texts: When using a "dilute hydrochloric acid" solution, how diluted should it be?

texts:
Quite often when reading through some instructions or documentation or an outline that I've found online (EG: acid-base extractions), theres a step that involves using a "dilute hydrochloric acid solution", but oddly enough, it often doesn't detail exactly how diluted the HCl should be. Heres one example (little past half way into the 3rd paragraph)

  Dilute hydrochloric acid is often used in the extraction of basic substances from mixtures or in the removal of basic impurities. The dilute acid converts the base such as ammonia or an organic amine into water soluble chloride salt.

So my question is: How does one know exactly how diluted the HCl should be? Is there a commonly used concentrated amount of HCl that I just don't know about? Sometimes it'll suggest using Muriatic acid instead, which I believe is basically 31.45% concentrated HCl, is that a commonly used concentration?


texts:
Is there good databases for Gibbs energy and other thermal properties? NIST WebBook is okay but easier to browse most common chemical elements like hydrogen, water, oxygen and so on in a table or interactive?
Thanks in advance.


texts: One half of a nail is exposed to vinegar. Un-exposed half develops a brown film. What is it?

texts:
I have recently done an experiment for my chemistry EEI (Year 12) where we are testing what factors effect the rate of corrosion. I used vinegar (acetic acid) as one of the acids and Hydrochloric acid as the other.

In the one with the HCl, the results were as expected – the area exposed to the acid will corrode, the unexposed part won't (in the time frame I did).

However, for the vinegar, the results were different. The part exposed to the vinegar didn't show any rust however the part of it that wasn't exposed had a brown coating. Now I understand that the vinegar reacts with the rust, hence the reason we cant see it on the iron nail, but my question is: What is the brown coating on the top of the nail, and what is it caused from? Was there some sort of gas from the vinegar that caused it? If so, what is this gas called and how does it cause corrosion?


texts: Why cyclic glucose is not a heterocyclic compounds if it consist Oxygen as a Heteroatom ?


texts: I don't think it follows the $4n + 2$ rule. The double bonds give 8 π electrons. Then the lone pairs on the $\ce{NH}$ and $\ce{NH2}$ groups are delocalized (are they?) so they must contribute 4 π electrons. Thus in total there are 12 π electrons, which doesn't follow Hückel's rule. So, why is it aromatic?


texts: Amount of substance expressed in yoctomole units

texts:
I stumbled upon a couple of papers where amounts were expressed in yoctomoles ([ymol], $\pu{10^{-24} mol}$) and I find it somewhat bothersome as 1 ymol would correspond to about 60% of atom/molecule/ion etc., which doesn't make much sense to me:

$$N_\mathrm{A} \times \pu{10^{-24} mol} = \pu{6.022 \times 10^{23} mol-1} \times \pu{10^{-24} mol} \approx \pu{0.6}\,\text{(elementary entities)}$$

Simply put, I'd say that using zeptomoles ([zmol], $\pu{10^{-21} mol}$) is already a stretch as one of the ideas behind a mole concept is to allow to handle large numbers of entities more conveniently, and at this scale there is no reason not to use direct quantities of molecules/atoms/ions.

Should the yoctomoles units really be used, and if so, then how to rationalize fractional elementary entities?


texts: Why is sodium methanethiolate still a better nucleophile than sodium methoxide when the solvent is ethanol

texts:
I'm looking at a problem where sodium methanethiolate and sodium methoxide, both in equal amounts, are being reacted with $\ce{CH3I}$ and the solvent is ethanol.

I understand that sodium methanethiolate is a better nucleophile than sodium methoxide when the two are reacted in equal amounts with something like methyl iodide in a polar aprotic solvent. But why is sodium methanethiolate still a better nucleophile than sodium methoxide when the solvent is polar protic, like ethanol?

I thought the ethanol would reduce the nucleophilicity of both, but would do so at by different amounts, given the different electronegativity of sulfur and oxygen. If ethanol reduces the nucleophilicity of both at the same rate, why even use ethanol as a solvent in this case?


texts: rust caused by salt solution & stainless steel

texts:
I am not a chemist and I could really use some help for a practical case.
I am fermenting vegetables (cabbage, onions, carrots, etc.). I recently switched from glass and ceramic vessels to stainless steel 304 ones (100L capacity). At the moment, I am only filling the vessels half-way, i.e. 50/60L and using a variable lid system. The vessel is airtight thanks to a plastic band around the lid, which is then placed right on top of the vegetables (it is a stainless steel lid and the plastic band around it is then pumped with air to compress it against the vessel). The lid also has an airlock system in the middle, allowing the co2 generated during the fermentation process to be pushed out. The brine created during the fermentation process also gets pushed out from that airlock (when the vegetables are put in the vessel, about 2% salt is added, so the brine contains salt). The brine ends up covering the lid and I removed it from time to time. It is not overflowing on the plastic band from the outside, but it seems that the brine is also pushed up against the plastic band and gets in between the plastic band and the vessel. After a few days, no more brine gets out.
At the end of the fermentation (after 4-5 weeks), when I removed the lid and emptied the fermentation vessel, I discovered traces of rust on the inside. It is right where the plastic sealed the vessel. It's not only rust, but the surface (or coating) of the stainless steel was even removed in some parts. There is no rust below or above that line (ie where the plastic sealed the vessel).
I am aware that stainless steel 304 is for sure not 100% rust-resistant but I was definitely not expecting such reaction after 1 usage! What a powerful brine...
My question is whether you believe that this reaction is due to the brine pushed up? Probably small amounts of brine end up getting stuck between the plastic and the vessel and thus potentially slightly exposed to air.
If that's the cause, I have two fixes in mind :

put the lid higher in the vessel so that the brine is not pushed up against the plastic/lid. I believe that the CO2 created should be sufficient to push out all the air below the lid.

continue to place the lid right above the vegetables. Once no more brine is pushed out, remove the lid to clean the hedges. Then put the lid back. I believe that the remaining fermentation process should push out the newly added air while not generating sufficient pressure to push new brine out.

I also came across another possible explanation while browsing full link

The same thing can happen at the water’s surface if the container is only half full. In this case, the steel above the waterline is exposed only to air, and the passive oxide layer is stable. Beneath the surface, the oxide layer is at a different potential and less stable because of the chloride ions. Now the crevice is represented by the waterline: stable area above, less stable but very large area below, and crevice corrosion occurs at the waterline. Usually this type of corrosion manifests as pitting or pinholes. The mechanism described is accelerated by localization, so a pit is most often the result.

Some pictures
1)the vessel
2)the rusted line / removed steel on the inside of the vessel
3)the lid on which the plastic band is then mounted
What do you think ?


texts:
Why does Butane burn blue? From my (very) basic understanding of chemistry, carbon and hydrogen do not burn blue, their radiation spectra are different-so why should the combination burn blue?
Please elaborate as much as possible, about bonds, orbitals, electrons, and the like!


texts: Find mass of CO₂ and heat released per minute in a combustion reaction

texts:
I am not sure where to start with this problem. I know that $\small q = mc(T_f-T_i)$, but that seems like it would not help here. I think I need to balance the equation, but I am not sure how the rate factors into the problem. Anyway, if anyone could help me find the relevant equations/method for solving this problem, it would be greatly appreciated:

A natural gas mixture is burned in a furnace at a power-generating station at a rate of 13.0 mol per minute.

If the fuel consists of 9.3 mole $\small\ce{CH4}$, 3.1 mole $\small\ce{C2H6}$, 0.40 mol $\small\ce{C3H8}$, and 0.20 mole $\small\ce{C4H10}$, what mass of $\small\ce{CO2} (g)$ is produced per minute?
How much heat is released per minute?


texts: Why is Cr²⁺ is a good reducing agent but Mn³⁺ is a good oxidising agent?

texts:
The question is the same as the title states. In my textbook,[NCERT Chemistry I for Class 12 , pg no 217.] the following is written

$\ce{Cr^{2+}}$ gets converted to $\ce{Cr^{3+}}$ as the +3 oxidation state has half-filled $\mathrm{t_{2g}}$ orbitals; thus it is a good reducing agent.
On the other hand $\ce{Mn^{3+}}$ gets converted to $\ce{Mn^{2+}}$ as its +2 oxidation state has a half-filled d-subshell.

Now my questions are:

Why can't the $\mathrm{t_{2g}}$ argument be used for $\ce{Mn}$?

Why can't the half-filled $\mathrm{d}$-orbital argument be used for $\ce{Cr}$?

$\ce{Mn^3+}$ could be oxidized to $\ce{Mn^4+}$, which would have a half-filled $\mathrm{t_{2g}}$ set. As oxidation and reduction both can take place in aqueous medium, why wouldn't $\mathrm{t_{2g}^3}$ or $\mathrm{d^3}$ configuration be more stable than $\mathrm{d^5}$ configuration in aqueous medium?
A similar observation is made in case of $\ce{Fe^2+}$ and $\ce{Cr^2+}$, where it observed that $\ce{Cr^2+}$ is more powerful reducing agent than $\ce{Fe^2+}$ (due to reasons explained above).
If possible, I would like to see the crystal field splitting calculations that show this to be the case.


texts: How/where can I find a reliable atomic radii table?

texts:
I am currently working on a periodic table to include it in a experimental chemistry book and I would like to include non-bonded atomic radii data so it would be easier for the students to learn about periodic trends and quickly determine if an atom is more likely to produce a hard or a soft Lewis acid-base.

The problem is that every reference I looked have different values for the same atom. For instance, see the results for Hydrogen and Gold non-bonded atomic radii below:

In this site we have: 0.53 (H) / 1.74 (Au) Å
In RSC site, we have: 0.32 (H) / 1.30 (Au) Å
This aricle (Slater, 1964 - see the DOI below): 0.25 (H) / 1.35 (Au) Å
Finally, in Wikipedia (which is the result Google will return if you type the search query "hydrogen/gold atomic radius") is: 0.53 (H) / 1.66 (Au) Å

These differences are observed in most elements. I do not know which one is more reliable. In my point of view, variations of 0.20 angstrons are too big in atomic scale, aren't they?

What do you think about what cause those variations? Are they significant? Could someone help me to find a reliable source for atomic radii data?

Maybe those variations occur due to statistical deviations from the method used to measure them, but could it be so big (about 20%)?

Thanks!

Slater, 1964. DOI: 10.1063/1.1725697


texts: When MgCl₂ · nH₂O is heated to the boiling point of H₂O

texts: When magnesium chloride hydrate is heated, does $\ce{Mg(OH)2}$ form or what? I'm curious, because Wikipedia says that it decomposes to release $\ce{HCl}$ gas.


texts:
Most elements are or have compounds that are gases or have a significant vapor pressure at room temperature. Fluoride is a powerful tool for producing highly oxidized covalent and volatile compounds. Tungsten hexafluoride is gaseous at room temperature despite being made with the element with the highest melting and boiling point. Refractory elements can also have volatile oxides such as $\ce{CO2}.$

Organometallics such as iron pentacarbonyl and dimethyl zinc are liquids at room temperature but have a decent vapor pressure, boiling at 103 °C and 46 °C, respectively. Other examples of "volatilized elements" include diborane and heaver analogous of ammonia such as phosphine.

