texts: Will the sulfur-iodine cycle and Haber Method work at lower pressures and temperatures?

texts:
I have a year-long research project next year in my senior year of high school, in which we have to make some product or prototype to solve some issue.

My interest was in the Liquid Fluoride Thorium Reactor but considering that I do not have the access I need, I opted to invest in the heat it produces.

One use as proposed by Kirk Sorensen proposed using the heat from the reactor to fuel the sulfur-iodine cycle to split water into $\ce{H2}$ and $\ce{O2}$.  Then use those combined with carbon collected from the waste of coal and fossil fuel plants and nitrogen from the atmosphere to make methanol dimethyl-ether and ammonia.

My teacher and I have ruled out the first two, but decided that we might be able to make ammonia.  My question is whether it would be feasible and practical to use the sulfur-iodine cycle in combination with the Haber process to split water and make ammonia at a much lower temperature and pressure to ensure safety.


texts:
Why are we able to show structures of compounds with different position of electron, but with same position of them? Shouldn't the structure become unstable due to this?

Let's take benzene for the example of resonance.We know that in reality benzene has no pure single or double bond. How can this be possible?

The bond length for $\ce{C-C}$ and $\ce{C=C}$ bonds in benzene is same which is $1.39~\mathring{\mathrm{A}}$. This is due to partial single and double bond between carbon atom, which is due to resonance. Why is there a resonance? Why can't benzene be happy with three alternate single and double bond between each carbon atom?


texts: kinetic description of an autocatalytic system

texts:
I have previously asked this question at physics SE here and it was suggested to post it here.
I am looking at the system:
$2X + Y \Leftrightarrow 3X $
$A \rightarrow Y$
$X \rightarrow B$
The description in terms of differential equations is this:
$\frac{dx}{dt} = x^{2}y - x$
$\frac{dy}{dt} = a - x^{2}y$
What is puzzling me is that the fact that 3X are produced is not captured in these equations.
Why is the description not something like
$\frac{dx}{dt} = 3x^{2}y - x - x^{3}$ ?
What fundamental thing am I missing? Help is greatly appreciated.
The source for this is "mathematical models in biology (1987), p 357" by Leah Edelstein-Keshet.
(also, I have a hard time finding relevant tags for this, so please feel free to change)


texts: Diagonalization of Hessian H= PkP$^{-1}$: what do the elements of P matrix physically mean?

texts:
This is quoted from Computational Chemistry by Errol J. Lewars' chapter 2's Stationary Points & Normal-Mode
Vibrations: ZPE:

  \begin{align}\mathbf H &=\begin{bmatrix}
    \dfrac{\partial ^2 E}{\partial q_1 \partial q_1} & \dfrac{\partial ^2 E}{\partial q_1 \partial q_2} & \dfrac{\partial ^2 E}{\partial q_1 \partial q_3} & \dots  & \dfrac{\partial ^2 E}{\partial q_1 \partial q_9} \\
    \dfrac{\partial ^2 E}{\partial q_2 \partial q_1} & \dfrac{\partial ^2 E}{\partial q_2 \partial q_2} & \dfrac{\partial ^2 E}{\partial q_2 \partial q_3} & \dots  & \dfrac{\partial ^2 E}{\partial q_2 \partial q_9}\\
    \vdots & \vdots & \vdots & \ddots & \vdots \\
    \dfrac{\partial ^2 E}{\partial q_9 \partial q_1} & \dfrac{\partial ^2 E}{\partial q_9 \partial q_2} & \dfrac{\partial ^2 E}{\partial q_9 \partial q_3} & \dots  & \dfrac{\partial ^2 E}{\partial q_9 \partial q_9}
\end{bmatrix}\\ \\ &=\underset{\mathbf P}{\begin{bmatrix}
    q_{11} & q_{12} & q_{13} & \dots  & q_{19} \\
    q_{21} & q_{22} & q_{23} & \dots  & q_{29} \\
    \vdots & \vdots & \vdots & \ddots & \vdots \\
    q_{91} & q_{92} & q_{93} & \dots  & q_{99}
\end{bmatrix}} \underset{\mathbf k}{\begin{bmatrix}
    k_{1} & 0 & 0 & \dots  & 0 \\
    0 & k_{2} & 0 & \dots  & 0 \\
    \vdots & \vdots & \vdots & \ddots & \vdots \\
    0 & 0 & 0 & \dots  & k_{9}
\end{bmatrix}}\mathbf P^{-1}\end{align}

  The 9 × 9 Hessian for a tri-atomic molecule
  (three Cartesian coordinates for each atom) is decomposed by diagonalization into a P
  matrix whose columns are “direction vectors” for the vibrations whose force constants
  are given by the $\bf k$ matrix. Actually, columns 1, 2 and 3 of $\bf P$ and the corresponding $k_1,k_2,k_3$ of $\bf k$ refer to translational motion of the molecule (motion of the whole
  molecule from one place to another in space); these three “force constants” are nearly
  zero. Columns 4, 5 and 6 of $\bf P$ and the corresponding $k_4,k_5,k_6$ of $\bf k$ refer to
  rotational motion about the three principal axes of rotation, and are also nearly zero.
  Columns 7, 8 and 9 of $\bf P$ and the corresponding $k_7,k_8,k_9$ of $\bf k$ are the direction
  vectors and force constants, respectively, for the normal-mode vibrations: and
  refer to vibrational modes 1, 2 and 3, while the 7th, 8th, and 9th columns of $\bf P$ are
  composed of the x, y and z components of vectors for motion of the three atoms in mode
  1 (column 7), mode 2 (column 8), and mode 3 (column 9).

I couldn't conceive what actually $\bf P$ implies; it is, of course, the eigenvector matrix of the Hessian $\bf H $ but what does it represent?

Lewars wrote that columns of $\bf P$ are actually direction vectors; now what did he mean by direction vector?

I thought $q$ represents the geometric coordinate; I got $k$ is the force-constant; but what are those series of $q$ s in $\mathbf P\;?$

Are the $q$ s in $\bf P$ coordinates of the atoms in molecules? If so, aren't they always changing since they are vibrating, rotating...?

Can anyone please explain this to me what those $q$ s actually represent? What did Lewars want to mean by direction vectors?


texts: Does ammonium react with water in an ammonia solution?

texts:
In the following equilibrium:

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

Is it possible for the ammonium to simultaneously establish another reaction with water?

$$\ce{NH4+ + H2O <=> NH3 + H3O+}$$

If so, we would enter a cycle where the additional concentration of ammonia resulting from the second reaction would, in turn, shift the first equilibrium to the right according to Le Châtelier's principle. I surmise that this system will eventually stabilize yielding hydroxide ions (with a negligible concentration of hydronium ions), hence the basic character of ammonia. Are these valid conclusions? Thanks in advance.


texts: Classification of the Inside of a Grapefruit

texts: In the text Chemistry: The Central Science, the inside of a grapefruit is classified as a homogeneous mixture. Unless I’m missing something, to me it would be a heterogenous mixture owing to pulp, seeds, and ultimately the fact that cells are not homogenous. Is this a mistake in the text, and, if not, what am I missing?


texts: How do you explain the thread sticking to an ice-cube when salt is sprinkled over it?

texts:
So this experiment goes like this :

You take an ice-cube
You put a thread on top face of it
You sprinkle some common salt on the ice-cube wherever its touching the thread
You wait for sometime (approx 1 min)
Voila! now you can lift the thread and ice-cube will stick to the end of the thread so you can lift the whole thing altogether

How do you explain this in chemistry?


texts: When does nucleophilic attack and proton transfer happen?

texts:
from the reaction, the 3rd molecule (carboxylic acid) formed undergo neutralization with OH- (proton transfer to a base).

However, is it possible for the 3rd molecule to behave as the 1st molecule (ester) and undergo nucleophilic attack by the OH- as they both have an electrophilic centre (carbon)?

If yes, will this reaction form a cycle (never forms carboxylic salt). If no, may I ask why? Is it related to stability or other effects? Thank you very much


texts: Wavelength of iPhone 4S camera light for visible spectroscopy calibration

texts:
I ordered a DIY spectroscopy kit from public-lab, however don't have access to a halogen lamp to calibrate the wavelengths.

I'm wondering if it would somehow be possible to calibrate the wavelength using the iPhone camera light?


texts: Reason for different chemical shift in chiral solvents for enantiotopic protons

texts:
The chemical shift of enantiotopic protons is defined as follows in Spectroscopy/Homotopic, Enantiotopic, Diastereotopic

Enantiotopic protons have the same chemical shift in the vast majority of situations. However, if they are placed in a chiral environment (e.g. a chiral solvent) they will have different chemical shifts.

The second sentence in this question piques my interest. Even after some searching, I only saw this same sentence over and over again.
What makes the chiral solvent cause a change in magnetic environment causing the change in chemical shift for enantiotopic protons?


texts: Were gold(II) complexes synthesized for the first time in 2017?

texts:
Recently in the Google news feed, I discovered this news:

  Gold stabilized in very rare oxidation state +II

  Missing golden link found: Divalent gold complex isolated for the
  first time in a pure form; new fundamental insight also provides
  possible explanation of the mechanism of action of cytostatic
  gold(+III) porphyrins

  Date: August 8, 2017

  Source: Johannes Gutenberg Universitaet Mainz

  Summary: A team of chemists has been able to isolate and analyze gold
  in the very rare oxidation state +II. This provides the missing links
  in the homologous series of the coinage metal ions copper(+II),
  silver(+II), gold(+II), and in the 'relativistic' triad of
  platinum(+II), gold(+II), and mercury(+II).

And there are loads of similar news- Here, here and here.

Now, I started digging for more information and found out that gold(II) complexes were known previously and has been synthesized but they are unstable and prone to disproportionation.

  Coordination chemistry of gold(II) complexes (October 1999)

  The number of complexes with gold in a formal oxidation state of
  two have increased considerably and nowadays this oxidation state can
  be considered nearly as a common state in gold chemistry. This
  review covers the evolution of the knowledge of this oxidation state
  from the first dithiocarbamate derivatives $\ce{[Au2(S2CNR2)2X2]}$,
  stable only at very low temperature, to the room temperature stable
  dinuclear gold complexes $\ce{[Au2(L–L)2X2](L–L=CH2PPh2CH2, CH2PPh2S,
 C5H4PPh2-2; X=halogen}$). Although a dinuclear structure with a
  gold(II)–gold(II) bond supported by two equal bridging ligands were
  the first and most common, this review shows the present diversity as
  mononuclear, $\ce{[Au([9]aneS3)2](BF4)2}$, dinuclear with two
  different bridging ligands, $\ce{[Au2(S2CNR2)(CH2PPh2CH2)X2]}$, with a
  non-supported metal–metal bond, $\ce{[Au2(Ph2PC8H6PPh2)2Cl2](PF6)2}$,
  and polynuclear gold(II) complexes either with chains of only gold
  centers or with other metals, such as
  $\ce{[{(C6F3H2)Au(CH2PPh2CH2)2Au}2Au2(CH2PPh2CH2)2]ClO4}$ or
  $\ce{[Au2Pt(CH2PPh2S)4X2]}$
  Disproportionation of Gold(II) Complexes. A Density Functional Study of Ligand and Solvent Effects (July 13 2006)

  For the disproportionation of $\ce{Au(II)L3}$ complexes with neutral
  ligands, disproportionation is highly endergonic in the gas phase.
  Calculations imply that for synthesis of a monometallic $\ce{Au(II)}$
  complex, a nonpolar solvent is preferred. With the exception of
  $\ce{[Au(CO)3]^2+}$, disproportionation of $\ce{Au(II)L3}$ complexes
  to $\ce{Au(I)L}$ and $\ce{Au(III)L3}$ is exergonic in solution phase
  for the ligands investigated.
  Structural Studies of Gold(I, II, and III) Compounds with Pentafluorophenyl and Tetrahydrothiophene Ligands(February 28
  2007)

  A golden opportunity was seized to prepare an unbridged, dinucleur
  gold(II) compound, $\ce{[Au2(C6F5)4(tht)2]}$
  (tht=tetrahydrothiophene), without any stabilizing chelating ligands
  (see picture; Au orange, S yellow, F green, C black) and to
  crystallographically characterize the gold(I) and gold(III) complexes
  participating in this conversion. A unique ligand scrambling of the
  latter gold(III) compound occurs in solution.

