texts: Why do we not see silicon in a structure like graphite?

texts:
Silicon exists in a structure similar to diamond, with 4 silicon atoms bonded to each other in a tetrahedron.
Why do we not see it exist in a structure like graphite?

Is it even possible to get silicon to exist like this? If so could we make graphene but with silicon atoms?
Not sure why you would, since I understand carbon graphene will still be cheaper. But I would just like to know.


texts: How would substitution reaction results differ between reacting halides with a tertiary bromoalkane vs reacting it with a primary bromoalkane?

texts:
Say, you conducted two separate reactions; in one, you combined $\mathrm{50~mmol}$ saturated $\ce{KCl}$ solution with $\mathrm{10~mmol}$ 1-bromooctane (assume heating), and in the other you combined $\mathrm{10~mmol}$ saturated $\ce{KI}$ solution with $\mathrm{10~mmol}$ 1-bromoctane. In both cases $\mathrm{0.5~mmol}$ hexadecyltributylphosphonium bromide was used as a catalyst.

So, due to relative charge densities and the fact that the electrophillic carbon is primary, you would have a low yield of 1-chloroocatane vs starting material in reaction 1 and you would have a high yield of 1-iodooctane vs starting material in reaction 2, both cases obtained via SN2 reaction.

Now, suppose you would have repeated the same two reactions, only this time you would have reacted the $\ce{KCl}$ and $\ce{KI}$ with 2-bromo, 2-methyloctane, how exactly would the results differ from the results of the previous two reactions, or would they have been the same?

I know that the reaction would have no "choice" but to react via the SN1 (or perhaps E1) route, as the electrophillic carbon is tertiary and thus very sterically hindered. Also, I know that $\ce{I-}$ ions are good nucleophiles, but that doesn't matter in this case, does it?

Perhaps this reaction would go slower than the previous, owing to the fact that it requires the $\ce{Br-}$ to dissociate, and therefore there would be lower yields of both haloalkane products. But then again, wouldn't it go faster owing to the fact that it is in a polar protic solvent, and that the formed carbocation would be tertiary?


texts: It is generally said that reactants react so that they can achieve a lower energy state. Then why does a reversible reaction occur in the first place? Since turning reactants into products increases their energy - an undesirable effect from the point of view of reacting molecules.


texts: How to find how much there is of a compound given the following information?

texts:
The detailed version of the question:

If we burn a strip of magnesium in air, there will be two main products, magnesium oxide and magnesium
nitride.  If we then treat that mixture with water, the nitride ion is converted to ammonia.  After boiling away
the water and ammonia, we would be left with only magnesium oxide.  Knowing that air is approximately
78% nitrogen and 20% oxygen, we might expect that the mixture that forms in the burning process would be
a similar distribution of magnesium nitride and magnesium oxide.  In fact, the ratio is closer to 75% of the
nitride to 25% of the oxide.  Assuming that the reactions are 100% efficient (i.e., no loss of magnesium),
how much magnesium oxide was formed initially, if the final product contains 3.22 grams of magnesium
oxide?

After thinking about this for a while and working it out, it seems like the other information provided was irrelevant to finding the amount of MgO. I believe since the reactions are 100% efficient, that the final amount of 3.22 grams of MgO would be exactly the same for the initial amount of MgO, which was left over at the part when ammonia and water was evaporated. However, I am not sure; I would like to know, do the given percentages of nitrogen and oxygen given affect the unknown amount of MgO?


texts: Why do Pop Rocks fizz longer in milk than in Sprite?

texts: After doing an experiment with Pop rocks in various liquids, it was noted that they fizzed the longest in milk. My daughter compared Sprite, apple juice, water and milk, and milk fizzed the longest. Why?


texts: How does the cyclisation of the 3,6-dimethylocta-2,6-dien-4-yne occur?

texts: The given molecule is treated with $\ce{H+}$ and an acid, that is all. I know that the alkene part reacts with the $\ce{H+}$ first, but have no idea on how to proceed further. I don't see how a cyclisation takes place as the final answer given is 3,4,5,6-tetramethyl-3-cyclohexen-1-one. Any help on how this happens?


texts: Maximum Concentration of Benzene possible

texts:
A question for my PhysOrg course states:

  Assume you are performing a reaction in which benzene is a reagent. What is the maximum concentration of benzene possible? Hint: what facts do you need to know to determine concentration?

I understand concentration is amount per volume in mol/L, but I'm not sure how to proceed from there.


texts: Does dissolving an ester shift the chemical equilibrium?

texts: Esters are fairly insoluble in water , however one of the products of an esterification reaction is water , hence by washing the ester as a method of purification you are adding more water and increasing the concentration of water , would this not cause an equilibrium shift and hence result in a lower concentration of the ester ?


texts: Flame Test of Alkali Metals and Alkaline Earth Metals

texts: The flame test colors for alkali metal and alkaline earth metal salts are well known, but what about the metals themselves? Do they also give rise to the same colors (eg, brick red for Ca, pale green for Ba etc), or does it differ? And if so, why?


texts:
Does hydrogen bonding only occur between water molecules?

Is the dipole-dipole intermolecular interaction know as hydrogen bonding because it is between water molecules, or is called that because of the hydrogen molecules present in the bond?


texts: Reaction between halogens and concentrated nitric acid

texts: I have read that the reaction between $\ce{I2}$ and conc. $\ce{HNO3}$ gives $\ce{HIO3}$ and $\ce{NO2},$ but there is no mention of the other halogens' products. Do they all give halous acids and nitrogen dioxide? Specifically with chlorine, how does the reaction proceed?


texts: What is the structural formula of a monomer of hydroxypropyl methylcellulose?

texts:
I'm studying the properties of the polymer hydroxypropyl methylcellulose (HPMC) with the static scattering technique. I'm trying to interpret the molar mass obtained with a Zimm plot, that is $\pu{(3.08\pm 0.47)\times 10^{6} g mol^-1}.$
In particular, I would like to calculate the number of unites in a polymer chain, but I don't understand from the PubChem reference  what is the formula of single monomer. At the website above, I've found the formula $\ce{C56H108O30},$ but at the same site there is a molecular structure with a lesser number of carbons (about 30).
What is the formula for a HPMC monomer?


texts: How does HCl break down amylopectin in starch into amylose?

texts: I'm currently researching on manufacturing bioplastics. During one of the steps, HCl is added to break down amylopectin into amylose, but I don't understand how exactly this happens. It would really help if figures were included to illustrate.


texts: Is there an equilibruim in an unsaturated calcium hydroxide solution?

texts:
Imagine an unsaturated(No Ca(OH)2 (s) just Ca2+ (aq) and OH- (aq))  aqueous solution of Calcium Hydroxide.

Is the following equilibrium present in that solution and does the transparency of an unsaturated Calcium Hydroxide vanish after a while?

$$\ce{ Ca^2+_{(aq)} + 2OH- _{(aq)} <=>  Ca(OH)2_{(s)}}$$


texts: Gibbs free energy ΔG=ΔG°+RTln(Kp) different expressions for ΔG

texts:
ΔG=ΔG°+RTln(Kp)

If I understand it correctly, the ΔG in this equation gives the "distance" in Gibbs free energy of a chemical system at a particular moment in a reaction (encoded by the Kp) to the gibbs free energy of the chemical system at equilibrium.
So when we write this in symbols
for a general equilibrium reaction A + B <=> C + D:

ΣG(products at eq) + ΣG(reactants at eq) - (ΣG(products at k) + ΣG(reactants at k)) with k denoting a random point with certain concentrations in the reaction and eq denoting the equilibrium point.

However, ΔG is also ΣG(products at k) - ΣG(reactants at k).

So how are these two expressions for ΔG related? Basically how would you prove that

ΣG(products at eq) + ΣG(reactants at eq) - (ΣG(products at k) + ΣG(reactants at k))
= ΣG(products at k) - ΣG(reactants at k)


texts: Safety regarding multiple metals in same acid solution

texts:
My son is testing the corrosion of metals in various solutions. Is it okay to place strips of multiple metals in the same container of a specific solution?

Metals being tested: $\ce{Fe}$, $\ce{Cu}$, $\ce{Zn}$, $\ce{Al}$

Solutions:

Sulfuric acid (1 part acid, 8 parts water)
Hydrochloric acid (1 part acid, 11 parts water)
Copper Sulphate
Hydrogen peroxide


texts: What does "dye content 80%" mean on Sigma Aldrich's product page for "Allura Red AC" (aka Red 40)

texts:
Here's a link to the page:
http://www.sigmaaldrich.com/catalog/product/sial/458848?lang=en&region=US

Why does it say "dye content 80%"?
Shouldn't it be pure if it's a packaged powder?
Is it 20% other chemical compounds (e.g. stabilizers)?


texts: How come one of the hydroxides in the phosphate group are more acidic than the other?

texts:
Three phsiologically relevant $\mathrm{p}K_\mathrm{a}$ values are associated with psilocybin: 1.3, 6.5 and 10.4. Suggest the appropriate charged species and mark the $\mathrm{p}K_\mathrm{a}$ values next to the corresponding protons in your structure.

How come one of the hydroxides are more acidic than the other in the phosphate group? Is because of electron repulsion? Can the substituents on a phosphorus group not move around? Why are the two hydroxide groups on the phosphorus atom not the same functional group?


texts: Site of first protonation of imidazole and aminoimidazole

texts:
I wish to ask where imidazole and aminoimidazole will be protonated on first protonation.

Imidazole:

Aminoimidazole:

I suppose that the nitrogen (without hydrogen) of the ring is the most probable to be protonated, but I am not sure about it. Do you know where it will be protonated first?

Any link to a study where the issue is solved will be good (I need the information for my thesis).


texts:
I am extremely new to both polymer chemistry and NMR.
I am struggling with the following question:
A proton NMR is used to attempt to quantify the molecular weight of a poly(ethylene oxide) molecule with methyoxy end groups at each terminus. If the integration of the methyl protons relative to the methylene protons gave a ratio of 1:20, what can  you say about the molecular weight?

Thank you. All help is appreciate including resources for me to be able to read up on my lacking knowledge.


texts: How can I determine the highest boiling point given a list of molecules?

texts:
I know that the highest boiling point has to do with which has the strongest intermolecular force. I also know that the strongest would be ionic, then hydrogen bonding, then dipole-dipole, then london dispersion.

Can someone show me how I am supposed to solve these questions step by step though?

Am I supposed to create the Lewis dot structure for all of them and then see which is nonpolar vs. polar?

Also, once I come up with the Lewis structure, is that all I need to determine polarity? I just look to see if it's symmetric or not?

I know the 3D VSEPR shapes, so am I supposed to come up with that and then see which is nonpolar or polar?

Can someone provide me with a step by step solution as to how I can solve any of these problems from start to finish so that I have a good methodology?

