texts: Does a diatomic gas have one or two vibrational degrees of freedom?

texts: Many sources claim that the vibrational degrees of freedom for a diatomic gas is one, but there are also a few which claim it to be two. Which is correct, and why is there even any ambiguity to begin with?


texts: What is the accuracy of medical syringes?

texts: I am interested in both low and high volume syringes.


texts:
In a gravimetric determination of phosphorus an aqueous solution of dihydrogen phosphate ion is treated with the mixture of ammonium and magnesium ions to precipitate magnesium Ammonium Phosphate. This is heated and decomposed to magnesium pyrophosphate which is weighed. A solution of $\ce{NaH2PO4}$ yielded 1.054 gram of $\ce{Mg2P2O7}$. What weight of $\ce{NaH2PO4}$ was originally present?

I attempted the question and my answer was coming out to be 1.32 gm where as the real answer is 1.14 gm

P.S: I wanted to post the pic of my solution so that i could be corrected  , but just cant figure out how to upload the photo.

And also can somebody give the answer without using POAC


texts: Kinetic Theory of Gases and molecular velocities of gases

texts:
The assumption that molecules collide with elasticity was postulated in the kinetic theory of gases.
So my question is molecules should have higher tendency to collide obliquely and would therefore result in change of velocity (as the vector components would cancel or add up the velocities of molecules, resulting in change of velocities of molecules) and energy states of electron, are the assumptions not very correct or am I wrong?


texts: Chemical reaction that can produce lots of heat from 2-3 simple liquid ingredients?

texts:
Have an experiment I want to try out utilizing thermoelectric power and I want to generate the heat via a simple chemical reaction. Ideally I'd like to mix 2 liquids together (one being water or alcohol would be great) that can get to around boiling water temperature for a few minutes or longer. Byproducts need to be only other liquids that can be drained easily or gasses that aren't dangerous to humans. No solids wastes and non corrosive / carcinogen / caustic.

So far I've found one that's close to my needs but still produces a solid waste product and isn't particularly safe, which is Calcium Oxide + Water -> Calcium Hydroxide + Heat. This might work if there's another liquid I could add after the main reaction to turn the Calcium Hydroxide into a liquid for disposal.


texts: Reaction of Grignard reagents with esters

texts:
Suppose I have a phenyl Grignard and methyl benzoate.

If I react the two, can I expect benzophenone and a triphenylmethoxide ion as my products?

I ask because I know that Grignards react with ketones and aldehydes. So as the benzophenone is generated, couldn't more Grignard attack the benzophenone as well as the original reactant?

Expected products and mechanism shown below:


texts:
When I want to check a $\mathrm{p}K_\mathrm{a}$ value I look it up in CRC Handbook. Is there such source for UV cut-off values of various buffers?
Usually books in chromatography contain tables with that data, but often no source is given.


texts: Nucleophiles in protic and aprotic solvent

texts:
If the nucleophiles have almost same size (not a large difference) such as $\ce{C- , N- , O-}$ then how their nucleophilicty varies in protic and aprotic solvents?\

Does it depend on types of reaction such as Sn1 or Sn2 ?


texts: How to balance the reaction between ethanol and chlorine using oxidation number method?

texts:
Balance the following chemical equation using oxidation number method:
$$\ce{C2H5OH + Cl2 -> CHCl3 + HCO2- + Cl- + H2O}~\text{(In basic medium)}$$

Chlorine in $\ce{Cl2}$ is in oxidation state $0$ and it is changing from $0$ to $-1$ in both $\ce{CHCl3}$ and $\ce{Cl-}.$
$\ce{C2H5OH}$ has two carbons and both of them have different oxidation states: one has $-3,$ the other has $-1,$ and they are changing to $+2$ in both the products $\ce{CHCl3}$ and $\ce{HCO2-}.$
So, it is definitely a redox reaction and thus I want to use oxidation number method to balance this equation.
I am finding it hard to balance because of multiple products of $\ce{C}$ and $\ce{Cl}$ in the same equation.


texts: Inductive effect of alkyl ammonium groups

texts:
Why $\ce{-NR3+}$ has more -I effect than $\ce{-NH3+}?$
And what about order of $\ce{-NHR2+}$ and $\ce{-NH2R+}?$

My attempts
I got idea about electronegativity of carbon atom in $\ce{R}$ is more than hydrogen atom, hence positive charge gets more concentrated on nitrogen atom and it exerts more electronic attraction. But this didn't worked out in latter case when -I effect of $\ce{-NHR2+}$ is less than $\ce{-NH2R+}.$


texts: Would a carbamate be attacked twice by an alkyl lithium cuprate reagent?

texts: For example, say you react ethyl carbamate with methyl-$\ce{LiCu}$; would two methyl groups displace both the amide and the ester, creating an isopropyl alcohol?


texts: Troubles with cinnemaldehyde extraction - A few general questions

texts:
I'm trying to do a cinnemaldehyde extraction.  I've tried both a simple and a steam distillation.  I'm using the video: [https://www.youtube.com/watch?v=bDoaPIKT_Xg] - as a guide.  One of the main problems is that, at the end, the receiving flask is full of water and has very few drops of oil whereas the video shows I should have a foggy mixture.

First off, what's up with that?  Second, third and fourth:
What is a good solvent to use other than DCM/ether?
I have read a lot but haven't figured out: What information does one use/how does one know what makes a good solvent given a situation?  Through some research, I decided to use methanol as an alternate solvent - I ended up with a purely clear substance in the separation flask - No layers to separate.  I have isopropyl, methanol, acetone and naphtha to choose from as solvents.

Finally, in the video, I'm having difficulty understanding what the guy is doing after separation.  I've watched the video several times but it still makes little sense to me.  If this last paragraph doesn't make sense, please just focus on the first two - Theoretically, I could figure out the last part through trial and error - that's why I'm doing such a benign experiment as my first.


texts:
Nickel :

Does not harden austenitic stainless steel
Ease the tempering of martensitic stainless steel
Harden maraging steel by forming precipitates

I also read people saying that it harden ferritic steel. Is it true ?

The chemicals reasons behind all of this are quite unclear for me. Could you explain how it works?

Thanks


texts: Why does the molar conductivity plot behave this way?

texts: On the left image.. we see that specific conductivity is increasing at a decreasing rate, eventually plateauing as it reaches a maximum. I am unable to reconcile this with the molar conductivity graph to the right... shouldn't the decreasing molar conductivity be decreasing at an increasing rate... why does it plateau and such? Thanks for the help


texts: Solubility of p-nitrophenol in various substances?

texts:
So I had an organic chemistry lab where we had to dissolve p-nitrophenol in water, dilute $\ce{NaHCO3}$, dilute $\ce{NaOH}$, and dilute $\ce{HCl}$ to test for solubility.

The p-nitrophenol dissolved in everything but water. I just want to make sure if these results are theoretically correct. From what I understand, the nitrophenol should have also dissolved in water because its a polar substance and it shouldn't have dissolved in $\ce{HCl}$ because I think the Hydrogen in the phenol is itself acidic due to electron withdrawing effects of the benzene.

Can someone please explain what should happen?


texts: Can rocket candy explode during the preparation?

texts:
I would like to follow the steps in this video: https://www.youtube.com/watch?v=hyPysthIRss

After I mixed the Potassium nitrate KNO3 and the sugar, I start to cook it in a pot, and stir it very often. After 25-30 min, the KNO3 and the sugar will melt together, and become a brown mass.

My question is: Can this mixture explode during the heating somehow? Or it can just burn, not explode? How to prevent it, and do it the most secure way?


texts: Why does beryllium have an exceptionally high hydration energy?

texts:
You would expect solubility of  Group $2$ fluorides to increase down the group, as lattice energy plummets much more sharply than hydration energy does. For the most part, this is true: $\ce{BaF2}$ is more soluble than $\ce{SrF2}$, which is more soluble than $\ce{CaF2}$, and so on. However, $\ce{BeF2}$ is several times more soluble than even $\ce{BaF2}$. Why is that?
Beryllium forms the complex $\ce{[Be(H2O)4]^{2+}}$ in water. According to Wikipedia, $\ce{M-O}$ distance expectedly increases down the group and enthalpy of solvation becomes less and less negative, but beryllium aquo complex is the black sheep:
\begin{array}{c|c|c}
 & \ce{[Be(H2O)4]^{2+}} & \ce{[Mg(H2O)6]^{2+}} & \ce{Ca^{2+}(aq)} & \ce{Sr^{2+} (aq)} & \ce{Ba^{2+} (aq)}\\
\hline
\ce{M-O distance (pm)} & 167 & 209 & 242 & 263 & 281\\
\ce{\Delta H- solvation (kJ mol^{-1})} & 2494 & 1921 & 1577 & 1443 & 1305
\end{array}
I found these solubility figures from JD Lee's Concise Inorganic Chemistry, Fifth Edition:
\begin{array}{c|c|c}
 & \ce{BeF2} & \ce{MgF2} & \ce{CaF2} & \ce{SrF2} & \ce{BaF2}\\
\hline
\ce{solubility (grams solute per 100 g water} & \ce{very soluble} & 0.008 & 0.0016 & 0.012 & 0.12
\end{array}


texts: Oxidation of alkyl side chain using KMnO4

texts:
I was reading about side chain oxidation of alkyl side chains of benzene using alkaline $\ce{KMnO4}$ and heat. My book (Solomon's and Frhyle) says that this is only for compounds having a benzylic hydrogen and has given examples of ethyl and methyl benzene. I have searched the internet but could not find a mechanism. I tried to find something of my use in that research paper given in this link.

I want to know what would happen if I take something like an ester or aldehyde/keto group, or any other organic functional group attached to a benzene ring. Will this reaction always happen with any aryl compound? Also, I came across an example of acetophenone being oxidized to benzoic acid by this method. It doesn't have a benzylic hydrogen so why does it still get oxidized?


texts: Is it possible to create a 100% identical copy of a chemical? For example, a 100% identical copy of vitamin A would have the same shape, the same formula, and the same structure.


texts: Why do solutions of electron in a box (and in a ring) predict coefficients for LCAO (linear combination of atomic orbitals) in 1D systems?

texts:
The solutions to the 1D particle in a box quantum mechanic system are standing waves (zero at both ends of the box) with 0,1,2... nodes for increasing energy (zero for the ground state).

If I look at the LCAO solutions for a linear system, combining AOs of the same shape and energy (e.g. conjugated double bonds, linear array of sodium atoms), the coefficients follow the pattern of a standing wave with 0,1,2... nodes. For example, when I combine 3 AO's in a row, the solutions are +++, +0-, +-+, i.e. zero, one, and two switches of signs as I go to higher energy states. For the state with one node, the node is in the center of the box, corresponding to the middle AO, which has a coefficient of zero. (More examples, i.e. hexatriene and pentadienyl cation, are on slide 126 and 128 of this document.)

The solutions to the particle in a ring system are standing circular waves (same value at 0 and 360 degrees) with 0,2,4... nodes for increasing energy. The animation shows a standing circular wave with 8 nodes:

If I look at the LCAO solutions for a circular system, again combining AOs of the same shape and energy (e.g. p-orbitals in an aromatic system), the coefficents follow the pattern of a circular wave with 0,2,4... nodes. For benzene, the solutions are ++++++, +++--- and +0--0+, +-++-+ and -0+-0+, +-+-+- (see picture):

What underlies the connection between the unbound electron in a box or corral with the formation of covalent bonds of bound electrons?


texts:
While filling liquid oxygen into a tank, why do they do open one end?
Then what is use of filling?

