represent the inverse of molar volume (as you have used it) common?
- Where is the phase-transition in the red van der Waals curve?
- I am still a little unclear on gas volume.  Are the 'volume available to the gas' and 'volume of the gas' the same?  You say it's the same as the shape of the container, but aren't we subtracting the volume of the actual gas particles from that?  The $V$ term represents the volume of the gas, correct?  And $V-nb$ represents the 'volume available to the gas'.


texts:
"the most remarkable success of the Bohr's theory is that it provides a satisfactory explanation for the line spectrum of hydrogen."

But what is the problem with line spectrum of hydrogen which could not explained before the Bohr's theory was introduced and how it was explained by Bohr's theory?


texts: Which of these compounds does not liberate heat when water is added to it?

texts:
Which of these compounds does not liberate heat when water is added to it: $\ce{KNO_3}$, $\ce{NaOH}$, $\ce{CaO}$, $\ce{H_2SO_4}$, $\ce{Na}$.

I know from experience that dropping sodium tablets into water has explosive results, but I am clueless about the method to solve this problem. I know the answer is $\ce{KNO_3}$, but I don't know why. If someone can provide the method, I think I can do the problem.


texts: Effect of Zn dust reduction of phenolic -OH group on other groups

texts:
We use distillation with zinc dust to remove -OH group from phenol.
$$\ce{Ph-OH + Zn \rightarrow Ph-H + ZnO }$$

What I want to know is that whether this reaction has any effect on other groups attached to the benzene ring, like $\ce{-CH_3,-NH_2,-NO_2, -CN, -CONH2}$ etc. or not?


texts: What compounds do Nor1 and Nor2 citalopram refer to?

texts: In Goodman and Gilman's The Pharmacological Basis of Therapeutics 12th Edition pg. 406, two drugs, nor1-citalopram and nor2-citalopram are referred to but I have no idea what they are. Could somebody tell me a more commonly used name of these drugs or their IUPAC names if common names do not exist. Also please show me what exactly the nor1 and nor2 refers to. I'm guessing there's methyl groups missing in them at different positions because I know that norpethidine (or normeperidine) refers to the N-demethylated metabolite of pethidine (or meperidine).


texts: Difference between the terms “analyte” and “analyate” and their applicability

texts:
“Analyte” is the term that is usually universally understood and is listed in  IUPAC Gold Book:

  analyte The component of a system to be analysed.

However, recently I stumbled upon the word “analyate”.
Initially I thought of it being a typo or an erroneous translation (I'm not a native English speaker), but upon inspection of the literature sources it turned out be used in cited publications in the context similar to the term “analyte” (emphasis mine):

McMaster's LC/MS: a practical user's guide (323 citations) [1, pp. 2, 16]:

  The mass analyzer is quickly overwhelmed by the signal from the solvent if the HPLC output is introduced directly into the mass spectrometer. The analyate signal is buried beneath this solvent signal avalanche. […] The HPLC solvent gradient used to resolve closely eluting HPLC peaks and decrease HPLC run times also produces solvent composition changes that further complicate the solvent-masking effect of analyate signal.

  […]

  The purpose of an interface is twofold. It must remove as much solvent as possible without losing the analyate, and it must volatilize and ionize its components for submission to the analyzer.

At the same time in the textbook the term “analyte” is utilized on p. 61:

  The ionized analyte ions formed in the interface between the HPLC and
  the mass spectrometer cannot survive collision with air molecules in the analyzer.

… and on p. 151:

  Gas chromatography. A separation technique in which the volatile analyte is swept by a carrier gas down a column packed with packing coated with an absorbing liquid.

Zhao and Swager (272 citations) [2, p. 9379]:

  It is informative to investigate the fluorescence quenching activities of P1-3 in solution. Conducting these studies in chloroform, a good solvent, allows us to evaluate the responses of individual polymer chains and the relative
  analyate affinities to the polymers under these conditions.

Patent US20050137471A1 (182 citations) [3]:

  The Signals are processed in a processing unit to calculate the concentration
  of the analyate.

DeLouise et al. (146 citations) [4, p. 3224]:

  It also simplifies quantitation of the optical response relative to competitive techniques based on evanescent waves where the signal response decays exponentially from the surface causing sensitivity to depend on the surface-analyate distance.

Hart et al. (130 citations) [5, p. 461]:

  It was found that as structural similarity between the imprint molecule and the analyate molecule diminishes, both retention and selectivity decrease.

  […]

  Making a relatively small perturbation to the analyate by removing the aromatic hydroxyl group results in a lower, but still significant, separation factor of $α = 2.5.$

… and many more other less cited papers, over 250 in total over 1887–2019 time span according to Google Scholar (I used Harzing's PoP software for query).
So, is there a difference between the terms “analyte” and “analyate”?
If they are not fully interchangeable, then what exactly “analyate” is, or in what context its usage is more appropriate?

