texts: How do you calculate the norm of a function describing a molecular orbital?

texts:
I'm a bit confused by a past paper question I came across for one of my courses, shown below.

  The wavefunctions corresponding to the lowest, $\psi_{1}$, and second-lowest, $\psi_{2}$, energy molecular orbitals in 1,3-butadiene are:
  $$\psi_{1}=0.372\phi_{1} + 0.602\phi_{2}+0.602\phi_{3} +0.372\phi_{4}$$
  $$\psi_{2}=0.602\phi_{1} + 0.372\phi_{2}-0.372\phi_{3} -0.602\phi_{4}$$
  where $\phi_{i}$ is the $p_{z}$ orbital on atom $i$. Calculate the norm of $\psi_{1}$, and the overlap between $\psi_{1}$ and $\psi_{2}$. Is the result what you would expect? Explain.

Neither calculating norm nor the overlap between 2 orbitals in the way the question asks came up.
I assume by norm it means the normalisationg factor, but that makes no sense to me since it's already normalised. I assume the overlap should be 0 since they should be orthonormal, but don't know how to show that. I'd really appreciate some help!
Sadly the lecturer for the course has contracted Covid-19 and so of course is not available to answer questions.


texts:
What are cubic zirconia (CZ) gemstones usually colored with?
According to wikipedia the following dopants are being used:

Cerium
Chromium
Neodymium
Erbium
Titanium.

Chromium is quite colorful and can be used for green CZ. However I'm worried about Cr(VI) which is carcinogenic being used, or other equally toxic substances. (manufacturing can take place in countries with less strict regulations than EU and US).

On the other hand, when it comes to pottery used for cooking food if it is properly fired practically no lead migrates to food.
So, if pottery used for boiling acidic food is safe when "properly fired", I'm assuming that the CZ (which only comes in contact with the skin) should be safe regardless of the dopants used since it can reach temperatures of 1400 °C.
Questions:

Is my above assumption correct?
Is there any research on CZ toxicity or allergies.
Could any other toxic dopants be used?


texts: Why does equilibrium favour weak acid or weak base?

texts:
For example, in the reaction $\ce{NaOH +HCl->NaCl +H_2O}$, the products are favoured by a factor of approximately $10^{24}$.
Is this a general rule? Is it because the products are more stable than the reactants?


texts: Electrons flow difference between circuit and electroplating process by considering battery's positive and negative side

texts:
Electrons flow  from the negative end to the positive end of a battery (via a circuit) but in electroplating process electrons flow from the battery's positive end  to the battery's negative end. Why this happens ?
Here I want to know about the electrons flow difference in battery's positive side  to the battery's negative side between circuit and electroplating system.

Here in the first figure by considering battery's positive and negative side electrons flow from positive side to the negative side.

But in this second figure by considering battery's positive and negative side electrons flow is opposite from the first figure.


texts: I thought Inositol was clearly chiral since it has 6 asymmetric C atoms. But friends of me argue that it is achiral and i've found websites say the same (http://bip.cnrs-mrs.fr/bip10/Inositol-EJB.pdf). So what am I missing? Is it chiral or achiral?


texts: Spices are absorbed or adsorbed in food?

texts: When we cook food, we add several spices and condiments which enhance color, taste and smell. Are these spices and condiments just adsorbed on the food particles? Or are they absorbed? For example using pepper while cooking a piece of chicken, would it just stay on the top of the leg (adsorbed)? Or get absorbed?


texts: Fractional distillation of a product differs from the components listed in the SDS. What am I doing wrong?

texts:
I recently bought a product called Prestone De-Icer for Windows and Wipers which claimed to contain Methanol. I was puzzled when using it to note that it did not smell much like Methanol so I looked up the SDS for the product which stated that it contained 50-100% Methanol, 1-10% Ethylene Glycol & 1-5% Carbon Dioxide.

Out of curiosity I decided to carry out a fractional distillation to see just what the constituents were and was puzzled to see the thermometer shoot up through the Methanol BP at 66C mark without stopping and the first stop was about 76C which would suggest Carbon Tetrachloride. It then stopped at about the 79C mark which would indicate Ethanol and then carried on up to about 98C which would suggest Heptane.

So my question is this - Is there something wrong with my methodology or interpretation of what I am seeing or is it possible that the manufacturer is in error in the SDS. The latter would be very serious if true since the SDS would be the resource used should it be suspected that someone has been poisoned by the product.

My instinct is to suspect that I am doing something wrong but for the life of me I can't see what it could be. The thermometers I have used ( three in all ) are calibrated to 0.1 degree and were one mercury, one alcohol and one digital and all agreed to within 0.4C max deviation.

I should point out that I am not a professional chemist, just an amateur who has taken the hobby up in retirement so I am quite prepared to be told that I have got it wrong. It's all part of learning in my opinion.

Here is a link to the SDS -
http://www.homedepot.com/catalog/pdfImages/2c/2cd5847a-9dd0-4cf0-a5ef-83efbd532f4c.pdf

I am including a photo of the setup I am using to do the separation. The Vigreaux column is actually wrapped in aluminium foil.


texts: Solution, hardener and metal required to cast key duplicates

texts:
I just watched this YouTube video for a DIY key duplication system and was trying to figure out what all the material components could be:

The "mold solution" (parts 1 and 2)
The "hardener"
The "low melting point ingots"

The mold gel has to be resilient enough to withstand molten metal (even if the melting point is low), but I can't figure out what materials would fit the bill. Any ideas?


texts: I have learned that in primary classes  that sea water is salty and I had also wondered that, what makes it salty? and my question is, where does sea water gets its salt?


texts: IUPAC nomenclature: putting the number before or in the middle of the name

texts:
Which is preferred according to "strict" IUPAC:

2-pentanone or pentan-2-one ?


texts: What is the energy released in chemical reactions?

texts:
I have heard that chemical reactions create energy.  I wanted to know how this energy was created (specifically light energy) and how this energy came about.  I wanted to know if the energy produced was made of particles (for example, light energy is made of photons).

My answer I already knew about heat, kinetic, potential, and sound energy.  What I was really looking for was light energy, which is caused by a phenomenon known as chemiluminescence.


texts: What are some chemical engineering bottlenecks for a perfectly synthetic meat?

texts:
Recently, the Impossible Burger has become more and more popular. It seems to be a very big effort and even making it's way to the top restaurants. Of course, this has been something that scientists have been working on for decades and is a mix of sciences such as gastronomy, chemistry and others.

In such experiments as the Impossible Burger, I keep hearing neuroscientists and flavour experts trying to replicate the smells, the texture and other characteristics by what I understand it to be brute testing (although I am sure they do some biological and chemical modelling to supplement the engineering process). What it got me thinking about was what are some bottlenecks to making a PERFECT replica of meat. As a mechanical engineer graduate myself, my knowledge is limited on the issue. What holds back chemical engineers and scientist to identify the contents of meat and exactly produce a synthetic copy? We have techniques like IR spectroscopy and many other advanced methodologies for identifying chemicals. Is it a manufacturing complexity or is it just another case of expensive computational costs and insufficient observational techniques to fully figure out the structure of meat?


texts: Calculating the pH of the endpoint in a titration of weak acid and strong base

texts:
Show that the pH at the endpoint in the titration of $\mathrm{0.100\ mol\ dm^{-3}}$ ethanoic acid with $\mathrm{0.100\ mol\ dm^{-3}}$ sodium hydroxide is 8.72. The dissociation constant Ka of ethanoic acid is $\mathrm{1.80\ x\ 10^{-5}\ mol\ dm^{-3}}$.

I managed to obtain the value of Kb using the formula (Ka x Kb = Kw = $\mathrm{10^{-14}}$).

I worked out the chemical equation at the endpoint which is:

$$\ce{CH3COO- + H2O <--> CH3COOH + OH- }$$

However, I am unsure as to what the concentration of $\ce{CH3COO-}$ should be.

I understand that if I find [$\ce{OH-}$] then I would be able to find pOH and by extension pH.


texts: Ventilating combustion byproducts in water heaters

texts:
I'm designing a system which will heat up water by burning natural gas which is commonly available. I would like to have a slow flame because water will need to reach $\mathrm{70^\circ C}$ and stay there. Having in mind that even weak winds can extinguish the flame as well as the system will be put together with other objects and systems in a tight space I decided it would be a good idea to build a chamber around the flame nozzle thats directly attached to the water container. I will build a small opening in the chamber to which I will attach a tube which will feed atmospheric air into the chamber through some kind of a filter (probably a piece of cloth) to keep it clean. I read that the byproducts of burning natural gas are $\ce{CO2}$ and water vapor which raises 2 questions:

Do I have to worry about humidity increasing in the chamber and eventually water forming on the inside, in extreme conditions water in the system can be as low as $\mathrm{-20^\circ C}$ (I call it water but it will be actually antifreeze)
Do I have to worry about the chamber filling up with $\ce{CO2}$ and eventually putting the flame out which will then be unable to be lit again. Is there anything I can do such that the byproduct will exit the chamber naturally without me having to do any work for it.

Edit:

So far from the comments it was made clear that it would be better to use a condensing boiler design efficiency wise, however due to construction complications that I'd like to avoid I'll stick with only the hot half of the design in question where the water will pass through a tubing inside the chamber where it will be heated, instead of applying heat to the container directly. There will be an exhaust that will utilize natural convection to expel the exhaust gasses in addition to the inlet.


texts:
Why does paper crumble on getting wet?
This is something I have noticed hundreds of times but cannot think of an explanation.

Does it have anything with water disturbing the intermolecular forces between cellulose micro fibrils in paper or something else?

Also, one peculiar observation is that it does not crumble immediately but only after the water evaporates? Why?


texts: How can I simulate chromatograms and spectra?

texts: Is there a tool which allows to generate simulated chromatogramms and spectra and export it into a mzML file? There is e.g. psims which allows to write mzML on a low level. However I was not able to find a high level tool which allows to define chromatogram shapes via a e.g. a GUI.


texts: How can I wet etch Nickel Chloride (NiCl/NiCl2) off a GaN sample

texts:
Apologies in advance for what may be a basic chemistry question - I'm asking from the point of view of microlithography.
I have a Gallium Nitride sample which I have etched in a Ar/Cl plasma with a Nickel hard mask (which starts off nominally 100 nm thick). Normally I would remove the nickel hard mask with a dilute (~5-10%) Nitric Acid solution, but in this case it seems like the mask has become chemically resistant to this etch.  Or at least it seems like there is some residue/skin that is hard to remove after the first attempt when I do see some removal.
I have read that at elevated temperatures (>150C) in a chlorine plasma, Ni can react with the plasma to grow NiCl or possibly NiCl2 (?).
Vigne et al. J. Appl. Phys. 114, 103303 (2013)
I was wondering if there were any standard wet chemical etches I could use to dissolve/remove this?
So far I have tried several etches which are supposed to work for Nickel without much effect - I haven't found anything specifically for NiCl:

Dilute Nitric Acid (10 HNO3 : 90 H2O, (and subsequently 15:85, 20:80)
Dilute Aqua Regia (100 HCl : 20 HN03 : 40 H2O) Dilute
Nitric/Acetic/Sulphuric Mix (25 HN03 : 25CHO3COOH : H2SO4 : 50 H2O)

Note... all of these at room temperature, with the quantities being of the standard lab grade acids (eg for nitric acid it is 30%) - so the actual percentages of the mixes will be slightly less than here.


texts:
Which of the following compound doesn't contain peroxy oxygen?