I don't think people who are filling this truck are beginners.


texts:
I have a cube of pyrite similar to:

(Source: Britannica)

Can pyrite turn into sulfuric acid?

Is this dangerous for me to touch, especially if my hands are sweaty?


texts: Is Van der Waal's force the real source of friction?

texts:
I'm currently taking a physics class, and my teacher explained that friction is the result of intermolecular interactions, and that energy must be applied in order to break these bonds.

This got be thinking about what kinds of things have a high coefficient of friction, and immediately my mind went to sandpaper. The atomic surface of these mineral crystals would be really smooth and not easily polarizable, as they are held tightly in place by the other ions. So does surface area have more to do with friction than actual Van der Waals forces? This would also seem to explain how geckos are so adept and clinging to things like glass, as the tips of their fingers are so highly ridged.


texts:
$\ce{Heat\ +\ PCl5(g)\ \rightleftharpoons\ PCl3(g)\ +\ Cl2(g)}$

According to the process above, which of the following can be done to increase the number of moles of $\ce{Cl2}$ in a sealed container at equilibrium?

Reducing temp
Increasing the pressure at a constant temp
Adding more moles of $\ce{PCl5}$

I'm pretty sure it's not 1. but I'm stuck between 2. and 3. Are they both true or only one of them?


texts: Anomalous trend in formation enthalpy of alkali metal halides

texts:
I read that in alkali metal halides, the formation enthalpy for fluorides become less negative as we go down the group, whereas the reverse is true for chlorides, bromides and iodides.

Why is it so? In my opinion, the formation enthalpy should increase with the stability which according to me, will increase as the cation's size increases and anion's decreases.

Therefore the trend is understandable in chlorides and others, but what about fluorides? May be it is due to its extremely small size but I can't find a suitable reason.


texts: The mass of a carbon-12 atom is 12 amu. What percent of the mass is located in the nucleus? and Why is the value so close to 100%?


texts:
According to what i learned in university, the energy of orbitals increases when the principal quantum number n increases. Also, in a given shell, s orbitals have lower energy than p orbitals which have lower energy than d orbitals, which in turn have lower energy than f orbitals.

And according to Aufbau principle: "Electrons fill lowest energy orbitals first."

But when we write the electron configuration of atoms, it goes as follows:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p

For example, why is 4s filled before 3d?
I think i have a big misconception here.

Another question circulating around the same topic is the order of electron removing when we want to form cations. To take as an example, let's take the electronic configuration of the atom Mn and its cation Mn2+

Mn: [Ar] 4s2 3d5

Mn2+ :[Ar] 3d5

Why did we remove electrons from the 4s before the 3d? Shouldn't the order of removing electrons be exactly the opposite pathway of Aufbau principle? And what is exactly the method used to remove electrons from an atom to form its cation?


texts:
In 1873 a German chemist named Springmühl announced a derivative of alizarin which acted as a blue dye and he sold this dye for a high price. The dye was sometimes called "anthracine blue" and Springmuhl kept the process for producing it a secret.

Has the composition of this dye ever been revealed?

From Chemical News, April 25, 1873:

  Anthracene Blue.— A few years since aniline was the great source of new and beautiful colours. Now that every possible shade of colour, surpassing in number and beauty the hues of the rainbow, have been produced from aniline, the chemist has taken up the study of anthracene and alizarine, also coal-tar products. While preparing artificial alizarine from anthracene, Springmühl has obtained a by-product, from which he has made a beautiful blue colour, superior in some respects to any of the aniline blues. The process by which it was prepared he keeps a secret. Dried in vacuo, it is a blue powder with a few little crystals. In this it differs from the aniline dyes, which are one colour when dry, another when in solution. When pure hot water is poured over anthracene blue it mostly dissolves, but leaves a little insoluble residue. The addition of an alkali destroys its colour, which is restored, however, by an acid. The strongest mineral acids are unable to destroy its colour, but rather heightens its tone. Unlike aniline dyes, it is insoluble in alcohol and ether. Experiments show that it withstands the action of light better than aniline blue. Unfortunately, it is at present very expensive, for Springmühl obtained but 2'5 grains of anthracene blue from 25,000 grains of anthracene, which makes it cost about 3000 dols, per pound at present. A cheaper method of making it is certainly desirable.—American Artizan.


texts: When recovering Copper from Copper Chloride via Aluminum, why can't we use Sodium instead to make Sodium Chloride?

texts:
About a week ago in my Middle School Science Class, we used an aluminum washer and some copper chloride, which we had gotten from creating circuit boards, in a closed system to recover the copper (if it was possible). We resulted in getting some copper flakes, but as a consequence the copper was replaced by aluminum in the chloride solution. So technically it is still a waste material that can't be used in everyday life, despite having recovered the copper.

So I got thinking: If Salt, or Sodium Chloride, is Sodium and Chlorine, and is much more useful than Aluminum Chloride or Copper Chloride since we need it in our everyday diets, what prevents us from using it to recover copper from chlorine?

I asked my teacher what she thought about the subject, and she explained that apparently sodium is very reactive when not bonded to anything and so is hard to come by naturally without extracting it from something else. I gathered that Aluminum, as reactive as it is, is apparently more common to find, or cheaper to manufacture, than sodium is. This was an unsure answer, as the costs and waste produced when manufacturing aluminum vs. manufacturing sodium were not looked up or explained.

However, in an earlier lesson we had learned that manufacturing aluminum produces a lot of hazardous waste, and so does not have a great impact on the environment to make. I do not know about sodium and its costs and waste production.

With that information provided, and a consideration of the environment at hand, would it be better to consistently use sodium in the recovery of copper from copper chloride than aluminum? Consider all waste produced from manufacturing and all costs to create when answering, please.

Thank you.


texts: What are the primary, secondary and tertiary physicochemical properties of ionic liquids?

texts:
In the following sentence

  ..the ability to modulate the individual components presents an advantageous framework for tuning secondary and tertiary physicochemical characteristics without sacrificing the primary function of the ionic liquids.

What do they mean by secondary and tertiary physicochemical characteristics?
Can somebody give example of this categorization of the physicochemical property?


texts: Cyclopentadiene/etc. hydrophobicity after nitrogen atom substitution at a double bond?

texts:
If I take a compound like cyclopentadiene ($\ce{C5H6}$) and I substitute a nitrogen for a carbon at one of the $\ce{C=C}$ bonds (making a $\ce{C=N}$ bond), how does this typically change the hydrophobicity of the compound?

The problem is that I'm not really a chemist.  My thought here is that nitrogen is more electronegative than carbon, so this will polarize the bond, induce a dipole, and make the molecule more hydrophilic.  In general, it seems to me that mixing together atoms of differing electronegativity in alkane or alkene/etc. compounds should create dipoles that can interact with polar solvent molecules, improving hydrophilicity.

As an additional thought, how would the nitrogen substitution effect stacking interactions between the substituted ring and a regular molecule of cyclopentadiene?  My guess here would be that hydrophobic effects would cause a more favorable pi-stacking interaction between two unsubstituted copies of cyclopentadiene relative to cyclopentadiene and the aforementioned and described nitrogen substituted version of the molecule.

To clarify, by "stacking interactions" I mean the sort of $\ce{C=C}$ stacking interactions that lead to cycloaddition reactions, not that the two rings will lie on top of one-another (as in the case of something like a pair of benzene molecules).


texts: Books showing colorful images of elementary particles....is this true?

texts: Do electrons or protons or any other elementary particle have colors of their own or do they have smell?


texts:
Just a quick question; I was looking up the MSDS for o-Toluic Acid for an experiment when I came across this in the "Hazards Identification" section.

Very hazardous in case of skin contact (irritant), ....
...
Slightly hazardous in case of skin contact (permeator).

How should this warning be interpreted?


texts: What exactly is causing analyte protonation in electrospray ionization MS?

texts: I commonly see explanations that the presence of acid in the mobile phase is a source of protons for the analyte, and that you should be multiple pH units below the pKa of the analyte, but in practice plenty of compounds that you end up detecting have pKa's that are well below the pH of any practical mobile phase or are not even protonatable - so how are these molecules being protonated?


texts: Predicting sign of enthalpy of allotropic transition of phosphorus

texts:
How to predict the sign of enthalpy during the transition
$$\ce{P(s, white) -> P(s, red)}?$$
$\ce{P(s, red)}$ is more stable than $\ce{P(s, white)}$ due to release in angle strain.
Since during formation of red phosphorus from white phosphorus bond breaking and bond formation both takes place, how to predict sign of enthalpy?


texts: Meaning of m2 in the symbol for an isotope of an element

texts:
What does the notation $^{197\mathrm{m}2}\ce{Pb}$ mean? Specifically, the '$\mathrm{m}$2' part.

I've found this and it appears to have something to do with charge distribution. The original notation was found here.


texts: Can the electron configuration of Te be written that way?

texts:
Normally, the electron configuration of Te is known as:

$$\begin{aligned}  {[Kr]} 5s^2 \ce{4d^10} 5p^4 \end{aligned}$$

Then, one day I was asked in a exam if this can be written also as:

$$\begin{aligned}  {[Kr]} 5s^2 \ce{4d^10} 5p^3 6s^1\end{aligned}$$

I answered that it couldn't. But my answer turned out to be wrong.

If this is correct, why is it allowed to be written like this? And what general case can I learn when being asked such tricky questions?


texts: Ethanol discolored yellow when stored with a rubber stopper. Forming fine white precipitate when added to water

texts:
I stored some Klean-Strip denatured alcohol in a test tube and capped it with a rubber stopper. I did this in preparation for a chemistry demonstration. When I opened my kit a few days later at the event, I was surprised to find that the ethanol in the tube had turned a definite urine yellow. It burned just fine but let off nearly imperceptible wisps of smoke. Even more interesting was when I added water into the tube, which caused an almost instant white precipitate to form. I had to improvise the demonstration and play it off as turning flammable urine into semen, which it closely represented (because it was meant to be a comedic demonstration for a mature audience). The next few days I ran an experiment of using the same denatured ethanol in a jar over the black rubber stopper. By the end of the experiment, the solution exhibited the same properties and characteristics as the accidental batch. Now, not even to save my own skin, I cannot come up with a reasonable explanation for why the ethanol turns yellow, what causes the discoloration, and how does it turn milky when water is added.

Why does this happen. Chemically, what is happening. And would this be a good indicator for a non-anhydrous chemical? For example, I can add this to methanol or NaOH, measure the "turned whitedness" and determine whether or not that chemical is truly anhydrous?


texts: What is the meaning of "charge separation" in resonance?

texts:
I've read that the resonance structures in which there is lesser 'charge separation' contribute more to the resonance hybrid than the ones with greater charge separation.

But I am unable to understand why it is so.

I mean isn't it correct that the presence of two charges on adjacent atoms leads to "less stability" due to bond stretching or/and compression?

But apparently, the actual observation is contrary to this argument.

I guess I'm actually confused about the meaning of 'charge separation'? Does it refer to the distance between the location of the charges or the difference between their amounts?


texts:
According to my textbook, electrons which are emitted due to the photoelectric effect have kinetic energy given by:
$$KE_{electron}=h\nu-h\nu_0$$
Where $\nu_0$ is the activation frequency of the metal.

My question is: when electrons are emitted in this way, is all of the photon's energy really converted to kinetic energy in the electron? Is there no loss of energy in this process?