References:

McMaster, M. C. LC/MS: A Practical User’s Guide; John Wiley: Hoboken, N.J, 2005. ISBN 978-0-471-65531-2.
Zhao, D.; Swager, T. M. Sensory Responses in Solution vs Solid State:  A Fluorescence Quenching Study of Poly(Iptycenebutadiynylene)s. Macromolecules 2005, 38 (22), 9377–9384. https://doi.org/10.1021/ma051584y.
Haar, H.-P.; List, H.; Baader, F.; Harttig, H.; Meacham, G. Continuous Glucose Monitoring Device. US20050137471A1, June 23, 2005. (PDF)
DeLouise, L. A.; Kou, P. M.; Miller, B. L. Cross-Correlation of Optical Microcavity Biosensor Response with Immobilized Enzyme Activity. Insights into Biosensor Sensitivity. Anal. Chem. 2005, 77 (10), 3222–3230. https://doi.org/10.1021/ac048144+.
Hart, B. R.; Rush, D. J.; Shea, K. J. Discrimination between Enantiomers of Structurally Related Molecules:  Separation of Benzodiazepines by Molecularly Imprinted Polymers. J. Am. Chem. Soc. 2000, 122 (3), 460–465. https://doi.org/10.1021/ja9926313.


texts: Why does a complete discharge destroy a Li-Ion-Battery?

texts:
I read that completely discharging a Lithium Ion Battery is a very bad idea because it will lose plenty of capacity. But why?

I know that the reaction (fot the LiFePO4 battery) is:
$$ \ce{LiFePO4 + C6 <=>[1 e-] FePO4 + LiC6 } $$

So at a complete discharge, we only have our electrodes made of $\ce{LiFePO4}$ and $\ce{C6}$. Why shouldn't this react to the products of the reactions above?

When overcharging the battery I could find a solution, why it destroys the latter. Maybe all the graphite is ionized and so, the electrode is in solution. This would be a very big problem, but the graphite will only ionize if it can react with a cation (like lithium), so a small excess of graphite should prevent this.

What about other Li-Ion-Batteries?

This is what I read on the internet:

  The discharge voltage is around 2.5 V depending on the cell type; It
  must not fall below, otherwise, the cell will be destroyed by
  irreversible chemical reactions. However, many electronic devices
  already switch off at significantly higher voltages, eg 3.0 V.

What do they mean with the irreversible chemical reactions? Which ones?


texts: Does baked bread have the same amount of calories as its ingredients?

texts:
I bake a loaf of bread containing:

500 g strong flour (1700 kcal)
40 g butter (300 kcal)
24 g yeast (80 kcal)

For a total of 2080 kcal.

How many calories does my finished loaf contain?

My assumption is that at most, some of the energy in the yeast will be used during the proving process but I realised I know very little about the actual processes that take place during proving and baking.


texts: What does an electron's spin of 0.5 and minus 0.5 signify?

texts:
While teaching me magnetism, my teacher told me about the spin of an electron. He told me that the spin of .5 means that if we rotate the electron twice counter-clockwise on its axis, we would have the same face(picture) of the electron. And if we rotate an electron of -0.5 spin twice in the opposite direction, we would have the same face. But if rotate it only once(360⁰), we would not get the same face/picture of an electron.
How can this be possible? Or am I just making a mistake somewhere? A simple explanation would be greatly appreciated for I am only a tenth grader.


texts: Does an electron's spin change when being excited?

texts:
My preconception is that when you fill an empty orbital by exciting an electron (with a photon), the empty orbital should be filled by an electron with the same spin. However, I've seen examples of that happening and not happening. For example, on this University of Calgary
web page there is an image of the electron spin being flipped:

The lowest energy transition is that between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the ground state.  The absorption of the EM radiation excites an electron to the LUMO and creates an excited state. The more highly conjugated the system, the smaller the HOMO-LUMO gap, DE, and therefore the lower the frequency and longer the wavelength.

Does it just not matter that much energetically?


texts: Why is crystalline aspirin washed with chilled water in the purification process?

texts:
Take as example this
or even better this:

  Wash the crystals with 2-3 ml of chilled water.

Why does the aspirin need to be cooled down? And why do we wash the aspirin with chilled water?


texts: What causes the stairstep structure in bismuth crystals?

texts:
I've been interested in bismuth crystallization since I found out they existed, but have a question on their formation.

According to Wikipedia, the stair-step structure of bismuth crystals is "the result of a higher growth rate around the outside edges than on the inside edges."

What would cause this higher growth rate around the edges? Cooling?


texts: Gaussian09 and Path Integral Monte Carlo which one predicts the total internal energy more accurately?

texts:
I'm learning PIMC with primitive action and currently just testing the code with single methane molecule, I did run a Gaussian ccsd(t) calculation, I notice that at 298.15K & 1atm, the energy predicted by PIMC(0.0476a.u.) is slightly lower than the one by Gaussian(0.0477a.u.) both errors start from 5th decimal number. I'm just wondering which result could be more reliable? And why one is more reliable than the other?
It might be a dumb question, but I don't see anywhere made such comparison and I'm just an undergraduate student with no experience with either of two computational techniques. Would be greatly appreciated if can use some expertise!


texts: Choosing Parent Chain, Complexity of Side Chains

texts:
Which parent chain should we choose for this structure? is it A or B?