Gold(II) complexes has been intensly studied previously. They have been trying to synthesize a stable complex but failed miserably. The stable ones are only present in low temperature and only one was found to be stable in room temperature. So, although gold(II) complexes were previously discovered and (synthesized?), why scientists at University of Mainz and those who discovered it in 2017 claims to have synthesized gold(II) complexes for the first time?


texts: Synthetic options for selective hydroxylation at terminal position

texts: Are there any synthetic options to add a hydroxyl group at the terminal position to the bicyclo compound below? What might be reactions worth trying, any idea? Or is this a lost cause?


texts:
It is a well-known fact that

Water kept in a container, on cooling, results in freezing with initially at the circumference of surface
(1D), then on the surface (2D) and then throughout the volume (3D).

Why does it happen that way?
My attempt:
I thought that this may be due to their exposure levels.The outer surface is more exposed to cooling than the inner ones and hence cools first.However, I am not satisfied with this explanation.
I think there is some relation between this and degrees of freedom.I feel as there are more degrees of freedom in 3-D, there's more movement you should suppress to lower its energy, so maybe they freeze slower.
Is the above reasoning correct? I would also like to know different ways to reason out this.


texts: Reaction of Hydrogen and Dinitrogen Tetroxide?

texts: What might be the possible products of a reaction between hydrogen and dinitrogen tetroxide ($\ce{N2O4}$)? They are fuel and oxidizer respectively in rockets.


texts: What is the difference between cofactors and coenzymes?

texts: I've just been wondering what are the differences between the two and I can't seem to find a formal delineation.


texts: Ripping apart plastic: is this a chemical or physical change?

texts:
I was holding a piece of plastic earlier, and I ripped it in half. This caused me to start to think about what was happening at the atomic level. If the plastic is being ripped, clearly bonds are being broken and new bonds are being formed, so is this not a chemical reaction?

I realize that the plastic retains all of its chemical characteristics despite it being ripped, so I am quite confused about how to classify what is occurring.


texts: What has been the accepted value for the Avogadro constant in the "CRC Handbook of Chemistry and Physics" over the years?

texts:
Some questions about the constant made me curious as to exactly how much the accepted value has changed over the years. I am pretty sure that I learned a rounded value of $6.023\times10^{23}$ about 1970 which would have been around the 50th edition. I know that sometime after that the accepted value rounded to 4 significant figures was $6.022\times10^{23}$. Of course since 2019 the accepted value has been fixed at exactly $6.02214076\times10^{23}$
It would seem that the CRC handbook is a reasonable source for the accepted value of the constant since it has been updated almost yearly.
Please update the table in the answer in the community wiki page with other values


texts: Why isn't this resonance possible in an imidazole ring?

texts: My question is why isn't the resonance structure drawn in pencil on the right a valid one? My review book states that after initial protonation on the indicated nitrogen no resonance is possible.


texts: How to know if a sample suffered descomposition during melting point?

texts: If I take a sample in order to determine its melting point, how do I know if that sample suffered a descomposition?


texts: What chemicals are in tap water that gives it a slightly basic pH level

texts: In chemistry, we recently did a lab where we observed the different ways of reading pH of several different substances. We used things such as red cabbage juice, litmus paper, pH paper and a pH probe. One of the substances we tested was water. When we used the pH probe, it came back with a reading around 8.0. When we tested the distilled water, it came back with a reading very close to 7.0. So what is different between distilled and tap water that causes the tap water to be basic?


texts: How do hard drives store information using magnetic layering? (Antiferromagnetic/ferromagnetic films)

texts:
I am doing some work with solid state materials in some chemistry courses and I've been doing some research into exactly how a hard drive stores information as 1's and 0's. It seems like a bunch of people know how it functions as an overview but the physics of what's going on is less well known.

So far I can confidently say that a hard drive is composed of many tiny thin films within the sectors on the platter. The film is divided into (at least) two layers. The top layer is the "pinning" layer which is an antiferromagnetic. The bottom layer is a ferromagnetic layer or in some cases a ferrimagnetic layer. The top layer contains magnetic domains which are anti-parallel and therefore contains no overall magnetic moment. The bottom layer being ferromagnetic has all of its magnetic domains aligned with each other, creating a net magnetic moment across the film.

I understand that in order to achieve a 1 or a 0, the magnetic moment of the underlying ferromagnetic layer undergoes a net magnetic moment flip, which is can be read. The pinning layer helps to keep it as a 1 or a 0 by not allowing this moment flip without considerable application of an external force. This force is termed the exchange energy of the film. This however is where I can't figure things out.

How does the "pinning" layer exert any force on the underlying ferromagnetic layer if it has no net magnetic moment? And more importantly how does this exchange energy manifest itself in a "snappy" transition between the 1 and 0 state of the ferromagnetic layer?

Please let me know if there is any more info that I can provide in order to help clarify, I am super interested in the answer to this question and would love to do some more research to figure it out if I can only get pointed in the right direction.


texts:
I found a term on this website that gives a unit of [A*m^2/mol]. The equation is:

$k_d^{eff}=\frac{2RT\kappa^{eff}}{F}(t^+-1)\left(1+\frac{\text{d}\ln(f)}{\text{d}\ln(c)}\right)$

where R is the gas constant [J/mol/K], K is ionic conductivity [S/m], T is the temperature [K], t+ is unitless, f is unitless and c is the concentration [mol/m^3], F is the Faraday constant [C/mol].

This equation gives the unit $\frac{A \cdot m^2}{mol}$. What kind of unit is this one? I can see that they define it as electrolyte diffusional conductivity, but I can't find this unit and better definition anywhere in the literature.

Can anyone help me with this?


texts: Why can't diamagnetic, and paramagnetic magnetize?

texts: Ferromagnetic materials can be made into permanent magnets.  How come diamagnetic, and paramagnetic materials be made into magents?  Does it have to do with the valence electrons, and how they are arranged, and their spin?


texts:
I keep reading that solutions are electrically neutral, but I've never read an explanation. I've read after the fact justifications, such as one problem which asked me to calculate the force of repulsion between two beakers with a tiny, tiny bit of excess charge (it ended up being over 10,000 pounds).

So why are solutions electrically neutral? Not interested in after the fact explanations like the above example.


texts: What is the correct Lewis structure of NH3O?

texts:
Choose the most appropriate Lewis structure for $\ce{NH3O}$ among the two:
 and

The oxygen in the second case has 3 nonbonding pairs around it.
I chose the first as an answer, yet the second seems to be the correct one. Can anyone please explain why?


texts: Should binding constants be unitless when deriving fractional occupancy equations from reactions?

texts:
It is known that binding (aka association) constants are in fact unitless, as has been discussed here already. However, I'm not a chemist and am confused about when one should or should not use units when working with association constants. One source says:

  $K_\text{eq}$ for a reaction with unequal numbers of reactants and products is always given with units, even in published papers.

But why is that? Why not always use unitless values? Is there something inherently wrong with never using units for binding constants?

Consider this example. Let $\ce{A}$ bind to $\ce{X}$ as an n-mer (e.g. $\ce{A}$ can be a transcriptional activator binding to gene promoter). This results in active state, $\ce{X_{A}}$ (e.g. a state leading to gene transcription):

$$\ce{X + nA ->[k_{\text{on}}][k_{\text{off}}] X_{A}}$$

Association constant: $K_\text{A} = \frac{k_\text{on}}{k_\text{off}} $

Assuming equilibrium and law of mass action:

$$K_\text{A} \cdot \text{X} \cdot \mathrm{A^n} = \mathrm{X_A}$$

Now, the fractional occupancy (active states to all states ratio) is:

$$y=\mathrm{\frac{X_A}{X+X_A}} = \frac{K_\text{A}\cdot \mathrm{A^n}}{1 + K_\text{A}\cdot \mathrm{A^n}}$$

As $y$ must be unitless (i.e. it can be interpreted as a probability), for this particular equation, $K_\text{A}$ must have units of $\mathrm{M^{-n}}$ (in general, $\text{concentration}^{-n}$) for the equation to work out, correct (assuming concentration of $\ce{A}$ has units $\mathrm{M}$)? So in this particular case, using unitless $K_\text{A}$ seems wrong, but is it really, or is there something I'm missing?

Now let's extend this equation so that it includes a half-saturation constant $h$, i.e. concentration of $\ce{A}$ required for $y=0.5$ (50% activation). If I'm doing this correctly, we get:

$$y=\frac{K_\text{A}\cdot \mathrm{A^n}}{K_\text{A}\cdot h^n + K_\text{A}\cdot \mathrm{A^n}} = \frac{\mathrm{A^n}}{h^n + \mathrm{A^n}}$$

Note that this is equivalent to the Hill equation for an activator. This generalized equation, unlike the previous one, works just fine regardless of whether or not $K_\text{A}$ is unitless.

Is my understanding of this correct, and does the choice of unitless vs non-unitless binding constant indeed depend on the formulation of a specific equation?


texts: Does Beta-ionone posses the same anti-ageing properties as Retinoids if applied topically to the skin?

texts:
I read a scholarly article on oxidisation and collagen structure in the dermis and they mentioned the use of Retinoids topically. so I looked into retinoids (admittedly on Wikipedia) for an overview (Vitamin A and Retinoic acid, retinol etc) in the possible use on anti-ageing, which happened to state that carotenes are apparently "metabolized to β-ionone, and thus have vitamin A activity because they can be converted by plant-eating animals to retinol and retinal. Carotenoids that do not contain the β-ionone moiety cannot be converted to retinol, and thus have no vitamin A activity."

I cannot find anywhere by googling this, and as I am an amateur perfumer, not a chemist, with a genuine curiosity for an innocuous bottle of Beta Ionone that I use for fragrancing. I would be really grateful if someone could point out in layman's terms what is meant by "vitamin A activity" and could explain-

If using Beta Ionone on the skin it can possess the same qualities of the retinoids that are sold as anti-ageing products?