All of the compounds I found of alkali metals, however, have very low vapor pressures at room temperature. For example, organolithium compounds tend to form lithium clusters or ionic crystals and decompose into lithium hydride when heated (which isn't volatile), rather then the covalent examples previously. Alkaline earth organometalics seem to suffer a similar problem with dimethylmagnesium forming a solid lattice.

Are there any known examples of an alkali metal compounds that has a reasonable vapor pressure, say 100 Pa at 300 K?


texts:
According to the Wikipedia article Triple point of water, the triple point of water occurs at

  The single combination of pressure and temperature at which liquid water, solid ice, and water vapor can coexist in a stable equilibrium occurs at exactly 273.16 K (0.01 °C; 32.02 °F) and a partial vapor pressure of 611.657 pascals (6.11657 mbar; 0.00603659 atm).

Shown in the illustration below (from the Wikipedia article):

Crucially, to put this into a context, the 611.73 pascals quoted in the article corresponds to the

  minimum pressure at which liquid water can exist. At pressures below the triple point (as in outer space), solid ice when heated at constant pressure is converted directly into water vapor in a process known as sublimation.

Potentially useful information to determine if an exoplanet can possibly have water (if all other conditions are suitable).

What are the spectroscopic signatures that differentiate triple state water from water at 1 atm?


texts: Find the final temperature and volume of the gas

texts:
$\pu{10 L}$ of a monoatomic ideal gas at $\pu{0 ^\circ C}$ and $\pu{10 atm}$ pressure is suddenly released to $\pu{1 atm}$ pressure and the gas expands adiabatically against this constant pressure. What are the final temperature and volume of the gas? (Answer: $\pu{174.9 K}$, $\pu{64.04 L}$)

There are some points I don't get:

First of all, it is not given whether it is reversible of irreversible expansion.
If it is reversible, I am at wits end deciding whether to use one of the following (without success):
$$ pV^\gamma = \mathrm{constant} \quad \mathrm{or} \quad T^\gamma p^{1 - \gamma} = \mathrm{constant}$$
If it is irreversible, I tried using
$$W_\mathrm{irreversible} = \Delta E$$
i.e.
$$-P_{ext} \left(\frac{nrT_2}{p_2} - \frac{nrT_1}{p_1}\right) = nC_\mathrm{v}\Delta T$$
I am having trouble using $r = \pu{0.0821 L atm mol-1 K-1}$ and $R = \pu{8.314 J mol-1 K-1}$.


texts: Formation of complexes by ferric ions is more frequent than ferrous ions. Why?

texts: Looking at the electronic configurations of ferrous and ferric ions they are d6 and d5 systems respectively. Hence, ferric ions are more stable. But in octahedral complexes like hexathiocyanates, the electron count of ferric ions reaches only 17 while for ferrous it reaches 18. In the case of thiocyanate , ferric complexes with the ligands while ferrous does not react at all.


texts: What are B and n in this expression for charge repulsion?

texts:
In a study of the creation of ionic bonds of in this case $\ce{Na}^+$ and $\ce{Cl}^-$ into $\ce{NaCl}$, I have come across this equation for the overall energy of the system:

$$E=-\frac{e^2}{4\pi\epsilon_0 R}+\frac{B}{R^n}+1.4 \,\mathrm{eV}$$

$e$: electron charge. $\epsilon_0$: vacuum permittivity. $R$: the distance between them.

The first term is the attraction energy between the two equal but oppositely charged ions $\ce{Na}^+$ and $\ce{Cl}^-$.
The second term is the repulsion between the like charges within the shells. When the distance $R$ is very small, this term has large (opposite) effect.
The last term is the difference in free creation energy for the two free reactions ($\ce{Na \rightarrow Na^+ + e^-}$ requires $+5.1\,\mathrm{eV}$ and $\ce{Cl + e^- \rightarrow Cl^-}$ gives $-3.7\,\mathrm{eV}$)

My question is two-fold and about the repulsion energy term: What is $B$? And what is $n$? I have been told that the exponent is around $n \approx 10$, but is this a general constant or material specific?


texts:
I read the wiki
https://en.wikipedia.org/wiki/Dilution_refrigerator
And my interpretation is that you get one cold liquid(helium 3) and add it to another (helium 4). The molecules of the liquids diffuse and this process requires energy so the mixture gets colder. I understand this so far. The twist is that as the temperature drops, the liquids become somewhat immiscible so they separate into two phases - an almost pure helium 3 phase (the concentrated phase) and a helium 4 phase ( made of 6% helium 3 and 94% helium 4)
The wiki then says
‘ Inside the chamber, the helium 3 is diluted as it flows from the concentrated phase through the phase boundary into the dilute phase. ‘
Why would one phase flow through another and why don’t they just layer out?
And also (if I am permitted to ask another question and further reveal my ignorance) when the phase separation occurs, doesn’t one phase recapture the energy it lost through mixing in the first place? It seems from the drawings that helium 3 mixes, gets colder, then separates and then is funneled away by a pump. Why isn’t its temperature when it gets funneled away the same as its temperature when it is added to the mixing chamber?


texts: Do we know what is the wavelength of the color of pheomelanin?


texts: Is lithium bicarbonate an aqueous solution of lithium carbonate?

texts:
This question is related to:

Are Lithium bicarbonate and Magnesium bicarbonate both soluble in water?
What type of chemical reaction is this?
How can bromine water be called a solution?

In the first question, the page from JD Lee (Concise Inorganic Chemistry 5 ed) states:

  Lithium is exceptional that it does not form that it does not form a solid bicarbonate, though $\ce{LiHCO3}$ exists in solution. All the carbonates and bicarbonate are soluble in water.

and then in the sideline(the most important line):

  If it exists in water, it must definitely be soluble in water.

Now, Lithium carbonate is prepared by bubbling $\ce{CO2}$ gas to a solution of lithium hydroxide, $\ce{LiOH}$.(source)

$$\ce{2LiOH + CO2 → (Li2CO3 + H2O)}$$

But in another source (endmemo), it shows that lithium hydroxide and carbon dioxide directly combines to form lithium bicarbonate.

$$\ce{LiOH + CO2 -> LiHCO3}$$

So, basically lithium bicarbonate is aqueous solution of lithium carbonate. Isn't it?

Now, what I gather from the fact that lithium carbonate is soluble in water and form a solution where the components do not react with each other. However, when the two reaction are compared, we observe that lithium carbonate reacts with water to form lithium bicarbonate. It seems contradictory with the above statement. How is this possible?

In the 3rd question, I said that if bromine reacts with water to form a mixture of acids, how can it be called a solution? Components of solution do not react with each other. Same case goes on with this reaction. If lithium carbonate is in aqueous solution, it should dissociate into component ions i.e $\ce{Li+}$ and $\ce{CO3^2-}$ but instead it goes on form $\ce{LiHCO3}$ and thus the solution has $\ce{Li+}$ and $\ce{HCO3-}$ ions. Why?


texts: Flammability (NFPA) - how is it defined?

texts:
I was reading up on a wonderful little chemical compound known as chlorine trifluoride ($\ce{ClF3}$). For a primer, check out Dr. Derek Lowe's blog post here: Sand Won't Save You This Time. The title of the post is quite telling; this compound is so reactive with other compounds - any other compound, really - that it will set sand on fire, making this old standby for extinguishing lab fires useless and putting the chemical in very rare company indeed. Obviously, water is a huge no-no for chlorine trifluoride; it will exothermically react with the water to produce clouds of steam containing two nasty acids (hydrochloric and hydrofluoric) and a host of chlorate and fluoride compounds. Somewhere in the middle of all the heat, fluorine and organic-ish compounds, you could probably even get some fluorine oxides, which would just LOVE to rapidly reduce their oxidation state (an event normally accompanied by shrapnel).

I was intrigued; I went and looked up the MSDS for this chemical to see what the instructions were for dealing with industrial spills of this stuff (apparently, there's a decent market for it in the semiconductor industry, and probably also for plastics to produce highly fluorinated polymers like Teflon). "A good pair of running shoes" can't be the only answer to a $\ce{ClF3}$ fire. (well, actually, it pretty much is; get everyone in a one mile radius and two miles downwind the hell away from the area)

Now, here's the question. While this stuff has some serious "synergy" when it comes to being an oxidizing agent (it's a better oxidizer than pure oxygen, loads better than pure chlorine, better even than pure fluorine gas), the NFPA flammability rating of the chemical is 0. This, despite reports from those who originally studied it that the chemical is hypergolic with every known fuel substance, and most things you wouldn't consider fuel (like asbestos, sand, concrete, brick, earth, test engineers). The resulting reaction certainly looks like fire; intense heat, bright light, sparks, smoke, the works. So, if chlorine trifluoride doesn't "burn" by the NFPA's definition, what is the NFPA's definition of "burning"?


texts: Why anions of weak acids are weak bases?

texts: This is what I saw from Chemistry: The Central Science 13th ed. by Theodore brown, page 698. It stated that there are two types of weak bases: one is those with lone pairs of electron and the other is anions of weak acids, which means conjugate bases of weak acids. My question is, aren't conjugate bases of weak acids strong bases? Because weak acids are less readily to give off proton but it's conjugate base can accept proton easily.


texts: Geometry optimization: dependence on initial geometry

texts: One would think that initial configuration should not significantly impact the final optimized geometry. Starting with two moieties, the final "optimized" geometry is not unique and depends highly on how they are placed initially. Is there a way to avoid this? Otherwise one could never be sure that they have ended up with the global minimum.


texts: Which plastic type is used inside dishwashers?

texts:
We have a drinking bottle made partly from polypropylene that wraps when washed in a dishwasher. We would like to change the plastic type so that it can withstand in dishwasher.

I know for a fact that my dishwasher at home has a lining inside made from polypropylene. After googling this  I have found a few sources that suggest that dishwashers would use a filler material in the PP called "calcium carbonate".

I would like to hear from someone who actually with confidence can tell us:

What is the usual plastic type used inside dishwashers? How is this plastic different from "normal" PP? Will we be able to use the same mold for this kind of plastic as "normal" PP?


texts: Why do unripe papayas taste less bitter after being boiled?

texts:
An unripe papaya tastes very bitter if you try to eat it. Actually, the juice that comes from it is so corrosive that it can burn your skin, causing severe pain. I've experienced this first hand when cutting raw papayas.

However, after boiling, these papayas taste quite bland. Very little of the original bitterness remains.

What chemical substances cause the original bitterness, and what happens to them when boiled?


texts: Is this expression correct "the reaction was not accomplished " when we check the final product finding two or more spots on TLC paper ?


texts:
Consider the paraphrase from Ebbing:

  It takes energy to break bonds & energy is released when bonds are formed

Let's look at the first statement  It takes energy to break bonds.