I followed the rule A-2.6, but it still got me confused.
Both alternative A and B has the same number of side chains (2 side chains) - rule A-2.6(a).
Both alternative A and B has the same number of locants, which are 5 and 6 - A-2.6(b).
Both alternative A and B has the same number of carbon in each locants, which are 4 atoms on number 5 and 9 atoms on number 6 - A-2.6(c).
Both alternative A and B branched side chains are quite similar, how do we decide? - A-2.6(d)


texts: How many crystal forms of HCl have been identified - where to find the unit cells/lattice constants?

texts:
This blog about stomach acid shows this image of the "zig-zag" form of crystalline HCl (see also Wikipedia where it looks (to me) like five four HCl's per unit cell), but links to this cubic crystal structure (2nd image) data card instead with only one HCl/cell.

I've read crystallographic "data cards" in a past life, but I have no idea how to search for all the forms of HCl on-line (and non-paywalled) now, in order to get the lattice constants, angles, unit cells etc. to build a 3D model of each form of crystalline HCl in Blender for example.

note: I am really looking for just the dimensions and shape of the unit cell, and coordinates of the atoms within the unit cell as a name and numbers, as one would find on a crystallographic data card. I can do all the plotting - no need for plotting software.

below: Here's the Wikipedia image mentioned above, from here. It certainly looks like the Chlorines are at 0.25 and 0.75 along the a-axis (vertically) and 0.00 and 0.50 along the b- and c-axes, so there seems to be enough information here to work out or infer the complete 3D structure, assuming it's cubic, and further infer that a=b=c=521pm, which suggests a density of this solid of about 1.7 g/cm^3. But remember, when you infer, you make an inf out of e and r.


texts: Is nitrogen of aniline sp² or sp³ hybridized?

texts:
I found a thread which discussed this which totally confused me. (refer to the part of the link which talks about $\ce{sp^2/sp^3}$)
The question "How to rationalise the resonance structures and hybridisation of the nitrogen in a conjugated amine?" is helpful, but doesn't have aniline specifically. I understand that if the lone pair is in resonance, it becomes $\ce{sp^2}$.
Can someone help me out?


texts: What are the metamers of penta-1,2-diene?

texts: First of all, are there any metamers for dienes? If there are any, how can I find them?


texts: How to calculate the solubility of lead (II) carbonate in water, given that bicarbonate will also form?

texts:
Calculate the solubility of lead (II) carbonate, $\ce{PbCO3}$, ($K_{\mathrm{sp}} = 1.5 \times 10^{-15}$) in water, given that carbonate is a stronger base than water, so will also form bicarbonate. When bicarbonate acts as an acid: \begin{align}
\ce{HCO3- &<--> H+ + CO3^2-} & K_{\mathrm{a}} &= 4.7 \times 10^{-11}.
\end{align}

I think the equation is, in light of airhuff's suggestion, $$\ce{PbCO3 -> Pb^2+ + CO3^2-}.$$
What I'm most confused about is how the bicarbonate and $K_\mathrm{a}$ comes into play in this question. It makes a traditional $K_\mathrm{sp}$ question a little trickier.

Possible answer?:
\begin{align}
\ce{PbCO3 &<--> Pb^2+ + CO3^2-}
&\implies K_1 &= K_\mathrm{sp} = 1.5\times10^{-15}\\
\ce{CO3^2- + H2O &<--> HCO3- + OH-} &\implies K_2\\
\ce{PbCO3 + H2O &<--> Pb^2+ + HCO3- + OH-} &\implies K_3\\
\ce{HCO3- &<--> H+ + CO3^2-} &\implies K_4 &= K_\mathrm{a} = 4.7\times10^{-11}\\[3ex]
K_3 &= K_1 \cdot K_2\\
K_3 &= \frac{K_\mathrm{w}}{K_4}\\
K_2 &= \frac{1\times10^{-14}}{4.7\times10^{-11}}\\ &= 2.1\times10^{-9}\\
K_3 &= (1.5\times10^{-15})\cdot(2.1\times10^{-4})\\ &= 3.15\times10^{-19}\\
S_{\ce{PbCO3}} &= [\ce{Pb^2+}][\ce{HCO3-}]\\ &=[\ce{OH-}]\\
K_3 &= [\ce{Pb^2+}][\ce{HCO3-}][\ce{OH-}]\\ &= S^3\\
S &= \sqrt[3]{K_3} (3.15\times10^{-19})\\
  &= 6.8\times10^{-7}~\mathrm{M}\\
\end{align}

Does the way I solved it look okay?


texts: Is there an important difference between soap and detergent?

texts:
I've read recently somewhere that most "soaps" are actually detergents and the real soap would not be a good idea in everyday applications like washing hands, shower gels and shampoos, and dish washing liquids. But I couldn't find a sufficiently detailed explanation about the differences of the two, just that the detergents are often marketed as soap.

Are they really different? What negative effects does soap have that detergent doesn't? Is there something soap does that detergent doesn't do?


texts: Can I use sodium hydroxide (NaOH) to remove oxides from metals?

texts:
Sodium hydroxide dissolved in water is a very strong base. I think this could mean it could de-oxidate the metal oxides during re-ox reaction. Basically, I ask whether the following happens:
$$\ce{NaOH + Fe2O3 -> Fe + something}$$

I have read that it does reduce carbon dioxide producing sodium carbonate and water:

$$\ce{2 NaOH + CO2 -> Na2CO3 + H2O}$$

Would that work with metals? If yes, which ones?


texts: Basic thermodynamics question about work

texts:
I am getting into thermodynamics, and I have a basic fundamental question about the definition of the change in internal energy $\mathrm{d}U$:

$\mathrm{d}U = T\,\mathrm{d}S - P\,\mathrm{d}V + \sum\mu_i\,\mathrm{d}n_i$

Firstly, I do not understand why it's not the case that $\mathrm{d}W$ is defined as $P\,\mathrm{d}V + V\,\mathrm{d}P$, but only as $P\,\mathrm{d}V$. I can imagine a situation where the volume is fixed, but number of particles increases, thus increasing the pressure. I would think that this increase in pressure would also increase the internal energy.