P.S I realise that beta-ionone is a possible cause for irritation on skin in certain amounts so this is not the question of safe amounts, it is the reaction in terms of the aforementioned that I am interested in.


texts: Lowering of the freezing point on adding a solute is a colligative property of solutions, it doesn't matter what the nature of the solute is (of course we have to assume ideal solutions). So when it is required to use an antifreeze - why are glycerol, glycol, methanol, etc. commonly used? For a given decrease in freezing point, a given value of molality is required - in other words a particular number of moles for the liquid's given mass. For the same number of moles, it should be simply more economical to use any substance with lower molar mass. Solubility in the solvent will obviously play a role - but there are many more solutes which are more soluble than alcohols. Why isn't $\ce{NaCl}$ used, for instance? Its molecular mass is not very high, and it is soluble to an appreciable degree. It's also more economical (moreover it will dissociate in water and generate twice the number of moles, so twice the decrease in boiling point).


texts: Reaction mechanism of combustion of hydrogen

texts:
After a discussion about the usefulness of hydrogen fuel for cars with a friend of mine, I wondered what the reaction mechanism for combustion of $\ce{H2}$ was. I only study (well almost) organic chemistry, so I have no idea if the mechanisms from organic chemistry can be applied at all to non-organic molecules.

So we have the following reaction:

$$2\ce{H2 + O2 -> 2 H2O}$$

In most textbooks this would be described as a redox-reaction with the two half reactions:

$$2\ce{H+ + 2 e- -> H2}$$
$$\ce{O2 + 4 H+ + 4 e- -> 2 H2O}$$

But I wonder what the real mechanism is. Based on my organic thinking I thought the following (it's probably completely wrong, but I think it is important to state because someone can correct me much better if I express my thinking than if he has no idea where the misconception started):

If the temperature is high enough a long pair of oxygen could break the $\ce{H-H}$ (the lone pair will be donated to the $\sigma^{*}$ bond) bond and form $\ce{2 H-}$ (each H gets one electron because of their equal electronegativity). $\ce{H-}$ is very unstable and one will immediately react with the empty oxygen orbital, the other will break the $\ce{O=O}$ $\pi$ bond. The electrons in the $\pi$ bond will go to the positively charged oxygen atom (the one that donated its electrons in the first step). Now one oxygen atom is neutral and the other has a positive charge (because the electrons of the $\pi$ bond went for the other oxygen), where the $\ce{H-}$ will attack forming hydrogen peroxide ($\ce{HO-OH}$). The previous process will now repeat, but instead, the $\sigma$ bond between the oxygen atoms will be broken, resulting in two water molecules, $\ce{2 H2O}$.


texts: Why won't increasing the temperature increase the solubility of a gas in a liquid solvent?

texts:
If I raise the temperature of a solution of a gas in a liquid solvent, why won't the solubility increase?

Increasing the pressure will increase the solubility, but increasing the pressure doesn't mean increasing the temperature?  What is wrong with this argument?


texts:
I think that the ginger ale is born this way.
Anyway, if you put the ginger in a glass and add sparkling water, small drops splash out of the glass, the water is fizzier, more effervescent.
Why? what makes the two of them react?


texts:
I've heard the commercials for this stuff for years, but what exactly does it do?  Does it do what the commercials say it does (clean out deposits in your tank)?  How well?

In other words, is this just an advertising campaign making a huge deal out of nothing, or is there actually an advantage to Chevron fuel?


texts: How to determine if a mixing process is spontaneous at constant temperature but variable pressure

texts:
This is a conceptual question.
Many times we work with the gibbs energy of mixing under conditions of constant temperature but not pressure.
In a problem like this:

  Suppose that 2.0 mol H2 at 2.0 atm and 25 ∘C and 4.0 mol N2 at 3.0 atm and 25 ∘C are mixed at constant volume. Calculate ΔmixG.

Is easy to calculate that the Gibbs mixing energy is -9,7 kJ.
But we also know that we cannot use gibbs' spontaneity criterion because it only works on constant pressure and temperature.

Is there any way to determine the entropy of the universe in this case to establish a criterion of spontaneity?
*For example if we know that the total volume is 10L and the division is even.


texts: What kind of drugs can be absorbed through skin?

texts: Some drugs such as nicotine can be administered through skin. I thought the layers of skin are designed to prevent in-flow of any chemical/germs. Not all drugs get absorbed in this fashion. So do drugs like nicotine have any specialities(such as a special chemical group) that fool the barriers of skin? A link to an article/site would be very helpful, or even a book recommendation.


texts:
I realize Chemistry Stack Exchange is not for homework and this will seem incredibly simple to many of you, but I have received no help elsewhere. I would really appreciate any support:

Limonene is obtained in the oil of lemon feel and it is the only alkene present.

$\pu{0.500 g}$ of the oil reacted with exactly $\pu{30.6 cm3}$ of a solution of bromine dissolved in cyclohexane with a concentration of $\pu{0.200 mol dm-1}$.
Calculate the percentage by mass of limonene in the oil.
Give your answer to an appropriate number of significant figures.
Assume that there is nothing else in the oil that react with bromine.

What I have done:
I tried working out the moles of $\ce{Br2}$ from these data (using the concentration and volume) and got $\pu{0.00612 mol}$. Assuming $\ce{Br2}$ is in the same ratio as limonene the moles will also be $\pu{0.00612 mol}$. However, this gives yield of $\pu{0.832 g}$ for limonene, which surely can’t be possible given the starting mass. Have I miscalculated the moles of bromine because it is dissolved in cyclohexane? Is there anything I am missing?


texts: I have a small question concerning the stirring bars cleaning. I use mine in BOD test wastewater for 5 days and I want to clean them so my question is can I soak them overnight with sodium hypochlorite (Javel) or it can affect their magnetic ability or something?


texts: Low-cost nontoxic corrosion inhibitor for steel exposed to hydrochloric acid

texts:
It seems that many commercial descaling solutions designed to remove scale (calcium carbonates, etc that form on water heaters) are a simple combination of an acid and an acid corrosion inhibitor for metals.

The acid renders the scale soluble in water, while (some) inhibitors coat metal surfaces preventing the acid from corroding the metal.

The problem is that these descaling solutions, despite their simplicity, are often \$30-\$100 per gallon (at just 5% HCl concentration!). Furthermore, most corrosion inhibitors are toxic.

A smart cost-sensitive consumer would obtain hydrochloric acid at a low cost (\$10 for 1 gallon of 35% HCl), and obtain or make a non-toxic, low-cost corrosion inhibitor.

Is there a non-toxic, low-cost, and reasonably well-established corrosion inhibitor that can be reliably obtained by a consumer for use as a descaling agent in combination with HCl?


texts:
Why is the electronegativity of indium greater than that of thallium?

One possibility which I had assumed was the poor shielding effect by the d and f orbitals which leads to an increase in the effective nuclear charge and hence the anomaly in the 13th group. But with thallium having a f orbital (which indium doesn't) which has a much poorer shielding ability than 'd', why does indium have more electronegativity?


texts: Mechanism of reduction by elemental sodium

texts:
How exactly does sodium form an alkoxide from an alcohol? I understand the general idea - sodium has a low first ionization energy. Sodium can thus give up its electron to something that'll take it. Sodium can therefore somehow cause hydrogen gas to leave.

How exactly does this mechanism work? I'm imagining that because alcohols are weak acids, that some hydrated protons exist in solution, and that sodium can donate an electron to these hydrated protons, which then can pair up with each other and form hydrogen gas. Is this accurate?


texts: In the beginning of the earth, there was at a certain point so much $\ce{CO2}$ in the air that most of it was absorbed by rock. The consequence of that was the snowball earth, because the atmosphere was empty; all the heat of the earth couldn't be more absorbed by $\ce{CO2}$, so it was getting cold. But how can rock ($\ce{SiO2}$?) absorb $\ce{CO2}$?


texts:
Determine the solubility of $\ce{N2}$ in water exposed to air at $\pu{25^\circ C}$, if the atmospheric pressure is $\pu{1.2 atm}$, assume that the mole fraction of nitrogen is $0.78$ in air and the Henry's Law constant for nitrogen in water at this temperature is $\pu{6.1 \times 10^{-4} M/atm}$.

I have the answer, but i want to know how to solve for it. I've been reading through my notes and the book trying to find a reference through which to approach this problem and i have found none. If anyone can guide me in the right direction that would suffice.


texts: Titrating iodine starch solution with sodium thiosulphate - Colour change

texts:
I investigated two mixtures with different solvents, one with water and one with n-heptane. Both contained iodine $\ce{I2}$ as a solute. To both solutions I added a bit of starch.

As I remember this resulted in a colourchange. So the solution turned from yellowish to dark blue (if I remember correctly!).

Now according to wikipedia starch and iodine indeed form a structure which has a dark blue colour. But it only forms in the presence of $\ce{I^-}$.

This leaves me wondering, why do I remeber the solution to be dark blue, eventhough I think there was no $\ce{I^-}$ present? Could it be the solution turned dark blue only after I added some sodium thiosulfate? Because in the next step I did a titration with $\ce{Na2S2O3}$.

In this case I don't see which reaction could have produced the $\ce{I^-}$ though. I thought only $\ce{NaI}$ is produced after adding the sodium thiosulfate.

$$\ce{I_2 + 2Na_2S_2O_3 -> 2NaI + Na_2S_4O_6} \tag{1}$$

So at which point did the solution turn dark blue and where did the $\ce{I^-}$ come from, that was needed for the formation of the starch-iodine-compound? Could it be there is an intermediate step to (1) in which $\ce{I^-}$ is formed and this $\ce{I^-}$ was used to produce the dark blue starch-iodine compound?


texts: How does an ice bath change the rate of an reaction?

texts:
If I had hydrogen peroxide decompose with the help of manganese dioxide and measured the time taken for the reaction to complete and the volume of oxygen collected. I will get a graph that looks like this:

Now what will happen to the shape of the graph if I placed the reaction vessel in ice?

I thought the following. The graph will rise but at a less rate and less steep than in the graph above. Then it will get to the point where the reaction ceases and doesn't go to completion because there are no more collisions.


texts:
Would trans hydride ligands on a metal complex be beneficial for a catalyst?
Such as alkene metathesis or hydrodefluorination


texts: Is sodium chloride really odourless? If yes, what do I smell?

texts:
I just had to read some general descriptions of sodium chloride and it was always classified as odourless (e.g., by Wikipedia). However, large amounts of table salts (around 1 kg) have a clearly perceptible odour to me. By table salt I mean salt sold for the purpose of cooking – I have not been taking notes or making experiments, but as I had the experience on dozens of different occasions, I would guess that the salt does not need to be iodised.

If I had to describe the smell, I would first say salty. It’s somewhat similar to the smell of the seaside, but the latter is much richer and has additional components. From the ten smell categories proposed here, only sweet and chemical fit somehow. It also has something of petrichor.

Is the classification as odourless just an approximation or do I smell additional ingredients (such as iodide) or impurities that cause table salt not to be pure sodium chloride? In the latter case: What causes the odour?


texts:
I came across an example today while I was studying tautomerism.

It is an example of tautomerism exhibited by acetylactone/1,3-diketone; given under the keto-enol systems under 1-3 migration/triad systems. (G.R.B. Organic Chemistry - O.P. Tandon 4.7.2(i) pg.122)

Soon I wondered - Why out of all the possible enols only this particular one - as shown in the example,
is the most stable form? ( 76% of the total content is only that particular enol, while the total enol content is 80.4%
testifies that it is much stable than the other possible enols)
As per my knowledge, the stability of enol increases in structures exhibiting:

Aromaticity
Intramolecular Hydrogen Bonding
Conjugation
Hyperconjugation

Where, Aromaticity stabilizes the most and hyperconjugation relatively the least with others in between just as they are arranged. (although I am not sure about it because it was just mentioned by my Chemistry teacher and I could not find sources mentioning it in such a hierarchy - so any edit suggestion in the hierarchy is welcome)
I drew all enol structures possible by 1,3-hydrogen migration:

Legend for the workings - 3C,5C,6C represent the number of atoms involved in conjugation while the numbers with alpha after them represent the number of alpha hydrogen present to stabilize a double bond.
(Here it is without any workings/markups)

Now, I'll be stating my assumptions about the stability of each of the 5 structures that I've drawn as per my knowledge.

