texts: Electric field required to split water into oxygen and hydrogen

texts:
Others sources typically say that the minimum voltage required to split water into hydrogen and oxygen is 1.229 V. Overvoltage is typically required in a practical device due to inefficiency leading to heat production.

However, suppose that two electrodes are separated by a large distance.  This will result in a very low electric field strength (generally, electric field equals $V/d$ where $d$ is the distance of separation).  Is there a threshold electric field level required for electrolysis to take place?


texts:
In my exam, my teacher asked me if the following is true:
"The chair cyclohexane has more axial hydrogens"
I did not have time to think, so I just put false.
And apparently I was right.
But, at home, I thought to myself: Does this question even make sense? Axial hydrogens are by definition only seen on cyclohexanes according to what I know.


texts: Properties that probe electron kinetic energy

texts:
This post is inspired by a question regarding the meaning of off-diagonal elements of the KE matrix (in some AO basis). One answer suggests that a diagonalized KE matrix might not be very useful. I take the liberty of quoting:

  I am not sure it really makes sense to give much of an interpretation to this, however, because what one is really interested in is diagonalizing the Fock matrix, of which the kinetic energy is only one part.

Indeed, we usually are interested in the wavefunctions (eigenfunctions of the Hamiltonian) whose eigenvalues are the energies of electrons inhabiting the orbitals. We like to think of electrons as existing primarily as standing waves with constant energy. Such states are central to computing electronic spectra and ionization energies, for instance.

This leads me to ask two related questions:

1) Is a diagonalized KE matrix, that is, an orbital representation in terms of kinetic energy (rather than full Hamiltonian) ever useful to chemists?

2) What if any spectroscopies probe the instantaneous value of the kinetic energy of electrons (or some portion of the KE spectrum)?


texts: Why don't we use an alkyl halide directly in Gabriel Phthalimide Synthesis?

texts: In Gabriel Phthalimide Synthesis, why do we use $\ce{KOH}$ in first step rather than directly adding an alkyl halide?


texts: Advantages of thioesters over esters in fatty acid catabolism

texts: In several metabolic pathways, Nature (live systems) chooses to make esterification using thioesters (CoA) and not esters. I would like to know what is the main aim of the Nature with this choice: faster reactions or more extensive reactions?


texts: What can be used as an electrolyte in water to perform electrolysis other than salt?

texts:
I am looking for an electrolyte to use in water to perform electrolysis. It can't be salt, as salt ($\ce{NaCl}$) would cause the chemical reaction of
$$\ce{2H2O + 2NaCl -> Cl2 + H2 + 2NaOH}$$
or

$$\ce{H2O + NaCl -> HCl + NaOH}$$

Which both make products with poisonous chemicals (ex: $\ce{NaOH}$ = Sodium Hydroxide (aka lye) which is poisonous). I am looking for a chemical I can use to create the pure forms of hydrogen and oxygen from the electrolysis process. I understand how electrolysis works, and have tried it before, but am looking for something that could be used as a non-poisonous electrolyte. I read that baking soda could be used, would that produce what I am looking for?


texts:
Considering oxidation mechanism of side-chains in arenes, it is known that side-chains get oxidized to carboxylic group ($-COOH$).

Below is a picture of 2-Methyl, 2-Phenyl Propane. When it gets refluxed with acidified $KMnO_4$ or acidified $K_2Cr_2O_7$, it should be oxidized to give benzoic acid.

But according to the provided source, it seems 2-Methyl, 2-Phenyl Propane doesn't react with the above oxidizing agents.

My question is,

Why does this compound disobey the general oxidation of benzyl derivatives?

Note, the source has a OH on position 4 of the ring, that makes it difficult for me to name it.

Source: https://papers.gceguide.com/A%20Levels/Chemistry%20(9701)/9701_s13_qp_41.pdf
Qno:5 c) i)

Or is the OH that makes the difference in this question?

2-Methyl,2-Phenyl Propane:


texts: Why does an increase in temperature decrease the electrode potential?

texts:
According to the Nernst equation, the electrode potential $E$ is
$$E = E^\circ - \frac{RT}{nF}\ln\frac{[\ce{M}]}{[\ce{M^{$n$+}}]}$$

Question is, why? Assuming a simple galvanic cell, we know that in general if the temperature is increased, there should be more collisions of the solution with the electrode, resulting in a higher accumulation of the metal ions on the electrode. It should also make it easier for the metal atoms in the electrode to leave the electrode and go into the solution.

Also, if temperature reaches zero, the reaction should stop altogether as there would be no more collisions and no more potential difference should be developed on the electrodes. Yet according to the Nernst equation if temperature reaches zero, maximum standard electrode potential would be reached instead. Where am I going wrong?


texts: Is there a metal that melts and solidifies quickly?

texts: Is there any kind of metal that melts very quickly with very low heat or temperature, and at the same time, becomes hard very quickly?


texts: Calculating equilibrium partial pressures of a gas given Kp

texts:
My work:

${K_p = 28.4 = \frac{[NOBr]^2}{[NO]^2[Br_2]}=\frac{[NOBr]^2}{[107]^2[160]}} \rightarrow$$\ce{[NOBr]=7212 torr}$.

This doesn't match up with the given answer. I don't see why 262 torr is the correct answer. I correctly set up the equilibrium constant expression and everything in the reaction equation is in the gas phase so they are all included and I used only equilibrium concentrations.

Another problem with the same issue:


texts: Skin permeability, for all chemicals or just some?

texts:
On skin permeability, according to Wikipedia:

"Human skin has a low permeability; that is, most foreign substances are
unable to penetrate and diffuse through the skin. Skin's outermost
layer, the stratum corneum, is an effective barrier to most inorganic
nanosized particles.[22][23]"

However there is little to be found on exactly what chemicals can permeate the unbroken skin.

This paper http://oem.bmj.com/content/61/4/376.full states the following:

"Many chemicals can cross the unbroken skin."

"However, the highly lipophilic nature of most solvents can also result
in dermal uptake when deposited on the skin."

Is Wikipedia's statement incorrect? What chemicals can permeate the skin, which ones cannot, and why?


texts: How closely should the energy components of ab initio SCF results at a stationary nuclear configuration preserve the virial theorem?

texts:
When running a SCF geometry optimization for water molecule, I found that the energy components of the optimized geometrical structure appear to deviate from Virial theorem sightly:

Kinetic energy = 75.424942151953331
Total energy = -75.585962823645531

How should this discrepancy be interpreted? Is it an indication of inaccuracy in the geometrical optimization algorithm of the software being used?


texts: How does the "sample type" selection on the MassHunter software for Agilent 7900 ICP-MS affect the quantitative results?

texts:
I'm new to using the instrument, and recently I have tried to measure Cr in both the eluent(1% nitric acid) and a method blank (also 1% nitric acid, but after it has gone through the entire analytical procedure).

In the batch settings, I set the "sample type" for the eluent as "bkgd"  (it stands for background), and my method blank as "samples". The result was that I obtained a negative CPS signal for my method blank. On the offline data analysis program, I was able to change the sample type of the the eluent to "samples" and told the program to reprocess the data, and lo and behold, the CPS signal goes back to positive.

What I think happened was that whenever I set something in my batch as the sample type bkgd, the instrument automatically references that cps count as zero, so that the subsequently analysed sample's signal will be referenced from that. However, I do not know exactly how the different sample types will affect my measurements. I have tried looking up the instrument manuals from Agilent, but none of them so far have given me any insight into this.

There are several sample types to choose from, such as blk (for blanks), sqstd(for tuning solution standards), calblk, etc. I don't want to risk selecting any of these until I'm confident I know what they do to my data.

Any response will be appreciated.


texts:
I am trying to follow a published paper. It is a one-pot synthesis of pyrazole from a ketone and and acid chloride via a diketone intermediate.

Here is the produre from the paper:

General Procedure: Ketone (2 mmol) was dissolved in 5 mL dry toluene in a screw cap vial (with septum) and then the solution was cooled to 0°C under nitrogen. LiHMDS(2.1 mL, 1.0 M in THF, 2.1 mmol) was added quickly via syringe with agitation stirring and the formed anion was allowed to sit for approximately 1 minute before the addition via syringe of acid chloride (1 mmol) in one portion with stirring. The vial was then removed from the ice bath and allowed to stand for 1 minute, then 2 mL AcOH was added with stirring. 10 mL EtOH and 5 mL THF was added to form a homogeneous
mixture, and then hydrazine hydrate (2 mL, 1.1 g, 34.3 mmol) or substituted hydrazine(5 mmol) was added and the mixture was allowed to auto-reflux and was held at that temperature for 5 minutes, when LCMS showed that all diketone had reacted. The resulting solution was added to 1.0 M NaOH solution and extracted with EtOAc. The organic fraction was then washed with brine, dried over Na2SO4, and evaporated under reduced pressure.See specific compounds for purification details.

My questions are:

What is the purpose of excess hydrazine hydrate, acetic acid, and enolate in producing the pyrazole?
How many molar equivalents of sodium hydroxide should I use at the end of the reaction?


texts: Calculating the wavelength of an emitted photon of a Ne^9+ ion

texts:
I'm supposed to calculate the wavelength of an emitted photon going from the 6p orbital to the 2s orbital. The first part of this problem will be to use the equation

$$E=-{Rh\over n^2}$$

in order to calculate the energy.

That's all easily done when considering a hydrogen atom. Our chemistry professor, however, has told us to consider the ion $\ce{Ne^9+}$.

Therefore, my question is this: What's the difference (if any) when calculating the energy when it comes to this specific ion? What part does the nucleus play in this?

Also side note(Just to make sure): There is no difference when the professor refers to the orbital numbers right? I'm only supposed to consider the principal quantum numbers, correct?


texts: Effective diffusion coefficient of a species in a heterogeneous mixture

texts:
I want to calculate the effective diffusion coefficient of hydrogen radical in a mixed-phase consisting of metal oxide, metal hydride and metal. I consider the interfaces to be diffuse.