Secondly, in the same manner I also don't understand why $\mathrm{d}Q$ is defined as $T\,\mathrm{d}S$ and not as $T\,\mathrm{d}S + S\,\mathrm{d}T$. I would think that a change in temperature would surely change the internal energy.


texts: Bicycle tube inflation with 16g CO2 cartridge

texts:
How much pressure will a 16 gram cartridge of $\ce{CO2}$ (carbon dioxide) provide in a bicycle tire? Remembering my high school chemistry (forty years ago) and googling, I came up with this answer:

Figure the volume of the tube (a torus): area of a cross section times the circumference, for a $30\:\mathrm{mm}$ tube on a $70\:\mathrm{cm}$ wheel, I got $1,554\:\mathrm{cm^3}$, or $1.554\:\mathrm{L}$. One mole is $24.47\:\mathrm{L}$. $1.554 / 24.47 = .06353$. One mole of $\ce{CO2}$ is $44\:\mathrm{g}$ (using atomic weights of carbon, 12, and oxygen, 16). $.06353 \cdot 44 = 2.795\:\mathrm{g}$. So the volume of the tube at one atmosphere is $2.795\:\mathrm{g}$ of $\ce{CO2}$. $16 / 2.795 = 5.7\:\mathrm{atm}$. One atmosphere is $14.7\:\mathrm{psi}$. $5.7 \cdot 14.7\:\mathrm{psi} = 84\:\mathrm{psi}$.

Is this correct?


texts: Boiling chips for concentrating sulfuric acid

texts: I am concentrating sulphuric acid. What should I use as boiling chips? I have tried broken mug pieces, the solution became cloudy, and I have tried broken glass (retrieved from a drinking class, not crystal) and the solution became yellow.


texts:
Silicon has been known to form analogues of organic compounds. For example, silicon with 4 hydrogen atoms forms silane as opposed to methane. This continues up the alkane list, with disilane for ethane, and so forth.

Silanes also have with hydroxyl groups to form "silanol." Thus, disilanol is the silicon analogue of ethanol. ($\ce{H3Si-SiH2OH}$)

How toxic is disilanol?


texts: Is the freezing point of solution always lower?

texts: If the freezing point of a solution always lower than that of the pure solvent or is it possible for it to end up being higher?


texts: Is “double dot” (“··”) notation used for a double radical?

texts:
I wondered if this was a typo in the notes given to me. I haven’t come across notation like this before:

Branching — steps in which number of radicals increases (can lead
to explosion)
$$\ce{H^. + O2 -> OH^. + O^{..}}$$


texts: Differences in specific free radical reactions enthalpies

texts:
Iodination of alkanes using iodine $(\ce{I2})$ is usually an unfavorable reaction. Tetraiodomethane $(\ce{CI4})$ can be used as the iodine source for iodination, in the presence of a free-radical initiator such as hydrogen peroxide. Propose a mechanism (involving mildly exothermic propagation steps) for the following proposed reaction. Calculate the value of $\Delta H$ for each of the steps in your proposed mechanism ($\ce{cp = cyclopentyl}$).
  $$\ce{cp-H + CI4 ->[H2O2, heat] cp-I + HCI3}$$

  The following bond dissociation enthalpies may be helpful:
  \begin{array}{lr}\hline
\text{bond} & \Delta H / \pu{kJ mol-1}\\\hline
\ce{I3C-I}  &  188 \\
\ce{HO-OH}  &  213 \\
\ce{HO-I}   &  234 \\
\ce{cp-H}   &  397 \\
\ce{I3C-H}  &  418 \\
\ce{cp-I}   &  222 \\\hline
\end{array}

From the book: L. G. Wade Organic Chemistry; 8th edition; Pearson: 2013; exercise 4-57.

The correct answer is given as:
\begin{align}
\text{Initiation:}\\\hline
\ce{HOOH &-> 2HO*}& \Delta H &= \pu{+213 kJ/mol}\\
\ce{HO* + I-CI3 &-> IOH + CI3}& \Delta H &= \pu{-46 kJ/mol}\\[2ex]\hline
\text{Propagation:}\\\hline
\ce{cp-H + *CI3 &-> cp* + H-CI3}& \Delta H &= \pu{-21 kJ/mol}\\
\ce{cp* + I-CI3 &-> cp-I + *CI3}& \Delta H &= \pu{-34 kJ/mol}\\\hline
\end{align}

The overall enthalpy is $\Delta H = \pu{-55 kJ/mol}$ for the propagation steps.

In the book, there is also an overall table of bond dissociation enthalpies.
One important one I used here is the one of water, $\pu{498 kJ mol-1}$.