  $\ce{CrO5}$
  $\ce{Cr2O3}$
  $\ce{Na2O2}$
  $\ce{BaO2}$

I think peroxy oxygen is peroxide, am I right?. I have read in this answer that there is no direct way to recognise peroxide oxygen, and I think that's the reason no one has taught me that in the school.

I am familiar with many peroxides like $\ce{Na2O2}$, $\ce{BaO2}$, etc. But I not able to recognise between 1 and 2.

Is there any way for this type of question to recognise peroxide oxygen?  And if there is no way to determine then really I need to remember all, because we can't use X-ray crystallography in exam or while studying high school chemistry!

Answer given is 2. $\ce{Cr2O3}$


texts: What product will be formed from the side chain oxidation of 4‐ethyl‐1,1‐dimethyl‐3,4‐dihydro‐2H‐naphthalene?

texts:
Benzylic hydrogen is required for the side chain oxidation of benzene. But for this compound the top branch connected to the benzene ring does not have a benzylic hydrogen. So, will the top branch be broken off in the process of oxidation?
The reagents and conditions for the side chain oxidation are $\ce{KMnO4}$ with $\ce{H2SO4}$ and heat.


texts: In etching of mono silicon, why does the etching process around the corners differ from the etching process around the flat edges? What brings about this difference and is there some way that MEMS engineers could quantify the process around the corners?


texts: Finding the Ka of a weak acid after addition of a strong base

texts:
When 50.00 mL of an unknown 0.2461 M weak acid are titrated with 0.1968 M NaOH, it was found after the addition of exactly 16.00 mL of base that the pH of the solution was 3.79. From this information, calculate the Ka of the acid.

I have an idea of how to do this question, but looking in my book, I seem to be arriving at a wrong answer.

$$50 \text{mL of }0.2461\text{M weak acid} = 0.2461 \cdot 0.05 = 0.012305\text{ mol weak acid}$$
$$16 \text{mL of }0.1968\text{M NaOH} = 0.2461 \cdot 0.013 = 0.0031488\text{ mol NaOH}$$

$$\begin{array}{|c|cccc|}\hline
   & \ce{HA} & \ce{NaOH} & \ce{A^{-}} & \ce{H_{2}O} \\ \hline
  \mathrm I & 0.0123 & 0.0032 & 0 & -\\
  \mathrm C & -0.0032 & -0.0032 & +0.0032 & - \\
  \mathrm E & 0.0091 & 0 & 0.0032 & -\\ \hline
 \end{array}$$

$$\text{molarity } \ce{A^-} = \frac{0.0032~\textrm{mol}}{0.066~\textrm L} = 0.0485~\textrm M$$

from here, I work on the assumption that the weak conjugate base will associate in water.

$$\mathrm p\ce{OH} = 14 - \mathrm p\ce H = 14 - 3.79 = 10.21$$
$$[\ce{OH^-}] = 10^{-\mathrm p\ce{OH}} = 10^{-10.21} = 6.17\times 10^{-11}~\mathrm M$$

$$\begin{array}{|c|cccc|}\hline
   & \ce{A^-} & \ce{H_2O} & \ce{HA} & \ce{OH^-} \\ \hline
  \mathrm I & 0.0485 & - & 0 & 0\\
  \mathrm C & -6.17\times 10^{-11} & - & +6.17\times 10^{-11} & +6.17\times 10^{-11} \\
  \mathrm E & 0.0485 \text{ (negligible change)} & - & 6.17\times 10^{-11} & 6.17\times 10^{-11}\\
 \hline\end{array}$$

\begin{align}K_\mathrm {b} &= \frac{(6.17\times 10^{-11})^{2}}{0.0485} = 7.85\times 10^{-20}\\ & = \frac{K_\mathrm W}{K_\mathrm b}\\ & = \frac{1.0\times 10^{-14}}{7.85\times 10^{-20}} = 127388.54 \leftarrow\text{This is obviously wrong}\;.\end{align}

Where did I go wrong? Any help is much appreciated!


texts: How can iodine(I) cations be produced in this reaction if no additional acid is added?

texts:
In laboratory, we had to synthesize an aromatic compound and identify it. The chemical reaction involved salicylamid, $\ce{NaI}$ and $\ce{NaClO}$. The solvent is ethanol.

First, we dissolved the salicylamid with the ethanol. Then we added the NaI. When the mixture was homogeneous, we let it cool down to 0 °C. Once the mixture reached that temperature, we quickly added the NaClO.

We figured out that for the salicylamid to react, we needed an $\ce{I+}$.
Here's how we think we can obtain the $\ce{I+}$:

$$\ce{NaI -> Na+ + I-}\tag{1}$$

$$\ce{NaClO -> Na+ + ClO-}\tag{2}$$

$$\ce{ClO- + I- + 2H+ -> I+ + Cl- + H2O}\tag{3}$$

It seems to be the easiest way to obtain the $\ce{I+}$. However, isn't it impossible for the ethanol to release an $\ce{H+}$? Isn't ethanol neutral? How can the ethanol reacts with the $\ce{NaI}$ and the $\ce{NaClO}$?

PS: Sorry if the terms may not be the correct ones. English isn't my first language.

Edit: Since ethanol is only the solvent and isn't involved in the reaction, how can we obtain an $\ce{I+}$?

Is it like this?

$$\ce{2NaI + NaClO -> NaCl + Na2O + 2I+}\tag{1}$$


texts: I read that lead(II) iodide is soluble in excess KI solution due to complexation, but lead(II) cyanide does not dissolve in excess cyanide solution. This seems wrong since cyanide is a much better ligand that iodide, so shouldn't it be able to form a complex more easily?


texts: Why do single, double and triple bonds repel each other equal amounts?

texts:
I'm here to share with you something that totally confuses me, as I can't see the logic behind it, and my teacher doesn't know either.

Let's take a set of bonds that's trigonal pyramidal, with a lone pair of electrons and three bonds. The angle between the bonds is 107 degrees.

Now, the part where I get confused is if, say, we have one double and two single bonds (I know this makes the atom have 10 electrons, but just ignore that. It's not the point).

Now, in my brain, it would be logical that the double bonds, containing four electrons, would repel more than a single bond, containing just two. However, according to what I've been taught, it doesn't. What is that?


texts: How to name compounds with more than one spiro atom and cyclic compounds with more than two fused rings?

texts:
The nomenclature of the bicyclic and spiro (mono) compounds are easy to understand. But when the number of spiro atoms or the number of rings exceeds 2, the nomenclature turns very complex. I cannot understand the method of numbering the carbons and the method of writing those bracketed numbers with dots and superscripts.

I have read the IUPAC Recommendations 2004, but the text given there is really hard to understand (for me only, I hope). I want to know the method of writing those numbers with the superscripts inside the bracket for spiro and cyclo compounds. Diagrams with arrows or a detailed text with one particular example, will be helpful.


texts: Ring expansion of two fused rings to a larger ring

texts:
I saw the following reaction mechanism in paper Tetrahedron Lett. 1976, 17 (33), 2869–2872.:

I'm not able to understand the following parts:

How did the conversion of 27 to 29 take place? I've never seen that kind of a ring expansion, and a detailed explanation would help - maybe including the necessary transition state(s) and why it happens.
27 to 28 and 30 to 31 aren't clear as well; why should such rearrangements happen and how do they happen? What is the mechanism?


texts: How to estimate the number of hydrogen bridges in a bouncing ball?

texts:
We want  to make a bouncing ball: the reaction is between with polyvinyl acetate (PVAc) of wood glue and borax. It makes bridges between the molecules like DNA and hydrogen bonds.
We would like to measure the number of bridge created with an experiment, like measure the lost kinetic energy and make conclusions.
Do you have an idea of protocol, we could easy make to get the number of bridge ?


texts: Can the guanidinium ion give stable N-nitrosamines under mild metalworking conditions?

texts:
Can the guanidinium ion react with inorganic nitrite under mild basic metalworking conditions ($\mathrm{pH\ 8 - 10}$ and temperature $\lt \pu{70^\circ C}$) to give stable N-nitrosamines?

Usually, the carcinogenic nitrosamines are generated from secondary amines. But guanidinium ion is not a secondary amine. Guanidinium ion is a mesomerism-stabilized system, and the nitroso group could be also stabilized by mesomerism therefore. So I'm afraid that it can build nitrosamines readily. But is this possible under basic conditions as mentioned above?


texts:
I have just been studying the $\ce{HCl}$-$\ce{KCl}$ 'buffer', but there are still quite a few things I am uncertain about. I would appreciate any help in clearing up some questions I have.

What I understand (possibly incorrectly) from my research so far:

Water is the weak acid acting as a buffer in this system. The $\ce{HCl}$ and $\ce{KCl}$ in the system are there to increase the solution's ionic strength, which somehow improves water's buffer capacity.
In high ionic strength solutions, the 'standard' equilibrium equation has to be changed to include the activity coefficients. For water's equilibrium, as the ionic strength increases, the activity constants decrease and so the K value decreases.

If anything above is incorrect, please point out my misunderstanding. There are still a few questions I can't find answers to:

Why does the increased ionic strength of the solution improve water's buffer capacity?
Isn't a higher equilibrium constant required to make water a better buffer? Then isn't it bad that the ionic strength decreases K?
Could any other salt have been used to increase the ionic strength, or is there some specific reason $\ce{HCl}$-$\ce{KCl}$ is used?

I'm finding this 'buffer' system to be extremely confusing, so any help answering these questions would be greatly appreciated.


texts: Why can a face-centered cubic lattice not be redrawn as a body-centered tetragonal lattice?

texts: A base-centered cubic lattice can be redrawn as a primitive tetragonal lattice, therefore we do not include it in the list of Bravais lattices. Why is it then that a face-centered cubic lattice cannot be redrawn as a body-centered tetragonal lattice? If they can be redrawn as each other, why is it then that they are still listed in the Bravais lattice list? What is the ultimate condition to be in the list?


texts: Would stainless steel corrode in this electrolytic cell I designed?

texts:
As far as I know, stainless steel is resistant to corrosion due to an inert oxide layer formed by the other alloy metals. I am learning about redox reactions right now so I am no expert; but since stainless is not to be used as a anode, I am wondering why is it allowed as an cathode? Wouldn't the oxide layer be reduced, forming oxygen gas and thus exposing more of the metal and lead to corrosion?
I have also read that stainless forms hexavalent chromium when being used as a anode, so is that because it gains extra oxygen atoms due to the oxidizing process? If so, it should be okay to put it in a high oxygen environment, right?
When using a carbon anode, does it only produce carbon dioxide? And is this gas formed from ions, or is there oxygen gas present first, which later reacts with the carbon?

Here is my design, I do not care at the moment that the gases are being mixed:

I plan on using sodium acetate as a salt in a future project, it produces carbon dioxide and hydroxide ions as some of the products. Similar to question three, is oxygen gas ever produced in this reaction?

In the future I would hope to have proper equipment and materials to build a cell like this one: link
Also if any of these questions are too broad to answer please let me know, I am quite new to stackexchange. Thanks in advanced!


texts: Why do you use catalysts if they increase the rate of forwards and backwards reactions equally?

texts:
So I wanted to know why catalysts didn't affect concentration; since if they increased rate of reaction, presumably the concentration of the products would increase.

I did read online, however, that catalysts increase the rate of the forwards and backwards reactions equally; and then the concentration not changing makes sense, but there's another question now.

