texts: Usage of ammonia as odorant in fuel gases

texts:
Usually, thiols such as ethanethiol are added to fuel gases to warn the user of a leak. Why is a few percent of ammonia not used instead?

Ammonia is flammable so it will burn to nitrogen and water in the flame.
Ammonia has a strong smell, and causes a stimulation effect which may wake sleeping people in the event of a gas leak.
Ammonia produces no sulfur oxides when it burns (although the usual amount produced with ethanethiol is insignificant).


texts: Do atoms in a molecule actually keep rotating freely in case they have sigma bond?

texts: While reading about cis-trans isomers I found the concept of free rotation of atoms.it says 2 atoms connected by sigma bond do not have trans sis isomer because of free rotation.while in case of pi bond free rotation is not possible. My question is : do we mean actual rotation of atoms in molecule when we say free rotation? Does the rotation happen spontaneously? What things are responsible for the rotation? Or is it just a concept to understand the concept of cis-trans isomers?


texts:
The $K_\mathrm w$ is a function of temperature. It is $10^{-14}$ at $25\ \mathrm{^\circ C}$. When the temperature is $50\ \mathrm{^\circ C}$, the $K_\mathrm w$ can be calculated to be somewhere around $10^{-12}$ using Vant Hoff's equation, but this is so weird.

MY ATTEMPT

If we will solve for $K_\mathrm w=10^{-12}$, we get $\rm pH=6$. Will the water become acidic due to increase in temperature?


texts: Calculating equilibrium constants: adding two or more equations

texts:
If two or more reactions are added to give another, the equilibrium constant for the reaction is the product of the equilibrium constants of the equations added.

How is this true? What is the reason?


texts: What is the function of nitrobenzene as a solvent in Friedel Crafts alkylation reaction?

texts:
I would like to know what is the function of nitrobenzene as a solvent in Friedel Crafts alkylation reaction.

Answer to this question suggests that Friedel Crafts reaction is not possible with nitrobenzene and I understand that it's because of the big loss of electron density of the benzene ring due to the highly deactivating nature of $\ce{-NO2}$


texts: How do I compute the mean dissociation time from the dissociation constant, assuming instantaneous binding reaction rate?

texts:
There is a solution with two chemical species, A and B. Given the equilibrium dissociation constant
$
K_D=\frac{[A][B]}{[AB]}
$
how do I relate the mean dissociation time $t_{off}$ to $K_D$, and initial reagent concentrations, assuming that the reaction time it takes for A and B to bind is much lower than the diffusion time from one to the other?
I know that $k_D = t_{off}/t_{on}$, so here I'm looking for $t_{on}$ in the approximation of instantaneous binding reaction time, which I assume should be the time required for a particle of a species to diffuse through the solution from a particle of the other species to the next. How do I do that to solve the question in the previous paragraph?
EDIT: changed notation to fix  typo and to incorporate Poutnik's feedback.


texts: Substances with high physical expansive property/expansion after reaction

texts:
I want to know if there is a substance/mixture of substances that expands more on some chemical or physical change, than what I've already seen.
Elephant toothpaste is a good example, a small amount of two substances expands into something with much more volume.
The list I have created so far is:

Diaper jelly
Orbeez
Elephant toothpaste
Water $\ce{->}$ Ice

A list of multiple substances with most expansive chemical or physical property will be appreciated.
The reason for my question: trying to develop a realistic 'smoke bomb' or some sort for a project photography. Best result would be lets say from small pellet, to huge smoke cloud.


texts: Isomerization reaction involving carboxylic acid derivatives

texts:
I have tried searching for what type of organic reaction this is in my textbooks and ended up with nothing. Thus, I could not fully understand and refer to the mechanisms that the solution has explained.
So, please tell me the types of organic reactions (i.e. name the reactions involved for me) that are involved in this question. If possible you can describe how the mechanism of this reaction. Thank You!


texts:
Oxford dictionary online gives etymology of alanine as:

  Coined in German as Alanin, from aldehyde + -an (for ease of pronunciation) + -ine.

But I see no resemblance to the aldehyde structure in alanine. Is this etymology incorrect, or am I mistaken about the resemblance?


texts: Comparison of boiling points of para-derivatives of phenol

texts:
The boiling points of four para-derivatives of phenol are:

How can we compare the boiling points of p-nitrophenol and p-aminophenol?
Apart from the hydroxyl group, p-nitrophenol has two oxygen atoms to form inter-molecular H-bonding. Whereas, p-aminophenol has a nitrogen atom and two hydrogen atoms to form inter-molecular H-bonding. Also, the molecular mass of p-nitrophenol is more than that of p-aminophenol.


texts: How can you extract palladium from palladium chloride

texts:
Hey guys I am working on a school project, focused on how precious metals can be recycled from industrial products. I am very much not an expert on the subject of chemistry. But I am just trying to get basic understanding on how to extract palladium from a catalyst like palladium chloride.
Thanks in advance,
Ilias


texts: What is the effect of conjugation of a carbonyl group in IR spectroscopy?

texts:
Doing an exchange term so I've missed some classes that the others have attended, and unfortunately we're getting contradictionary explanations, so I thought I'd try and ask you.

Would be extremely thankful if someone could explain the effect of conjugation of a carbonyl group on the resonance frequency in IR spectroscopy.

Our 'assignment' is basically to figure out if it's supposed to be lower or higher than an unconjugated carbonyl.

Thanks in advance!


texts: What is the difference between quantities reported as optical rotation and circular birefringence?

texts:
Optical activity gets complicated quickly and the following question is intended to avoid threshold confusion. The linked lecture note* seems very accessible to me and Table 10.6 in particular is quite clear. On page 2 the author writes, "Optical rotation results from circular birefringence..." and then relates that idea to circular dichroism.

  My question is: How does the angle we measure in a student polarimeter as optical rotation relate to the angle reported as circular birefringence? Do they merely differ by a constant or is there more to it than that?

What I think I get is that circular birefringence measures the ellipticity of light, which involves a difference in the transmission of L and R circularly polarized components of an initially plane-polarized beam. Optical rotation simply measures the change in plane of polarization of light that has passed through a sample. My guess is that the two are different, otherwise one could just translate to degrees of rotation...? But if they are both measures of optical activity it would be also be surprising if they are related in some non-linear way.

*The note is from a lecture at Washington Univ. at St. Louis and I will try to get a better cite.


texts: Evaluating (∂U/∂T)P - (∂U/∂T)V for an ideal and van der Waals gas

texts:
What is the value of $$\left(\frac{\partial U}{\partial T}\right)_{\!P} - \left(\frac{\partial U}{\partial T}\right)_{\!V}$$ for an ideal gas and for a van der Waals gas?

($U$ refers to the molar internal energy.)


texts: Do some electrons transfer if I connect with a conductor 2 solid pieces of 2 different elements with different electronegativity?

texts:
Making some researches to answer my last post, I found this article.
It explains that when a piece of zinc and a piece of copper are connected with a conductor, since copper is more elctronegative than zinc, electrons start to flow form zinc to copper till too many electrons has reached the piece of copper and they start to  repel the others.
Is this explanation accurate?
Can you generalize this observation for other elements connected through a conductor?
Does it work for solid and liquids?
**EDIT:
I'm not stating that there will be an electricity flow, I'm asking if there is an amount of electrons that will converge from the zinc to the copper. Even if it happens for a millisecond.


texts: Represent bonds spanning a unit cell boundary plane

texts:
Is there a chemical input format that is-

Supported by Open Babel (and hence supports visualization in avogadro??)
Can represent a bond connecting an atom to its partner in a neighbouring unit cell, for crystals/systems with periodic boundary conditions

Follow up (added later):
I could not understand how cif does it, or cml. But it would be nice if I could get rid of the symmetry folds in the markup given below.
Here is the cif file. The cml output using babel is --
<?xml version="1.0"?>
<molecule id="Calcium titanate" xmlns="http://www.xml-cml.org/schema">
 <crystal>
  <scalar title="a" units="units:angstrom">5.380000</scalar>
  <scalar title="b" units="units:angstrom">5.440000</scalar>
  <scalar title="c" units="units:angstrom">7.639000</scalar>
  <scalar title="alpha" units="units:degree">90.000003</scalar>
  <scalar title="beta" units="units:degree">90.000003</scalar>
  <scalar title="gamma" units="units:degree">90.000003</scalar>
  <symmetry spaceGroup="-P 2c 2ab">
   <transform3>1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1</transform3>
   <transform3>1 0 0 0.5 0 -1 0 0.5 0 0 -1 0 0 0 0 1</transform3>
   <transform3>-1 0 0 0 0 -1 0 0 0 0 1 0.5 0 0 0 1</transform3>
   <transform3>-1 0 0 0.5 0 1 0 0.5 0 0 -1 0.5 0 0 0 1</transform3>
   <transform3>-1 0 0 0 0 -1 0 0 0 0 -1 0 0 0 0 1</transform3>
   <transform3>-1 0 0 0.5 0 1 0 0.5 0 0 1 0 0 0 0 1</transform3>
   <transform3>1 0 0 0 0 1 0 0 0 0 -1 0.5 0 0 0 1</transform3>
   <transform3>1 0 0 0.5 0 -1 0 0.5 0 0 1 0.5 0 0 0 1</transform3>
  </symmetry>
 </crystal>
 <atomArray>
  <atom id="a1" elementType="Ti" formalCharge="4" xFract="0.000000" yFract="0.500000" zFract="0.000000"/>
  <atom id="a2" elementType="Ca" formalCharge="2" xFract="0.006480" yFract="0.035600" zFract="0.250000"/>
  <atom id="a3" elementType="O" formalCharge="-2" xFract="0.571100" yFract="-0.016100" zFract="0.250000"/>
  <atom id="a4" elementType="O" formalCharge="-2" xFract="0.289700" yFract="0.288800" zFract="0.037300"/>
 </atomArray>
 <bondArray>
  <bond atomRefs2="a1 a4" order="1"/>
  <bond atomRefs2="a4 a2" order="1"/>
 </bondArray>
</molecule>


texts: How do I make a 0.5 M citrate buffer at pH 4.5?

texts: I need to make a citrate-sodium citrate buffer at 0.5 M concentration and pH 4.5. I calculated the molarities of the citrate and disodium citrate based on the Henderson Hasselbalch equation, using a pₐ of 4.76 . To cross-check my calculations, I tried a couple of online calculators, but the results are way off from mine. I think the formulae should change based on where I use monosodium, disodium or trisodum citrate. What is the right way to go about making this calculation?


texts:
Consider a binary azeotropic solution of two volatile components $A, B$. I wanted to try and find out the required concentrations of $A, B$ in the solution in terms of their vapour pressures. I tried using Raoult's Law to do this, but the I got an unexpected answer:

Let the vapour pressure of $A, B$ at the current temperature be $P_A, P_B$, respectively. Let their concentrations be $\chi_A, \chi_B$ and their partial vapour pressures over the solution be $p_A, p_B$.

Then, by Raoult's Law,

$$p_A = P_A\chi_A$$

$$p_B = P_B\chi_B$$

By Dalton's Law of partial pressures, the mole fractions of $A, B$ in the vapor phase are given by $\frac{p_A}{p_A + p_B}$ and $\frac{p_B}{p_A + p_B}$ respectively. Since the solution is azeotropic, these two are equal to their mole fractions in solution.