I have a significantly more exothermic process here:
\begin{align}
\text{Initiation:}\\\hline
\ce{HOOH &-> 2HO*}& \Delta H &= \pu{+213 kJ/mol}\\
\ce{cp-H + OH* &-> cp* + H2O} & \Delta H &= \pu{-101 kJ/mol}\\[2ex]\hline
\text{Propagation:}\\\hline
\ce{cp* + I3C-I &-> cp-I + I3C*}& \Delta H &= \pu{-135 kJ/mol}\\
\ce{I3C* + cp-H &-> cp* + I3C-H}& \Delta H &= \pu{-21 kJ/mol}\\\hline
\end{align}

Here the initiation is less endothermic, and the propagation is significantly more exothermic. So why is this not given as the correct answer? Am I missing something here? I'm quite new at organic chemistry, so I think I must be wrong, not the textbook.


texts: Low or high enthalpy of combustion in relation to stability

texts:
I know that this is a very basic question, but I am new to chemistry and I cannot figure it out on my own:

A combustion is always exothermic, so ΔH is negative. It says in my textbook that more stable molecules have a lower heat of combustion (I am assuming here that this is basically identical to stating that it has a lower enthalpy of combustion).

What I do not understand is the following: more stable molecules have a lower enthalpy of formation than less stable molecules. When undergoing combustion, stable molecules should be expelling less heat than less stable ones. So shouldn't the enthalpy of combustion of more stable molecules be higher (i.e. less negative)?

N.B. The question is related to the following:
I was asked to determine which of the following two compounds has a lower enthalpy of combustion. I understand that B is more stable than A, but I am not able to translate that to "a lower enthalpy of combustion" because of my lack of understanding of the above…

Many thanks!


texts: Why do polar aprotic solvents favour SN2 over E2?

texts:
I was reading about Substitution and Elimination Reactions and I came across the following on MasterOrganicChemistry:

  Polar protic solvents tend to favor elimination (E2) over substitution (SN2). Polar aprotic solvents tend to favor substitution (SN2) relative to elimination (E2).

I understand the first part. But I have trouble understanding the part with the polar aprotic solvents.

Consider the following example (from the same website):

Why is E2 not favoured? I can understand why polar aprotic solvents favour SN2:

  A polar aprotic solvent like acetone or dimethylformamide preferentially solvates cations, leaving an almost "bare" nucleophile. This increases its nucleophilicity

But I could find no explanation as to why E2 does not happen because of the solvent. What keeps the nucleophile (cyanide anion here) from abstracting a beta hydrogen?


texts: How to determine the empirical formula given mass percentages of the elements and the molecular weight?

texts:
A compound has $67.3 \% \rm~C,4.62 \%~N,6.93 \%~ H$ and O. Determine the molecular formula of the compound knowing its molar mass is $283\rm~\frac{g}{mol}$.

My solution : The percentage for the oxygen is $$100-( 67.3+4.62+6.93)=21.15$$ percent oxygen. Lets determine the number of moles for every substance.

For the carbon we have $$n_C = \frac{67.3 \rm~g}{12\rm~\frac{g}{mol}} =5.6~\rm mol$$

We do the same for N, H and O. We have 0.33 atoms of N,6.93 atoms of H and 1.32 atoms of O.

So the ratio is $5.6 : 0.33 : 6.93 : 1.32$.

We divide by $0.33$ and we have $17 : 1 : 21 : 4$. The empirical formula is $\ce{C17H21NO4}$.

Its molar mass is 303 g/mol. Now we find the quotient:

$$K= \frac{\text{Molar mass of the real formula}}{\text{Molar mass of the empirical formula}} =\frac{283}{303}\approx 1$$

So the molecular formula is $\ce{C17H21NO4}$. Is this correct?


texts:
I'm having trouble understanding how exactly coordination complexes are formed.

Compounds such as $\ce{[Cu(H2O)6]++}$ are the ligands filled into the empty 3 of 4p orbitals+ 1 of 5s orbital + 2 of 4d orbitals or how?


texts: Why is 2H2O2 -> 2H2O + O2 a first order reaction?

texts:
My book says that the reaction $\ce{2H_2O_2 -> 2H_2O + O_2}$ is a first order reaction and that it's rate equation is $\ce{k[H_2O_2][I^{-}]}$.

However i don't see why that would be first order? Isn't the order of the reaction supposed to be the sum of powers of the concentration of the reactants?


texts: Why is bond angle of H2O greater than that of PH3?

texts: Central atom of water has two lone pairs and that of phosphine has one lone pair, then why isn't bond angle of water smaller?


texts: Can you calculate the properties of a substance based solely on its atomic properties?

texts:
I'm trying to write some software that I can use to determine, roughly, what the physical properties of a pure substance are. I know I could just use a database of the known properties of each element, but that doesn't do much for me when I go to create molecules and combine substances. A database that lists how each element will react to another is likely impossible, so I got to thinking... there has to be a mathematical way of determining these properties!

For example, I understand that there are trends on the periodic table that show that the stronger the force between the molecules is, the higher the melting point will be. I also understand that we can calculate how strong that force is based on what we know about the atom. So why can't I find any information relating the two in some mathematical way? The same goes for color, hardness, malleability, etc. Do we really only know these values through testing? We know the values but we don't know why they are what they are?