How can I calculate the effective diffusivity or effective diffusion coefficient of a species (ion or radical) in a heterogeneous mixture consisting of 3 different components? Can I weight average the diffusivities or is it more complicated than that?


texts: Explanation of the orbital energies resulting from Jahn-Teller distortion of octahedral complex using MO theory

texts:
I am confused about the energies of the orbitals after Jahn-Teller distortion of an octahedral complex. Take elongation for example.
To my understanding, since the ligands on the $z$ axis move away, there is less orbital overlap with the $d_{z^2}$ metal orbital, leading to weaker orbital interactions, leading to the antibonding orbital being lowered in energy.
There are two things I don't get: 1. The lowering of $d_{xz}$ and $d_{yz}$ and 2. the raising in energy of the $d_{x^2-y^2}$ and $d_{xy}$ orbitals.
1. The $d_{xz}$ and $d_{yz}$ don't seem to have the correct symmetry to sigma bond with any $p$ orbitals of the ligands. They are nonbonding in a perfect octahedron, so how can the be lowered in energy after distortion? Maybe they only appear lower relative to the $d_{xy}$?
2. Are they not actually raised in energy, only appearing higher relative to the $d_{z^2}$ and $d_{xz}$ and $d_{yz}$ orbitals? Or are the equatorial bonds shortened so there is a stronger interaction, raising the $d_{x^2-y^2}$? If so, then why is the $d_{xy}$ orbital raised?
Is there an explanation for the orbital energies using MO theory? If you could clear up my confusion that would be great. Thanks!


texts: What I am wondering, are aspartic acid and glutamic acid at physiological pH present in zwitterion form. In my textbook it says that all aminoacids are at pH 7,4 or 7 in zwitterion form. I wonder how if pKa values of side chains of aspartic acid is 3,65. There are also arginine, lysine, cysteine and tyrosine that  will not have overall neutral charge at pH = 7.


texts: How to electronically calculate alcoholic level of a liquid

texts: Is there any way to estimate the alcohol content of a drink with an electric test? Is alcohol in a liquid (e.g wine) dependent on the drink's conductivity?


texts: What components of safety should be included in a chemistry laboratory experiment conclusion?

texts:
The focus of my question here is this: In a laboratory there is a Bunsen burner, a hot plate, hydrochloric acid, and concentrated ammonia. What would you mention about safety precautions?

As students of chemistry and science, we often need to write detailed conclusions about our laboratory experiments. This eventually becomes second-nature, but to have an an idea of which of the safety measures taken to include are often useful to ensure ourselves that we have not left anything out.

I believe that the following are some of the the most important components of any well written conclusion in a lab entry, something that your lab instructor will read and grade you on.

Purpose: Explain the goal and purpose of the experiment in a clear and concise manner.
Findings: Presents a reasonable interpretation of, and logical explanation for all findings pertaining to the problem and stated purpose.
Discussion: Discusses possible sources of error in detail, including their effect on the results and ways of avoiding them in the future.
Referencing experimental findings and explaining the known/expected results we were looking for. Mentioning and discussing reasons for trends, if any.

In particular my instructors last year were often interested in:

Safety: This is often what I always got marked down for. I would explain that hydrochloric acid is a caustic substance and should be treated with care to not get on your tissue by wearing clothing that does not expose skin and closed toe shoes, and to always carry out the experiment with safety goggles securely fastened. It never seems to be enough for them, even if I mention eye flush and chemical shower in case of emergencies. Should I mention to not snort or freebase it? /end sarcasm

Have I missed any safety components that should be included in a "complete" conclusion for the average experiment? What else might I have left out that instructors tend to look for?


texts: Confusion in the line written in my book

texts:
In my class 11 chemistry NCERT book ,there is a line in chapter P-block.

The line is

  The oxidation state two unit less than the group oxidaton state become progressively more stable for heavier elements in each group . Due to 'inert pair effect'

I could not understand this , what they meant to conclude from it.

Can anybody explain me with an example.


texts: Do perfect gases react when placed in a container whose volume can vary?

texts:
Suppose that $n$ moles of four generic perfect gases are made to react in a container, whose volume can vary, at a constant temperature and pressure, according  to the formula
$$\ce{A(g) + B(g)<=>C(g) + D(g)}$$
and suppose also the the equilibrium constant $K_c$ is known.

Now, if temperature and pressure are constant, then so will the density of the gases be. But if the density is constant, then the concentration of the gases will be constant as well, regardless of the number of particles present in the container (this is more or less the same argument that my chemistry textbook makes to justify the exclusion of concentration of solids and liquids from the expression of the equilibrium constant).

But if the concentrations are constant, then at the outset of the reaction, when there are $n$ moles of each gas, the reaction is already at equilibrium, because the reaction quotient $Q=K_c$.

My question is the following: is there something wrong about this argument? If not, how will the number of moles of each gas vary with time?


texts: Why inert pair effect is seen in P- block elements only

texts: why is inert pair effect specific to certain groups? Why heavier transition elements DO NOT show inert pair effect?


texts:
In the preparation of sulfuric acid through contact process,

Hot sulfur trioxide passes through the heat exchanger and is dissolved in concentrated $\ce{H2SO4}$ in the absorption tower to form oleum:
$$\ce{H2SO4(l) + SO3(g) → H2S2O7(l)}$$
Oleum is reacted with water to form concentrated$\ce{H2SO4}$.
$$\ce{H2S2O7(l) + H2O(l) → 2 H2SO4(l)}$$

The sulfuric acid obtained is $\ce{96-98}$% pure. That means $\ce{2-4}$% is impure and contains byproducts and other oxoacids of sulfur including trisulfuric acid. If the sulfur trioxide to be adsorbed on $\ce{H2SO4}$ is in excess, it can form trisulfuric acid.
$$\ce{H2SO4(l) + 2SO3(g) → H2S3O10(l)}$$
But the amount of trisulfuric acid is negligible and can be omitted. But is it an actual compound? Can it be isolated? Can it exist in room temperature?
Pubchem identify it as a compound and also has a unique ID. It also has an unique CAS number.

It has $\ce{S=O}$ bonds and $\ce{S-OH}$ bonds (characteristics of oxoacid of sulfur) but still it is not mentioned in that list (link above). Why?


texts: We all know that an atom starts moving faster when it's heated.But actually atom is not some new thing itself in the sense that it is just a bunch of electrons and protons. So, I think that same happens to the electrons or protons within. What does?


texts: What is melting? Which bonds do we break to melt something?

texts:
To melt diamond, we have to break the covalent bonds, which we can consider 'intermolecular' because it is one giant molecule.

To melt Methane, we have to break the van der Waals (intermolecular) forces.

For $\ce{NaCl}$, ionic bonds, which are intermolecular as well in a sense.

But I've read that melting graphite also requires breaking the covalent $\ce{C-C}$ bonds rather than just breaking the van der Waals forces between the layers.

And for cross-linked polymers, I've read that melting involves breaking only the bonds linking the two polymer chains.

So I guess what I want is a precise definition of melting. Does it involve breaking the weakest bonds? The intermolecular forces? The intramolecular bonds?

When we melt a molecule of, say, $\ce{H2O}$, we imagine molecules of $\ce{H2O}$ roaming around with little intermolecular forces, as most hydrogen bonds have been broken.

What do we 'imagine' when we melt diamond, or a cross-linked polymer, or graphite, or ionic compounds like $\ce{NaCl}$?


texts: What are the half reactions for the redox reaction between SO2 and iodine?

texts:
What are the half reactions for the redox reaction between $\ce{SO2}$ and iodine? The relevant chemical equation:
  $$\ce{ SO2 + H2O + I2 -> H2SO4 + 2HI}$$

This is what I think it is, not sure if it's correct.

Oxidation: $\ce{SO2 + 2H2O -> SO4^2- + 4H+ + 2e-}$

Reduction: $\ce{I2 + 2e- -> 2I-}$


texts: Can solid acids and bases have pH values? If not, how are they classified as acids or bases?

texts:
This answer states

  $\mathrm{pH}$ is the aqueous concentration of $\ce{H3O+}$ or $\ce{H+}$ ions in soution. I would not say that ice lacks $\ce{H3O+}$ and $\ce{OH-}$ ions as ice's structure would allow for such, however, since the ions are not in aqueous solution, the material cannot rightfully have a "$\mathrm{pH}$" as we know it.

How does that generalize to solid acids and solid bases? Can solid acids and bases have pH values? If they don't have a pH, how would the solid form of a new compound then be classified as an acid or a base?


texts: Stability and Rate of Formation of Carbocations

texts:
Consider the dehydration reaction of the following compounds with $\ce{H2SO4}$:

(a) Tert-butyl alcohol
(b) 3-Methylbut-2-en-1-ol

Consider the protonation of the $\ce{OH}$ group followed by the removal of a water molecule. In (a), we get a tertiary carbocation whereas in (b) we get a primary allylic carbocation. As far as I know, a tertiary carbocation is more stable than a primary allylic carbocation. Therefore I expect (a) to be dehydrated at a faster rate.
But if I consider a resonating structure of the carbocation formed in (b), I get a tertiary allylic carbocation which is more stable than the tertiary carbocation.
My main question is when comparing the rate of reaction of 2 different compounds, do we rank them based on the stability of the initial carbocation formed, or based on the most stable carbocation formed by these compounds after resonance?
I believe that the compound having the tertiary carbocation would be formed at a faster rate as the initially formed intermediate is more stable.

Could anyone please shed some light on this?


texts: What is the magnetic moment of tris(oxalato)nickelate(IV)?

texts:
I'm really struggling with finding the magnetic moment of this complex:

In the solutions, it says that it is 2.83 BM (which corresponds to 2 unpaired electrons). However, in drawing out the d orbital diagram (using crystal field theory) I found that there are actually 4 unpaired electrons (since there are 6 d electrons and the complex will be octahedral and high spin). Am I missing something or is the solution wrong?


texts: Alkali earth metals produce white coloured salts with halogens like chlorine. But Muriate of potassium available in India generally used as a fertilizer is pink coloured(reddish white actually), why is it so?


texts: Solution based measurement of Solvent-Accessible Surface Area of macromolecules

texts:
The Solvent-Accessible Surface Area (SASA) is a valuable metric for looking at protein folding and protein-protein interactions. However, this measurement is typically done by calculating the SASA from a solved (and generally static) structure.

Chemical probes like diazirine and hydroxyl radicals show some bias regarding where they tend to bind. I'm realizing while I'm writing this question that NMR is a perfectly valid method to determine a solution based structure and then calculate the SASA. Similar strategies has also been used to examine structured RNAs. I'm curious about the variety of these methods and how accurate they are.


texts:
These might be basic question but they are quite confusing to me?

If $\ce{Sc+}$ doesn't exists, why does $\ce{Ti^{2+}}$ exist?

on the similar account why does this trend increases at first( till Mn) and then decreases?
My book just concludes that the general trend is due to increase in $Z_{\mathrm{eff}}$ and decrease in atomic radius.

A little insight will be really  appreciated.


texts: What kind of functional groups can give positive silver mirror test?

texts:
kindly help me with a mechanism of Tollen's reagent that could explain how it acts as a reagent with organic compounds I wish to understand how we can analyze through structure whether a given compound will give a positive silver mirror test or not.

i found a mechanism that explains it's reaction with aldehydes but again it also gives a positive test for terminal triple bond. (link to that question)
I am unsure whether it could give the test with any other functional group also

link to an article that could give more insight on this would be of great help

p.s. I m really new to asking questions so please do help me in asking better questions and framing them better


texts:
I am trying to understand the nomenclature of amoxicillin:

The IUPAC name that Wikipedia has given is (2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid.

I think I understand most of it but I have two problems:

Why is there a 24 before the carboxylic acid?
There is a $\ce{C=O}$ group between two nitrogens that doesn't appear in the name. I was expecting an amide, rather than amino or oxo.


texts: Bioisosteric replacement using SMARTS (KNIME and RDKit)

texts:
I am trying to create a KNIME workflow that would accept a list of compounds and carry out bioisosteric replacements (we will use the following example here: carboxylic acid to tetrazole) automatically.