If there is energy lost (which I suspect must be true), is it a sufficiently small amount so that we can say it is negligible for most purposes?


texts:
I know that when you have $\ce{HCl}$, $\ce{H2O}$, and $\ce{NaOH}$ that you produce $\ce{H2O}$ and $\ce{NaCl}$.

However some people say water does react and so would think that this 2 step reaction is correct and the 1 step reaction is wrong.

$\ce{HCl + H2O + NaOH -> H3O+ + Cl- + NaOH -> 2 H2O + NaCl}$

However others say that water does not react and think that the 2 step reaction is wrong and the 1 step reaction is correct.

$\ce{HCl + NaOH -> H2O + NaCl}$

I personally think that both of these happen and so water consumed = water produced and thus there is no change in volume. So does water react with the $\ce{HCl}$ via the 2 step reaction or is it just a spectator molecule waiting around until there is more water and salt?


texts: What computational methods are available for predicting nanoparticle structure?

texts: I'm a quantum chemist, and nearly every system I've ever cared about has been studied by DFT. However, I am currently trying to model the surface interactions on a nanoparticle around 100 nm in diameter. I know the composition of the nanoparticle, but I do not know which atoms are at the surface versus in the core. It's too large to really be reasonable in my regular DFT packages. Any ideas on where to start?


texts:
The structure of ozone is traditionally depicted using two resonance forms:

However, what I am wondering is instead of using such an idea to explain the structure why can't we show the structure of ozone like this?

Some people have told me that such a structure is not possible but they fail to mention the reason. What I have in mind is maybe electron repulsion. But I would like to know exactly what mechanism would prevent this from happening?


texts: I'm looking for something as strong as Acetone

texts: We use Acetone to remove nail polish and gel polish at our salon.  Is there another  alternative substance out there with less irritated smell like Acetone?


texts: Referring to numbered atom (e.g. C-1 vs C1)

texts:
Is there a recommended style how to designate an atom by its number according to the structure numbering (given by nomenclature, or any other one in the text context)?

The are (at least) two different styles used by IUPAC itself. E.g.[1]

  Diastereoisomers of glycosides, hemiacetals or related cyclic forms of sugars, or related molecules differing in configuration only at C-1 of an aldose, C-2 of a 2-ketose, etc.

or[2]

  Note: The configuration at C-4 (method 2) or C-1 (method 1) cannot be given because the attached substituent is unknown.

or[3]

  Small substituents on the C-8 and C-9 atoms of steroids should be drawn within the ring system in this fashion even if there are no substituents on the adjacent fusion atoms C-10 and C-14.

vs[4]

  The oxygen atom of the $\ce{CF3CO}$ portion of the ligand is attached
  to C2, while that of $\ce{MeCO}$ is attached to C4.

I can see some disadvantages for both of the styles.

With hyphen (dash):

Might be mistakenly thought, in favorable cases, that it is an isotope abbreviation. E.g. C-14 for carbon-14 ($\ce{^{14}C}$).
Not very likely, but eventually might be thought as a mathematical expression (e.g. when talking about 1st halogen atom X-1).

No hyphen:

When the text formatting was lost, it might be interconfused with molecular formula. Maybe not for carbon / organic chemistry, more likely for other elements in inorganic compounds, e.g. P4. Especially at chem.SE with Georgia font ☺.

References:

Basic terminology of stereochemistry (IUPAC Recommendations 1996), p. 2199 (anomers, via IUPAC Gold Book)
Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013, p. 551
Graphical representation standards for chemical structure diagrams (IUPAC Recommendations 2008), p. 356
Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005), p. 156


texts: Method to determine ibuprofen content in dosage forms

texts:
Please suggest some methods for determining the ibuprofen content in tablets, capsules and liquid dosage forms.

Is there a method which this can be done using UV spectroscopy?


texts:
I'm more asking this because I'm not sure how far science has come.
Pretty much, I've been thinking about the car exhaust system lately. The two main components that lead to hazards from cars are $\ce{CO}$ and $\ce{NO_{$x$}}$. Carbon monoxide is hazardous because it thrives to become $\ce{CO2}$ and robs living beings of the oxygen in their bloodstream to become carbon dioxide. And the nitrogen oxides are hazardous only as that compound, but nitrogen and oxygen are quite harmless as $\ce{N2}$ and $\ce{O2}$.

Would it be possible to separate the oxygen from $\ce{NO_{$x$}}$ and somehow give that to the $\ce{CO}$, and any left over oxygen simply becoming $\ce{O2}$?

This all might be a stretch, but I have an active imagination and like seeking out answers to these questions.


texts: What chemical test can differentiate secondary and tertiary alcohols?

texts: I have to perform a chemical test to determine whether the solution is a secondary or a tertiary alcohol. How can I do this? Please explain the procedure and the apparatus.


texts: Calculating moles of Hydrogen gas in multiple gas container

texts: If there was a 500 mL container filled with oxygen and hydrogen so it burns completely (2H:1O), how many moles of hydrogen gas would there be if there if pressure is 101.3 kPa and the temperature is 293 K?


texts: Why does a six-membered ring contract in this SN1 reaction?

texts:
I was watching this video on Khan Academy (YouTube link) regarding SN1 mechanisms and carbocation rearrangements and came across this mechanism.

At around timestamp 4:20 in the video, why does step 2 take place where the ring contracts to 5 carbons? Surely it would be far easier to simply have a methyl shift from the carbon in blue which would also result in a more stable tertiary carbocation.


texts: My wife made a cleaning solution of isopropyl alchohol (1200mL), baking soda (100 mL) and distilled water(2400 mL). She first mixes baking soda with warm water till it dissolves.  Then adds the isopropyl.  Sometimes, a solid material will form at the bottom of the solution. What is it? It has us confused...


texts: White hot hydrogen gas, like that during a big bang

texts:
Difficult to know for certain which field this is. According to what I can discover about it, the big bang explodes into being as white hot hydrogen gas, millions of degrees hot.

I'm okay with that my question is what colour would it fade to as it cools down? Is there a spectrum I can refer that would illustrate that. I've seen such diagrams for metals as they cool down.

Difficult times people, thank you for your time and input, stay safe. Cheers!


texts: Am I right in giving the following reason for some questions relating to the p-block?

texts:
I'm seeking clarification as I believe this to be the answer to why boron compounds are electron deficient.
While  bonding, the $2s^2$ electrons of Boron are excited to the $2p_y$ orbital, they engage in bonding. However, even after bonding, there exists an empty $2p_z$ which leaves an incomplete shell, thus these compounds require two more electrons and so, they are electron deficient.
(As in the case of $\ce{BCl3}$)
$\ce{CO2}$ cannot put out fire caused by the reaction of saline hydrides and water as it will be converted into formate ions during the process. (although, I'd appreciate some help on chemical equations if possible)

Moreover, if this is accurate, does the same logic apply to $\ce{NH3}$?

Grade 11.


texts: Why is acetyl cyanide not obtained from acetyl chloride?

texts:
Why doesn't acetyl chloride or any other aliphatic acyl chloride react with cyanide ions and undergo nucleophilic addition elimination to form aliphatic acyl cyanide, even though this reaction occurs for aromatic acyl chloride?

This was the related question in my workbook:

  Which of the following compounds will react with ethanolic $\ce{KCN}$?
  A) ethyl chloride B) acetyl chloride C) chlorobenzene D) benzaldehyde

My answer is A, B, D undergoing SN2, nucleophilic addition-elimination, and benzoin condensation respectively.
Answer is given as only A,D.

Searching the internet led me to this article, but I am not able to understand why.


texts:
According to IUPAC, an ion is defined as:

  An atomic or molecular particle having a net electric charge. (source)

But how do you call an atomic or molecular particle that does not have a net electric charge? Is there a noun or an adjective that one can use to refer to the opposite of an ion?


texts: Why are metals conductive in terms of orbitals?

texts:
Back in high school I was taught a definition of metals:

  Metals are a lattice of positive nuclei embedded within a sea of delocalised electrons

Metals are conductive because the electrons aren't bound to any particular atom, and hence can flow freely throughout the entire metal.

However, I was recently taught about electron orbitals, and I'm not sure how to reconcile the two pictures. If the metal atoms were sharing pi or sigma bonds, I'm not sure how any of the electrons could be truly delocalised, and how conductivity arises. In terms of the atomic orbital theory, how does conductivity arise in metals?


texts:
I'm trying to find a substitute of Glucono delta-lactone (GDL). This food additive is usually used to produce silk tofu. Because of its slow hydrolysis the pH decreases very smoothly, which results in a tofu(coagulated soy milk protein) very soft. At the same time it is neutral in flavour, which is a great feature for a food additive. Now, my problem is that I'm trying to find an alternative because GDL is not allowed in organic food (in EU). Does anyone know any possible alternative compatible with the allowed additives (Annex III in:

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:250:0001:0084:EN:PDF)

Or, how can I know the reaction rates of these acidifiers? For example, does Lactic acid hydrolyses slowly?
Note: When I refer to fast or slow, my time reference is a minute (fast) or hours (slow).


texts: Removing titanium from tantalum crucible

texts:
I'm trying to remove titanium filling from a tantalum crucible for a high-temperature effusion cell.  I've managed to get a majority of the material out with tweezers, but some remains and is difficult to remove.  I understand that sulfuric acid will corrode titanium, but not tantalum, and was considering this as a method for extraction.

If anyone has some advice on a method to (safely) remove $\ce{Ti}$ from the $\ce{Ta}$ crucible without destroying it, I would very much appreciate it.  I am certainly not a chemist and could use some help.


texts: How can I measure the pH of high-viscosity fluids like dough?

texts:
I would like to measure the pH value of dough with a pH-Meter, to ensure a pH value of 4.1 (max). Because of the high viscosity I would thin down the dough with demineralized water for two reasons:

I expect more accurate measurements
This reduces pollution of the measurement device.

As far as I understand this will affect the measured value, so I would thin down the dough in a defined ratio of 1:10.

Questions:

Is it correct that the thinning with demineralized water changes the pH value?
The ratio 1:10 should cause an offset of 1 in ph value, right? In which direction? Do I have to add 1.0  to or subtract 1 from the measurement to estimate the real value?

Edit #1

As it seems to be important: We are talking about weak acids produced by fermentation of rye flour (or wheat flour) using sourdough (lactose bacteria + yeast). Some samplings are taken during the fermentation process to check that the pH value is low enough (value of 4.1 or lower).
I'm less interested in the -details- of the theoretical background, more in a practical solution for the issue. The actual real value isn't that important (I need to check, if the pH limit is reached), but it would be interesting how to measure it as there might be future experiments where the value matters...

The use of additional chemicals except (demineralized) water should be avoided for simplicity. Of course the use of tab water would be preferable, but I guess this becomes more complicated because of unknown water hardness and varying ion concentrations.


texts:
I find that there are two contradicting factors at play here:

1) On removing proton, negative charge on oxygen is more stable than it is on nitrogen (because of greater electronegativity of oxygen). Therefore, phenol is more acidic than aniline.

2) +M effect of nitrogen is more than oxygen, so negative charge (after deprotonation) in the case of aniline will be more delocalized making the anion more stable. Therefore, aniline should be more acidic than phenol.

