texts: Chemistry of solids: allowed wavevectors

texts:
I'm a complete beginner in the chemistry of solids, and many of the things I came across don't make sense. I have two subquestions, which I think it would be most logical to post as a single question.

The longest wavevector of a commensurate matter wave is $k_{max} = \pi / d$, where d – lattice-plane spacing, so that amplitude minima and maxima of the wave  coincide with adjacent lines / planes of atoms. I don't understand this explanation – why is, for example, $k = 2\pi / d$ inconsistent?
Bloch's equations dictate that the value of the electron wavevector isn't uniquely defined, and the vector is uncertain to modulo G, where G – a general Reciprocal Lattice (RL) vector. This means that wavevectors greater than $\pi / d$ are permitted and can be found in Brillouin's zones of order greater than 1 in the RL. This seems to be in contradiction to the point above – what am I missing?


texts: Differences between hexaaqua cobalt (III) complex and hexammine cobalt (III) complex in aqueous solution

texts:
Why is $\ce{[Co(H2O)6]^3+}$ a strong oxidizing agent and $\ce{[Co(NH3)6]^3+}$ stable in Aqueous solution?

I think this has got to do with Pairing Energy and Ligand strengths of $\ce{H_2O}$ and $\ce{NH_3}$ but I haven't been able to get a definite answer so far, neither by my friends nor by google.


texts: How can over grinding lead to reduced API extraction in HPLC analysis?

texts:
I am looking for some advice regarding particle size distribution (PSD) & how this can be affected by grinding a tablet.
During an assay by HPLC, the method requires grinding of a tablet before dissolving in order to extract the active pharmaceutical ingredient (API) into solution. Of the tablet, the API is only 0.5% m/m of the tablet. I have been told that over grinding the tablets can affect extraction of the API and this is supposedly related to PSD as the API is the smallest particle found in the tablet amongst other excipients.
Could someone explain how "over grinding" would cause a detremential effect? Thanks.


texts: effect of temperature on position of equilibrium

texts: I was wondering if there was an intuitive way of explaining how a change in temperature would effect the position of an equilibrium, without using le chateliers principle. Le Chateliers principle doesn't seem to explain why the equilibrium shifts the way it does, I was wondering if there was a way of explaining this.


texts:
Is there a decent on-line source for dissociation constants for acids and bases as CRC alternative?
This chemistry stackexchange old answer no longer has valid links:
Is there an online database of acid and basic dissociation constants?
I can only find abrupt and and possibly non-reliable links with often missed temperature like these:

https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/acidity.htm
https://courses.lumenlearning.com/boundless-chemistry/chapter/strength-of-acids/
https://infotables.com/chemical-tables/87-dissociation-constants-of-acids-and-bases-inorganic.html
https://chem.libretexts.org/Ancillary_Materials/Reference/Reference_Tables/Equilibrium_Constants/E1%3A_Acid_Dissociation_Constants_at_25C
https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Acids_and_Bases/Monoprotic_Versus_Polyprotic_Acids_And_Bases/Polyprotic_Acids_and_Bases_1
https://depts.washington.edu/eooptic/links/acidstrength.html
https://clas.sa.ucsb.edu/staff/Resource%20Folder/Chem109ABC/Acid,%20Base%20Strength/Table%20of%20Acids%20w%20Kas%20and%20pKas.pdf

Thank you.


texts:
I recently came across this question while studying Solid State.
The coordination no. of [Ni(CN)4]2- is 4  as Ni is bonded to 4 CNs and  is planar in structure.Hence its Limiting Radius Ratio must be between 0.225 and 0.414 . But the answer given in the book is 0.414 to 0.732 (which is the limiting radius ratio for coordination no. 6) .
How is this true?Some sites agree with my answer .
Is the answer given in the book wrong or have I made any mistake in the reasoning?


texts: Is it possible to add R chain that contains a carbonyl (ketone) to the alpha carbon?

texts:
I'm trying to synthesize 2‐(3‐oxobutyl)cyclohexan‐1‐one from cyclohexanone:

I thought about LDA, then adding an R group that has a ketone. Is that possible? As far as I know, we can add halogen or alkyl chain only. If it's not possible how can I get this compound from cyclohexanone?


texts:
Why is the $\ce{I-Cl}$ bond length in $\ce{ICl2-}$ (charge of -1) is longer than in $\ce{ICl2+}$ (charge of +1) ?

Here are a few explanations that I have in mind. Please critique.

I in $\ce{ICl2-}$ is $sp^3d$ hybridized. $\ce{I}$ in $\ce{ICl+}$ is $sp^3$ hybridized. Since additional promotion energy is required to form the $sp^3d$ hybrid compared to the $sp^3$ hybrid, the bond lengths in $\ce{ICl2-}$ is longer.
For $\ce{ICl2-}$, if we let $\ce{I}$ be $sp^2$ hybridized such that the 3 lone pairs lie 120 apart in a plane, and then let the 2 $\ce{Cl}$ atoms and the $\ce{I}$ atom lie in a straight line, then we can form a 3-centred, 4 electron system. This is weaker than the 2-centred, 2 electron system in the $\ce{I-Cl}$ bond in $\ce{ICl+}$.
As $\ce{I}$ in $\ce{ICl2+}$ has a higher effective nuclear charge, its valence orbitals are smaller and more compact, hence the $\ce{I-Cl}$ covalent bond is stronger as the electrostatic attraction between the nuclei and the overlap density is stronger.


texts: Is 3,5-diethyltoluene an accepted IUPAC name?

texts:
My book says that

  Monocyclic substituted hydrocarbons are named as derivatives of benzene or compounds like cumene, toluene, xylene, etc. However, if the substituent introduced into such a compound is identical with the substituent already present in the compound, then the substituted compound is named as tge derivatives of benzene.

But I guess that names like toluene have stayed due to historic reasons and are not accepted in IUPAC nomenclature. Is my book correct?


texts:
I have to say I have never really understood the half reaction method. What bothers me is that it seems to be too artificial. Too many little rules to remember!
Why don't we use the mass conservation law to justify the process and use sistematically a set of linear equations to do the balances?