NOTE: I am using the following workflow as inspiration : RDKit-bioisosteres (myexperiment.org). This uses a text file as SMARTS input. I cannot seem to replicate the SMARTS format used here.

For this, I plan to use the Rdkit One Component Reaction node which uses a set of compounds to carry out the reaction on as input and a SMARTS string that defines the reaction.
My issue is the generation of a working SMARTS string describing the reaction.
I would like to input two SDF files (or another format, not particularly attached to SDF): one with the group to replace (carboxylic acid) and one with the list of possible bioisosteric replacements (tetrazole). I would then combine these two in KNIME and generate a SMARTS string for the reaction to then be used in the Rdkit One Component Reaction node.

NOTE: The input SDF files have the structures written with an
attachment point (*COOH for the carboxylic acid for example) which
defines where the group to replace is attached. I suspect this is the
cause of many of the issues I am experiencing.

So far, I can easily generate the reactions in RXN format using the Reaction Builder node from the Indigo node package. However, converting this reaction into a SMARTS string that is accepted by the Rdkit One Component Reaction node has proven tricky.
What I have tried so far:

Converting RXN to SMARTS (Molecule Type Cast node) : gives the following error code : scanner: BufferScanner::read() error

Converting the Source and Target molecules into SMARTS (Molecule Type Cast node) : gives the following error code : SMILES loader: unrecognised lowercase symbol: y

showing this as a string in KNIME shows that the conversion is not carried out and the string is of SDF format : *filename*.sdf 0 0 0 0  0 0    0 V3000M V30 BEGIN etc.

Converting the Source and Target molecules into RDkit first (RDkit from Molecule node) then from RDkit into SMARTS (RDkit to Molecule node, SMARTS option). This outputs the following SMARTS strings:

Carboxylic acid : [#6](-[#8])=[#8]
Tetrazole : [#6]1:[#7H]:[#7]:[#7]:[#7]:1

This is as close as I've managed to get. I can then join these two smarts strings with >> in between (output: [#6](-[#8])=[#8]>>[#6]1:[#7H]:[#7]:[#7]:[#7]:1) to create a SMARTS reaction string but this is not accepted as an input for the Rdkit One Component Reaction node.

Error message in KNIME console :
ERROR RDKit One Component Reaction 0:40       Creation of Reaction from SMARTS value failed: null
WARN  RDKit One Component Reaction 0:40       Invalid Reaction SMARTS: missing

Note that the SMARTS strings that this last option (3.) generates are very different than the ones used in the myexperiments.org example ([*:1][C:2]([OH])=O>>[*:1][C:2]1=NNN=N1). I also seem to have lost the attachment point information through these conversions which are likely to cause issues in the rest of the workflow.
Therefore I am looking for a way to generate the SMARTS strings used in the myexperiments.org example on my own sets of substituents. Obviously doing this by hand is not an option. I would also like this workflow to use only the open-source nodes available in KNIME and not proprietary nodes (Schrodinger etc.).
Hopefully, someone can help me out with this. If you need my current workflow I am happy to upload that with the source files if required.
Thanks in advance for your help,
Stay safe and healthy!
-Antoine


texts: Are there actually any reactions during which STATIC equilibrium is reached, as opposed to dynamic?

texts: Static would be where a set amount of both products and reactants is formed. Dynamic would be where both the forward and backward reactions occur at equal rates, meaning no change in the overall product and reactant concentrations.


texts: Comparing of melting point of dibromo p-xylenes

texts: How to compare the melting points of the above isomers? I know that melting point depends upon the packing of the molecule, more efficient the packing, higher is the melting point. Symmetry in a compound also increases it's melting point. But all the above compounds have symmetry in them and I can't figure out how to compare their melting points.


texts: What theoretically is the smallest cyclic trans hydrocarbon to correspond to a local potential energy minimum?

texts:
Trans-cyclooctene is isolatable at room temperature.

Trans-cycloheptene is also known at low temperature.

Ab Initio Conformational Analysis of trans-Cyclohexene (1995) says that there is spectroscopic evidence of the existence of trans-Cyclohexene, but that trans-cyclopentene hasn't been studied.

So I'm looking for any further information on trans-cyclopentene, trans-cyclobutene or trans-cyclopropene, particularly whether any of these have been theoretically calculated as (or ruled out as) corresponding to a local potential energy minimum.


texts:
I have (very) basic knowledge in chemistry.

I am curious as to why osmosis works. I read a couple of introductory chemistry books and also searched online but most explanations I found only explained the phenomena (i.e. solvent molecules move through semipermeable membrane from low solute concentration area to high concentration area), but not the reason behind it at the molecular level (i.e. what makes more solvent molecules move towards the high solute concentration area than in the reverse direction).

Wikipedia seems to go a step further:

  ... there is an interaction between the solute and water that counteracts the pressure that otherwise free solute molecules would exert.

And a bit later:

  The virial theorem demonstrates that attraction between the molecules (water and solute) reduces the pressure, and thus the pressure exerted by water molecules on each other in solution is less than in pure water, allowing pure water to "force" the solution until the pressure reaches equilibrium.

I think I understand what it means, but what I don't understand is this: osmotic pressure is said to be a colligative property, i.e. only affected by the concentration of the solute and not by its type. If the reason for osmotic pressure is the attraction between water and solute molecules - wouldn't we expect different osmotic pressures for different kinds of solutes?


texts: Why does the temperature remain constant during freezing?

texts:
I know it's the most silly question one could ever ask but why is that so?

I am aware of what latent heat means and I also know it has something to do with freezing too.

Say I have with me, a mug of hot water and I put it to freeze. And so the temperature reduces first to 273 K and then remains constant to convert into ice and decreases once again.
 But why does the temperature remain constant though? Does this has something to do in molecular level?


texts: Is m-cresol or p-cresol more reactive towards electrophilic substitution?

texts:
Which is more reactive towards electrophilic substitution, meta-cresol or para-cresol?

Both oxygen and methyl are activating groups. I don't know on what basis do I compare their reactivity. There's just a change in the position of one of the group.

My book says meta-cresol is more reactive and the reason given was

  If two groups are working for the same effect at the same time, then their effect decreases.

I don't understand the reasoning and hence the answer. Any help would be appreciated.


texts: Why does lithium from the nitride whereas the other alkali metal forms the azide?

texts:
What property of lithium makes them forms the nitride, lithium nitride $\ce{Li3N}$ whereas the other group 1 elements forms the azide, like sodium azide and potassium azide - $\ce{NaN3}$ and $\ce{KN3}$ respectively?

Does lithium azide exist? If so, what is its structure?


texts: Are there any nonflammable thermal insulators which can be made at home?

texts:
I am trying to build a homemade thermos. It needs to be able to conserve the heat in 125 ml of water for 15 minutes.

However, unlike a normal thermos, it also needs to be able to be heated. What homemade substances can I use that are not flammable, yet provide a relatively high degree of insulation?

Note that my thermos will be heated with a flame from a candle for 25 minutes.


texts:
Is it safe to boil water in a foil pan on an electric burner?

Can the metal leach into the water?

I've heard some reports recently about avoiding aluminum foil due to it leaching into food.

Photos of the items in question, below:


texts: What does it mean for a higher glass transition temperature in terms of crystallinity?

texts: The glass transition temperature is associated with amorphous regions in a polymer. If I have observed in a lab experiment that polymers with a higher glass transition temperature tend to have less crystalline structures, how should I interpret this?


texts: How would the crystal structure of sodium stearate look like?

texts:
In my lessons of solid state, I was taught about Bravais Lattices, and Face Centered, Body Centered, and Primitive cubic lattices, to name a few. All these crystal structures had this assumption, that ions/atoms are considered as hard spheres.

Considering sodium stearate, the stearate anion isn't a hard sphere, not by a long shot. Since Bravais lattices assume spherical atoms, I am led to believe that sodium stearate doesn't follow Bravais lattice structures.

So my question is, what is the crystal structure of sodium stearate?


texts: Where can I look for a short chain photopolymer?

texts:
I am by no means an expert in this field, so please be patient with my explanation. I am looking for a photopolymer with very specific properties. I am not sure how realistic it is to find such a material, but I will list the properties in the hope that someone can point me in the right direction, to help me narrow my search.

What I am looking for is a short chain monomer (hopefully no longer than $\pu{5 nm}$) that polymerizes in response to light (I understand a photoinitiator will also probably be needed), and has a hydrophilic head, to allow it to bond to my aluminum (hydrophilic) substrate. In the polymerized form, it has elastic properties, as well as a hopefully low mass to elasticity ratio.

A few things that I have thought of that could work include negative photoresists, such as those used for mask lithography, as they would demonstrate very small features (however, they may be too brittle), or 3D printing photopolymer (I am cautious to use the latter, as it is not made for such small dimensions, though it would probably work for the elasticity).

What I am trying to do is make a very thin membrane to rest on top of a nanoporous surface (where the pores are $\pu{20\pm5nm}$, that, upon being exposed to light, hardens to an elastic thin film.

I have more of a biochemistry background, but I would very much appreciate a nudge in the right direction, either via a repository where I could possibly find such a material, or through learning resources specific to this type of material, or, even better, chemicals that have similar properties to the one I am looking for.


texts: Finding the color of crystal violet theoretically

texts:
I am trying to find the color of an organic molecule, crystal violet, theoretically.

I suspect that the color is due to the large conjugated system. My question is, how would I go about finding the energy levels of such a system? I know how to solve the Schrodinger equation for a particle in a ring or a box (i.e. benzene, or a poly-diene) to solve for energy levels and find the lowest-wavelength transition. But how would I do it for this sort of molecule?


texts: How accurately does (pKa1 + pKa2) / 2 estimate the pH of an amphoteric salt?

texts:
This question came up when answering Find the pH and amphiprotic salt is added to water at room temperature. If we dissolve $\ce{NaHA}$ in water, the species $\ce{HA-}$ can act as acid or base:

$$
\begin{align}
\ce{H2A &<=> AH- + H+}\\
\ce{HA- &<=> A^2- + H+}
\end{align}
$$

The $\mathrm{pH}$ of the solution can be estimated as

$$\mathrm{pH} = \frac{\mathrm{p}K_\mathrm{a1} + \mathrm{p}K_\mathrm{a2}}{2}$$

My question is how accurate this estimate is, depending

on concentration of the amphiprotic salt (as the concentration approaches zero, the $\mathrm{pH}$ should approach 7),
on the average of the $\mathrm{p}K_\mathrm{a}$ values (the closer these are to neutral, the smaller the difference between $[\ce{H2A}]$ and $[\ce{A^2-}]$), and
on the difference between the $\mathrm{p}K_\mathrm{a}$ values (the bigger the difference, the lower the percentage of $\ce{NaHA}$ undergoing acid or base reactions).