I thought the whole point of a catalyst was to increase the rate of reaction so you can get more of something in less time. If it increases only the rate of reaction and not concentration, the net output of the products would be the same as if you didn't use a catalyst — and in that case, what's the point of even using a catalyst?


texts: For a 1st order reaction, how do you derive the integrated rate law for a product versus time?

texts:
For a chemical reaction in which some stoichiometric quantity of arbitrary chemical $A$ decomposes into products $B$ and $C$,

$$a \ce{A} \ce{->} b \ce{B} + c \ce{C}$$

or more simply:

$$a\ce{A} \ce{->} \text{Products}$$

The depletion of substrate A at a concentration [A] can be modeled:

$$\frac{{\rm d}[\ce{A}]}{{\rm d} t} = - k[\ce{A}]^n$$

If this is a first order reaction then n = 1:

d[A] / dt = -k * [A]

This is a separable differential equation. When integrated from time 0 to time t and initial concentration [A]0 to [A]t which is the concentration at time t, the integrated form is this:

ln([A]t) = ln([A]0) - k * t

or in terms of [A]:

[A]t = [A]0 * e-k * t

This is useful if you want to know how the concentration of A as [A] changes with respect to time. But if you want the concentration of products, I think you could consider the total concentration:

[A]0 = [A]t + [P]t

Substitution into the the last equation yields a form in terms of products:

[P]t = [A]0 * (1 - e -k * t)

This kind of makes sense to me. The substrate is being exponentially depleted and the products are being exponentially produced to a maximum concentration which is [A]0. The following assumptions were made that the reverse reaction is negligible and that the reaction proceeds to completion which isn't always true. In fact, the time coordinate where these two curves intersect is actually the half-life!

If [P]t = [B]t + [C]t

Solving the equation for [B]t yields:

[B]t = [A]0 * (1 - e -k * t) - [C]t

This doesn't make sense because at the start of the experiment (time = 0),
negative concentration of [B] would be observed. Am I doing something wrong?

I have never seen integrated rate laws modeling the concentration of a single product versus time, only the depletion of reagent concentration versus time.


texts: Enantioexcess for a non-chiral molecule?

texts:
I am trying to understand this quote in a section on "Biotransformations of Organic Molecules" from a handbook I am reading:

[...] Euglena gracilis could convert acetophenone to 2-phenylethanol; however, its enantioexcess is very poor (10%) (Takahashi, 1994).
Ref.: Takahashi, H., 1994. Biotransformation of terpenoids and aromatic compounds by some microorganisms. PhD thesis. Tokushima Bunri University, pp. 1–115.

What does "enantioexcess" mean in this context? Neither of those molecules are chiral, right?  I cannot spot any asymmetric C atoms. Nor any higher order symmetries.
I looked up Wikipedia entries on both molecules and neither mention any d / l isomers.
What am I missing?


texts:
Questions

Question F-2:

I think question f1 requires one to relate $\mathrm{\psi^2}$ or. Probability density with radius but I am just in high school and have not learnt about Hamilton operator

Question F-1:
In second I think A should be 1s and B should be 3p


texts: Is this the correct equation for the mean free path?

texts:
$\lambda=\frac{KT}{\sigma p}$ is the equation given in my textbook but everywhere else I look it is different. Is it wrong? The derivation is as follows:

$$\lambda = \frac{v_{rel}}{z}$$ where $\lambda$ is the mean free path and $z$ is the collision frequency.

Since $z=\frac{\sigma v_{rel}}{KT}$ where $\sigma$ is the area where it is possible for two particles to collide.

Then substituting for $z$ gives the equation $\lambda=\frac{KT}{\sigma p}$. Have I gone wrong somewhere. I often see a factor of root two in the denominator but I don't see where that might come from.


texts: How to predict the solubility of an organic compound in different kinds of solvents?

texts:
How is it possible to know whether a particular solvent will dissolve in a particular kind of solvent, i.e. organic, polar, protic...?
Are there any indicators to look for in molecules or elements that allow one to predict what kind of solvent should be used to dissolve it?


texts:
When the spark plug of a car ignites the pressurized air/fuel mixture, could you instead send the exhaust to another system within the car to be Recycled?

I think it's a great idea that could drastically lower pollution, that is if it's possible.


texts: Temperature dependence of reaction rates

texts:
Is it correct to say that "Increasing the temperature will always increase the rate of any chemical reaction"?

Many articles on the internet and textbooks say yes but what about biochemical reactions that take place in our body?

To my knowledge  at higher temperatures some enzymes (which are catalysts in chemical reactions in the body) become less effective which in turn slows down the reaction rate.

So is it correct to say "any chemical reaction" in the statement or do I have to think of the temperature dependence of the biochemical reactions without the enzymes?


texts: Why the concentration with respect to time equation of a first-order reaction does not depend on the stoichiometric coefficient of reactant?

texts:
According to my Chemistry textbook (Chemistry by Raymond Chang 10th edition, pg 570), for a first-order reaction of the type $$\ce{A->product}$$
the rate is $$rate=-\frac{[\Delta A]}{\Delta t}$$
From the rate law we also know that $$rate=k[A]..... (13.2)$$
Combining the two equations for the rate we write $$-\frac{[\Delta A]}{\Delta t}=k[A]$$
And finally, using calculus, $$\ln\frac{[A]_t}{[A]_0}=-kt...... (13.3)$$
All of this feels okay to me. However, later on, the book uses the same equation (13.3) to solve a first-order reaction of the type $$\ce{2A->product}$$ and I don't understand why. Because the rate of reaction would now be
$$rate=-\frac12\frac{[\Delta A]}{\Delta t}$$ and equating this relation with (13.2) gives $$-\frac12\frac{[\Delta A]}{\Delta t}=k[A]$$ and finally $$\ln\frac{[A]_t}{[A]_0}=-2kt$$ I know I'm probably misunderstanding something. Please can someone explain this to me. I've been trying to figure it out for days now.

[Edit] The problem that I'm referring to is a Practice Exercise, the book only gives the problem and the answer, not the solution. However, based on the answer is obvious that equation 13.3 was used to solve it.

Problem: The reaction $\ce{2A->B}$ is first order in A with a rate constant of $\pu{2.8 \times 10^{-2}s^{-1}}$ at $\pu{80 ^{\circ}C}$. How long (in seconds) will it take for A to decrease from $\pu{0.88M}$ to $\pu{0.14M}$?

Answer: $\pu{66s}$

If equation $$\ln\frac{[A]_t}{[A]_0}=-2kt$$ were to be used, the answer would ended up being $\pu{33s}$.


texts: Which of the resonance structures is more stable?

texts:
I am quoting a rule on resonance from Organic Chemistry by T.W. Graham Solomons, Craig B. Fryhle, 12th edition, page 25.

  Structures in which all the atoms have a complete valence shell of electrons
  (i.e., the noble gas structure) are more stable.

I tried to apply to the following.

According to this rule structure 4 must be most stable. But structure 4 is not aromatic, while structure 1 is aromatic. Since aromatic species are more stable then nonaromatic species, structure 1 must be more stable.

My question is which of the structures is more stable?


texts: Copper(II) oxide is black, but when we find the percentage of oxygen in air by volume using ammonia, copper, and ammonium chloride, the color of $\ce{CuO}$ turns green. What is the reason for this?


texts: How to get $\Gamma_{vib}$ for hexafluoroethane?

texts:
An exercise asks me to find $\Gamma_{vib}$ for that molecule.
I know that: $$\Gamma_{cart}=\Gamma_{vib}+\Gamma_{translations}+\Gamma_{rot}$$

Since the molecule I'm considering belongs to the $D_{3d}$ group (in the staggered configuration), from the character table you get:
$$\Gamma_{translations}=A_{2u}+2E_{u}$$
$$\Gamma_{rot}=A_{2g}+2E_{g}$$
and then:
$$\Gamma_{vib}=\Gamma_{cart}-2E_{u}-2E_{g}-A_{2g}-A_{2u}$$
My question is: does exist a fast way to find out $\Gamma_{cart}$?

The only method that I know is to express each operation of the group in terms of matrices using the Cartesian basis, so I should write down 12 matrices 24x24, and then find out the corresponding reducible representation, but I'd take ages. I'm pretty sure that there must exist a faster method.


texts: Partial and total concentration in solutions

texts:
The total pressure of gas mixture equals the sum of partial pressures of its components.

Can this rule be true for liquid concentration?
I.e. can we say: the total concentration of mixture is equal to the sum of partial concentrations of its components?


texts: How much gas is inside a pressurised gas cylinder?

texts:
Given a 19kg Liquid Petroleum Gas (LPG) cylinder, with this specification:

LPG inside the cylinder weighs 19kg.
The internal volume of the cylinder is 44.5 litres.
The LPG is a mixture of propane gas (60%) and butane (40%).

I would like to calculate the volume of LPG contained in the cylinder. This is the volume the pressurised gas will uncompress to, if it escapes the cylinder.

I have looked at the Ideal Gas Law:

Pressure x Volume = Number of Moles x Gas constant x Temperature

But I cannot use it as I do not know about the pressure inside the cylinder and volume is the unknown I am interested in.

How do I proceed with this problem?


texts: Is the 1,4-adduct of carbonyl compounds ever a major product over the 1,2-adduct?

texts:
If, say, propenal undergoes nucleophilic addition of hydrazine, will the 1,2- adduct or the 1,4-adduct be preferred? Why?

There is an obvious reasonace structure with an electrophilic beta carbon so under proper conditions will the 1,4-adduct dominate?


texts: Is there Any Advantage to Using Multiple Steel Plates in an Electrolyzer?

texts: If I have an electrolyzer (For water) is there any advantage to having additional steel plates in between the electrodes in solution? For some reason this appears to be a popular design and I'm not sure why. I'd think that at worst the voltage would have to be slightly higher to conduct through the extra solution in a 2 electrode system.


texts: Estimate the concentration of HCl and volume of 6 M HCl required to complete precipitate each of the given salts

texts:
In our chemistry lab we performed the following experiment below.

  Given that $K_\mathrm{sp}(\ce{AgCl}) = 8.2 \times 10^{-11}$ and $K_{\mathrm{sp}}(\ce{PbCl_{2}}) = 1.7 \times 10^{-5}$

  Procedure:
  $0.2\,\mathrm{mL}$ each of $\mathrm{0.05\: M \: \ce{Ag+}}$ ions and $\mathrm{ 0.05\: M \: \ce{Pb^{2+}}}$ ions were added into a centrifuge tube. The solution was diluted to $1\,\mathrm{mL}$ $6\,\mathrm{M}$ $\ce{HCl}$ was added to the solution till it completely precipitates. The quantity of $\ce{HCl}$ required was recorded. The precipitate and supernatant were separated and kept for subsequent experiments.

  Observations: Precipitate formation was observed almost instantly. It took 6 drops of $\ce{HCl}$ to completely precipitate the contents.

  Estimate the concentration of $\ce{HCl}$ and volume of $6\,\mathrm{M}$ $\ce{HCl}$ required to complete precipitate each of the given salts.

Here is my approach:

\begin{align} c_{1}V_{1} &= c_{2}V_{2} \\
\text{Let } c_{1}=0.05\:\mathrm{M}, V_{1}&=0.2\:\mathrm{mL}, \text{and} \ V_{2}=1\:\mathrm{mL}\\
[\ce{Pb^2+}] &= 0.2 \cdot 0.05\ \mathrm{M} \\
[\ce{Ag+}] &= 0.2 \cdot 0.05\ \mathrm{M}\\
K_{\mathrm{sp}}\:(\ce{AgCl}) &= [\ce{Ag+}] [\ce{Cl-}] \\
8.2 \times 10^{-11} &= 0.2 \cdot 0.05\ \mathrm{M} \cdot s_{1} \\
s_{1} &= 8.2 \times 10^{-9}\ \mathrm{M}\\
K_{\mathrm{sp}}\:(\ce{PbCl_{2}}) &= [\ce{Pb^{2+}}] [\ce{Cl-}]^{2}\\
1.7 \times 10^{-5} &= 0.2 \cdot 0.05\ \mathrm{M} \cdot (s_{2})^2\\
s_{2} &= 0.041\ \mathrm{M} \end{align}

Thus to precipitate $\ce{AgCl}$ and $\ce{PbCl_{2}}$ completely, the concentration of chloride ions in solution must exceed $8.2 \times 10^{-9}$ M and $0.041$ M respectively).