That is:

$$\frac{P_A\chi_A}{P_A\chi_A + P_B\chi_B} = \chi_A \implies \frac{P_A}{P_B}(1-\chi_A) = \chi_B\tag1$$

Similarly,

$$\frac{P_B}{P_A}(1-\chi_B) = \chi_A \tag2$$

Substituting $(1)$ in $(2)$, yields

$$ \frac{P_B}{P_A}\left(1-\frac{P_A}{P_B}(1-\chi_A)\right) = \chi_A$$

$$ = \frac{P_B}{P_A}-1+\chi_A = \chi_A$$

$$\implies P_B = P_A$$

But there are numerous azeotropes where this condition is not satisfied. How come?


texts: Can carbanion rearrange to attain more stability?

texts:
We all know that carbocations rearrange to attain more stability, but I have never heard anything about carbanion rearrangements for attaining more stability.

Is it possible for a carbanion to rearrange? If not,why?


texts:
I understood the simplified reason for optical activity of a compound based on the difference in the angular velocities of counter-rotating circularly polarized light. The difference is due to the spatial arrangement of different groups with different electronic configurations. Even though it wasn't specified in my textbook, I guess the difference in the electronic configurations cause some electrical constraints to the oscillating electric field of the plane polarized light, thereby rotating the plane of polarization.

Do isotopic groups cause optical activity?

For example, is $\ce{CHDTF}$ optically active due to the presence of different isotopes of hydrogen?

I understood that $\ce{CHTDF}$ is chiral or it exists as a pair of enantiomers. But I don't know whether different isotopes of hydrogen account for any optical activity as I think optical activity is something to do with the electronic configurations rather than the atomic masses.


texts: Difference between black and brown eumelanin / red and pink pheomelanin

texts:
Wikipedia says the following:

  There are two types of eumelanin—brown eumelanin and black eumelanin—which chemically differ from each other in their pattern of polymeric bonds.

What are those differences in polymeric bonds and which bond produces what color? Are the bonding differences also the reason for the different colorations in pheomelanin?


texts: What does radiofrequency really do in NMR & MRI?

texts:
In NMR, the protons’ frequencies are affected by the magnet which makes them precess around its magnetic field so now all protons will have different frequencies according to their environment including shielding and de-shielding effects. As I read, the radio frequency pulses only change the resonance of protons and make their $\omega$ angle  change  ($180^\circ$) to be induced inside the coil and make signals that can be measured.

But if this true why do we have to use different gradient coils and phase encoding gradient coils in MRI, if the protons really have different frequencies?


texts: I would be very grateful if you help me to understand what is nanoporous structure. Does this term relate only to the nanoporous materials (as I understand, materials with regular porous structure) or to the such structures as nanotubes, fullerenes, layered silicates and so on? My doubt arises from the fact that the last do not seem for me to have regular structure.


texts: Can I claim that a hot dip Aluminum coating in steel provides cathodic protection to a substrate since Al can act as sacrificial anode?

texts: I have a school experiment wherein I will put aluminum coating to a steel substrate, wherein the Al will act as a corrosion protector for the steel. We know that aluminum is also classified as a sacrificial anode. Can the aluminum coating on the steel provides a cathodic protection?


texts: Random order of melting points of group 2 elements

texts:
Compare the melting points of $\ce{BeF2, MgF2, CaF2, SrF2, BaF2}$.

Actual order is  $\ce{ BeF2 > CaF2 > SrF2 > BaF2 > MgF2}$.

I have worked out the following things while comparing their melting points.

a) Melting points of ionic compound increases as the ionic interactions between cation and anion in the metal lattice increase. In this case, smaller cations will result in stronger interactions. That gives this order :  $\ce{ BeF2 > MgF2 > CaF2 > SrF2 > BaF2}$.

b) None of these compounds is a covalent solid. If it were, its melting point would have been higher.

c)The order of melting point also depends upon the crystal lattice structure.

(i) Be and Mg crystallise in hcp, Ca and Sr in fcc and Ba in bcc.

(ii) The cations will occupy the lattice points and since fluoride ions are smaller than cations, they will occupy the voids.

(iii) The more is the coordination number, the more will be repulsions between similar ions. In the lattice, when two cations are in contact, there will be repulsions. But, the repulsions will be less when the size of carion will be small since in that case, the electron cloud of one cation will experience nuclear attraction by the other cation.

(iv) Hcp and fcc have the same coordination number.

(v) Based on this logic, the order should be:
         $\ce{ SrF2 > CaF2 > MgF2 > BeF2 }$.

(vi) Although, the coordination number of Ba is very less, it size is
          very big. So, we cannot say with certainty if it would have the
          lowest melting point.

Now, I don't know how to reconcile these two points, the factors are totally opposing. Where to put Barium? This made me think that the order cannot be predicted with certainty just based upon theoretical analysis of their lattice structures.

It is important for me to know whether the points that I have mentioned correct or not. Are there more factors that could influence their melting points? And finally, if the order can be predicted with certainty purely on theoretical basis, how would that be done?


texts: Maximum possible hypochlorite concentration from electrolysis?

texts:
For reference, "electrochlorination" is just the electrolysis of a simple solution of water and table salt (NaCl) followed by reintroducing the chlorine gas produced.

But, the Wikipedia article on "electrochlorination" claims

  The product of this process, sodium hypochlorite, contains 0.7% to 1% chlorine. Anything below the concentration of 1% chlorine is considered a non-hazardous chemical although still a very effective disinfectant. In addition, the sodium hypochlorite produced is in the pH range of 6-7.5. This means that the chemical is relatively neutral in regards to acidity or baseness. Also, at that pH range, the sodium hypochlorite is extremely stable and the electrochlorination extremely effective.

Is the yield really that small? It seems like we should be able to get much more! The electrolysis of NaCl in water
$$\ce{2H+ (aq) + 2Cl- (aq) -> H2(g) + Cl2(g)}$$
upon recombining the chlorine gas
$$\ce{2OH- (aq) + Cl2(g) ->  OCl- (aq) + Cl- (aq) + H2O(\ell)}$$
should lead to a net increase in pH
$$\ce{Cl- (aq) + H2O(\ell) -> OCl- (aq) + H2(g)}$$
as$\ce{\; OCl- (aq)\;}$is the conjugate base of a weak acid.

Consequently, it seems the resulting solution should have a much greater percent active chlorine, due to the hypochlorous stabilization effect of higher pH -- which would only get even higher as the electrolysis (given sufficient external voltage) continues!


texts: Why are hydrogen bonds in an antiparallel beta sheet stronger than those in parallel beta sheets?

texts:
Beta sheets are illustrated as such in most diagrams, where:

In an antiparallel β-sheet, the polypeptide strands are arranged such that a $\ce{C=O}$ and an $\ce{NH}$ from adjacent strands face each other, and the $\ce{H}$ forms an H-bond with the $\ce{O}$, with $\ce{C=O**HN}$ all lying on the same plane.
In a parallel β-sheet, the strands are literally parallel, and so the H-bond formed has to form a sort of angle, where the $\ce{C=O}$ and $\ce{NH}$ no longer lie on the same plane (when viewed from the perspective of the diagram).

Most explanations explain the stronger bond strength by stating the obvious from the diagram: that the "hydrogen bonds are aligned directly opposite each other, making for stronger and more stable bonds." (taken from chem libretexts, https://chem.libretexts.org/Bookshelves/Biological_Chemistry/Supplemental_Modules_(Biological_Chemistry)/Proteins/Protein_Structure/Secondary_Structure%3A_-Pleated_Sheet)
This seems intuitive, but my issue arises when considering some orbital geometry: in a peptide bond, the $\ce{C}$, $\ce{N}$ and $\ce{O}$ have orbitals with ${sp^2}$ hybridization, meaning that bond pairs/lone pairs are organized in a trigonal planar orientation around each of those atoms. As a consequence of this, one can also observe that all the atoms illustrated in the diagram should lie on the same plane, making things rather easy to visualize.
However, if one considers that the 2 lone pairs and one bond pair in the $\ce{O}$ atoms are orientated in a trigonal planar fashion, then shouldn't the ideal, strongest, H-bond is orientated at an angle (specifically $\pu{{60}^\circ}$) relative to the $\ce{C=O}$ bond? Now, if I observe the diagram again, it seems this $\pu{{60}^\circ}$ H-bond angle is better fulfilled in the parallel strand than in the antiparallel one. So shouldn't the H-bond in the parallel strand, theoretically, be stronger?
A possible explanation would be that the bond length in parallel strands would be longer, thereby weakening it. But that's not how most textbooks explain it, so what am I missing out here?


texts:
The liquid crystal can be control using polarizes light. This means we can control the arrangement of the liquid crystal molecules, then when the light passes through it can be manipulated.
But why exactly is this possible? What is the relationship between liquid crystal material and light pass through it? How do they interact and affect each other?


texts: In an Electrotlytic cell using MgSO4 electrolyte, Cu(OH)2 and Mg(OH)2 are visible products, Where Does SO4 go?

texts:
I have an electrolytic cell with $\ce{MgSO4}$in an aqueous solution at full saturation, running at a potential of $3.6v$ with a copper anode because I need some $\ce{Cu(OH)2}$.
Production of $\ce{Cu(OH)2}$, $\ce{CuOH}$ and $\ce{Mg(OH)2}$ are all visible.
There's no gas production at the anode but I expect that the oxygen is remaining in solution due to $\ce{OH}$ production.
There's no sign of $\ce{SO2}$ or $\ce{SO3}$, so
what Happens to $\ce{SO4-}$?
EDIT
$\ce{SO4-}$ eventually rejoins $\ce{Mg}$ because the more reactive base will always oxidize a less reactive neutral or acidic salt, not to mention that $\ce{H2SO4}$ is a species that will form under these conditions as $\ce{Mg}$ and $\ce{Cu}$ both become insoluble (which should actually yield $\ce{H2SO5}$ because $$\ce{Cu + MgSO4 + H2O -> Cu(OH)2 + Mg(OH)2}$$ @cathode, $$\ce{H2O + SO4- -> H2SO5}$$ @anode, which doesn't hang around too long $$\ce{H2SO5 -> 2H2SO4 + O2(g)}$$ and the obvious reformation of $\ce{MgSO4}$ via $\ce{H2SO4}$ + $\ce{Mg(OH)2}$ and $\ce{CuSO4}$ + $\ce{Mg(OH)2}$ so I was eventually left with $\ce{Cu(OH)2}$ as the only insoluble product.
I have since been able to produce $\ce{Mg(OH)2}$, omitting $\ce{Cu}$ entirely of course, but coming up with a process wasn't easy with my 3 months of experience. I however have been able to completely separate $\ce{Mg+}$ from $\ce{SO4-}$, yielding $\ce{H2SO4}$and $\ce{Mg(OH)2}$using perlite.


texts: Why does this E2 reaction occur on the less substituted carbon?

texts: In compound C it eliminates the beta hydrogen attached to the less substituted carbon, rather than attacking the beta hydrogen attached to the tertiary carbon. Why is this the case?


texts:
The saturated vapor pressure is designated as the gas pressure in a closed container when the evaporation process has reached an equilibrium (when there are as many molecules returning to the liquid as there are escaping it). Doesn't that mean that vapor pressure is dependant on the volume? Why not?

And how exactly is vapor pressure connected to the boiling point? I know that a liquid boils when its vapor pressure becomes equal to the external pressure but why is that? Is it because the pressure in the bubbles, that are formed by heating the liquid, is the same vapor pressure?

Thanks in advance.


texts: What Are Examples of Reducing Sugar in Mailliard Reaction?

texts:
I'm interested in food science, and I've been reading about Maillard reaction.

All of the articles / videos about Maillard reactions that I found online mention that reducing sugar and amino acids are required for the reaction to occur, but never talks about what kind of reducing sugars are present while searing a steak, roasting a chicken, etc.