Is this true of spontaneous processes?
If yes, is this true only in a closed-environment sense, where the energy required for a reaction to occur between two molecules is the energy contained within those molecules; i.e. no outside energy is necessary?
If yes to 2), is this energy, outside the kinetic energy of the molecules themselves, potential energy (PE) stored in the bonds?

Then for the second statement, energy is released when bonds are formed.
When the PE of the reactants is greater than the PE of the products, heat is released and we have an exothermic process. Consider the conversion of ethane to ethene. This is an endothermic reaction requiring approximately 220 kJ/mol of energy (bonds broken (2X C-H) - bonds formed (C=C).

As the PE of ethene is greater than that of ethane, why is this not reflected when considering the sum of bond energies in each molecule? For example, for ethane we have 2,812 kJ/mol and for ethene we have 2,246 kJ/mol.
Given the bond energy of C=C (602 kJ/mol) is higher than C-C (346 kJ/mol), why would it be incorrect to assume the energy necessary to drive the reaction is stored in the C=C bond, given the PE of ethene is greater than that of ethane?

Lastly, when teaching cellular respiration, we speak of energy being stored in the phosphate bonds when ADP is converted to ATP and in photosynthesis, of the energy from sunlight being stored in the bonds of glucose.

Is this line of thinking correct, if not why?
If that line of thinking is correct, how do we reconcile this fact with "Energy is released when bonds are formed?
Would it be appropriate to say energy is both stored and released as bonds are formed?

I am a tutor hoping to master this content to best help my students. Please lend a hand to whichever questions you feel most confident in answering.


texts: How to calculate Ka for hydronium and Kb for hydroxide?

texts:
I am wondering how to calculate the $K_a$ for hydronium, $H_3O^+$, and the $K_b$ for hydroxide. Because hydronium undergoes the equilibrium

$\ce{H_3O^+(aq) + H_2O (l) <=> H_2O (l) + H_3O^+ (aq)}$ ,

isn't the constant  exactly 1? (And the same thing for hydroxide?)
However, Wikipedia gives the $pK_a$ for hydronium to be -1.7. Does it have something to do with the "concentration" of water, which is 55.6 M, and upon taking the negative natural log, is -1.74?


texts: Which conformer of beta D-glucose is more stable?

texts:
I drew the two chair conformers of  $ \beta $-D-glucose:

Which one is more stable?

I think it's the one with all of the OH groups in the equatorial position because of less steric hindrance, but I also know that the anomeric effect makes the axial one favored as well.  So I'm unsure which is more stable.


texts: Eriochrome Black T titration - Concentration of Indicator and endpoint

texts:
While not as frustrating an indicator as murexide, Eriochrome Black T's wine red to blue transformations provide significant challenges. The change from "fully wine red" to "fully blue with no trace of red" takes around 1mL. It goes through first from the wine red to a purple, which then becomes are deeper blue after several more drops (with still very slight traces of purple and hence red). Addition of several more drops thereafter produces a dark blue colour which appears to have no purple trace (there may be a slight amount), and adding 10 or so drops converts the darkish blue to a beautiful, light blue. Where is the endpoint here? I assume it is at the deep blue, although the wine red to purple transformation is very sharp and abrupt.

Another challenge that this indicator provides is the amount used. It appears the more indicator I put, the more a pure blue solution appears to have a purple trace. The endpoints differ with a tenfold difference in Erio T amount up to 1mL. I have tested this theory - with a dilute solution I titrate to the "deep blue endpoint", add more Erio T, and then hints of purple become visible etc.

Does anyone know the true endpoint of Erio T and the optimal amount to add?

Note: This was for a Mn (II) titration (ascorbic acid added). The problem manifests itself in magnesium titration as well, and prevents obtaining endpoints to any accuracy.

Edit: The concentration of titrant and analyte are both ~0.01M. This is quite standard for EDTA titrations.


texts:
Why is thallium(III) oxide stable while thallium(III) chloride unstable

Both the compounds have +3 oxidation state of thallium and the electronegativity difference between chlorine and oxygen is not very large. Then why is there such a large difference between the stability of the 2 compounds?


texts: Are there any "catalysts" that decrease the rate of reaction

texts:
Catalysts are things you can add to a reaction that provide an alternate reaction pathway for the reaction that decreases the overall activation energy of the reaction meaning the reaction is faster but the catalyst isn't consumed in the reactions. Are there any materials, in any reactions where a similar material can be added to a reaction that will decrease the rate of reaction by providing a more favorable reaction pathway but one that takes longer.
Maybe it isn't possible for a reaction to be more favorable but require a higher activation energy and this is why this kind of "pseudo catalyst" doesn't exist.


texts: Why enol content of ethyl acetoacetate is more in toluene than water?

texts: Ethyl Acetoacetate has enol content of 0.4% in water and 19.8% in toluene. What is the reason behind this? Does this anything have to do with the intramolecular hydrogen bonding in the enol form?


texts: Bioinformatics tools for predicting synthetic reaction for identified drugs?

texts:
We are aware of many bioinformatics open source tools like AUTODOCK, Smina for drug discovery through structure based virtual screening.

I was wondering if there are validated bioinformatics tools for predicting the synthetic reaction for the identified compound.

On browsing literature, I came across ReactPRED(1)

But again, I have not heard about this tool a lot. What are the tools available for predicting synthetic reaction for identified drugs in both open source and paid?

Edit:

By synthetic reaction, I am referring to the synthesis reaction of the compound. The tool should be suggesting the synthesis reaction for synthesizing the identified compound.

Tadi Venkata Sivakumar, Varun Giri, Jin Hwan Park, Tae Yong Kim, Anirban Bhaduri, ReactPRED: a tool to predict and analyze biochemical reactions, Bioinformatics, Volume 32, Issue 22, 15 November 2016, Pages 3522–3524, https://doi.org/10.1093/bioinformatics/btw491


texts:
I’m interested in quantitating lithium via NMR using a Magritek Spinsolve 60MHz bench top NMR spectrometer. Is there any evidence that suggests the volume of the liquid sample used in the NMR tube has any effect on the area of the spectra peaks? I’m interested in hearing opinions on the matter before running tests verifying if such correlations in-fact do exist.
I’ve seen in relevant literature that 0.6-1mL is generally a sufficient amount of solution for the 5mm tubes. However it’s not clear to me yet if this volume should be consistent between the calibrants and experimental solutions for analytical NMR. Thanks!


texts: What chemical properties make some grasses usable for producing textile fabrics?

texts: Textile fabrics are made out of cellulose fibres, that can be derived from cotton or bamboo. As far as I know all grasses contain cellulose, so why are only a few grasses used? What makes them so special? Why could you not use for example gamba grass/andropogon gayanus for that, which contains 30%  cellulose and 21% hemicellulose (http://www.lrrd.org/lrrd20/2/oded20027.htm)? Any insight on that would be very helpful


texts:
Chlorine can be found as the following oxoanions $\ce{ClO–} , \ce{ClO2-}, \ce{ClO3-}, \ce{ClO4-}$ in many chemical stockrooms. However, iodine is never found as $\ce{IO4-}$. Explain this observation.

I didn't really find any reason as to why periodate cannot exist, unlike anions such as flourate where it is limited by flourine's small size. After researching this further, I found that the periodate anion actually exists in compounds such as sodium periodate. Even though it has another form $\ce{IO6^{5-}},$ the periodate anion actually dominates its equilibrium. Thus, I was wondering what the intended/likely answer was?


texts: Is there a quantum chemistry package which calculates a second-order wavefunction?

texts:
I am trying to generate a change in density which corresponds to a second-order wave-function in standard Rayleigh-Schrodinger perturbation theory. I would like to try out a simple test on an atomic dimer. However, I am not sure if such a method is implemented in any of the standard quantum chemistry software packages. Does anyone know of such a package?

EDIT: What I am after is the following wavefunction:

$\Psi = \psi^{(0)} + \psi^{(1)} + \psi^{(2)}$


texts: pH value of a buffer solution of HClO and NaClO

texts:
So,
I have 200mL of HClO 0,64M.
I mix it with 0,1mol of NaClO.
How should I calculate the pH?

My question is about this: should I keep attention about changes made to the solution volume after adding NaClO?

So far this is what I've done.

Considering:

$\ce{NaClO + H2O -> Na+ + ClO-}$

With n(NaClO) = n(ClO-) = 0.1mol,

I calculated the molarity of the conjugate base:

[ClO-] = 0.1mol/0.2L = 0.5M.

Then I applied the Henderson-Hesselbalch equation:

pH = pKa + log([ClO-]/[HClO]) = 7.53 + log(0.781M) = 7.422

In this case I didn't consider the variation to the solution volume due to the addition of NaClO. So, is this correct?


texts:
Does the entropy of a system depends on the system's temperature?

I know that $\Delta S_{ext}=\frac{q_{rev}}{T}$ ($q_{rev}$ is the heat in a transformation if it is reversible).

My textbook says that the entropy of the exterior always depends on that formula (so it depends on the temperature).

But it says the entropy doesn't always depends on the formula, and we can only say the that in a transformation the entropy of a system can increase or decrease. So does it depend on the temperature?

Thanks!


texts: For two compounds that are symmetrical, why does the more compact one have a higher melting point?

texts:
In this post, I refer to two molecules B (Di-tert-butyl ether) and C (Dibutyl ether).

Wikipedia: Di-tert-butyl ether (B)
b.p.  107.2 C
m.p. - 61   C

ChemSpider: Dibutyl ether (C)
b.p.  142 C
m.p. - 96 C

I understand that Compound C has a higher boiling point than compound B, because of its greater surface area and therefore stronger intermolecular VDWs.

I don't understand, however, why Compound B has a higher melting point than compound C. A lecturer told me that this is due to compound B being more compact and symmetrical. I think that I understand the concept that some structures pack into a crystalline lattice better than others, such that the structure of the packing influences the strength of intermolecular forces within the solid, therefore affecting the melting point.

However, it seems to me that both B and C above are equally symmetrical in at least one conformation. Beyond that, C has conformations of greater surface area than B, which should further strengthen its intermolecular bonds in a solid state. I would expect the melting point of C to be higher than B; yet this is not the case.

I feel like the answer may lie in the fact that C has many more conformers than B. Even so, I can't seem to draw a link anywhere. Shouldn't the solid formed take the most stable crystalline structure, much like how water tends to just one of many crystal structures?


texts: Predict polarity (TLC, column) using ChemSketch (-Draw)

texts:
I'm currently working on a project where I have to make and isolate often quite similar molecules. But, as I change the functional groups the overall electronic situation and polarity of the product and of the side-products often changes. I can just estimate what spot on my TLC might be my product and check later with the NMR but I'm still interested in a software-supported way. So I checked ChemSketch (I don't use ChemDraw) and found some parameters that might be of help:

  The polarizability, the density, the molar mass, the index of refraction and (although often not displayed) the dielectric constant.

Now I know this is all just a very rough and simple calculation but sometimes I just need a very basic feeling if the molecule can be considered polar or not.

So I thought perhaps using the equations of Clausius-Mossotti and Lorentz-Lorenz I might be able to determine the dielectric constant (because the software is often unable to predict it).