I am not sure of my computations up till this point, and I need some help on how to proceed further.

EDIT: My calculations  tell me that volume of $6\,\mathrm{M}\,\ce{HCl}$ necessary is $0.00683\,\mathrm{mL}$. In the lab we have estimated the volume of one drop of our pipette as $0.037\,\mathrm{mL}$, based on this I calculated that the number of drops of hydrochloric acid necessary to complete precipitation is $0.18$ drops. But in the actual experiment I performed 6 drops of $\ce{HCl}$ were dispensed and based on the computations we did, everything should have precipitated. But after centrifugation and separation the supernatant still had lead ions which were precipitated as lead chromate. Why is this so? (This is the main reason why I suspected my calculations and turned to this website for help).

EDIT2: I now see the flaw in my computations. what I have calculated is in fact that amount of HCl necessary to start precipitation. Thanks to everyone for their help.


texts: Help with determining the rate constant of a reaction

texts:
The question asked was,

The initial concentration of $\ce{N2O5}$ in the first order reaction $$\ce{N2O5 -> 2NO2 + 1/2O2}$$ is $1.24\cdot 10^{-2}~\mathrm{mol\,L^{-1}}$ at 318K.
The concentration of $\ce{N2O5}$ decreases to $0.20\cdot 10^{-2}~\mathrm{mol\,L^{-1}}$ after 1 hour.
Calculate the rate constant at this temperature.

How i attempted to solve this is as follows:-
The answer given, however, is $4.82 \times 10^{-4}\ \mathrm{s{-1}}$. What have I understood incorrectly?


texts: Is it possible to dissolve Raspberry ketone in warm water?

texts: I poured a small amount of RK in cold water and it clumped together so I warmed it in the microwave and it disappeared in the water meaning it dissolved, but i was under the assumption that RK is insoluble in water, so what happened ?


texts:
Is $\ce{HgI_2}$ polar or non-polar?

The electronegativity difference between Hg and I is about 0.66, so the compound should be almost covalent. However, I cannot find the structure of $\ce{HgI_2}$ as a single molecule, so, I cannot find if it is polar or not, as a whole.


texts: I want to know the mechanism of this reaction. My intuition says $\ce{H-}$ will attack on $\ce{C}$ attached to $\ce{N}$ and hydrolysis afterwards would produce $\ce{-NH-OH}$. But the answer says that the amine will be formed.


texts: Thermodynamics of a spontaneous isothermal chemical reaction.

texts:
Which of the following is/are correct for spontaneous isothermal
  chemical reaction?

  (A) $\Delta H = 0$,  because $\Delta T = 0$

  (B) $\Delta S = 0$

  (C) $\Delta U = 0$,  because $\Delta T = 0$

  (D) $\Delta G < 0$

My answer: $\mathrm{A, C, D}$

Reasoning:

$U$ is a state function and only depends on the initial and final states and their temperature. Since $\Delta T = 0$, $\Delta U = 0$

$\Delta H = \Delta U + \Delta(PV)$, but $PV = \text{constant}$, so $\Delta H = 0$

$\Delta G <0$ - the requirement for any reaction to be spontaneous.

But answer given is only option D.

I think the flaw in my $\Delta H = 0$  argument is that reactants can be solids and liquids as well and we cannot apply $PV = \text{constant}$ to them. Am I right?

But I  still can't figure out why $\mathrm C$ is wrong.


texts: why lawrencium is placed in f-block elements although its last electron enters in 6d-subshell?

texts:
The electronic configuration of lawrencium ($\ce{Lr}$) is $\mathrm{[Rn] 7s^2 5f^{14} 6d^1}$. As its last electron enters the $\mathrm{6d}$ sub shell, it should be a part of $\mathrm{d}$-block elements, but in the periodic table it is given as a part of $\mathrm{f}$-block elements. Why?

I noticed that if we place lawrencium in $\mathrm{d}$-block elements the symmetry and similarity in properties of many elements will be broken. Is that the reason to place it like this? Or something else? Is lawrencium an exception? How? Please explain.


texts: Electroplating: What exactly does an additive/ brightener do in the electrolyte?

texts:
A carrier or supressor is generally a poly-oxyalkyl compound that is instrumental in suppressing the electrolytic current. This is achieved by the formation of a diffusion layer when the additives surround around the cathode.
An additive or brightener on the other hand is generally disulphide compounds that increases the current and reduces suppression.
Could anyone please explain the mechanism of this? Is it possible that the disulphide compound is breaking the polymeric chain of the carrier?


texts: Estimation of pressure and kinetic energy density of stellar interior using kinetic theory of gases

texts:
In Physical Chemistry we are working a problem that is confusing. We started by calculating the pressure half way to the centre of the sun assuming that the interior consisted of ionized hydrogen atoms. We determined this to be $\pu{3.59e6 kPa}$. However, the third part of the question asks:

  What is the kinetic-energy density half way to the centre of the Sun? Compare with the (translational) kinetic energy density of Earth's atmosphere.

Can someone expand on what kinetic energy density is, if it is different from kinetic energy, and what the formula is. I might just be overthinking the problem.


texts: How do I overlay spectra in an ACD/NMR Processor, version 12.01?

texts: I am having great difficulty getting spectra to overlay (the option doesn't even appear) after setting to new window mode and selecting each spectrum.


texts: Analytical solution of the Schrödinger Equation for AB^+ systems

texts:
According to Wikipedia, there are not many problems for which the Schrödinger equation can be solved analytically. [1] The $\ce{H2+}$ ion is probably the most complex molecule that can be treated this way.

As far as I know, every diatomic homonuclear system like this can be solved, e.g., $\ce{U2+}$.

Up to this point the molecules always consisted of two equal atoms which makes me curious about the following:

Is the Schrödinger equation not only solvable analytically for diatomic homonuclear systems $\ce{A2+}$ but also for diatomic heteronuclear systems like $\ce{AB+}$?


texts: How does the reaction Mg + O₂ → MgO occur?

texts:
$\ce{Mg + O2 → MgO}$

Magnesium, oxygen and magnesium oxide form the above equation.

How?
What do I need to learn to do this? atomic numbers/ valencies?


texts: How is the triferric tetroxide of iron possible?

texts: If oxygen has a valency of $-2$, $4$ of it would result in $-8$. But iron doesn't have a (variable) valency of anything that goes to $-8$. Then how is $\ce{Fe3O4}$ possible?


texts: Mechanism and type of polymerization of chloroethene

texts:
Ethene reacts with hydrogen chloride to form a monomer used in the production of a polymer. This monomer is chloroethene.

My questions are:

(1) How is the polymer formed from the monomer?

and

(2) Is this an addition or a condensation polymerization?


texts:
Consider the dehydration of the following molecule with conc. $\ce{H2SO4}$ at $443 \text K$:

The possible products are:

The first one is the Zaitsev product and the second one Hofmann  product.
Which compound is the major product?
There are 2 factors to consider here:

Zaitsev product is more stable than Hofmann product due to
hyperconjugation
Anti elimination is more favorable than syn elimination due to steric requirements

Obviously both the factors clash with each other, so I couldn't come to a definite conclusion. Can you help me out?


texts:
There is another question on the site which is:

  Two containers, A and B, connected by a closed valve were evacuated and the Chlorine gas (Cl2) with a pressure of 200kPa was put into A and Oxygen (O2) with a pressure of 150kPa into B. a)If Container A has a volume of 10L and container B has a volume of 5L, find the total pressure within the system if the valve were opened and the gases allowed to mix b)Which of the gases would diffuse through the valve at a faster rate?

It has been a long time since I took chemistry and blundering around with Google didn't really seem to answer my question about a technical point about question (b) for this problem.

Obviously when you first open the valve between containers A and B the pressure is going to equalize. Since A has a higher pressure, gas will flow from A into B. Is this diffusion?

In a weird way the pressure equalization does fit the basic notion of diffusion - molecules mover from an area of higher concentration to an area of lower concentration. Thus if both containers had oxygen, then container A would be more concentrated (e.g mol $\rm L^{-1}$) since it has a higher pressure. Thus the molecules will move from A to B because there is a lower "concentration." However this doesn't really seem to fit my notion of either  diffusion or effusion. So is there a better proper term for this or is the phrase "pressure equalization" about as good as can be done? Or am I just wrong?

Obviously after the pressures equalize, then the oxygen from the oxygen/chlorine mixture will diffuse into the chlorine faster since oxygen molecules have a lower mass.

The gist is that the question would be simple to answer if containers A and B had the same pressure. But the difference in pressure seems to make the question turn on a very exacting definition of diffusion.


texts: Why does a 1:1 mixture of Polyvinyl Alcohol (PVA):H2O decompose/carbonize during heating?

texts:
I bought a powder of Polyvinyl Alcohol (PVA from Sigma Aldrich). I mixed the powder with water in a mixture 1:1 to place a droplet on a hot plate. To figure out the melting temperature of the PVA, I heated it, meanwhile the water should be evaporated. According to Wikipedia or other chemical databases, partially hydrolysed grades of PVA melt between $150-180\ ^\circ C$
.

My questions:

Why did my mixture decomposed/carbonized above $120\ ^\circ C$
(its color changed from transparent to brown, so I guess it decomposed)?
The mixture did not melt between $150-180\ ^\circ C$
. Why?
Did I make any general mistake at all?


texts: In a hydrogen fuel cell stack, is pure oxygen required?

texts: I have been researching making a hydrogen fuel cell to produce electricity. However, since pure oxygen is expensive, is pure oxygen needed for the dry fuel cell stack or can the oxygen in the air be used.


texts:
I am told that because of the poor overlap between a chlorine atom and a carbon atom and chlorine's relatively high electronegativity, there is a strong partial positive character on the central carbon in an acyl chloride molecule.

This makes sense. I am then told that because of this high partial positive character created through the inductive effect of chlorine and oxygen and the poor overlap between chlorine and oxygen, the oxygen's lone pair(s) actually participate in a sort of resonance with the central carbon, thereby giving the C=O bond in an acyl chloride partial triple bond character.

Is this true? Also what exactly is this called? Backbonding?


texts: Conformation of six-membered ring constituting a bridged compound

texts:
What is the conformation of the cyclohexane ring constituting [2.2.1]-bicycloheptane?
Is it boat or twisted boat? Is that conformation abundant in other bicyclic systems containing a cyclohexane ring?

EDIT: From Modern Organic Synthesis by Zweifel I took the following image:

which is in contradiction with current answers. Can anyone account for this observation?


texts: Does molarity change if you decrease volume?

texts:
For example if the solute of the solution contains $\pu{0.5 mol}$ and the total volume is $\pu{0.5 L}$, the molarity would be $\pu{1M}$. But if I take a portion of that solution, let's say $\pu{0.1 L}$, would that molarity be still $\pu{1M}$? If it were that way, the solute would be $\pu{0.1 mol}$ too.

Or, do the moles of the solute stay the same $\pu{0.5 moles}$ and the molarity would change to $\pu{5M}$?