So depending on these three variables, how accurate is the estimate? My guess is that high concentration, average of $\mathrm{p}K_\mathrm{a}$ near neutral and difference between $\mathrm{p}K_\mathrm{a}$ low would give good estimates. When any of these parameters a very different from those "ideal" conditions, the estimate probably gets worse.


texts: Is there a possible distortion of XeF6 from Oh point group to reduced symmetry?

texts:
Below the molecular orbital diagram for $\ce{XeF6}$ (from What is the molecular structure of xenon hexafluoride?)

I am trying to figure out if a distortion from $O_h$ can take place and to which (lower symmetry) point group it would be. I know that it will involve the HOMO $a_g$ interacting with the $t_u$ orbital (bonding). Using a descent of symmetry table for $O_h$, I have found that the $a_g$ must remain completely symmetric. The part I am confused about is, looking at the descent of symmetry table, I am looking for an $a_g$ component of $t_u$ in a point group. I am using the following table:

$t_{1u}$ does not $a_{1u}$ in the table. Literature actually suggests $C_{3v}$ as the resulting distortion, but how would I know this when it isn't in the table? and I was wondering where I am going wrong in my approach?

Also, I am curious where the subgroups fit into the table, as $C_{3v}$ is not there but what does this mean?


texts: Can you determine when the orbtials of an atom will hybridize?

texts: We know that when it comes to C its orbitals hybridize (they become sp3 , sp2 or sp) and the energy levels of an hybridized orbital of this kind is lower than that of the p orbital that formed it but higher than the s orbital so for example energetically speaking is more convenient for an atom to have its electrons (even if they are non-bonding and they don't do too much) in an hybridized orbital if possible.And I know that O and N also can hybridize so the energy barrier between their orbitals (the s and the p orbitals) is not that high to be unable to do this so why don't they just hybridize first in O2 or N2 and then form the molecular orbitals like is the case with C-C bonds , why in the case of O-O bonds we have no hybridization? I mean ok I get the perspective of being able to form a double bond but O2 can have a double bond even if it was sp2 hybridized and then all the non-bonding electrons would be in lower energy orbitals (the other sp2).


texts:
If you have a weak base XOH titrated with a strong monotonic acid, where do you start with that? Would you first have the base react with water and break up and determine how much of it does? Or just it breaking up alone, not reacting with water? Reacting just with the acid right away? I'm not sure where to start for this problem type...

I need to find the pH at the equivalence point. I have the concentrations of the acid and base, which are both equal, no volume given.


texts:
I have been using deodorant to propel potatoes (potato gun :D), but I want to switch over to pure butane. However, in order to do this safely I have to know how much butane is typically in deodorant (percentage). If you do know, please also include a source.

Secondly, for a potato gun, is it wiser to use butane or propane?

And could a spark ignite butane? Or is a real flame needed? Tested this already, it does.


texts:
I'm actually looking for 2 chemicals that will produce a really small exothermic reaction. The 3rd chemical would be there to separate the chemicals - like oil,  water, and air.

Ideally, the 3rd chemical would be a nonreactive oxide of the other 2.

Also, they should all stay liquid on a hot summer's day.

As stated, they should produce a small exothermic reaction - I'm looking for mostly light that won't melt a glass bottle.
Melting the bottle isn't ideal, but I can find a stronger material too.

Also, the chemicals should be as nontoxic as possible. They don't have to be though.


texts: Do all polymers contain either carbon or silicon?

texts:
Is either carbon or silicon present in every known polymer?

If not, is there a small group of elements that, between them, are present in every known polymer, or can polymers be based on a lot of different elements?


texts: Why is the boiling point of rectified spirit lower than alcohol absolute?

texts:
The boiling point of rectified spirit is ($78.1~\mathrm{^\circ C}$) while that of absolute alcohol is ($78.3~\mathrm{^\circ C}$). I know its too small, but shouldn't the addition of impurities increase the boiling point?

What qualifies as an impurity? Is it that solids like salt only can be called an impurity? — which increase the boiling point of water?


texts: Can carbon dating tell how long a species would survive?

texts:
Carbon ($\ce{^{14}C}$) is used to determine how long a particular species has lived or how old it is. Can we use the same isotope to derive how long a species may survive? (My understanding is still quite at infant level on half-life concept)

Is it prohibited or is it impossible? If not possible, why?


texts:
I was recently shown an object and asked if it was a chestnut. It looked like a regular horse chestnut except instead of an opaque brown surface, the entire nut was slightly translucent, in similarity to dark amber, and with an almost oily texture to the surface.

Is there a chemical that this supposed chestnut could have possibly been dipped in, to give it this translucence?

Apologies if this question is incorrectly tagged, if so, re-direction most appreciated.


texts: Some substances appear white when crushed while others do not. Why?

texts:
Calcite crystals are semi-transparent but turn white when crushed. I used to think that it has something to do with the scattering of all wavelengths of light from small particles. But that cannot be the whole story. By that explanation crushed carbon should also appear white (which is not the case).

So my question is why do some substances appear white when crushed while others do not.


texts: Books for a very advanced 3rd grader (elementary school)

texts:
My daughter is a 3rd grader, but she reads at 8th grade level, and she is 2 grade levels ahead in math.

She reads everything she gets her hands on.

She took some chemistry activities, and she loved them. ("Mad Science", "Ooo, goo and stinky too",...)

She knows that matter is made of atoms, and that atoms are made of protons and electrons.

I'd like to find some chemistry books that would be appropriate for her. A good book would be one that starts from beginning, help her connect together the stuff she already knows, and then take her further.

My reason is that I don't want school to be too easy for her. I want to nurture her curiosity, love of challenge, and motivation to study.

On the other hand, I don't want to push her even further ahead in the subjects that she has to take in emementary or middle school anyway -- because that would make our dealing with the school system even more complicated... So, I think Chemistry and Physics are good subjects.


texts: Is lithium is less reactive than sodium?

texts: Lithium has most negative electrode potential still its reaction with water is less vigorous than that of sodium


texts: Do all double displacement reactions lead to precipitates?

texts:
I know that most of the double displacement reactions form some kind of precipitates as their products. But do all of the double displacement reactions form precipitates? I have searched on this site as well as on Google, I've found answers, but they are not clarifying my doubts. Maybe I need a simpler explanation.

So, if you answer is yes, they all lead to precipitation, please justify.

If it's no, not all of them give precipitates, please justify with an example.


texts: Why is the oxidation state of carbon in carbon monoxide +2? Why does its dipole moment point from oxygen to carbon?

texts:
Shouldn't it be +3 since 3 of its electrons are being pulled away by the electronegative oxygen?
Also, shouldn't the dipole moment point from the carbon to the oxygen since most of the electron density in this molecule is surrounding the more electronegative oxygen?


texts:
I can't understand the electron count made on this page about Ozonolysis. (http://ursula.chem.yale.edu/~chem220/chem220js/STUDYAIDS/ozonolysis/Oz.html)
This is the specific part of the article:

From my calculations the oxidation of an alkene to an ozonide is a 4 electrons oxidation and not 6e, in fact the two carbons in the double bond loses 2e each from bonding two oxygens.
Anyway I agree with the 4e oxidation from alkene to two carbonyl compounds. Where am I wrong?
Thanks in advance.


texts: Van der Waals nonspecific interaction definition

texts: Every definition I see of Van der Waals interactions claim that they are short-range, nonspecific interactions between two chemical species. What does "nonspecific" mean in this context?


texts: What are unit cells, and how do you determine the number of atoms in one of them?

texts: I've read several websites to try to figure out what exactly a unit cell is, but I can't seem to understand it. Could someone explain what a unit cell is, and the different types? Thanks!


texts:
In chemistry there are ideal models/concepts of ideal crystal, ideal gas and even ideal solution, but there is no model/concept of ideal liquid.

In physics (fluid dynamics, to be precise) there is a model of perfect fluid, a fluid without internal friction and, as a consequence, no viscosity, and thermal conductivity. The model covers macroscale physical properties and doesn't really touch what's happening on the "chemistry level".

Why chemistry lacks a proper model of ideal liquid when a seemingly more complex model of an ideal solution has been developed? Isn't there a need for one, and if so, is there a concept of ideal fluid that comes the closest to be an alternative of, let's say, an ideal gas law, but for liquids?


texts:
I am trying to understand more about the period of vibrational nodes. Currently, I am interested in the wavelength of the $\ce{Si-O}$ bond stretch in silica. I think this value is roughly $1000\mathrm{~cm^{-1}}$.

I am somewhat confused on how to find the period of vibrational modes. I am new to this subject. When I look up the frequency, like I said, I get units of $\mathrm{cm^{-1}}$, but I want units of $\mathrm{s^{-1}}$.

Any pointers on how I can get this value?

Is this the way to calculate it:

$$T = \frac{1}{\nu}$$

where

$$\nu = c \bar{\nu}$$

with $T$, $\nu$, and $\bar{\nu}$ being the period, frequency, and wavenumber respectively?

With this I get:

$$\begin{align}
T &= \frac{1}{c\bar{\nu}} \\
&= \frac{1}{(3 \times 10^{10}\mathrm{~cm~s^{-1}})(1000\mathrm{~cm^{-1}})} \\
&= 33.33\mathrm{~fs}
\end{align}$$

Also, as temperature increases, wouldn't the period decrease? But in the literature, I find that as temperature increases, the wavenumber decreases. Thus, the period increases. Why would the period increase? I would think at a higher temperature, bond stretching would occur more quickly. Is this not the case?


texts: Why is tin-112 stable, but indium-112 radioactive?

texts: According to Wikipedia, tin-112 is a stable nuclide, but indium-112 is radioactive (half-life only 14 minutes). What is the explanation for this?


texts: Reaction analogous to burning that causes cooling rather than releasing heat

texts:
Is it physically and chemically possible to design both a gas and a solid substance, such that there would be a technologically feasible initiation of a chain reaction analogous to the spark that starts a fire, with the unusual feature that the reaction cools the region?
We are familiar with a spark being applied to the surface of a solid surrounded by gas, so that the spark is applied where there are both solid and gas.  Would it be possible to instead start a chain reaction in the gas, with the gas then changing form and affecting the solid?
I acknowledge that I haven't provided any information about the process that initiates the chain reaction, except via the vague analogy with a spark.  For example, perhaps  spraying a liquid catalyst into the gas is what initiates the chain reaction.


texts:
After studying a somewhat overview of "gamma" activity coefficient (it is not actually in our course but may come in exam as a part of unknown paragraph in ionic equilibrium) I can understand most things , but can somebody please just explain in layman's terms (so i can understand it logically, not experimentally) how ionic strength can increase the coefficient and how is distance of approach (lost here) comes into play.

{I am familiar with laplace equations but by only using fourier tricks etc, so, i cant solve any general question with my knowledge}

Are there any more very well known effects only to be understood by activity like
ex- When a 0.1 M hydrochloric acid solution is added to 5 M solution of magnesium chloride, pH decreases — when in fact the acid has been diluted.


texts: Is water committed to vapor state at boiling point or after?

texts:
Quite early into my studies, I learnt about phase changes with this graph.