To my understanding is the dielectric constant a very fundamental parameter here. Polar solvents have a much larger one than non-polar solvents and the dielectric constant is responsible for how well a salt is dissolved in a solvent. For TLC and column chromatography on a polar stationary phase, a more polar substance will move much slower.

So can I just break this down in comparison of two molecules, that the one with the higher dielectric constant will also have a smaller $\mathrm{R_f}$-value?


texts: I understand zero-filling increases the resolution of an NMR signal in the frequency domain, but I fail to comprehend how. Why do the artifical points appear between the real points in the frequency domain? Is it a byproduct of the fast fourier transform algorithm? Can someone explain this to me? Thanks!


texts: What makes a glowing splinter glow and a burning splinter burn

texts:
This question bugs me for years since I started learning the oxygen, carbon dioxide and hydrogen tests. I know you can make a glowing splinter burn when doing the oxygen test due to enough oxygen. But why won't it burn in ordinary air?

So, my question is what factor differentiate a glowing splinter and a burning splinter


texts:
I was wondering that at optimum temperature can 6,6'-bis(hydroxymethyl)[1,1'-biphenyl]-2,2'-dicarboxylic acid show esterification reaction.

I know that the two phenyl groups aren't in the same plane so is esterification reaction still possible?


texts: Why do atoms stay nearer to each other even when delocalized electron moves away

texts: When the delocalized electron moves from between two atoms to other then why yet the measurement of distance between those older two atoms is less than normal single bond.


texts: Removing water/moisture from car exhaust

texts: I know that car exhaust is almost entirely nitrogen, water and carbon dioxide. How would I go about removing the water? Would I have to condense it off? Any devices already exist for doing so?


texts: "Non-stick" action on ceramic-coated pans

texts:
I understand how PTFE, or Teflon as it is commonly called, prevents anything from sticking to pans; apparently, anything coming into contact with the PTFE coating has ignorably tiny van der Waals forces with it.

However, there are also ceramic coated pans, with similar properties.

How do ceramic coated pans prevent anything from sticking onto the pan?


texts: Perturbation Theory in Orbital Interactions in Chemistry

texts:
In the entire book, perturbation theory is used as a qualitative tool to rationalise some chemical phenomena. The authors write that
$$\psi_i = \sum_\mu{T_{ji}\psi_j^\circ}\tag{1}$$
The proof of the derivation for $T_{ji}$ involves the following statement:
$$T_{ji} = \left(\mathbf{C}_j^\circ\right)^\mathrm{T}\mathbf{S}^\circ\mathbf{C}_i \tag{2}$$
where
$$\left(\mathbf{C}_j^\circ\right)^\mathrm{T} = \left(C_{1j}^\circ \quad C_{2j}^\circ \quad \cdots \quad C_{mj}^\circ\right)\tag{3}$$
(indexing the coefficients for the jth unperturbed MO), and
$$
\mathbf{C}_i =
\begin{pmatrix}
C_{1i} \\
C_{2i} \\
\vdots \\
C_{mi}
\end{pmatrix}
\tag{4}
$$
(indexing the coefficients for the $i$th perturbed MO); $\mathbf{S},$ the overlap matrix, is defined as usual.
I'm not quite sure how the aforementioned statement is obtained. Could someone please walk me through how
$$T_{ji} = \sum\sum C_{nj}^\circ S_{nm}C_{mi}?$$
Source: Orbital Interactions in Chemistry, 2nd edition, page 794-802


texts:
What is the kinetic shift for the simple cleavage fragmentation if the ion source residence time is 100 microseconds, the time to reach the detector after leaving the ion source is 10 microseconds? (given that the simple cleavage is the green line below)

My work: Because kinetic shift is Ef-E0, E0 would be the energy at which the ion is in the ion source, or where the green line and 4 (from 100 microseconds, or 10^-4) intersect. Then Ef would be where the green line and 5 (from 10 microseconds, or 10^-5) intersect. Does this seem correct?


texts: What is the problem with forming 2,3-dimethylcyclohex-2-en-1-one?

texts:
I have suggested a mechanism for the formation of 3-ethyl-2-methylcyclohex-2-en-1-one A

but the question says problems would be encountered if a similar route was used to make 2,3-dimethylcyclohex-2-en-1-one B. I think perhaps a decarboxylation step is involved? Can someone please explain how to get to B and the difficulties in the mechanism?


texts: Can I solubilize lemon essence in water somehow?

texts:
I have a water based solution (95% water, the rest are salts) to which I want to add a lemon fragrance. I bought "water based lemon essence", but upon putting a mere drop in about 500 mL, the solution turned from crystal clear to milky off-white.
I researched and found that lemon essence is apparently one of many essential oils (citral, citronellal, cintronellol). None of which are water-soluble. That's why the result is an emulsion, and it's not translucent. (It mixed very well and it's very stable, that's not my problem)
I was wondering then if it's possible to give lemon fragrance to a water solution without turning it into a milky emulsion.


texts: Why does it hurt in the mouth when drinking carbonated beverages?

texts:
The typical explanation for the origin of the "sting" is that $\ce{CO2}$ turns into carbonic acid (reddit, yahoo), however the "explanations" there are   incomplete.

The answer I'm looking for would cover:

Is conversion to carbonic acid is really the case here? And what are the original compounds the same enzyme(s) is used for?
Why is there no "sting" from $\ce{CO2}$ found in air?


texts: For a gas having molar mass M, express specific heat at constant pressure in terms of heat capacity ratio

texts:
For a gas having molar mass $M$, express specific heat at constant pressure in terms of heat capacity ratio.

My attempt:

using $ C_p  - C_V = R $ and

$ \dfrac{C_p}{C_V} = \gamma $

$ C_p = \dfrac{R \gamma }{ \gamma - 1} $

But answer is
$ C_p = \dfrac{R \gamma }{ M(\gamma - 1)} $

But from where this $M$ is coming from? Isn't specific heat independent of $M$?


texts: Reacting sodium metal with aqueous sodium hydroxide, what would happen?

texts:
I know sodium metal, when reacted with water, produces flammable hydrogen gas but I was wondering if that would also be the case if I had aqueous 1M sodium hydroxide?

Would this reaction be safe or will it also produce a harmful compound like hydrogen gas?


texts: What is the origin of the naming of deoxycorticosterone acetate?

texts:
Deoxy- means the compound misses an oxygen comparing to the name without the prefix.
Acetate means ethanoate in IUPAC language. Many biologists still abide old rules and call it acetate. And finally, corticosterone. I just threw away thoughts and checked for the formula  online.
What is the law behind naming "corticosterone"? Is it relative to corticosteroids? Please answer in a detailed way!
Maybe it is corti+coster+one? Since I know that there exists cortisone and cortisol.


texts:
A. For certain ideal gas Cp=8.58 cal/mol-deg. What will be the final temperature and volume when two moles of the gas at 20 degrees celsius and 15 atmosphere are allowed to expand adiabatically and reversibly to 5 atm pressure? Find W, ∆U, and ∆H.
B. Suppose that the expansion takes place adiabatically against a constant pressure of five atm, what will be the final volume and temperature of the given gas?
I already solved part A but I have no clue for part B. Especially on how to get the final temperature and pressure.


texts: Why is hydrochloric acid often sold as 33% concentration?

texts:
What is the historical perspective for the choice of 33% concentration that is often found in commercial sales of Hydrochloric acid?

Is this the same reason we find sulfuric acid sold at 37% and Nitric at 68%?

I am guessing these are some limit at which further concentration, synthesis or purification reaches a chemical or economic limit but am curious to find out about the specific numbers selected.  Obviously, all of these are also sold in higher purities/concentrations as analytical reagents but that obviously takes more effort to produce and will cost more.


texts:
Molecules of an ideal gas are assumed to have zero volume, the volume available to them for motion is always the same as the volume of the container. In contrast, the molecules of a real gas have small but measurable volumes. At low pressures, the gaseous molecules are relatively far apart, but as the pressure of the gas increases, the intermolecular distances become smaller and smaller . As a result, the volume occupied by the molecules becomes significant compared with the volume of the container. Consequently, the total volume occupied by the gas is greater than the volume predicted by the ideal gas law. Thus at very high pressures, the experimentally measured value of PV/nRT is greater than the value predicted by the ideal gas law.

This is what I read in a website. In the above statements, what is the volume predicted by the ideal gas law? The volume predicted by the gas law, should be the volume of container. Now if volume occupied by real gas is less than the volume of container, how can the volume occupied by it be greater than that predicted by ideal gas law ?

Also, compressibility is given by $Z = \frac{PV}{nRT}$.  In this equation is P the measured pressure or the ideal pressure?


texts: Difference between chemical potential and gibbs free energy

texts: I know that the chemical potential is the molar Gibbs free energy and that it is an intensive variable and that the gibbs free energy is extensive. However, they have identical units: $\mathrm{J~mol^{-1}}$. I don't understand why $G$ is extensive if it has $\mathrm{mol^{-1}}$ in its units.


texts:
Can somebody please explain the mechanism of Peptization(or give a link to the website which explain the mechanism step by step). The Mechanism given in my book is somewhat different from the mechanism given on the Wikepedia. Also the Wikepedia one is baffling me.
The wikipedia Peptization states

  The electrical charges present at the surface of the particles are so "neutralised" and disappear.

This process is same in the preparation of coagulated solution

  The electrical repulsion no longer hinders the aggregation of particles and they can then coalesce to form a flocculent precipitate that is easy to filter.

Again my book has exactly same para that this step is used in preparation of coagulated solution
And isn't peptization reverse of it that is that making of colloidal solution from splitting aggregating precipitate molecules, but here we are forming precipitate again.

  When colloidal particles bear a same sign electric charge.

Does wikipedia means precipitate particle here?

Also, how does coagulation differ from peptization. I mean one method to prepare a coagulated solution  is by adding electrolyte (containing ion of opposite charge ). In the process of peptization the only difference is that charge(should be opp charge) and one of the ion should be same as that in the precipitate. Does the mean in coagulation ion should  be different?


texts:
Could anybody explain the following statement:

"The boundary surface is a common way to represent atomic orbitals, incorporating the volume in which there is about a 90 percent probability of finding the electron at any given time.

I don't understand what does the author means starting from "incorporating the volume.."


texts: Explaining differences in rate of propagation based on monomer structure

texts:
The values given below have been taken from my lecture hand out, and they weren't cited so I don't know where my instructor got them from

The $k_\mathrm{p}$ (rate constant for propagation in radical polymerisation ) step for the following monomers is given below:

$$\begin{array}{cc}
\hline
\text{Monomer} & k_\mathrm{p}~/~\mathrm{mol^{-1}~s^{-1}} \\ \hline
\text{Styrene} & 106 \\
\text{Vinyl ester} & 3000\mathrm{-}4000 \\
\text{Ethylene} &  16 \\ \hline
\end{array}$$

And the instructor explained the difference between the first two as follows:

  the benzyl radical is stabilised by conjugation, however the radical produced in a vinyl ester lacks stabilisation by conjugation and thus reacts more rapidly.