So my question is, does the solute decrease when the volume decreases too?


texts: The meso-form of tartaric acid is optically inactive due to the plane of symmetry. But how are these forms able to show optical activity when the σ-bonds can freely rotate, which can change the configuration of the atoms?


texts:
From a biological system, I got the following reaction:

$$A+B+D\rightarrow C+C_1D$$ ($C_1D$ is a certain complex)

However, if at any given time there are no $D$s to react, and only then, instead the following reaction does happen (until a new $D$ appears, at which point the first reaction switches in instead):

$$A+B\rightarrow C+C_2$$

So, the second reaction happens if and only if there are no $D$s.

Therefore, this system is like a "conditional" system, where under existence of $D$ the first reaction happens, until all $D$s are used, and then . At any given time, more $D$s can appear and then the whole reaction system acts again as described above.

In the above system, what are the kinetic equations?

(Note: of course, this is not the complete reaction scheme, but the minimum one to extract equations for. However, it should be noted that I consider $[D]=g(t)$, i.e. not constant equal to the initial concentration of $D$. Of course $g(t)$ also depends on the aforementioned reactions too, but on others also)


texts: Why is it not possible to determine the rate constant this way?

texts:
The following equation can be used to determine the rate:
$Rate = \frac{-\Delta [A]}{\Delta t}$

This equation can also be used:
$Rate = k[A]$

By simple substitution, $\frac{-\Delta [A]}{\Delta t} = k[A]$ should be true. Therefore, $k$ can be represented as:
$\frac{-\Delta [A]}{[A]\Delta t}$

However, calculating the rate constant for a given reaction is obviously not that simple. Why does this equation not work then, if the mathematics of it check out? I have tried using this equation for some problems, and as I expected, they do not yield the correct answer as opposed to using the integrated rate equation.


texts: Can I replace potassium nitrate with sodium nitrate in a smoke bomb?

texts:
A very famous experiment goes like this:

$\ce{KNO3}$, molten wax and sugar are mixed and later burnt; the resulting mixture produces quite a lot of smoke.

After hearing about the experiment, I threw in the idea, "What would happen if $\ce{NaNO3}$, or other alkaline compounds were used instead?". However, the teacher wants us to be sure that the building doesn't explode. So here I am. Has this experiment been attempted before? What would happen if it was used?

Here is a link with the smoke bomb experiment.


texts: Can the electronegativity of metals be changed by applying an electric potential?


texts:
Suppose a carbanion is involved in resonance and thus its electrons conjugate with unhybridised p orbital
of the nearby sp2 hybridised carbon and a pi bond is formed. Since carbanions are sp3 hybridised, how would it form a pi bond or will the hybridisation of the carbon change?


texts: Why do transition metals form particularly stable complexes?

texts:
The pre-transition metal ions can form complexes but the ligands are weakly bound unless they are multidentate and thus benefit from the chelate effect. For example, crown ethers and cryptands.

However, transition metal ions can form a vast array of stable of stable complexes with monodentate and multidentate ligands. Why is there such a difference between the pre transition elements and the transition metals in this respect.

My initial thoughts are that the transition metal ions will have a higher charge and smaller radius so the electrostatic attraction is larger. I also thought about the d-orbitals but the pre transition elements have d orbitals available, they're just not filled. As a result, is increased stability related to exchange energy or perhaps the lower energy d orbitals? Are there any more factors? Are my suggestions valid?


texts: Is hydronium an electrophile, nucleophile, both or neither?

texts:
Is hydronium an electrophile or a nucleophile? I expected $\ce{H3O+}$ to be a nucleophile due to the presence of electrons in the $\ce{2p}$ orbitals of $\ce{O}$. But the answer key of the test states that its none of them.

I can rationalise it this way: If $\ce{O}$ donates its 2 electrons then there would be 2 positive charges on $\ce{O}$ leading to instability.

But I am not too sure of my reasoning either. Isn't hydronium serving as a nucleophile in its reaction with $\ce{OH-}$ ? Why is it then neither an electrophile nor a nucleophile?

Google books results show that its mentioned as an electrophile in some books. While there's disagreement on other sides on the internet?  What's the true classification?


texts: How will my studies in mathematical statistics be applied to and assist me with problems in chemistry?

texts:
I'm currently working towards a major in both chemistry and mathematical statistics as a part of my science degree, and I got to wondering:

How will these two go hand in hand and help each other?

Now, I know there's the obvious applications of statistical inference to any experimentation I do, but I'm talking about less obvious relationships. Could my knowledge of solving SDEs ever help me with my experiments? What about continuous Markov processes? Will I ever even think about a discrete random variable again if I go on to get a PhD in chemistry? Also not looking for the standard "well we use statistical physics to model electrons" example, either (welp, unless you can offer some nice specifics). Surely there's other ways that these skills I've found can interact with each other?


texts: How do I do stoichiometry for 2 limiting reactants

texts:
The Drano reaction produces sodium aluminate along with hydrogen gas. If a typical container of Drano weighs 500 g which is 35% by weight by weight sodium (l) hydroxide and 2.5% by weight aluminum, what volume hydrogen gas would be produced if (excess) water was added to an entire can of crystal Drano at 22 °C and 1.2 atm?

My equation:

$$\ce{4 Al + 4 Na(OH) + 12 H2O -> 4 Na[Al(OH)4] + 6 H2}$$

If my balancing correct, I am trying to get the excess for water. Would I need to do the moles left over? Or would 500 x 62.5% (2.5% and 35% added together) suffice?

If I do need to do moles left over, how do I manage with two limiting reactants?


texts: Is sulfide ion a stronger base than hydroxide ion?

texts:
I received these three responses. They are all, except the last response, incorrect to varying degrees. I am, however, unsure about how to grade these responses because the question itself, in my opinion, misleads the students by saying that both have the same pH and to use this information to determine the strength of the bases. Their responses also raised a few questions of my own. What are your opinions?

Question
It is an experimental fact that the pH of 1 M $\ce{Na2S}$ is essentially the same as the pH of 1 M $\ce{NaOH}$. Based on this information, is $\ce{S^{2-}}$ or $\ce{HO-}$ the stronger Bronsted-Lowry base? How can you tell?

Student 1's response:

A base's strength is measured by how much it can increase the hydroxide ion concentration in a solvent relative to its own initial concentration.
Given that both the 1 M $\ce{Na2S}$ and 1M $\ce{NaOH}$ solutions have the same pH, they both have the same $\ce{[H3O+]}$ concentration and therefore the same $\ce{[HO^{-}]}$ concentration. Therefore, the two bases are the same strength as each creates a $\ce{[HO^{-}]}$ concentration equal to their initial molarities in water.

I think this response could be improved if the student mentioned the leveling effect and recognized how all bases stronger than hydroxide ion are "leveled." It's just like the high striker game at the fair; you can hit it hard enough to make the puck go all the way to the top, and so can someone else, but that doesn't necessarily mean you guys are equal in strength; it just means that the device quantifying strength doesn't differentiate between "strong" and "super strong."
Student 2's response

$\ce{S^{2-} + H2O ->HS- + HO-}$
From this equation and the problem statement, it is clear that $\ce{S^{2-}}$ hydrolyzes water to create a hydroxide ion concentration in water equal to its own initial molarity. Hydroxide ion isn't hydrolyzing water to create hydroxide; the below equation is non-sensical. Therefore, sulfide ion is the stronger base.
$\ce{HO^{-} + H2O ->H2O + HO-}$

Is the second equation really non-sensical?
Student 3's response:

The stronger base has the weaker conjugate acid.
Sulfide ion's conjugate acid is $\ce{HS-}$.
Hydroxide ion's conjugate acid is $\ce{H2O}$.
From the $\ce{K_{a}}$ table in the beginning of the lab manual, one knows that $\ce{HS-}$ is a weaker acid than $\ce{H2O}$. Therefore, sulfide is the stronger base.


texts: Mechanism for Chromyl Chloride Formation

texts:
This is the very famous chromyl chloride test, used for detection of chloride ion in solution -

$$\ce{K2Cr2O7 + 4NaCl + 6H2SO4 -> 2CrO2Cl2 + 2KHSO4 + 4NaHSO4 +3H2O}$$

When a mixture containing chloride ion is heated with potassium dichromate and concentrated sulphuric acid, deep orange-red fumes of chromyl chloride are formed. My question is, how?

I want to know the proper mechanism for this reaction, particularly for chromyl chloride formation. I couldn't find it in several texts (and online), such as JD Lee and Atkins.

Also, if instead of chloride ion, bromide ion (or iodide) is used then 'chromyl bromide' is not formed. Instead, bromine gas is liberated, and chromium (III) sulphate is formed along with potassium (I) sulphate. Why? What is so special about the chloride ion?


texts: Charge density is the amount of charge per unit volume but what is charge?

texts: I was studying about x ray crystallography and my book says that charge density is measured in electrons per nano-meter cubed and this means that charge is the amount of electrons. But i am not sure if this definition (charge density = the number of electrons in a unit volume) applies when we are studying crystallography only. So to make sure, is charge simply the amount of electrons ?


texts: Etymology of saturation degrees (-ane, -ene, -yne) in aliphatic compounds

texts:
I like to know where the names for saturated, unsaturated double, and unsaturated triple bonded aliphatic compounds came from.

What is the reason/etymology behind the suffix -ane, -ene, and -yne?

I suppose it parallels something like the inflection-based umlauts in Germanic languages (which may be seen rudimentary in modern English for example in words like mouse/mice) but that is utter speculation. Yet I did not find anything in the web (I think some good extensive Chemical Etymological Encyclopaedia is really missing).


texts: Calculating the ph of an unknown solution by measuring the precipitate

texts:
You have an unknown metal hydroxide, but no meters or indicators. You have lead (II) nitrate, which is soluble in it, and lead (II) hydroxide that is insoluble in it. You take one liter of the unknown substance and add lead (II) nitrate, causing the formation of a precipitate. You add more lead (II) nitrate until the precipitate stops forming, and then add a little more. After you filter and dry the precipitate, you have 3.81 grams of it. What was the approximate ph of the original solution?

I know that the metal hydroxide would be a base, but I’m having a hard time figuring out anything else about this problem. My first thought was to figure out the molar mass of the precipitate to try and determine how much lead nitrate was added to the unknown substance, but I can’t figure that out if I don’t know what the precipitate is composed of. I thought about figuring out the molarity of the total solution to figure out how much lead nitrate was added, but again I couldn’t see a way to do it without more information.

I also thought, since we’re working with pH, we’re supposed to do something with dilution and changing powers, but I don’t see any way to do it.

This problem has me completely stuck. I just don’t see where to start. Any help would be greatly appreciated.


texts: Can grignard reagents react with any electrophillic sites?

texts: Yeah I am confused about the above question. Like since textbooks always say how C atom bonded to Mg is very nucleophillic, I was wondering why it does not bond with carbon atom that is single bonded (not the one in carbonyl part) to one of the oxygen atom of ester? Since O atom is more electronegative than C atom, C atom is electrophillic, so shouldn’t grignard reagent also bond with that C atom instead of one double bonded to the other O atom. I always see example where GR reagent attack the carbonyl carbon atom so I was wondering why? Thanks.


texts: How do chemists find a procedure to produce a given substance?

texts:
How do they find out exactly what reactions they can use to produce some substance they want to produce? Is there some reaction database that helps them find a way to make the target substance out of available chemicals?

For example, let's say they want to produce ethanol. There are multiple ways to do this: they could use the fact that yeast can transform sugars into ethanol and carbon dioxyde and use distillation to produce concentrated ethanol, or use ethylene hydration to get the same thing.