Thank you!


texts: Combustion, in chemical terms, is a reaction with a certain molecule and oxygen, and it produces, energy, $\ce{CO2}$, and $\ce{H2O}$ (That's how I learned it at least). So what makes a fire'smokey'? I had always thought that smoke was simply $\ce{CO2}$, but read that it was actually the result of incompletely 'combusted' material, yet I don't fully understand what this means. Is smoke made from material that starts to combust but stops before it finishes, or does it never even begin combustion? What would the chemical reaction be of a wood (Or other similar) fire that produces a lot of smoke? And finally, is there a certain element or compound that gives smoke its 'smokey' smell?


texts: Is there a specific term for reactions of the form A + B → C + D?

texts:
I'm working with an abstract model of chemical reaction networks. In this model, some of the reactions have the form $\ce{A + B <=> C}$ and others have the form $\ce{A + B<=>C + D}$. I'm wondering if there is some existing terminology I can use to refer to these two cases.

I know that the terms "unimolecular" and "bimolecular" refer to the number of reactants, but in this case the important thing is the number of products. The ideal thing would be if there's a general term describing whether a reaction has the same number of products as it does reactants.

Alternatively, since the species I'm modelling are abstract polymers, I can use the terms "cleavage" and "ligation" to refer to the $\ce{A + B <=> C}$ case, depending on the direction in which the reaction proceeds. If there is a corresponding term for $\ce{A + B<=>C + D}$ type reactions in polymers, that would also be useful to know.

I suppose at a stretch I could call it an exchange or a substitution reaction, but (as far as I know) that tends to imply that the thing being substituted or exchanged is a single atom, rather than a whole section of polymer. (In my case the reaction might be something along the lines of $\ce{aaabb + ccdddd -> aaadddd + ccbb}$, where $\ce{a}$, $\ce{b}$, $\ce{c}$ and $\ce{d}$ are different types of monomer.)


texts: What, if any, are the differences between hemiwicking and wicking?

texts:
I'm encountering these two terms, but their uses seem to be different, and there's little documentation out there defining the terms.

Here is an example definition I've found of Wicking:

  Wicking is the spontaneous flow of a liquid in a porous substrate, driven by capillary forces.$^1$

Here is an example definition I've found of hemiwicking (notice little difference between the one above):

  Hemiwicking refers to the spreading of a liquid on a rough hydrophilic surface driven by capillarity.$^2$

Below is a typical depiction showing Wenzel wetting (a), Cassie-Baxter wetting (B), and hemiwicking(c).$^3$ My assumption would be that Wenzel wetting would actually be an example of wicking?

http://journals.sagepub.com/doi/abs/10.1177/004051759606601008
http://fluids.snu.ac.kr/Publication/hemiwicking.pdf
http://jss.ecsdl.org/content/3/1/N3095/F3.expansion.html


texts: Temperature relation for isomerism reactions

texts:
When we have an isotherm isomerism reaction
$\ce{A(g) -> A^*(g)}$  with $\ce{ΔH^0 = 0}$
is the ratio of preassures $\ce{P_A^* / P_A}$ independent from temperature?


texts: Gelatination of solution in saponification

texts:
When I performed a saponification experiment in school, I added some ethanol to the solution (glycerol ester fatty acid + sodium hydroxide) to change the equilibrium of the reaction. (Molecules of salt of fatty acid made some chunks so they don't react efficiently.) But accidentally I spilled a lot of ethanol and the solution became hard, like a hair gel. And after I added some water to it, it became liquid again.

What I want to know is why the solution became a gel. I know that ethanol is used for an efficient reaction because ethanol can be a common solvent of grease and water and it can help sodium hydroxide and glycerol ester meet, but I don't know why they became harder when ethanol was overused.

Of course, the solution was in the water bath.


texts: Extent of dehydration by concentrated sulphuric acid

texts:
I know that conc $\ce{H2SO4}$ is a dehydrating agent. And the most easiest mechanism for example would be this:

But I want to know how to find the extent of dehydration of it.
I came across this question:

And the answer is:

 d

My thinking:
(a) $\ce{O}$ is EN and will pull $\ce{-OH}$ towards itself inductively, thus decreasing the electron density on $\ce{-OH}$, and decreasing its power to pull $\ce{H}$ from concentrated $\ce{H2SO4}$.
Similarly for (b) and (c) and I think due to inductivity (c) will have more chances than (b).
As for the (d) I think $\ce{-CH3}$ group is an electron pusher so it should increase the electron density, and hence reducing the effect on $\ce{-OH}$ group .
1) But my doubt is: is this the only reason for the extent of dehydration by conc $\ce{H2SO4}$ on (d) to be more than (c)?
2) I don't think there would be much difference if it tautomerises to enol form.


texts: Rule of mutual exclusion: is the converse true?

texts:
There is a "famous" rule in spectroscopy,1 that goes this way:

  If a compound is centrosymmetric, then its normal vibrational modes cannot be simultaneously IR and Raman active.

and this is simple enough to prove: for a vibrational mode to be IR active, it has to transform under the same irrep as (one of) the cartesian axes $x$, $y$ or $z$, which are all ungerade. For a vibrational mode to be Raman active, it has to transform under the same irrep as one of $(x^2, y^2, z^2, xy, yz, xz)$, and since $u \otimes u = g$, these irreps cannot be the same as the irreps of $(x,y,z)$. Hence, a vibrational mode, which transforms under a single irrep, cannot simultaneously satisfy both conditions at once.

However, I am curious about the converse statement.

  If a compound does not have any vibrational modes which are simultaneously IR and Raman active, is it necessarily centrosymmetric?

If the answer is yes, I would like a proof; if it is no, a counterexample, please.

(Just in case anybody is confused, because I am: A counterexample would be a molecule without a centre of inversion, which has no vibrational mode which is simultaneously IR and Raman active.)

1 Famous enough for me to know, at least.


texts:
I have recently starting distilling my own essential oils using a still that I built out of an old diesel barrel. Before the first run with the still, I cleaned the inside using soap and water. I distilled until I created 5 gallons of hydrosol. The issue is that it seems that the oil and water are emulsified (hope that is the right term, I don't have a background in chemistry). There appears to be a thin film of oil on the surface, rather than the "globs" I would expect. Another reason I believe this is an emulsion is that no matter how much I skim off the top, that film is always present, making me think that the oil is thoroughly mixed in the solution.I have done some research and it seems to be that there may be a surfactant present that is causing this.

Is there a way that I can test for the presence of a surfactant?

Does it sound like my issue is the presence of a surfactant or something entirely different?

Could the soap I used to clean it be the surfactant?

Thanks!

Update in Response to Answer:

The end goal is to use a few drops of the oil to enhance the smell of a facial product (beard oil), so the end product has to be safe for skin.

I don't have a diagram at the moment, but here is a smaller still that is basically the same as my setup, just much smaller. I am using a propane heat source to control the temperature.

To be honest, I don't know the expected structure of the oils. This is my first attempt at anything like this (I'm a software engineer that recently acquired an interest in chemistry!).

Thanks for the help!


texts: Why does water diffuse from a lower solute concentration to a higher one?

texts: I'm studying biology and this came up in the context of passive transport. I understand why, in general a gas moves down a concentration gradient (the random movement of gas particles and probability). But I don't understand why the concentration of some solute (ions, salt, etc) would affect the movement of water. Why does water move from an area with a lower concentration of solute to an area with a higher concentration of solute?


texts: Polysytrene factories and hypothetical health concerns

texts:
Background/Research so far

I'm actually not much of a chemist at all; but I'm doing research for a book I'm writing.

The events of the story begin from a factory that produces/supplies jewel cases for cheap CDs. This factory then pollutes the city's water by reckless dumping. Basically I'm a psychopath and I want to give my city's citizens harmful affects that are revealed after 15 years. Maybe their livers melt or something.

I learned that these jewel cases are made from a plastic called polystyrene.

From this website, I found this:

  Polystyrene (PS, #6): styrene, ethylbenzene, benzene, ethylene, carbon
  tetrachloride, polyvinyl alcohol, antimony oxide, and tert-butyl
  hydroperoxide, bensoquinone

I thought maybe the pollution could be caused by leftover ingredients for the plastic used in the process.

I then examined carbon tetracholoride ($\ce{CCl4}$). This seems really harmful and may cause long term damage if accidentally ingested, especially to the liver. So this sounded exactly what I am looking for. However, I'm not sure how realistic/true this is because further research showed that $\ce{CCl4}$ is, in fact, so harmful that it's rarely used anymore. So it seems like it may be unrealistic to use in the story, because maybe the above article is inaccurate and $\ce{CCl4}$ is not that prevalent.

Benzene also is an obvious one, but it seems to mostly cause blood cancer (leukemia) through ingestion. For reasons that occur later in the story, isn't really isn't going to work. I was kind of looking for a specific organ failure/problems/cancer and not those that effect blood and/or skin.

Ethylene also looks promising because it's so close to ethylene gylcol, and ethylene glycol would really mess people up (it is my understanding is that it's basically antifreeze). But further research indicates that ethylene isn't very harmful at all.

I also thought of cleaning agents for polystyrene instead of actual ingredients. And it sounds like $\ce{CCl4}$ comes into play again because it's used as a "dry solvent," according to Wikipedia in "Historical Uses".

Question

I'm starting to fall short in research and I want my story to be as facutal as possible. So I'm wondering which chemicals would be the most realistic in terms of use in the practical manufacture of polystyrene that could be dumped a really cause problems health-wise for a city.


texts:
How can phenoxyacetone be synthesized from phenol?

My Attempt:

We would first need to deprotonate phenol by addition of NaH in THF and then add bromopropene.

I'm not quite sure where I would go from here. Any help would be much appreciated!


texts:
$R$ is the universal gas constant equaling $8.314\ \mathrm{J/(mol\ K)}$.
$k$ is the Boltzman constant equaling $1.38\times10^{-23}\ \mathrm{J/K}$.

$$R=nk$$

$n$ is no. of moles.
$n$ can change.
$R$ is a constant, $k$ is a constant,  but $n$ changes. Then how is $k$ a constant?
Is the equation correct?


texts:
I am reading some papers about quantum chemistry and in one I found a notation for excited states of a molecule that I don't understand at all.

In the picture below you can see the potential curves of biphenyl as a function of its torsion angle. In the description of the picture, the author speaks of states $1^1A$ and $1^1B_1$. What does he mean by these states?


texts:
Do you know some books or articles that elaborate on the chemistry behind fertilizers?

I have taken organic chemistry so far, and  inorganic chemistry as well. I am also familiar with the Haber-Bosch process.


texts: Does the Nernst equation suggest voltaic cell voltage remains constant over time?

texts:
Say the following reactions are occurring in my voltaic cell:

$$\ce{Mg->Mg^{2+} + 2e-     +2.36V}$$
$$\ce{Cu^{2+} +2e-->Cu     -0.34V}$$

Then, the Nernst equation would become:

$$E_{cell}=2.70-\frac{RT}{nF}ln\frac{[Mg^{2+}]}{[Cu^{2+}]}$$

However, if the initial volumes and concentrations of the copper and magnesium solutions were equal, the fraction within the natural logarithm would constantly equal 1.