Has conjugation extending only to 3 atoms & only 2 alpha hydrogens for hyperconjugation.
Has conjugation extending only to 5 atoms & only 3 alpha hydrogens for hyperconjugation.
Has conjugation extending only to 6 atoms & only 4 alpha hydrogens for hyperconjugation.
Consecutive double bonds are often unstable so I decided not to bother about this, anyway it is least conjugated although has 6 alpha hydrogen hyperconjugation shared by two double bonds.
6 atom bad conjugation since it is not spread throughout the chain & 2 alpha hydrogens.

So with all this, I concluded that option 3 is more stable but the book and the teacher said it is option 2.
I asked this question to my teacher about why option 3 cannot be counted in to which I got a rather unconvincing answer - the double bond is usually stable if it is placed more towards the center of a chain. Double bonds at the ends are usually unstable.
Having already accounted for hyperconjugation this is such an unconvincing answer!
It would be really helpful if someones can tell me the hierarchy of various stabilizing factors that make the enol more stable and how to determine which structure is more stable.


texts:
We just had chemistry practical few days a go. The topic was strong acid-base titration, in which we had to find the normality and concentration of $\ce{HCl}$.

My teacher instructed me to add 2 drops of Phenolphthalein  in 10 ml $\ce{HCl}$, and then add $\ce{NaOH}$ from buret and take a reading.

We needed to repeat the process 4 times and then find the constant reading, but in that I never used to take 2 drops of Phenolphthalein, instead I used to take 5-6 drops and then also used to get almost same reading as of pilot reading.

So my question is whether it is compulsory to take 2 drops of Phenolphthalein or it was just a instruction so students don't waste it?

In this same instruction given. (Procedure point 2)


texts:
1) What could be the most plausible explanation to the very low percentage of the nitro group attacking the site between bromine and chlorine?
- is it solely because of steric hinderence
- or is it because of the inefficient pi-electron overlaps by the larger chlorine and bromine atoms suppressing resonance in the region between them
- or is it inductive effect

2) why is the first product (given above) more formed than the second. Is it because of the more electronegativity of Cl over Br which could lessen the stability of compound 2 by negative induction effect( which destabilised nitro group which itself is electron withdrawing).


texts: What is the mechanism for this Horner-Wadsworth-Emmons (HWE) reaction?

texts: In this reaction the HWE reaction does not give a "normal" alkene product, but instead gives (R/S)-2. Provide a reasonable mechanism for its formation?


texts: Converting fractional coordinates into cartesian coordinates for crystallography

texts: So let's say for a given molecule I have the volume of a unit cell, the shape of the unit cell (monoclinic, cubic, etc), the cell angles alpha, beta, and gamma, the cell lengths a,b, and c, and a list of atoms with their corresponding fractional units. How do I convert these fractional coordinates of the atoms into cartesian coordinates for any given cell shape? Orthogonal or not?


texts: What kind of metal alloys can resist corrosion from molten salt?

texts: Molten salt is pretty hot, 801 C. With such heat and the corrosive nature of salt, I am wondering what type of metal alloy or other material hybrid would be appropriate to handle and work with molten salt?


texts:
I have no background in chemistry whatsoever. However, I'm very interested in sidewalk chalk composition. I read that chalk can be both either made out of gypsum or chalk (calcium carbonate). However, I'm confused, since a person that it is connected to a chalk (final product) manufacturer told me that the main ingredient in their product (chalk for kids) is sulfuric acid carbon.

As I said, my knowledge in chemistry is very reduced. I was just hoping that someone that knows well the subject can say if there can be a connection between the sulfuric acid carbon and gypsum.


texts: Magnetic moment of trivalent lanthanide cations

texts:
The effective magnetic moment $\mu_{\mathrm{eff}}$ of tripositive rare earth elements, is calculated by $$\mu_{\mathrm{eff}}=g_J\sqrt{J(J+1)}\mu_\mathrm{B}$$

Why can't we use normal formula as $\sqrt{n(n+2)}\mu_\mathrm{B}$ for them? I calculated $\mu_{\mathrm{eff}}$ for $\ce{Ce^3+}$ ion and got $2.54\mu_\mathrm{B}$ using first formula and $2.83\mu_\mathrm{B}$ using second one, there's a significant difference in two. How is the first formula derived?


texts: Thermal decomposition of steam to hydrogen and oxygen; at what temperature is half decomposed and how to calculate?

texts:
In comments below this answer in Space Exploration SE I've said:

  (Wikipedia) says that dissociating water costs about 4.4 eV per bond. If = 4.4 eV and $k_B$ is 8.617E-05 eV/K then that corresponds to a characteristic temperature of something like 50,000 K. Does a nuclear rocket's exhaust get close to that? (I have no idea)

and the reply was:

  but en.wikipedia.org/wiki/Water_splitting says 3000 K. Can anyone clarify?

That Wikipedia article actually says:

  At the very high temperature of 3000 °C more than half of the water molecules are decomposed, but at ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat.

Question: If it takes 4.4 eV to break one hydrogen-oxygen bond, how could half of the water be dissociated at only 3273 K where $k_B T$ only about 0.28 eV?

$$\exp \left( -\frac{0.28 \ \text{eV}}{4.4 \ \text{eV}} \right) \approx 0.94$$

so I'd naively expect only about 6% of the water to be dissociated at 3000 °C.

update: I've just realized that in my naivety I've forgotten to consider that forming H2 and O2 from free atomic H and O is probably exothermic, so my 4.4 eV is an overestimate of the energy difference between initial and final states. But I don't know how to take this into account.


texts:
The concentration of $\ce{Fe^2+(aq)}$ can be determined by a redox titration using

A. $\ce{KBr}$
B. $\ce{SnCl2}$
C. $\ce{KMnO4}$ (basic)
D. $\ce{KBrO3}$ (acidic)

Can anyone please help me on this question? I know the answer is between C and D, since those two are the only redox reactions. However, I don't know how to determine between C and D, as they will both act as an oxidizing agent and Fe will be reduced in both cases (the correct answer is D).


texts: Why are d orbitals used in the hybridisation of PCl5 and similar compounds?

texts:
Phosphorus uses its $\ce{3s}$, three $\ce{3p}$ and one $\ce{3d}$ orbitals for its hybridization in $\ce{PCl5}$ and similar compounds.

However, shouldn't it use its $\ce{4s}$ rather than $\ce{3d}$ orbitals as the former is of lower energy?

I initially thought that this was not the case because hybridization cannot take place between orbitals of different principal quantum numbers, but then learnt that this indeed was possible, for example in coordination compounds with $\ce{dsp^2}$ hybridization such as $\ce{[Pt(NH3)2Cl2]}$.


texts: Logic behind this statement (On Transcription)

texts:
There's this little paragraph in my textbook, parts of which I find redundant. My teacher is absolutely fine with this ("Aaron, you've got to write down what's in the textbook if you want to score in exams, nothing extra...."), but all the same.....

It's regarding 'Why does transcription occur at one DNA strand at a time?'

According to their first point, forming two complementary RNA strands would result in the production of two different proteins for the same character.

Now according to their second point, formation of two complementary strands of RNA side-by-side would just result in them pairing to form dsRNA, which would be transcriptionally inactive and therefore wouldn't take part in the translation process.

The thing is, they've mentioned the second point after the first point, which I find confusing. For if the second point were correct, the first point wouldn't even exist.

Is there a sound reason for the points being stated this way? Am I missing something here?


texts:
Is the azide ion ($\ce{N3-}$) paramagnetic?

How do I use molecular orbital theory to show that it is or isn't?

I drew a sine wave diagram and filled up the $1\pi$ and $2\pi$ MOs, and since there are no unpaired electrons, can I conclude that the ion is not paramagnetic?


texts: Are all fatty acids monocarboxylic acids?

texts:
The answer to this question might solve a multiple choice in my previous chemistry exam, which caused an argument with my teacher.

We know that fatty acids form fats and oil due to their carboxylic groups by forming triesters with glycerol. But is it possible to have a fatty acid with two or more $\ce{-COOH}$ groups to exist naturally? If so, is the property "fats and oils are neutral" just a general property, or does it have an exception?


texts: What is the constant of integration in a series reaction?

texts:
Consider the series reaction

$$\ce{A ->[k_1] B ->[k_2] C}$$

Then

$$\frac{\mathrm d}{\mathrm d t} [\ce{B}] = k_1 [\ce{A}] - k_2 [\ce{B}]$$

We already know that

$$[\ce{A}]=[\ce{A}]_{0} \exp(-k_1 t)$$

Thus far, I have used the method integrating factors, with $u=\exp(k_2t)$, to arrive at the equation:

\begin{equation}
[\ce{B}]= \frac{k_1}{k_2-k_1} \left( \exp(-k_1 t) + C \exp(-k_2 t) \right) [\ce{A}]_{0}
\end{equation}

What would the constant of integration be in this situation?


texts: Specific kind of plastic that won't make fabrics smell?

texts:
I store various fabrics (clothing, cloths, linens, etc.) in RubberMaid RoughNeck plastic bins.  It seems to work fine for a while, but given enough years, the contents take on a strong chemical smell.  These are not stored in a musty or damp area -- they are stored in my living room.  I assume, therefore, that the smell is from the plastic.  Before using the contents again, I need to wash them.  This means competing for machines in the laundry room of a highrise.  This entirely defeats the point of keeping the seldomly used items, which was to have them on stand-by for immediate use upon demand (as opposed to going out to re-buy them).

Are there specific types of plastic that I should look for in a bin to avoid this kind of smell from the plastic?


texts: How much UV lamp power is needed to initiate radical polymerization?

texts:
I'm looking to purchase a UV lamp for initating some radical polymerizations. Is a hand lamp like the type for examining TLC plates (5-10W, like this) enough power to do this, or do I have to buy something a lot more expensive?

In my case, I'm looking to polymerize a fairly small sample (1mm thick, about 100 mm$^2$ of area, encased in 1mm-thick lab slides) and the chemistry will probably be MMA (initiated with AIBN). I'd like to know for my particular case, but it would be great to know if there's some rules of thumb involved (does it depend on the chemistry? does it depend on the amount? Will different power levels give different final results?)


texts: why oxidation states of suphur atoms of Disuphur-monoxide is +2 and 0?

texts:
I) According to my logic, sulfur-sulfur linkage (linkage between same atoms) result in no charge separation.So, the oxidation number of the sulfur atom linked to only sulfur should be 0(zero) and other sulfur being +4 as it is connected to 3(more electronegative) oxygen atoms.

Thus, the oxidation number of sulfur atoms should be +4,0.

II)However, Using X-ray absorption to probe sulfur oxidation states in complex molecules claims that oxidation states are +6 and -2.

III)Again,Determination of Changes in Sulfur Oxidation States
in Prostate Cancer Cells proved that that oxidation states are +5,-1.

These three sets of results left thoroughly confused.Which one of them is correct and why?