The question is: how could they find those ways? How do they know what will be produced by a given reaction, or inversely, what reaction will yield a given substance? Some reactions are well known and were just observed and studied, but what about the obscure ones?

Thanks.


texts: What is the Iso electric point of the given amino acid?

texts: I am not sure about three but for two acidic parts we take the mean of the two..  But what about three?


texts: Imagine I have a bottle with a random quantity of molecular hydrogen, and can apply exactly enough energy to break only one molecule of hydrogen. Is the reaction going to occur or the energy would be shared between other molecules in the bottle?


texts: Why do nanoparticles have a different color than their macro counterparts?

texts:
It astonished me when I learned that at nanoscale, gold is no longer "gold",rather it's red. Other elements' nanoparticles also have a different color than their macro counterparts.

Why does this phenomenon occur?


texts: Why does magnesium form covalent bonds with carbon?

texts:
According to my professor, magnesium and lithium form covalent bonds with carbon but calcium does not. He did not elaborate.

Why is this so? The electronegativities are:

Mg — 1.31
Li — 0.98
Ca — 1
C — 2.55

So a $\ce{C-Mg}$ bond would have an electronegativity difference of 1.24 and a $\ce{C-Li}$ bond would have an electronegativity difference of 1.57. Both are considered covalent. So how come a $\ce{C-Ca}$ bond wouldn't be covalent? There exists an electronegativity difference of 1.55 — comparable to the difference in the $\ce{C-Li}$ bond.

I know that Mg likes to be tetra-coordinated (Grignards) but I don't think this has much to do with this discussion. So, what makes Mg and Li special compared to Ca?

Summary of possible explanations others have come up with

$\ce{Mg^2+}$ has an ionic radius 72 pm, $\ce{Ca^2+}$ has an ionic radius of 100 pm, and for $\ce{Li+}$, it's 76 pm. So perhaps the greater charge density of $\ce{Mg^2+}$ and $\ce{Li+}$ allow them to pull electrons toward themselves a bit more, thus making the bond more covalent in character? That being said, $\ce{Li+}$ has a single positive charge while $\ce{Ca^2+}$ has a double positive charge, and I haven't calculated the actual charge densities for any of these ions so I don't think we can come to a definitive conclusion here.

http://www.wiredchemist.com/chemistry/data/metallic-radii


texts:
My teacher insists that we can push electrons either from a bond to an atom's valence, or vice versa. Bond to lone pair; lone pair to bond, he insists.

However, what about bond to bond?

Is there a pedagogical reason he might be avoiding bond-to-bond movement? This is a legal move.

Or does he simply not see bond-to-bond movement as a separate entity; could bond-to-bond electron pushing be construed as simply a bond to lone pair and lone pair to new bond move?


texts: Why is the 2nd ionization energy of chloride similar to that of sulfur?

texts: The first ionization energy of chloride is significantly greater than that of sulfur. I suggest that this is very expected as the effective nuclear charge of chloride is higher and additionally, sulfur has even more electron-electron repulsion due to advent of paired electrons in 2p orbitals. However I am not too sure on why the 2nd ionization energies are almost the same.


texts: How is the acidic dissociation of acetic acid thermodynamically feasible?

texts:
For a reaction between an acid and a base

$$\ce{A1 + B1 <=> A2 + B2}$$

to be spontaneous $\ce{A1}$ must be a stronger acid than $\ce{A2}$.
With this in mind, how can this reaction  be understood in terms of spontaneity
    $$\ce{CH3COOH + H2O <=> CH3COO- + H3O+}$$
Also sources on the internet say that $\ce{pK_a}$ of $\ce{H3O+}$ is $-1.74$ while that of acetic acid is $4.74$.


texts: Quantum particles are never objects but are always waves. But do they have mass or can they carry mass?


texts: Can reaction of gastric acid with swallowed things be dangerously exothermic?

texts:
Okay, okay. I know that swallowing a large enough amount of any substance would be considered dangerous. That isn't the point of this question, however.

As you probably know, the stomach has hydrochloric acid in it to help digest food, and kill off some microorganisms. I suspect the swallowing aluminum foil (or a decent-sized ingot if aluminum) would be dangerous, because it reacts with hydrochloric acid exothermically to form aluminum chloride and hydrogen gas.

$$\ce{2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)}$$

Here is a video of aluminum's exothermic and vigorous reaction with hydrochloric acid:
https://youtu.be/LaaORZ0ofCY?t=1m12s

Now imagine that going on inside your stomach. I believe that the hydrogen gas may be able to escape through the mouth, but the intense heat might evaporate water (thus creating more gas that must escape), and would burn and kill cells inside the stomach. Plus, there's always the possibility that the hydrogen gas that is escaping could ignite, and burn through the mouth (where it escaped from) and into the body.

So why isn't everyone worried about accidentally swallowing aluminum foil? Wouldn't it be considered very dangerous to do so? Is there something I'm missing or otherwise not thinking of?


texts: What is the difference between a positive and negative electron orbital?

texts: Why are do some electron orbitals have a negative number in the subscript (i.e. f-1), some a positive (f1), and some have a 0 (f0)? What do these numbers tell you about the atom? I know that these orbitals have different shapes, but I was wondering if they had any other effect on the atom/ion and if there was a reason that they were put in the order that they are in now.


texts:
I came across this molecule on wikipedia, and all that was written about it was two words: Docosanasaccharide and polyfuranoside.

https://en.wikipedia.org/wiki/Chemical_glycosylation#Notable_synthetic_products


texts: Brown particles in electrolysis of brine

texts:
This is not a duplicate... pls read the whole question....

I am attempting electrolysis of brine  (tap water + table salt). I am using HB pencil lead (graphite) as my two electrodes. I am using 12 volt- 1.5 amp DC power supply (using an adapter from the wall).
The solution is getting slightly alkaline (~8 pH) and hydrogen is confirmed by pop sound.

However, the whole solution is getting filled with some brown particles (resembling Dirt). If by chance my alligator clips get submerged, the get a brown coating (which I am able to wash it off).

What are this brown particles?

I have a few theories:
1. Pencil lead also contains clay.
2. Something with the water (though it is filtered)

I had attempted this earlier (~3y) and had a similar but a more dramatic result.
Then I used iron/steel electrodes and they became completely brown. The plastic container I used also became completely brown coated. I was unable to wash it off.


texts:
Is $\ce{CF_3+}$ more stable than $\ce{CH_3+}$?

In $\ce{CF_3+}$, there is $\ce{C-F}$ back bonding that increases  stability of the carbocations. But -I effect of $\ce{F}$ dominates +R effect and this decreases the carbocation stability. How can I compare these two competing effects to find the more stable carbocation?

Also, is $\ce{CF_3+}$ more stable than $\ce{CH3-CH+-CH_3}$ and tert-butyl carbocation?


texts: Need an explanation for how they got this compound name out of this structure

texts: My professor posted this question as practice in naming compounds and provided the answer. I have stared at this for 30 minutes and cannot seem to figure out how he got this name out of it... Can someone please explain.


texts: Isothermal process gives V = A(T)exp(-KP)?

texts:
Substance with isothermal compressibility K, where $\mathrm{K = -\frac{1}V(∂V/∂P)_T}$
undergoes constant isothermal, mechanically reversible process from state ($P_1$, $V_1$) to ($P_2$, $V_1$) where V is molar volume.

(a) Starting with the definition of K, show that the path of the process is described by: $\mathrm{V = A(T)e^{-KP}}$

I don't know how to get A in terms of T, the furthest I can get is $\mathrm{A = V_1e^{KP_1}}$


texts: Determination of major product in crossed aldol condensation

texts:
The title speaks for itself really.

I know that if we have a conventional ketone (with 3+ α-hydrogens) and an aldehyde with less than or equal to 3 α-hydrogens, the ketone acts as the nucleophile and attacks the aldehyde, which consequently forms the major product.

Let us take an example of a case where we have acetophenone and acetaldehyde. Both have 3 α-hydrogens. Also, the acetophenone is sterically hindered due to the phenyl group. Which is the major product here?


texts: My wife bought me a special cup for me to drink beer out of.  The problem is that, if I pour any beer in it, it goes crazy with foam.  I will get just a few ounces of beer in there and the rest of the 16 ounce cup will be full of foam.  The cup is hand spun from clay.  The texture is still pretty rough.  So, if there is any glazing, it is not really noticeable.  The cup also has little brown specks in it here and there.  Does anyone know the reaction that is taking place to produce all this foam?  Is there a way to fix it?  Let me know if I need to supply any more details.  You should assume you are talking to someone whose last chemistry class was high school.


texts: Decomposition of total Interaction energy with SAPT or EDA-NOCV

texts: I want to perform energy decomposition analysis for some Hydrogen bonded complexes. I came to know that ORCA and Psi4 allows EDA-NOCV an SAPT(0,2,3) respectively. But I do not know which one would be better, and how to perform them.


texts: Dissociation of H3PO4 and colligative properties

texts:
Which of the following solutions that have concentrations of $0.01\ \mathrm{M}$ show the highest elevation in boiling point and why?
A) $\ce{NaCl}$
B) $\ce{CaCl2}$
C) $\ce{H3PO4 }$
D) $\ce{C6H12O6}$ (glucose)

When dissolved in water, $\ce{H3PO4 }$ dissociates into 4 ions, which is more than any of the other compounds. Someone told me though, that because it's a weak-acid, it doesn't matter how many ions it has, and that $\ce{CaCl2}$ will still have the highest elevation boiling point. Is this true?


texts: How can I find the emf of a cell given the individual reduction and oxidation reactions and their respective potentials?

texts:
If I am given the individual oxidation and reduction half-equations, how can I find the emf of the combination? For example:

$$
\begin{align}
E^\circ(\ce{Fe^3+}/\ce{Fe^2+}) &= \pu{0.77 V}\\
E^\circ(\ce{Fe^2+}/\ce{Fe^0}) &= \pu{-0.44V}
\end{align}
$$

How can I find the emf of this redox pair, i.e. $E^\circ(\ce{Fe^3+}/\ce{Fe^0})?$


texts: Why is this named 3-phenyl-2-butanol instead of 2-phenyl-3-butanol?

texts: Why is the following compound named 3-phenyl-2-butanol and not 2-phenyl-3-butanol? Does the alcohol or the phenyl group have priority?


texts:
From an article by Frye et al. [1]:

Reduced glutathione (GSH) is the major intracellular redox buffer and is essential in free radical scavenging, redox homeostasis, maintenance of protein redox conformation and regulation of redox sensitive enzyme activity.

What is "maintenance of protein redox conformation"? Is it just fancy phrasing for "keeping proteins properly reduced, but not too much reduced, and properly oxidized, but not too much oxidized?
Reference

Frye, R. E.; Rossignol, D.; Scahill, L.; McDougle, C. J.; Huberman, H.; Quadros, E. V. Treatment of Folate Metabolism Abnormalities in Autism Spectrum Disorder. Seminars in Pediatric Neurology 2020, 100835. DOI: 10.1016/j.spen.2020.100835.


texts: Reaction of bicyclic diol with periodic acid

texts:
I'm in an organic 1 class, and we learned about using periodic acid (HIO4) to cleave a glycol into two carbonyl groups, oxidizing the glycol. However, in the given reaction (see picture below), I'm skeptical that an oxidation as presented in our textbook (Organic Chemistry 6th Ed., Brown, Foote, Iverson, Anslyn) actually occurs. The mechanism presented in the textbook is analogous to the first step followed by the step labeled (A). This produces a ring with nine carbons and two carbonyl groups, which to me seems rather unlikely due to angle strain. The step labeled (B) seems like a more likely follow up to the first step, where a ring shift creates a spiro shaped bicyclopentane with a single carbonyl group.