Thanks in advance!


texts: Are titration, recrystallisation, functional group analysis, etc. outdated?

texts:
In modern chemistry,
- pH meter, ion electrode, AES, HPLC, etc. replacing titration
- HPLC replacing recrystallisation
- IR and NMR replacing melting point analysis, derivative analysis, functional group analysis

In other words, are the techniques that being replacing only being used inside school and teaching labs?


texts: Detailed description of hydroxy(phenyl)methanesulfonic acid?

texts:
Hydroxy(phenyl)methanesulfonic acid, or benzaldehyde adduct is the product of reacting benzaldehyde with sodium metabisulfite ($\ce{NaS2O5}$) solution.
It is obviously a well-known and often used reaction, and yet, I'm not able to find much info on the adduct, or the reaction itself.

One thing I managed to dig out is its corresponding PubChem entry.

I want to find out the exact mechanism of the reaction with an equation, a bunch of videos of someone performing it will be nice too...

But most importantly - the hydroxy(phenyl)methanesulfonic acid: What is its color, texture and so on? What is its crystalline structure? Is it supposed to smell of benzaldehyde, how soluble it is in different solvents, how should it be stored, is it harmful or dangerous, does it decompose in some conditions, melting point, and so on.


texts: Is cyclohexene an alicyclic or aromatic compound?

texts:
Classification of organic compounds have open and closed chain compounds. Closed chain further have homocyclic and heterocyclic componds. In homocyclic compounds there are two types: alicyclic and aromatic compounds.

In alicyclic compounds, only singles bond are allowed, whereas in the aromatic category the ring of carbon atoms has alternate single and double bonds (i.e. conjugated double bonds). So what happens to the compounds which have a lone double or triple bond?

For example, cyclohexane is classified under alicyclic, but where would cyclohexene or cyclohexyne be classified?


texts:
I'm supposed to balance a redox equation. I arrive at
$$
\ce{H2O} + \ce{NH4+} + 2\ce{S^{2-}} + \ce{O2} \rightarrow \ce{NH3} + 2\ce{S} + 3\ce{OH-}
$$

The "official" solution is
$$
4 \ce{NH4+} + 2\ce{S^{2-}} + \ce{O2} \rightarrow 4\ce{NH3} + 2\ce{S} + 2\ce{H2O}
$$

There is no information about if this is occuring in basic or acidic medium. But IMHO in the first equation the charges and all atoms are balanced, so are these equations equivalent?


texts: Does H2O2 break down into H2O + O or H2O + O2?

texts:
In hydroponics, Hydrogen Peroxide is used to sanitise nutrient solution from pathogens. Allegedly it does not take sides, oxidising aerobic as well as anaerobic, including damaging the roots, so I was told. I believe this argument, since O as a free radical is highly reactive. I would appreciate your input on this. However, this isn't the main question.

The main question is that manufactures also claim that it will provide DO, dissolved oxygen, to the solution. I find this hard to believe. Reason being, DO refers to dissolved $\ce{O2}$ (Dioxide) not Monoxide. When $\ce{H2O2}$ breaks down it breaks down to $\ce{H2O + O}$ (free radical), right?

Can you please put some clarity into this?


texts: The "Ostwald Isolation Method": How does this work?

texts:
Recently started reading up on Chemical Kinetics, and I came across a certain "Ostwald Isolation Method" that figures in my school-issued workbook. Apparently, it's used to determine (approximately) the order of a given reaction.
However, the painfully short passage that constitutes that section of the book, coupled with my teacher's reluctance to take up the said section in class, means I still don't know how this "method" works. Heck, I don't even know if the said "method" even exists (at least not under that name anyways...the book is notorious for its numerous errors that have gone unchecked over the years. We fondly view it as the Mater Omnium Errorum)

My book, on the "Ostwald Isolation Method":

This method is particularly useful in case of reactions where two or more reactants are involved.
Consider the reaction between $a$ moles of species $A$ and $b$ moles of species $B$ to give product(s) $P$: $$\ce{aA + bB -> P}$$
The reaction is first carried out with $B$ present in great excess. So the reaction must only depend on the concentration of $A$: $$\ce{r = k[A]^{x}}$$
Similarly, when the reaction is now carried out in a large excess of $A$, the rate of reaction must only depend on the concentration of $B$: $$\ce{r = j[B]^{y}}$$
The order, $n$, of the overall reaction is therefore: $$\ce{n = x + y}$$

Okay, I understand how the first two bits work (i.e- Concentrations of whatever species present in excess can safely be considered constant/invariant).
But I don't get how directly adding $x$ and $y$, both obtained from different rate equations, having different rate constants , gives us the overall order of the original (without excess) reaction.
Could someone explain the logic behind this to me? That is, if there is any logic behind it...


texts: Treatment of ketones with excess Tebbe reagent

texts:
The reaction in black below was presented in a set of lecture notes as an example of the use of the Tebbe reagent, however it's not immediately obvious (to me, at least) that the product should be the gem-dimethyl compound shown.

Mechanistically, it appears that the Tebbe olefination has taken place once (standard formation of Schrock carbene, [2+2], retro [2+2] to give the alkene and a Ti=O compound as a thermodynamic driving force). The alkene must then however react with more Tebbe reagent (or more Schrock carbene) to form a metallacyclobutane. It's at this stage that I feel it makes less sense: firstly, what is the involvement of the deuterium oxide, but secondly and more importantly, why doesn't the metallacyclobutane just collapse back down to form the thermodynamically favoured alkene product.

I've used Tebbe in the past to turn ketones into terminal methylene groups, but never encountered what appears to me to be an over-reaction (I'd actually always considered Tebbe to be fairly mild and selective).

After some digging around in Comprehensive Organic Synthesis I, there is some mention of this 'over reaction' (1985JOC50). The authors report that treating the ketone 22 with 1 equivalent of Tebbe reagent affords a mixture of the expected methynlenation product along with some of the gem-dimethyl product (i.e. implying that an excess isn't required, but the reaction is just not overly chemoselective for the cyclic ketone over the cyclic alkene).


texts: Distilled water to clean greasy stains: Why does that work?

texts:
I noticed that distilled water works well to clean away fingerprints on touchscreens or oil stains on a ceramic field after frying an egg.