I’m just going to focus on vaporization/condensation. I learnt that the plateau was caused because all the heat was going into breaking the bonds between the molecules, freeing them from a liquid state to a gaseous state. Thus, no energy was going into raising the kinetic energy of the substance or the temperature.

Later, I learnt about thermodynamics and Gibbs free energy. Spontaneity is dependent on temperature—some processes are spontaneous at some temperatures, and some are not. For a temperature above 100 °C, the boiling of water is spontaneous. For a temperature below 100 °C, the condensation of water is spontaneous. At 100 °C, both states coexist in equilibrium (i.e. $\Delta G = 0$). It is only when you raise/decrease the temperature ever so slightly that water is committed to either state.

I fail to reconcile this with what I learnt. At 100 °C, energy is going into breaking intermolecular bonds. That suggests to me that at 100 °C, water is being committed to vapor. According to the thermodynamic interpretation, at 100 °C, both liquid and gas coexist in equilibrium, and water is not committed to vapor until the temperature exceeds 100 °C.

Can anyone clear up my confusion?


texts: Is this reaction with H+ and OH− a possible reaction?

texts:
I am wondering about the reaction $\ce{H+ + O^2- -> OH-}$. Is it possible?

I think this is not a possible reaction, because here a strong acid plus another particle reacts to a strong base. If it is possible, what would this mean for $\ce{O^2-}$ in the acid-base system? Would it be a very, very strong base?


texts: How do scientist obtain the value of enthalpy of formation?

texts:
Do they do it experimentally or do/can they use bond enthalpy to figure it out? For example $\ce{C2H4 + H2 -> C2H6}$. The enthalpy of formation, $\Delta_fH$ of formation for the product is listed as -84, however if I use bond enthalpy to calculate the $\Delta_fH$, it gives be a value of -222, which is considerably different. Shouldn't the difference between bonds formed and bonds broken account for the heat given off my the reaction? With this discrepancy I can only conclude that I mixed up the two concept.

Also if $\ce{C2H4}$  enthalpy of formation $\Delta_fH$ equals to 52,  $\ce{H2}$ = 0 and $\ce{C2H6}$ = -84, the difference between the product and reactant is -136. I am confused about the 3 numbers (-84, -222 and -136) and their significance.

Also, how is $\Delta_fH^\circ$ different from $\Delta_RH^\circ$ of reaction? When do I use each one?

I would really appreciate it if someone can clear this up concisely


texts: Are graphite intercalation compounds stable in water?

texts:
I want to do an experiment with graphite sulfate, but I want to know if it will de-intercalate in a beaker of distilled water?

Thanks!


texts: Osmium tetroxide reaction with cell membrane

texts:
Background: $\ce{OsO4}$ is a widely used staining agent used in transmission electron microscopy (TEM) to provide contrast to the image. In the staining of the plasma membrane, osmium(VIII) oxide binds phospholipid head regions, thus creating contrast with the neighbouring protoplasm (cytoplasm).The osmium tetroxide molecule is tetrahedral and therefore non-polar. This nonpolarity helps $\ce{OsO4}$ penetrate charged cell membranes.

Question:

What would be the product formed by reaction of $\ce{OsO4}$ with polar head of phospholipid of cell membrane?

My attempt , since $\ce{OsO4}$ is non-polar and phospholipid is polar, therefore it must be some sort of covalent interaction, I couldn't find any literature regarding further at wikipedia.


texts: What is the effect of impurities on ice?

texts: So, I know that the salt dissolves in the thin film of water on the surface of the ice, thus resulting in freezing point depression... but how exactly do i quantify this? Is there any effect on temperature? Will perhaps water be formed? Im tryna think of a way to measure the freezing point depression by adding salt to ice. Thanks in advance.


texts: Why does clearance increase after phenytoin overdose?

texts:
I am finding it hard to envision how an overdose of phenytoin ultimately leads to an increase of the clearance of phenytoin after the enzymes that metabolize phenytoin stop getting saturated.

I know it has to do with zero order and first order kinetics, but I just can't put it in perspective.

Would appreciate if someone could help out.


texts:
Rotation of groups about double bonds are usually restricted due to large torsional strain and it is due to this reason that cis- and trans-isomers have their independent existence. However, certain structural modifications in the compound makes the rotation of groups about double bond possible and hence, for such compound, cis- and trans-isomer exist together in equilibrium.
Identify which of the following compounds has such structural feature and its cis and trans isomers exist together in equilibrium:
(A) $\ce{CH3-CH=CH-CHO}$
(B) $\ce{CH3-CH=CH-CH3}$
(C) $\ce{cyclohexyl-CH=CH-cyclohexyl}$
(D) $\ce{CH3-CH=NH}$

Could someone explain the answer step-by-step and the theory behind it?
I think that rotation of groups about a double bond can be possible due to conjugation of double bonds, so the answer should be (A). But I am afraid I haven't completely understood the logic behind it.


texts: How to differentiate a metal from its ion?

texts:
I am working on metal and its ion. The problem is, I would like to know whether the metal has been converted to its ionic form or not.

The hypothesis for the analysis is that metals are good conductors and ions possess redox potential. Therefore, by measuring the conductance and red-ox potential is it possible to  differentiate whether I have metal or metal ion.

The questions are

Based on the hypothesis, can I expect a positive result?
Apart from this, is there any other technique where I can qualitatively / quantitatively measure  metal and its ion?


texts: Acid-base reaction is screwing up my synthesis

texts:
I'm gonna get kicked all the way to the Moon, but whatever.

I am doing some nitroglycerin. I know the process, since the reaction itself is pretty basic. I know that it is an electrophilic substitution and that it releases a hell lot of energy. I've handled that with an ice bath and by doing the respective stoichiometry. I add around 5 ml of glycerol every 10 minutes.

All of that works great, until I have to do the wash. I've learned how to do washing and extractions from MIT's OCW. Nitroglycerin is insoluble in water, so I require water to wash the mixture and pull out the acid. <- There's the problem. When I'm doing the wash, the temperature rises and a runway reaction begins.

Any advice, besides the usual: "Just… don't"?


texts: Why is acetic acid more acidic than phenol?

texts:
Acetic acid (ethanoic acid, $\mathrm pK_\mathrm a \approx 5$) is more acidic than phenol ($\mathrm pK_\mathrm a \approx 10$), which is reflected in their reactivity with a weak base such as sodium carbonate (adding acetic acid leads to effervescence of carbon dioxide).

However, if we look at the structures of acetate and phenoxide ions, the delocalization of negative charge should be greater in the phenoxide ion as the charge moves inside the benzene ring. On the other hand, in the acetate ion, the negative charge is delocalized between two oxygen atoms only.

How is it possible that acetic acid is still a stronger acid, even when its conjugate base has fewer resonance structures?


texts: First the question gives no units or that these are covalent radii or what, so I assume they are in nanometers and assume an atomic radius. I check my periodic table app and it says a 92pm atomic radius, 75pm covalent and 155pm van der waal for the N atom, which happens to be the first option I crossed out. Now what? BTW, this question is from a previous national aptitude test.


texts:
I wonder, if I wanted to know the molar mass of a some white crystalline solid that is a mix of $\ce{C6H12O6}$ and $\ce{C12H22O11}$, would I just do this :

$$170.1559 \; \ce{g/mol} + 343.2965 \;\ce{g/mol} = 522.4524 \; \ce{g} / 2 \ce{mol}$$

Thus : $261,2262 \; \ce{g/mol}$.

Would this be a correct operation ? Or it wouldn't make any physical sense ? Thank you!


texts: Elimination of HCl from isomeric chlorocyclohexadienes

texts:
Which of these is most easily dehydrohalogenated?

a. 5-Chlorocyclohexa-1,3-diene (1)
b. 3-Chlorocyclohexa-1,4-diene (2)
c. 1-Chlorocyclohexa-1,4-diene (3)
d. Both 1 and 3

I encountered this question a while ago.  The given answer is option (b) (compound 2). But the dehydrohalogenation of compound 1 produces benzene which has high heat of formation. So why isn't that the answer?


texts: Bleaching of chlorophyll stains using hydrogen peroxide

texts:
I have been doing some experiments concerning bleaching of chlorophyll stains from cotton clothing. Currently I have found that $\ce{H2O2}$ is fairly effective, but still leaves visible stains. Would a crude Horseradish root extract containing peroxidase get me better results?

The reason I'm asking about the crude extract and not the purified enzyme is because I don't have access to a laboratory or more complex materials and my work also aims to produce simple methods of chlorophyll degradation that could be replicated at home.


texts: Orange flakes forming after salt water electrolysis with rusty iron electrodes

texts:
I am using two old iron bars, rusty from the years, into a solution of tap water saturated with NaCl.

After a few minutes at 32.6V and between 1 and 2 Ampere, I get a clear looking yellowish solution, containing HOCl (which I am after) along other products.

Invariably, letting the solution sit for a while, either in the electrolysis vat itself, or after having immediately transferred it to another container (via a spigot I installed above the electrodes in the vat, which lay on the bottom of it, so any leakage from the eletrodes themselves should stay on the bottom and I should extract only the "clean" solution above), I notice many orange flakes floating around, that end up sedimenting at the bottom.
After this happens, the yellowish solution becomes mostly transparent.

These are the flakes that form in the external container, where I transfer the electrolysed solution of tap water, NaCl and a touch of vinegar, I seal the top, and put it away from sunlight:

These are the flakes forming in the electrolysis vat, where I left sitting the electrolysed solution of tap water and NaCl (no vinegar added) near the window and with open top (you can see the electrodes submerged to the bottom through a sealed hole on the side)

The flakes do not appear ferromagnetic, they are impalpable (as soon as I try catching them with tweezers they disperse or just float away). I suspect they are iron oxides, but not sure.

I would like to know if such solution is "safe" to be used in a pressure spray painter or if I risk clogging the nozzle.

Also, I would like to know if investing in graphite electrodes will prevent such by-products.


texts:
The Henderson-Hasselbalch approximation gives us a method to approximate the pH of a buffer solution. The basic equation is as follows:
$$\mathrm{pH} \approx \mathrm{p}K_\mathrm{a} + \log\dfrac{\ce{[A^-]}}{\ce{[HA]}}$$

Note that HA is a weak acid. By definition, "HA does not dissociate completely and we can say $\ce{[HA]}\approx\ce{[HA]_i}$ and $\ce{[A−]}\approx\ce{[A−]_i}$. Hence, we can use the initial concentrations because
$\mathrm{p}K_\mathrm{a} + \log\dfrac{\ce{[A^-]_i}}{\ce{[HA]_i}} \approx \mathrm{p}K_\mathrm{a} + \log\dfrac{\ce{[A^-]}}{\ce{[H\!A]}} = \mathrm{pH}$

Source: Chem.Libretexts
Now they have given a question and it's solution as:

Find $\ce{[H+]}$ in a solution $\pu{1.0 M}$ $\ce{HNO2}$ and $\pu{0.225 M}$ $\ce{NaNO2}$ The $K_\mathrm{a}$ for $\ce{HNO2}$ is $5.6\times10^{−4}$.
$\mathrm{pH} = 3.14 + \log \left( \dfrac{1}{0.225} \right)$

So my question is why did they neglect the concenteration of conjugate base from the dissociation of the weak acid and included concentration of the base from the salt?


texts: Changes over time in sodium hydroxide concentration in a hot water bath used for pretzel manufacture

texts:
I make soft pretzels using a hot (190 °F) and dilute (2-4% w/v) sodium hydroxide solution. The bath is kept hot in a open-top stainless steel vessel like a stockpot. I make my pretzel dough and dip the dough in the hot solution for about 20 s prior to baking. As you can imagine, there is a fair amount of evaporation, as well as absorption by the dough of the solution.