Following the same sequence of logic:
My counter-question for the claims (I) and (II) is
"Why the oxidation number of sulfur atoms of Disulfur monoxide is [ +2 and 0 ] instead of [+4 and -2] or [+3 and -1] ?"


texts: Why does gas particle velocity affect rate of effusion?

texts:
I understand why smaller particles have more velocity, but I don't understand what velocity has to do with rate of effusion:

My reasoning is thus:

Pressure is the number of impacts of particles in a given period of time.
If He and Ar are both in balloons at, say, 1.5 atm, both gasses have the same average Kinetic energy but He is moving faster (because it's smaller). Simple enough.
If both gasses are subject to the same pressure, they have the same number of impacts over a given area over a given period in time.
This should mean that each gas has an equal number of particles approaching a hole over a given period of time.
If a hole is big enough for both particles to fit through, the rate of effusion should be the same, since the same number of particles are approaching the exit hole.

For an analogy to explain my thinking ... if you have two lanes of cars going through a checkpoint, one has 30 cars per minute at 50 miles per hour and one has 30 cars per minute at 30 miles per hour, the resulting number of cars through the checkpoint should still be 30 cars per minute in each lane, regardless of their velocity.

My book (and professor, and Wikipedia...) say that it is the higher velocity of He particles which cause the faster rate of effusion; however, from my reasoning, that doesn't make sense except with small enough holes where the size of the particles would have an effect, i.e. the holes are very small in size and He could fit through but Ar could not, or there are simply more holes that He could fit through.

But Graham's law is referring to pinholes, which should be large enough for either atom to fit through.

So why does velocity affect rate of effusion?


texts:
What is the basic difference between formal charge and net charge . Does formal charge take part in resonance .

I searched it on wikipedia , but it is mostly discussing how to find formal charge.

https://en.m.wikipedia.org/wiki/Formal_charge


texts: What is the area that 1 litre of gasoline would spread above the sea?

texts:
I am studying for a general chemistry test with Atkins and Jones "Principles of Chemistry" 5th edition.

In the Chapter 18, page 743, section 18.3, there is this funny question:

  How would you estimate the area that 1 litre of gasoline would spread
  above the water surface?

Observation: I translated it from the Brazilian Portuguese edition. The English version may have different units, but the idea should be the same.

Let's say that the water body is the sea. But it could be a big lagoon, too. It doesn't really matter.

It got me thinking and now I'm stuck. How can we do that?


texts: Are all carbohydrates a subset of alcohols?

texts:
According to the definition,

  an alcohol is any organic compound in which the hydroxyl functional
  group (-OH) is bound to a saturated carbon atom.

Monosaccharides such as glucose contain several hydroxyl groups. Does that mean all carbohydrates are a subset of alcohols?


texts: What could be causing noisy pH measurements?

texts:
I designed and built a hydroponics system with pH logging and I am trying to understand why pH measurements in the nutrient reservoir vary ~ ±0.2 pH while measurements in a separate bottle of probe storage solution only vary ~ ±0.01 pH.  The nutrient solution is in a 3.5 gallon plastic pail, as shown below.  The pH probe is the one with a blue top.  The black probe measures EC and removing it has no effect on the pH noise in the reservoir.

The plot below shows the  logged pH. The abrupt change is when the probe is moved from the nutrient solution to the storage solution.  Note the relatively large noise in the nutrient reservoir and the nearly imperceptible noise in the storage solution.

In the plot,the pH is measured every 5 minutes at the start of a spray cycle, when the pump is off and has not been running for the last ~4.5 minutes.  Note that similar noise occurs when measuring at a rate of 1 Hz.  During the storage solution measurements, the probe tip is in a separate O-ring sealed bottle.  The bottle is sitting at the spot where the pH probe would normally be inserted into the reservoir.

What are potential causes of the pH noise in the nutrient solution?


texts: Quantum numbers required to specify the position of an electron

texts:
In a test today, there was this question:

  How many quantum numbers are required to specify the position of an electron?
  $$(A)\ 1 \quad (B)\ 2 \quad (C)\ 3 \quad (D)\ 4$$

The answer key says that the answer is $(D)$ but I am feel that the answer should be $(C)$ as the spin quantum number describes the angular momentum of the electron.

Please let me know what should be the correct answer keeping in mind that I am a sixteen year old.

Thanks!

P.S. let me know if I should include more or change tags.

Edit: Since it was not clear previously (or so I think), my point is that spin quantum number is not necessary for specifying the position of an electron.


texts: Cyclic voltammetry for irreversible reactions

texts:
I'm new to electrochemistry and I was wondering two things, sorry if these two problems are trivial but I just can't find anything close to this in the literature.
First, the following reaction is irreversible, right? an intermediate Q is formed:
$B + e^{-} \rightarrow Q$
and another reaction follows where it is converted to a different product X:
$Q \rightarrow X$.
Then I'm supposed to sketch a cyclic voltammogram (CV) of this process, but I was taught that for irreversible processes a CV is not useful.
I looked pretty much all day for a similar reaction and the closest I could find is in "A Practical Beginner’s Guide to Cyclic Voltammetry" where the following reactions are presented:
$\text{Ox} + e^{-} \rightleftharpoons \text{Red}$
$\text{Red} \rightarrow Z$
These are defined as EC coupled reaction: reversible electron transfer Er following by an irreversible homogeneous chemical reaction Ci.
The ones I am given are not the same, I think. But I have no idea how to sketch a CV for that process. Am I interpreting the given reactions wrongly?


texts: Precipitation of water-insoluble materials from shower or laundry greywater

texts:
I am currently working on a project to build a filter that aims to separate or salt out the 'dirt' in shower or laundry greywater. The ideal result from this chemical reaction will be such that the 'dirt' will be in a solid-state (precipitate). Meanwhile, the residual water will be 'clean'. The degree of cleanliness of 'clean' I mentioned is such that this residual water is clean enough to be used for non-potable purposes such as mopping the floor.

Therefore, I would like to ask your help in figuring out how can I turn the soap micelles into precipitate, leaving out only 'clean water'?

Disclaimer: I am ignoring soap scum as I can filter that out easily.


texts: What is the oxidizing agent for Fe in the following redox reaction?

texts:
Redox: $\ce{Fe + 2HCl  ->  FeCl2 + H2}$

Oxidation:  $\ce{Fe -> Fe^{2+} + 2e-}$

Reduction: $\ce{2H+ + 2e- -> H2}$

The $\ce{HCl}$ and $\ce{H2}$ are formed by covalent bonds. The $\ce{FeCl2}$ forms an ionic bond.
The iron actually loses 2 electrons to the two chlorines, so the oxidation equation makes sense to me. But the hydrogen is always in a covalent bond with the chlorine or another hydrogen atom, it is always sharing electrons, never losing or gaining, so the reduction equation doesn't make sense to me. When the $\ce{H}$ is bonded with the $\ce{Cl}$, it "has" two electrons because it is sharing a pair with the $\ce{Cl}$. After the reaction, when the $\ce{H}$ is bonded with another $\ce{H}$, it still "has" two electrons because it is sharing a pair with another $\ce{H}$, so no electron was gained as the reduction equation indicates.

After a little a thinking I came up with an answer, which raised even more questions:

Since the covalent bond between the $\ce{H}$ and the $\ce{Cl}$ is a polar bond and it behaves more like an ionic compound because of that, when $\ce{HCl}$ is dissolved in water, the $\ce{H}$ will lose an electron to the $\ce{Cl}$, making $\ce{H+}$ and $\ce{Cl-}$ ions, so there is no covalent bond when $\ce{HCl}$ is in water. The $\ce{H+}$ ions can gain one electron and then make a covalent bond with each other, making $\ce{H2}$ molecules.

But what about the $\ce{Cl-}$ ions in the solution? they have already formed an octet in their outer shell by getting an electron off the hydrogen when they got separated, so they are satisfied. Then why $\ce{Fe}$ atoms oxidize? who is the oxidizing agent? The $\ce{H2}$ molecules are already comfortable with their covalent bond, and the $\ce{Cl-}$ ions are also satisfied with their octet.

I'm very confused.


texts:
For a science/engineering project we are taking pool water (disinfected), filtering to 0.1 microns, and pumping to the kitchen.  Of course there is still 5 ppm of chlorine present so we want to neutralize the chlorine.  Asorbic acid in the form of orange juice neutralized the chlorine,  but I understand that it also creates some amount of HCl. This method is used to neutralize chlorine in water being introduced into ponds, rivers, etc. so that the chlorine does not kill the fish.

Could the asorbic acid actually create enough HCl to be dangerous,  how can I test this,  and what is acceptable?  I used a standard pool testing kit to test the chlorine.


texts:
Background: Glycerin, when heated with a metal coil, decomposes below its boiling point to acrolein, which in turn appears to decompose to formaldehyde and acetaldehyde. (see previous post)

Question: Is there a chemical that could be added, or a process that could be applied, that would lessen the decomposition of glycerine when vaporized?


texts: Must a sample of a deuterated compound be isotopically pure for kinetic isotope experiments?

texts:
I'm trying to do a project on the primary kinetic isotope effect on the dehydroxylation of $\alpha-FeOOH$, goethite. The goethite consists of edge-sharing double octahedra of 3 oxyanions and 3 hydroxyanide. The double octahedra are joined at corners by the oxyanion or hydroxide, leaving empty channels across which hyroxides and oxyanions form hydrogen bonds.

The dehydroxylation mechanism is believed to consist of proton diffusion from the bulk of the material to the surface (likely facilitated by a series of protonations down the hydrogen-bonding channels), then binding of hydrogens to surface hydroxyl group, forming water desorbing. The proton diffusion is believed to be the rate-determining step.

I thought I could lend more evidence to whether this is the case by performing the dehydroxylation on a deuterated compound and a compound of natural isotopic abundance. However, I cannot find the deuterated compound for sale and will have to synthesize it. The most facile synthetic method given time constraints involves potassium hydroxide. We could use deuterated hydroxide, but that would be more expensive. Grey et. al.** were able to do this synthesis with the undeuterated hydroxide, but they didn't report an H/D ratio.

All the papers I've come across on kinetic isotope effect experiments work under the assumption that their deuterated compounds are isotopically pure. It may just be a matter of convention, but would I actually need to do this experiment on an isotopically pure sample? Could I use a sample with, say, an isotope ratio halfway between pure deuterated and natural abundance? Would the calculated kinetic isotope effect (defined as hydrogen rate constant/deuterium rate constant) then be twice what I measure with this partially-enriched sample?

*Surface and Bulk Reactivity of Iron Oxyhydroxides - A Molecular Perspective
Xiaowie Song
Umea University

**2H MAS NMR Studies of Deuterated Goethite (α-FeOOD)
Kathryn E. Cole,†,§, Younkee Paik,†,§, Richard J. Reeder,‡,§, Martin Schoonen,‡,§ and, and Clare P. Grey*,†,§
The Journal of Physical Chemistry B 2004 108 (22), 6938-6940
DOI: 10.1021/jp0486090


texts: Gases produced by pyrolysis of cellulose

texts: I heated cotton in a sealed container (with a small hole) over a natural gas flame. Some gases and smoke were produced. What would they probably be? I can come up with some guesses based on the composition of cellulose: $\ce{CO2}$, $\ce{CH4}$ or possibly other hydrocarbons, $\ce{CO}$, $\ce{H2}$, $\ce{H2O}$, however I do not know which of those they are. Obviously, soot ($\ce{C}$) was also formed, due to the visible smoke particles.


texts: Can someone induce cancer in another person

texts:
Is it possible to poison someone's food on a daily basis in order to give them cancer?