But water and oil/fat are not supposed to mix, so why does that even work?


texts:
I'm having difficulty understand the relative stabilities of the compounds

  2,4-dimethyl-3-methylidenepentane < (3Z)-2,5-dimethylhex-3-ene < (3E)-2,5-dimethylhex-3-ene

which, for simplicity’s sake, can be described as

  1,1-diisopropylethene < (Z)-1,2-diisopropylethene < (E)-1,2-diisopropylethene

The compounds are listed in order of increasing stability.

Also, what does the $\ce{C=C-C}$ bond angle have do to with stability?


texts: I figure that t-BuLi has effectively a negative charge on the carbon that is attached to 3 methyl groups. So I'm wondering what is the accurate way to represent this reaction, does the carbon anion attack a silicon atom in the chain like so-


texts:
I am fairly new to anodization of Titanium. It concerns anodization using oxalic acid with the sole purpose of coloring Titanium grade 2 parts (= type III?). After some research online, I found a lot of information on the required voltage levels per color. However, to my understanding, the "purpose" of the voltage is only to induce a certain current. I did find a few articles and discussions on other forums about anodization based on the current density, but I mainly found information related to a constant voltage. Considering that the current generated by a certain voltage also depends on the resistance of the anode, cathode, electrolyte, etc., I'm wondering why there is this little information on the required current density instead of the required voltage.

Can anyone give me (a link to) the information that I'm looking for or explain me why my reasoning is not correct?

If any information is missing, please let me know!


texts: How do you calculate the absorption spectrum of water?

texts:
If you look online you can find various graphs of the absorption spectrum of water. The graph below for examples comes from this blog post.

As far as I can tell these graphs come from empirical measurements. Is there a theoretical model that can derive the same or similar results?  Of course if it was easy to implement in software that would be ideal.


texts: Experimentally finding order of a reaction

texts:
For the reaction of bromocresol green and bleach, I was supposed to conduct an experiment to find the order of the reaction with respect to bleach. To do this, I used a fixed amount of bromocresol green and varied the amount of bleach in each trial. I recorded the amount of time it took for each reaction to finish.

To find the order, I was told that if the order = x, $\frac{time_1}{time_2} = (\frac{[bleach]_2}{[bleach]_1})^x$. However, I'm having trouble understanding why this is true. For example, say we begin with $[bleach]_1=y$ and $[bleach]_2=2y$. If $\frac{time_1}{time_2} = 2^x$, this means that the rate of reaction 2 is always $2^x$ times faster than the rate of reaction 1.

In the beginning, this is definitely true, since rate = $k[bleach]^x$. Initial $rate_1 = ky^x$ and initial $rate_2=k(2y)^x$. But at a time $dt$ later, $[bleach]_1=y-ky^x\cdot dt$ and $[bleach]_2=2y-k(2y)^x\cdot dt=2y-2^xky^x\cdot dt$. At this time, $\frac{rate_2}{rate_1} = (\frac{2y-2^xky^x\cdot dt}{y-ky^x\cdot dt})^x$, which does not equal $2^x$ unless $x=1$.

Thus, I'm not understanding why $\frac{time_1}{time_2} = (\frac{[bleach]_2}{[bleach]_1})^x$ is true for x other than 1. Any clarifications would be much appreciated.


texts: Does partially/completely removing solid shift the equilibrium?

texts:
For the reaction: $$\ce{P4(s) + 5O2(g) <=> P4O10(s)}$$
Let's say the reaction is at equilibrium, and SOME $\ce{P4O10(s)}$ is removed from the reaction. Will that affect equilibrium? My assumption is no, since $\ce{P4O10(s)}$ is not included in the equilibrium expression.
However, for me, it gets confusing when let's say $\ce{P4O10(s)}$ is COMPLETELY removed. In this case, I would assume that the reaction shifts to the products (since no products are present). I'm not sure if this is right.
Help is appreciated. Thank you!


texts: Pseudo 3D skeletal structure style which emphasizes geometry

texts:
If one searches and navigates to a wiki page for, say, dichlorodifluoromethane one sees the 2D skeletal structure of the compound as below

This representation appears to be of a particular style that is not exactly what is rendered when one uses a rendering tool such as MolView or obtains data from PubChem and uses other converters/rendering tools.

The big difference may be that the former example shows bond angle information, stereospecificity and generally emphasizes the geometry of the molecule.

My question is whether there a database allowing access to data which are already in this style (e.g. bond angles and bond types included), or does one typically configure the finer details of the drawing / modifies the source data in order to achieve the specific style alluded to above?

Also, what is the most used name for the style of the former example (2D version which conveys 3D information)?


texts:
Why is the $\ce{sp^2}$ hybridized nitrogen atom in guanidine the most basic?

I know that as a general guideline, $\ce{sp^3}$ hybridized atoms are more basic than $\ce{sp^2}$. Bases are electron pair donors; having the electrons further away from the nucleus makes donation easier.

On the other hand, protonating the double bonded nitrogen enables effective resonance stabilization. The positive charge can be delocalized across the molecule. Protonating the other nitrogens does not allow for the same degree of resonance stabilization.

And finally, in one textbook, I found mention of a +M effect - what is the +M effect? And while we're on that, what's +/- I? I understand that I stands for induction, but what's +I? What's positive induction?

One more note, since the double bonded nitrogen is $\ce{sp^2}$ hybridized, does that mean it has a greater negative charge density than the other nitrogens by nature of having greater s-character? Could this + charge density be giving the double bonded nitrogen more nucleophilic character?


texts: Naming phosphonium cations in ionic liquids

texts:
In Rennie et al., J. Phys. Chem. Lett., 2013, the following cation and anion structures are given in Figure 1.  Figure 1(f) is captioned as butyltrimethylphosphonium, which seems to match the given structure.  However, in the caption, the abbreviation $\text{P}_{2225}$ is given, which seems strange:

Rennie et al. repeat this in their Supporting Information:

But, other authors, such as Tsuchida et al., J. Mol. Liq., 2018, use $\text{P}_{2225}$ as an abbreviation for triethyl-n-pentylphosphonium, which makes sense if the subscript numbers represent the number of carbon atoms in the substituent alkyl groups:

Does it seem to you that there is a typo in the Rennie et al. paper? Or, what are the standard abbreviations for phosphonium cations?


texts:
I want to make some homemade ink suitable for amateurs to practice calligraphy. I have access to many household chemicals, including acetic acid, sodium hydrogen carbonate, sugar, sodium chloride, and more.