Seems like a fair explanation, however in the same table the $k_\mathrm{p}$ for ethylene is given as $16~\mathrm{mol^{-1} s^{-1}}$, the slowest propagation step of the three. Thus his explanation is not consistent with this observation I believe, because similar to the vinyl ester radical this one too is not stabilised by conjugation and should be similarly eager to react.

My instructor did not offer a satisfactory explanation and I was wondering if people could weigh in on this here.


texts: Suggestions for chemistry experiments to do regarding toxic gasses

texts: I'm doing a final project on mustard gas, and need an experiment to conduct. I'm obviously not allowed to make or work with mustard gas, but what else can I do? Any other gas experiments that would be able to say something about the qualities or mustard gas (density, reaction speed, gas laws, other stuff?)? Or maybe similar gasses with effects of mustard gas, just less lethal and fast?


texts: Is an element's "atomic electron configuration" EXACTLY equal to the term with the largest coefficient in the CI series of the neutral atom?

texts:
For atoms and molecules with more than one electron, the wavefunction cannot be written as a single Slater determinant, so the ground-state configuration of (the atom or molecule in question) is defined as the configuration whose Slater determinant has the largest (in absolute value) coefficient in the configuration interaction(CI) infinite series expansion.
My question is the following- let one set an element, say aluminium. Then, does the term with the largest coefficient in (the CI series converging to the EXACT wavefunction of a neutral atom of aluminium) EXACTLY consist of the 13 one-electron wavefunctions corresponding to 1s²2s²2p⁶3s²3p¹, without containing any 4s, 3d, 4p(etc) one-electron wavefunctions in the determinant?


texts: Most of the elements have isotopes, so the atomic masses are calculated depending on the percentage of the existing isotopes. That is clear. However, what about elements that have only one isotope (monoisotopic) - like fluorine? Shouldn't the atomic mass for it be a whole number and not 18.9984?


texts: How p-phenylenediamine (PPD) is produced? PPD is used as raw material for Kevlar (Para amid Fiber).


texts:
In the froth flotation process, the concentration of a sulphide ore takes place using $\ce{NaCN/KCN}$ as a depressant. It forms a soluble complex with the impurity sulphide.

Taking the particular case of lead extraction from Galena($\ce{PbS}$), $\ce{NaCN}$ reacts with the impurity $\ce{ZnS}$ present in it forming a soluble complex.
$$\ce{ZnS + 4NaCN → [Zn(CN)4]^{2-} + 4Na+ + S^{2-}}$$

We also know $\ce{Pb^2+}$ ions react with $\ce{NaCN/KCN}$ to form a white precipitate of $\ce{Pb(CN)2}$.

My question therefore is why when both $\ce{ZnS}$ and $\ce{PbS}$ are present in the solution only $\ce{ZnS}$ reacts whereas $\ce{PbS}$ doesn't? Or is it simply that it reacts but from an insoluble compound?


texts: What is the difference between 'particles', 'molecules' and 'chemical species'?

texts:
I have read the Chem.SE question about the difference between 'compound', 'mixture', 'element' and 'molecule', but I would like to know the precise definitions for more terms (see below). From the article, these are the definitions:

Elements are classes of atoms. Atoms of the same element are similar (if not identical) in their physical and chemical properties (but be aware of Isotopes which are physical variations among atoms of the same element).

Molecules are a group of atoms covalently bonded to each other.

Compounds are made up of two or more elements. Compound is often used interchangeably with the word substance.

Mixtures are collectives of different molecules or atoms.

How are compounds substances? Isn't 'substances' a general term for any chemical thing?
These are the terms that I would like definitions for:

chemical species
substance
particle
atom/isotope
salt

I am rather confused about these terms, because my tutor uses particles and molecules (and elements) as if they were the same thing. As for the rest, I want to know how to distinguish between general (such as chemical species, substance) and specific terms (such as particle, atom, isotope, salt).


texts: Calculating the theoretical percent purity of a recrystallization

texts:
The sample contains some percent A and some percent B with A being the majority. The solubility for both is given at two different temperatures. One where both are very soluble and one where both are much less soluble. From these five values I'm supposed to determine the theoretical purity of the recrystallized compound.

I'm surprised that this is possible and I have no idea how to even begin approaching it. I always thought that crystallization was structurally depended as well. Shouldn't the lattice favor the dominant compound? What if the impurity is less soluble at the low temperature than the majority compound? How can we mathematically represent such a (seemingly) complex phenomena with such little information?

Note: I don't mean percent yield, the question specifically stated purity.


texts: Metal reagent in dehalogenation of vicinal dihalides

texts:
In the dehalogenation of vicinal dihalides why can't sodium be taken as a reagent?

I understand that zinc is taken because it is reactive and rate of reaction would be considerably high and it doesn't form complexes. Because of this many other metals can't be used including magnesium as it forms complexes. But I don't understand why sodium can't be taken.


texts: why are amines more water soluble than alcohol for similiar molecular weight?

texts: kindly someone please explain the reason behind this behaviour despite the fact that oxygen is more electronegative and forms stronger hydrogen bond.


texts: Are all complexes with a polydentate ligand examples of chelation?

texts:
I'm getting a little confused about the definition of chelation and its implications (I should probably point out I'm only an A2 Chemistry student). The IUPAC defines chelation as the following:

  The formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central atom

Does this mean that any ligand that is not monodentate (e.g. even ethanedioate) is an example of chelation? I thought chelation was only for complexes with a large coordination number (e.g. $\ce{EDTA^4-}$), it would seem odd to call a single metal ion with 1 ethanedioate ligand chelated?


texts: Free database of polymers with Hansen parameters

texts:
I am developing a product that needs a component to expand when in contact with crude oil.

Found the wikipedia article about Hanses solubility parameters and thought it would be a good idea to run the parameters of crude oil against a list of polymers to find maybe the five closest polymers.

Where can I find a database of solvents and polymers online?

It should be noted that I know very little about chemistry, but enough about computer programming to be able to run the test against any database format.


texts: Why are nanoliposome encapsulated antibiotics still so unavailable despite being so effective?

texts:
I wasnt sure how the phrase the headline question really nor if this is the right place to ask it, but i'm primarily interested in the chemical synthesis aspect and the experience of chemists regarding this subject.
In the antimicrobial literature specific liposome or nano particle encapsulations of antibiotics have been shown over and over again to show immense potential for quite a long time by now, enhancing efficacy, pharmacokinetics while at the same time reducing toxicities. My question basically is, why is this not being used really? Advanced liposomes can be found in some vaccines for example and the likes of it. But we continue to pump e.g. Aminogylcosides like Gentamicin into people which while very effective against certain hard to treat organisms can fail due to 1. pharmacokinetic limitations (low intracellular penetration etc.) and 2. toxicity and damage.
Im not interested in the discussion about efficacy for treatment in people, as that wouldnt be on the subject of chemistry and that has already been shown, but rather what is it that makes it so hard about this being available? I found literature ranging from 20 years ago showing specific PH sensitive liposome encapsulations of Gentamicin vastly increased efficacy against gram negative intracellular infections in vitro and in vivo and immensely reduced toxicity towards human cells - yet its just nowhere to be seen.
Is it that hard to synthesize/make these compounds? Does it cost a castle made of gold to produce a single vial of it? I would like to hear chemists views on the complexity/cost ratio of the production if possible. I do no have an advanced background in chemistry but it is just hard for me to imagine it would take half the world to produce some specifically charged or ph sensitive liposomes - especially if the science on what and how has already been done.


texts: Given this liquid-liquid phase diagram, is the green line the nitrobenzene-rich phase?

texts:
The temperature-composition diagram for hexane and nitrobenzene at 1atm. The region below the curve corresponds to the compositions and temperatures at which the liquids form two phases. The upper critical temperature, $T_\mathrm{uc}$,  is the temperature above which the two liquids are miscible in all proportions.

Am I right in assuming that the right side (green line) is the nitrobenzene rich phase? Is that always the case? Whichever one has the side with a mol fraction of 1 that side is more abundant? If you don't understand my question just tell me, and I'll clarify


texts:
I need to find the formula, if there is one, which would calculate the correction of alcoholmeter.

Basically convert observed %ABV (Alcohol by volume) to actual %ABV using the sample's temperature.

I know the correction tables, but I am looking for the formula or do I have to use tables?.


texts: Can I make Ferrofluid without evaporating Ammonium?

texts:
I want to make ferrofluid, which is ferromagnetic particles suspended in a carrier fluid. Three methods I have seen involve using magnetic ink (for MICR codes), cassette tapes, or ferric chloride as the iron source. The last method is the only one that makes ferrofluid with nano-scale ferromagnetic particles. AFAIK, the process boils down to using ammonia to precipitate magnetite from a ferric/ferrous chloride mixture, coating the precipitated particles with oleic acid (acting as a surfactant), and suspending the coated particles in a carrier oil such as kerosene.

The steps (based on this):

Oxidize iron with ferric chloride to form ferrous chloride: $\ce{2FeCl3 + Fe -> 3FeCl2}$
Precipitate magnetite: $\ce{2FeCl3 + FeCl2 + 8NH4OH -> Fe3O4 + 8NH4Cl + 4H2O}$
Add oleic acid, evaporate the ammonia, and end up with surfactant coated magnetite nanoparticles?
Add kerosene to magnetite suspension => ferrofluid

There is another example here that has slightly different steps:

Dissolve $\ce{Fe^2+}$ and $\ce{Fe^3+}$ in $\ce{HCl}$ and mix
Precipitate magnetite
Repeatedly:

Separate precipitate from liquid with a magnet
Decant the liquid, leaving the precipitate
Add distilled water

Add $\ce{N(CH3)4OH}$

It seems to me that the first process generates a 'smoother' ferrofluid. I mean to say that it looks more like a homogenous fluid, whereas the ferrofluid in the videos from the second link looks more like a sludge.

I have two questions. First, what is actually happening in the first process when the oleic acid is added? From the first article, it sounds like the oleic acid reacts to form ammonium oleate, and then adding heat decomposes the ammonium oleate, releasing ammonia gas and dissolving the oleate ions, which then coat the magnetite particles. But that sounds a bit odd. Second, would the following work (create a suspension of magnetite nanoparticles suspended in a carrier):

Obtain a mixture of $\ce{FeCl2}$ and $\ce{FeCl3}$ via either method.
Precipitate magnetite
Separate the magnetite precipitate from the ammonium chloride via decanting (as in the second process)
Add oleic acid (and heat?) to coat the magnetite particles
Add kerosene to magnetite suspension => ferrofluid

It seems like removing the ammonium chloride via washing would be easier than via evaporation. Less heat, less time, less nasty fumes. But I don't really know what's going on when the oleic acid is added, so I'm not sure if my proposed method would actually work.


texts: Can you produce activated carbon from toast?

texts:
On the Skeptics stack exchange we have a question about burned toast being used as a treatment for poison, the idea being that burned toast acts as activated carbon.

We are skeptical due to the fact that gas activation requires heating to high temperature, but don't have the chemistry to rule out toast as a source of activated carbon.