Then again, with option (C), which ignores that first step, a Pinacol Rearrangement could occur, giving the same product as (B).

Which of these is most likely? I would think that B or C would be the mechanism since the final product seems much more stable. Normally we assume reactions are done in water unless told otherwise, so I don't see any reason why C couldn't also work.


texts: Can the Lewis dot structure of SO2 be experimentally verified?

texts:
I have just watched 2 different videos on the Lewis dot structure of sulfur dioxide, $\ce{SO2}$. One says it is

$$\ce{O=S=O}$$

and the other says

$$\ce{^-O-S^+=O <-> O=S^+-O-}$$

The first paper acknowledges the second structure and says they are both right. Isn't there some way of experimentally determining the bond length, or the bond energies etc to tell which is the true structure?


texts:
For context, I am planning to try and use this sample to make a ceramic glaze.
I recently collected a sample of what I think is lawsonite, which has the chemical formula $\ce{CaAl_2Si_2O7(OH)_2*H_2O}$. After collecting it I calcined it in an electric (oxidation) kiln to around 2016 °F. Assuming that what I collected is indeed lawsonite, what happened to it? I'm assuming that all the water "evaporated", leaving some combination of $\ce{CaO},\,\ce{Al_2O_3},$ and $\ce{SiO_2}$.


texts: Gallium-induced structural failure of aluminium

texts:
I have seen youtube videos of people treating some aluminium object with liquid gallium and after letting it sit for a while, they are able to break up the aluminium into tiny little pieces with their bare hands.

Can someone tell me what is exactly going? I haven't been able to find a satisfactory explanation as of yet.

Does the gallium somehow incorporate itself into the metal lattice, disrupting the bonds? or is it forming an amalgam of sorts and actually dissolving the aluminium?

Is it a combination of these two, or are my ideas off completely? Also, what would be the exact mechanics of a process like this?

EDIT: How exactly does gallium "unzip" the grain boundaries?
 Also, besides Ga or Hg, what other metals would produce a similar effect? What mechanism/property allows them to behave in such a manner?


texts: Catalytic hydrogenation of polycyclic hydrocarbons

texts:
Recently I came across a question-

The compound on the left undergoes catalytic hydrogenation to yield A(not B, according to the answer). My knowledge is limited to the stereospecificity of catalytic hydrogenation, and I don't know if it's regioselective as well or not. Why do we get A as a product and not B? There are 3 moles of hydrogen provided, so how to decide which 3 multiple bonds would be reduced in such a situation? Can someone provide me with a detailed answer?


texts: Why does mercury have low melting and boiling points?

texts: Many metals have relatively high melting and boiling points, but mercury has relatively low melting and boiling points. What are the possible reasons for this?


texts: Why are certain reflections forbidden in body centered cubic and face centered cubic structures?

texts:
I know that for body centered cubic structures the allowed reflections only happen if h+k+l is even and reflections are forbidden is h+k+l is odd, and for basic face centered cubic structures (excluding diamond cubic) for a reflection to happen the h,k,l terms must be all add or even and if they're a mix of odd and even then the reflection is forbidden.

I've tried looking in textbooks/lecture notes as to how/why these selection rules come about but I can't find an answer which explains, it's just kind of stated that this happens. Why is it that you get these allowed and forbidden reflections?

I know it'll probably be something to do with the group space/symmetry/destructive interference within the structures but I can't come up with a definitive explanation other than just stating that it's to do with 'symmetry' or 'destructive interference within the cube'. Is there a more detailed and specific answer that explains what actually goes on within the structure?


texts: On the stabler tautomer in amide-imidic acid tautomerism

texts:
In the section on acid-catalysed hydrolysis of nitriles, this webpage has the following line of reasoning;

...the more stable amide tautomer predominates the (following) equilibrium.

(credit)
How are the relative stabilities of these tautomers compared? I made up a reason of the resonance structure for the amide one having negative and positive charges on oxygen and nitrogen respectively, and vice versa for the imidic acid one, but I'd like clarification on that.
There's also another hand-wavy thing I thought about of the double bond being stable on the more electronegative atom, oxygen. Is that correct, too?


texts: Boiling point of a liquid increasing with temperature?

texts:
In my textbook, a statement is given, as follows:

  Boiling point of a liquid increases with increase in temperature

However, I was wondering, isn't this wrong? The boiling point of a liquid always remains the same, it doesn't change.

Hence, my question is:
Is the above statement wrong? If it is, then under what conditions does the boiling point of a liquid change?


texts: What does Molecular Orbital Theory allow you to predict?

texts:
Molecular Orbital theory reveals the outcome when two atomic orbitals overlap. Almost all of the time we draw a Y axis with the notation of energy that can be described using electron volt units (eV). However I don't recall in university lectures or in textbooks any actual values associated with either atomic orbital or molecular orbital states. For example when two Hydrogen atomic orbitals come together. Are there actual energy values associated with these and if so how would they relate to reactivity. In relation to this does Molecular Orbital theory allow to predict reactivity of common nucleophiles and electrophiles seen in Organic Chemistry.
Thanks


texts:
Which of the following molecules is/are polar

$\ce{B3N3H6}$
Hydroquinone
Benzene
$\ce{IF7}$

Molecules (4),(3) are non-polar. Molecule (4) has pentagonal bipyramidal structure and the dipole moments of \ce{I - F}$ Bonds cancel out.

I thought the answer was (1) (inorganic benzene). But the answer given is (2). How is hydroquinone or para-hydroxyphenol polar?


texts: How can I separate benzidine from a food colouring (FD&C red 40)?

texts:
I'm doing a research paper on the food colouring red $40$ (also known as Allura red) and the fact that it contains a carcinogen: benzidine.

I am having trouble finding a way to separate the benzidine $(\mathrm{C}_{12}\mathrm{H}_{12}\mathrm{N}_2)$ from red $40$ $(\mathrm{C}_{18}\mathrm{H}_{14}\mathrm{N}_2\mathrm{Na}_{2}\mathrm{O}_{8}\mathrm{S}_2)$ to determine the concentration of benzidine in the colour since they are both organic.

Paper chromotopgraphy wouldn't work because I need to quantify the amount of benzidine as well, which is the aim of my project.

I am a highschool student and I have very limited resources available to me and therefore the method of separation shouldn't be very complicated but instead, rather basic. Does anyone have any suggestions.


texts: Is zero dipole moment possible in a square pyramidal complex?

texts: Say, the complex is [ML5] and is repelled in magnetic field. Given, its dipole moment is zero. Can its shape be predicted as trigonal pyramidal by the given information or square pyramidal structure may also fullfill them?


texts: What conditions can cause a material to exist as a gas?

texts:
So my question is, how can something exist a gas. Is it when the pressure exerted by the gas is greater than the atmospheric pressure, then it is a gas?

And also how do manometers work, how can you measure the pressure of a gas if the atmospheric pressure is greater?

  Taking a look at the example above, I understand that the pressure
  exerted by the gas can be greater than the atmospheric pressure,
  because only then you have a gas. But what I don't understand is why a
  substance exists as a gas when the atmospheric pressure is greater?
  Shouldn't the atmospheric pressure crush the substance to a solid or
  liquid?

I know this is a lot, but please help.


texts: Calculation of an equilibrium constant when data for reactants and products is given

texts:
Lets say that I want to calculate the equilibrium constant $K$ for a chemical reaction where $\ce{A -> B}$

$$K = [\ce{A}]/[\ce{B}]$$

where $[\ce{A}]$ is the concentration of $\ce{A}$ and $[\ce{B}]$ is the concentration of $\ce{B}$ at equilibrium

I have measured the quantities $[\ce{A}]$ and $[\ce{B}]$ and thus have two sets of data.

To calculate $K$ should I:

Take the ratio of $[\ce{A}]$ and $[\ce{B}]$ at each data point and then calculate a mean average of all of the $K$ values?
OR Plot a graph of $[\ce{A}]$ against $[\ce{B}]$ and use the gradient of the best fit line as the value of $K$?

My instinct tells me it is the former as the straight line plot on excel has a non-zero intercept (which is not reasonable). If it is the first option, can you explain to me why it is so?


texts: NMR Coupling in an aromatic system via π system

texts:
I was presented today with the following molecule:

and asked the splitting pattern of $\ce{H_a}$ given that up to $\mathrm{^3J}$ and $\mathrm{^4J}$ coupling is allowed.

I thought that $\ce{H_a}$ couples to $\ce{H_b}$, $\ce{H_c}$ and $\ce{H_d}$ given that

there is a $\mathrm{^3J}$  coupling to $\ce{H_b}$ (Clockwise)
there is a $\mathrm{^4J}$  coupling to $\ce{H_c}$ (Clockwise)
there is a $\mathrm{^4J}$  coupling to $\ce{H_d}$ (Anticlockwise)

Hence the splitting would be ddd.

However, the answer is apparently dd for the splitting of the $\ce{H_a}$ signal.

My thought was that anticlockwise, the $\mathrm{^3J}$ coupling is not possible due to the absence of a π bond in that direction down to $\ce{H_d}$ hence the coupling through the π system would not be possible.

Am I correct or is there another reason for no $\mathrm{^3J}$ coupling to $\ce{H_d}$?


texts:
Wikipedia states:

  After using toothpaste, orange juice and other juices have an unpleasant taste. This effect is attributed to products of the chemical reaction between stannous fluoride in toothpaste and the acetic acid in the juices. Sodium lauryl sulfate alters taste perception. It can break down phospholipids that inhibit taste receptors for sweetness, giving food a bitter taste. In contrast, apples are known to taste more pleasant after using toothpaste.

The primary reference for this appears to be a comment on the US Department of Energy website.

There are several references to this.

This seems to be an untested hypothesis. My question is Are there any papers linking the bad taste of orange juice after toothpaste to sulfates?


texts:
Bank of England has issued a new £5 note which contains Animal Tallow. I was wondering if you can explain to me as to how the animal tallow is used in this process. Also would you be able to speculate as to tallow of which animal could potentially be used in this production process?

Does the animal tallow completely transform or are its original characteristics retained?

Bank of England official Press Release is as follows:

We are aware of some people’s concerns about traces of tallow in our new five pound note. We respect those concerns and are treating them with the utmost seriousness.

This issue has only just come to light, and the Bank did not know about it when the contract was signed.

Information recently provided by our supplier, Innovia, and its supply chain shows that an extremely small amount of tallow is used in an early stage of the production process of polymer pellets, which are then used to create the base substrate for the five pound note.

Innovia is now working intensively with its supply chain and will keep the Bank informed on progress towards potential solutions.


texts: Why are hexamonodentate ligands optically inactive?

texts:
After encountering a lot of problems on optical isomerism of coordination compounds I have come to an idea that only complexes with polydentate or tridentate ligands shows optical isomerism. For example $\ce{[Co(en)3]^{3+}}$ shows optical isomerism but complexes such as those having platinum as the central atom and having six different monodentate ligands don't show optical isomerism. I have no trouble understanding why $\ce{[Co(en)3]^{3+}}$ shows optical isomerism but I am facing trouble finding out a reason for the second case.

The main question is why do complexes having monodentate ligands don't show optical isomerism?Any ideas?


texts: Kinetics of converting a water + heavy water mixture to HDO

texts:
Imagine an initial 50%-50% mixture of normal ($\rm H_2 \rm O$) and heavy water ($\rm D_2 \rm O$).