Can someone give me an easy recipe for a colored (any color will be fine) ink that I can make at home? (preferably basic, but slightly acidic is fine too I guess)

Here are some ideas:

Caramelized sugar --- nope, too expensive and smelly.
Something with rust? (iron)
Something like india ink. (pigments are acceptable too)
Cornstarch and iodine.


texts: Is energy required to form bonds [phase change]

texts:
My question is if any energy is required to form bonds, for instance when there is a phase change?

If I am correct, energy might be required in the beginning, to make the reaction start and then release a bigger amount of energy than it was putted in. However, in terms of molecular behaviour in a phase change, I think there should not be any energy required to make the molecules to form bonds, if they are placed in a system which has a lower temperature than the molecules. Would they not lose the kinetic energy after a specific time?


texts:
Since formaldehyde gas is flammable, is there a safe way to burn it, and can this be done to dispose of the gas or neutralize its harmful effects (tear production, respiratory problems, etc.)?

This is a more detailed form of my earlier question, including the context of "gas disposal".


texts:
I was reading about water photolysis which produces a positive water radical and a dry electron, or an excited water $\ce{H2O^*}$ through the following equation

$$\ce{
H2O ->[$hv$] H2O^{.+} + e_{dry}^-, or~ H2O^*
}$$
(as seen in this link)

By opposition I have also seen $\ce{e_{aq}^-}$ (as seen in pp. 2 of this link).

I can understand the "positive water" and even the "excited water", but what is a "dry electron"? And what is an $\ce{e_{aq}^-}$ (wet electron? I am unsure of how to translate the term I had learned to english). Why not simply say "free electron"?


texts: What is a "ynoate" in the context of alkynes?

texts: In the literature, I have read the term, "ynoate" refer to a sort of alkyne. Searching through the IUPAC gold book and Google has failed to return an explicit definition.


texts: Why do diacidic and triacidic alkalis dissociate in one step?

texts:
My book states that dibasic and tribasic acids dissociate in water in two and three steps respectively but for diacidic and triacidic bases it states that they dissociate in one step. I do not know why.

For example:

$\ce{H2SO4}$ dissociates in water in two steps as follows:
$$\ce{H2SO4(aq) <=> HSO4^{-} + H+}$$
$$\ce{HSO4^{-}(aq) <=> SO4^{2-} + H+}$$

but

$\ce{Cu(OH)2}$ dissociates in water in one step as follows:

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

Why is this so. Why does not $\ce{Cu(OH)2}$ dissociate in two steps to form $\ce{CuOH+}$ in the first step and $\ce{Cu^{2+}}$ in the second step?


texts: Is propanol 1-2 diol 178 the same as propylene glycol?

texts: I clean vinyl records in an ultrasonic vinyl record cleaning machine the manual states it uses propanol 1-2 diol 178 as a surfactant.  I think this is the same chemical as propylene glycol. Is it?


texts: The intuition behind carbon's covalent bonds

texts:
As an introduction to hybridization, my textbook discusses that "The formation of covalent bonds often starts with the excitation of the atoms." Taking carbon as an example, the author says:

  Carbon  forms four covalent bonds. Yet if we consider the elctron configuration in the carbon atom, we would not predict this as it has only two singly occupied orbitals available for bonding. ($1s^2\, 2s^2\, 2p_x^1\, 2p_y^1$)

I don't understand why carbon's bonding is counterintuitive. Why don't the 4 added electrons just go into the $p_x$ and $p_y$ orbitals then into some newly formed $p_z$ orbital? Why does the existence of "only two singly occupied orbitals available for bonding" complicate things?

As an extension, why is the excitation of the s-orbital electron to $p_z$ needed?

Thank you for your answers and please try to respond keeping in mind that I am a high schooler (more specifically, part of the IB Diploma program).


texts: How would my sample be affected if the sample was not totally dry? What would happen to the mass percent composition? I believe that it will increase but someone argues that due to ratios, it will decrease.


texts: How to generate sulphuric acid vapour to test an analyzer?

texts: We have a UV gas analyzer we want to test to see if it reads gas phase $\ce{H2SO4}$. How can we safely produce less than $\pu{5 ppm}~\ce{H2SO4}$ as a spike test to see if the analyzer sees the spectra?


texts: Why there are just two Ramachandran angles in protein structure for two peptide bonds?

texts: I really want to understand why there are just two ramachandran angles to understand the structure of the protein and why not three or many ? Can someone suggest some reference and explain this ?


texts: Is it possible to calculate the concentration percentage using chromatography paper?

texts:
I'm trying to calculate the concentrations of specific compounds using paper chromatography. Would I be able to calculate a rough estimate by comparing the size of each concentrated spot? If not is there another way to calculate this?

Thanks!


texts: Is there an advantage to the Clemmensen or Wolff-Kishner reductions over the Mozingo reaction?

texts:
As I understand it (and please correct me if I'm wrong), ketones and aldehydes can be reduced to methylene derivatives via:

Clemmensen Reduction (acidic conditions):

Wolff-Kishner Reaction (basic conditions):

Mozingo Reaction (mild conditions)

A preference for Clemmensen or Wolff-Kishner can be established based on functional group tolerance with respect to acidic vs basic conditions.