The thing here is that i'm worried someone at my workplace might be poisoning other people's water (each employee has his own packs of water bottles at their desks, also, this person seems to have some mental issues).
It is possible to put chemicals in a bottle with no water leaking via a syringe. So my fear is that this bad person (this person IS bad., believe me) may have poisoned, in a daily basis for 3 or 4 weeks, our water.

So the question is, could this person poison the bottles to make others get cancer? Or another highly dangerous disease?


texts: There are some stereochemical reactions that result in the presence of enantiomers. When moving forward with a practical organic synthesis, how does one usually separate them in order to continue with one of the enantiomers?


texts: Easy-to-do experiments that clearly show outstanding properties of graphene

texts: By chance, we received some monolayer graphene sheets (20 cm x 20 cm) and mixed coper-graphene wires for free at our university. I would like to prepare some very-easy-to-do experiments for the chemistry students that show the awesome properties of graphene, and which could be carried out with very simple lab equipment or even home experiments. What are some good experiments we could do?


texts:
I have looked this theory up on google and found that the theory is that when metal is burnt calx (metal oxide) and phlogiston is created (metal --> calx + phlogiston). Then I found out that phlogiston is a substance supposed by 18th century scientists to exist in all combustible bodies and to be released during combustion. But it later got disproved by Antoine Lavoisier who proved that metal and oxygen when burnt produced calx.

So my questions are:

What exactly is the phlogiston theory and if my understanding of it correct?
What exactly did Georg Ernst Stahl (discovered the phlogiston theory) think phlogiston was?
Why did the 18th century scientists believe that phlogiston existed in all combustible bodies and why not just a product created during the combustion reaction?


texts: How can a conductivity experiment have higher voltage than battery?

texts:
I did an experiment where I tested the conductivity of different solutions and some substances.
We connected a 9 bolt battery, some aluminum foil sticks, and a multimeter that reads the voltage.
It connects like  liquid --> aluminum --> multimeter --> battery --> aluminum --> liquid.

My understanding is that if a liquid contains more ions, it conducts electricity better.
Here's my question. We tested the battery just by itself and it read about 9 volts. When we tested with baking soda, it reads about 9.2 volts.
How can it be higher than the energy source? Does baking soda produce its own electricity?
Also, when we tested deionized water, it came out to be about 8.5. It seems close to 9, but it was one of the lowest of the tested solutions.
Why is it like this? If it's deionzed, shouldn't it be nearly zero? since it doesn't conduct electricity at all? (although there can be impurities so it can have some, but I think 8.5 is still too much).
I don't really understand. Can someone explain why the results came out like this?


texts: The difference between CASSCF and MCSCF methods

texts:
I'm not sure the exact difference between the MCSCF and CASSCF methods. I know that the CASSCF method proceeds by optimizing both the CSFs and MOs (I mean the coefficients), but I don't know if this is also the case in MCSCF calculations.

My guess is that in MCSCF only the coefficients of CSFs will be optimized, but the HF reference MOs would be the same.


texts: What is the mechanisms of this reaction? How feasible is this reaction? Can it happen under relatively mild conditions if it is intermolecular?


texts: Is melting of NaCl a physical and chemical process?

texts:
If I melt $\ce{NaCl}$, I get a molten salt. This means a liquid formed only by ions ($\ce{Cl^-}$ and  $\ce{ Na^+}$). That could mean that the crystal $\ce{NaCl}$ experimented a chemical change:
$$\ce{ NaCl->Cl- + Na+}$$ Like a chemical reaction... The ions have now more space to move and interact with much more ions than in the solid phase. I am trying to get an explanaition why the melting temeprature and the melting heat of molten salts show some erratic behaviour, I mean they do not follow a simple pattern such as that found for n-alkanes or n-alkanols.


texts: What substances in ash may create a green colour and are also soluble in water?

texts:
I have an ash that is high in $\ce{K2O}$ ($ \gt 30 \text{%}$), $\ce{SiO2}$ ($  \gt 10 \text{%}$) and $\ce{CaO}$ ($ \gt 10 \text{%}$), with $\ce{P2O5}$ ($5 \text{%}$) and $\ce{MgO}$ ($3 \text{%}$) also present. When the ash is heated to above $700^\circ \pu{C}$ for $16$ hours for decarburizaton, a color change is observed, from beige to a shade of turquoise, which at higher temperatures ($1300^\circ \pu{C}$ for $10$ mins) becomes a deep shade of green during cooling (the green substance appears to be condensing through the sample).

Whatever substance that is causing this green color appears to be inhibiting melting within the sample (melting temperature should be around $1200^\circ \pu{C}$, according to ash fusion testing), and is soluble in water. I've found through XRD that the ash has significant peaks that correspond to $\ce{KCl}$ in the form of sylvine, but I'm not sure that there is enough chlorine to cause such a deep color change, or that it could cause the color change at $700^\circ \pu{C}$.

So, my question is, does it seem possible that $\ce{KCl}$ is what is causing this color change, and are there other possible candidates that I should test for? (For instance, I've read that potassium manganate will dissolve in water, resulting in a green color too, but I'm not sure how feasible that is).


texts: Creating an exothermic reaction through exposure to oxygen

texts: Is there a way to create a label that when ripped or torn, it's triggered by oxygen and creates an exothermic reaction that heats the object it's surrounding? Say just like a cold cup of coffee or something?


texts: How do bond electrons covers both atoms in covalent bond?

texts:
I want to know how bonding electrons behave when they have to cover for both atoms. Electrons can spin around only one atom right? If so, then what happens when a covalent bond forms?
Let's say we have two covalent bonds between two atoms (for example: $\ce{C=O}$), so they have two pairs of shared electrons.
Since the double bond clearly exists, how do the electrons form the clouds that cover both atoms?


texts: How to calculate weight of CO₂ in one kg of fuel

texts:
I'm trying to do homework and I have the answers to the problems but I can't read the explanation because it's illegible and I can't find how it's done in my notes.

Here's the simplest example:

$$\ce{ C + O_2 \to CO_2}$$

It looks like the answer is 44/12 but I don't understand where the 12 comes from at all. How is a question like this approached? (Didn't know what to search in google to get an explanation).


texts: Octet rule violation in Period 2 elements

texts:
My textbook states,

  Period 2 elements typically obey the octet rule. Period 3 and later elements can expand their valence shells. Elements in Periods 5 and 6 of the p-block show variable valence (the inert-pair effect).

I was surprised that it said period 2 elements typically obey the octet rule. What are some circumstances in which period 2 elements break the octet rule? I though they couldn't because they don't have available d orbitals.


texts: Why does increasing orbital energy mean an electron can be more easily lost?

texts:
Why is the higher the orbital energy, the easier the electron lost?
Also, if the distance between the electron and nucleus is getting father，the   electronegativity is getting weaker, the electron is getting easier to lost?
I feel confused about this two concepts.


texts: I wanted to make some ethanol from baker's yeast and I used sucrose. I've made it and put it in a glass jar. I left it on a warm place (near the radiator) until the yeast died and after they died I distilled the yellowish liquid using simple distillation. When I smelled the product in the receiving flask I was confused. It resembled ethanol a little. The smell was like sweet and medium-intense ethanol. I think that it might be methanol. If there are any reagents or tests other than smelling that I can use at home, please do tell.


texts: I am looking for a solvent for polypyrrole. I read M-cresol and chloroform can be used, but I am not entirely sure.


texts: Can I disable "Display visual cues" by default in Avogadro?

texts: These huge arrows are very annoying to me. I disable them every time I open Avogadro. Is there a way to disable them permanently?


texts:
Take the example of a copper and zinc galvanic cell, connected by a salt bridge of $\ce{KNO3}$. I understand how the reactions will result in positive and negative charges, and that the ions of the salt will migrate to maintain neutrality. But why is the salt needed in the first place?

In one beaker we will have an excess of zinc ions (resulting in positive charge) and the other with an excess of copper ions (resulting in negative charge). If we just have a bridge, perhaps just soaked in water, wouldn't the ions, if not purposefully then randomly, travel across the bridge and maintain neutrality? What is the purpose of the salt then, if it works without a salt?


texts: Basicity af N containing aromatic species

texts:
Hello friends, I got struck in this interesting question on basicity. I am able to get different answers applying different methods.
In general, for these compounds we have to see the lone pair denoting tendency by the nitrogen.
I was able to conclude that IV is most basic. And II is greater than I. Now the problem is between I and III. Whether to consider the -I effect of $\ce{N}$ or $\ce{Ph}$ more effective? And, is -I the correct way to compare among both of these?
I even draw the resonating structures but was unable to conclude anything from there. Please help as to how to proceed.


texts:
Why does ts start just after tm ?
Does the analyte starts spending time in the stationary phase only after the mobile phase has passed and reached the detector ?
Wouldn't there be an overlap between the two ?


texts:
My understanding is that aza-enolates have an advantage over enamines in enolate-type alkylations because the reaction at N is less likely. As a result, unactivated electrophiles can be used (i.e. electrophiles that are not allylic / benzylic / $\alpha$-halo, source: Clayden et al., p. 593)

Question: why is the lone pair on N in aza-enolates less reactive?


texts: How can solids undergo combustion if it only occurs in the gas phase?

texts:
According to the smoldering Wikipedia article, flaming combustion occurs in the gaseous phase. I know butane undergoes flaming combustion in a Bunsen burner because it's a gas, but how can wood undergo flaming combustion at all instead of just smouldering? What gas is there to react with oxygen in the flames? Does it smoulder to create carbon monoxide then the carbon monoxide undergoes flaming combustion? Can charcoal also undergo flaming combustion? I've never seen a piece of charcoal without wood inside it undergo flaming combustion, only smoldering.

Also, when oil undergoes flaming combustion, is it its vapour that reacts with oxygen to produce a flame?


texts: Replacement for Centrifuge in Calcium Content Determination

texts: Basically, I'm performing a lab investigation to determine calcium content in different milk sorts. Since my school didn't have any EDTA, I'm using Sodium Oxalate to form a precipitate with Calcium Oxalate. However, the source I have says that the best way to make these two things react is by centrifuging, a tool which my school lacks. How could I do this without centrifuging for 5 minutes on 1500 RPM? Can I just wait or heat up increase the rate of reaction? Any tips?


texts: How to find partial pressures from a given equilibrium constant Kp?

texts:
I answered wrong on my quiz the following question on finding an equilibrium constant:

For the following reaction, at $1~\mathrm{bar}$ and $300~\mathrm{K}$, partial pressures of $\ce{NO2}$ and $\ce{N2O4}$ are both $0.5~\mathrm{bar}$. If pressure is increased to $2~\mathrm{bar}$ (this is the final pressure), and temperature is increased to $400~\mathrm{K}$, calculate the final composition of the system. $\Delta H$ for this reaction is $57.2~\mathrm{kJ/mol}$; assume it is independent of temperature.
$$\ce{N2O4 (g) <=> 2NO2 (g)}$$

My attempt:
I first found $K_\textrm{p}$:
$$K_p (300~\mathrm{K}) = \frac{P^2(\ce{NO2})}{P(\ce{N2O4})} = (0.5^2)/0.5 = 0.5$$
Then I used
$$\ln\left(\frac{K_p(400~\mathrm{K})}{K_p(300~\mathrm{K})}\right) = - \frac{\Delta H}{\mathcal{R}} \left( \frac{1}{400~\mathrm{K}} - \frac{1}{300~\mathrm{K}}\right) $$
I solved for $K_\textrm{p}$ at $\pu{400 K} = 92695.44$
This is where everything went wrong. I can not figure out how to get from $K_p$ to partial pressures. All I got to is the following line:
$P_\text{total} = 2P(\ce{NO2}) + P(\ce{N2O4})$, since $n(\ce{NO2})$ to $n(\ce{N2O4})$ ratio is $2:1$. I assumed they exert pressure proportionally.
Can some one guide me in the right direction?