When we are cooking a steak with just olive oil, for example, what kind of reducing sugars are present? I initially thought glycogen and ribose in the meat might be acting as reducing sugars, but I learned that most meat we buy don't have glycogen, and there is only a very small amount of ribose present in the meat. Similarly, what kind of reducing sugar / amino acid is present when baking bread?

Lastly, my understanding is that table sugar we buy from stores is sucrose, which is a non-reducing sugar. Does this mean that adding sugar while cooking meat wouldn't help if your goal is to start a Maillard reaction? I know that sucrose does break down to glucose and fructose, which are reducing sugars, when heat is added, but does that break-down occur fast enough for it to be meaningful?

Any input would be greatly appreciated!


texts:
According to some sources, charcoal burns at temperatures as high as 2600 °C (Wikipedia), others (that seem less reliable) say around 1000 °C.

I know that it depends on the air flow, but how high of a temperature can normal charcoal (bought for BBQs) burn? Can it be used to melt metals with a melting point such as iron or steel?


texts:
During a laboratory exercise in a course on analytical chemistry, we were asked to calculate the $z$-score.

  $$z=\frac{X_{\text{lab}}-X_{\text{cons}}}{S_{\text{target}}}$$
  where

  $X_{\text{lab}}$ is some measured quantity (e.g., concentration),
  $X_{\text{cons}}$ is the consensus value for that $X_{\text{lab}}$,
  $S_{\text{target}}$ is known as the benchmark standard deviation

One way of optaining the $S_{\text{target}}$ was to use the so-called Horwitz equation:

  $$S_{\text{target}}=2^{(1-0.5\log C)}.$$
  $C$ denotes the concentration as a dimensionless mass fraction.$^{[1]}$

On the mathematical relationship,  M. Thompson comments$^{[2]}$

  As well as being useful, the Horwitz Trumpet is a feature of considerable theoretical interest. It is hard to avoid the assumption that a simple mathematical law that describes the behaviour of large numbers of methods over at least six orders of magnitude of analyte concentration must have some inherent meaning and deserves serious consideration. So far,
  though, nobody has managed to explain the strange empirical exponent from basic principles, although several people have made conjectures. Are we seeing the manifestation of a physical law here, or is there a psychological basis, perhaps to do with our perception of fitness for purpose?

  There is a sure-fire paper in Nature waiting for somebody!

In statistical terms, why have we chosen such a form for $z$?

This might include an explanation of the relationship with the Horwitz equation.

What are the several conjectures that have been made?

[1] Carlos Rivera, Rosario Rodríguez. Horwitz Equation as Quality Benchmark in ISO/LEC 17025 Testing Laboratory

[2] M. Thompson. The amazing Horwitz function. Royal Society of Chemistry. (2004)


texts: What is the difference between "atomic hydrogen" and "nascent hydrogen"?

texts:
My book (Comprehensive Chemistry by Dr. N . K. Verma, S. K. Khanna, Dr. B. Kapila) mentions two forms of hydrogen — "atomic" & "nascent".

It says that these two forms of hydrogen are more or less the same except that the former is produced by passing $\ce{H2}$ gas through an electric arc struck between two tungsten filaments and the latter is formed during chemical reactions in aqueous solutions. For example, $$\ce{Zn + H2SO4 -> ZnSO4 + 2[H]}$$

The book also said that the reactivity order of these hydrogens is

$$\ce{H2} \lt \ce{[H]} \lt \rm atomic~hydrogen$$

But I think  that the reactivity of $\ce{[H]}$  must be same as atomic hydrogen. So please explain the difference between them and also their reactivity order.


texts: Two possible chains - isopropyl or ethyl and methyl?

texts:
I see two possibilities for choosing the longest branch, and they yield pretty different names:

3-isopropyl-3-hexene
3-ethyl-2-methyl-3-hexene

Is there a rule to determine which to choose? Does one of these prefixes take priority over the other, for example? Or is the second option preferable because of the lower number? I suspect this is a very straightforward rule...


texts:
It has been noted in several sources (e.g. J. Romero et al. Strategies for quantum computing molecular energies using the unitary coupled cluster ansatz. arXiv:1701.02691 [quant-ph]) that one of the disadvantages of the Coupled Cluster method for the description of electron correlation is that, since $e^T$ in
$$E_\mathrm{CC} = \langle0|e^{-T}He^T|0\rangle$$ isn't unitary, the method isn't variational (the energy obtained by solving CC equations isn't a rigorous upper bound to the exact energy).

Could someone please explain to me the connection between non-unitarity of $e^T$ and the method not being variational.


texts: How to obtain reactant lifetime using transition state theory?

texts:
I've read this paper and the authors calculate life times of an intermediate using Quasi-Classical-Trajectories (QCT), RRKM and transition state theory (TST). Table 3 on page 4755 show the results.

If I understand correctly for the QCT calculations they take all (several hundred in that case) trajectories and just do statistical analysis of the lifetime of that intermediate. That perfectly makes sense and they come up with a value +/- error.

For TST they also calculate a lifetime of that intermediate, assuming it is in equilibrium with it's surrounding. This makes me think that they used the reaction barrier from intermediate to product for their calculation of the lifetime. How to do this? Up to now I've only used TST in combination with Eyring equation for calculation of rate constants.


texts: Would the End Point and Equivalence Point be Labelled the Same?

texts:
I created two graphs of two different titrations : One graph was the titration curve of acetic acid with sodium hydroxide (weak acid-strong base) and the other was that of nitric acid with sodium hydroxide (strong acid-strong base). I've marked the equivalence point of the acetic acid curve to be at a pH of ~8.5, while the nitric acid curve has a pH of 7.

Knowing this, where would I label the endpoint of the titration curves? In the same general location? On most of the photos I've researched, people don't tend to label the end point but it's required for this assignment. For the titration, I didn't use an color indicator like methyl red or anything but rather a pH meter. If anyone can give an idea, that would be greatly appreciated.


texts: How to carry out cyclization of 1‐(2‐methylbutyl)‐2‐nitrocyclohexane?

texts:
How the cyclization can take place as there is no other functional group than $\ce{NO2}?$

One way that I can think of is photochemical bromination which occurs selectively at tertiary center which then can be promoted to give cation in polar medium. Nitro group on being reduced to amino group will attack on carbocation, thus closing the ring.
The problem here is that there are three tertiary centers and radical close to functional group will be more stable than the one at the far tertiary center on side chain.
How would you handle this conversion?


texts: Memorizing polyatomic ions? Using Periodic Table

texts:
In my Chemistry course, we must memorize a list of common polyatomic ions. Is their an easy way of memorizing ions such as Sulfate $\ce{SO4^2-}$ by looking at just the periodic table. I listed the ones we have to memorize bellow. I know that if they contain oxygen (which is most of them) they usually end in "ate" or "ite." But how do I know how many Oxygen an ion will contain and its charge. My teacher said the only reference table we can use on our test is the Periodic Table of Elements.

I have to memorize the name and the formulas of the ions. Any methods will be much appreciated. I guess the real question is their any trends in the periodic table that helps predict the charge and number of oxygens and polyatomic ions will have? So if I have Sulfate for example, Can I predict the formula by looking at Sulfur on the periodic table

Update: My question is not a duplicate of When to use -ate and -ite for naming oxyanions? because my question wants to **use the periodic table to identify and memorize polyatomic ion **. Voldemorts question had nothing to do with memorization what so ever!

  But, what I don't understand is how does the book know that NO−3 is Nitrate: how does the book know that NO−3 is "the most common oxyanion for the element". How does it know that a charge of −1 and 3 oxygen atoms create "the most common" Nitrogen oxyanion?

His question had nothing do with specifically looking for patterns in the periodic table to help him or her memorize the polyatomic ions. In fact he or she wasn't even asking for a technique or method to memorize polyatomic ions, but rather figure out which form of a polyatomic ion is "most common." For Example: He wanted to find out how the author of his book knows $\ce{NO3^-}$ is more common than  $\ce{NO2^-}$


texts: Equivalencies and catalytic hydrogenation

texts:
Can we actually control catalytic hydrogenation by introducing specific molar quantities of hydrogen gas? My prof insists on no. No we cannot use a certain equivalency of hydrogen gas to stop at a desired product.

Yet in the book I keep seeing examples of specific molar quantities of hydrogen gas being used ...


texts: I'm am doing research in creating an artificial nose. I need to know how this process works by someone with domain expertise; essentially, what technologies are available currently to detect a broader range of particles in a closed system. My understanding so far goes like this on a high-level overview: particle comes into contact with the olfactory cells and particles from the environment have a custom signature which we associate as smell of a banana or orange, now how to do this artificially or how is this done artificially?


texts: Why is the hybridization of oxygen in the seven membered ring pictured below $sp^3$, while the oxygen has a hybridization of $sp^2$ in the 5 membered ring? This also may be an error in the answer key as well.


texts: Why does N₂ react with O₂ to Form NO at high temperatures?

texts:
This also raises questions that I have about the Haber Process which produces ammonia ($\ce{NH3}$) from molecular nitrogen ($\ce{N2}$) and hydrogen ($\ce{H2}$).

I have heard multiple times that bond between diatomic nitrogen is one of the strongest bonds in nature due to the fact that it is a triple covalent bond that fills the valence shells of both atoms.

I understand that at high temperatures it is possible to break this bond, but I don't understand why the resulting Nitrogen atoms wouldn't simply return to their previous bonds as the temperature cooled.

For example, I read that lightning can result in this reaction:  $\ce{N2 + O2 -> 2NO}$

Why would the atoms not return to their original bonds since they would be more stable in that manner? Is bonding indiscriminate at high energy levels? Completely random and dependent on luck?


texts: What is the activation energy barrier of uncatalyzed nitrogen fixation?

texts:
I'm interested in the activation energy ($E_\mathrm a$) of uncatalyzed aqueous nitrogen fixation:
$$\ce{3 H2 + N2 -> 2 NH3}$$
Biology performs this reaction with the nitrogenase enzyme at room temperature. Humans have come up with ways of doing this reaction with a metal catalyst like rubidium at ~300 °C. I am not interested in the activation energy of nitrogen fixation when catalyzed by biology or by industrial chemists. I want to know the activation energy of the uncatalyzed reaction.

The most luck I have had is with a book titled "Ammonia: Principles and Industrial Practice", which states, "According to estimates[99], the homogenous reaction of nitrogen with hydrogen to form ammonia in the gas phase requires an activation energy of 230–420 kJ/mol." Reference [99] is cited as "W. G. Frankenburger, Catalysis 1954-1960 3 (1955) 171" which I haven't found a copy of yet. I would prefer to have a measured (not estimated) value that is a bit more precise.

Any help would be much appreciated!


texts: How much of Ag has formed on the Cu tile?

texts:
$\pu{9.547 g}$ $\ce{Cu}$ tile is added to an $\ce{AgNO3}$ solution. After some time, $\ce{Cu}$ was taken out of the solution, washed, dried and weighed. The mass appeared to be $\pu{9.983 g}$. How much of $\ce{Ag}$ has formed on the $\ce{Cu}$ tile?

The right answer to be found is supposed to be: $\pu{1.08 g}$.

My imaginary equations (with unlikely scenarios):

\begin{align}
\ce{Cu + 2AgNO3 &-> Cu(NO3)2 + 2Ag}\\
\ce{Cu + AgNO3 &-> CuNO3 + 2Ag}
\end{align}

I cannot solve this problem. There are a few others, but this is bugging me the most. How does one solve it? I believe this is something I wasn't taught before or there is again a mistake in the references given.
I've tried calculating in ways I thought was right and anyhow, I cannot find the answer.