But if the Mozingo Reaction doesn't have the drawback of requiring either acidic or basic conditions, is there a reason to ever use the Clemmensen Reduction or Wolff-Kishner Reaction instead of simply applying the Mozingo Reaction?

images for reaction formulas from their respective Wikipedia pages


texts: How are lowercase k and uppercase K used in general chemistry courses?

texts: Where do lowercase k and uppercase K make appearances in general chemistry, and what do they signify?


texts:
So I have been studying the four methods the past couple of weeks. To my understanding, XPS is a very surface-sensitive technique. It can give information about the composition of the surface but also of the bulk material via depth profiling. I think it is mainly used for qualitative analysis, i.e. find out the elements of the sample.
The same goes for EDS/EDX (in SEM), it is used to identify samples. Strictly speaking, EDS is not a surface sensitive technique I think, because the spectral resolution is not as good as XPS. XPS looks at the first few layers of atoms, while EDS looks more at the bulk of the sample.
Now my question is: can't we do the same with FTIR or Raman? Except of course that with FTIR or Raman it would be difficult to study metals, whereas with EDS/XPS it is easy.
What are the advantages of FTIR or Raman w.r.t EDS/XPS or the other way around?
I know that there are handheld devices for FTIR and Raman, so they would be easier to use to identify unknown samples and require less sample preparation than XPS or EDS.
To me it seems that all four can be used interchangeably, except for maybe XPS, because it is so surface-sensitive. I know it depends on the applications, but in general, can either of these be used to identify unknown materials?
Summary of the question by the OP from their comments:  I mean to say that either of the methods can be used to identify unknown samples. But of course, it depends on the sample and what you want to know from the sample to know which method works best. While I agree that the methods are different and answer different questions regarding the sample, I don't agree that they are "completely" different. To some extent they do answer the question of what the unknown sample is. Right?


texts: What is purpose of sulfuric acid in iodine extraction?

texts: I am trying to extract iodine from kelp following this guide here.  It calls for sulfuric acid, but I don't see what this does do help the reaction.  I thought the reaction was simply oxidizing iodide to iodine with hydrogen peroxide, so I don't understand the purpose of the acid.  I do not have any sulfuric acid, and it is expensive to purchase, I do have a large supply of sodium bisulfate.  Could this be used as a substitute to the sulfuric acid if all that is needed is a low pH.


texts: Why is the carbon-carbon bond in hexachloroethane shorter than in ethane?

texts: How can we explain the shorter carbon-carbon bond length in $\ce{(CCl3)2}$ ($1.49 \,\mathrm{\mathring{A}}$) than that of $\ce{(CH3)2}$ ($1.534 \,\mathrm{\mathring{A}}$)?


texts: Solving two electron integral numerically

texts: Is there any software package in python or C to evaluate two electron integral repulsion integral in quantum chemistry of atoms. I am trying to solve the helium atom by constructing many body basis.Using those basis i am attempting to evaluate matrix elements.Also please suggest some references to understand more about two electron integral.


texts: What is the difference between radical initiator and radical inhibitor?

texts:
I am confused between these two concepts. My book gives $\ce{O2}$ as an example of a radical inhibitor and peroxide as an example of an initiator. But I don’t know why this is so? Both have $\ce{O-O}$ bonds so what is the difference?

Also aren’t all radical initiators in some sense? Aren’t radicals in general reactive and that they always create more radicals?


texts: Why are metalloids found in a zig-zag line on the periodic table

texts: I am confused about the zig-zag pattern of metalloids in the periodic table. Why are metalloids arranged in a zig-zag line? Can anyone answer my question?


texts: How to convert -OH to terminal -SH group in nucleolipids:

texts:
I am recently working on some synthesis of Nucleolipids and I want to transform $\ce{-OH}$ to terminal $\ce{S}$ group.

Can anyone help?


texts: Does there exist any relation between metallic property and oxidation potential?

texts: I was having a revision on periodic table I was thinking about different properties I could connect most of I could not connect metallic property and oxidation potential .


texts: Why does Co2+ have 7 electrons in the 3d orbital, and not 5 like Mn?

texts:
I'm taking general chemistry 2 this half of the summer. We are currently going over coordination complexes, ligands and transition metal ions. In particular, this question is in regards to the ligand field stabilization energy.

Why does $\mathrm{Co}^{2+}$ have 7 valence electrons in the $3d$ orbital? Doesn't the superscript $^{2+}$ denote that it is missing 2 electrons, and therefore isoelectric with $\mathrm{Mn}$?


texts: Have the STRUCTURES of synthesized anthropomorphic molecules (nanoputians) been verified experimentally?

texts:
Have the molecular structures of any synthesized anthropomorphic molecules (nanoputians) been verified experimentally?

This is a different question than this question as I am asking here about the structure, not the actual shape of the molecule. The importance of the distinction was pointed out in this helpful comment. Was there some property that was measured that confirmed that the correct, desired molecular structure had been in fact correctly synthesized?


texts:
I was wondering how we could test that the auto-ionization of liquid ammonia actually occurs experimentally. The chemical equation is described below:
$\ce{NH_3 <=> NH_4^+ + NH_2^-}$
I was thinking if there might be a substance that reacts with $\ce{NH4+}$ to form a noticeable precipitate, but I couldn’t find anything. Maybe we could test pH? But do pH tests work in liquid ammonia, and what would it tell us?
Any tips would be appreciated!
Thank you!


texts: How can I calculate the diffusion limiting current density?

texts: I know the concentration of a substrate in a water solution and I want to calculate the diffusion limiting current density for an electrode that reacts with that substrate. What are the steps to calculate that? I think I need to use Fick's law but I am not sure how to calculate dφ/dx. I assume I will get a mass transport moles/m3*second rate from Fick's law and then I can convert that to electrons and then Electrons/second to find the amperes. Can you advise please on the steps to follow?


texts: How can we conduct reactions for insoluble materials?

texts:
I am working on metal organic polydehra topic to synthesize new metal-organic cages or other based frameworks. I want to conduct postsynthetic modification for one cage, but the solubility is very poor in most solvents, only methanol can dissolve but it needs large volume.
My question for who in the field of MOFs, COFs, MOPs, and other related chemistries, how can I deal with the problem of insolubility of synthesized materials to conduct postsynthetic reactions? what are the proposed strategies and methods to attain the target modified compound?

Please you can answer based on your experience with reactions for any insoluble materials.


texts:
In Zemansky and Dittman's book on thermodynamics, pages 41–43, the authors discuss the Daniell cell as a thermodynamic system.

Their cell consists of two saturated $\ce{CuSO4}$ and $\ce{ZnSO4}$ solutions separated by a porous wall, with a copper strip dipped in the first and a zinc in the second, and with salt crystals in the bottom of each solution.