Multiple choice answers:

$P(\ce{N2O4(g)}) = 0.0252~\mathrm{bar}$; $P(\ce{NO2(g)}) = 1.9748~\mathrm{bar}$
$P(\ce{N2O4(g)}) = 0.039~\mathrm{bar}$; $P(\ce{NO2(g)}) = 1.961~\mathrm{bar}$
$P(\ce{N2O4(g)}) = 1.45~\mathrm{bar}$; $P(\ce{NO2(g)}) = 0.098~\mathrm{bar}$
$P(\ce{N2O4(g)}) = 1~\mathrm{bar}$; $P(\ce{NO2(g)}) = 1~\mathrm{bar}$


texts:
Does ozone have a color or is it colorless? I have heard that ozone has a bluish color.

Could someone explain this observation scientifically?


texts: How to tell the difference between lysine and the N-terminal amino acid in DNP labeling?

texts:
The N-terminal amino acid of a protein can be identified by reacting the N-terminal amine with FDNB (1-fluoro-2,4-dinitrobenzene), or Dansyl chloride, or Dabsyl chloride, then digesting the protein with acid.
This question points out that the epsilon amino group of lysine can also react with the labeling reagents, creating a side-chain labeled lysine. Dinitrophenyl (DNP) derivatives of amino acids (specifically epsilon-DNP-lysine)
But if we're just looking for the labeled amino acid, how do we tell the difference between the N-terminal amino acid and lysine?
I suppose that if we ran the amino acid mixture on HPLC or TLC that the epsilon labeled lysine would have different retention times, and we could learn to ignore those peaks once we knew what lysine looked like.


texts: Why does KCl come in amber coloured bottles?

texts: I remember from school that photosensitive chemicals are kept in amber coloured bottles. Is KCl photosensitive? I read up the impurities list on the bottle and it says that it may have bromides too? So is it because of the KCl or the bromides? If it is due to the bromide, what sense does it make since it would react just to form another impurity?


texts: What causes the colour when conducting flame tests on solid salts?

texts:
The normal technique for flame tests is to dip a clean nichrome or platinum wire into a solution of the relevant salt, and observe the resulting flame colour when inserting the wire into a non-luminous Bunsen flame.

But what is the species undergoing the electron transition that emits the light of characteristic frequency?

One explanation suggests vaporisation and then atomisation of the sample, with the light emission occurring from the excited atom, rather than ion. Another suggests that it’s the ions undergoing the electronic transitions. The Wikipedia article is somewhat vague on the question.

Now, I was doing some flame tests for a student, and in the absence of an available nichrome or platinum wire I simply took a pinch of the solid salts ($\ce{NaCl}$ and $\ce{KCl}$ respectively), and threw it into a non-luminous Bunsen flame.

The characteristic yellow and lilac flame colours were instantly and repeatably observed.

My question is this:

Given that the outer regions of a Bunsen flame are at less than $1000\ \mathrm{^\circ C}$, and that the boiling points of $\ce{NaCl}$ and $\ce{KCl}$ are $1413\ \mathrm{^\circ C}$ and $1420\ \mathrm{^\circ C}$ respectively (according to Wikipedia), it seems unlikely that the instantly generated characteristic colours originate from individual ions or individual atoms.

So what is the species exhibiting the electron transitions? Is it the metal ions still within the crystal lattice?

Edit: I should emphasise that the flame colour was observed in the outer regions of the flame, not the super-hot tip of the inner cone. So $1000\ \mathrm{^\circ C}$, not $1500\ \mathrm{^\circ C}$ by any stretch of the imagination. And I don’t at all buy the notion that the colours were simply the glow of hot solid particles emitting black body radiation. The colours were the characteristic sodium yellow and potassium lilac, instantly recognisable by anyone that’s familiar with simple tests like these.


texts: Why is maltose a reducing sugar but not sucrose, even though they're both disaccharides?

texts:
I came across this on Wikipedia:

  Many disaccharides, like cellobiose, lactose and maltose, also have a reducing form, as one of the two units may have an open-chain form with an aldehyde group. However, sucrose and trehalose, in which the anomeric carbons of the two units are linked together, are nonreducing disaccharides since neither of the rings is capable of opening.

https://en.wikipedia.org/wiki/Reducing_sugar#Aldoses_and_ketoses

I took the following Haworth projection of sucrose for comparision.

That's all fine and dandy, but the thing is, I can't seem to find any source that (explicitly) explains why this whole 'ring-opening' business even happens in disaccharides like maltose, but not in sucrose.

The Wikiedia article probably implies that this has to do with the fact that both the monomers of sucrose are bound through their anomeric carbons, which is not the case with maltose. A quick look at the structures of maltose and sucrose confirms this, however; pardon me if I'm being dense here (I can't seem to think straight today...don't ask me why, I'm clueless myself), but I don't see how that piece of information helps.

Can anyone explain this disrepancy?


texts: How can I use sunlight to heat a RBF and reflux a reaction?

texts:
This may seem like a off topic question but I really need help on it. I am currently working on a polymerization reaction in which I'm breaking down plastic polymers into smaller molecules. However, since this is a green chemistry project, I decided, with the suggestion of other chemists, that I should a method that doesn't require a lot of electrical energy to heat it. One idea was an enzyme, but I decided I want to use solar energy to reflux the RBF. I have a few ideas and please comment on them and also provide your own suggestions:

First is using a parabolic mirror below the flask to focus the heat towards it.
Second idea is painting the RBF black and hoping that is sufficient to heat it to reflux.


texts: If an unsaturated air parcel ascends adiabatically in the atmosphere with an initial temperature, would the final temperature of the air parcel, when it reaches it's destination, be the same at the initial temperature since it does not exchange heat with it's surroundings?


texts: Stereoselectivity of dihydroxylation with osmium tetroxide

texts:
Dihydroxylation responds to steric effects and proceeds at less hindered positions. What will be the major product in the following reaction if the reagent used is $\ce{OsO4}$ followed by $\ce{NaHSO3}$?

Won't interactions between $\ce{- OH}$ bring $\ce{OsO4}$ on the same side as $\ce{- OH}$? Or will the $\ce{OH}$ sterically hinder the reagent from attacking the olefin from the same side?
Why I am I having this doubt is because I read that $\ce{m-CPBA}$ can be directed by hydroxy groups. For example, if the compound given below were to react with $\ce{m-CPBA}$, the product formed is:

The reason is because of interactions between $\ce{m-CPBA}$ and the substrate like this:

EDIT:

It's given in Classics in Stereoselective Synthesis by Erick M Carreira and Lisbet Kvaerno that $\ce{OsO4}$ with $\ce{NMO}$ does not respond to directing effects while $\ce{OsO4}$ with $\ce{TMEDA}$ responds to directing effects.

It's given in the same book that the reason why $\ce{OsO4}$ doesn't attack on the same side as $\ce{-OH}$ is because of electrostatic repulsions between oxygen atoms. These repulsions increase in E-alkenes. Fair enough. But won't the same reason apply for $\ce{m-CPBA}$? Why won't the oxygen atoms repel $\ce{m-CPBA}$ but only $\ce{OsO4}$?


texts: Can we write "1-Chloro-ethane" when a single chloro group is present in the ethane? I think only one position is possible for the chloro group in ethane.


texts: How adding one more electron increases the ionization energy?

texts:
Elements of group 6A, compared to 5A, require less ionization energy due to the paired electrons of 6A.

But a question arises: why does group 7A, compared to group 6A, require more ionization energy in spite of the paired electrons in group 7a too.

Regardless of the general trend that the ionization energy increases as we go from left to right in periods, why didn't we apply the same procedure as the first comparison?


texts:
Chlorine is an oxidizing agent, so could it replace oxygen? If so, what would be the products, and how much energy would such reactions release? Do any other carbohydrates burn in chlorine? I cannot find any information on this.

Clarification: How does glucose interact with chlorine chemically?


texts:
I bought an electronic meter which measures the concentration of oxygen in air. But I think the sensor has failed because it is too old, as it had a crusty substance coming from it.but I can no longer find spare sensors for it.

How might this sensor have worked? I presume the property of some substance was measured; this property changes with the concentration of oxygen.

Perhaps one of these:

Its resistance changed as air was passed through some sort of chemical, and the resistance measured to determine the oxygen concentration.
Or perhaps its opacity to light measured with an LED and an appropriate optic sensor.
Or the volume of the substance changed, or some other property, which ultimately varies the capacitance.

What substance might this have been? I want to make my own device - I don't intend to fix this one, so I don't need to identify the substance used in this particular sensor.


texts:
My father* wants to synthesize Sodium orthovanadate, and has found out it is prepared from Vanadium pentoxide and a strongly alkaline solution of NaOH, or by fusion with NaOH but cannot find a detailed method, e.g. about quantities, separation from excess alkali, drying, etc.

I** haven't been able to find out much by googling or searching Pubmed: most methods I've found deal with stabilizing the solution, not with the complete synthesis. Could you point us to a complete protocol?

*chemist, but his English is not so great.

**not a chemist anymore


texts: What is the correct numbering & order for this molecule?

texts: I'm having a hard time understanding why the numbering for this molecule is: 4-bromo-1-tert-butyl-2-methylcycloheptane, instead of: 1-bromo-4-tert-butyl-3methylcycloheptane. Is it just because the overall numbers are lower? I just figured the numbering out by going in alphabetical order, which I now know is wrong. But is that the reason the first numbering is correct?


texts: Why is pH used as a measure of acidity if not only hydronium ions can act as a acid when in solution?

texts:
The Brønsted-Lowry theory tells us that the when an acid such as $\ce{HCl}$ dissolves, the following reaction takes place:
$$\ce{HCl + H2O <--> Cl- + H3O+}$$
It is said that the hydroxonium ion is what functions as an acid when a base is added to such a solution. However, there will indeed remain some $\ce{HCl}$ molecules in solution. So wouldn't they also act as an acid in some instances?

This problem becomes more apparent when we look at weak acids such as ethanoic acid. There are many many ethanoic acid molecules in comparison with the hydroxonium ions. Why is the acid 'weak' if the ethanoic acid molecules can just react with the base anyways?

To further explain where my problem is, consider the scale which we use to measure the 'acidity' of a solution, the pH scale. Consider a scenario where I have 2 different solutions of ethanoic acid and $\ce{HCl}$, both of the same concentration. The $\ce{HCl}$ solution will definitely have a lower pH and will be considered 'more acidic'. But would it really be correct to call the $\ce{HCl}$ solution 'more acidic' just because the $\ce{HCl}$ has dissociated to produce a much higher hydronium ion concentration? The ethanoic acid solution will have a lower hydrogen ion concentration, but the ethanoic acid molecules can still act as an acid … The main problem here is with using pH as a measure of acidity if molecules which haven't dissociated may also act as acids …


texts: How is the potential difference between the outer and inner surface of the glass bubble in a glass electrode measured if an Ag/AgCl wire is used as the indicator electrode and Ag/AgCl/KCl is used as the reference electrode? In the Nernst equation for the reaction, hydronium ions don't participate.


texts: Balance Repeatability Sample or Population for SD

texts:
A question for the masses about standard deviation (SD), selection of population vs sample in balance measurements.