After discussions, I have come to the conclusion that I am taking $\pu{0.618 g}$ as the solution to this problem and will look forward into it tomorrow with the teacher as well.
This is the only closest answer I seem to arrive at by myself and others, as we get $\pu{0.618 g}$ when using the $\Delta m_\mathrm{p}=\pu{0.436 g}$ and $\Delta m_\mathrm{t}=\pu{22.853 g}$ differences. However, the problem regarding the other exercises still persists, which are of similar nature.
I am starting to question my teacher's logic and abilities.

There is a close answer to the referenced answer, which assumes the $\ce{Cu}$ having a charge of $+1$, thus $\ce{Cu + Ag+ -> Cu+ + Ag}$ and $\Delta m_\mathrm{p}=\pu{0.436 g}$, $\Delta m_\mathrm{t}=\pu{16.2 g}$.
However, I assume that to be a very unlikely scenario considering the current circumstances. This scenario lets you acquire \pu{1.0617 g} as the answer.


texts: Why do most drugs (eg: oxycodone) have seemingly arbitrary names?

texts:
How do some medicines derive their names?

For instance, is the name oxycodone somewhat arbitrary? I am not well-versed in Chemistry (1st semester student) but does the prefix oxy- imply some chemical meaning as well as the -codone such as some sort of functional group or grouping of molecules?

I realize such nomenclature such as di- implies "two".


texts: What is the difference between nuclear charge and ionic charge?

texts:
There was a question asking why magnesium metal has a higher melting point than sodium.

In the answer, they said:

  Magnesium has more delocalised electrons.
  Magnesium ions have a greater positive charge.
  Magnesium has a greater electrostatic attraction between ions and delocalised electrons.

However, in the mark scheme in the additional guidance, it also said the mark couldn't be given if you said:

  Magnesium ions have a great nuclear charge rather than greater positive charge.

I was confused as to what the difference is.


texts: Why not use all the colours in colorimetry?

texts:
Colorimetry (and it's cousin visible-UV spectroscopy) is a form of chemical analysis that works by sending visible light of one wavelength through the sample. It then analyses how much of the light was absorbed in that process so you can determine concentration.

What I don't understand is why only one wavelength is used. Apparently, even for Infrared Spectroscopy, only one wavelength is analysed at one time yet the whole spectrum is needed. Why not send in white light (with all the wavelengths at once)? The output light could be split through dispersion and every wavelength could be analysed for its absorbance. Perhaps some wavelengths of light aren't worth measuring or too many frequencies at once cause interference?


texts: I'm looking to reflux a 250 mL of ethylene glycol solution. Would an Allihn condenser be suitable; if so what length?


texts: Is electrolysis with AC current possible?

texts: Optimizing everything else, would efficient electrolysis be possible with AC current? Most sources suggest to use DC, but can the water still be split/disassociated with AC?


texts: Hybridization of Oxygen in Orthoboric Acid

texts:
What should be the hybridization of the oxygen atom?

A) It should be $\mathrm{sp^2}$ as 1 lone pair must be in the unhybridized orbital for back bonding with boron which has a vacant p-orbital
B)It should be $\mathrm{sp^3}$ (2bp + 2lp)

(In my book it is given as $\mathrm{sp^3}$ but I cannot find a reason to rule out option A. I am not convinced with option B.)


texts: Are enzymes with superior catalytic properties more sensitive to temperature changes?

texts:
I am wondering whether enzymes with superior catalytic properties are more or less temperature sensitive than average enzymes.

I know that enzymes lower the activation energy, Ea. So the more catalytic superior an enzyme is the lower the value of Ea. Then the Arrhenius equation can be used to describe how the rate constant of an enzymatic reaction changes with temperature. But how can I use this information to decide whether the more catalytic enzyme is more or less temperature dependent?


texts: Is the solution isotonic, hypertonic, or hypotonic?

texts:
The problem is shown below. I don't understand how can the tonicity of a solution be determined if the solution has multiple solutes dissolved in it.

Do I take the total sum of the mass of solutes and divide it by the volume of the solution in both outside and inside of the cell (total concentration) and determine the osmosis direction based on whichever is greater? Or should it be done in another way?

If it could be of use, here are the questions that were asked below the picture and their answers. This question was taken out of a test-bank for the 8th edition of the Campbell biology textbook.


texts: How to manage complex equilibria when studying a mecanism?

texts:
Consider a complex multistep reaction mechanism with several intermediates. There are multiple possible pathways as well as equilibria in solution. One wants to study the reaction mechanism using computational chemistry.

It is easy to calculate the $\Delta G$ and $\Delta G^\ddagger$ of individual reactions, but how do you take in consideration all the possible equilibria?

For example, consider an aldol reaction in presence of water (taken from Wikipedia):

Acetone can be either as a ketone, a protonated ketone, an enol or an enolate. This means that there are 16 possible pairs (although only 4 which make sense). These will yield different intermediates, which can dehydrate in different ways (ex. by protonation of the hydroxyde first or not, through a ketone or an enol or an enolate...)

In this case, many possibilities could be eliminated as too high in energy just by general knowledge of chemistry, but if you don't know enough about the system, how do you tackle this problem? How do you handle all the equilibria possible?


texts: Mechanism for Hydrogen Peroxide decomposition?

texts:
Someone asked this question earlier and made no attempt at understanding it on their own so the question was flagged.  However, it prompted me to attempt to figure it out.  This is what I have come up with, and the reason I'm asking about it is I found the mechanism quite interesting (if it is indeed the mechanism).

The first step is of course the breakage of the $\ce{O-O}$ bond in hydrogen peroxide to form 2 hydroxy radicals ($\ce{H - O•}$)

In the second step, a hydroxy radical reacts with an unsplit hydrogen peroxide molecule to form water and a peroxy radical ($\ce{H - O - O•}$).

In the third step, two peroxy radicals react to form a molecule of hydrogen peroxide and what google terms "triplet oxygen" with the structure $\ce{•O - O•}$.  Heres the interesting part, if I am indeed correct.  The triplet oxygen goes through an intramolecular free-radical termination reaction to form oxygen gas.  It may be more complicated than an intramolecular reaction.  I only assumed this is what happens based on my knowledge of intramolecular friedel-crafts acylation, which is much faster than intermolecular friedel-crafts acylation.  This is due to intramolecular acylation having no change in entropy (one reactant forms one product) while intermolecular acylation has a decrease in entropy (two reactants form one product).

This would be quite interesting if it is indeed the mechanism!

Edit: Regardless of whether or not the oxygen gas is formed by an intramolecular free-radical termination, I do believe this is the correct mechanism because the sum of all the elementary reactions produces the overall reaction of:

$$\ce{2 H2O2 -> 2 H2O + O2}$$

Elementary steps:

1)    $\ce{H2O2 -> 2 HO•}$

2)    $\ce{2 HO• + 2 H2O2 -> 2 H2O + 2 HOO•}$

3)    $\ce{2 HOO• -> H2O2 + •OO•}$

4)    $\ce{•OO• -> O2}$

Do correct me if I am wrong though


texts:
I'm writing a computer program to help a factory produce bottles of mixtures. A mixture is usually alcohol, water and some other stuff, like menthol. But could also be water and NaOH and some oils (think schampoo).
My basic understanding is that if one bottle is 500 ml and contains:
50% water
45% alcohol
5% oils
I need:
250 ml water
225 ml alcohol
25 ml oils
Then if I want to make 1000 bottles I just multiply this with 1000:
250000 ml water
225000 ml alcohol
25000 ml oils
However this is with the assumption that all mixtures have linear dependencies.
So my questions is:

Is all (possible) mixtures linear?
Are all reactions linear?
Are there a difference between mixtures and solutions here?

I suspect this is a very easy question for someone who know chemistry, but unfortunately my understanding is basic and my search skills too bad to find this out.


texts:
When I went to the supermarket, I noticed that some of the product say sunscreen and some of them say sunblock.

My question split into two part.

1) What are the different chemical substances use in both item? (In general)

2)What is more effective to prevert sunburn? (In general)


texts: What happens at equilibrium for two solutions that produce gasses?

texts:
Suppose one has two chemical reaction equations:

$\ce{A_{(aq)} + B_{(aq)} <=>[H2O] C_{(g)} + D_{(g)}}$

and

$\ce{A_{(s)} + B_{(s)} <=> C_{(g)} + D_{(g)}}$

Suppose one puts 0.1 mol of A and 0.1 mol of B into 1 litre of water. The water is contained in a closed rectangular container that can hold up to 2 litres of material.

The produced gasses C and D are lighter than water and so float up out of the water into the top of the container where they can't react . So if some equilibrium is reached for A and B in the water where they do not react any more it has to be of the form $k_{\mathrm{eqc}} = \frac{1}{{c_{\ce{A}}} {c_{\ce{B}}}}$ unless A and B completely and totally react together into gasses or do not react at all to form gasses.

The produced gasses C and D float up out of the water and when they react in the air they produce heavier solids A and B which fall to the water at the bottom and then dissolve into ions.  As there are no A and B products in the air any equilibrium for C and D has to be of the form $k_{\mathrm{eqp}} = {P_{\ce{C}}} {P_{\ce{D}}}$ unless C and D always completely and totally react together to form solids or do not react at all to form solids.

What happens here?

I think I'm making a mistake where I'm not factoring pressure in somehow.


texts: A little help understanding some basic algebra(I think) in conversion pathways

texts:
Attached is a picture from my textbook.

Here is my question:

Must the 3.18cm(1.25in X 2.54cm) have to be cubed(^3) in order to cancel the cm in the 1cm^3 that is beneath the 22.59g Osmium?

Is that a standard rule in algebra? And if it is, under what section might I find it.

I've looked in Blitzer's 6th edition of Introductory Algebra for a clue but didn't find anything there. I've checked out Principles of General Chemistry by Martin S. Silberberg for a similar conversion but didn't find anything similar; all there was in that chemistry text book were much easier conversions.

I've even gone onto youtube and searched "multiplying fractions with unit and exponents" but couldn't find anything.

I find it strange that the entire cm^3 doesn't cancel out and just the cm does.But cubing the 3.18cm is necessary to arriving at the given answer. I could assume that the 1cm^3 should be cancelled, but we cannot cancel the cm^3 on one side and not cancel the cm^3 on the other side, but if we did that, we would be removing the ^3 which is necessary to arriving at the given answer.

Thank you all


texts: Why are branched alkanes used as fuels instead of straight chain alkanes?

texts: My textbook states that branched alkanes are thermodynamically more stable than straight chain alkanes. Of course, iso-octane has an enthalpy of formation of $\Delta H_\mathrm f$= $\pu{-259.3.40 kJ mol-1}$ and n-octane has an enthalpy of formation of $\Delta H_\mathrm f$= $\pu{-249.73 kJ mol-1}$ which indicates that iso-octane is relatively more stable than n-octane at room temperature. When they are used as fuels, both produces energy and the enthaply of combustion of iso-octane would be less than enthalpy of combustion of n-octane. So, n-octane should be more efficient fuel than iso-octane. But in petrol, iso-octane has more composition than n-octane. Why?


texts:
I am confused regarding significant figures. Consider "Calculate the volume of 2.8 kg of liquid with density of 1.11 g/cm^3"

Then,
Volume = 2.8 kg * (cm^3 / 1.11 g) = 2522.522 (where 522 is recurring).

Since the original figure (2.8 kg) has only two significant figures, I thought the answer should be 2.5 kg.