Does this mean there is no change in voltage as the concentrations decrease, or did I understand something wrong?


texts: Nanoparticle tracking analysis v.s Transmission Electron Microscope

texts:
I have various bimetallic nanoparticles which have formed alloys.
I then used NTA and TEM to characterize the size of my nanoparticles.
The TEM shows that the size of nanoparticles is considerably less than the NTA.
Can anybody help explain the difference in size?


texts: Why do we begin an experiment involving solutions of different concentration from the least concentrated solution?

texts:
Is there a particular benefit to start any kind of measurement with the least concentrated solution and then work my way up to the more concentrated solution?

In one of my experiment, we measure the UV absorbance value of a solution beginning with lowest concentration. Weirdly, the demonstrator did not clean the apparatus and simply rinse it with higher concentrated solution that is to be measured.


texts:
I am very much confused: in the cell (Zn, Cu in $\ce {H2SO4}$), Cu is positively charged and is anode, where in this cell (Zn in $\ce {ZnSO4}$ and Cu in $\ce {CuSO4}$), Cu is positively charged but is Cathode. So how can I define it, where both are electric or voltaic cell. Please help me. Please see these picture for better understanding.

reference:A Text Book Of Electrical Technology,Volume 1,B.L.Theraja


texts:
I'm trying to make a Bismuth-Indium based low-melt alloy wetter (specifically, better at wetting to solid metals and glass). I've tried adding gallium, which obviously works, but due to its metal-attacking nature it can't be used here.

I know that antimony and tellurium are often used as surfactants, but I've only read of them acting as surfactants in organic solvents, and can't find anything on whether alloying them with a liquid metal would improve its wetting ability. As I don't have any Sb/Te at present, I'd rather ask if this has any chance of helping before trying them.

If not, is there anything else I could incorporate into the alloy - possibly a non-metal/metalloid - which would improve wetting?


texts: How to determine which gas is more soluble

texts:
I have a chemistry homework problem that asks whether $Br_2$ or $O_2$ is more soluble in water in room temperature. However, I can't seem to find a way to figure it out, short of looking it up.

Is there a guiding rule for such figures, such as relating to molar mass?


texts: Effect of anisotropy on electrical conductivity of crystalline solids

texts:
I was reading through a chapter named 'Solid state' in the NCERT Chemistry book.
I learnt about anisotropy of crystalline solids.
And what I understood was, you measure a certain property of that solid in one direction and it could be X while you measure it in the other direction it could be Y.
I then learnt about how a solid could show the property of birefringence.

My question : So does that mean, even electrical conductivity isn't the same in all directions? Does that mean a copper wire is going to conduct differently in different directions?
How is that possible? It feels impossible?
Does that mean different copper wires conduct differently?

I understand the last part is like a chunk of questions altogether and our community doesn't like that, but then it is basically having the same origin with just a little counter questions kinda? so I just let that be. I believe the contributors can understand what confusion I'm dealing with if I ask it like that.


texts: When classifying the molecules in symmetry point groups some non-principal rotation axes $C_2$ and some reflection planes $\sigma_v$ and $\sigma_d$ are primed or double primed, like $\sigma_v'$, $\sigma_v''$, $C_2'$ or $C_2''$. What determines which is the unprimed, primed or double primed $C_2$-axis/$\sigma_v$-plane, or is it arbitrary?


texts: If you have an ice cube in water and the ice cube does not melt after reaching equilibrium with the water, does the water have temperature 0 degrees Celsius?


texts: How to make spectra smooth by using gaussian or lorentzian function

texts:
I want to use some origin spectrum to fit to my experimental spectra. However, my experimental spectra is not so smooth because of finite resolution of spectrometer. I used to use 'origin' to make it smooth, but it seems not reasonable because I don't know how 'origin' makes it. Then I was suggested using Gaussian or Lorentzian function.
A lot of nonsense, in one word, please teach how to use gaussian or lorentzian function.


texts: Heat of reaction for the decomposition of AgCl means?

texts:
Certain sunglasses have small crystals of $\ce{AgCl}$ incorporated into the lenses, on exposure to light of appropriate wavelength produces a grey colour to reduce the glare following the reaction:
$$\ce{
  \underset{(colourless)}{AgCl}
  ->[h\nu]
  \underset{(grey)}{Ag} + Cl
}$$

If the heat of reaction for the decomposition of $\ce{AgCl}$ is $\pu{248 kJ/mol}$, what maximum wavelength is needed to induce the desired process?
Does this mean that by absorbing only a certain wavelength, electrons move for a lower to higher energy state and react?
Why does it only emit grey light, but does not any colours of the spectrum in order?
The question asks about the "heat of decomposition".  Does this mean the energy required to excite an electron and cause a reaction?
When a molecule absorb a photon, it is breaking the atoms apart by  moving electrons?
Please help clear up any misunderstandings in this question.


texts: What exactly are the graphs of orbitals?

texts:
In my QM class we are finding the wave functions of the hydrogen atom. In spherical coordinates, these wave functions are functions of 3 variables: $r,$ $\theta,$ and $\phi.$ My professor stated that "the wave functions of the electron are called orbitals".

Say, we are interested in the $l = 0$ (or s-orbitals). Since $l = 0,$ $m = 0.$

$$\psi_{n00}(r,\theta,\phi) = R_{n0}(r)Y_{00}(\theta,\phi) = \left(\frac{1}{4\pi}\right)^{1/2}R_{n0}(r)$$

So, we can set a specific $n$ value. Say, $n = 1,$ and we get the the corresponding 1s orbital. Since we set an $n$ value, the wave function reduces to a function of the radius $r.$ During the lecture, he said that this image:

is an isosurface (or level surface) of the wave function at a constant radius.
I interpreted that as finding the isosurface of a 4D graph, our wave function, at some radius. This isosurface is the the sphere in 3D. What confused me was when he stated that the graph was an "isosurface of the full orbital".

What does he mean by the "full orbital"? Is this "full orbital" something in 4D space?


texts: Is there a nomenclature for linear alkanes with n carbons?

texts:
Is there a common nomenclature (not necessarily IUPAC) for naming linear alkanes with $n$ carbons without resorting to Greek/Latin numerical prefixes (hex-, hept-, etc.)?

For instance, is there a name for the higher linear alkane of $\mathrm{50}$ carbon atoms other than n-pentacontane? ("Not necessarily IUPAC" is meant in the same sense that $\alpha$, $\beta$, and $\gamma$ nomenclature  don't follow IUPAC rules but are nevertheless often used to designate relative positions of carbon atoms)


texts: Why is aniline less basic than methylamine?

texts:
The reason given for the question is that in aniline the lone pair on N atom is delocalized throughout the benzene ring, making it less available for donation.

But the conjugate acid of aniline should be more stable given the fact that the positive charge on N atom is also delocalized throughout the ring, hence making it more stable than the conjugate acid of methylamine which has +I effect. On that account, shouldn't aniline be more basic?


texts: Mechanism of polymerization of 4-nitroaniline

texts: Does anyone know the mechanism for/the structure of the product of the explosive polymerization of 4-nitroaniline with concentrated sulfuric acid? My guess is that it is some sort of aromatic substitution reaction, leading to a number of benzene rings connected by nitrogens.


texts: Can you get oxygen form silica or alumina?

texts: If I had a lot of silica or alumina, like on the moon, would I be able to split the silica or alumina into aluminium and oxygen/ silicon and oxygen? It doesn't matter how unpractical it is. If there is a way, how can it be done?


texts: QM modelling of charge separation reactions

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I have a general question regarding the modelling of reactions in which neutral reactants form charged species/ions (in solution). How can one get the energetics approximately right on reactions like thes? Examples would be very simple acid/base reactions like
$$\ce{NH3 + HCl -> NH4+ + Cl-}$$
but also more complex reactions like
$$\ce{Ru(CO)H2(PPh3)3 + HCl -> Ru(CO)H(PPh3)3+ + H2 + Cl-}$$

Important contributions that I can think of, but do not seem to be sufficient in many cases, are:

Solvation. Some correction must be applied to account for solvation effects of the ions. I usually try to obtain corrections to $\Delta$G for this from COSMO-RS, and the solvation energies are a lot higher than for neutral species, but still seem to low. It is hard to judge whether these corrections are good, since for most of the interesting cases no data on solvation enthalpies in certain solvents etc. exists.
Diffuse functions. For better description of anions, diffuse functions in the basis set can make a difference. However that change also seems to be small when the basis set is already large (say def2-QZVPP to def2-QZVPPD), and for very large basis sets, the computational cost is also considerable.
Coordination sphere of ions. Many (smaller) ions probably have a special coordination sphere, which also depends on the solvent, and may form aggregates or oligomers. For new species it's quite likely that solution structure is not known, but even for seemingly simple cases (for example $\ce{NaOMe}$ in $\ce{MeOH}$) it is hard to find data.

Are there other things that should be considered? What is a good "standard" protocol to deal with these kinds of reactions?


texts: Is the Gibbs standard free energy always constant?

texts:
I am a biochemistry student and we are learning about thermodynamics. Is the Gibbs standard free energy for a reaction always constant? The equation below suggests that it changes with temperature:

$$\Delta G^{\circ\prime} = -RT\ln K'_\mathrm{eq}$$

It is important to note that we are using the biochemistry version of the Gibbs standard free energy equation. To answer my own equation, I believe that it is always constant. Changing the temperature would probably just change the equilibrium constant.


texts: Symmetry and stability of a molecule (Jahn-Teller Distortion)

texts: I've taught in my class that if a molecule posses high degree of symmetry it's stability will be more,in other words symmetry and stability are directly proportional. Is this statement correct? And if this is correct than why Jahn teller distortion stabilizes a molecule when it's symmetry gets low eventually because of the distortion.


texts: Is there a mathematical basis behind the HSAB theory?

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I learnt about the HSAB concept about a year ago, and found that it helped rationalise many of the solubilities/reactivities that “pure” Lewis acid/base theory could not.

Is there a mathematical basis behind Pearson’s theory, or was it just an empirical observation?


texts: How to wedge d/hash notation a molecule?

texts:
This is probably trivia for many of you (I already feel the pressure by even posting this question). Yet funny enough, most of the time the materials I have come across show the wedge-d/hash notation. Then due its cumbersome or what not, the material decides to propose Fisher project as a better notation. But frankly that doesn't give the proper picture of the stereochemistry or least understanding of how the atoms would arrange in space.

When revising Rectus-Sinister (R/S) system for stereochemistry, it has almost always indicated about assigning priority to the groups by descending order of the atomic number and that lowest priority substituent should always point away from the plane of the central atom. Speaking of a simple molecule like $\ce{CH4}$, Wedge-Dash is ideally suited to show structure of sp3 hybridised (tetrahedral atoms).