I know this is deeply complex topic and may not even be computational possible. In those cases, I'm trying to do as much as I can to approximate.


texts: Creation of ester from acetylene derivative

texts:
I took a much different approach from the solutions manual. My synthesis:

1) H2 and Lindlar's catalyst to stop at the alkene.

2) Oxidative cleavage to form benzoic acid. Works here because we have a benzylic hydrogen.

3) Addition of excess allyl alcohol with catalytic concentration of acid and heat. A Fischer esterification step.

This is also one fewer step than what my solution's manual has. The solutions manual went up to the acid chloride and down to the ester, which is a nice step (avoids the heat). Does mine also work on paper?


texts: PLP-Dependent Cyclization and Decarboxylation

texts: I am looking at Compound A (see below) and am trying to figure out a decarboxylation mechanism that results in Compound B (see below). I have come up with an internal mechanism that might work that I have attached to this question. However, I am trying to connect it to enzyme catalysis, and I am thinking that a PLP-dependent enzyme is involved I just cannot quite figure out the mechanism.


texts: How does volume contraction in solvent mixing work?

texts:
I recall seeing chemistry demonstrations where a significant amount of a solute is dissolved in a solvent and the solution volume barely changes. Questions regarding this:

1) How is this possible?

2) What solvent/solute combinations best demonstrate this effect?

3) Is it possible to wind up with less solution, in other words Is it possible to have Volume(solution) < Volume(solvent) + Volume(solute) ?


texts: What's the chemical equation for the lithium iron phosphate battery

texts:
The title says it all, I'm searching for the chemical equation to the lithium iron phosphate battery.

I know that the cathode is made of $\ce{LiFePO4}$ and that upon discharging, it is transformed to $\ce{FePO4}$. The Anode is made of graphite.

So I think that the reaction on the anode is:
$\ce{LiFePO4 -> FePO4 + Li+ + e-}$

Is this correct? If so, what's happening on the anode?


texts: Does the reaction of sulfur and potassium nitrate involve production of sulfur trioxide?

texts:
I've heard that oxidising sulfur with potassium nitrate yields $\ce{SO3}$ gas, but can't find a definitive answer anywhere.

Is sulfur trioxide produced? More generally, what's the full reaction?


texts: Michaelis menten constant motivation behind 1/2?

texts:
So the michaelis constant is defined as the substrate concentration at half maximal „reaction-speed“.
I was wondering why 1/2 ?
I guess for higher values you need more substrate, which could be a problem. But would 1/3 also work ? Or does 1/2 optimize some other parameter?


texts:
I don't understand how a salt bridge work exactly: what happens inside it and how it affect the cell's lifetime.
I have already read:
Salt Bridges/Porous Disks
Salinic bridges in voltaic cells
Difficulties understanding how salt bridge works
What I understand:
The salt bridge's goal is to maintain electro-neutrality in each of the half-cells so that the voltaic cell keeps working and it helps avoiding the mixing of the half-cells' ions in solutions.
When the salt bridge is being used in the cell, its ions (anions and cations which constitute the salt bridge's electrolyte) are moving towards the half-cell that attracts them.
What I don't understand:

Do the salt bridge's ions leave the salt bridge to go all the way within the hall-cells' solutions or do they stay at the border ? Is it the case in all bridges ?
Do the half-cells' ions move inside the salt bridge or do they stay in the salt bridge at the border solution/salt-bridge ? Is it the case in all bridges ? And is it in the same proportions as the salt bridge's ions ?
How do the ions move exactly in the salt-bridge ? It seems like the propagation in, let's say agar-agar, is much slower than the displacement of ions in the liquid solutions in the half-cells, is it not a problem for the whole cell ? Is it like a longitudinal wave, ions pushing others ? If so, are they two speeds of propagation (the wave speed and the ions speed) ?
If ions are moving inside it, we can consider that there is a current in the salt bridge, correct ?
Are they families of salt bridges depending on how they work ?
Finally, can the salt bridge be exhausted before the half-cells (whether the solutions or the electrodes) ? It seems the salt bridge is quite small in basic cells examples compared to the sheer volumes of the solutions and sizes of the electrode, thus containing much fewer ions.


texts: Mechanism for conversion of imide to ester with NaH

texts: What is the mechanism of this reaction? My proposed mechanism is shown below, would it work?


texts: Electrophilic addition on cyclopropane using sunlight

texts:
I encountered a weird question in an exam. The statement says that instead of radical substitution, cyclopropane undergoes electrophilic addition reaction in sunlight.
I know that all saturated compounds give substitution reactions in sunlight but the answer key states that electrophilic addition takes place.
I couldn't find any source to prove this. Any help with an explanation and a verified source would be appreciated.


texts: Both calcium hydroxide and ethanol have a hydroxide group, then why isn't ethanol ionic?

texts:
I am confused on what is a hydroxide exactly is. For example, ethanol has a hydroxide group so does this mean it contains hydroxide ion? Does this make it ionic? I know it is a covalent molecule but why isn't it ionic?