My instinct tells me that:

Toast is not good source of carbon
Activation is not easily done in your average kitchen.

Can someone answer those 2 questions?

Is toast a good source of carbon
Can activated carbon be produced in your average kitchen without training or any special supplies?


texts: How is it thermodynamically possible to obtain energy from a piece of coal?

texts: If we put a piece of coal in open air we don't get any energy of it. But if we put fire to it in open air we get energy. Explain it with help of Gibbs free energy.


texts: Error in calculation of rate of reaction through graphs

texts:
I'm asked to find the Reaction Rate when t = 120 seconds (which involves differentiation) for an unknown Chemical Equation. The rate of a chemical reaction is defined as:

$$R =\frac{dC}{dt}\ \text{(Differentiation of concentration with respect to time)}$$

I'm given a set of 11 points $(x=t\ (\text{time}),\ y=C (\text{concentration}))$ which I need to plot in order to find a general trend for them.

After plotting all points and observing the resulting graph, I tried performing multiple regression analyses in order to find a function $C(t)$ that best fits the plotted points.

For each of the Functions I obtained from each individual Regression...

I derived each one
Evaluated each resulting derivative for $t = 120$, in order to obtain
the reaction rate for each case.

Finally, I compared each result (Reaction Rate) with the Literature Value, and calculated an error percentage for every case.

These were my results:

$$\begin{array}{|c|c|}
\hline
\text{regression type} & \text{error percentage} \\ \hline
\text{exponential} & 26.92\% \\
\text{quadratic} & 22.89\% \\
\text{cubic} & 19.1\% \\
\text{quartic} & 1.39\% \\ \hline
\end{array}$$

My question is:

Many sources (including my book) claim that a High-Degree Polynomial Regression (Cubed Regression and above) is not appropriate for describing a Physical Phenomenon, even when the Regression Fit is perfect (R=1).

However, based on the table above, the most accurate answer I got was obtained through a Quartic Regression, while the rest had considerably higher error percentages.

Am I missing something or is it just an exception? Any clarification would be much appreciated!


texts: Comparing the solubility of glucaric acid and mucic acid

texts: Why is glucaric acid soluble in water but not mucic acid? The chemical formulae seem to be the same so why is it that one is more soluble than the other?


texts: What is the oxidation state of nitrogen in N2O5?

texts: According to the formula it should be +5 but according to its structure shouldn't it be +4? How is it +5 then?


texts: Search materials by HOMO, LUMO and work function

texts:
I need to search organic semiconductors for organic photovoltaics (OPV) by their HOMO, LUMO, work function at 300K (as I understand, WF cannot be derived from HOMO and LUMO because semiconductor can be differently doped and Fermi level depends on concentration of dopants) and deposition methods (such as CVD, PVD, spin-coating, electrodeposition, etc)..

Is there some free site where I can either download a machine-readable table of needed data or make a search based on that criteria? What is it?


texts: Does CO2 form carbonic acid in the atmosphere?

texts: Since when $\ce{CO2}$ goes into water it makes carbonic acid, then what happens when it rains? Some of the $\ce{CO2}$ in the air joins the rain drop as it falls and while the rain drop falls and changes shape, it releases then regains $\ce{CO2}$? Is there a critical point or point of saturation within the raindrop for $\ce{CO2}$? It’s an interesting dynamic considering the complexity of storms and weather systems.


texts: What is the viscous component in viscoelastic materials?

texts:
All real solid materials are in certain way viscoelastic, because an ideal fully elastic material doesn't exist as well as a fully viscous solid material. According to rheologic models it is possible to define approximately the deformation of the material under stress.
I was searching information, but I don't know yet what is the cause of the viscosity.
For example this is the rheologic Tuckett model, which clearly shows the viscoelasticity of a real material (specifically a polymeric material)

An ideal elastic material after stress release would return to its original shape, but in a viscoelastic one, energy dissipation occurs and the material has not the sufficient energy to come back to its original shape (plastic deformation is resulted)
Here is the example of a ideal elastic material, where all the energy returns and the material takes back its shape and note, that the deformation response to the stress is immediate. On the other hand the viscoelastic materials have a late reaction to stress (why?).

The issue at stake is:

what does it mean "when a material is more viscous than another one" and what is the cause of the viscous component in solid material?
Viscosity in liquids is caused by friction of the particles during movement. Surely it is not possible to apply the same answer to the viscosity in viscoelastic materials.

Thank you in advance for helpfulness


texts: What type of organic compounds are used in OLED technology?

texts: I know that there are organic compounds that exhibit electroluminescence, and are those types of materials difficult to synthesize?


texts: Does adding ice to sparkling mineral water extend the 'fizziness' of the solution before the drink goes flat?

texts:
To my understanding the carbonated beverage loses its $\ce{CO2}$ content as gas bubbles which gives the drink its 'fizziness'. The loss of $\ce{CO2}$  occurs due to the low solubility of carbonic acid formed during carbonation resulting in an excess of unreacted $\ce{CO2(g)}$ which is trapped in the container when bottled and escapes when opened:

$$\ce{H2O(aq) + CO2(g) -> H2CO3(aq) + CO2(g)}$$

Temperature and volume of the solvent play a critical role in the solubility of matter.

Would the decrease in temperature and slight increase in solvent caused by the ice cube being added to a carbonated beverage exposed to air cause the solution to remain 'fizzy' for longer than the same solution at RT°C with no solvent increase?


texts: What is heat of vaporization? How can it be used at temperature as low as 25 °C?

texts:
When I first learned this term. I was introduced to this graph:

The heat in this case is at 100 °C, which I had ever since believed to be the only temperature of vaporization, assuming vaporization = boiling.

Then I saw a table with all the heat of vaporization values for different compounds. Most importantly, all these values apply to reactions at 25  °C.

Different heat of vaporization values apply to different temperature. but water, for ex., cannot boil, with vapor bubbles, unless at 100 °C, thus all the energy used will just be used to simply raise the temperature. wouldn't it?


texts: Thermochromic pigment that changes at around 50 °C / 120 °F?

texts:
I wish to find a pigment that can indicate when a battery contact is getting too hot, and all the thermochromic pigments from hobby stores change color below body temperature, at 31 °C is the highest I found.

What kinds of thermochromic pigment can be used for electronic components, that would change color at 40–50 °C / 120–140 °F?

The best thing would be easily obtainable and would give an rough indication of temperature transitions from 30 to 55 °C


texts:
For those who understand plastics and epoxies in particular, curious to know if I can add a correctly proportional amount of flexane urethane to epoxy paint without worrying about compatibility issues. IOW is there any non-typical or particular ingredient in epoxy that might prevent successful mixing of the two?
For clarity, I am using epoxy paint for a waterproof top coating on my rv roof, but would like to ensure it is a bit rubberized and not too brittle. Devcon flexane addition seems to be the answer but I can't find any guidelines for the DIYer.
Please go easy if this question is too general in the area of chemistry, seems like this is the correct forum, and thanks for any info. If you have personal experience working in the chemistry of urethanes, you may have valuable knowledge on this.
Product links:
https://www.amazon.com/Olympic-Poxolon-Two-Coat-Epoxy-Swimming/dp/B07BLMHKBK
https://www.reynoldsam.com/product/flexer-epoxy-flexibilizer/


texts: Why does Nitrogen gas appear in the equation for making producer gas?

texts:
My book gives the equation for synthesis of producer gas as follows:

$$ \ce{2C{(s)} + O2{(g)} + N2{(g)} -> 2CO{(g)} + 4N2{(g)}} $$

And it says that the stuff on the right-hand side is called producer gas.

My question is why does $\ce{N2}$ even appear in the equation? It isn't reacting is it? It's just a mixture.


texts: Why and how does hydrogen peroxide decompose in the presence of light?

texts: When exposed to UV light, hydrogen peroxide decomposes into $\ce{H2O}$ and $\ce{O}$. Why does this happen and more importantly how? Is the energy from light absorbed by the bonds which are specific to UV frequency and thus leading to decomposition?


texts: $\ce{Cu}^{2+}$ has nine d-electrons, regardless of the ligand field strength it will have one free electron (so it is paramagnetic. Are $\ce{Cu}^{2+}$ octahedral complexes high spin or low spin?


texts: Tap water pH adjustment using citric acid

texts:
I've lowered tap water pH from 7 to 6 using citric acid. After couple of hours pH raised again to 7.

What is the reason for this raise? Citric acid overcomes waters buffering  feature then raise the $\ce{H+}$ concentration in water. Why pH raise again?

The pH was measured using a pH meter.


texts: What are the consequences of having an element with an atomic number above 137?

texts: In other words, is an element such as Feynmanium the last chemical element that can physically exist on a planet such as Earth?


texts: What is the maximum amount of medicine that could accumulate in the body if the compound has a half-life of 24 hours?

texts: If a patient is prescribed 25 mg per day of a compound that has a half-life of roughly 24 hours, what is the maximum accumulated amount of the medicine that would build in the patients body?


texts:
I have been taught that orbitals can overlap only when all of them are in the same energy state. That is the reason why the orbitals hybridise in a kind of 'mixing up' and give rise to orbitals having same energy state.
But my question is: Why do the orbitals need to be in the same enrgy state to overlap with orbitals of other atoms?


texts: Synthesis for turning synephrenine into N-methylphenethylamine

texts:
I am trying to devise a synthesis to change synephrine (4-[1-hydroxy-2-(methylamino)ethyl]phenol) into N-methylphenethylamine.

I was figuring that I could remove the hydroxyl group attached to the ethyl part using thionyl chloride to convert the hydroxyl into a chloride and then remove the superior leaving group using $\ce{LiAlH4}$ as a reagent and $\ce{AlCl3}$ as a catalyst, but thionyl chloride affects amine groups and I couldn’t find any information about how to protect the amine group when performing this reaction to reduce the hydroxyl.

I also researched how to remove the hydroxyl from the benzene ring but that involved using zinc and distilling the benzene which wouldn’t work for this because the boiling point of the substance is around 341 °C for synephrine.

Any insight would be really helpful.


texts:
I would expect an aqueous solution of ciprofloxacin to be basic for the following reasons:

The carboxyl group has pKa = 6.09 and the secondary amino group has pKa = 8.74. Because 8.74 is further from neutral pH than 6.09, I would expect the pH of an aqueous solution to be above 7.
The tertiary amino groups are connected to an aromatic ring, so they should be very weakly basic and not affecting pH much.

However, the PubChem Compound Summary says the following about ciprofloxacin: "pH range for the 1.0% aqueous concentrates in vials is 3.3 to 3.9; the pH range for the 0.2% ready-for-use infusion solutions is 3.5 to 4.6" (see https://pubchem.ncbi.nlm.nih.gov/compound/ciprofloxacin#section=pH)

Is an aqueous solution of ciprofloxacin solution really acidic and if it is, what is the reason?

I also found an article citing several estimates of the pKa:s and the consensus seems to be that the amino group is stronger than the carboxyl group. (Babić et al. Determination of pKa values of active pharmaceutical ingredients. Trends in Analytical Chemistry, Vol. 26, No. 11, 2007.)