There are two problems:

The first is that the authors say that the cell is rechargeable, whereas this Wikipedia page says it not, so who is right?

The second is that the book states that in discharging mode:

  If the electrolytes are saturated solutions, a current driven by the chemical reaction at constant temperature and pressure will not alter the concentrations of the electrolytes.

Well I can't understand how this happens. I can imagine that the $\ce{ZnSO4}$ solution will be over-saturated and the extra amount of it will deposit on the crystals,  but how can the other solution keep a constant concentration?

Any help is appreciated.


texts: What reactions will occur at the anodes and electodes of two iron electrolytic cells?

texts:
What reactions will occur at the anodes and electrodes of two iron electrolytic cells: both with iron metal electrodes, one with an iron(II) sulphate electrolyte, the other with an iron(III) sulphate electrolyte?

I set up an experiment with both types of cells connected in series, which yielded the following qualitative data:

Both cathodes saw vigorous bubbling--to me implying hydrogen gas evolution.
Also, there appeared to be a darkish iron plating on the cathode, implying two reactions occurring here.
Some bubbling at anodes.
Large quantity of dark green precipitate formed in Iron(II) electrolyte, I would assume $\ce{Fe(H2O)4(OH)2}$ precipitate.
A deepening orange in iron(III) solution and a relatively small quantity of orange precipitate, I would assume $\ce{Fe(H2O)3(OH)3}$ precipitate.
pH of electrolytes remained constant (measured with a pH probe).
Conductivity of iron(III) solution remained constant, whilst conductivity of iron(II) solution--which was almost 20 times higher--steadily fell.

It seems to me that similar things are happening at the respective cathodes of the iron(II) and iron(III) cells: both hydrogen gas and iron metal are evolving. The hydrogen gas evolution momentarily increases pH, pushing equilibrium of iron complexes towards the precipitates--thus keeping pH constant.

I'm less sure about the anodes. But I think iron is entering solution as Fe(II) and Fe(III), respectively, with some oxygen evolution.


texts: Does an "excited atom" lose energy gradually?

texts:
When an electron absorbs energy and is in a higher energy orbit (I guess the atom would be in an unstable state), when the electron releases this energy, would all of this energy be released at the same time, or could it release energy one "level" at a time?

So for example if a Hydrogen atom absorbed a lot of energy and its electron went to some level n = 5, could it slowly make its way back down to level 1?


texts: Problem with epoxy silane (Random results in glass silanization). What are crucial points to look at?

texts:
I`m trying to immobilize an antibody onto the glass surface by means of GPTOMS (glycidoxypropyl trimetoxy silane). Using the same protocol (silanization in toluene) I get different results any time, what are key points to check?
Looking through literature on immobilization, I see a lot of articles where authors use APTES (aminopropyl triethoxy silane) and only a few using GPTOMS, why? Epoxy group seems so atractive...
For toluene:

Rince slides with water
Ultrasonicate them in isopropyl alcohol for 3 min, dry them
Put for 3 minutes into piranha solution
Rinse with distilled water
Treat with oxygen plasma for 3 min
Slowly put slides into 2 or 4 % silane solution in toluene, incubate for 3 min
Rince with toluene and isopropyl alcohol.
Put them on dry heater (max temp. of ours is 97 C, most protocols say 110 C), incubate an hour

For ethanol:

Rince slides with water
Ultrasonicate them in isopropyl alcohol for 3 min, dry them
Put for 3 minutes into piranha solution
Rinse with distilled water
Treat with oxygen plasma for 3 min
Put slides slowly into 2% silane in ethanol solution (silane + alcohol + acetic acid (pH 4,5-5,5)), incubate 3 minutes
Rince slides with ethanol
Put them on dry heater (max temp. of ours is 97 C, most protocols say 110 C), incubate an hour


texts:
Ok, so I am working on a project where I have to make a tax for manufacturers using non recyclable materials. So for this tax you multiply the weight (in kg) by how toxic the material is, this gives you an answer in pence. So I have a list of heavy metals that are dangerous to the environment but I don't know what one is the most toxic and the least toxic.

This is what I think the order from most dangerous to least dangerous is:

Selenium (most harmful to the environment)
Arsenic
Mercury
Copper
Lead
Cadmium
Nickel
Chromium
Antimony
Zinc (least harmful to the environment)

Could someone please share their opinion on this order and suggest a better order. Also could someone suggest a suitable number to multiply the weight by to get price in pence.

Thanks


texts: Why does orthocresol behave as a skin irritant?

texts:
o-Cresol or ortho-Cresol or 2-methylphenol is a constituent of tobacco smoke, and, like most other phenols, behaves as a skin irritant, causing a burning sensation when it comes in direct contact, or upon inhaling it in.

What is the biochemical reaction that causes our skin to produce such a reaction to orthocresol? Is there any correlation with orthocresol being an acidic compound? Can this be explained by +I effect or Hyperconjugation effect of the $\ce{-CH3}$ group?

Unlike Vinegar or Alcohol, which have different effects (vinegar feels like water to me, and alcohol has a cooling sensation), why do cresols and phenols in general have a stingy sensation on touching?


texts: Identifying principal quantum numbers in natural population analysis

texts:
Following a Hartree-Fock calculation, I would like my program to perform some kind of Natural Bond Orbital (NBO) analysis. Preceding this I would like to output a list of atomic orbitals, along with their identity (i.e. 2$p$, 3$d$) and their occupancy. The occupancy is simply gathered from a population analysis:

$$ occ_k = 2 \sum_{\mu\in k} (\bf DS \rm)_{\mu\mu} $$

Where $\bf D$ is the density matrix and $\bf S$ the overlap. Of course, the angular momentum of the relevant basis function provides us with the $s$, $p$, $d$, ... character. I understand that to find the principal quantum number $n$, and label a basis function as core, valence, or excited/Rydberg state, you can use the orbital energy (eigenvalues of the Fock matrix) and occupancy, along with some intuition.

My question is, does there exist some algorithm for this task which does not rely on such intuition? I have thought of using some method of 2-objective clustering of the occupancy and orbital energies, but this seems far to over the top for this task.


texts:
Today I was making a pastille of Niobium Pentafluoride powder. The procedure includes a 6 ton squeezer, precision wipes, silica gel, filter papers and acetone.