Calcium hydroxide has $\ce{OH-}$ but how is this different than the $\ce{OH}$ group in ethanol? Is it covalent due to the fact it does not dissociate into ions when in aqueous solution? I know I'm missing something here.


texts:
Can you split carbonate ions into their constituent elements directly in the carbonate form? (so not first producing $\ce{CO2}$ and then decomposing the carbon dioxide)

(edit:)

I know that when running electricity through an aqueous solution containing carbonate ions and other element ions, the carbonate ions will act as individual groups and will not split (only after chemical reactions (for example the thermolysis of metal carbonates will produce carbon dioxide)) So this was just out of interest - how can the carbonate ion itself be split into its constituent elements if it can't be split with electricity (or at high voltage, could it then be split?)?


texts:
Are these all valid isomers for the formula $\ce{C_3H_6O}$? I drew the first five; my friend came up with the last three, which have double bonds. Are these all isomers or different? More importantly, are there any more?

Also in general, how can one come up with all the isomers for a molecule? I heard of graph theory, but I think that's a little bit too advanced for me. I guess the only way is to draw out as many as you can and name them to weed out redundant structures?


texts: How to create different levels of hydrophobicity on glass beads surface?

texts:
I have some glass beads and I need to create different levels of hydrophobicity on their surfaces (various contact angles). I know that this is possible by 'silanization'. However, I need to know about the following questions:

Whether there is any other reasonable method to do that.
In silanization, how can I change the level of hydrophobicity that my glass beads achieve? (e.g. by changing coating time, using different solutions or concentrations, etc.)

PS. I have the following solutions for silan. Please let me know if anybody has any comments on them or knows a more suitable solution for this purpose.
- CHLOROTRIMETHYLSILANE
- DICHLORODIMETHYLSILANE
- TETRAETHYL ORTHOSILICATE
- OCTADECYLTRICHLOROSILANE


texts: How to find the number of hydrogen atoms in 0.5 mol of hydrogen gas?

texts:
How do I calculate the number of hydrogen atoms in $\pu{0.5 mol}$ of hydrogen gas?
I presume the answer would probably somehow use the equation
$$n = \frac{m}{M},$$
where $n$ is the amount of substance, $m$ is the mass, and $M$ is the molar mass. However,  I'm not sure how to calculate it.


texts: Analysis of salts using color change when heated

texts: In order to detect basic radicals one of the preliminary test done is dry test tube heating. My book says that on doing so salts that would appear black when hot and cold are supposed to be Mn, Co, Ni or Cu salt. But does it refer to white salts turning black during heating or salts of any colour including black when it says that they appear black after heating?


texts:
In kryptomerism assignment, there was a question to compare more stable tautomeric form between 4-pyridone (1) and 4-pyridinol (2):

Answer: 4-pyridone.

My friend gave two plausible reasons:

$\ce{C=O}$ is more stable than $\ce{C=N}.$
$\ce{-N=}$ will have greater repulsion between the lone-pair and the double bond than the same in $\ce{-O=}.$

Though, not being convinced by his explanation, I have two questions. First, is the answer correct? And second, what's the reason if it's correct?


texts: What prompts sodium to give up an electron?

texts: What triggers sodium to convert from elemental Na to Na+? I know that it wants to have a full valence shell and all that, but how does it just eject the electron out?


texts: Asymmetric Suzuki coupling - saturated alkyl chain

texts:
9-BBN is applied for Suzuki coupling of a saturated alkyl chain with some alkenyl,alkynyl or even secondary alkyl halide like the modification attached:

(Saito, B.; Fu, G. C. Alkyl−Alkyl Suzuki Cross-Couplings of Unactivated Secondary Alkyl Halides at Room Temperature. J. Am. Chem. Soc. 2007, 129, 9602–9603. DOI:10.1021/ja074008l.)

For asymmetric hydroboration another bulky group is used - Ipc:

Is there an asymmetric version of Suzuki coupling employing saturated groups where instead of 9-BBN, Icp or a similar chiral group would be used or would the stereochemical information be lost during transmetallation?

EDIT: I've found this reaction sequence in Carey, Sundberg Advanced Org. Chem:

The product could be used for a Suzuki couping, but the question whether the stereochemical information is lost during coupling remains open.


texts: What are the oxidation states of sulfur in the tetrathionate ion?

texts: What are the oxidation states of the sulfur in the tetrathionate ion $\ce{S4O6^{2-}}$?


texts: Lewis Structures and electron distribution with oxygen atom

texts:
I am a novice in chemistry.

I don’t understand the way Lewis structure and how electrons are shared between elements.

For instance

As we know, Oxygen has six valence electrons that means it has 3 lone pairs.

So when oxygen wants to form a covalent bond, one of its valence electron should participate in the covalent bond.

In the picture above, however, even though that oxygen use one of its valence electron, we can clearly see that it still has 3 lone pairs. Well, they should be five electron Instead of 6.

In my interpretation, it should be like this ⬇:

Could you explain this?


texts: Alternative software for processing Molden files?

texts:
I am trying to salvage old data, and one of my output files is in Molden format.

I tried downloading Molden at its homesite but the link does not seem to work.
Is there another way to access Molden format files?

Thank you very much.


texts: Does a strong acid's conjugate base act as Brønsted-Lowry base?

texts:
Why is the conjugate base of a strong acid not considered a Brønsted-Lowry base? Is it because the base is so weak that it essentially has no ability to accept a proton?