But what about more complex compounds/molecules like amino acids or things like drugs like morphine etc? or even an imaginary molecule given in exam? I dread at the thought of it.

I went through this question for few days now, before posting this question. Perhaps it has more advanced perspective compared to the simplicity of my question I think.

So are there direct guidelines to draw the wedge-h/dash notation for a given complex molecule? Am I really missing something from preliminary general chemistry here?

Obviously there are online applets that allow to get a SMILE of a molecule and generate the 3D structure like JSmol. I also know there are complex methodologies employed in higher level of physical science to determine the structure of molecules. But at this beginning level, is there anyway to determine the 3D structure of a molecule? At least to get a feeling of it, and to predict that what atom/side chain would pop out of plane and remain in the plane?

I am a beginner in Chemistry, so should I really bother about this at all?


texts: why don't carbons use sp3 instead of sp2 orbitals to make double bonds?

texts:
I don't have a strong chemistry background, but I was thinking why do carbons have to make different kinds of orbital hybridization for double and triple bonds?
Why doesn't a carbon make two sigma bonds into a double bond?


texts: How to convert chemical rate of reaction into time?

texts: I am very new to chemistry. I am using a simulator for knowing rate of chemical reaction whose unit is $\mathrm{(kmol/m^3)/s}$. I want to convert it into time taken only. I have got concentration of each chemical can I convert it into time.


texts: Is it possible that diamond can be grown from aqueous solutions?

texts:
Assume a cubic diamond crystal with hydrogen-terminated surface bonds. The terminating hydrogen atoms will form pairs that are geometrically close together in alternating diagonal pairs (think of the rectangles on corrugated walking steel).

Next, picture a formaldehyde molecule being pushed oxygen-first into one of these terminating hydrogen pairs. If the oxygen atom can be made to react with the hydrogen pair, a water molecule would be expelled and the remaining $\ce{CH2}$ group would presumably bond to the two bonds of the diamond lattice.

If you repeat this process over the entire cubic face, the result will be a new layer of diamond that is terminated with the same paired hydrogen atoms as the original layer. The entire layer-growth process thus in principle could be repeated indefinitely, resulting in a diamond grown at or near room temperature from an aqueous or other low-temperature solution.

Question: Can anyone think of a fundamental reason why the above process, or some variant of it, could not be used to grow diamond crystals at room temperature? (A "variant" might start with carbohydrate units larger than $\ce{OCH2}$, for example.)

One or more geometrically sophisticated catalyst molecules would be required. Each catalyst molecule would snag, carry, and orient a formaldehyde molecules onto some part of the textured surfaces provided by the cubic diamond face, such as the face itself or along a growth edge.

I did this a long time ago in high school, but my recollection is that the reaction should be mildly exothermic. But even if it is not, energy-source molecules (think of the role of ATP in living systems) could provide energy to enable an endothermic reaction.

So... thoughts, anyone? Is there any deep reason why this approach to room-temperature or near-room-temperature diamond synthesis is clearly not possible?


texts:
What methods are there to produce this compound? What are its properties as a component of automobile petroleum? How does it impact on detonation resistance of automobile petroleum?

I think that the title compound might be produced from catalytic cracking of petroleum. But I don't have a clue of what methods are there to produce exactly this specific compound. I also think that it helps to increase the detonation resistance of automobile petroleum but I can't explain why. So I'm seeking for the explanation. Surprisingly, there's nothing on the Internet, so this site seems to be the only place where I can possibly find some information.


texts: How does the number of electrons increase in beta decay?

texts:
So, I am having trouble understanding beta decay. Particularly the number of electrons.

For example; Carbon-14 decaying into Nitrogen-14.

Carbon-14 has 12 neutrons, 6 protons and 6 electrons.
When it decays 1 neutron is converted into: 1 proton, 1 electron and 1 anti-neutrino.

So after the neutron breaks down, and before emission, there should now be:
11 neutrons, 7 protons, 7 electrons and 1 anti-neutrino.

But now 1 electron is emitted from the atom (as a beta ray), alongside the anti-neutrino. Which means the numbers should now be:
11 neutrons, 7 protons and...6 electrons.

Since 1 electron is created in the process and 1 is emitted out of the atom, then surely the number of electrons shouldn't change from the original 6 of carbon-14.
But Nitrogen-14 has 7 electrons?? Can someone explain?

Thanks.


texts: How to treat Magnesium powder and ribbon

texts:
I am a master student of nuclear physics. Due to some measurements I'd like to make, I have to use Magnesium as a beam target. Searching through the net to see it's properties I found that it can be easily oxidized. In addition I've read that it's highly flammable.

I have in hand two forms of Magnesium:powder and ribbon. In order to make the targets I have two alternatives.

Use the powder to make highly pressured pellets. I thought of flushing a bottle with Argon or Nitrogen, making the pellet as fast as possible using this procedure(which involves acetone) in the atmosphere and then after the pellet is formed put it in the Argon or Nitrogen bottle.
Use the ribbon as is. The only problem is that it not wide enough, so I will have to make a spiral of this ribbon around something(I don't yet know what the "something" will be, so any idea is welcome!). The ribbon I have has a width of 3mm but I want a width of 6mm. So I thought of spinning the ribbon around an item, to form a spiral.

The goal is to make the target as safely as possible and avoid Magnesium oxidizing, because I don't want to have Oxygen in my target. So my question has three parts.

How to safely treat magnesium powder/ribbon so as to avoid any possible accident and preventing it from oxidizing?
Which of the above would be the most effective way to make the target?
How to store the target until the experiment will be held?

Note that after the target is made, it will go to an evaporator, in order to evaporate some gold. Any advice, help or direction is more than welcome!


texts:
After investigating what makes the persistent radical TEMPO stable, I was wondering if another compound which is more feasible for my needs would be comparable to it.
Would oxidizing 2,2’-dimethyl-diphenylamine result in a compound similar to TEMPO? It will have an Aminoxyl group and have the steric hindrance of the methyl group next to it. By similar I mean if it will have a stable radical in the aminoxyl group.


texts: Chemical equation for the reaction of Allura Red AC with NaClO

texts:
I am trying to figure out the chemical formula for the reaction between Allura Red AC and $\ce{NaClO}$ (bleach). I have never met such reactions before in my study, and I was unable or maybe looked in the wrong places, to find the chemical equation for the reaction. The closest thing I have found is an image with the reaction but without the chemical equation. Could somebody please help me figure out the chemical equation for the reaction in the image?

Thanks for the help in advance.


texts: Theoretical temperature change in lime hydration

texts:
Calcium oxide (quicklime) and water have an exothermic reaction

$\ce{CaO + H2O \rightarrow Ca(OH)_2} \quad \quad \Delta H^{\circ}_f=-65.3 \;  \mathrm{kJ \cdot mol^{-1}}$

Assume that I have 1 kg of lime which means that I would theoretically need 322 grams of water for complete hydration. However, I want to use different amounts of excess water and calculate the final temperature of the whole system after the reaction has finished.

The heats of formation are given at the standard temperature in the tables. Therefore, if I assume that the calcium oxide and water start the reaction at 25 °C I know that 65.3 kJ of heat per mole of reacted $\ce{CaO}$ has to be transferred to the $\ce{CaO}$/$\ce{H2O}$ mixture. With 1 kg of lime (molar mass of $\ce{CaO}$ is 56.08 g) this would mean 1164 kJ of energy released.

So, if for example 1 kg of water was added, the final mixture would consist of 1.322 kg of $\ce{Ca(OH)2}$ and 0.678 kg of $\ce{H2O}$. Using the specific heat capacities the heat capacity of the total system could be calculated and the final temperature rise obtained.

Now, assume that I want to take into account the effect of adding reactants at different temperatures. Say that my slaking water is 16 °C and the lime 35 °C. Should I first calculate the initial temperature by assuming that the reactants do not react until the temperature difference between the lime and the water has settled?

I obtained the heat capacities from here: http://www.update.uu.se/~jolkkonen/pdf/CRC_TD.pdf

$\ce{H2O}$ heat capacity 75.3 J mol$^{-1}$ K$^{-1}$ $\rightarrow$ 4.18 kJ kg$^{-1}$ K$^{-1}$

$\ce{CaO}$ heat capacity 42.0 J mol$^{-1}$ K$^{-1}$ $\rightarrow$ 0,749 kJ kg$^{-1}$ K$^{-1}$

$\ce{Ca(OH)2}$ heat capacity 87.5 J mol$^{-1}$ K$^{-1}$ $\rightarrow$ 1.18 kJ kg$^{-1}$ K$^{-1}$

The amount of heat is calculated from

$Q=cm\Delta t$

If I use the arbitrary initial temperatures of 16 °C for water ($t_1$) and 35 °C for the lime ($t_2$), and initial weights of 1 kg the starting temperature of the system without reaction would then be obtained from

$c_1 m_1 (t-t_1)+c_2m_2(t-t_2)=0$

and solving for final temperature $t$

$t = \frac{c_1m_1t_1+c_2m_2t_2}{c_1m_1+c_2m_2}=18.9 \;°C$

I would then calculate the heat of the reaction, account for the reduction of water and the formation of $\ce{Ca(OH)2}$ and finally calculate the heat distribution and the final temperature.

Is this the proper approach to this problem? How large error is made if the starting temperature of the reaction is not the normal temperature of 25 °C? The temperature range I am interested in would be between 10 °C and 100 °C.

The recommended final temperature for wet slaking is about 71-93 °C. Here I assumed that all of the quicklime reacts and none of the heat is lost to the environment. The reaction rate is dependent on the temperature and in too cold conditions (too much excess water) the hydration can be incomplete as the lime is "drowned". My ultimate goal is to create a model of a slaker and use it to improve the temperature control of a milk of lime plant.


texts: How to calculate the emission wavelength of a substance?

texts:
A light photon (700nm) gets absorbed by a substance*, this substance than emits the light photo.

How to find out the wavelength emitted by this light photon?

*substance can be anything, I've just used the beryl mineral as an example


texts: What is Sn valence in this case? Because  it depends on it if it will be linear or tetragonal.I'm talking about a molecule.


texts:
I was taught to balance redox equations with acid/base considerations. Instead of arbitrarily adding $\ce{H^+}$ and $\ce{HO^-}$ ions and memorizing separate rules for acidic and basic solutions, I was taught simply to keep these four things in mind:

1) Charge must be conserved.

2) Mass is similarly conserved.

3) Do what's thermodynamically more favorable. For example, in strongly basic solution, $\ce{O^2-}$ oxygen ions come from not hydronium ion (because that doesn't exist in significant quantity in basic solution) and not from water (because that requires heterolytic clevage of 2 $\ce{H-O}$ bonds but instead $\ce{HO^-}$ because that only requires clevage of only one $\ce{H-O}$ bond.

4) Strongest base reacts with strongest acid.

On the other hand, here's a gem from Chem Wiki by UC Davis:

My question is:

1) How come I've never seen my professor's method mentioned anywhere? I've Googled, looked at scholarly papers; looked in advanced analytical textbooks, etc.