The first suspicious part was that on product details, $NbF_5$ was suppossed to be $5\mu m$ powder. Instead it looked like having hair(forgive my bad terminology but I am not a chemist, but a physicist and  I don't know how to describe it).

The procedure is the following.

Acetone and wipe papers$\rightarrow$clean squeezers parts(made of stainless steel)
Powder gets into the squeezer(using a funnel made of the filter paper) and gets pressed
The powder becomes a pastille.
It is stored in a plastic bottle, with Silica gel.

The filter paper is also used to fill the bottle with silica gel(as a funnel) as well as a way to store the pastille while filling the bottle with silica gel.

I have made several pastilles with the exact same recipe(i.e. $B,\;ZnF_2,\;LiF$ etc) and everything went fine. This powder however became very sticky. I have also noticed that while it's stored in the silica gel box, there are some drops inside the bottle.

So I have some questions... First of all why did it became sticky and secondly why the powder wasn't actually a powder?Is it typical for $NbF_5$?


texts: Do all electrons in an element move at the same speed and have the same momentum angular vs non-angular momentum?

texts: Do electrons' speed, energy, angular momentum increase when they are in the p, d, and f rather than in the s orbital? Do all electrons in a specific orbital, say for example, the f orbital all have the same speed, energy, angular momentum? Do electrons in the f orbital have higher angular momentum as a result of their distance from the radius or because of their higher speed, energy, or something else?


texts: Calculating the electrons an atom wants to gain/lose to reach a noble gas

texts:
I'm trying to understand ions.

From what I understand, an ion is when the atom gains or loses electrons. More electrons means it is negatively charged (anion). Less electrons means it is positively charged (cation).

My problem is with the following premise:

  Many atoms gain/lose electrons with the hope of having the same number of electrons as the closest noble gas in the periodic table.

The book uses Potassium as an example. Looking at my table, the closest noble gas to Potassium is Argon, which has $18$ electrons. Therefore Potassium wants to lose one electron...

$$\ce{K^+}$$

Nice, I get that. But then I noticed something odd about all the examples in my book: all the elements they picked are elements conveniently one or two steps away from a noble gas. They never picked an element in the middle of the table like, say, iron.

Iron has $26$ electrons. Its closest noble gas is Argon, which has $18$ electrons. So iron wants to lose $8$ electrons (becoming a cation):

$$\ce{Fe^{8+}}$$

Is this correct? My book literally avoids picking elements in the middle of the table, so I feel there's something weird about this.

Also, I noticed that in every example, the book mentions the Group of the element (Potassium is group 1A, etc...). How is that even relevant? All you have to do is count the number of electrons, no?


texts: Distillation for separating very close boiling components

texts:
When components of a mixture have very similar Boiling Points, say 2 C is distillation ever a viable separation procedure at industrial scale?

Assuming one were willing to install a very tall column, say 100 theoretical plates (which with modern high efficiency structured packing can be fit within a column 15-20 m tall), would one expect distillation to work out?

The goal is to get an impurity component to approx. 0.1% starting from a 1.5% initial concentration. The rest of the mixture is the desired product & the BP difference between the two is only 2 C.


texts: Optical isomerism in Co-ordination Compounds

texts:
Optical isomerism in normal organic molecules can be found out by looking for chiral carbon, and the number of isomers can be found out by drawing different spacial orientations of the same.

But, I don't know how to check whether a given coordination compound is optically active or not, and how many optical isomers does it have. I don't know how to draw different spacial orientations with all those polydentate ligands.

I would like to learn the general guidelines for finding optical isomerism in co-ordination compounds. I would like to solve questions like how many no. of optical isomers are there for $\ce{[CoCl2(en)2]^+}$


texts: Assigning 1H NMR spectrum and predicting peak coupling patterns for 2H-1-benzopyran-2-one

texts:
I have a the proton NMR of 2H-1-benzopyran-2-one (2H-chromen-2-one):

There are 6 individual hydrogens and none of them are equivalent. In the spectrum I have been given there are only four peaks.

I have been able to assign two double peaks at chemical shifts 6.43 ppm and 7.73 ppm to the two hydrogens on the alkene in the ring on the left. This leaves the four hydrogens on the benzene ring which should all be non-equivalent, but this spectrum shows them as two 2H peaks. Does this mean they have overlapped, and if so please help me figure out how. Should the multiplicities have been two ddd for the two H's in the middle and then the two H's on the ends should be a dd or ddd?

This is the expansion of those two 2H peaks in my spectra shown below.


texts: If chemical reactions occur because everything tends to a lower energy state, why is there such a thing as equilibrium?

texts: It just doesn't make any sense, if a reaction occurs because the reactants go into a lower energy state, then there should be no such thing as equilibrium. right? Because that would mean that the products are going back into their higher energy states..... Is it just some sort of random chance that they keep changing form?


texts:
In general, when we put potassium into water, it will produce potassium hydroxide and hydrogen:

$\ce{2K + 2H2O ⟶2KOH + H2}$

However isn't the following reaction also possible?

$\ce{2K + H2O ⟶K2O + H2}$

Why isn't the oxide produced?


texts: Would the concentration of oxygen around fire increase as we get close to the fire (from the outside)

texts: Since fire require oxygen, wouldn't a fire, like those in the American forest along west coast, constantly draws in oxygen from around? And if that is so, would the concentration of oxygen around the fire higher than farther away?


texts: Probability of measuring a particle in the ground state: having trouble with the integration

texts:
I am working on a problem in the context of an infinite symmetric potential barrier around the origin, with barriers at $x=- \frac{a}{2}$ and $x=\frac{a}{2}$. The wave function is a symmetric triangle-function:

$$
\Psi (x) = \begin{cases} 0 & x < - \frac{a}{2} \\ \sqrt{\frac{12}{a^3}} \left( \frac{a}{2} - \lvert x \rvert \right) & -\frac{a}{2} \leq x \leq \frac{a}{2} \\ 0 & x > \frac{a}{2} \end{cases}
$$

I must calculate the probability of measuring a particle in the above eigenstate in the ground state (when $n=1$). The way to attack this problem is to calculate the coefficient $c_1$, and then square it. Here follows my (wrong) attempt.