(Quote from my lecture notes: "$\ce{Br-}$ is the conjugate base of a strong acid ($\ce{HBr}$), so it will not act as a Brønsted-Lowry base").


texts: How do I list these elements according to their radius?

texts:
$\mathrm{Z=33,\ Z=37,\ Z=9,\ Z=31}$

Since we shouldn't look at the periodic table, I found their groups and periods, what should I do next?


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Dicarbonyl amides, that is carboxylic acid anhydrides with their single-bonded oxygen between their carbonyl groups replaced with an amide group, I'm curious as to whether they're stable in water or unstable like carboxylic acid anhydrides.

This is what I mean by a dicarbonyl amide:

where R1 and R2 are organic substituents/hydrogen.


texts:
Bromothymol Blue is an indicator that turns yellow in acid, blue in base.

If I were to titrate NaOH with HCl, what color should I look for at the equivalence point? Should I titrate until the solution turns from blue to yellow or will there be an intermediate colour of green?

I know the salt produced (NaCl) has a pH of 7.


texts: Why is 2-methylpropene less in energy than its alkene counterparts?

texts: Other isomers include 1-butene, cis 2-butene, and trans 2-butene. Why would 2-methylpropene be less in energy if there is more steric hindrance?


texts: Energy required to break the "delocalised electron cloud" of benzene

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I learned that when benzene undergoes hydrogenation, $\pu{208KJ}$ of energy is given off and thus $\pu{152KJ}$ less energy than what would be given off if Kekule's structure was correct. My confusion is that my book says that this $\pu{152KJ}$ of energy is required to break the delocalized electron cloud - this does not make sense to me.

How is the energy discrepancy of value the energy required to break the delocalized electron cloud in the benzene?


texts: Can you make napalm out of gasoline and orange juice concentrate?

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According to the novel Fight Club by Chuck Palahniuk:

  The three ways to make napalm: One, you can mix equal parts of
  gasoline and frozen orange juice concentrate. Two, you can mix equal
  parts of gasoline and diet cola. Three, you can dissolve crumbled cat
  litter in gasoline until the mixture is thick.

The napalm is originally called napalm because is mixture of naphthenic acid  and palmitic acid. This makes me very skeptic about it being created by gasoline and juice. Also I see no reason for it to be frozen.

The only thing that sounds realistic to achieve the sticky effect is the use of cat litter - but you could as well just use dry dirt, couldn't you? And dirt doesn't really burn so you're weakening the burning effect.


texts: how many electrons are in the second subshell of this element?

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first of all sorry if I have some mistakes in my "chemistry words", I'm Iranian and I know the Persian terms but only some of the English ones.

So suppose we have an element (x) with the atomic number of 24, so the electron configuration would be something like this :
$_{24}x : 1s^2\ \ 2s^2 \ \ 2p^6\ \ 3s^2\ \ 3p^6\ \ 3d^{5}\ \ 4s^1$

So the question is : in the element above, how many electrons are there in the subshell of l=2 (which is the subshell of d) and how many are there in the l=0 subshell (which is the subshell of s)

P.S. I just took an exam and this exact question was in the exam, my answer was 5 electrons for 'd' and 7 electrons for 's'


texts: Controlling Current Density in Electrowinning Cell

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What are the parameters which govern the current density in an electrowinning cell? What equations relate Current Density to the applied potential difference?

Is it simply just Ohm’s Law J = σE? Where does redox at the electrodes come into play, if this is the case?


texts: If you add AlCl3 to water, why does the pH decrease?

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You are not adding any hydrogen ions, so why does the pH of the solution decrease?
Thank you in advance.

EDIT: I will add the context of my asking this question to clarify some details. This is not a homework question. I am preparing for an upcoming examination in Chemistry, and I found this statement in the mark scheme of a practice exam I was doing, and yet I don't understand why it is true.

I have learnt pH as simply being the negative log of the concentration of H+ ions. I fail to see how adding the above salt changes the pH, especially since HCl is a strong acid (hence it completely dissociates in solution).

Thought process: Is the pH change a result of Aluminium forming Aluminium Oxide?


texts: Which method can be applied to separate ferrofluid liquid from oil?

texts: I want to know if there is any substance, liquid or any other stuff to separate ferrofluid from oil after mixing them.


texts: Why acyl halides are not named as 1-substituted aldehydes?

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For acyl halides, IUPAC uses preferably the "acyl halide" type naming (e.g. acetyl chloride). But they can be theoretically named as aldehydes, where a hydrogen atom in the $\mathrm{CHO}$ group (carbon 1) is substituted by a halogen atom (e.g. acetyl chloride $\mathrm{CH_3COCl}$ has the same structure as acetaldehyde (or ethanal) $\mathrm{CH_3COH}$, so it can be named 1-chloroethanal - the name is probably valid, some sources list it as a possible one).

Of course, functionally acyl chlorides and aldehydes are very different (since acyl chlorides are much closer to corresponding carbonic acids), but structurally they aren't (and the systematic name should probably express the structure of a compound at first). Consider for example the naming of alkyl halides (halogen-substituted alkanes), where IUPAC switched to the substitutive nomenclature (for example, from "ethyl chloride" to "chloroethane", despite that chemical properties of chloroethane and ethane are very different).

The question may be incorrectly stated, since I'm not a (professional) chemist. Thanks in advance!