Can someone help me theorize what happens to the sodium hydroxide concentration over time? pH is already 14, so pH is not a good measure of concentration. I don’t need to measure precisely, but I would like to understand if concentration is increasing as water evaporates, or if concentration stays the same because the solution is evaporating, or if there is a decrease in concentration by absorption of the pretzel dough.

This will help me understand what I need to do to keep my production going without running out of solution. In other words, do I just add water back to the bath as it evaporates, do I add water and the same concentration of sodium hydroxide I did in the beginning? Or other?


texts: Is it right to compare the molarity of a substance with the probability of its molecules reacting?

texts:
I was watching this video on Khan Academy (about the equilibrium constant), and the analogy that they made really got me thinking. I wanted to verify whether it was completely correct, or just an analogy to explain reaction rates to high school students. I'm well aware that this is an equilibrium constant, and the probability of molecules reacting relates to kinetics. However, this is how it was explained in the video, and I'm trying to make sense of it.

Would anyone please guide me as to whether this analogy, of the molarity and the probability of a molecule reacting, is really true and mathematically correct or whether its just a simplification for students? (I'd recommend that you watch the video first before trying to answer.)

Also, please note that I'm not saying that what Khan Academy is teaching is wrong, I'm just trying to clarify whether what they're teaching is a simplification, or a scientifically accurate explanation.


texts: Why is $\Delta G = -T \Delta S_{\mathrm{total}}$ valid only at constant pressure?

texts:
According to my book(Elements of Physical Chemistry by Atkins and de Paula, 5th ed.), $\Delta G = - T \Delta S_{\mathrm{total}}$ is valid only for constant pressure and temperature.

Enthalpy is defined as $H = U + PV$. So, when pressure and volume both are not constant, $\Delta H = \Delta U + \Delta (PV)$. So, enthalpy can be defined even if the pressure is not constant.

Now the criterion for spontaneity is that $\Delta S_{\mathrm{total}} > 0$. But $$\Delta S_{\mathrm{total}} = \Delta S_{\mathrm{sys}} - \frac{\Delta H}{T}$$ where $T$ is the temperature of the surroundings. Now, if any heat enters the surroundings, the temperature of the surroundings does not change provided that the surroundings are large. I think that due to this the temperature of the system has essentially to be the same or infinitesimally greater/lesser than the surrounding temperature as the heat transfer has to take place reversibly.

But now, as $G = H - TS_{\mathrm{sys}}$, $$\Delta G = \Delta H - T\Delta S_{\mathrm{sys}}.$$

Thus, from comparison of equations, $\Delta G = -T \Delta S_{\mathrm{total}}$. So, I did not need to specify that pressure is constant and why does my book do so?


texts: Name of proton directly bonded to a functional group e.g. carbonyl

texts:
For example, a carbon bonded to a carbonyl group is the alpha carbon, and has alpha protons. Following that there are beta and gamma carbons and protons.
Is there a specific name for the proton in an aldehyde that is bonded to the carbonyl, outside of "aldehyde proton" etc?


texts: Stat Mech: Maxwell-Boltzmann Distribution of Momenta

texts:
I'm trying to show that the MB distribution of scalar momentum that I've found is properly normalized but I'm stuck. My process: I started with the MB distribution of momentum in 2D and found the normalization factor. Then I'm asked to find the distribution for scalar momentum (where only the magnitude of momentum matters) and prove that it's properly normalized. I transformed from Cartesian to polar coordinates and used a 2D Jacobian matrix. The thing is, once I try to prove it's normalized, I get stuck with an expression that goes to zero and I can't find where I went wrong. I'd appreciate any input. Thanks!

MB dust of momentum in 2D, normalized:
$$ f(\textbf{p}) = \frac{\beta}{2\pi m} e^{\frac{-\beta \textbf{p}^2}{2 m}} $$

To find $F(p)$, we integrate over the polar angle and integrate out the angle-dependence.

From Cartesian to polar coordinates:
$$ dp_x dp_y  = det(J)* dp d\theta = p*dp d\theta$$

The probability of finding p between p and p+dp:
$$prob(p,p+dp) = \int_{0}^{2\pi}f(\textbf{p}) p*dp d\theta = 2\pi p \frac{\beta}{2\pi m} e^{\frac{-\beta p^2}{2 m}} dp = p \frac{\beta}{m} e^{\frac{-\beta p^2}{2 m}} dp$$
Therefore,

$$ F(p) = p \frac{\beta}{m} e^{\frac{-\beta p^2}{2 m}}$$

Then to prove F(p) is properly normalized,

$$ 1 = \int_{-\infty}^{\infty} p \frac{\beta}{m} e^{\frac{-\beta p^2}{2 m}} dp $$
$$ = \frac{\beta}{m} \int_{-\infty}^{\infty} p e^{\frac{-\beta p^2}{2 m}} dp $$

but by symmetry,

$$\int_{-\infty}^{\infty} p e^{\frac{-\beta \textbf{p}^2}{2 m}} dp = 0$$


texts:
I am studying solids states.
So we studied different lattices of Ionic solids by introducting smaller Cations into VOIDS.
Next topic is of defects. SO it is written Frankel defect arises when a smaller cation (or anion) shifts from its lattice site to Interstitial site.

Now something is wrong here. I have seen all the threads and topics, didnt find answer to it.
If we have already discussed all kind of Empty spaces as voids (octa, tetra etc), and have already filled them with cations while making ionic crystals, Now where these Interstitial spaces rises from?

Moreover, Cations are already in interstitial site, why they are even shifting to another interstitial site (which technically is already filled with cations, because we made ionic crystals by placing cations into interstitial sites.)


texts: How do I explain the existence of these 2 peaks in this mass spectrometry?

texts:
Question about HRMS:Phosphatidylcholines and phosphatidylethanolamines are common types of glycerophospholipids found in biological membranes. Because of the high amount of heteroatom content, electron impact mass spectrometry is a bad idea because the ions fragment too fast. For biological molecules, electrospray ionization is the most common method. A compound in the glycerophospholipid class was analyzed by low-res electrospray ionization. It produced peaks: 773 Th(100 percent abundance), and 795 Th(about 20% abundance). The question says these are not isotope peaks. The same compound was analyzed by high-rest EI mass-spec to have peaks at 772.5856 Th and 794.5680 Th. The question says to explain the 2 peaks’ presences in the high-resolution mass spectrometry.

For question #6, I came up with the molecular formula for C40H80NO8P for both classes of lipids but I was unsure of how to use that to come up with the actual molecular formula. The first lipid I found was dipalmitoylphosphatidylechloline with a molar weight of 734. But it's smaller than either of the 2 fragments. Then I added 6 methylene groups to come up with a molecular formula of C46H92NO8P. But I'm not sure how to get the molecular formula for both fragments(or if we actually need them). Can you help with this question or let me know of what I'm missing?


texts: How to know whether a molecule is 'stabilized'

texts:
According to a reference book, in acid-base reactions, the position of equilibrium is shifted towards when the conjugate base is more 'stable' and the relative stabilities are compared by

different atoms
resonance
induction
orbital

What I don't understand is that in the first 3 of criteria. They are about how able for the electrons to move around (delocalize). But in the fourth criteria, presence of triple bonds make the molecule most stable since the electrons are confined in a small place (stronger attraction to the nucleus). Doesn't this mean electrons are 'localized' instead of 'delocalized' (i.e. less stable)? Do I get it wrong? Thank you very much.


texts:
In my text book, it is written that $\ce{NH3}$ is a base. They mentioned the reason for this is that it produces $\ce{OH-}$ ions in water. They stated this reaction:

$\ce{NH3 + H2O -> NH4OH}$

So That's why, they said that it is a base.
But in a neutralization reaction, mentioned by our teacher,
Acid + Base = Salt + water
So, if $\ce{NH3}$ is a base then,
it should be,
Acid + $\ce{NH3}$ = Salt + Water
But it does not happen. When reacting with acid, it doesn't produce water.
For example,

$\ce{NH3 + HCl -> NH4Cl}$
--  Reference

Again,

$\ce{NH3 + H2SO4 -> (NH4)2SO4}$
--  Reference

So it is not producing water in the neutralization reaction. Hence, I'm confused whether it is base or not.


texts: Aspartame poisoning: Can it modify aminoacids?

texts: I just accidentally closed a webpage (and did not find it later) which described that somehow, Aspartame poisoning victims had faults in the vital proteins of their body due to the reaction of Aspartame with some aminoacids. I doubted that this is true. However, considering the high solubility of Aspartame in the liquids in the body and its digestibility it is feasible for it or one of the related compounds to be causing this symptom. The info that will be shared is welcome.


texts:
Hepworth, Waring and Waring (2002) mentions that:

  In general, electron-withdrawing substituents make the arene more susceptible to reduction, while the opposite applies for electron-donating substituents.

They then go on to say:

  Methoxybenzene (anisole) is reduced more rapidly than benzene under Birch conditions. This is an exception to the rule, the reasons for which are not clear.

Why is this the case? Does anyone know of any possible explanations?

Source: Wikipedia Commons

Also, I was thinking, since the methoxy group donates electron density mesomerically to the ortho and para positions, wouldn't it be unfavourable for the carbanion to form that the ortho positions? This seems to happen in the mechanism shown above.

Lastly, I understand that the dispute between whether it is "Mechanism O" or "Mechanism M" was settled a while ago but I've read that the evidence pointing to "Mechanism O" seems to be computational studies and experiments. However, there has yet to be any qualitative explanations, based on chemistry principles and concepts, as to why "Mechanism O" is the one which occurs to a greater extent. I was wondering if anyone knows of any such explanations?

Reference

Hepworth, J. D., Waring, D. R., & Waring, M. J. (2002). Aromatic Chemistry. United Kingdom: The Royal Society of Chemistry.


texts: Is there a way to contain fluorine gas for long term so that it can be visually observed?

texts:
Bromine, chlorine and iodine can all be sealed in a glass container for display without the elements reacting with the glass.

But if you try to seal fluorine in glass I believe it will react and fog the surface making it harder to see the gas, right?