The textbook says the answer is 2.523 kg, which is four significant figures.

Which is correct?


texts:
Why is the cathodic reaction of $I^-/AgI/Ag$ is $$\ce{AgI + e-  -> Ag + I-}$$ but not,
$$\ce{Ag+ + e- -> Ag }$$

whereas, in $Ag/AgCl(s)$, $KCl$(0.2M); it is
$$\ce{Ag+ + e- -> Ag}$$


texts: Electrolysis for rust removal: is "line of sight" a showstopper?

texts:
So I am using electrolysis to remove rust from a fuel tank.  The tank is the cathode and a sacrificial anode is inserted where the fuel pump normally goes.  It's not practical to put it anywhere else.
However, the fuel tank has internal baffles, apparently for anti-slosh.  They have continuity with the tank, i.e. they are part of the cathode.
It cannot be denied that the the tank is getting a lot cleaner, and formerly-rusty areas are becoming shiny.  And it's difficult to tell for sure, but subjectively, it seems like it's not doing so well in parts of the tank placed "in shadow" by the baffle, i.e. the baffle interrupts line-of-sight to the anode.  This is more obvious where there are holes in the baffle.

My setup, and what seems to be happening.
So my question is: Is line-of-sight a requirement for electrolysis?  Does electrolysis happen through the electrolyte (acting on all wetted surfaces) or does it only use the most direct path between anode and cathode?
Electrical current takes all paths in proportion to their conductance... so will the path through the electrolyte around the baffle eventually have effect?


texts:
To determine the free $\ce{SO2}$ in wine, a common method used is called the Ripper Titration Method.

The equation is as follows: $$\ce{SO2 (aq) + I2 (aq) + 2H2O (l) -> 4H+ (aq) + SO4^2- (aq) + 2I- (aq)}$$

This method involves titrating an Iodine solution into a sample of wine. I have found that triiodide is made from reacting $\ce{I-}$ with $\ce{I2}$. However, if it is the triiodide we are titrating, how is the iodine reacting with the wine?

Is it triiodide ($\ce{I3-}$) that is being titrated with the wine sample or iodine ($\ce{I2}$)?


texts: How to compare standard entropy of diatomic gases?

texts:
Say, for example, I wanted to compare the standard entropies of $\ce{Cl2(g)}$ and $\ce{F2(g)}$. They both are equimolar.

I understand that entropy is a measure of how many states a particle can occupy (loosely speaking), so I tend to think the larger chlorine molecule has higher standard entropies. This is backed by experimental data, but why?


texts: Why do you need excess LAH to reduce esters?

texts: I am little confused on this question. On one hand, I remember my teacher saying that $\ce{LiAlH4}$ is like $\ce{BH3}$ of hydroboration oxidation of alkene, where you one mole of $\ce{BH3}$ can oxidize 3 mole of alkene molecule. but on the other hand my textbook keeps on mentioning excess LAH when reducing ester? Can't one mole of LAH reduce four mole of ester molecules as well? Thanks.


texts:
Is there a way to map smells to numerical values of different variables?

I.e. With RGB colours, each colour is made up of numerical values from 0-255. For example, red is (255,0,0), and yellow is (255,255,0). Is there a way to do this with smells. I.e, the smell of Candy is (140,70,255), and the smell of grass is (255,34,27)? How many different sets of numbers (like red, green and blue) would you need, and what would they represent?


texts: How much CO2 could you remove from the atmosphere with 2 trillion USD?

texts:
I know it's possible to capture $\ce{CO2}$ with various chemical reactions. For example NASA's space shuttle had some kind of regenerative $\ce{CO2}$ scrubber. But how expensive is it? Could a huge number of these devices, or something like it, significantly reduce the atmosphere's $\ce{CO2}$ level?

I realize this is probably not practical, but it's an interesting thought experiment. To make my question more specific: can anyone show some rough calculations of how much $\ce{CO2}$ you could remove if you had, say, 2 trillion USD to spend? To simplify, assume that energy is at current prices, but clean. (i.e., if the device requires electricity, assume it's coming from a nuclear power plant, solar farm, etc.).


texts:
10 g of substance below were dissolve in each 1 L water:
$\ce{Na2SO4}$
$\ce{NaCl}$
Glucose
$\ce{MgCl2}$
Which one has the highest boiling point?

Glucose has London dispersion force.
$\ce{Na2SO4},$ $\ce{NaCl},$ $\ce{MgCl2}$ have ionic forces.
Ionic forces is stronger than London dispersion force, so $\ce{Na2SO4},$ $\ce{NaCl},$ $\ce{MgCl2}$ have higher b.p. than glucose.
Now, how to decide which one has highest b.p. among $\ce{Na2SO4},$ $\ce{NaCl},$ $\ce{MgCl2}?$


texts: Why does Oxygen act as Nucleophile over here?

texts:
We were taught in class that when a carbon atom and an oxygen atom both have a negative charge in a resonating structure, then carbon atom attacks the nucleophile rather than oxygen atom because it acts as a better nucleophile.

In the question I have attached, in the first step the hydroxide ion abstracts the hydrogen from the oxygen of o-cresol. The negative charge so formed is delocalised onto ortho and para position.

There are 4 possibilities:

Oxygen atom attacks $\ce{CH3I}$.
The carbon atom attached to $\ce{CH3}$ attacks.
The carbon atom adjacent to oxygen (not attached to $\ce{CH3}$) attacks.
Carbon at para position attacks.

Now, based on the statement that Carbon atom should attack, Option 1 should be ruled out.
Option 2 also is unfavourable because the carbon atom attached to $\ce{CH3}$ would have less negative charge due to inductive destabilisation by $\ce{CH3}$.
Option 3 is unfavourable because the product formed would be sterically crowded.
Option 4 seems correct.

But the answer given to the above question is Option 2.

I confirmed from my teacher and he says that the statement that Carbon atom is a better nucleophile than oxygen is true but here attack from oxygen would take place (he doesn't explain why).

Also, in the well known Riemer Tiemann Reaction and Kolbe Reaction of Phenol, the attack takes place from Carbon side.

Question- where is my reasoning wrong? According to my reasoning, answer should be Option 1. Why isn't it?


texts: Redox reaction: Iron(III) and Iodide ion

texts:
I'm a real beginner in chemistry and I'm currently reading about redox reactions. I'm quite confused about this simple redox reaction:

  ${\text{Iron(III) ion + Iodide ion} \rightleftharpoons \text {Iron(II) ion + Iodine}}$
  \begin{array}{|c|c|c|c|c|c|}
\hline
\text{Oxidation numbers}& +3 & -1 &\rightleftharpoons & -1 & 0\\ \hline
 & Fe^{3+}& I^-&\rightleftharpoons & Fe^{2+}&I_2\\ \hline
\end{array}

I understand the principles of transferring electrons. But how would I come from the upper formula to the result that the Iodine exists two times on the right side? After reading the reaction formula I would have written the Iodine just once (not as seen here twice).


texts:
Can't we perform Fischer esterification using methanol to make a methyl ester from a carboxylic acid?

If so, why might we use diazomethane? Would the release of nitrogen gas confer an entropic advantage to the reaction? As I understand, the Fischer esterification process is an equilibrium process and at equilibrium there is often significant amounts of both product and reactant. So we might have to add excess alcohol to drive the reaction to the right.

I ask because my book just presents the use of diazomethane as a way of making methyl esters without any discussion of why might someone do this rather than just use a few gallons of methanol.

On the other hand I know from working in a research lab that methanol is poisonous and protocol calls for its use in a fume hood ... could that be another reason? On the other hand diazomethane is also toxic (and explosive to boot) ... so I would definitely be inclined to use that in a fume hood (perhaps more so than when using methanol).


texts: Chemical reaction of radicals with different multiplicity

texts:
I am studying the chemical reaction of radicals by computational chemistry software.
I just want to know what is the rules for multiplicity.
I have two radicals for which, the ground state of one is a doublet and the other is a triplet.
A chemical reaction between them is possible or not, if a chemical reaction is possible then in what multiplicity the reaction will proceed.
what multiplicity should I use in my input file?


texts: Do radioisotopes emitted particles influence their chemistry?

texts: Supposedly, a isotopes have the same chemistry, i.e. how they bond to other atoms. Is this true for radioisotopes?  I can imagine a nucleus emitting particles that interact with existing bonds in its outer shell, i.e. it may break an existing bonds, or reconfigure them. Does this happen at all?


texts: Improving Elephant Toothpaste experiment

texts:
we are trying to perform the Elephant Toothpaste experiment involving the reaction of yeast and Hydrogen Peroxide for the students at school.

However, the results have been very underwhelming, likely because we have to use the 3% version of Hydrogen Peroxide.

My question is: What are some other ways to help create a stronger propulsion or thicker foam?

Some things I have been experimenting with are reducing the water mixed with the yeast, and swirling the bottle to mix the yeast and Hydrogen Peroxide. Any advice is much appreciated.


texts: Enol form of acetone is treated with D2O

texts: Could find the mechanism in brief online. Still have few queries. What makes the D2O not attack the the central carbon (to which OH is attached) and choose other the carbon instead (both have a double bond). Again, in the 'repeat' part of mechanism, there's only one carbon with double-bond (carbonyl group). Why does D2O attack the second carbon again and not the carbonyl group one? I'm really confused.


texts: Could you make a helium atom from hydrogen gas?

texts: Hydrogen gas is $\ce{H2}$, and contains 2 electrons and 2 protons. My question is, with sufficient pressure, could you fire two neutrons at the molecule and have them form a single Helium atom?


texts:
It is well known that the A in both DNA and RNA stands for acid, but where is the acid in chemical formula for the compound, and it is classified so based on what acid-base theory? Like Arrhenius, Brønsted-Lowry or Lewis.

Just to better explain my question, when I say DNA I am essencially thinking about nucleotides linked together, am I missing something in the structure that contains my answer or this is the way to go?


texts:
When molten glass is dropped into water you can get tear shaped objects which are both incredibly strong and which have massive internal stresses. Which means any scratch can cause them to explode.

Is this only a feature of glass, or would it apply also to molten Alumina (Aluminium Oxide)?


texts:
I happened to stumble upon this Nature Chemistry article today. It claims that

  [...] use a 3D printer to initiate chemical reactions by printing the reagents directly into a 3D reactionware matrix, and so put reactionware design, construction and operation under digital control.

Unfortunately, I cannot obtain the full article to read, but even the abstract does not seem plausible in my opinion. My questions are...

How can one "print reagents"? What is meant by this?
Most synthetic reactions require hours of refluxing and whatnot, not to mention isolation/purification afterwards. How can all of these techniques be performed with a printer?

Perhaps I'm not "getting it", but the abstract of the article isn't providing me with the explanations and theory I'm looking for. How can something like this be possible?

References

Symes, Mark D., Philip J. Kitson, Jun Yan, Craig J. Richmond, Geoffrey J. T. Cooper, Richard W. Bowman, Turlif Vilbrandt, and Leroy Cronin. “Integrated 3D-printed Reactionware for Chemical Synthesis and Analysis.” Nat Chem 4, no. 5 (May 2012): 349–354.


texts:
Determine the equivalence ratio of the following mixture: 4g of Butane, $\ce{C4H10}$, and 75 grams of air.