So is that a factual question or am I missing something?


texts: How much D2O is in Vienna Standard Mean Ocean Water?

texts:
I'm curious how much $\ce{D2O}$ (heavy water) is in Vienna Standard Mean Ocean Water. I am interested in $\ce{D2O}$ molecules and not $\ce{HDO}$/$\ce{D+}$/ $\ce{DH2O+}$/$\ce{D2HO+}$/$\ce{D3O+}$ or any other deuterium species or ions. Vienna Standard Mean Ocean Water is pure water extracted from some ocean with a specific isotopic composition. Sweet water has slightly different isotopic composition.
A suitable unit for the result could be mol/kg or a mol fraction.
I'm not sure if temperature or pressure make a difference. I suggest $\pu{20 ^\circ C}$ (or any other temperature, please specify, if possible) and $\pu{101325 Pa}$, but other conditions are ok, too. Liquid water makes most sense, I guess.

Allright, I took some effort as suggested and used my brain ...
2H/1H = 155.76 ± 0.1 ppm (a ratio of 1 part per approximately 6420 parts)1
So if an HDO autoprotolyzed ...
HDO --> D+ + OH- or
HDO --> H+ + OD-
and then D+ or OD- reformed water with OH- or H+, then it would have a 1 in 6420 chance of forming D2O, and so D2O would be 1 in 6420^2=41,216,400 parts.
Sounds good?
1 https://en.wikipedia.org/wiki/Vienna_Standard_Mean_Ocean_Water


texts: How to separate benzyl alcohol and meta-cresol

texts: Benzyl alcohol and meta-cresol boiling point's are not so different, the fractional distillation will be very difficult, what can i do for separate this two composites ?


texts: Why is the first energy of ionization of oxygen lesser than that of nitrogen?

texts:
The following question arises from a question I found in my book.

  Experimentally it has been determined that the value of the first
  energy of ionization of oxygen is lesser than the first energy of
  ionization of nitrogen. Select the statement which explains this:

  The higher electronegativity of oxygen
  The lesser electron affinity of nitrogen
  The lesser radius of oxygen
  The higher stability of nitrogen
  The higher electron affinity of nitrogen

According to my book the answer is the fourth option, but I couldn't find a way to justify this. What sort of explanation can do this?.

My guess is that nitrogen forms a triple bond with itself which is higher than the oxygen and this makes the molecule more stable but I don't know if this can be translated into a higher energy of ionization nitrogen rather than the oxygen which does have a sigma and pi bonds. Am I right?

Can someone please illustrate this or bring some sort of diagram with some values to justify this?. It would help a lot if an answer could help me why should I discard the second option?.

Doesn't nitrogen has smaller electron affinity than the oxygen? Wouldn't it mean that having a smaller electron affinity cause it to be easier to strip out an electron from its outer shell rather than the opposite as the question indicates?


texts: Effect of pressure on viscosity of liquids and gases

texts:
My textbook says the following on viscosity and pressure:

  increase in pressure decreases the viscosity of water but for other liquids it increases. Viscosity of gases does not change much

No further explanation is provided.

I have two doubts regarding this:

How does the viscosity of water decrease? Does it have something to do with the anomalous expansion of water?
How does the viscosity of gases not change much on increasing the pressure? The gas molecules should have an increase in kinetic energy, contributing to more collisions and hence more viscosity


texts:
Why is the maximum theoretical efficiency of Ar engine higher than that of Nitrogen engine? On a molecular level.

For an Otto Cycle

$\mathrm{Eff} \le\left(1-r^{1-\gamma}\right)$
$\gamma=\dfrac{C_p}{C_v}$
$r=\dfrac{v_1}{v_2}$

Sys. Fluid

Nitrogen, $\gamma=1.4,\ r=10,\ \mathrm{eff(max)}=60.2%$
Argon, $\gamma=1.67,\ r=10,\ \mathrm{eff(max)}=78.5%$


texts: How can diamond have a fixed refractive index?

texts:
I was doing a lesson on solid states. There were given two kinds of solids namely amorphous solids and crystalline solids. Some differences between these two solids were given in my book. One of the difference was that crystalline solids are anisotropic in nature whereas amorphous solids are isotropic in nature.
Following is from my book

Crystalline solids are anisotropic in nature, that is, some of their physical properties like electrical resistance or refractive index show different values when measured along different directions in the same crystals.

Diamond is a crystalline solid. That means it is anisotropic in nature. This means that measuring the refractive index of diamond from different direction will give different values of refractive index. Then why we have fixed value of refractive index of diamond.
Not just about diamonds, many other crystalline solids have fixed refractive index.


texts: Why is it that all strong bases contain at least one hydroxide bond? What is going on here at the chemical level? For example, we know that $\ce{NaOH}$ is a strong base. I know it is strong because it completely dissociates in water. And under the Bronsted-Lowry definition of bases, I know that is is considered a base because it accepts a proton. So what is it about having a hydroxide bond specifically that lets it dissociate?


texts: How do I print property matrices in Avogadro?

texts:
I'd like to print the content of property matrices (i.e., the matrices shown after selecting View→Properties→X where X is one of the six options shown, including Angle properties..., Atom properties... and Bond properties...) in Avogadro, but I can't seem to find this option at Avogadro Wiki or other forms of Avogadro documentation.

e.g. this is the bond properties matrix.


texts: Chemical kinetics of a reaction, rate constant, and activation energy

texts:
From the Arrhenius equation in kinetics of reactions,

$$k = A\exp{\left(-\frac{E_\mathrm{a}}{RT}\right)}$$

Which tells us about the temperature dependence on rate constant of a reaction.

Activation energy is dependent on the temperature (as it is the energy difference between the average energy of the reactants and threshold energy, and since the average energy of reactants depends on the temperature, activation energy also should depend on temperature) Is my assumption that activation energy depends on temperature correct?

Moreover, is there any case where activation energy is zero or negative? (like in the case of spontaneous reaction or $E_\mathrm{a} = 0$) I feel that whenever activation energy is zero, all the molecules undergoing collisions should form products successfully, but this case won't occur.

But when we substitute $E_\mathrm{a} = 0$, in the Arrhenius equation, we get the result as $k = A$, i.e. rate constant will be equal to pre-exponential factor.


texts: What reaction happens when carboxylic acids are treated with calcium hydroxide and distilled?

texts: What reaction takes place when $\ce{Ca(OH)2}$ reacts with $\ce{R-COOH}$? What is obtained after distillation?


texts: Ionize Hydrogen and Oxygen Gas in Electrolytic Cell?

texts: As is well known, water can be electrolyzed into oxygen and hydrogen gasses. However, all redox reactions can be run in reverse. If I were to electrolyze water in 2 closed containers (in order to trap the gasses) and i were to run the cell in reverse using a battery, would the hydrogen and oxygen gasses turn back into ions and, therefore, water? If so how would this work on a physical level? And what path do the ions take to get to each other?


texts: Can a reaction with positive Gibbs free energy change ever occur?

texts: If you have an endothermic reaction with a negative entropy change, is it still possible to induce the reaction in some way despite the fact that the Gibbs free energy change is positive or all temperatures?


texts:
Are there compounds that are rings of non-carbon atoms, say a ring of six oxygen atoms, or 5-6 nitrogen atoms with attached hydrogens?
Or are these too unstable to exist for long (if at all), like long oxygen chains ($\ce{HO_{n}H}$)?


texts: What is the direction of charge transfer between Aluminum and aliphatic amines physisorbed on top?

texts:
Is there dipole formation upon physisorption of an aliphatic amine to an aluminum substrate? What is the charge transfer direction? What if the aluminum substrate is clean, surface oxidized or covered with -OH groups?
What if aluminum is replaced by other types of metals, such as Au and Ag?


texts: Why lattice constant (unit cell) is always a parallelepiped?

texts:
Wikipedia defines lattice constant as physical dimension of unit cells in a crystal lattice.

Unit cell is defined as:

  The unit cell is defined as the smallest repeating unit having the
  full symmetry of the crystal structure. The geometry of the unit
  cell is defined as a parallelepiped.

Why that elementary pattern that repeats itself in crystals is always a parallelepiped? In real life such elementary repeating unit/part/block is very often not a parallelepiped at all!

Is this some abstraction and a "bounding parallelepiped" is meant - the one into which definitely fits whatever real elementary repeating pattern is?


texts: What is the reaction between a copper anode and a zinc cathode?

texts: I prepared a battery with $\ce{Zn}$ screws and a $\ce{Cu}$ wire, with water as an electrolyte. The $\ce{Zn}$ screw acted as the cathode, and the $\ce{Cu}$ wire acted as the anode. I got nearly $0.6\:\mathrm{V}$ as the emf. I placed numerous amounts of such cells in an ice cube tray. Each ice cube acts as a cell and i got nearly $6\:\mathrm{V}$ of emf. What is the reaction happening here? What is the reaction involved with the electrodes and the electrolytes?


texts: What is the reason behind neglecting & putting the overlap integrals $0$ in Simple Hückel Theory?

texts:
This is an excerpt about Simple Hückel Theory from Elements of Physical Chemistry by Peter Atkins:

  The first step that Hückel took was to ignore the $\sigma$-bonding framework and focus solely on the $\pi$ electrons. That is, he assumed that the atoms had taken up the positions they have in the actual molecule, then calculated the properties of the $\pi$ orbitals that matched that framework.

  [...] we show in Derivation 14.3 that the Schrödinger equation for the orbitals $\hat H \psi = E\psi\;,$ then becomes the following pair of simultaneous equations for the coefficients: $$(H_{AA}- E)c_A- (H_{AB}- ES)c_B= 0\\ (H_{BA}- ES)c_A+ (H_{BB}- E)c_B= 0$$ ... . These equations are called the secular equations.

  Hückel then made further approximations. First he neglected all the overlap integrals and set $S= 0$ wherever it appear. .....

I didn't quite get why he made this approximation. There must be some reason for neglecting the overlap integral, I suppose. Also, Atkins didn't mention why Hückel only made calculations for $\pi$ orbitals only; does his equations not work for $\sigma$-bonding?

So my questions are:

$\bullet$ What is(are) the reason(s) behind making the approximation of putting all the overlap integrals $0\;?$ After all, making $S= 0$ would mean there is no overlap.

$\bullet$ Why did Hückel work only on $\pi$ orbital? Doesn't his calculation work for $\sigma$-bonding?


texts: Why does enthalpy change differ in a chemical reaction because of temperature?

texts:
If enthalpy is a state function, shouldn't the change in enthalpy be the same between a given initial and final state, regardless of how the change took place? Kirchoff's equation describes this variation as
$$\Delta H_{T_2} = \Delta H_{T_1} + \Delta C_p (T_2 - T_1).$$
I'm guessing that this change in enthalpy change is only because of the variation in $C_p$, but I'm not too sure about it. Am I completely wrong about this?


texts: Acid/Base dissociation constants relationship

texts:
From what I understand, the concentration of hydronium and hydroxide molecules is constant in pure water (and equals $10^{-7}\ \text{M}$, which is measured experimentally).

What I don't understand is why this remains true for an aqueous solution with an acid or base in it. Shouldn't it affect these concentrations?

When you write the equilibrium reactions for a weak/weak acid/base pairs (one with its conjugate), and get that $K_\mathrm a\cdot K_\mathrm b = [\ce{H+}][\ce{OH- }]$, what's the explanation for it? Why does their multiplication (either as pure water or in a acidic/basic solution) remain constant?


texts:
This is for my AP Chemistry course and the question is:

Which of the following elements is important in the semiconductor industry to improve the conductivity of Ge?