Analytical balances are typically checked for repeatability by taking 10 weight measurements and finding the uncertainty by calculating standard deviation.

There are two forms of standard deviation: population and sample. Population divides the sum of differences squared by $n$; where as, sample divides sum of differences squared by $n-1$.

If I take 10 measurements of a standard weight, is this not the entire population? Or does the fact that I will repeat this test in the future make it a sample? I would typically select population in this case; however, most of the balance manufacturers I am reading are quoting $n-1$. What is the correct SD?


texts: Will equilibrium ever establish if one of the products starts to disassociate?

texts:
When $\ce{N_2O_5}$ is heated at a certain temperature, it disassociates as $$\ce{N_2O_5 (g)<=>N_2O_3 (g) + O_2 (g); K_c = 2.5}$$ At the same time $\ce{N_2O_3}$ also decomposes as $$\ce{N_2O_3 (g)<=> N_2O (g) + O_2 (g)}$$If initially 4 moles of $\ce{N_2O_5}$ were taken in a $\pu{1 L}$ flask and allowed to disassociate, and at equilibrium $\ce{[O_2]=2.5 M}$ then find equilibrium concentration of $\ce{N_2O_5}$

Lets say the first reaction reached equilibrium and then $\ce{N_2O_3}$ started decomposing. This means more amount of $\ce{O_2}$ will be produced and the equilibrium for the first reaction will get disturbed.
The first reaction will then proceed backwards as predicted by Le Chatelier's principle (since the concentration of $\ce{O_2}$ is more than the equilibrim conc.).
Due to this the oxygen level will drop and equilibrium for the second reaction will get disturbed and $\ce{N_2O_3}$ will decompose further to form oxygen.
But this process will go on forever. There is definitely wrong with this. Will this really happen or is there some other mechanism at work?


texts: How to get specific concentration of carbonic acid in solution?

texts: I wanted to know if there is a way of getting specific quantities of carbonic acid? Carbonic acid is water + $\ce{CO2}$ but not all the $\ce{CO2}$ dissolves in water. So if I wanted $5\:\mathrm{g}$ of carbonic acid solution, how much $\ce{CO2}$ should I add to water? Is there a way to know how much has been added?


texts: White mucous substance forming around iron paper clip during electrolysis

texts:
I'm using a graphite cathode and an iron paper-clip anode, in a saltwater solution, basically to produce rust.

I've done this before with no complications, but this time I noticed a white, mucous material forming around the paperclip, quite late into the process.
I had eaten about half-way through the clip when I started noticing the cloudy white stuff. That suggests that whatever is producing it, is at the core of the clip.

If I try to move it, the mucus immediately detaches and sinks to the bottom of the jar, where it stays above the iron hydroxide.
Everything else seems to be in order, colour-wise.

Another thing is, if I shake the mucus off, the paperclip starts off clear, before turning black again, as it should be.

Does anyone have a clue of what this might be?
I know zinc oxide is white, but I'm pretty sure zinc and iron don't mix.

I've turned the power off, just in case it's something I -really- don't want to handle without protection.


texts: How to calculate a reaction's DeltaH using a MM forcefield calculator software?

texts:
I want to calculate $\Delta H$ for hydrogenation of benzene and producing cyclohexane using MM+ Force Field Energy. I am using Hyperchem for energy calculation and optimization. I calculated the energy for cyclohexane and then I calculated the energy for benzene. But the difference of two energies is totally false. The calculated energy is $8~\mathrm{kcal/mol}$ however the real value is $-49~\mathrm{kcal/mol}$.
Is it a true way to calculate $\Delta H$? If not, how can I do it ?


texts: Reactivity of meta and para xylene towards nitration

texts:
Is meta xylene more reactive towards nitration or is it para xylene?

I would say it is meta xylene as it has two methyl groups meta to each other. Since both are activating groups, there would be a greater electron density at the ortho and para positions with respect to both the groups. This would make meta xylene more susceptible to nitration (EAS) as compared to para xylene.


texts: How do I decide the electromeric effect on pent-2-ene?

texts:
There are two possible case
π electrons shifting to C2
In this case, nucleophile attacks C3
It is stabilized by +I effect of two ethyl groups
π electrons shifting to C3
In this case, nucleophile attacks C2
It is stabilized by +I effect of a methyl group and a propyl group.

How do I decide which one is more stable, and ultimately, which one is favoured?


texts:
This is the boiling-point elevation equation:

$$
\Delta\mathrm{T}_{b}=ib\mathrm{K}_{eb}.
$$

If we do the limit of the above, for $b\rightarrow\infty$ we find that the boiling-point elevation is infinite. How this could be explained under a physical view?

$$
\lim_{b~\rightarrow~\infty}ib\mathrm{K}_{eb}=\infty,~\text{if}~i\wedge b > 0.
$$

For example, if we use a solute molality that is so big that the solution would be something like the pure solute, the final boiling-point of the solution, in the case of water as solvent for example:

$$
\mathrm{T}_{b}=ib\mathrm{K}_{eb} + 100\mathrm{°C}.
$$

wouldn't be like the boiling-point of the pure solute? I mean, something like this:

$$
\lim_{b~\rightarrow~\infty}\mathrm{T}_{solution}=\mathrm{T}_{solute}.
$$

Now, please forget what I've said above about $b\rightarrow\infty$. And take a look at this:

$$
T(b) = 0.86b + 64.7.
$$

As you can see is, the boiling-point of a solution of $\mathrm{CH_3OH}$ with $\mathrm{H_2O}$ as solute would be $322.7\mathrm{°C}$ for $b = 300$. This it's weird to me  'cause that temperature would be about three times higher then the boiling-point of the pure water!

So the following:

$$
\mathrm{T}_{b}=ib\mathrm{K}_{eb} + \mathrm{T_{solvent}}.
$$

holds true if

$$
b = \frac{x~\mathrm{g}_{solute}}{1000~\mathrm{g}_{solvent}} \le 1
$$

right? If yes why (in the above case):

$$
0.86\frac{1000~\mathrm{g}}{18.01528~\mathrm{g}/\mathrm{mol}}\frac{1~\mathrm{mol}^2}{1~\mathrm{kg}} + 64.7~\mathrm{°C} = 112.4~\mathrm{°C}
$$

?


texts: Predicting isotope patterns in mass spectrometry

texts:
Imagine you have a mixture of $\ce{^1H}$, $\ce{^2H}$ and $\ce{^3H}$ (hydrogen, deuterium and tritium) present as diatomic molecules and that the numbers of the atoms of the three species are the same. Sketch the mass spectrum.

The book's answer is

For peaks of mass= 2, 3, 4, 5, ratio of heights = 1:2:3:2:1.

I’m not getting why the answer is this?
Why there is no peaks of mass 1, is it because $\ce{H2}$ consisting of $\ce{^1H}$ can break in mass spectrometer?


texts: Measuring pH in ferric oxalate solutions

texts:
I have a problem with measuring $\mathrm{pH}$ in ferric oxalate solutions ($\sim 5~\text{to}~\pu{10 g L-1}$ $\ce{Fe},$ $\pu{0.8 M}$ oxalic acid, $\pu{25 °C}$). While I am sure about the $\mathrm{pH}$-meter device and buffer solutions ($4$ and $7$) and also the good function of my electrode (Sentek) in other solutions, the $\mathrm{pH}$ value does not stabilize at all in such a way that it continuously decreases as far as the pH becomes negative and eventually, under-ranged.

Is there any interference or any requirements for $\mathrm{pH}$ measurement in oxalate solution?


texts: The pyridine/benzene stability 'paradox'?

texts:
So, apparently pyridine is more stable than benzene. My lecture notes are saying that pyridine will undergo electrophilic aromatic substitution much more slowly than benzene will, which got me thinking - slower means the compound is more stable (higher activation energy). But isn't benzene more aromatic than pyridine?

I checked the heats of hydrogenation and it checks out - pyridine is indeed more stable than benzene. I'm a little bit lost though, because I don't get where this unexpected stability is coming from. Surely benzene is an ultra-stable compound because of the superb resonance it has (higher resonance energy than pyridine), electron density is (AFAIK) equally distributed around the ring, whereas this isn't the case in pyridine.

Also, the reason I call this a 'paradox' (in my head, at least) is because I've been learning about how benzene is a really stubborn compound when it comes to getting it to react - it doesn't undergo normal alkene addition reactions and all that - yet pyridine is quite a bit more stable than benzene and it has a million different weird reactions going on (acid/base, nucleophilic, EAS, N-oxide formation, metal complexes, etc. etc.)

Apparently pyridine is more stable, yet more reactive due to the lone pair electrons on the nitrogen (which allow lots of crazy stuff). In general, is it true that more stable = less reactive? That's the basic assumption I've been using until now - based on thermodynamics (?) - but I've seen a couple of things that make me think it's not as simple as that. Sorry for the rambling, just blurting my questions out!


texts: Confusion regarding the mechanism of acidic/basic buffer solutions

texts: While learning about acidic and basic buffer solutions we were told that they can resist pH change if we add small amounts of acid or base by neutralizing the $\ce{H+}$/$\ce{OH-}$ ions from the added acid or base. But I am confused about the fact that if we add a small amount of base to an acidic buffer then after neutralization of the excess $\ce{OH-}$ ions from the base by the $\ce{H+}$ ions from the buffer, shouldn't the concentration of $\ce{H+}$ ions in the solution decrease, thereby making the solution acidic and reducing the $\mathrm{pH}$. (vice-versa for the addition of acid to a basic buffer)


texts: On what factors does amine inversion depend

texts:
What factors promote amine inversion? Like bulky groups around the nitrogen atom or less sterically crowding groups?

Are there any other factors that affect amine inversion? Does the electronegativity of the atoms bonded to nitrogen affect amine inversion?


texts: What is the exact definition of state functions? How to determine state functions?

texts:
How do you know if something is a state function? I know Internal Energy (U) is a state function since it is the sum of energies, which is constant at a given time.

However I don't know for sure if $\Delta$U is a state function. I know that $\Delta$U$= U_{final}-U_{initial}$, and so any path from final to initial will yield the same $\Delta$U. So by this definition any $\Delta$ function should be a state function.

As a result I would expect Heat ($q$) to also be a state function since $q=\Delta$TE, but this is not the case.

Where am i going wrong in my understanding? I understand the "altitude" analogy, however i need a more technical definition with chemistry terms.
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texts: Galvanic corrosion between nickel brass nut and stainless bolt

texts:
I am planning to install something on a boat that will be in salt water, and my question is, will the nickel plated brass fastener not corrode if I connect it to stainless steel?

I looked it up on the chart and it says that there should be less then 0.15 V difference in the "Anodic Index" for harsh environments and while brass and stainless is within the 0.15, nickel is just outside.

The environment is not entirely harsh as well, as these will be used to fasten just the windows, so while there could be water there, mostly it will be fresh water from rain and the occasional spray from salt water.