Answer is 0.82

Ok so I try converting everything into mols

$4~\mathrm{g}~(\ce{C4H10}) \times \frac{1~\mathrm{mol}}{58~\mathrm{g}} = \frac{4}{58}~\mathrm{mol}$

$75~\mathrm{g~(Air)} \times \frac{1~\mathrm{mol}}{28.966~\mathrm{g}} = \frac{75}{28.966}~\mathrm{mol}$

Air-fuel ratio = $\frac{\frac{75}{28.966}}{\frac{4}{58}} = 37.54$

This is just a guess that the air-fuel ratio is some sort of equivalence ratio.

I saw that equivalence ratio =  actual air-to-fuel ratio divided by the theoretical. I don't know how to get either actual or theoretical? Is the data in the problem sufficient enough to get both?

I also see a formula in the reviewer: Fuel + Air = Products of combustion and the appropriate reaction, but it only works for finding the exact amount of mols like: $\ce{C4H10 + aO2 + 3.76aN2 = bCO2 + CH2O + 3.76aN2}$

This is for a mechanical engineering board exam review; unfortunately, university only tapped briefly on the chemistry side of fuels.

Any hint on what I should be doing? Point me to the right direction?


texts: Hydrogen bond strength of trichloromethane and chloromethane

texts: Chloromethane has a larger dipole moment than trichloromethane. Does that mean that the hydrogen bond (C-H...O type) between chloromethane and acetone is stronger than that of trichloromethane and acetone?


texts: Why are the OV and VO blocks of the CIS 1RDM zero?

texts:
I know the reduced density matrix has the form:
$$
\gamma(\alpha,\beta) = \langle\Psi_N|c^{\dagger}_{\alpha} c_{\beta}|\Psi_n \rangle
$$
but when $\Psi_N$ is the configuration interaction singles (CIS) wavefunction, why are the occupied-virtual (OV) and virtual-occupied (VO) subblocks zero?  I see multiple references state that it is due to Brillouins Theorem, but I don't entirely see that connection.


texts: Why are partial molar Gibbs energy and Gibbs energy per mol equal?

texts:
I'm not a chemist, but I need some insight into chemical thermodynamics.

In the book that I'm reading (Nevers, 2012), equation (4.28) relates the chemical potential of a pure species to it's Gibbs energy per mol:

$\qquad\mu_a^{(1)} = \bigg( \dfrac{\partial G}{\partial n_a} \bigg)_{T,P,n_b...} = g_a^{(1)}$

where the subscript stands for the species $a$, the superscript stands for it's phase, $\mu$ is the chemical potential and $g$ is the Gibbs energy per mol.

I understand the first equal sign. Though, I don't understand the second equal sign. What am I missing?


texts: What kind of bond exists between a metal and a non-metal with a difference in electronegativity of less than 1.7?

texts:
I'm being taught that the kind of bonds that exist between elements depends on the electronegativity difference between the elements. A difference less than 1.7 is covalent and a difference higher than 1.7 is ionic.
Separately, I've been taught that bonds between metals and non-metals are ionic. What happens when these two 'rules' disagree? When Magnesium and Phosporus bond for example.
I understand that there isn't always a definite border between covalent and ionic bonding, but what should my rule of thumb be? That bonds between metals and non-metals are always ionic, and that bonds between non-metals are covalent unless there's a difference of more than 1.7?


texts:
I can't understand why 2-methylpropane has/needs the 2 in front of it?

It appears to me that if you were to add the methyl group at the first or last carbon on the chain then you get plain old butane and so defining 2-methylpropane is unnecessary when it could just be methylpropane.

Have I missed something or is this just a convention? Apologies if it's a really simple question; it's my first ever time studying organic chemistry.


texts: Confused with 'discharge potential',preferential discharge theory

texts: My book says that the ions which have least value of discharge potential are deposited first in the concerned electrode  because the 'require' the least energy to do so.I am confused by 'require' , do ions upon discharging gain energy or lose energy , are ions in general not less stable than neutral counterparts?further,suppose there are two contenders for the same electrode, say sodium ion and hydrogen ion during alkaline electrolysis of water , what is the need of adding the base , what actually is it doing and how does it improve electrolysis ?


texts:
In comparing hydroxylamine, hydrazine, and methylamine for basicity, the order of increasing basicity is hydroxylamine < hydrazine < methylamine.

I tried to reason this trend based on electron donating power of the -$\ce{OH}$, -$\ce{NH2}$, and -$\ce{CH3}$ groups, however that yields the order of basicity: methylamine < hydroxylamine < hydrazine, because more electron-donating power concentrates electron density on the nitrogen atom, making it more basic.

Other factors, such as steric hindrance, do not seem to be impacting anything here, because $\ce{-OH}$, $\ce{-NH2}$, and $\ce{-CH3}$ groups are all around the same size.

What is the key factor that influences the basicity here? I realize that hydrazine has two nitrogen atoms, whereas hydroxylamine and methylamine have one nitrogen atom, so that may be affecting the basicity.


texts: Mercury binding agents which cross the blood brain barrier

texts: The two substances I have come across are cilantro and lipoic acid. How effective would either of them be? Are there any other agents known which produce the desired results?


texts:
To my understanding, an increase in pressure (of gases in a container) is proportional to an increase in gases' kinetic energy, and hence temperature. However I read that gases liquify under pressure... However, gases liquify in colder temperatures, so how come gases liquify under pressure, where the temperature increases?

Thanks to all responses.


texts:
Lyases are a class of enzymes that break down (lyase: ly- = lysis, -ase = enzyme) bonds like $\ce{C-C, C-S}$ and so on (except hydrolysis), and can eliminate molecules like $\ce{H2O}$ or $\ce{CO2}$. They are referred to as synthases, respectively, some authors categorize synthases among lyases.

My question is, (if word "synthesis" still means joining two substances into one more complex by creation of bonds between them), why are synthases placed among lyases if lyases actually break down bonds and synthases are (by their name) supposed to join, create bonds? Respectively, why was their name derived from 'synthesis' if their role actually is to break down?

Lastly I have even seen that JCBN (Joint Commission on Biochemical Nomenclature) dictated that "synthase" may be used for any enzyme catalysing synthesis, and that even without paying attention to whether the enzyme uses NTP like ATP (ligases = synthetases) or not (synthases).

I'd like to let everybody know that I understand the difference between synthases and synthetases, and that this difference isn't my point of question. I also do not controvert the fact that in the literature synthases are referred to as lyases, but somehow I kind of miss logic of naming enzymes responsible for breakdown after 'synthesis' which is actually opposite reaction than analysis. Until today I thought 'synthesis' stands for joining (syn-) and 'analysis' for breakdown into simpler products.

Here I attach in the images the answers from Wikipedia and forums for you to read.


texts: If Substance A is more soluble in water than Substance B, will Substance A be more easily absorbed by the body?

texts:
I am comparing the solubilities of artificial vs natural sweeteners for my Chemistry IB Internal Assessment. I must demonstrate personal engagement, so I am relating my topic to weight management in which I am saying that if a sweetener is more soluble in water, then it will be more easily absorbed by the body. Ergo, since the body's need for carbohydrates has been satiated, one will feel less need to eat sugar, thus aiding in weight loss.

I'm not quite sure if the above is true, so I would be very open to any suggestions or corrections. Please indicate any reference material in your answers to my question.

Thank you very much!


texts: Is the pyrolysis of tetrachloroaluminate(III) anion possible?

texts: Wikipedia says that lithium tetrafluoroborate decomposes to lithium fluoride and boron trifluoride when heated. Does the same hold for sodium tetrachloroaluminate (all anhydrous) as well?


texts: Can sodium acetate anhydrous be used as a desiccant?

texts: Sodium acetate trihydrate can be converted to sodium acetate anhydrous easily with an oven. I've been told to quickly store sodium acetate anhydrous in a sealed container because it takes water from the air and turns back into the trihydrate form. It's also non-toxic, and is even sometimes used as a food additive. For these reasons, would sodium acetate anhydrous be viable as a desiccant? Perhaps as a less-toxic replacement for silica gel?


texts:
With reference to the periodic table’s d-block, are the terms “transition metals” and “transition elements” interchangeable when describing these elements?
Are there any situations where it would be incorrect to use one phrase instead of the other?


texts: Naming a cyclic organic compound with multiple functional groups

texts: Why the IUPAC name of the compound is 5-hydroxycyclohex-3-en-1-one and not 3-hydroxycyclohex-4-en-1-one?


texts:
I've managed to get myself thoroughly confused in thinking about the vapor pressure of a substance at a particular temperature $T$, and how it relates to the pressure of the substance if it is in a phase equilibrium at that same temperature $T$.

Consider two sealed, rigid containers.  All three containers are in thermal equilibrium with a large temperature reservoir at (say) 298 K.

We evacuate Container A completely, and place into it a sample of liquid water.  Some of the water boils away until the pressure of the water vapor attains the appropriate pressure on the phase boundary in the P-T diagram.  (We assume that the sample of water is appropriately sized so that some water is left in each phase once it reaches equilibrium.)  Once equilibrium is reached, the water vapor has reached a pressure $P_A$.
Into Container B (which is of the same size) we also place an indentical sample of water.  However, Container B also contains dry air at $P_\text{air} = 1$ atm.  The water evaporates, mixing with the air, until it reaches a particular vapor pressure.  (Again, assume that the sample of water is appropriately sized so that some water remains unevaporated in equilibrium.)  Once equilibrium is reached, the water vapor has partial pressure $P_B$.

  Does $P_A = P_B$ exactly?  Or, to put it another way, does the value of $P_\text{air}$ affect the partial pressure of the water vapor in equilibrium?  If $P_A \neq P_B$ precisely, is there some limit or approximation under which $P_A = P_B$ exactly? If so, what is it?

I haven't been able to find a definitive answer in my searching online, and it seems plausible to me that the presence of an external source of pressure on the water (namely the air in container B) might affect the phase transition properties of the water.


texts: Why does sulfonation of aniline occur para rather than ortho?

texts:
According to a textbook by K. L. Chugh:

  Sulfonation [of aniline] is a reversible reaction. The p-isomer, being more stable, does not get desulfonated easily. Hence, p-sulfanilic acid is the major product.

I am curious as to why the ortho isomer (2-aminobenzenesulfonic acid) is not more thermodynamically stable. There is a possibility of intramolecular hydrogen bonding (in a six-membered ring):

Why is the para isomer (4-aminobenzenesulfonic acid) favoured?


texts: How to model 98% ethanol solution concentration graph over time

texts: İ want to plot a graph of ethanol solution concentration over time .So we know that alcohol evaporates quickly in open air but is there a time when the rate of evaporation mathces that of water and concentration stops decreasing or increasing? İ know surface matters but lets assume surface is totally hydrophobic and doesnt interact with solution.Any ideas how to do it?


texts: Can whatever is special about quasicrystals be understood at A-Level standard or slightly above it? The material I saw online is either too layman or too advanced for me to follow. What practical uses do they have and why does their structure lead to the properties that allow them to have these practical uses?


texts: Why are elimination reactions in organic chemistry known as beta eliminations?

texts: Why are organic elimination reactions known as beta eliminations? Why don't we call them alpha eliminations?


texts:
The qualifier 'free' seems to be ubiquitously attached to discussion of radicals as highly reactive species with unpaired spins. What, precisely (or imprecisely, as the case may be) does 'free' really mean?