K
Ga
Al
Mg

It seems like any of the above could be a correct answer. The answer given was Ga. What about gallium would make it the most appropriate answer?


texts: Preparation of sulfuric acid through Contact process

texts:
In the preparation of $\ce{H2SO4}$ through the Contact process, $\ce{H2SO4}$ is added to hot sulfur trioxide to form oleum. This oleum is then diluted by adding water to form $\ce{H2SO4}$.

$$\ce{H2SO4(l) + SO3(g) → H2S2O7(l)}$$

$$\ce{H2S2O7(l) + H2O(l) → 2 H2SO4(l)}$$

In a preparatory reaction, different reagents are used to obtain the desired product but here the product is itself a reactant and is used to make the product. Indirectly, $\ce{H2SO4}$ is being used to make $\ce{H2SO4}$.

Would this process be called as a preparation process?


texts:
I work for a company that manufactures pyrotechnics for the oil and gas industry, and we have been having an odd phenomenon occur.

One part, a brass tube with a copper clip filled with black powder, is placed into a steel receptacle. Another part, consisting of a blend of black powder, asphalt, epoxy, and a little ammonium nitrate (and possibly a few other materials) in a steel tube is placed into the same atmospheric chamber, but does not come in physical contact with the first part. The chamber is sealed up, and the brass tube is covered in blue corrosion within minutes. I don't think that the second part is offgasing, because it's in a sealed package prior to use which never builds up any pressure. What could be causing it to corrode so fast? I think the customers are using a caustic cleaner in the tool which isn't being fully removed that's reacting with the brass, but they seem to think it's an interaction between the two tools. Any thoughts?


texts: How to mitigate salicylic acid saponification?

texts:
I started to make soap a few months ago and came up with a few formulas, one of it contains salicylic acid as a exfoliant/anti-acne agent, I've just realized that since salicylic acid is, well, an acid, and sodium hydroxide a base they will react together to form sodium salycilate, which doesn't have the required properties.
I add the salicylic acid and the other agents at (really) thick trace, when the saponification reaction is quite advanced but not complete, actually I couldn't find any data on how far the reaction has completed at this stage (if anyone knows this is always good to know).
Is there any way (besides waiting for reaction completion) to keep the NaOH reacting with triglycerides instead of starting reacting with the salicylic acid?
Is this even necessary?
I mean I know some reactions will be more likely to form a product or another depending on the amount of one of the reactants, like the reaction between salicylic acid and NaOH will give either sodium salicylate or disodium salicylate depending on how much NaOH is available (how is called this phenomenon by the way?), so maybe the unreacted NaOH will be that low at the time I add the salicylic acid it won't react with it at all or so little that there's nothing to be worried about.
What do you think?


texts: Reaction of an alkyl halide with silver nitrite

texts: I want to know that whether both alkyl nitrite and nito alkane are produced or if nitroalkane is the only product. There are many different (contradicting) things written in different books that is confusing me.


texts: Finding percentage of the gas in a binary gaseous mixture of the given density

texts:
At STP, the density of a gas in a vessel is $0.9002$. If the gas is a mixture of argon and helium, what percentage of the gas is argon?

I am stuck on this. From what I can gather, the only influencing characters would be moles and grams. This idea is based of off of STP and given constants.

I have a couple equations written down but I can’t seem to the flow going.

R, T, P are all known along with acccording densities. I also want to say $22.4$ is also a known at $V_\mathrm{tot}$ and therefore $n_\mathrm{tot} = 1$.

$$n(\ce{Ar}) + n(\ce{He}) = 1$$

$$\frac{n(\ce{Ar})}{n(\ce{Ar}) + n(\ce{He})}d(\ce{Ar}) + \frac{n(\ce{He})}{n(\ce{Ar}) + n(\ce{He})}d(\ce{He}) = d_\mathrm{tot}$$

$$d = PM/RT$$


texts: Can bone mineral be obtained in pure, crystalline form?

texts: Can bone mineral be obtained in pure, crystalline form outside a living organism? Had this been done ever?


texts: What are the fragments that result from taking the Mass Spectrum of o-fluronitrobenzene?

texts:
I am doing my online lab, and we are on mass spec right now. I am having a very tough time figuring out the shape of the fragments of o-fluronitrobenzene, especially the large peaks. Especially the one at 75, 83, and 111. I have been drawing fragmentation diagrams for a while now, but have come no closer to understanding what those fragments actually look like.
I am fairly confident that the peak at 95 is a phenyl ion after the loss of entire nitro group. Also, the small peak at 125 also suggests the fragmentation of simply the nitrogroup(after the loss of the oxygen radical), which results in the cation being squarely on the Nitrogen. Although I am confused why the peak is relatively small. I suspect it is to do with the unfavorable oxygen radical being produced. My understanding is that if a compound is nitrogen contaning, that it will give a odd mass on the spectrum.
However, I think that it would not apply in this case as the nitrogen is bonded to two oxygen(both even), and the benzene give us all even masses. The only other odd mass atom would be the 19 Fluorine. It is my suspicion that the 75, 83, 111 peaks all do contain fluorine to some extent. I am just confused on how the fragmentation would lead to the masses with the fluorine on it. I know it contains fluorine, and most likely not a lot of the nitro group.


texts: Why is the equilibrium constant of water with its vapour equivalent to its vapour pressure?

texts:
Can someone conceptually explain why the equilibrium constant is equivalent to the vapour pressure of water for the above equilibrium reaction?

For example if $K = x$, then it is said that vapour pressure $= x$ (in bars). However I seem to cannot understand why.


texts: Will electric field make organic matters (e.g. glucose) ionize in water?

texts:
After reviewing this post, I have a new question regarding ionization and dissolution.

If applying a strong electric field (DC or AC) in a water solution, will the electric field ionize the organic matters that are not ionizable? For example, an electric field makes $\ce{CH3COOH}$ ionize more? Or makes glucose ionized in water instead of forming hydrogen bonding with the water molecular? Thanks.


texts: Why is the lone pair of pyridine's nitrogen atom not part of the aromatic ring?

texts:
In pyrrole, the lone pair of electrons belonging to the nitrogen is part of the aromatic ring. However, in pyridine it is part of an sp2-hybridized orbital. Why can't it be in the p-orbital and take part in the aromatic ring?

I mean, why can't the lone pair in pyrrole be in the p-orbital, with the sp2-hybridized orbital (which is not bonded to anything) sporting a single electron?

I'm not talking about the nitrogen atom having two p-orbitals participating in the aromatic ring. That would be strange. I wonder why the existing p-orbital of N cannot carry two electrons, the way it does in pyrrole.

P.S. A related question, with a very interesting answer: sp2-hybpidization in pyridine and pyrrole


texts: Is there a danger in electrolyzing NaCl?

texts:
To make $\ce{NaOH}$ one could electrolyze a solution of $\ce{NaCl}$ in water ($\ce{H2O}$) It would go like this:

$$\ce{2H2O_{(l)} + 2Cl-_{(aq)} + 2Na+_{(aq)} -> H2_{(g)} + Cl2_{(g)} + Na+_{(aq)} + 2OH-_{(aq)}}$$

After calculating a bit, I found that even just a few minutes of electrolyzing this at $10\ \mathrm{A}$ could be deadly.

Can anybody confirm this?


texts: Is there a way to calculate how fast water will cool?

texts: Is there a way to calculate how fast water will cool if you know the water's starting temperature and temperature of the environment that you put it in, such as a freezer?


texts: Synthesise the CBZ derivative of glycine from glycine and benzyl chloroformate

texts:
Question
  The benzyloxycarbonyl group (CBZ) is widely used to protect amines, especially in aminoacid chemistry. A procedure to synthesise the CBZ derivative of glycine from glycine and benzyl chloroformate is given in the description below.

  Glycine ($0.1~\mathrm{mol}$) was dissolved in aqueous sodium hydroxide ($50~\mathrm{mL}$ of a $2~\mathrm{M}$ solution)
  and the solution was cooled in an ice bath. Benzyl chloroformate ($1.2~
\mathrm{eq}$) and aqueous
  sodium hydroxide ($25~\mathrm{mL}$ of a $4~\mathrm{M}$ solution) were added dropwise simultaneously to the
  glycine solution at $0°\mathrm{C}$ dropwise over thirty minutes. The mixture was stirred for an extra
  ten minutes, then warmed to room temperature. The solution was extracted twice with
  ether. The combined organic layers were acidified to $\mathrm{pH}=1$. The precipitate was filtered,
  washed with a little cold water and dried to give carbobenzoxyglycine ($18.5~\mathrm{g}$), m.p. $119-120°\mathrm{C}$.

  (a) Relative to glycine, how many equivalents of sodium hydroxide are used in this reaction? Explain why this number was used.

  (b) Can sodium carbonate ($\ce{Na2CO3}$) be used in place
  of sodium hydroxide? Explain why it can or cannot be used.

  (c) What inorganic by-product will be formed (write its chemical name)?

  (d) The procedure given includes a serious mistake, which would result in a yield of $0\%$.
  What is the mistake, and how might it be corrected?

My answers

(a) I mentioned $1~\mathrm{eq}$ of sodium hydroxide as sodium hydroxide reacts with glycine in a 1:1 ratio.

(b) I mentioned that sodium carbonate cannot be used in place of sodium hydroxide as sodium Carbonate is not basic enough to catalyst the reaction.

(c) Sodium chloride

(d) I mentioned that during the process when the combined organic layers were acidified to $\mathrm{pH}=1$, it could destroy the product by hydrolysing it hence giving a yield of $0\%$.

I'm unsure whether my answers are correct though, could anyone explain? Also, are there any resources on the web that contain practice questions of a similar nature to this?


texts: Will changing the salt in the salt bridge change the voltage produced in a galvanic cell?

texts:
I have used zinc sulfate and copper sulfate as the solutions, and used zinc and copper electrodes.
For salt bridge I took lithium, potassium, calcium, sodium and zinc nitrates. The results are as below:
$$
\begin{array}{lr}
\hline
\text{Compound} & E_\mathrm{cell}/\pu{V} \\
\hline
\ce{LiNO3}    & 1.081 \\
\ce{NaNO3}    & 1.057 \\
\ce{KNO3}     & 1.071 \\
\ce{Ca(NO3)2} & 1.069 \\
\ce{Zn(NO3)2} & 1.071 \\
\hline
\end{array}
$$
As it shows, there is very insignificant difference. Is the results supposed to be like this or have I done something wrong in my experiment or something so that the voltage was constant?
If I have done something wrong, then should I have changed the anions instead of the cations? Or would it have been a mechanical problem?


texts: How much oxygen is used up by the browning of an apple?