2) How were you taught?

3) Which way do you think is more advantageous?


texts: Do non-ergodic chemical reactions exist?

texts:
Do reactions whose final outcome is not even theoretically predictable by any means possible exist in Nature or does the outcome of all possible chemical reactions can (at least in theory) be predicted if we could get enough information about the conditions the reaction system is in?

My question isn't about a well-defined reaction system whose behavior is unknown to a certain degree but about the possibility in principle to discover a chemical reaction or a system of chemical reactions able to produce compounds which can't be predicted even in theory, even if we manage to acquire all the possible information about the system that can be acquired by all experimental means possible? What I want to ask is whether we can, at least in theory, know all possible products a reaction system can generate or do we "hit a wall" limiting our ability to predict certain chemical reactions over a certain limit?

I know very well the difference between a stochastic and a deterministic process, but what I'm asking isn't about stochasticity. It is about the possible predictability of all chemical reactions that could exist. As far as I know if we use the concept of stochasticity we may be able to derive possible, albeit only probable predictions about the state the system can be in. Therefore we can at least compute some probabilities different compounds can have to emerge under certain conditions. What I'm asking about is the validity of the concept of ergodicity, therefore I want to know is it possible to know the end state and all the reaction products of all possible chemical reactions, or there are some which could generate products that are impossible to predict in both theory and reality? Do reactions generating such unpredictable behavior exist in the real world or are they possible only in theory?


texts: Which of the five conformers of propyl propanoate is most stable?

texts:
I've worked out five different conformations of propyl propanoate:

I think the bisected conformations (E) should be the most stable one.

Are my rationals and suggestions in my scheme correct?


texts:
Consider the following Ellingham diagram.

At 673K, the Gibbs energy value of oxidation of Zn is more negative than the Gibbs energy value of oxidation of C (coke). So, Zn should be oxidised to ZnO. But in various sources like the textbooks of class 12 of CBSE (India), it is mentioned that ZnO is reduced to Zn and C (coke) is oxidised to CO at 673K in the reaction between ZnO and C. Looking at the Ellingham diagram, coke should not reduce ZnO to Zn at 673K.

So why is ZnO is reduced to Zn in this case?


texts: Order of −I effect among ethenyl and 1-propenyl groups

texts:
We know that both ethenyl $\ce{-CH=CH}_2$ and 1-propenyl $\ce{-CH=CH-CH3}$ are electron-withdrawing groups when attached to hydrocarbon chain. Which one has greater electron withdrawing power?
The $\ce{-CH3}$ is electron-donating, hence allyl should have lesser electron withdrawing effect. Is this correct?


texts: Is there any electronic component to water conductivity?

texts:
Answers to Decrease in temperature of a aqueous salt solution decreases conductivity indicate that the electrical conductivity of salt solutions arises from the mobility of ionic species and therefore the temperature dependence of conductivity is related to viscosity.

Question: Is there any measured or predicted electronic component to water conductivity as well, where the charge carriers are electrons rather than ions?

This could take place via charge exchange (migration of bound electrons) or even perhaps via solvated electrons, or some other mechanism.

In this case I'm interested in both pure water, and salt solutions.


texts: Why do Allylic Halides prefer SN2 reaction over SN1?

texts:
As explained by my instructor,

  Allylic Halides form highly stable Transition States. They are stable because they are:

  $sp^2$ hybridized
  possess a conjugated system of pi bond and empty p orbital

However, if we consider the $S_N1$ mechanism, a carbocation intermediate is stabilized by resonance. Why is the formation of the transition state more favorable than the formation of the resonance stabilized intermediate?


texts: Calculating entropy change of surroundings

texts: I have seen many similar questions but have not found my answer. Why do we use the actual heat involved in the process to calculate entropy change of surrounding? The only answer I can think of is that we are treating the process as reversible with respect to the surroundings even if it is irreversible with respect to the system. But, this is an irreversible path for the system, and a reversible path will not involve the same heat, so now, the entropy of surrounding calculated must be different. This seems to contradict the idea that the entropy of surroundings must be a state function. So why is this reasoning incorrect?


texts:
Find the number of stereoisomers of the following compound:

I think the answer is 16:

The double bond in the ring cannot show geometrical isomerism.
The first double bond on the top substituent can show cis-trans isomerism and the one on the end will not show cis-trans isomerism because of two same groups on one carbon.
The substituent on the bottom that is: $\ce{-CH=C=C=CHMe}$ can also show cis-trans isomerism.
Then, there are two chiral centres and the number of optical isomers is $2^2=4$. The total number of stereoisomers is 16.

But the answer given is 4. Am I correct or not?


texts: Is there any law for pH conservation in chemical reactions?

texts:
I would like to know (just curiosity) if there is any law for pH conservation in chemical reactions. (like conservation of momentum in dynamics).

EDIT

The reaction I would like to take as example is fuel combustion. Too many sources (mostly media) stating that acid products (NOx and COx dissolved in water) are obtained.

My idea is that acids cannot be created from nothing. Either the inputs of the reaction were acid or the output is not only acid but also basic outputs.
Thus the question whether this reasoning is true.


texts: Why does the following "Battery" experiment work?

texts:
I did the following experiment:
Experimental setup:
Two electrodes (one made out of Iron,the other made out of Copper)
are put into a (bluish) Copper(ii) sulfate lotion.

Then, one connect a voltmeter to them to measure the potential.

Finally, one disconnect the voltmeter and connect an Amperemeter to measure the electrical current.

Observations:
-Copper accumulates around the iron electrode,forming a thick copper coloured slick around it.
-there is a potential of about 0.5 V between the electrodes, which stays for several minutes.
-when one connect the amperemeter, one can measure a current which stays at least for a few seconds. (didn't measure further)
-there is no (visible) activity around the copper electrode.
-the solution doesn't change its colour notably.
-especially, one could not observe any evolution of gas. (although this does not mean that there is absolutely no gas evolution)
How is the measured tension and current caused?


texts: Does diamagnetic anisotropy only apply to a proton bonded to triple bonded carbon?

texts:
Lecture tells me that double bond, with the sp^2 bonding will have more s-character, which will hold the electons closer to nucleus, which means a more deshielded proton which means downfield chem shift.
But it doesnt follow the same idea with triple bond, with sp bonded carbon, and this is where diamagnetic anisotropy becomes a factor.... But is D.A. a factor with double bond also and why? Thats what I dont understand, because both double and triple will have pi bonds.. thanks for any help


texts: Salts that are more hydrophilic than NaCl

texts: What other, rather easy to obtain, salts are more hydrophilic than $\ce{NaCl}$? Is there a hydrophilic scale for substances like the Mohs scale of mineral hardness?


texts: Prevent molten glass from cracking when cooling down

texts:
My mother works in a ceramics workshop. Besides giving lessons she creates various ceramic dishes, cups and plates. She often uses the effect of colored glass melting in the product and then leaving beautiful patterns at the bottom.

However it always cracks a lot as cooling down. Sometimes, it looks good when it's cracked, but other times she's trying to make it look like a gem - and cracked gem is not very gemmy.

So I was curious if there is something non toxic, insoluble in water and alcohol, that would melt at the similar temperature as glass and would prevent it from cracking in the cool down phase.

The glass doesn't have to be temperature resistant in the final products. We just want to avoid the cracks


texts: Relation between ionic resonance energy and polarity

texts:
The ionic resonance of the bonds are given as follows:

  $$
\begin{array}{cr}
\ce{A-B} & 24.3 \\
\ce{A-C} & 50.6 \\
\ce{A-D} & 102.3 \\
\ce{A-E} & 105.9
\end{array}
$$

  Which of the bonds is the most polar?

  a) $\ce{A-B}$
  b) $\ce{A-C}$
  c) $\ce{A-D}$
  d) $\ce{A-E}$

I thought that more the resonance energy, more is the electron delocalisation and less polar is the bond, but this is not the case with the answer given.
I was getting a), but the answer is d).


texts: How do you find the average rate and instantaneous rate given a kinetics plot?

texts: What is average rate? What is instantaneous rate? How do you find these? My teacher described finding the tangent to a graph. I am not sure what is meant by this.


texts: How to efficiently weight DCC (N,N'-Dicyclohexylcarbodiimide)?

texts: I have to run a reaction using N,N'-Dicyclohexylcarbodiimide and at room temperature, it is solid, but it's very hard to weigh. I know its melting point is around 40 degrees. Is it better to melt it and measure it as a liquid or is it no worth the struggle? I just don't want to have it in my hands anymore after reading it is very toxic in contact with skin and I feel like I had a few grams in contact with my hands everytime I try to break the chunks and weight it. Any tips on dealing with this reagent?


texts: Is anyone aware of a open source atomic spectra database? In particular I am looking for high resolution Na atomic emission which can be downloaded in csv or Excel. I am aware of NIST but I could not find a atomic spectrum. Secondly do they allow re-use of their figures? Thanks.


texts:
I've recently purchased a Damascus knife and am patiently awaiting it's arrival in the mail. I have been researching the potential care and maintenance habits for this craftsman blade, hoping to keep it in pristine condition.

I'm wondering what measure(s) could be taken to prevent a Damascus knife from rusting. I will be crafting the handle from my own scales and pins upon receiving the item, so any manipulation done to the steel can be preformed upon the blade in its entirety. The alloys used are a mix of 1095 and 15n20 steels respectively.

One of the potential means that I've entertained the thought of is bluing, AKA a black oxide finish. Bluing is a method commonly used on gun metal in which various gun parts are submerged in caustic hot salt baths for a period of time in-order to attain the coat. This isn't the only method to obtain the oxide layer, it's but one of many. Some sources have stated that bluing provides rust resistance while others are skeptical since most oxide layers as a result of the process are merely 2.5 micrometres (0.0001 inches) in thickness.

The method I'm most interested in potentially trying is cold bluing. Cold bluing can be achieved either by coating the high-carbon steel in mustard, painting it in a commercially sold "perma-blue formula", or submerging it in an acidic at-home substance such as vinegar or lemon juice (boiling vinegar to enhance the effect).