Free as in free speech? Free beer? Freedom of movement? Kinetic accessibility?


texts: Which is a dye: Ferric Acetate or Ferrous Acetate?

texts:
I’ve been trying to make Iron Acetate to dye leather and I cannot, for the life of me, figure this out experimentally.
I’ve been allowing steel wool to react with pure white vinegar in a sealed glass vessel with a pressure release for about a month. It turns dark black to green which I assume is due to the ferrous acetate ($\ce{Fe(C2H3O2)2}$). It also contains orange particulates that I assume are the ‘insoluble in water’ salt complex basic iron acetate, Ferric Acetate $\ce{[Fe3O(OAc)6(H2O)3]^+}$.
The solution has dyed leather black and acted as a mordant, and I assume it is a reducing agent. I’ve been trying to separate the iron acetates but I don’t know what properties they each have. Here’s the question:

Which is the dye? Which one turns leather and wood black? Any information anyone has on the properties of either one would be immensely helpful.


texts: What does it mean if a functional group has "higher priority" in terms of IUPAC naming of organic compounds?

texts:
What does "higher priority" mean exactly in the following statement from this wikipedia article (article name: "E-Z notation") on naming organic compounds in IUPAC nomenclature of organic compounds?

  If the two groups of higher priority are on opposite sides of the
  double bond, the bond is assigned the configuration E (from entgegen,
  German: [ɛntˈɡeːɡən], the German word for "opposite").


texts: What is the interaction between dissolved ions of opposite valence in a solution at rest?

texts:
NaCl is dissolved in water. Ions sodium and chloride are sufficiently free from each other so that they may occupy different regions of the solution after an active transport process through a membrane, or a mere electric field is in place.

They still act upon each other, and a membrane voltage is set by oppositely charged ions lining its interior and exterior surfaces.

So my question is this: how free are those ions in a uniform solution at equilibrium? Aren't they actually forming pairs of watered ions, although weakly bound? Can they form even bigger clusters, be them of short lifetime?

Note: I originally asked this on Physics SE but after several weeks I have received no answer nor any other kind of reaction, so I am trying Chemistry SE now.


texts:
Recently I have watched a video demonstration with a sponge and mercury and the sponge can't absorb mercury like it does with water.

Why is that?


texts:
I was hoping an actual person could offer me some advice. I work in a craft distillery and I'm getting a lot of mixed information on how compatible PVC is with high-proof alcohol. It definitely seems that "Food-Grade" doesn't necessarily mean "Alcohol-Grade".
A. Is PVC hose safe to use for transferring Grain, Water, and most importantly, Ethanol?
B. If not, is there a type of material you would recommend for any and all distillery applications?


texts: Local resolution of a crystal structure in PDB File (protein data bank)

texts: I am wondering if it is possible to find the local resolution of a crystal structure. Usually, the resolution of the PDB is assigned the resolution of the highest resolved part of the protein/nucleic acid. However, it is actually a range of resolution (ie. 2-8 A). I am wondering if it possible to extract the resolution of each atom from a PDB file?


texts:
Can a dextrose / caffeine powder be (mostly) separated by dissolving in water then filtering the water?

Dextrose is readily soluble in water (1-10 parts solvent to 1 part solute).
Caffeine anhydrous is sparingly soluble in water (30-100 water : 1 caffeine).

I'm assuming water would dissolve nearly all the dextrose (and a bit of caffeine), and upon reaching saturation, the caffeine will remain out of solution in solid form and easily filtered.

Repeating the process would refine (increase) the quantity of caffeine vs. dextrose in the remaining filtered solids.

Thoughts?

References:

Caffeine Anhydrous - BASF

Dextrose - NBS


texts: Inorganic foreign author books for odd electron species

texts: I need a foreign author book which explains odd electron species in great detail ,(explaining dimerization , energetic) telling hybridization of central atom with one unpaired electron on it pls tell me the book. I need to understand this topic and I don't have any idea of foreign author books pls


texts: What is the difference between crystal structures of proteins, organic and inorganic materials?

texts:
From the definition of crystal and the main differences between crystalline and amorphous material, it is known that crystal formation requires ordered bonding between atoms or molecules.

How can the protein with its irregular structure (when compared to organic and inorganic materials) make ordered bonding, since I often read about the crystal structure of the a protein and its ligand or inhibitor obtained by X-ray?

And is there any difference in crystal structure of an organic and inorganic material?


texts:
Why do simple molecular substances have weak intermolecular forces and why do giant covalent substances have strong intermolecular forces?

I understand that in simple molecular substances the atoms within a molecule are held together by strong covalent bonds, but the intermolecular forces between molecules are weak.

But I don't see what makes giant covalent substances have stronger intermolecular forces? What makes them stronger and have higher melting points?

I thought I understood but I think I must have gone wrong somewhere and now I am very confused. Help would be much appreciated. Also please explain simply, chemistry does not come naturally to me so I might get even more confused.


texts: Carbonyl chloride from stabilized chloroform treated with hydrogen peroxide

texts:
In our lab, chloroform contains 0.5–1% ethanol to prevent it from producing carbonyl chloride when exposed to UV light.

Will the following reaction occur using such chloroform?

$$\ce{CHCl3 + H2O2 -> HCl + H2O + COCl2 ^}$$


texts: How many resonating structures of Carbon Monoxide are there?

texts:
Anywhere I look, I get 3 resonating structures for CO molecule, like in this answer.
However, according to the rules stated for drawing resonating structures in this site, I wonder why there can't be this resonating structure as well?

Although it will be very unstable (due to lesser number of covalent bonds, positive charge on more electronegative atom), yet a minute contribution of this structure must in present in the resonance hybrid of the CO molecule. Then why is this structure not shown anywhere?


texts: Reference request for properties of amorphous titanium carbide (a-TiC)

texts:
I assume through some side reaction I'm getting $\ce{TiC}$ in my $\ce{TiO2}$ samples after calcination and I need some basic information about the properties of amorphous $\ce{TiC}$.

Is it paramagnetic or are there paramagnetic centers in the powder, i.e. $\ce{Ti (III)}$ species? What is the colour?


texts: Which are stronger intermolecular forces: ionic bonds or hydrogen bonds?

texts: Do strong ionically attracted molecules have stronger intermolecular forces than hydrogen bonding forces?


texts: Amines such as triaminomethane, tetraaminomethane, and many polysubstituted amines do not exist because of their degradation into ammonia.  Is it possible for derivatives of these amines to exist at all? Take for example tetra(t-butylamino)methane. Will there be enhanced stability due to the tert-butyl groups or will degradation to t-butylamine still occur?  Is there a point at which this degradation will stop, if so where?


texts:
Traditional Grignard reagents are made by reacting alkyl halide with Magnesium metal. However, the preparation and scope of their application have been limited because of low functional group tolerance.

Until recently, Knochel and coworkers have demonstrated the functional-group tolerance of magnesium-halogen exchange, which is now the method of choice for the preparation of highly functionalized organomagnesium reagents at low temperature as shown in the example

Turbo Grignard reagent ( isopropyl magnesium chloride) is used to change iodine or bromine with Magnesium.

what is reaction mechanism for exchange between iodine and magnesium?


texts: Does the shielding effect affect atomic bonding?

texts:
Electrons within an atom don't experience the full charge of the nucleus due to the shielding effect? Likewise, when creating atomic bonds, does the shielding effect affect the attraction between two bonding atoms?
Thanks for any help offered


texts: Write the combustion equation of an organic compound

texts:
Write the combustion equation of the organic compound $\ce{C5H10O}$

I have no idea at all how to write the equation. Should I add $\ce{O2}$ to make it $$\ce{C5H10O + O2 → ... ?}$$


texts: Is it the Na+ or the Cl- that gives table salt its taste?

texts: What gives it that salty taste? I'm wondering if it's the $\ce{Na+}$ or the $\ce{Cl-}$. I know that $\ce{KCl}$ also tastes salty, and other salts have different flavours,  but where does the saltiness in $\ce{NaCl}$ come from? I mean, it makes sense that it's the $\ce{Cl-}$ ion, but it could also be that $\ce{K+}$ and $\ce{Na+}$ have similar flavours.


texts: Synthetic Solution: How much nitric acid to add?

texts: I am making a synthetic solution to imitate a real life situation. I am adding calcium nitrate to the solution to meet a target calcium level of $\pu{334 ppm}$. However, using excel calculations the amount of calcium nitrate that is needed imparts a total of $\pu{522 ppm}$ calcium. I am also adding $\pu{100 ppm}$ calcium carbonate which will increase the levels of calcium. My supervisor said I need to add nitric acid to lower the calcium imparted by the calcium nitrate. How and why does that work? and what calculation do I need to do to figure out how much nitric acid I need to add?


texts: What products are formed when KMnO4 and KI react with each other in "weakly basic" medium?

texts:
While solving JEE Advanced 2020 (Paper 2) questions, I came across this particular question:

According to the final answer key, its answer is 6.
In my chemistry book (NCERT Chemistry), the following equation is given:
In neutral or faintly alkaline solutions:
$\ce{2MnO4- + H2O + I- -> 2MnO2 + 2OH- + IO3- ~~~~(1)}$
If I go by this equation, the answer should have been 0.
According to the same book,
In basic medium:  $\ce{MnO4- + I- -> MnO2 + I2 ~~~~~(2)}$
This gives the correct answer.
Is there a difference between "weakly basic" and "faintly alkaline"? What I can conclude from here is that the reaction in weakly basic medium is equivalent to that in basic medium, and not in faintly alkaline medium.
Could anyone please explain why the answer is 6 and confirm which equation is valid for the given case?

Side question:
I had learned that in basic medium, n-factor of $\ce{KMnO4}$ is 1 due to the following reaction:
$$\ce{MnO4- -> MnO4^2-}$$
This transition is not seen in the reaction (2). Could someone explain this?

**UPDATE:
After doing some analysis, I have been able to conclude the following:

Acidic medium:
$\ce{MnO4^- + I^- -> Mn^2+ + I2}$
Neutral / Faintly Alkaline medium:
$\ce{MnO4^- + I^- -> MnO2 + IO3^-}$
Basic (not alkaline - so that I2 is not oxidised to $\ce{IO3^-}$ due to presence of $\ce{OH^-}$ ions) / Weakly Basic medium:
$\ce{MnO4^- + I^- -> MnO2 + I2}$
Alkaline medium / Strongly Alkaline medium:
$\ce{MnO4^- + I^- -> MnO4^2- + IO3^-}$

Could anyone please confirm if the above equations are correct?**


texts:
The atomic radius of Sc is $\pu{162pm}$, Ti is $\pu{147pm}$, $\ce{Fe}$ is $\pu{126pm}$, and that of $\ce{Co}$ is $\pu{125pm}$.

The electronic configuration of $\ce{Fe}$ is $\ce{[Ar] 3d^6 4s^2}$, and that of $\ce{Co}$ is $\ce{[Ar] 3d^7 4s^2}$.  The difference in atomic number, and hence the difference in the number of 3d electrons, is 1. So, due to screening, the extra charge is "canceled" and they have nearly the same radii.

The difference in atomic number and 3d electron count between $\ce{Sc}$ and $\ce{Ti}$ is also the same — 1.

So, I want to know why there is a considerable difference between the radii of Sc and Ti but not between the radii of Fe and Co.


texts: Difference between torsion, out of plane, coplanar and perpendicular bends?

texts: In Infrared spectroscopy, stretches are easily understandable. But, how do I visualize (or conceptually understand) the difference between dihedral (torsions), out of plane bends, coplanar bends, and perpendicular bends? Can you give examples?


texts: Ratios and mass; reaction calculation problem

texts:
I have come across the following problem:

One method used to inflate air bags in cars is to use nitrogen produced chemically from the decomposition of sodium azide. The sodium formed reacts with potassium nitrate to give more nitrogen.
$$\ce{2NaN3(s) -> 2Na(s) + 3N2(g)}$$
$$\ce{10Na(s) + 2KNO3(s) -> K2O(s) + 5Na2O(s) + N2(g)}$$
a) In what ratio by mass must the sodium azide and potassium nitrate be mixed in order that no metallic sodium remains after the reaction?
b) Calculate the total mass of the solid mixture needed to inflate a $60.0\ \mathrm{dm^3}$ air bag at room temperature and atmospheric pressure.