texts:
This is inspired by a recent popular question on Cooking.
Let's assume that I take some apples, cut them up, and place them in a hermetically sealed container. Then the container goes into the fridge. The apple pieces will start to get brown, because some of the apple molecules are reacting with oxygen (enzymatic browning). Obviously, since the container is now sealed, this reduces the total amount of oxygen in the container.
Now I had an interesting discussion in comments with another user - their intuition told them that this browning reaction will use up the oxygen so quickly that the apple will brown less than when held in a place with a normal atmosphere. My intuition went to the other direction - that so little oxygen will be used up, that the apple will brown as much as when exposed to unlimited quantities of air. I tried to look up some numbers, but didn't trust my rusty high-schoo-chemistry knowledge enough even for back-of-the-envelope calculations. So here my question: how much of the oxygen will be used up? Especially, will browning stop earlier than with unlimited air?
An interesting side question would be: if the browning does use up significant amounts of oxygen, which will stop the browning first, the system running out of oxygen, or the system running out of the necessary enzymes? But that's an optional question, since getting data on the enzymes may be too complicated.
I am aware that there are too many degrees of freedom for an exact answer. I am perfectly happy with an answer which describes the magnitude of the effect in a way that is easy to grasp, or gives a range for the expected oxygen concentration (even if it's a wide range). To make it more answerable, here are some assumptions:

let's define a container with 100 g of apple and 100 ml air
since I expect that only molecules on the apple's surface will react, I would be interested in a discussion of the two possible extremes - either an apple cut in half (let's assume that's 40 cm^2) or an apple hacked into many small pieces for maximum surface, but not pureed (I don't know how to calculate the surface, does chemistry offer a formula for the minimum particle size before air stops being able to flow through the particles?)
the container is held at 4 Celsius (I hope we can ignore the time in which it cools down from kitchen temperature - but it is filled at kitchen temperature, I don't know if the effect on the total amount of oxygen is significant)
we can keep the apple for a maximum of 5 days before we declare it inedible
we are not using any methods to slow down browning. Just cut the apple, close the container, let it sit undisturbed.
I found a source measuring the amount of phenolic compounds in apples: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4665438/#:~:text=In%20general%2C%20the%20polyphenolic%20contents,per%20apple)%20%5B22%5D. As far as I can tell, the relevant measurement is the 75.7 to 93.0 mg of total phenolic compounds per 100 g of apple flesh, so let's round to 80 (I'm somewhat puzzled by the abbreviation GAE, maybe you know what it is?). I am aware that it lists many different compounds, but I hope that the reactions they do use up a relatively similar number of oxygen atoms, up to a small numeric constant (so maybe compound A reacts with 2 atoms of oxygen and compound B with 3 atoms), so that should be enough for estimating a range.


texts: Can 4-aminophenol be used to produce 2,5-cyclohexadien-1-imine?

texts:
If the hydroxl group on 4-aminophenol was protonated by a strong acid in aqueous solution, and the compound further to that dehydrated, could a rearrangement of the subsequent carbocation lead to formation of 2,5-cyclohexadien-1-imine and thus regenertion of the strong acid before SN1 was possible?

Is there a more common name for this sort of reaction (assuming it is possible)?


texts: What are the applications of tetraxenonogold(II)?

texts:
I recently stumbled upon a pretty interesting chemical: tetraxenonogold(II) $\ce{AuXe4^2+}.$ Basically, an atom of gold with four xenons around. It is a product of a superacid reaction and it is interesting because both gold and xenon are quite inert elements.
What could be the application of such a molecule? It reminds me of some cancerostatic compounds.


texts: The chemical reaction between lemon juice and polystyrene foam cups

texts:
I have noticed that when I have lemon juice on my fingers and I touch a polystyrene foam cup (I will refrain from using the term 'styrofoam'), the cup begins to break down, i.e., melt. I can leave fingerprints on the cup in this manner. What is it about lemon juice and foam cups? What is happening, other than what I see; the cup melting.

I have never tried replicating this using other citric acids, such as an orange. So, I don't know yet if it's just lemon juice that will do this.


texts: How do I find the theoretical pH of a buffer solution after HCl and NaOH were added, separately?

texts:
This question is about the theoretical pH of a buffer solution.

  Calculate the theoretical pH values expected for a $\pu{200mL}$ buffer solution containing a 1:1 ratio of acetic acid and sodium acetate (their concentrations are $\pu{0.05M}$), following the addition of;

  $\pu{10mL}$ of $\pu{0.2M}$ $\ce{HCl}$ and
  $\pu{10mL}$ of $\pu{0.2M}$ $\ce{NaOH}$.

  $K_\mathrm{a}$ of acetic acid is given.

So I just found the $\mathrm{p}K_\mathrm{a}$ for the Henderson equation.

Attempt for (1):

$\ce{[HCl]}$ = $\pu{0.2M}$ and $V=\pu{10mL}$/$\pu{0.01L}$ thus $n = 0.002 $

$0.002 \times \pu{0.2L} = \pu{0.01M}$

ICE table:

$$
\begin{array}{cccc}
&\ce{H3O+ + &CH3COONa <=> &CH3COOH + &H2O}\\
\text{I}&   x& 0.05&0.05\\
\text{C}& -0.01&-0.01&+0.01\\
\text{E}& x - 0.0&0.04&0.06\\
\end{array}
$$

$\mathrm{pH} = 4.74 + \log (0.06/0.04) = 4.926$

Although in our experiments the actual pH was 4.17 after $\pu{10mL}$ of $\ce{HCl}$ was added and the pH after 10 mL of NaOH was 4.98

Attempt for b:

$\ce{[NaOH]} = \pu{0.2M}$ and $V = \pu{10mL}/\pu{0.01L}$ thus $n= 0.002$

$0.002 \times \pu{0.2L} = \pu{0.01M}$

Is this how I would properly set it out?

$$
\begin{array}{cccc}
&\ce{CH3COOH + &OH- &<=> &CH3COONa + H2O}\\
\text{I}& 0.05&x&&0.05\\
\text{C}& -0.01&x-0.01&&+0.01\\
\text{E}& -&0.04&&0.06\\
\end{array}
$$

$\mathrm{pH} = 4.74 + \log(0.04/0.06)= 3.74$

So I feel like I have done these the wrong way because it makes more sense but I don't know why or how.


texts: Is it true that an evaporating molecule has the same kinetic energy as a molecule in a pot of boiling water?

texts:
A molecule on the surface of room-temperature water shoots off the surface of said water, or in other words, it "evaporates." It does so because it gained kinetic energy ${x}$, and ${x}$ was great enough to counteract the pressure of the air surrounding it.

Is it true that this ${x}$ would be similar (the same or greater) as the average kinetic energy level of a molecule in a pot of boiling water?

Reasoning for thinking this: boiling is when the vapor pressure = the pressure of the atmosphere.


texts: Why does standard reduction potential get multiplied by the change in oxidation state and not by the number of electrons transferred?

texts:
The whole basis of Frost diagrams is to have a graphical representation of the Gibbs free energy of formation ($\Delta{G}_{f}$) of different oxidation states of an element using the proportional relation between Gibbs free energy and standard reduction potential:

$\Delta$$G$ = $-nFE^{o}$

From which we can derive:

$\frac{{-}\Delta{G}}{F}$ = $nE^{o}$

Thus, if we graph $nE^{o}$ against the oxidation number (N), we can accurately describe the relationship between oxidation state and ($\Delta{G}_{f}$).

I encountered a problem in Shriver's Inorganic Chemistry that asks to draw the Frost diagram of oxygen from its Latimer diagram.

Construct a Frost diagram for oxygen from the Latimer diagram below.

I initially though that we would use the standard reduction equations below, which give $nE^{o}$ as $-1.36V$ ($-2$ times $0.68V$) for $\ce{H2O2}$ and $-4.92V$ ($-4$ times $1.23V$) for $\ce{H2O}$.

$\ce{O2(g) + 2H+ (aq) + 2e- -> H2O2 (aq)}$  $E^{o}$=$+0.68V$
$\ce{O2(g) + 4H+(aq) + 4e- -> 2H2O(l)}$  $E^{o}$=$+1.23V$

However, the book seems to be using the change in the oxidation number of oxygen to calculate $nE^{o}$ for $\ce{H2O2}$ and $\ce{H2O}$.

Online images of Frost diagrams corroborate this calculation.

Why is the change in oxidation state used as the standard to calculate $nE^{o}$ instead of the number of electrons transferred given that $n$ in $nE^{o}$ is the number of electrons transferred?
References
Shriver, D. F., Weller, M. T., Overton, T., Rourke, J., & Armstrong, F. A. (2014). Inorganic chemistry 6th Edition.


texts:
I'm dealing with a voltaic cell constructed like this:

(From “Electrochemistry”, chapter 19 from the book Principles of General Chemistry (v. 1.0).)

I understand that as oxidation occurs at the $\ce{Zn}$ electrode, the electrode loses mass as $\ce{Zn}$ dissolves into $\ce{Zn^{2+}}$ in the solution and eventually will bond with $\ce{Cl-}$ coming from the salt bridge. But on the $\ce{Cu}$ cathode side, how could it gain mass if initially the $\ce{Cu}$ electrode lost mass after the $\ce{Cu^{2+}}$ ions dissolved in the solution? I get that the $\ce{Cu^{(2+)}}$ ions are re-attracted to the $\ce{Cu}$ electrode once electrons flow from anode to cathode, but wouldn't that mean that the $\ce{Cu}$ will retain the same mass once the cell is complete?


texts: Which melting point would indicate a metallic structure?

texts:
Question
  If you have three substances with three different melting points;

  445 °C
  1907 °C
  -7 °C

  Which of these would most likely have a metallic structure?

I understand that the third option would most likely be covalent. But between the first and second option, there are many bonds which have a similar melting point to both answers. Which of these would most likely indicate a metallic strucure to be involved.


texts: Does the dipole moment increase or decrease by increasing the bond length?

texts:
It is established the dipole moment is a result of multiplication of the magnitude of charges (Q) and the distance between them (r). What I understand is that when an electron and a proton get closer (bond length decreases), polarity decreases hence the dipole decreases. When they move further away from each other(bond length increases), the polarity increases and hence the dipole moment increases. However, in case of halides (H-X), let's take for example HF and HI, HF has a bigger dipole moment than HI, it is stated that the bond length of HF is smaller than HI. Why do I find this contradictory?
Can you help me with What I am missing here?


texts:
My chemistry teacher taught us that one of the ways to see if we had produced ammonia gas in a reaction was if it released a pungent smell (Even BBC supported that here! http://www.bbc.co.uk/schools/gcsebitesize/science/triple_edexcel/qualitative_analysis/qualitative_analysis/revision/3/ ). However, as far as I knew, Ammonia was poisonous. Is it okay to breathe in small amounts of Ammonia, or is this a hazardous practice that can potentially harm us?

This question What chemical compounds used in qualitative chemistry can be distinguished by smell? did say that Ammonia could harm you, but it doesn't say how much is needed to cause the damage, which is a big part of my question.

Thanks!


texts: Is there a liquid that looks like water but boils at a low temperature?

texts:
I just watched a movie where someone put their hand into boiling water. Disregarding how this was actually done, I wondered whether there was a liquid which could be used for an illusion of someone "putting their hand into boiling water".

For this it would have to look like water, boil at a comfortable temperature (< 50 degree celsius) and should not be so toxic that you can't put your hand into it. Smell doesn't matter.

Is there some liquid that fulfils these requirements?


texts:
I was reading an article:

  We first compared experimental (S 2 exp) and computed (S 2 calc) side-chain order parameters using the simplest approximation of side-chain conformational variability, where motions are only allowed within the rotamer well of the side-chain conformation observed in the crystal structure

Now I am wondering what side-chain order parameters are.


texts: Why is an alkyne substituent on benzene is electron withdrawing, but alkane and alkene are electron donating?

texts:
Hammett constants for alkyls/vinyls/etc. are all negative (i.e. toluene), and my understanding is that they donate electrons through inductive/resonance effects.

However, ethynylbenzene has a positive Hammett constant, and I am unsure how to rationalise this in terms of induction/resonance (or whatever other effects that might be responsible for this).


texts: Time dependence of integrated rate equations

texts:
Is it possible for an integrated rate equation to not be dependent on time? What law or principle says so in chemical kinetics?