Here is a picture of ciprofloxacin from Wikipedia:


texts: How to name molecules with a hydroxyl group in a side chain?

texts:
TL;DR: Are there clear nomenclature rules for naming the below molecule?

Today in school we learned about the nomenclature of alcoholes. Unfortunately, it was not mentioned what to do with hydroxyl groups in side chains.
With the rules we learned I would guess the name of this molecule is something like 2-(methylol)-propane-1,3-diol. But I could not find any specific rule telling me how to name hydroxy groups in side chains. 1

A free molecule builder with integrated naming I found names the molecule as follows:

  2-(hydroxymethyl)propane-1,3-diol

But I'm still not sure if this is the right way to do it.

Are there any precise IUPAC nomenclature rules that say that you use "-ol" in the main chain and "hydroxy" in side chains? 2

1 I did some research with no solutions: our schoolbook, some websites, Chemistry Stack Exchange...

2 I mean, isn't this IUPAC's aim? To provide (relatively) clear nomenclature rules?


texts: Are adamantane crystals covalently bonded?

texts:
I'm writing a report and need one thing clarified after reading the Wikipedia article on adamantane:

'All the above methods yield adamantane in the form of polycrystalline powder. Using this powder, single crystals can be grown from the melt, solution or vapor phase (e.g. with the Bridgman–Stockbarger technique). Melt growth result in the worst crystalline quality with a mosaic spread in the X-ray reflection of about 1°. Best crystals are obtained from the liquid phase, but the growth is inpracticably slow – several months for a 5–10 mm crystal. Growth from the vapor phase is a reasonable compromise in terms of speed and quality.[2] Adamantane is sublimated in a quartz tube placed in a furnace, which is equipped with several heaters maintaining a certain temperature gradient (about 10 °C/cm for adamantane) along the tube. Crystallization starts at one end of the tube which is kept near the freezing point of adamantane. Slow cooling of the tube, while maintaining the temperature gradient, gradually shifts the melting zone (rate ~2 mm/hour) producing a single-crystal boule.[16]

Would I be write in thinking that these crystals are not randomly shaped diamond structures you would get if the adamantanes covalently fused with eachother? In other words, are the crystals formed from polycrystalline adamantanes (with different numbers of basic ten carbon adamantanes in one derivative crystal) bonding together without covalent bonds? Or perhaps without many covalent bonds? For example, one C-C bond between two crystals? What other type of bonding could be at work here? Is the macro-crystal structurally weak as a result?


texts: are there any stable four membered chelate rings?

texts:
With reference to coordination compounds, most chelate rings formed with the metal atom and ligands are 5-member rings (including the central metal atom), such as complexes with Oxalate, ethylenediamine, dimethylglyoxime and glycinate ions as complexing agents.

Are there any compounds which contain stable 4-member chelate rings? Or any 7-member rings as well for that matter? I understand that angle strain makes these complexes hard to form but are there any exceptions to this trend?


texts: Is using the term "family" strictly correct when we mean a group of the periodic table or is it just in general use (and should perhaps be discouraged in favour of using "group" exclusively)?  At my highschool, other teachers refer to the transition metals as a family; is this a common practice?


texts: How do I calculate the total volume when i mix 1000 kg of glucose with 5000 L of water

texts:
I want to know how to calculate the resulting volume when I mix 1000 kg of glucose into 5000 L of water.

How does the calculation change if I'm mixing NaCl into the water, instead of glucose? Or how does the calculation change if im mixing several things into water (CaCl, Nacl, ect.)?

Sorry if this is a basic question, I have searched alot for a way to calculate this, but could not find answers that clearly explained how to calculate.


texts: How does temperature affect equilibrium, according to Le Chatelier's principle??

texts: I want to understand this concept in detail. I am getting confused with increase in temperature backward reaction takes place or forward?? And how?? Proper explanation is needed.


texts: Comburent, to the best of my knowledge, refer to substances that catalyze combustion reactions without reacting itself or being flammable independently, such as potassium chromate. How would oxidizing agents assist combustion reactions?


texts: In Water Solution will there be an interaction between Ozone Gas and Carbonic Acid

texts:
Original Question Posted 8/31/15
We are trying to predict what will happen when Carbon Dioxide gas is introduced into a contact chamber that serves as an Ozone Contact Chamber.  These Contact chambers presently oxidize compounds found in Municipal Pool Water along with Chlorine at below 5ppm. there are 3 contact chambers (one for each pool) and the Temperature range is from 104 to 80 F. We are switching from Hydrochloric acid to Carbon Dioxide to keep the Total Alkalinity from dropping when the acid is introduced.

"Predict what will happen" is exceptionally broad. If you can narrow your question to specifics, that will help a great deal. For instance, we don't know what the compounds are in the municipal pool water. See this link for a guide to asking questions here on chemistry.SE. –  Todd Minehardt yesterday
Ozone and carbon dioxide will be pretty much indifferent to each other. Indeed, ozone is known for its ability to oxidize almost everything, but CO  2   is already a final product of oxidation. "What is dead may never die", they say. Likewise, CO  2   may never be oxidized. –  Ivan Neretin yesterday

Thank you for taking the time to respond Todd and Ivan. The other compounds in the municipal pool water would include body oils, salt from perspiration and whatever else a particular bather might introduce. We are using Calcium Hypochlorite as a chlorine source and, depending on the PH may also leach Calcium from the Plaster of Pool Walls. The calcium harness varies in the Three separate bodies of water from 400 to 1200 and we endeavor to keep the PH between 7.2 and 7.6.  The Total Alkalinity is around 20 in the 2 bodies of water in which the PH is controlled by adding Hydrochloric acid. We have started using Carbon Dioxide in our smallest body of water and are introducing it in the water returning to the pool perhaps 150 ft away the Total Alkalinity in that pool has risen to 120 ppm which helps to maintain a more stable PH.  Because the piping to the other 2 pools is not as long we are thinking about introducing the Carbon Dioxide into the line the ozone is injected into before the contact chambers. Ivan stated that the Carbon Dioxide would not interact with the ozone.  My research implies that both Carbonic Acid (the objective of injecting Carbon Dioxide) and Ozone are very unstable, and Carbonic Acid has a very short life.  Is it likely that the Carbonic Acid would interact with the Ozone before the Carbonic Acid can effect a PH change (in effect neutralizing both objectives)?        Thank you  for any feedback you may provide.


texts:
For size trend down a group, it is known that:$$Al\gt Ga$$
Due, to d block contraction of gallium.
Why isn't this the case when it comes to silicon and germanium?
Won't the poor shielding effect from the d electrons have an effect here?

The Answer on the SE for a similar question does not really answer the question.


texts: In many fields of science (e.g. biology, medicine, psychology, statistics, physics), machine learning and artificial intelligence techniques are becoming more and more popular to analyze data. Is it also so in chemistry?


texts: Finding new pH after NaOH added to buffer solution

texts:
I have a buffer containing 0.2 M of the acid $\ce{HA}$, and 0.15 M of its conjugate base $\ce{A-}$, with a pH of 3.35. I need to find the pH after 0.0015 mol of $\ce{NaOH}$ is added to 0.5 L of the solution.

I started by converting everything to moles, writing out an equation for $\ce{HA}$ and $\ce{OH-}$ reacting to make $\ce{H2O}$ and $\ce{A-}$, getting 0.0985 mol of $\ce{HA}$ left after all the $\ce{OH-}$ was used up, and 0.015 mol of $\ce{A-}$ produced.

At that point I got a bit stuck. I tried doing things a bunch of different ways after that, such as trying to calculate $\mathrm{p}K\mathrm{_a}$ by using the Henderson-Hasselbalch equation, but I'm not getting anywhere near the answer. I calculated a $\mathrm{p}K\mathrm{_a}$ of 3.47. I added the amount of $\ce{A-}$ made when $\ce{HA}$ reacts with $\ce{OH-}$ to the original moles of $\ce{A-}$ in the buffer (I calculated 0.18 M $\ce{A-}$), and tried putting that, the leftover moles of $\ce{HA}$, and my $\mathrm{p}K\mathrm{_a}$ value into the equation, but that wasn't right either.

What am I doing wrong?


texts: I can't find a simple definition via google. All I get are research papers, that I don't understand.


texts: Odd Acidity Trend in Hexaaqua Metal Complexes

texts:
In the following link (three quarters down the page) it states that theoretically there should be a proportional relationship between the ionic radius and pKa of a hexaaqua metal complex (provided that the charge of each metal is the same).

The website's reasoning for this is that due to the smaller ionic radius, there is a smaller volume meaning that there is a greater charge density. Therefore this will cause a greater distorting effect on the electrons in the $\ce{O-H}$ bond. Hence this will enable the $\ce{H}$ to be deprotonated more easily, resulting in a lower pKa value.

However it later says that experimental data don't fit this relationship shown by one of the graphs in the website:

Obviously $\ce{Cu^2+, Cr^2+}$ and $\ce{V^2+}$ don't follow this relationship at all. The author of the website states that he has no idea why this happens.

I was wondering if anyone here could provide a more in depth explanation on how ionic radius effect acidity which perhaps can explain why these metals don't follow this linear relationship.


texts: We all know how CO2, as a greenhouse gas affects the climate and causes global warming. I was thinking of a small device, which could be attached to the exhaust pipe of an automobile. It could convert the CO2 into something having negligible greenhouse effect, such as water. Is this feasible? Thanks!


texts: What facts are being used in this atomic structure question?

texts:
I wish to understand how to solve this atomic structure question:

  For the ground state, the electron in the H-atom has an angular
  momentum = $\hslash$ , according to the simple Bohr model. Angular
  momentum is a vector and hence there will be infinitely many
  orbits with the vector pointing in all possible directions. In
  actuality, this is not true, because:

Bohr model gives incorrect values of angular
momentum.
only one of these would have a minimum energy.
angular momentum must be in the direction of spin of electron.
electrons go around only in horizontal orbits.

Actually, we have been taught Bohr orbits a lot in class, with formulae for everything (atomic radius/electron orbital speed/various energy levels/etc.)  and also basics of the quantum mechanical model. However, we didn't go into such a great depth of Bohr orbits as asked in the above question.

Specifically, I don't know of any reasonable arguments against points 1,2,3. Point 4 is evidently wrong based on the quantum mech model.

  How do I develop any claim for/against the points 1,2,3? What are the facts involved here?


texts: How does salt push out the water from vegetables, meat, etc.?

texts:
Where can I find out, how does this process work? Have you noticed, that when you salt mushrooms, eggplant... or add sugar to lemon - some "juice" comes out.

Any explanations? Or maybe name that reaction?


texts: Thermodynamic control or kinetic control?

texts:
In my notes, it is written that the case 1 product will be major one. The explanation given is as follows:-

  However, since the pi clouds of alkenes are perpendicular to each other, the resonance factor will be reduced. Till the time resonance occurs, water would have already attacked the positive charge centre and hence the thermodynamic-controlled product will be favoured.