What's the best way, if at all possible for long term containment of fluorine for display?


texts: Homemade "milk of magnesia" (suspension of magnesium hydroxide in water)

texts:
I want to make homemade "milk of magnesia" as a suspension containing only magnesium hydroxide and water.
I see that I can purchase a bag of magnesium hydroxide powder. Can I use this to make a suspension or is there a multi-step process?


texts: Which gems can be prepared on a small scale basis?

texts:
I am interested to know the following:

Which gems can be prepared at home (without sophisticated instruments)?
What will be the quality (appearance) of the product for a certain method?

I want these information just for hobby-scale purposes(no academic/commercial production). In addition to common lab equipment, I have $\pu{1000 K}$ of temperature and few atmospheres of pressure at disposal.


texts:
I am quite confused when it comes to this, there are quite a lot of definitions of the above terms in numerous books and websites. However the definitions do not match each other. So, here are the two common definitions of atomic weight

It is the weighted average of the atomic mass of all natural isotopes of a particular element. unit is amu
the number of times the mass of an element is heavier than 1/12th the mass of one atom of carbon 12. it is unit less

Though this question is quite common, please do help me.


texts: Are Tellurium Fluoride or Antimony Fluoride Ionic?

texts: I would like to know if any of the tellurium fluorides or antimony fluorides are ionic.  I am aware that the difference in electronegativity is greater than the 1.665 cutoff indicating ionic bonds.  Melting point and reactivity seem to somewhat support that tellurium(iv) fluoride is ionic but this is not proof. Being an unusual case of an ionic bond between nonmetallic atoms only though, I would like to know if anything empirical (e.g. spectroscopic) has been observed to support this.


texts: Why does pH change with temperature?  I recently read up on some chemistry notes, and found out that the higher the temperature of distilled water, the lower the pH.  Why?  Does this apply to other fluids too?  Does this also mean dipping a litmus paper into 2 beakers of water of different temperature would yield different results?


texts: Resonance structures of some aromatic compounds

texts:
Do compounds like tropolone, furan, and thiophene (which are aromatic) show resonance?

If yes then what are the resonance structures that can be drawn? Also, do all aromatic compounds show resonance?


texts:
For my science classes, I have built multiple types of electrochemical batteries utilizing oxidation-reduction reactions, and I have demonstrated that they each produce potential difference across the different solid metals used using a voltmeter.  Unfortunately, I have been unable to harness any of this to light up a simple lightbulb.

For my first demonstration, I used a copper and zinc strip in vinegar solution.  There was a voltage difference across them of about 0.9V.  This was lower than the 1.1V I was expecting, so I hooked up two of these in series to produce 1.8V.  I attempted to light a simple light bulb (which works perfectly with a 1.5V D battery), but there was nothing.  No current flowed.

For my second demonstration, I made a voltaic pile with cardboard in vinegar, zinc discs, and copper discs.  Again, I had a great voltage prepared (about 3V or so), but I could get no current.

For my latest demonstration, I tried a 1.0M CuSO4 solution with a Cu strip in it connected to a 1.0M ZnSO4 solution with a Zn strip in it via a salt bridge of 0.2M KNO3.  The voltage difference was about 1.1V spot-on, but again, I could get no current to flow through the light bulb.

What could I be doing wrong?  Is there something fundamental I am forgetting here, or is there something perhaps wrong with the items I am using?  My original copper and zinc strips were about 1mm thick, if even that, so I replaced them with thicker strips in later demonstrations, but that did not fix anything.


texts: Balance reaction equation for stabilised PAN cylisation reaction

texts:
I am dealing with polymer chemistry and trying to balance one of these reaction steps. I have read a lot about the cyclisation reaction step but it is not clear to me how to balance these equations or what happens between the first step A) and B1) cyclised form of polyacrylonitril?

By looking at the image and counting the H- and C-atoms, I can tell that polyacrylonitril in the first step has 13 H-atoms (the same amount of C-atoms like the cyclised structure) while the cyclised structure gives 15 H-atoms. Can someone help me to balance or comment on this or what is missing in this part?

P.s.: I know that it is an increasing polymer chain but I just would like to truncate it to this step.


texts: I have a Raspeberry Pi in a small plastic enclosure. The whole thing smells intensely of some chemical I normally associate with burned electronics. It is quite choking. Any ideas what it might be? And is it dangerous? [I do not know the plastics involved -  Straight of the shelf, not powered up]


texts: How might one reduce the concentration of bubbles in their ice, from ice cube trays?

texts:
So I have been freezing ice a lot recently, and I will come out and say it, as it turns out it is, albeit unlikely, it is sometimes possible for ice to "explode." I was not so aware of this before, but from now on I consume my ice beverages with deliberate care.

The first action I have taken is to make sure no bubbles are visibly present before freezing.

I was thinking about how one might reduce these frozen bubbles when making ice with ice trays and a freezer (the bubbles are sometimes a few millimeters across). I was thinking perhaps the bubbles are more likely to form if there are more dissolved minerals and other compounds commonly found in tap water. I think it is time to review osmosis to see if anything will shed light on this idea. My first instinct was to distill water and freeze it to see if there would be less bubbles, but since there will always be dissolved gases even in a freezer it does not follow that this will greatly affect anything.

Is it the case that at lower temperatures water will not be able to hold as many dissolved gases? If that is the case, then it might be worthwhile to lower the temperature of ice in the fridge or to a temperature just above freezing and allow the solution to stabilize, and then put it in the freezer.

Your insight is appreciated, thank you.


texts:
I'm trying to get a sense of how $\ce{Cu^2+}$ and $\ce{NH3}$ are bonded together because it doesn't make any!
I understand that $\ce{NH3}$ has a lone pair of electrons that can be donated (right?), but since there are four molecules of $\ce{NH3}$, then there are 4 pairs, and $\ce{Cu^2+}$ only needs two!
the reaction in my textbook was written like this:
$$\ce{CuSO4.4NH3 <=> [Cu(NH3)4]^2+ + SO4^2-}$$
I would appreciate any clarification.


texts: Multiplicity letter codes for large amount of states

texts:
Well, let's say we have a large amount of states computed (e.g. over 50), all with the same multiplicity.

So, our ground state can be $X^2\Sigma^+_g$ and we can continue with $B^2, C^2$ etc. as described in Molecular orbitals symmetry - states notation and Letter codes in molecular term symbols.

But what is the convention of the number of states is larger, than the number of letters? Does any convention like $B^2_2$ exist?


texts: Relationship between Productivity and Yield

texts:
I am trying to formulate an optimization problem. Can you help me understand the definition of productivity and yield? Why is there a trade-off between them during the reaction?

Thanks in advance.


texts: Reaction of HBr + 2,4-dimethylpent-1,3-diene yields 3 products?

texts:
My understanding is that either pi bond can react with HBr but that you still have to follow Marovnikov's rule or whatever.

I end up with 2 allylic carbocations that are actually the same molecule along with 1 unformed non allylic carbonation. From there there is only one product...


texts: Stereoselectivity differences in Lindlar's catalyst and Na/NH3?

texts: Why does using the Lindlar's catalyst form cis-alkenes whereas $\ce{Na/NH3}$ forms trans-alkenes?


texts:
When reading about making glycerine soap, the recipes suggested to melt animal fat and mix it with $\ce{NaOH}$.

Could I use Sunflower oil instead? Or a olive oil for nice flavor? Is heating necessary in that case?


texts:
Why does the ketone carbonyl group react in preference to the ester carbonyl?

Is it something to do with the resonance occurring into the ester carbonyl from the oxygen? but how does this make the ketone carbonyl more likely to form the ketal when reacted with a diol and non aqueous acid?


texts: Why does moving from left to right on the periodic table result in higher conductivity?

texts: Question is in the title. I understand that the metals towards the left form stronger bonds with other chemicals compared to metals towards the right, and that the ones with weaker bonds break down easier and pass more current. (if that's wrong, please correct me) Why is this the case? Could someone please explain this concept to me more?


texts: Relation between rate of adsorption and the critical temperature of a gas

texts:
How is the rate of adsorption related to the critical temperature of a gas? My textbook says more the critical temperature, better are they adsorbed. But I cannot really understand why. They threw in another confusing statement that says that easily liquefiable gases are readily adsorbed. I am thoroughly confused.

I did read the question How does critical temperature affect adsorption? before posting this question, and while that question was answered, it did not answer my question fully.

Edit: To clarify my area of doubt, let me say what I find confusing. Gases with lower Ct will 'prefer' the gaseous phase over the liquid phase. Which is what we want. We want gases to be adsorbed.


texts: What is density in density functional theory?

texts:
This may be dumb question. Please bear with me.

Density functional theory (DFT) is a successful theory for electronic structure calculations of materials. In DFT, electron density is the fundamental variable that is proven by the Hohenberg-Kohn theorems. However, I find it difficult to understand how density is used to calculate the energy of the system.

In general, number of electrons per volume will provide the electron density. Okay. Now, I consider Hydrogen atom (for simplicity). If I calculate the electron density, in fact, it depends on how much volume is chosen. If I chose a unit volume, its charge density is 1e. If I double the volume, the charge density halves ($\frac{1}{2}e$). What decides this volume? How to chose this volume?


texts: Are buckminsterfullerene-corannulene complexes actually stabilised by π stacking?

texts:
According to wikipedia and the references given therein, $\pi\cdots\pi$ stacking interactions are the result of interaction between the quadrupole moments of two aromatic rings, rationalising the stabilisation of perpendicular and offset-parallel association modes of the benzene dimer.

Conventional wisdom is that the supramolecular complexes of buckminsterfullerene and functionalised corannulenes (the so-called buckycatchers) are stabilised by $\pi\cdots\pi$ stacking. How can the quadrupole interaction explanation be reconciled with the pseudo-spherical symmetry of buckminsterfullerene? Surely the interaction must be entirely Van der Waals in nature?


texts: Rust removal ended with black oxide on the metal?

texts:
I have tried to remove common red iron rust from a small piece of metal that looks like steel.

I submerged it into hot water with a bit of citric acid, and let it sit overnight. In the morning I have no rust, but the thing is now covered in dark-black oxide.

Was that possibly steel that I was cleaning or something else? How do I remove that black oxide?

How should remove rust in situations like this in the future?!

left - piece from the same metal that has no rust, and was not cleaned, right - piece that was cleaned


texts: Yellow precipitate in the presence of ammonium molybdate?

texts:
We had analytical chemistry experiments to determine acidic radicals from a mixture of two salts. After the chloroform-chlorine water test for distinction between halides $(\ce{salt\ solution + H2SO4 + CHCl3 + Cl2_{(aq)}})$ when I emptied the test-tube in the sink, all of it suddenly turned yellow.

What reaction could have occurred to cause this?
The sink mostly contained diluted $\ce{H2SO4}$ and $\ce{HNO3}$ along with small quantities of $\ce{AgNO3, BaCl2, NH4OH}$, lead acetate and ammonium molybdate.