Here is my question Ultimately TL:DR Can a true rust resistant layer be obtained via cold-bluing methods on high-carbon Damascus steel (1095 & 15n20)? Will the acidic substance such as vinegar or "perma-blue formula" simply eat through the steel with time (while I'm letting the bluing process take place before I've neutralized the blade with something such as baking soda), or will it develop a thicker layer of patina oxide layer? Some sources say the bluing layer is rust, therefore rust can't develop on top of rust. Others say bluing is purely cosmetic and can not prevent rust.


texts: Why is the ortho isomer a major product in the nitration of toluene?

texts: Usually when an ortho-para directing substituent is present on the benzene ring for an electrophilic aromatic substitution reaction, the para product is the major product (exceptions can be there when hydrogen bonding or ortho effect of COOH group makes the ortho product a major one.) But I don't understand why the ortho product in nitration of toluene is the major product (and the para product isn't). The ortho position is supposed to have more steric crowding, right?


texts: Stability of a carbanion that is attached to three phenyl groups

texts:
I had come across a question - which asked me to predict the stability of a carbanion attached to 3 phenyl rings, in opposed to one in which the same 3 phenyl rings that are attached to the carbanion are now attached to each other via sigma bonds at the ortho position.
While comparing the stability, I thought that both of them would be stabilised by the -R effect equally. Hence, I could not choose between either of them.
However, my book says the answer would be the later case without giving an explanation and I couldn't find one anywhere on the net as well.


texts: Why does HgCl2 react with HCO3^- but not with CO3^2-?

texts:
I have started learning Qualitative Salt analysis recently. When I was reading about tests to distinguish $\ce{CO3^2-}$ and $\ce{HCO3-}$, I came across a line in a book which states

  $\ce{HgCl2}$ forms a reddish-brown precipitate of $\ce{3HgO.HgCO3}$ with $\ce{HCO3-}$ but no reaction is reported in case of $\ce{CO3^2-}$.

I am not able to understand why there will be no reaction of $\ce{HgCl2}$ with $\ce{CO3^2-}$.

It would be better if I can get a sound logic for this so that I can remember it better.


texts:
When choosing a cup of tea, I can choose a big cup or a small cup. I'm wondering if I get more caffeine with the bigger cup or the same amount of caffeine. (in moles)

My question is: For a given teabag and dunking duration - will I get more caffeine in a bigger cup or the same amount?

Assumptions

Teabag is placed in cup first - and hot water poured directly onto the bag
Same amount of stirring across both cups (assume three spoon swirls)
The main varying parameter is the volume of solvent changing

Question behind the question - trying to express it another way

Is there a kind of 'fixed rate of dissolution' that limits the amount of caffeine that comes out over a period of time - ie for two cups where one is 250ml and one is 300ml - and each have a tea dissolving time of 30s - wouldn't they have the same number of moles of caffeine at the end because of an upper bound on the rate of caffeine dissolving?


texts: Physical gelation result in a single massive polymer chain?

texts:
Physically crosslinking PVA polymers using the freeze-thaw method (Peppas 1975) results in regions of interconnected PVA polymers through crystalline regions formed when frozen and which persist after thawing. These physical crosslinks are sufficient to produce a homogenous hydrogel of predictable bulk characteristics. The formation of Jello gelatin uses a similar phenomenon.

My question is:
Are these crystalline regions only available to form at the free ends of the polymer chains, or can these lamellae form along any portion of the polymer chain?

If crystallization were only able to occur at free ends of the chain, this would result in a massively long polymer chain (assuming tip to tail occurred for many polymer chains in the solution) and as such the bulk polymer might be defined as a tangled network.


texts: Draw a structure for each of the following isomers of unsaturated amine 1

texts:
My ochem professor has several practice exams as resources but does not include answers,  I believe I understand the concepts but once I apply them I'm not sure whether I'm right or clueless. Can anyone check my work and if I'm wrong tell me why ?

  The format of his exams does not seem to be anywhere else online but if it is can someone provide a link. I really want to understand how to deal with these more complex structures rather than look at Fischer projections and simple problems again


texts:
Why does the rotational constant B decrease and transition spacings decrease as the mass of a particle increase?

I understand from a purely equation perspective that since

$$B = \frac{h} {8\pi ^2 cI}$$

that as $I$ increases the denominator increases and so $B$ decreases. But what is the physical reasoning behind this? Why or in what way is the rotational constant dependent on mass?


texts: What type of stereoisomers do these two complex compounds represent?


texts:
From time to time, I come by to see what people do with my mhchem package. Here, I came across a notation that I did not know yet: $\ce{K2O-nSiO2-xH2O}$ and $\ce{K2O - 3.2SiO2 - 2.7H2O}$

What is this? Is this really a bond? Is this a short form for writing $\ce{K2O-Si_nO_{2n}-H_{2x}O_x}$ and $\ce{K2O - Si_{3.2}O_{6.4} - H_{5.4}O_{2.7}}$? Is this an established notation that mhchem should support? (It doesn't yet with the numbers.) Do you have authoritative References?


texts: What is the difference between non-adiabatic coupling and diabatic coupling?

texts:
The diabatic couplings are the off-diagonal terms of wave functions written in a diabatic basis. There is a need to use the diabatic basis when there is a breakdown of the Born-Oppenheimer approximation. Then a transformation is done from the adiabatic to diabatic basis. But what does non-adiabatic coupling mean?

The reason I am asking is that most quantum chemistry softwares (I use Molpro) calculate the non-adiabatic coupling. Then some procedure has to be used to convert them to diabatic coupling. But what is the difference between the two and why do I need to use the diabatic coupling?


texts: How do non-polar substances dissolve in non-polar solvents?

texts: The case of polar solvents is clear to me - we get an attraction between opposite charges. However, how do non-polar substances dissolve in non-polar solvents? How could it be explained on a molecular level?


texts: How could I cause metal to rust rapidly?

texts:
I'm writing a novel set in the mid-nineteenth century. One of my characters needs to cause an iron padlock to rust rapidly, ideally within a matter of hours.

The lock doesn't need to rust away completely - the goal is just to make it noisey and annoying so that it can't be opened in silence.

Is this a realistic goal? If so, what methods could someone use to cause rapid rusting? Bonus points for suggesting period-appropriate materials.

Update: Based on the answer and comments below, it sounds a period appropriate approach would be to mix fine copper filings with saltwater and apply it to the lock.

I've read that bleach is an oxidizing agent which was available in the 19th century. Would adding bleach to this mixture increase the rate of rusting without creating an overly dangerous mixture?

Update: I conducted an experiment in my garage. Iodine worked pretty well.
Experiment Video

A few months later the iodine had eaten through the lid of the jar I tested it in:


texts: Why doesn't limestone thermally decompose instead of turning to marble?

texts: When limestone is buried and put under intense heat and pressure, why does it turn to marble instead of thermally decomposing into calcium oxide and carbon dioxide?


texts: Change in volume of two beakers on reaching equilibrium

texts:
Two beakers are placed side by side in a sealed container. The first beaker contains 100 ml of pure water. The other an equal volume of an aqueous solution of sugar. What should be the volume of the liquid in the two beakers when all physical change stop, that is when the equilibrium is reached?

I know that the vapour pressure of pure water is higher than the vapour pressure of the sugar solution. But is it anyway going to help me in solving this question.


texts:
Yesterday a Reddit user posted a page from Morrison's Organic Chemistry in which it is said that singlet methylene is less stable than triplet methylene. Another user asked basically the same I'm asking here, as he got no answer and probably won't get any.
I'm used to see radicals (and therefore diradicals) as extremely reactive and lone pairs as stable, when not reacting in some Lewis base fashion.
Also, Jahn-Teller effect explanations usually say that unpaired electrons configurations with each electron on a degenerate orbital are less stable than the paired configuration with some deformed structure, and therefore the structure deforms to "de-degenerate" the orbitals and achieve a lower energy configuration, hence the effect.
What we see here is exactly the opposite, isn't it?
What is it then that makes the triplet state more stable?
Wikipedia confirms the observation and adds a value to the energy difference: 38 kJ.
Wikipedia also says it is normal for carbenes to be more stable in the triplet state.


texts: When the vapor pressure exerted by the gas equals that exerted by the liquid, do their densities equal?


texts: Comparing relative negative inductive effect of substituents (dialkyl amine, amine, alkoxide, fluoride)

texts:
Which of the following is correct with respect to the negative inductive effect of the substituents?
  1. $\ce{-NR2 < -OR < -F}$
  2. $\ce{-NH2 < -OR < -F}$
  3. $\ce{-NR2 > -OR > -F}$
  4. $\ce{-NH2 > -OR > -F}$

Since it would be directly proportional to electronegativity, $\ce{-F}$ will be highest. That cancels out (3) and (4).

Now, to me both (1) and (2) seem correct. But the official answer (since this is from an entrance exam) is (2).

Are both (1) and (2) correct? Or is there something wrong with (1)?


texts: Is this a correct way to write a chain reaction?

texts:
I don't know much about chain reactions and how I understand them, they are just a series of chemical reactions where the products of the preceding reaction act as the reactants for the succeeding reactions.
Now, let's assume that $\ce{A}$ and $\ce{B}$ are two compounds that chemically react under certain conditions to give $\ce{X}$ and $\ce{Y}$. This chemical reaction can be written as:
$$\ce{A + B -> X + Y}$$
Now, let's also assume that $\ce{X}$ and $\ce{Y}$ react under the very same conditions to give $\ce{M}$ and $\ce{N}$. This chemical reaction can be written as:
$$\ce{X + Y -> M + N}$$
Now, can the series of these reactions be written as follows :
$$\ce{A + B -> X + Y -> M + N}$$


texts: Formation of hydrogen bromide: Does the concept of "order" apply to this reaction?

texts:
Started reading Levine's Physical Chemistry [1] yesterday, and I hit upon (another) wall.

On page 517, Chapter 15, she includes a reaction resulting in the formation of $\ce{HBr}$ from $\ce{H2}$ and $\ce{Br2}$ (it's a homogeneous, gas-phase reaction) along with the corresponding rate equation:

$$\ce{H2 + Br2 -> 2HBr} \qquad r= \frac{k[\ce{H2}][\ce{Br2}]^{1/2}}{1 + j[\ce{HBr}]/[\ce{Br2}]},$$

where $k$ is the rate constant and $j$ is...um...just a(nother) constant O:)

Levine goes on to mention:

  [For this reaction] the concept of order does not apply.

Now I'm still new to the whole Chemical Kinetics thing... But what's this?!

How come the "concept of order does not apply" to this reaction? I've never come across this situation in any book so far. Well, the reaction seems trivial (though the rate equation says otherwise...); I fail to understand why an order can't be assigned to this (overall) reaction.

(Note: Until I know otherwise, I'm assuming "concept of order doesn't apply", is the same as saying "this reaction has no order". Do correct me if I'm wrong in doing so...I tend to miss out on subtleties...)

Even having an order of zero still counts as having an "order". But what could Levine possibly be talking about when she says that the idea of an "order" doesn't apply to this reaction? What are the (physical) implications of a reaction lacking an "order"?

My questions, explicitly put:

Why can't an order be assigned to the above-mentioned reaction? Or can it?
What are the physical implications of a reaction having "no order" (as compared to reactions with an order)?