What if an integrated rate equation obtained only depends on the concentrations of the reactants? Is it possible? Can you refer me to books and references?

By definition, an integrated rate equation shows the change in concentration as a function of the progress of the reaction (time). So I don't understand why professor insists that an integrated rate equation can exist without having the variable time in it.


texts: Why does the ionization enthalpy of elements across a period not follow a regular pattern while the atomic size always decreases?

texts:
First of all, I would like to mention that I am only talking about elements that aren't from the d or f blocks.
In order to further elaborate on my question, I would like to take the third period as an example.

As we can see, the atomic radii decrease across a period constantly, whereas the ionization energies increase and decrease depending on the element. I just fail to understand how this can be. As far as my understanding goes, isn't work done against the electric field to remove the electron called ionization energy? And if this is true, then it must mean that the closer an electron is to the nucleus, the stronger the force of attraction experienced by it would be, which would in turn translate into a higher ionization energy. However, we can see that this does not seem to be the case. I would really appreciate it if someone could tell me where I'm going wrong and why this is the case.


texts: Spontaneous/Non-Spontaneous Reactions and Reversible Reactions

texts:
My chemistry textbook states "Reversible reactions constitute a limiting case between spontaneous and non-spontaneous processes."

Does this mean that some of the reversible reactions are spontaneous and others are not? Or that the reversible reactions are sort of intermediary between said two types of reactions? Or something else?


texts: Are coefficients in a reaction taken as the exponents in the rate law expression?

texts:
In my book it is written that if we have an reaction equation such that
$$\ce{a A (g) + b B(g) + c C(g) -> product}$$
The rate expression of the reaction will be
$$R = k[\ce{A}]^a [\ce{B}]^b [\ce{C}]^c.$$

But, when I researched on expression of rate law, I understood that $a$, $b$ and $c$ are not coefficients of the reaction. But, in most part of my book, the coefficients are taken as the powers $a$, $b$ and $c$.

Is my book wrong or is there something that I don't know about rate expression?


texts: Why are negative enthalpies becoming more positive described as decreasing?

texts:
This website and my lecturer have describe negative enthalpies that are becoming less exothermic as decreasing. A relevant diagram from the linked to website to illustrate what I mean:

I see the enthalpy of hydration is decreasing in magnitude but it is becoming more positive so why is it said to decrease? Is this a convention of some sort?


texts: What chemical should I use to thin UV cure epoxy?

texts: The epoxy that I am working with is UV curable with a cycloaliphatic epoxy resin base. I am trying to reduce the viscosity. Whatever I add to thin the epoxy, it needs to be able to evaporate off so that when I cure it, it's just the epoxy remaining. I have used solvents like acetone to thin 2 part thermal cure epoxies, but I am not sure if this is appropriate for a UV cure epoxy or which solvent would be best to use.


texts: What is the relationship between configuration & optical rotation?

texts: Is there a clear cut rule between the two? For example, is R always (+), or is S always (-), or is there no relationship? And if so, why? Wouldn't it make sense that plane polarized light would rotate in the direction ascribed to chiral molecules?


texts:
I want to ask a question about the multiplication of two variables and the error associated with the process.

I was learning about calculating errors in the physical labs at school and was taught that the following formula was used to calculate errors:

  $\frac{\triangle Z}{Z} = \frac{\triangle A}{A} + \frac{\triangle B}{B}$

This made sense, given that we are in essence calculating percentage uncertainties and these are added when calculating the uncertainty of Z.

However, in my current undergraduate lab, we square each term:

  $(\frac{\triangle Z}{Z})^2 = (\frac{\triangle A}{A})^2 + (\frac{\triangle B}{B})^2$

and I cannot find any reference to explain the purpose of squaring the values.

Why do we square each term as above?


texts: Are these molecular structures enantiomers or diastereomers?

texts:
What relationship exists between the two structures shown?

I think that since the configuration at the bridge head carbons remains the same and only there is an inversion at the carbon bearing $\ce{Ph}$ group, the above two structures should be diastereomers, but these are mentioned to be enantiomers in a book.
So, are these enantiomers or diastereomers?


texts: Why is CO2 more likely to dissolve in a basic solution than an acidic solution?

texts: I'm having trouble thinking through this problem. I know that when $\ce{CO2}$ dissolves in water it can release $\ce{HCO3-}$ and $\ce{H+}$ and cause a drop in pH. But can I use this to justify why $\ce{CO2}$ (g) might dissolve more easily in a basic solution than an acidic one? Is the water acting as the base?


texts: Several carbonyl groups, which one does ethylene glycol protect?

texts:
We know that ethylene glycol is used to protect carbonyl functional groups. But, consider this:

Here, we have two carbonyl groups, but only one equivalent of ethylene glycol. Obviously, only one carbonyl group will get protected in this case. But will it be the $\ce{C}^1$ or $\ce{C}^2$ carbonyl? And why?


texts: How report metal amounts as amount of their respective metal oxides?

texts:
I have performed an element analysis, and I I have calculated the amount of each metal in my sample, given in milligrams. Let's say I weighed in 10 mg of the powder. I want to see how much of that I have accounted for by the major components in my sample (those > 1-2 %).

Since my metals were not free metals in my sample, but rather as various oxides, I need to convert back to the most common oxides. This is the idea:

  If I have 1 mg $\ce{Mn}$ in my sample, how many milligrams would that be if I
  have $\ce{MnO2}$ instead?

Should I use the number of atoms? Like this:

I have 0.002648 g of $\ce{Mn}$ = 4.82×10-5 moles = 2.90×1019 atoms. I then assume I have 2.90×1019 molecules of $\ce{MnO2}$. Going backwards, this gives me 4.815×10-5 moles = 4.187 mg. Would this be the correct way of doing it?


texts: Regarding change in temperature in Bomb Caloriemeter

texts:
In a Bomb Calorimeter, we measure the change in temperature of water $\Delta T$. But when it comes to calculating the change in internal energy we use $$\Delta U = C_{cal}\Delta T$$ Where $C_{cal}$ is the specific heat capacity of the whole calorimeter. Why is that? What I mean is that we're measuring the change in temperature of the water and assuming that heat from the reaction transferred completely to water, so shouldn't we apply $$\Delta U = C_{water}\Delta T$$ since we're calculating the change in temperature of the water?
Or are we assuming that the change in temperature of the water is the change in temperature of every element in the calorimeter?


texts: Mechanism for removal of pesticides from fruit by sodium bicarbonate

texts:
When Googling around for methods to remove pesticides from fruits and vegetables, a study commonly referred to from some news sites (e.g. here and here ) is one where soaking apples in a sodium bicarbonate solution was shown to effectively remove pesticides (the study was conducted using the pesticides phosmet and thiabendazole), more effectively then a certain method where just water was used.

My question is what would be the likely mechanism for a sodium bicarbonate solution to remove pesticides better than plain water (which was also tested in the mentioned study) and what that says about the applicability of the study to other pesticides (is the result likely to be applicable just to the two pesticides tested, or to be quite general?)

Here is my guess; a guess from just dabbling in chemistry here and there (I'm a computer programmer and by no means an expert on chemistry). The guess is that the additional hydroxide ions in the solution, created due to the sodium bicarbonate having been added, make hydrolysis of the pesticides more likely because the hydroxide can do a "nucleophilic attack".


texts: Naming ionic compounds with multiple cations and anions

texts:
I have seen complex ionic compounds that have mixed anions and/or mixed cations. For Example I have seen this:

$$\ce{NaKCl2}$$

Also known as Sodium Potassium Chloride. The only information I can find on this is an ion cotransporter for sodium potassium and chloride ions.

Anyway the structure of a single monomer of this would be $\ce{Na+}$ $\ce{Cl-}$ $\ce{K+}$ $\ce{Cl-}$

I have also thought of this as a possibility:
$$\ce{Na3ClO}$$

This looks very similar to sodium hypochlorite in terms of its formula but has a different structure. The structure of it would be $\ce{Na+}$ $\ce{Cl-}$ $\ce{Na+}$ $\ce{O^2-}$ $\ce{Na+}$

I know that naming mixed ionic compounds is not easy unlike naming simple ionic compounds(which itself can be hard if you don't know the name of a particular polyatomic ion). But how would I go about naming these mixed ionic compounds?


texts:
Does $\ce{LiAlH4}$ and $\ce{NaBH4}$ reduce an isolated epoxide? I have two books where both are saying differently. One says it can and other says cannot. On searching the web there was no definite answer. Can they reduce epoxide to diol or something else ?
I am aware of the reduction of the other groups in the picture:

Sources:  NCERT: yes; JEE Advanced 2016 paper solution by Arihant: no; multiple coaching stuff: both yes/no


texts: Nucleophilic aromatic substitution on pyrimidines: C2 vs C4 selectivity

texts:
[There are many similar questions on Chemistry.SE (e.g. 1, 2) and a quick search will reveal all of them, but nothing on this in particular.]

The reaction of 2,4-halopyrimidines with nucleophiles generally leads to selective displacement of the halide at the 4-position:1

In their textbook, Joule and Mills don't explain why, though, simply saying that it "is the normal situation for nucleophilic – 4-chloro > 2-chloro".

I don't see any obvious difference in the stability of the anionic intermediates, either (the so-called Meisenheimer complexes).

What can explain the regioselectivity of the above reaction?

Reference

Joule, J. A.; Mills, K. Heterocyclic Chemistry, 5th ed.; Wiley: Chichester, U.K., 2010, p 257.


texts: Why is the the rate of a reaction measured in concentration?

texts: Why is the rate of a reaction measured using concentration against time, rather than mol against time?


texts: Is there any evidence, *any evidence at all*, that nascent hydrogen actually exists?

texts: As far as I know, nascent hydrogen is nothing more than an especially magical unicorn entity that either makes reactions happen or at least greatly facilitates reactions happening. Many years ago, it was assumed that nascent hydrogen existed, but it was never characterized in any way because it did its work so fast as to escape detection. Now I am seeing "answers" to questions that invoke nascent hydrogen. I consider nascent hydrogen to be entirely bullcrap, pardon my language. Would someone please tell me what is going on with this?


texts: Does s stand for sigma bond and p for pi bond?

texts: When we are talking about hybridization, in $\mathrm{sp/sp^2/sp^3}$ hybridization, does s stand for sigma bond and p for pi bond ?


texts: Is there any fuels without hydrogen that will combust. My friend believes there might be and do to my experience I have never heard of one. Please explain and if u can show a balanced equation of this combustion.


texts: van der Waals equation for deviation of gases from ideal behavior

texts:
$(P + an^2/V^2)(V - nb) = nRT$

I understand that the term $nb$ is subtracted from the volume term as the available volume for the gas molecules to move around decreases in the case of a real gas due to the volume of the molecules themselves.

However, I don't understand why the term $an^2/V^2$ is added to the pressure term. Because of the attractive/repulsive forces, shouldn't the pressure on the walls of the container by the molecules also decrease?
(I thought about this and guessed that due to repulsive forces, the pressure must be increasing, but what about due to attractive forces? Does the sign of $a$ depend on the gas and hence affect the equation? I may be wrong here.)