All of these would mostly be in small quantities since I had rinsed the sink with water before emptying the test-tube.


texts: Finding Pv in Pv=nRT for molecular hydrogen

texts:
I'm attempting to write a small program that will calculate the values for the Ideal Gas Law, specifically for molecular Hydrogen (H2) in space.  Eventually, this will grow to be a sort of "simulator", but right now I seem to be having problems with remembering my college chemistry and physics.

Here is a picture of the form that I created:

So in my program (written in C#), I have the following as initial values for those variables:

        P = ?
        v = ?
        n = 2.0158 (weight in grams of H2)
        T = 2.725 (average temp in space)
        R = 1.67E-27 (1.67 * 10^-27)

My problem is that, how does one go about trying to solve for P or v?  Do you assign an arbitrary number for what you suppose the volume of the gas would be in space, and then calculate P based on that?  Or is it the other way around?

Extra, yet entirely unneeded info:
This was brought about because my 7 year old daughter asked me how stars were made.  I gave her the explanation that anyone who's got even a remote interest in it gives to their kids, but thought it would be pretty cool to make a little program that would give her a visual.  Here was my explanation:

  "we think that Hydrogen stuck together to make even larger clouds of
  Hydrogen, which increased the total mass of the gas cloud, increasing
  the gravitational pull on other atoms/molecules of nearby gas, etc.
  This eventually got to the point that the gases started to heat up as
  they were squished together by their own mass, but that increase in
  temperature created an outward push (pressure), which got into a
  tug-of-war with gravity acting on the mass of the gas itself.  And
  later, we got a star.  That's how most of us non-scientists think it
  happens, anyway!"


texts: Determining number of electrons transferred

texts:
When determining the number of electrons transferred in a redox reaction is it the total in both half equations?

For example:

$$\ce{2I- + Zn^2+ -> I2 + Zn}$$

First we split it up into the two half-reactions and get the following

$$\ce{2I -> I2 + 2e-}$$

$$\ce{Zn^2+ + 2e- -> Zn}$$

So would the number of electrons transferred in the redox reaction be two or four?


texts:
I am interested in learning how to oxidize tantalum. I have seen some tantalum rings that the sellers say is a permanent smokey blackish color. But I've spoken to some people that say tantalum cannot be oxidized, and the rings I saw must have been coated.

So anyone know if and how tantalum can be oxidized?


texts:
Double Bond Equivalent/Degree of Unsaturation

  25. Degree of unsaturation in

  is

  (a) 6; (b) 7; (c) 8.

There are two rings and six double bonds in structure so degree of unsaturation should be 8, but it is not. Why?


texts: How does a combustion process produce carbon monoxide?

texts:
My question is in the context of combustion heater safety- I want to identify the mechanism by which CO is produced, and hopefully have additional understanding, and clues to the warning signs, to identify unsafe stoves or installations. The primary safety measures will always be CO detectors and good ventilation.

The worst horror stories usually concern charcoal barbecues in confined spaces- solid carbon burning at about 900 °C. Is it a safe educated guess that the main combustion product here is CO, which fails to burn fully to CO2 in depleted oxygen levels? Or is a more complex process at work?

How does the yellow combustion of an oil or gas flame produce CO? Is it a simple matter of poor gas flow in the flue, and depleted oxygen in the feed air?

Thanks for any help


texts:
Compound X has 3 carbon atoms in one molecule. It contains a primary alcohol and a carboxylic acid functional group.

Draw the displayed formula of Compound X.

Help! Condensed formula is fine for me!


texts: Alkene production by dehydrohalogenation

texts: What is the difference in the reaction mechanism when alkyl halides are reacted with aq.koh and alcoholic koh along with products


texts: Ea is the term for activation energy, what is the mean of a in this term?

texts: Our doctor said it is not stand for activation. it stands for something else, any help will be appreciated.


texts: Why hyperconjugation can't stabilize carbanion?

texts: If Resonance can stabilize both carbo cation and anion then why can't hyperconjugation stabilize carbanion ? Since both Resonance and Hyperconjugation are pretty much the same, i.e both involve delocalisation or diffusion of electrons( at least in model) ?


texts: Why hybridization occurs in diatomic molecule

texts:
In diatomic nitrogen
There are two electron configurations I'd like to compare:

1s2 2s2(lone pair) 2p3(the bonding electrons sigma,pi,pi)
1s2 2sp(lone pair) 2sp(sigma bonding) 2p2(pi,pi bonding)

Why is option 2 favored over option 1?
I thought having the lone pair in a 2s orbital would be favored over 2sp.


texts: How to neutralize the stink of decomposed fish?

texts:
Recently I discovered for myself an interesting way to easily produce home made plant fertilizer that is quite effective (tested myself on the plants). It's fish emulsion (so can be used also in a hydroponic system) - 1 part fish wastes(skin/bowels) to 2 parts water placed in an airtight container in a sunny spot for ca. 1-2 weeks. The problem - it stinks unbearably. Both - the gas that is produced during the decomposition and the liquid(/fats).

Is it possible to neutralize the stench somehow without loosing the fertilizing qualities of the emulsion? Especially of phosphorus.
1.1 Ideally of both - the gas and the liquid. But at least of the liquid - as that is what is used actually and then continues to spread the smell after being added to the plants.
1.2 Ideally it should be done using some usual household substances/wastes - maybe adding of lemon/orange peels along with the fish wastes? Or maybe ash/charcoals?

Ideally the resulting emulsion should be acidic as many plants like the pH range of 5 - 6.5 .


texts: Why is nylon durable and how does it have such exceptional strength?

texts: I was wondering how the chemical composition of a synthetic polymer such as nylon results in strength and durability.


texts: Why are rates of reaction faster for ionic compounds than for covalent compounds?

texts: Why is it that ionic reactions (i.e., reactions involving ionic compounds) are faster than covalent reactions (reactions involving covalent compounds), even though the ionic bond is stronger than the covalent bond and hence more time will be required to break the bond?


texts: Why are these two methods of converting from ppm to g/m3 equivalent?

texts:
I've found two methods to convert from $ppm$ to $g/m^3$. They both appear to give equivalent results, but I don't understand why. Can anyone join the dots for me and explain why they are equivalent methods, or show a derivation for Method 1? I've found a derivation for Method 2.
Method 1 - Definition
$$C[g/m^3] = \frac{C[ppm] \cdot \rho}{1000}$$
Where $C[ppm]$ and $C[g/m^3]$ represent gas concentration in units of $ppm$ and $g/m^3$ respectively and $\rho$ represents gas density.
Method 2 - Definition (As derived here)
$$C[g/m^3] = \frac{C[ppm] \cdot M \cdot P}{R \cdot T \cdot 10^6}$$
Where $M$, $P$, $R$ and $T$ represent molar mass, pressure, ideal gas constant and temperature respectively.
Method 1 - Example - Carbon Monoxide (CO)
Assuming $C[ppm]$ as $100ppm$ and CO density as $1.15 kg/m^3$ at $20^{\circ}C$ and $100000Pa$
$$C[g/m^3] = \frac{C[ppm] \cdot \rho}{1000}$$
$$C[g/m^3] = \frac{100 \cdot 1.15}{1000}$$
$$C[g/m^3] = 0.115$$
Method 2 - Example - Carbon Monoxide (CO)
Assuming $C[ppm]$ as $100ppm$ at $20^{\circ}C$ and $100000Pa$.
$$C[g/m^3] = \frac{C[ppm] \cdot M \cdot P}{R \cdot T \cdot 10^6}$$
$$C[g/m^3] = \frac{100 \cdot 28 \cdot 100000}{8.3145 \cdot (20+273.15) \cdot 10^6}$$
$$C[g/m^3] = 0.115$$


texts: How to draw the 2D representation of ammonia molecule

texts:
In the 2D representation of the ammonia molecule, we see one solid line, one solid triangle and one dashed triangle

A plane can be made to pass through any three given points. In other words, we can always find a plane which will pass through any three given points in space. So the central N atom and two H atoms will lie in a plane. Only one H will be out of plane. So I think, in the 2D representation, we need to show two solid lines and one solid triangle. Please give your opinion about this. Thanks


texts: Regarding the use of dilute sulphuric acid in this titration

texts:
I did a titration today for the first time.
A solution of Potassium Permanganate of unknown molarity was titrated against a solution of ammonium iron II sulphate of known molarity.
I have to say, seeing the purple solution turn clear was a lot of fun.
Dilute sulphuric acid solution was used twice during this experiment. First to prepare the ammonium iron II sulphate and sulphuric acid solution, and then 20 ml was added to each sample before titration.
Why did these have to be added ?
Also, could I have used pure sulphuric acid ? Why did it have to be diluted ?
I think the first usage provided the H+ for the reaction to occur but I am not sure. Would pure sulphuric acid not be more efficient ?


texts: Liquid floating on top of water due to density or insolubility?

texts: When a liquid is floating on top of water, how can one tell whether it is because of its insolubility in water or because it has lower density than water?


texts: Why was silver considered valuable in history?

texts:
Silver has been used for several millenia and (according to the german wikipedia page) was at some point even considered more valuable than gold. Today we know that it has the highest thermal conductivity and so on but these things were not known to the people back then.

What property made ancient civilizations agree that silver is something valuable compared to other metals like tin, gold or copper which were also known in the early days of humanity? Was is just rarity? Ductility? The ability to be polished? I assume that it was not just corrosion resistance as polished silver becomes dark rather quick.


texts: How to find out which organic molecules would be good electron acceptors/donors on a GaAs semiconductor surface

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I'm a physicist in way over my head.
I have a list of organic molecules to investigate, all common aldehydes and amines. My supervisor wishes to know which of these molecules would be good electron donors and which would be good electron acceptors.

The idea is to use some of these molecules to dope some GaAs nanowires, in order to be able to tweak the Fermi level at the edge states. What are the properties I should be looking for? I am guessing that compounds with very electronegative elemental constituents will be good electron acceptors and vice versa for those with electropositive constituents but other than that I am unsure where to find the information I need. Could anybody point me in a helpful direction?

Some one else mentioned electron affinities and ionisation potential but I have no idea where to look for these things in the literature. My chemical understanding is limited to what I know about physics and advanced high school chemistry.


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For part a) I don't really know what to look at. Diffusion occurs from low to high concentrations so by looking at $t_1$ I would say that the direction of the mass transfer is from phase II (organic phase) to phase I (aqueous phase) since the organic phase starts at a lower concentration than the aqueous phase.

But apparently it is supposed to be the opposite. And the answer is the same at $t_2$.

Could anyone please explain how to determine the direction of the mass transfer and how it can be the same at $t_1$ and $t_2$. Thank you!


texts: If double and triple bonds are stronger than single bonds then why are unsaturated hydrocarbons less stable than saturated hydrocarbons?

texts: I have learnt that unsaturated hydrocarbons are more reactive and less stable.  However if double and triple bonds are stronger and shorter bonds than single bonds, aren't they supposed to be more stable and inert?


texts: Is there a replacement for glacial acetic acid in determining peroxide value

texts: I am not allowed to use glacial acetic acid at my school, which all procedures online for finding the peroxide value of oils use through an iodometric titration. Is there a replacement?