I have a solution to part a), which is 1:0.311, but this differs from the given answer (1:3.11). Here is my solution:
For every 10 moles of $\ce{NaN3}$, 2 moles of $\ce{KNO3}$ is needed i.e. ratio in moles is 5:1. Mass of $5\ \mathrm{mol}$ of $\ce{NaN3}$ is $5 \times 65.0 = 325$ and mass of 1 mol of $\ce{KNO3}$ is 101.1. So, ratio = 325:101.1 = 1:0.311. Is this incorrect?
I also have a solution to part b), but again this differs from the given answer $(40.9\ \mathrm g)$. Here is my solution:
Using ideal gas law to find how many moles of $\ce{N2}$ needed to inflate air bag: $n=\frac{PV}{RT}=\frac{101000\times 0.06}{8.31\times293}=2.49\ \mathrm{mol}$ If the first equation is rewritten as $\ce{10NaN3(s) -> 10Na(s) + 15N2(g)}$, then there are $\frac{15}{16}\times2.49=2.33$ moles of $\ce{N2}$ from the decomposition of sodium azide, and $\frac{1}{16}\times2.19=0.156$ moles of $\ce{N2}$ from the second reaction. Using these values gives $101\ \mathrm g$ of $\ce{NaN3}$ and $31.5\ \mathrm g$ of $\ce{KNO3}$, which clearly does not give the answer. What's incorrect here?


texts: Is the electrophile in sulfonation of benzene SO3 or SO3H+?

texts:
What's the electrophile in sulfonation of benzene? Is it $\ce{SO3}$ or $\ce{SO3H+}$?

According to what my professor taught me, both $\ce{SO3}$ and $\ce{SO3H+}$ may be the electrophile involved - and mechanisms with both species can be successfully written.

I'm looking for some source(s) that confirms the existence of both electrophiles in sulfonation reaction of benzene.


texts: Does a difference in IR signal size from 'normal' provide information on amount of material?

texts: I have an IR spectrum that has signals for my expected product but also signals from what I believe to be some reactant (an alcohol). Typically, an O-H signal is pretty strong, but this O-H signal has an absorbance of only ~35%. Can I make a conclusion about the relative amount of reactant?


texts:
Just to explain this question in a better way just think about the Rutherford's experiment(the alpha particle bombarded on Gold foil) be conducted using a electron gun in place of the Alpha one.. So what will happen when electron is targeted on a gold foil?

Either the atom rather the electrons of Ag atom become excited and therefore emit some sort of waves(if yes,then what kind of waves?), or in return electrons are ejected from the atom along with some waves,  or it may be possible that the electron pass by the gold foil without any effect...


texts: After boiling water in an electric kettle, should I empty it?

texts:
(I'm reposting my question from Physics SE where it got closed for being off-topic, but chat tells me that it might be on topic here.)

In the office I'm working in, there's an electric kettle for boiling tea water.  Every day, I boil water in it.

At one point, my boss asked me to empty the kettle after making the tea, that is, pour the unused water remaining in the kettle into the sink so that the kettle is as dry as I can easily get it.  His rationale was that this will stop the kettle from getting chalk residue from the hard water.

I obey my boss, both because he owns the office and so the kettle is his, and because he's an engineer.  But privately, I have doubts about this request.

I know from practice at home that it is very easy to clean chalk residue from an electric kettle: you just boil water with citric acid in it, then rinse the kettle properly, and this removes all the residue.  (Vinegar also works instead of citric acid, I prefer citric acid because it doesn't have the smell and is also cheap.)

On the other hand, I'm worried that if I don't leave any water in the kettle after boiling water for tea, the heating element may still be hot and its surface could become oxidized.  If that happens, that's much more diffictult to fix than the chalk.  Because of this, at my home, I always make sure that there is water in the kettle after boiling, including adding cold water from the tap if I used up all the hot water.   I have very hard water at my home, which causes a lot of difficulties cleaning the bathroom tiles.  (I do not know how hard the water is at the office.)

So what's the best practice at home?  Should I leave the kettle dry or wet after boiling water?


texts: How could a scientist from the 1800s to the 1920s run spectroscopy of chemicals?

texts:
How would such a scientist be able to get the spectroscopy of chemicals?  Without access to modern computing or electronics how would it be possible?

Any video link or reference link are much appreciated here.


texts:
Ortho acids like orthoformic acid (methanetriol, $\ce{HC(OH)3}$), orthocarbonic acid ($\ce{C(OH)4}$), and orthoacetic acid (ethane-1,1,1-triol, $\ce{H3C\bond{-}C(OH)3}$) are known to be unstable and decompose spontaneously.

For example, orthoformic acid spontaneously decomposes into formic acid and water, while orthocarbonic acid spontaneously decomposes into carbonic acid and water. As a matter of fact, these two acids have never been isolated.

$$\ce{HC(OH)3 -> HCOOH + H2O}$$
$$\ce{C(OH)4 -> H2CO3 + H2O}$$

Interestingly enough, orthoesters are stable and can be isolated, unlike ortho acids, just that orthoesters are easily hydrolyzed, especially with a mild acid present. For instance, trimethyl orthoformate, the simplest orthoester, can be synthesized. Why is that ortho acids are very unstable, while orthoesters are stable? Is the presence of hydroxyl groups of ortho acids a direct contributor of their instability?


texts: Finding orbit radius using the Bohr model and Rydberg equation

texts:
To start with its a homework problem, quite lengthy.

  A particle of mass equal to 208 times the mass of an electron moves in a circular orbit around a nucleus of charge $+3e$. Assuming the Bohr model of the atom is applicable to this system,

  Derive an expression for radius of $n$th Bohr orbit.
  Find the value of $n$ for which the radius is equal to the radii of first orbit of hydrogen.
  Find the wavelength of radiation emitted when revolving particle jumps from third orbit to the first.

Now, I did the first part and got the answer correct. Here's what I did.

Suppose the mass of the particle revolving is $M$, its speed is $v$, and $M = 208 m_{e}$. Electrostatic force is the centripetal force. Therefore

$$
\begin{align}
\frac{Mv^2}{r} &= \frac{(ke)(3e)}{r^2} \\
v^2 &= \frac{3ke^2}{208m_{e}r}
\end{align}
$$

From the Bohr model,

$$
m_{e}vr=\frac{nh}{2\pi}
$$

where $h$ is Planck's constant. Therefore,

$$
v = \frac{nh}{2\pi m_{e}r}
$$

Squaring it,

$$
v^2 = \frac{n^2h^2}{4(\pi)^2(m_e)^2r^2}
$$

Equating the two equations which have $v^2$ in them,

$$
\frac{n^2h^2}{4(\pi)^2(m_e)^2r^2} = \frac{3ke^2}{208m_{e}r}
$$

After solving for $r$, we get something like this,

$$
r = \frac{n^2h^2}{4(\pi)^{2}3ke^{2}208m_e}
$$

All of the above is correct. The problem is in the second and third parts; when I put $r =\pu{0.53*10^{-10} m}$ I do NOT get the required answer. To approach the third part, I started with the standard Rydberg equation,

$$
\frac{1}{\lambda} = \mathcal{R}Z^2 \left( \frac{1}{n_f^2}-\frac{1}{n_i^2} \right)
$$

I plugged in each value, $n_i = 3, n_f = 1, Z = 3$; but again didn't get the answer correct.

  The answer to the second part is 25 $(n=25)$; and to the third is 55.2 picometers.


texts: What makes DNA/Protein in a gel run in straight lines?

texts:
In a gel electrophoresis, let's assume an SDS-PAGE, I understand that the sample is loaded on a cuboidal well and the electric field is straight downward. It is easy to assume that the sample is going to run straight in the gel. Like it does here.

But when I observed the apparatus in my lab, the anode was all throughout the base - looking something like this (cathode not shown here and the anode is insulated on the side - so effectively present at the base of the gel).

What makes the sample run in the gel only in a straight line? You may say that the forces cancel out on the either sides but what about the well that's at one end? It's being pulled downwards and also the other end.

So how does this work?


texts: Finding the density of nitrogen at 0 degrees Celsius and 1 atmosphere

texts:
The density of nitrogen at $\pu{0 ^\circ C}$ and $\pu{1 atm}$ is most nearly equal to which of the following quantities?
(a) $\pu{0.001 g/L}$; (b) $\pu{0.01 g/L}$; (c) $\pu{0.1 g/L}$;
(d) $\pu{1 g/L}$; (e) $\pu{10 g/L}$.

The answer is (d), $\pu{1 g L-1}$.
I think this is how you do it, but please correct me if I'm missing something. I didn't end up using the standard molar volume, so this might be incorrect.
$$pV = nRT$$
We know the pressure is $\pu{1 atm}$, the temperature is about $\pu{273 K}$ and $R = 0.08$.
Solving for $\frac {n}{V}$, we find $\frac {n}{V} = \frac {1}{22}$.  Now, this is in moles per litre, so by multiplying by the molar mass of nitrogen (approximately $\pu{28 g mol-1}$), we find that we have about $\pu{1 g}$ per litre as the density.


texts:
I am not able to understand the difference between Saytzeff's rule and beta elimination reaction. Also I am writing two reactions below:

\begin{align}
\ce{CH3-CH2-CH(Br)-CH3 + \underset{\text{(aqueous)}}{KOH} & -> CH3-CH2-CH(OH)-CH3} \tag{1} \\
\ce{CH3-CH2-CH(Br)-CH3 + \underset{\text{(alcoholic)}}{KOH} &-> \underset{\text{(major)}}{CH3-CH=CH-CH3} + \underset{\text{(minor)}}{CH3-CH-CH=CH2}} \tag{2}
\end{align}

Are they correct? If they are, then what are they called?


texts: How can copper(II) nitrate hexahydrate be synthesized in the laboratory as well as industrially?

texts:
I am researching the hexahydrate and found the same synthesis method being presented for both the anhydrous form and the trihydrate form.
Chemistry of the Elements Second Edition, N. N. Greenwood suggests that dissolving $\ce{Cu}$ into $\ce{N2O4}$ and ethyl acetate will give out the trihydrate by heating at $\pu{90 ^\circ C}$. $\ce{Cu(NO3)2*N2O4}$ is an intermediary product.

Syntheses and Physical Studies of Inorganic Compounds, C.F. Bell claims the same process to form the trihydrate.

And finally, the reaction I got from Ullmann is below:
$$\ce{Cu + N2O4  -> Cu(NO3)2* N2O4  -> Cu(NO3)2}$$

All of this just leaves me with more questions. How do I know if the final product has 3, 6 or no waters?
I would like to obtain the hexahydrate form so I need the proper conditions for this.
There is no mention anywhere of the industrial process or have I been looking in the wrong places? Ullmann just mentions dissolving $\ce{Cu}$, $\ce{CuO}$ and so on in $\ce{HNO3}$, but there is no elaboration on industrial tools and techniques to produce the hexahydrate specifically.


texts: Why would hexacyanidocobaltate(II) be uncommon while pentacyanidoaquacobaltate(II) is common?

texts: In Huheey's Inorganic Chemistry it is written that hexacyanidocobaltate(II) is uncommon but pentacyanidoaquacobaltate(II) is common. Something is mentioned about Jahn-Teller distortion, but I don't understand how it applies here.