I don't get this thing!


texts: Nitrogen molecule vs carbon-carbon triple bond stability

texts: Why does the triple bond in the nitrogen molecule convey stability, whereas a triple bond between carbon atoms conveys instability?


texts: What is the chemistry behind cleaning silverware with aluminium foil

texts:
This question has a accepted answer on this site already:

What happens during cleaning silverware?

but the reason I ask the question again is because I found different "recipes" for the technique and also different reaction formulas in other sources.

The "recipe" given in the linked question is

  "Put [the silverware] into a pot with some club soda and a piece of aluminium foil and pour over a hot water."

And the reaction formulas given for "blackening" is the following

$$\ce{3Ag2O(s) + 2Al(s) -> 3Ag(s) + Al2O3(s)}$$

and for the reaction with the aluminium foil

$$\ce{3Ag2O(s) + 2Al(s) +3H2CO3(aq) -> 3Ag(s) + 2Al(OH)3(aq) + 3CO2(g)}$$

But I also found the following "recipe" in a Swedish newspaper

"Put aluminium foil in a bowl. Put some baking powder on the foil. Put in the silverware. Add more baking powder. Pour over hot water and wait."

I assume this recipe is more or less equivalent to the one given earlier since the baking powder essentially turns the water into carbonated water?

The reaction formula for the "blackening" of the silver given in the newspaper is

$$\ce{Ag + sulfurcompunds + O2 -> Ag2S + H2O}$$

and the reaction with the aluminium is described as following:

$$\ce{2 Al(s) + 3 Ag2S(s) + 6 H2O(l) - 6 Ag(s) + Al2O3(s) + 3 H2S(g)}$$

The newspaper also links to a small piece written at a University in Sweden with regards to this question.

where they explain the blackening of the silver in the same way as the newspaper but they give a different reaction formula for the aluminium reaction

$$\ce{2 Al + 3 Ag2S -> 6 Ag(s) + Al2S3}$$

So my question is: Is any one of these reaction more "true" (occurring more often naturally) than the others or is it the case that a little bit of everything is happening?


texts: Reason for usage of Metal chlorides and Platinum or Nichrome wires in flame test

texts:
I'm studying about the s-block elements in my course of Inorganic Chemistry and I happened to come across the following text.

  Electrons may be quite readily excited to a higher energy level, for example in the flame test. To perform this test, a sample of Metal Chloride or any salt of metal moistened with conc. HCl, is heated on a platinum or nichrome wire in a Bunsen burner flame.

Why are metal chlorides specifically used and also what is the role of the Plantinum or Nichrome wire?


texts: IUPAC of heterocyclic compounds terminology

texts:
During my studies of heterocyclic compounds I learned that monocyclic compounds has prefix+ stem+ suffix.
the prefix is coming from the heteromolecule name (e.g oxgen --> oxa- )

however the stem and suffix is ambiguous to me. I can link some of the stem (e.g et --> from tETra)  but what about all other stems and suffixes. Where do they came from?

It will be very helpful if the source of terminology is documented here.


texts:
So lately I've been studying the concerted metalation-deprotonation of thiophene and I came to the conclusion that the alpha positions of thiophene are the most reactive, which is why one of those alpha carbons (either at the 2 or 5 position) will be deprotonated en metalated.

But why are the alpha carbons on thiophene the most reactive ones and why is thiophene preferred during concerted metalation-deprotonation if there are other heterocyclic compounds that are more reactive?

Thanks!


texts: Can you find 5 mistakes in this organic molecule?

texts:
I found two:
1) the Oxygen needs a positive charge
2) the carbon on the far bottom has 5 bonds


texts: How is adenosine synthesized in biology?

texts:
I understand the constituent parts of adenosine (adenine and ribose) and that it can be broken down from ATP anabolically. Can adenosine also be formed catabolically? If so, what is the mechanism?

What's the mechanism for combining ribose and adenine in the cell?

A general explanation or citation would work. No need for someone to go out of their way to draw pictures. Thank you very much!


texts: Usually tetraethyl orthosilicate/tetraethoxy silane (TEOS) is mixed with both ethanol and water to produce silica in a sol-gel process. I am curious what happens if one adds TEOS to water at a high pH, without any alcohol. Would TEOS simply not mix and not react with water? Or it would hydrolyze too rapidly and not condense at all?


texts: What does it mean by 'photons of higher intensity'?

texts:
I found an Assertion and Reason question related to transition energy in Bohr's orbits.

Assertion In the H-atom, photons of higher intensity are emitted when electron falls from the 2nd to 1st orbit than when it falls from the 4th to 2nd orbit.

Reason Transition energy from the 2nd to 1st orbit is greater than for the 4th to 2nd orbit.

The answer says the Assertion is false and Reason is true.

What does it mean by photons of higher intensity? Is it talking about the frequency? But if it was talking about the frequency, then the Assertion would be true.


texts: Reaction between potassium permanganate, alum, and sodium hydrogen sulfite

texts:
When I was a teenager, I played with a chemistry set. I tried adding potassium permanganate, alum, and sodium hydrogen sulphite (not sodium hydrogen sulphate) to water.

Upon adding the third ingredient, the water would rapidly turn clear, and a brown precipitate would form. After filtering this out, I allowed the water to evaporate, which left a white crystalline deposit. All three ingredients were definitely needed in order for the reaction to happen, which is why I remember it, since none of the other reactions I knew about needed three reactants. (This was a long time ago, so there's a very slight possibility I've mis-remembered the ingredients, but I'm 99% sure they're right.)

At the time, neither my teachers nor my parents could help me work out what kind of reaction it might be, so out of sheer curiosity, I thought I'd ask here. I'm no chemist, so simple explanations would be appreciated.


texts: Why p,d and f orbitals have non spherical shapes

texts:
I know what orbitals are. The orbitals are solutions (also called wave functions) to the (time-independent) Schrödinger equation[ref].

What I don't understand is why p,d,f orbitals have non spherical and s has a spherical shape. Our universe is made up of many circular or spherically (not perfect)  shaped objects like stars, planets, bubbles, droplets, wheels etc. I always thought (or guessed) circular and spherical shapes are the most efficient shapes in our universe. Then why p,d and f have non-spherical shapes or non efficient? Is there any other logic other than solution to Schrodinger equation which explains these unique shapes?


texts:
I have struggled in attaining a solid grasp of the Lewis acid/base concept largely because so many sources seem to offer conflicting definitions.

For instance, Klein's Organic Chemistry mentions that Brønsted–Lowry acids and bases are strictly a subclass of Lewis acids and bases. Other sources say this is true of bases but that a Brønsted acid need not be a Lewis acid and vice versa.

A common example of a non-Lewis acid provided by Wikipedia is $\ce{HCl(g)}$. The rationale being that it has no available empty atomic and/or hybrid orbitals to accept an electron pair (it does have an empty antibonding orbital though — see below).

Another source says hydronium is only a Lewis acid if it is "informally" treated as a hydrogen ion $(\ce{H+})$.

There appears to be further disagreement on whether the adduct formed in the Lewis acid/base reaction is necessarily a product or whether it can effectively appear as a transition-state before splitting apart to give the products. For example, say something like

$$\ce{NH3 + H2O <=> NH4OH <=> NH4+ + OH-}$$

Other users on this site suggests the approach should be to consider molecular orbitals. I will further note that $\ce{HCl}$ has an empty antibonding orbital so this definition, although arguably the best I can think of, still necessarily conflicts with multiple other sources labeling $\ce{HCl}$ as a non-Lewis acid.

Any help on resolving some of these apparent conflicts would be appreciated.


texts: Poly(3-hexyltiophene-2,5-diyl) (P3HT) reactions with inorganic salts in aqueous solution

texts:
I would need for my research at least as a starting point to know what kind of reactions occur at the interface of P3HT and an electrolyte. The electrolyte is simple $\ce{KCl}$ solution, maybe with $\ce{HCl}$ or $\ce{KOH}$ added. The reactions of polytiophene with the same type of electrolyte will do, if there is no information on P3HT. The two molecules don't seem to be that much different to me from the point of view of electrolytic reactions.

What I really need is information about reaction kinetics, at least in the form of some reaction constants, but simple stochiometric equations are still better than nothing at all, so I'm interested in those, too. I have been searching for some time now, but I'm not a chemist, and I don't really know where to look to find something like this.


texts:
In Clayden's Organic Chemistry it gives the Houk model as a way for predicting selectivity for alkene reactions where an existing stereocentre is present (diastereoselectivity).

Unlike the description of the Felkin-Ahn model, there is no real description of how the Houk model works, and I can't find this information in March Advanced organic chemistry either.

My feeling is that there must be some stabilising interaction between the pi system of alkene with a sigma orbital on the adjacent carbon, however this doesn't explain why one would be favoured over another.


texts: Electron Spin, and the Stern-Gerlach Experiment

texts:
I think I understand the basics of the electron spin. However, I'm trying to figure out how to tell if, when shooting a beam of atoms (the Stern-Gerlach experiment), how to tell if an element will have some atoms deflecting up and some down?
I initially thought to draw out the electron distribution of each possible element (it's a multiple choice question) and then try and figure out which ones were spinning up and which were spinning down. But this doesn't align with the answer to the question. Any guidance would be appreciated?


texts: What is the difference between "reaction in both directions" and "equilibrium"?

texts:
According to the Wikipedia page on Chemical Equations:

  Symbols are used to differentiate between different types of reactions. To denote the type of reaction:
  "$=$" symbol is used to denote a stoichiometric relation.
  "$\rightarrow$" symbol is used to denote a net forward reaction.
  "$\rightleftarrows$" symbol is used to denote a reaction in both directions.
  "$\rightleftharpoons$" symbol is used to denote an equilibrium.

How is a "reaction in both directions" and an "equilibrium" any different? Aren't they supposed to be identical?


texts: On the meaning of distinguishability, and wavefunctions for 3 electron atoms

texts:
In a 2-electron atom at lowest energy, the $(1s)^2$ is occupied and the electronic wave-function must satisfy anti-symmetry requirements in the particle coordinates, as the spatial wave function is symmetric. How is the situation in a 3 electron system?

In a 3-electron atom (or in a nucleon with one excited quark) of lowest energy, say the $(1s)^2(1p)$ states are occupied, is the fermion in the $(1p)$ state distinguishable? I.e. must my wave-function still treat all 3 electrons indistinguishably, or are mixed symmetry wave-functions now physically viable?


texts:
For context: I got a question asking, "Which of the following alkaline earth metals do not give flame colour?". I quickly marked $\ce{Be}$ and $\ce{Mg}$ and got negative marks.

The following is a quote from my book (emphasis in the original):

  The elements of Group 2 include beryllium, magnesium, calcium, strontium, barium and radium. These elements with the exception of beryllium are commonly known as the alkaline earth metals. These are so called because their oxides and hydroxides are alkaline in nature and these metal oxides are found in the earth's crust.

As you can see, it's stated that beryllium is not an alkaline earth metal!

Is beryllium an alkaline earth metal or not?