References

Levine, I. N. Physical chemistry, 6th ed.; McGraw-Hill: Boston, 2009. ISBN 978-0-07-253862-5.


texts: Is there a thermodynamic explanation for how a substance behaves based on its pKa and the solution’s pH?

texts:
If the pH of the solution is lower than the pKa of the compound, then the compound will be protonated, because pH is a measure of the concentration of protons, and low pH means a high proton concentration, so the compound is “driven” to act as a base and take up protons because there’s so much of them in the solution.
By the same logic, if pH is higher than pKa then the concentration of protons in solution is not very high, so the compound is “driven” to act as an acid and donate protons to the solution.
What is the “driving” force (I know it’s not technically a force) that causes this behaviour? Is there a thermodynamic reason involving changes in enthalpy and entropy and an increase in stability (decreasing Gibbs free energy) in the system?
My own thought is that perhaps this spontaneous exchange of protons between the compound and solution based on pKa and pH values takes the system closer to an equilibrium... but I don’t know where to go from there.


texts: Is it not safe for health to finish a bottle of wine during a week

texts:
People said that wine is good for health. So I take a cup (less than 100 mL) of wine every evening. (Yes, wine is cheap where I live.) So to finish a bottle of wine (750 mL), it takes me a week.
(Of course I put it in the refrigerator.) I have to say that it doesn't taste good after 3 days (but still OK).

But I don't know if it is not safe to do so. Maybe the wine begins to produce something not good for health after a few days when it is opened. So, my question is: what chemical species are formed after opening a wine bottle, making it go bad? Are they only bad for the taste, or also bad unhealthy?


texts: what is the acceptable percentage for food grade ethanol?Is 95% ethanol plus 5% water consider as food grade ethanol?


texts: Using real wave functions for chemical bond explanation

texts:
My question related with another one here.

For explanation valence bond direction chemists are used real wave functions, for example $p_x, p_y, p_z, \ldots$. But this functions do not describe the preffred direction of angular momentum, they are not the eigenfunctions of $\hat L_z$.
The functions, that are describe the states with some preffered directions are not real, they are complex. For hydrogen, for example, they looks like:

If some other atom nearby first one, then there is some prefered direction, and good funtcions for this situation should be not real ones, but complex ones. Then why chemists used real functions for bond explanation?


texts: How closely do GCMS spectra typically agree to conclude a match?

texts:
I have two unknown peaks on my GC (both with the same MW or rather highest M/Z ratio peak = 98) and I am trying to confirm their identity.

Unknown-1

Unknown-2

Based on the expected chemistry I have identified two potential candidate molecules from a library of GCMS spectra (see images below; just click on the images please if you cannot read the smaller font numbers).

Compound-A

Compound-B

Is it safe to think these are matches or not really? The MS was run in EI+ mode.

Unknown-1 is Compund-B?
Unknown-2 is Compound-A?

Both likely? Neither likely? Any one likely?

Is having the same set of M/z fragments good enough (e.g. 98-83-55 similar between Unknown-1 & Compound-B) or ought the abundance ratios also match mostly?


texts: How to read the used volume from a burette?

texts: I conducted an acid-base titration with vinegar and sodium hydroxide today, where sodium hydroxide was used as the titrant (solution in the burette). I collected the data for the initial and final burette reading to work out the volume of sodium hydroxide used. Is the volume used just the final burette reading, as the measurements are counted backwards?


texts: Dieckmann condensation's final protonation step

texts:
This is the Wikipedia image for the reaction mechanism:

In the final protonation step, why does the enol tautomerize to the keto form?

In the enol form the carbon-carbon double bond is in resonance with the ester's carbonyl double bond. Also the enol's $\ce{-OH}$ group would form a H-bond.

Shouldn't the enol form be more stable/predominant?


texts: How to measure and transfer suspensions?

texts:
I need to measure and transfer 10 ml of a fairly dilute suspension at a time to another container.

But no matter how diligently I do it, sedimentation happens quickly after mixing and successive transfers have different strengths or concentrations of solute.

Is there a way to achieve this without increasing the viscosity of solvent?

Note: I have to start with a dilute suspension and then transfer measured quantities of it. I have no other option.


texts: Does broader peak mean stronger absorber in UV/VIS?

texts:
I want to ask a question about peaks in a UV/VIS spectrum.

My lecturer in our introductory course mentioned the following:

  Two molecules may have the same molar extinction coefficient, but if I have two molecules, A and B, and B has a peak that is broader than molecule A, it will be a stronger absorber.

He failed to qualify this further or provide any reasoning.

My thought was that if it is a broader peak, then molecule B will absorb a wider range of wavelengths in a UV/Vis spectrum, but I couldn't see what he meant by a "stronger" absorber.

Does he mean that molecule B absorbs more wavelengths, so it is "stronger" or is there another qualification for using the word "stronger" to describe B?


texts: Reduction of 1,4-benzoquinone in the synthesis of 1,5-diazocane

texts:
Synthesize 1,5-diazocane using only benzene as a source of
  carbon atoms, and ammonia as the only source of nitrogen atoms.

My attempt: Noticing that the target compound has split the benzene ring, I attempted to split the benzene ring as well. I thought of two options:

H2/Pt at high temperature and pressue
Creation of phenol and subsequent oxidation

As the first process would create cyclohexane and be difficult to manipulate, I went with the second option. To synthesize phenol from benzene, I used a nitration, followed by reduction to create aniline, then used nitrous acid to create the benzenediazonium salt, and decomposed the salt in the presence of  water to create phenol. After the oxidation of phenol I got 1,4-benzoquinone.

Now, realizing that I would need to create 1,3-propandial in order to use $\ce{NH3/NaBH3CN}$ to create 1,5-diazocane, I attempted to make 1,3-propandial from 1,4-benzoquinone. Ozonolysis of 1,4-benzoquinone produces 2-oxo,1,3-propandial, which has an extra carbonyl group. Because of the many carbonyl groups involved in this compound, I was thinking of removing the carbonyl groups directly from benzoquinone, and doing an ozonelysis from there. However, I was not sure if any standard carbonyl reactions, such as the Wolff-Krishner or the Clemmensen reaction could be applied to remove the carbonyls, seeing as they are heavily resonance stabilized.

Therefore, I was wondering if these reactions do proceed on benzoquinone, and if not, then what other plausible ways of synthesizing 1,5-diazocane exist?


texts: How to determine the iron content in spinach from a titration with permanganate solution?

texts:
I used titration to find the mass of iron in a $5~\mathrm{g}$ sample of spinach after leaving the spinach to soak in tap water for 5 different amount of times. I added $\ce{H2SO4}$ to the solution and then titrated it with $\ce{KMnO4}$. These are my results:

I found the following total reaction occurs:
$$\ce{5Fe^2+ + KMnO4 + 8H+ -> Mn^2+ + 4H2O + K+ + 5Fe^3+ }$$

I am now trying to do my calculations to find my answer.
I first found the amount of substance of $\ce{KMnO4}$ needed to neutralize my solution and then what I think is the initial amount of iron ($\ce{Fe^2+}$). I am stuck as I am not sure how to continue to find the actual mass of iron on the right sight of the equation, do I use stoichiometry? Is finding the $\ce{KMnO4}$ value even necessary?


texts: In this question there is no inversion in A to B, but there is one in C to D. I feel like this must be due to the lone pairs on the $\ce{S}$ (in A) being able to open the ring, whereas this isn't possible in C to D so this can only occur via an $\mathrm{S_N2}$ reaction, but I just can't seem to make the mechanisms work for either.


texts:
Question 13 from the ACS chemistry olympiad exam:

  The phase transition from gas to solid is called
  \begin{align}
&\text{(A) condensation.} & \text{(B) evaporation.} \\
&\text{(C) polymerization.} & \text{(D) sublimation.}
\end{align}

I am pretty sure the answer is deposition, which is not listed, but yet the answer is (A) condensation [scroll to the end of the question paper to see the answer key].

Did the chemistry olympiad make a mistake, or is there something obvious that I am missing?


texts: What are the properties of COₓ where x ≥ 3?

texts:
$\ce{CO_x}$ are part of the oxocarbon molecule class. Commonly known are $\ce{CO}$ and $\ce{CO2}.$ However, there are molecules in which $x$ is equal to or larger than $3.$ Those molecules are barely known, other than the fact that they're unstable.

$\ce{CO3}$ decomposes slowly enough that it may come into contact with other molecules (including biomolecules), but nothing is known of its possible oxidizing potential.

$\ce{CO4},$ $\ce{CO5}$ and $\ce{CO6}$ are very unstable, and could possibly be strong oxidants (though it may never be known since they're too unstable).

Other than that, any information?


texts:
All my texts make it a point that in a differential rate law, the sum of the exponents on the reactant concentrations add up to the overall reaction order. However, I have yet to see any use in this. So you have two reactants, each undergoing a first-order reaction, and the overall reaction is second-order. So what? We analyze reactions for being first-order, second-order, and zero-order (at my level anyway), but that hasn't to do with the overall reaction order—just the reaction order pertaining to each individual reactant.

So my question is simple: what is the point of the overall reaction order? Why is it important?


texts: What could possibly cause a "melting" reaction between vinyl and plastic?

texts:
This question was posted in Electronics. Something is really odd about it! What could possibly be causing this "melting" reaction between a common flexible covering (vinyl, apparently) on test lead clips and the plastic there?

  a couple of breadboards had been lying in a box with a rubbered alligator wire sandwiched between. They've been there for maybe a month untouched. No other chemical or electricity has been present and only ambient heat (hot summer but 30°C tops here in Sweden). I'm pretty shocked that the plastic of these two different styles of breadboards both got so messed up simply by touching this rubber:

This is a very common alligator clip and very common electronics breadboard, often used together. I'm wondering whether the asker is telling us everything.


texts: What is the product of the following series of reactions?

texts:
.

The answer given to this question is .

This is how I attempted solving the problem.

Considering that my answer and the author's answer is differing only by a methyl group, is this a publishing error or am I wrong somewhere?

Himanshu pandey, Advanced Problems in Organic Chemistry, 9th edition page 219 question number 4


texts: How to run crystal simulation on GAMESS?

texts:
I know GAMESS is not best suited for crystal simulation but I am not ready to start learning another package as VASP. As I heard GAMESS is able to do some calculations in a "terminated" crystal (I mean using an ion in the periphery instead of repeating it multiple times).  Mostly I need to calculate HOMO-LUMO gap / hessian matrix and transitional state of a surface reaction .

I looked in the web but couldn't find a good worked example of using GAMESS for crystals.  Is there anywhere I can find such an example ?


texts: Meta-directing nature of anilinium cations

texts:
The comments on this answer seem to detail a trend in which $\ce{NR3+, NHR2+, NH2R+}$ all show meta-directing nature towards electrophilic substitution, with the slightly stronger para-direction of $\ce{NH3+}$ being the odd one out, as cited from March's Advanced Organic Chemistry.
The 2020 edition has this to say, on pages 617 and 618 under "Aromatic Substitution, Electrophilic" (emphasis mine);

Groups that lack an unshared pair on the atom connected to the ring are electron
-withdrawing with a (+) charge or (δ+) dipole. In this category are, in approximate order of decreasing deactivating ability, $\ce{NR3+}$, .... and $\ce{NH3+}$. Also in this category are all other groups with a positive charge on the atom directly connected to the ring... and many groups with positive charges on atoms farther away, since these are often still powerful −I groups. The field-effect explanation predicts that these should
all be meta directing and deactivating, and (except for $\ce{NH3}$
+) this is the case. The $\ce{NH3+}$ group is an anomaly, since this group directs para about as much as or a little more than it directs meta, often because the ammonium ion is in equilibrium with the amine. The $\ce{NH2Me+, NHMe2
+}$, and $\ce{NMe3+}$ groups all give more meta than para substitution, with the percentage of para product decreasing with the increasing number of methyl groups.