I think, simply mixing them, the result will exponentially converge to an equilibric state, where about a half of the solution is $\rm{HDO}$.

What is the time constant with what the system is going to the equilibric state?

Does some "easy" way exist to estimate the reaction speed in such systems, or it has to be determined experimentally?


texts:
If place a can of pressurized liquid butane (such as a lighter refill canister) into a freezer to get it below its boiling point of $-1\ \mathrm{^\circ C}$,
and then release it into a container kept at a freezing temperature, will it remain in the liquid state without boiling off (until it reaches its boiling point), or will it boil off immediately?

I had a cold metal container kept at a stable temperature of $-7\ \mathrm{^\circ C}$, but when I released room temperature butane into it, it boiled off instantly.

Why did that happen, and what will happen when it is released from the can at a temperature at or below $-1\ \mathrm{^\circ C}$?


texts: If we replace two oxygen in $\ce{-COOH}$ what is the name of the compound we get?


texts: What is the origin of 'tenting' or 'roofing' in NMR spectra?

texts:
Given an NMR spectrum with two coupled nuclei one can often observe so-called 'roofing' – an asymmetry in the multiplet.

For example, here is a 300 MHz proton spectrum of 1-bromo-2-methoxyethane, where the inset shows the triplets corresponding to the adjacent $\ce{CH2}$ groups:

(Source: Hans Reich, University of Wisconsin)

What is the origin of that effect?


texts: Why does chromium(III) have the highest tendency to form complexes, comparatively, among Mn(III), Cr(III), V(III) and Ti(III)?

texts: I was looking at some quick revision notes for d&f block elements and it had this random fact: Out of $\ce{Mn^3+}$, $\ce{Cr^3+}$,  $\ce{V^3+}$, and $\ce{Ti^3+}$, chromium readily forms complexes. I did not understand which properties of chromium make it advantageous for it to form complexes, was it due to its size? Its electronic configuration? Were there any other properties at play?


texts:
I am confused about $\mathrm{H_0}$ value of fluoroantimonic acid. Wikipedia says $\mathrm{-23<H_0<-21}$. Others say around $-31$. There's a huge gap. I won't worry for $3-4$ fluctuations but worry for $10$.

Can anyone provide confirmed data?


texts: Why does covalent nature in ionic solids increase the lattice energy?

texts: I have observed in my textbooks that ionic solid that have a greater covalent character tend to have higher lattice energy. Can this be generalised as fact?


texts: Why does this compound only have one pair of enantiomers?

texts:
I've been doing some reading about enantiomers, which are apparently chiral molecules that are non-superimposable mirror images of each other. An example I found of this in some problems that I've been attempting seems to have stumped me somewhat:

Take the compound $\ce{CH2=CH-CHD2}$, where $\ce{D}$ is deuterium, or hydrogen-2, and react it with deuterium gas. A pair of enantiomers is formed, both with the condensed formula $\ce{DCH2-CHD-CHD2}$. The answers provided say that these enantiomers are as follows:

...where $\ce{A}$ is standing in for deuterium.

Why don't you get enantiomers where the orientation of the $\ce{C-D}$ bonds at both ends of the molecule varies? (ie. where those $\ce{C-D}$ bonds are also in varying planes, represented by different combinations of hashed and solid wedges on paper.) Here's an example of what I mean:

Why aren't these two structures considered to be another pair of enantiomers also?

Is this - the orientation of bonds at the end of carbon chains counting effectively for nothing - the case with all stereoisomerism in alkanes?


texts: How could uranium be extracted from ore to be melt?

texts:
I would like to go hunting for uranium ore, and because it has a relatively low melting point (1132.2 °C), I thought it would be cool to melt it just like any other metals. According to this video extracting yellowcake (mainly U3O8, UO2 and UO3) is relatively easy, however, how could I remove the oxigen from the oxides? Or is it easier to obtain the uranium directly from the ore in another way?

EDIT: because of all of the comments I've received I'm going to explain better the question:

I'm well aware of the dangers of handling uranium, a weak radioactive materials, the fact that it's dangerous as an heavy metal and that the ore is more radioactive than the pure metal because there are products of the decaying chain that are more active tha the uranium itself.
I know all the regulations and laws in my country, so that I know how much I can keep it (about 0.1 curie) and what I can and what I cannot do with my uranium source. I also know where I can get it withouth getting in trouble.
what I need to know is what chemical peocess I could use to extract pure uranium metal (238U + 235U) that I can melt in whatever shape I please. And no, I don't want to make a nuke because that would be impossible


texts: Logical reasoning behind the formula for molar conductance of an electrolyte

texts:
I am studying some introductory material on electrochemistry. My book and all standard websites I've found define the molar conductance of an electrolyte as "conductivity of an electrolyte solution divided by the molar concentration of the electrolyte."

I am unable to figure out how this definition was arrived at. Can anyone provide a logical, beginner-level, step-wise approach to how this definition was reached?


texts: Why is the transition (0,0,0) -> (1,0,1) observed in a gas phase IR spectrum of CO2?

texts:
Let ($v_1$,$v_2$,$v_3$) denote the vibrational state of $CO_2$.

Why is the transition $(0,0,0)\rightarrow (1,0,1)$ observed when the trasition $(0,0,0)\rightarrow(1,0,0)$ (asymmetric stretch) is not observed because it is IR inactive (not allowed)?

Is the following procedure correct for showing that the $(0,0,0)\rightarrow(1,0,1)$ transition is allowed?

The criteria for the transition being allowed is

$$\Gamma_{tot. sym.}\in\Gamma_{initial} \times \Gamma_{x,y,z}\times\Gamma_{final}$$

Where $\Gamma$ is the "irrep" of the group $D_{\infty h}$ and $\Gamma_{tot. sym.}=\Sigma_g^+$. The initial state is $(0,0,0)$ and the irrep is $\Gamma_{initial}=\Gamma_{(0,0,0)}=\Sigma_g^+$

The irreps of the three normal modes $v_1$, $v_2$ and $v_3$ are

$$\Gamma_1=\Sigma_g^+\text{, }\Gamma_2=\Pi_u\text{, }\Gamma_3=\Sigma_u^+$$

From a character table we get that

$$\Gamma_{x,y}=\Pi_u\text{ and }\Gamma_z=\Sigma_u^+$$

Now, this is the step I'm not sure about; we say that the irrep of the state $(1,0,1)$ is $$\Gamma_{(1,0,1)}=\Gamma_1\times\Gamma_3=\Sigma_g^+\times\Sigma_u^+=\Sigma_u^+$$

And finally, using a product table, we get

$$\Gamma_{(0,0,0)}\times\Gamma_{z}\times\Gamma_{(1,0,1)}=\Sigma_g^+\times\Sigma_u^+\times\Sigma_u^+=\Sigma_g^+\ni\Gamma_{tot.sym.}$$

And thus the transition is allowed and we observe it as a band in an IR spectrum.


texts:
What do the subscripts on the orbitals (such as px, py, pzetc) mean and how can one derive these or at least gain a fundamental understanding of each? Do they describe the geometry of the shape? And if so- how do derive them?

Please describe in an advanced high school level.


texts: If it's OD of 600nm I know that's the wavelength used, but what are the other numbers in something like  "OD 600nm of 0.6-0.7". The 0.6-0.7?


texts:
Does Hund's rule allow both of the following scenarios?

Filling each orbital with a single electron, so that a sub-shell, at first, only electrons with a negative spin
Filling each orbital with a single electron, such that a sub-shell, at first, only electrons with a positive spin?

I assume two H atoms whose electrons have different spins would form $\ce{H-H}$ and atoms where the spins are the same would form $\ce{H:H}$. Is that correct?


texts: Is the mixture of alkyl dimethyl benzyl ammonium chloride and vinegar dangerous?

texts: So I was trying to clean cat pee out of my carpet and I scrubbed it with a Lysol wipe that says the active ingredient is alkyl dimethyl benzyl ammonium chloride and without thinking then sprayed white vinegar on the area. Now I'm afraid that made a bad chemical mixture? Do you know if those 2 ingredients are dangerous?


texts: Assigning absolute configuration when determining crystal structure isn't possible

texts:
When natural products are isolated, their structures are often determined by x-ray crystallography which gives a complete picture of the atom coordinates, the relative and the absolute stereochemical configurations. If however the isolated molecule won't crystallize, how can absolute stereochemistry be obtained?

I know that 2D NMR can tell about connectivity and also possibly relative stereochemistry ($J$-value analysis), but unless one stereocenter is known the others cannot be implied from it. Optical rotations also are useless unless the compound is known. How then can the absolute configuration be found without single-crystal x-ray diffraction?


texts:
I have to calculate the bond dissociation energy of steam. I'm a total noob, so don't go too hard on me.
(I'm translating the exercise by myself, sorry if there is a mistake.)

Calculate the bond dissociation energy of gas-water/steam ($\ce{H2O}$). Whereas the total enthalpy of the bound is the sum of the "sub-bounds". Use the following table:

Now, we have: $\ce{2H2 + O2 -> 2H2O}$
Imagine we have a tank with one $\ce{O2}$ and two $\ce{H2}$, then, according to the table (if I read it correct), we need $2\cdot436\ \mathrm{kJ} + 497\ \mathrm{kJ}=1396\ \mathrm{kJ}$ to "break" the bonds. We then get two $\ce{O}$ and four $\ce{H}$. They react to two $\ce{H2O}$
Now, according to the table, two $\ce{H2O}$ need $2\cdot 2\cdot 463 \ \mathrm{kJ}=1852\ \mathrm{kJ}$ to bind together.
So, we start with a system of total inner energy $1396\ \rm kJ$ and end up with one of $1852\ \rm kJ$. Clearly, we have to put energy into the first system to get to the second.
Now, that's obviously false - but I don't get why. I'd expect a exothermic reaction because 1. I just know it is and 2. because the $\ce{O2}$ have a double bound which I just expect to be harder to break.
So where is my thought wrong?


texts: Why is carbon dioxide used in soda? What makes it preferable to other gases for this purpose?


texts: Rigorous reason behind internal energy change being zero while mixing

texts:
A container is divided in two parts: one part contains oxygen gas $(n_1$ moles, at temperature $T_1)$ and the other part contains helium gas $(n_2$ moles, at temperature $T_2).$ The partition separating them is removed. Find the final temperature of the mixture $(T).$

While solving this (multiple choice exam) question, since I was constrained by time, I started to look for hints within the question. I realized the question has explicitly mentioned the gases, i.e. it gave us information about their degrees of freedom (since oxygen is diatomic and helium is monoatomic). So my instinct was that this had to do something with $C_V.$ At the time, I hypothesized $\Delta{U}_\mathrm{sys} = 0.$ Thus:
$$n_1\frac{5R}{2}(T - T_1) + n_2\frac{3R}{2}(T - T_2) = 0$$
$$T = \frac{5n_1T_1 + 3n_2T_2}{5n_1 + 3n_2}$$
Which was indeed one of the options, and in fact, the correct one.
However, is there any rigorous method/reasoning that tells us why exactly is it that $\Delta{U}_\mathrm{sys} = 0?$ I can't think of a satisfactory explanation. I tried to analyze it using the first law of thermodynamics, but that clearly seems to be the wrong approach.


texts: Can ethyl acetate isolate cinnamaldehyde from cinnamon oil?

texts: I recently watched a video on extracting cinnamaldehyde from cinnamon using dichloromethane as a solvent.  I would like to attempt the process.  However, I would prefer not to use haloalkanes because of the health risks.  Would ethyl acetate be a suitable replacement solvent for dichloromethane in extracting cinnamaldehyde from cinnamon oil?