Please clarify!


texts: How can the ground state electron configuration for a d3 complex correspond to an F term symbol?

texts:
The ground-state term symbol from a $\mathrm{d^3}$ Tanabe-Sugano diagram is $\mathrm{^4F}$. My question is how the total orbital quantum number $\Lambda=3$, or $\mathrm{F}$ term, arises.

For a $\mathrm{d^3}$ metal, I'd expect the following ground state d-electron configuration:

where notably the $\mathrm{t_{2g}}$ orbitals correspond to $\mathrm d_{xy}$, $\mathrm d_{xz}$, and $\mathrm d_{yz}$ suborbitals.

From the spherical harmonics, $\mathrm d_{xy}$ results from a linear combination of:

$$\begin{align}
Y_2^{-2}(\theta,\varphi) &= \frac{1}{4}\sqrt{\frac{15}{2\pi}}\cdot \mathrm{e}^{-2\mathrm{i}\varphi}\cdot \sin^2\theta \\
Y_2^{+2}(\theta,\varphi) &= \frac{1}{4}\sqrt{\frac{15}{2\pi}}\cdot \mathrm{e}^{2\mathrm{i}\varphi}\cdot \sin^2\theta
\end{align}$$

i.e. $m_l=\pm2$ equations.

$\mathrm d_{xz}$ and $\mathrm d_{yz}$ result from:

$$\begin{align}
Y_2^{-1}(\theta,\varphi) &= \frac{1}{2}\sqrt{\frac{15}{2\pi}}\cdot \mathrm{e}^{-\mathrm{i}\varphi} \cdot \sin\theta \cdot \cos\theta \\
Y_2^{1}(\theta,\varphi) &= -\frac{1}{2}\sqrt{\frac{15}{2\pi}}\cdot \mathrm{e}^{\mathrm{i}\varphi} \cdot \sin\theta \cdot \cos\theta
\end{align}$$

i.e. $m_l=\pm1$ equations.

From this assumption–which I may very well have presented incorrectly – the $\mathrm{t_{2g}}$ orbitals would therefore correspond to $m_l$ values of $\pm1$ and either $+2$ or $-2$. This would mean the greatest $\Lambda$ from one electron in each $\mathrm{t_{2g}}$ orbital (a $\mathrm d^3$ ground-state electron configuration), would be $\mathrm d_{xy} + \mathrm d_{xz} + \mathrm d_{yz} = \pm2+1-1=\pm2$, or a $\mathrm{D}$ term symbol.

Would anyone be able to correct me where my logic went wrong? I have a feeling I'm not allowed to restrict the $\mathrm{t_{2g}}$ orbitals to those $m_l$ values, but why would that not be allowed, when those are the equations that derive the $\mathrm{t_{2g}}$ d-orbitals?

Thank you!


texts: Silver (111) surface structure, and is bulk structure body-center or face-center cubic?

texts:
I'd like to understand the atomic arrangement is on a silver (111) surface.

Step 1 would be to find out the bulk crystal structure.

Wikipedia lists silver as face-center cubic (fcc) here and here and the page Silver: crystal structures also shows fcc and links to Lin-gun Liu and W. A. Bassett, J. Appl. Phys., 1973, 44, 1475:

But the page Ag(111) and Ag/Si(111): similarities and differences begins

  The crystal structure of silver is body-centred cubic (Figure 4.4a), and so the Ag(111) plane exhibits a close-packed, hexagonal structure (Figure 4.4b). Ag is a stable transition metal, and one of the few metals found abundantly in nature as a pure native element. This stability is due to its relative inertness, and the Ag(111) close-packed surface has the lowest energy of its high-symmetry surfaces.

While this page tells me that the silver (111) surface will be a close-packed hexagonal arrangement, I am uncertain I can trust this because it begins by stating that silver is bcc and Wikipedia tells me silver is fcc.

  Figure 4.4: (a) Schematic model of the silver body-centred cubic structure, showing the (111) cleavage plane. (b) Model of the close-packed Ag(111) surface, with the principal directions indicated.

Question(s):

Is bulk silver bcc or fcc?
What is the structure of the silver (111) surface?


texts: Growing crystals that are in a magnetic field or subjected to an electric field

texts:
I know different crystals resonant at different frequencies but is it possible to grow crystal at a certain frequency.  An example would be growing crystals using Epsom salt or Alum in a magnetic field or when it's subjected to an electric field while two electrodes are submerged into the saturated solution.

The reason I ask is I know they can "program" magnetic fields one company doing this is called Correlated Magnetics

A video that explains "programming" magnets

I would like to do something similar but with crystals.  I do know there are ways to test the resonance of crystal oscillators Video showing how to find resonance frequency of crystal oscillator

How to test Rochelle salt piezoelectric crystals voltage oscilloscope

Now I'm just trying to see and find out if I can "program" crystals at various frequencies by subjecting them to magnetic fields or electric fields.  Has anyone tried this or know of research being done?


texts: Is there a chemical treatment for pipes to reduce or eliminate leaching of lead into tap water?

texts: Given events in Flint, Michigan, where a switch to acidic river water in the city water supply resulted in leaching of lead into tap water from the insides of pipes, I wonder -- has anyone has heard of a chemical treatment for pipes that would reduce or eliminate further leaching of lead into the water?


texts:
A primary battery has the reaction:
$$\ce{2MnO2 + Zn + 2NH4Cl -> Mn2O3 + Zn(NH3)2Cl2 + H2O}$$
Write the half-cell reactions for the given equation.

I am having trouble understanding how you know which will be the oxidation reaction and which will be the reduction reaction. From what I have understood I should assign the oxidation states of each reactant and product and from that I assume that the reactions should be:
Ox: $\ce{Zn + 2NH4Cl -> [Zn(NH3)2]^{2+}}$  +  ...
Red:  $\ce{2MnO2 +  ...  -> Mn2O3 + H2O}$  +  ...
And by balancing out the hydrogens and charges I get that:
Ox: $\ce{Zn + 2NH4Cl -> [Zn(NH3)2]^{2+} + 2H+ + 2 Cl- + 2e-}$
Red:  $\ce{2MnO2 + 2H+ + 2e- -> Mn2O3 + H2O}$
Is this correct? Or should the oxidation reaction only be: $\ce{Zn  -> Zn^{2+} + 2e-}$ and then the reduction reaction would consist of the remaining compounds?
All help is appreciated.


texts: What pH value of 1M sodium crotonate solution supposed to be?

texts:
I need to prepare the $\pu{1M}$ solution of sodium crotonate, however, I don't have one in lab, but I do have sodium hydroxide and crotonic acid.
Thus, I calculated that for $\pu{100 mL}$ of $\pu{1M}$ solution I need: ~$\pu{4g}$ of $\ce{NaOH}$ and ~$\pu{8.6g}$ of crotonic acid. After preparation of solution (approx $\pu{80 mL}$ of DI water to dissolve the crotonic acid in a beaker, add $\ce{NaOH}$, mix until dissolving, let it cool down, quantitatively transfer a solution into a $\pu{100.0 mL}$ volumetric flask, adjust the volume), the $\mathrm{pH}$ of the final solution is 6.1 (which also stays the same after purging with $N_2$ gas and autoclaving).
To my understanding, the solution of sodium crotonate supposed to have a basic $\mathrm{pH} \ (\gt 7)$ since it is formed by weak crotonic acid (with a $K_\mathrm{a} = 1.97 \times 10^{-5} $, reference) and a strong base. Thus, the rough estimation of $\mathrm{pH}$ should be done according to formula:
$$
\mathrm{pH} = 14 + \lg \left(\sqrt {\frac{K_\mathrm{W} \times C_\text{sodium crotonate}}{K_\mathrm{a}}} \right)\\= 7 + \lg \left(\sqrt {\frac{C_\text{sodium crotonate}}{K_\mathrm{a}}} \right) \\= 7 + \lg \left (\sqrt\frac{1}{1.97 \times 10^{-5}} \right) = 9.35
$$
Which results in a far higher value.
On the other hand, if I suspect the formation of buffer solutions as sodium crotonate + crotonic acid (if there was not enough hydroxide), then the final $pH$ should be estimated according to:
$$
pH = pK_a + \lg \frac{C_{salt}}{C_{acid}}
$$
Which roughly estimates 3.8% of unreacted acid in solution. However, even if I arbitrally assume only 0.1% of unreacted acid in solution, the formula results in $pH$ of 7.7, which is anyway higher than I obtained, but still not a 9.35 as should be.
So, my questions are:

What is the real value of $\pu{1M}$ solution of sodium crotonate supposed to be (like if prepared from salt reagent)?
I think I should adjust the $\mathrm{pH}$ with $NaOH$, but for what final value? 9.35 or 7.7?
Are there any verified protocols for preparation such solution (USP / EuP / etc.)?

P.S. I also found paper where sodium crotonate solution was prepared by reacting sodium bicarbonate and crotonic acid followed by adjusting $\mathrm{pH}$ to a final range of 6.7 ... 7.0, but I still don't get why they stopped at $\mathrm{pH}$ of 7, not higher.
P.P.S. As also stated here, the pH "without neglecting the water autoionization" can be estimated by solving this equation:
$$
\left\{\begin{matrix}
\left [ H^+ \right ] ^3 +\left ( K_a + C_{salt} \right ) \times \left [ H^+ \right ] ^2 - K_w \times \left [ H^+ \right ] - K_w \times K_a = 0
\\
\left [ H^ + \right ] > 0
\end{matrix}\right.
$$
However, it results into
$
\left [ H^ + \right ] = 4.43847 \times 10 ^{-10}
$
and $pH = 9.35$ which is not much different from the previous estimation.


texts: Is there any reaction between amines and AgNO3?

texts:
I found a question in a book about the reaction between $\ce{AgNO3}$ and aromatic/aliphatic amines, but I couldn't find any information about
it. What should be the expected reaction mechanism and products formed in this reaction?


texts: Spectral reflectance identification of types of iron rust

texts:
Based on the Wikipedia page about rust, there are red and green types of rust that occur on iron.  Red rust is the reaction with oxygen and water and the green with chlorine (in oxygen poor environments).

I understand the chemical reactions that forms these types of rust, but in the Wikipedia article, it states that:

  Several forms of rust are distinguishable both visually and by spectroscopy

(bolding mine). Visually, it'd be pretty obvious (one is red, one is green); spectroscopy-wise, I would imagine it to be a similar story - but what aspect of the types of rust cause this difference - hence, the question:

Are the spectral reflectence features that distinguish between the red and green rust types based on what the iron reacts with (oxygen/water or chlorine), or is it based on the type of iron present (Fe2+ vs Fe3+)?

Full disclosure, I have a similar question on Open Data.SE here, but are asking for an explanation in terms of spectral reflectivity.


texts:
I am currently studying for my organic chemistry exam, but there is one problem I do not understand. Unfortunately, I do not have any solutions.

See image for the problem.

My first thought was the Dienone-phenol-rearrangement. But in order to do so, I need to add the alkyl substituent and I need a dienone. So can I deprotonate the phenol using potassium carbonate? (Or is it too weak as a base? The pKa of bicarbonate is around 10, so maybe it is too weak) But if it is possible, then the free electron pair of the oxygen can form a ketone... I could then use the alkene with a chloride substituent, so that the aromatic ring can attack it. Then I would have the dienone. But with the Dienone-phenol-rearrangement, the alkyl substituent can only move by one carbon-atom in the ring...

Is my thought process wrong? Can you please help me?

I did not have any lectures on rearrangement reactions, I had to learn them by myself, but by now, I have not found any similar reactions.

Thank you!