@ron's explanation coupled with the equilibrium argument makes a pretty good reason for why aniline behaves this way.
But why do the other groups meta-direct? The field effect mentioned above seems to refer to inductive effects, which should make them para-directing.


texts: What is actually the difference between valence bond theory and molecular orbital theory?

texts:
Recently I have read about both of the concepts in my book (Physical Chemistry by Atkins, Paula). It was literally a reading; though I could understand the language and superposition of orbitals, inversion symmetry, and so on, I never could really comprehend how these two theories differ (or agree) with each other. I have googled it but couldn't gain a lucid explanation between the differences in their approaches. So, now my question is:

How do these two theories differ from each other? What are the differences between their approaches?

Also, in VB theory, resonance plays a pivoting role; why isn't such concept needed in MO theory? Why it is told that "MO theory provides a global, delocalized perspective on chemical bonding"? This portion of the question was split to a separate question: Why is the resonance concept not required in molecular orbital theory?

Edit: After viewing some of the answers, I think IMHO, I had to clear what I was really asking. By saying "difference between MOT & VBT", I am not intending to mean that just write the different predictions the two theories can separately succeed in making. What I really mean is the difference between their approaches & their way of explanation. Of course, the case is not like "Hey, look, one theory is outdated; just follow the other one..."; they are both important and hence do want to know the difference between their pathways of analyzing the cases.


texts: Where does Free Energy go in a Redox Reaction?

texts:
This doubt came to my mind while answering the following question:

  Why does a voltaic cell not operate unless the two separate compartments are connected by an external circuit?

The answer seems to be that only on connecting the two halves of a Redox reaction via an external circuit, does one allow the electrons to be transferred from one species to another. And while the electrons move towards their goal (to a higher potential), they do work in the way (light a bulb or a motor or something).

Another way to view this process is that the free energy of the Redox reaction is used to do useful electrical work.

But then my brain started to wonder and there came up a question - what happens to all this energy when none of it is actually used to do electrical work, i.e, when the Redox reaction is let to occur spontaneously, where does all the free energy go? Does it get converted to heat, thus warming the solution? Or does it simply stay stored in the solution in some form?


texts: Which of the following show hyperconjugation

texts: None of the given compounds have any alpha hydrogen to show hyperconjugation, but the given answer is c.


texts: Correct equation for Ionic Conductivity (λ) in Solutions?

texts:
We haven't started on Electrochemistry at school yet, but I did manage to find some time to read up on the topic. One thing I've noticed from when I started, is that different books and sites use different terms for the same symbols (For example: One book says Molar conductivity is represented by $\Lambda$, but another says it's Molar Conductance, and another book makes use of both Molar Conductance and Molar Conductivity, albeit inconsistently).
Now, my school textbook, as well as another book, Physical Chemistry by Wallwork and Grant employ the following equation for ionic conductivity:
$$\lambda=F\mu$$
Where $F$ is the Faraday constant and $\mu$ is the ionic mobility of the ion under consideration.
But I saw another equation on Wikipedia

$$\lambda=zF\mu$$
Where $z$ is the ionic charge of the ion being considered.

So my question is, which of these equations are right?


texts: How do I calculate the standard enthalpy of formation for liquid ethanethiol? Do I use Hess's law?

texts:
Calculate a value for the standard enthalpy of formation for liquid ethanethiol, $\ce{C2H5SH}$. Use the equation given below and enthalpy of combustion data from the following table.

Just assume values and comment the methods to solve the problem, I'll try solving it.

Edit: I'm not sure whether you're supposed to use

$$\Delta H^\circ = \sum{\Delta H_f(\text{product})} - \sum{\Delta H_f(\text{reactant})}$$

because the given is enthalpy of combustion data, not heat of formation. I'm not quite sure what an enthalpy of combustion is.


texts: What is the green solution that gives yellow precipitate when reacted with lead (II) nitrate and that gives a green precipate when reacted with aqueous sodium hydroxide ? I'm confused with this question.


texts: Confusion in finding electrophilic centre

texts:
In the compound CH3-CH2-CN the electrophilic centre according to my NCERT TEXTBOOK(class 11) is the carbon of cyanide but I think it should be the the carbon adjacent to cyanide since, during bond cleavage between cyaninde and ethyl the electron pair will be taken up by the carbon of cyanide so in this way it is a neucleophilic centre . Hence I think that the carbon of ethyl should be electrophilic centre. Am I right or iam missing something or my textbook is wrong?
Any help is greatly appreciated.


texts: When volume decreases and the product has less moles than reactants, why is there no increase in the reaction quotient?

texts:
Assume a reaction:

$$\ce{CO + Cl2 <=> COCl2}$$

My textbook says that a decrease in volume will result in the reaction quotient being less than the equilibrium constant. Why is that?

With a decrease in the volume, a forward reaction proceeds. Thus, more product and less reactant means there should be a higher reaction quotient.


texts: Why do bubbles form and stay when I shake a bottle of tea?

texts: I have some bottled tea and I noticed that shaking it creates some foamy bubbles that stay for quite a while (at least half an hour if not more). I originally thought it has something to do with my saliva, but then I realized that a brand new bottle of tea also does the same thing. The listed ingredients are water, oolong tea and vitamin C. What could be the reason?


texts: Effect of impurities on Enthalpy of vapourization

texts:
How does the Enthalpy of vapourization change when impurities are added? I know that the boiling point of a substance increases on addition of impurities, but how does the Enthalpy of vapourization change? Is less heat needed to convert the liquid from a solution to a gas?

Related: This question deals with a similar problem, but for Enthalpy of fusion instead of Enthalpy of vapourization.


texts: Should you work in metres-cubed or litres in chemistry?

texts:
Generally, is it better to work in metres-cubed or litres in chemistry?

My undergraduate degree was in civil engineering and we always worked in $\mathrm{m^3}$.

However, I notice the gas constant $R$ is used in a few different forms:

$$R=0.0821\mathrm{\frac{L\cdot atm}{mol\cdot K}}$$
$$R=8.3145\mathrm{\frac{J}{mol\cdot K}}$$
$$R=8.2057\mathrm{\frac{m^3\cdot atm}{mol\cdot K}}$$

among others.

I guess it depends on the application but is it generally easier to work in litres or metres-cubed?


texts: Electrolysis of aluminum in a solution of magnesium sulfate

texts: So I recently started looking into electrolysis to produce chemicals and I have only produced a few chemicals from it like copper hydroxide and copper sulfate. However I can’t seem to figure out what this wight precipitate that is produced in a electrolysis between  a aluminum cathode and a aluminum anode in a solution of magnesium sulfate.I am relatively new at chemistry and I am only in high school so I can’t figure out this precipitate. I would also like to know if there is a new dissolved salt being formed. Thanks in advance all ideas are much appreciated.


texts: How Does Benzyl Alcohol Produce a Peak at m/z = 79?

texts:
I have understood the mechanism for converting ion 1 (benzyl alcohol) to ion 2 (m/z = 107) but not the mechanism for the conversion of ion 2 to ion 3 (m/z = 79).
Please elaborate the mechanism for the conversion of ion 2 -> ion 3.


texts: Avogadro Conformer Properties with Linux Version

texts:
My Windows version of Avogadro has the following menu point:

View > Properties > Conformer Properties

My vanilla Avogadro version under Ubuntu does not even have the menu. What do I need to do, to either activate the menu or to get to this option under Linux?


texts: Determining the number of triphenylphosphine ligands in nickel(II) complex

texts:
A complex is synthesised by combining hydrated solutions of $\ce{NiCl2}$ $(\pu{0.6 g})$ with $\pu{1.35 g}$ triphenylphosphine $(\ce{PPh3}).$ After cooling the product precipitates as a solid with formula $\ce{NiCl2(PPh3)_x}.$ Determine $x.$

I first found the molar ratios
$$n(\ce{NiCl2}) = \frac{\pu{0.6 g}}{\pu{129.59 g mol^-1}} \approx \pu{4.6 mmol}\tag{1}$$
$$n(\ce{PPh3}) = \frac{\pu{1.35 g}}{\pu{262.29 g mol^-1}} \approx \pu{5.1 mmol}\tag{2}$$
The smallest ratio these go into gives $x \approx 1,$ but I don’t think this is right.


texts: Is there a general method for working out electron configurations?

texts: For up to period 3, elements' electron configurations are relatively easy to work out until the transition metals begin. Then some elements may have $\ce{4s}$ orbitals which are preferred by electrons over $\ce{3d}$ orbitals. These small rules don't make sense all the time and only cover some elements. Is their any master method for working out the electron configurations of any given element?


texts: Is there a metal for which its gas is necessarily a plasma?

texts:
Related to this question:
Gaseous metals?

The top answer clarifies that even with metals, the gaseous state is distinct from a plasma.

However, my question is, is this actually true in all cases?
Or is there an element and a pressure for which heating it to a gas will necessarily also be hot enough for it to immediately become a plasma?
Or is there a situation in which heating can bring about the transition from solid or liquid straight to plasma while skipping gas?


texts: What is the white powder that I have extracted from cinnamon?

texts:
In Advanced higher chemistry, I am extracting cinnamaldehyde using this procedure- https://www.flinnsci.ca/api/library/Download/ba6ab218508047ea843bb0d9e580be16
. After evaporating the hexane, instead of the cinnamaldehyde (a liquid), a solid white power is formed. We have no clue what it is and think it may be either something that is naturally extracted from the cinnamon bark or something that was added during 'production' (got it from Tesco's).


texts:
Is it an ion or a neutral atom that is created through beta decay?

For example: $_6^{14}\mathrm C \to ~ _7^{14}\mathrm N + \mathrm e^- + \mathrm{v{_e}}^{-}$

Isn't $_7^{14}N$ an ion since neutron gives us only a proton and an electron, not a proton and 2 electrons? If so, why isn't it stated in the example above (it's from Wikipedia)?


texts: Using a significantly large metallic sphere, could we draw out the electrons from the negative terminal of a battery?

texts:
I've pored over many articles on electrochemical cells, and I understand that on the oxidation side of a zinc-copper Daniell cell, the anode is highly negatively charged because zinc participates in oxidation and loses electrons as the ions go into the zinc sulfate.

So since the anode is rich in free electrons, is it possible to take an electrically neutral, large conductor (a metallic sphere for example), touch it to the negative terminal of the battery so that the free electrons will distribute themselves over its surface, discharge the sphere, and repeat this until the negative terminal is neutralized?