$$
c_n = \int\limits_{-\infty}^{\infty} \psi_n^*(x)\Psi (x)\,\mathrm dx
$$

I understand from the above expression that the $\psi_n^* (x)$ is just the "regular" solution to the particle in a box. Given this symmetric potential, and that $n=1$ (odd $n$, even function), I must set

$$
\psi _1^* (x) = \sqrt{\frac{2}{a}} \cos\frac{\pi x}{a}
$$

The expression for $c_n$ becomes

$$
c_n = \int\limits_{-a/2}^{a/2}  \sqrt{\frac{2}{a}} \cos\frac{\pi x}{a} \sqrt{\frac{12}{a^3}} \left( \frac{a}{2} - \lvert x \rvert \right)\,\mathrm dx \\
$$

Simplifying gives

$$
c_n = \frac{2 \sqrt{6}}{a^2} \int\limits_{-a/2}^{a/2} \cos \left( \frac{\pi x}{a} \right) \left( \frac{a}{2} - \lvert x \rvert \right)\,\mathrm dx
$$

This can be solved by partial integration, setting $u'=\cos \left( \frac{\pi x}{a} \right)$ and $v= \left( \frac{a}{2} - \lvert x \rvert \right)$. Hence, $u=\frac{a}{\pi}\sin \left( \frac{\pi x}{a} \right) $ and $v'=-1$. The integral itself then becomes

$$
\int\limits_{-a/2}^{a/2} \cos \left( \frac{\pi x}{a} \right) \left( \frac{a}{2} - \lvert x \rvert \right)\,\mathrm dx = \frac{a}{\pi}\sin \left( \frac{\pi x}{a} \right)\left( \frac{a}{2} - \lvert x \rvert \right) - \int \frac{a}{\pi}\sin \left( \frac{\pi x}{a} \right) (-1)\,\mathrm dx
$$

Cleaning up

$$
\mbox{Integral} = \frac{a^2}{2 \pi} \sin \left( \frac{\pi x}{a} \right) - \lvert x \rvert \frac{a}{\pi} \sin \left( \frac{\pi x}{a} \right) - \frac{a^2}{\pi ^2} \cos \left( \frac{\pi x}{a} \right)
$$

Now we just need to insert the limits. However, we see quite easily from the above expression that upon inserting $x=\pm \frac{a}{2}$, the last term vanishes, since $\cos ( \pm\pi / 2 = 0)$. The sine terms will equal $1$ when the limit is positive and $-1$ when the limit is negative. Hence, we are left with

$$
\mbox{Integral} = \left[ \frac{a^2}{2 \pi} - \frac{a}{2} \frac{a}{\pi} \right] - \left[ \frac{a^2}{2 \pi}(-1) - \lvert \frac{-a}{2} \rvert \frac{a}{\pi}(-1)  \right] = \frac{a^2}{2 \pi} + \frac{a^2}{2 \pi} = \frac{a^2}{\pi}
$$

Plugging this into the original expression

$$
c_n = \frac{2 \sqrt{6}}{a^2} \cdot \frac{a^2}{\pi} = \frac{2 \sqrt{6}}{\pi} \approx 1.56
$$

So, you see the problem. My $c_n$ is larger than one, which will give me a rather un-physical probability. Am I wrong in this derivation in my assumption for $\psi _n^* (x)$? If not, then where?

Wolfram Alpha gives me that

$$
\mbox{Integral} = \frac{2a^2}{\pi ^2} \\
\Rightarrow c_1 = \frac{2 \sqrt{6}}{a^2} \cdot \frac{2a^2}{\pi ^2} = \frac{4 \sqrt{6}}{\pi ^2}
$$

Using this gives me a probability of $c_1^2 \approx 0.986$, which at least has physical meaning. Also, logic tells me that there is a very high probability of finding the particle in the ground state, so this further backs up WA's answer.


texts: In a Pourbaix diagram (E-pH diagram) where the regions are given , but the assignment of these to the elements we have is not done yet , how can the oxidation numbers helps me out assigning each element in its appropriate region?


texts:
Determine which of the following pairs of reactants will result in a spontaneous reaction at 25 celsius?

Pb2+(aq) + Cu(s)

Ag+(aq) + Br-(aq)

Li+(aq) + Cr(s)

Fe3+(aq) + Cd(s)

None of the Above.

I've tried using using tables like this http://ch302.cm.utexas.edu/images302/Electrochemistry_Reduction_Potentials.jpg to use the equation Ecell = Ecath - Eanode.

I'm hoping anyone could answer the question, and explain why each of them could be, or could not be spontaneous. (I know that an Ecell being positive results in spontaneity).

Here's my work:

Pb2+(aq) + Cu(s)

.34-(-.13) = .47

Ag+(aq) + Br-(aq)

.80 - (.76) = .04

Li+(aq) + Cr(s)

-.90-(-3.05) = 2.15

Fe3+(aq) + Cd(s)

-.04 - (-.81) = 77

None of the Above.

As you can see, they're all spontaneous. I'm wondering if I grabbed the wrong values from the above table. The question asks about ONE spontaneous reaction, from my calculations, they're all spontaneous.

@MichaelD.M.Dryden


texts: How were the elements discovered before modern technology?

texts:
I recently was in need of zinc for an experiment. So I resorted to obtain it from some dry cell. But I wondered if it was pure zinc or was it $\ce{ZnO2}$ or any other compound of $\ce{Zn}$. It then occurred to me that I had knowledge of existence of pure $\ce{Zn}$ and its compounds, but how would its discovery have happened without the prior knowledge of its existence?

How did scientists discover the elements without knowing of their existence and unique properties?

Modern day scientists rely on technology and advanced nuclear physics. But in absence of these advances, how were ancient scientists able to discover them?


texts:
I am studying molecular bond theory, and I see that sometimes this happens.
Does this have some significance to the molecule?


texts: What is mass-independent isotope separation/fractionation?

texts:
How can any separation/fractionation of isotopes be mass-independent, if the only difference between two isotopes is mass?

The only clue(s) on Wikipedia mention molecular symmetry, 'forbidden' spin-flip transitions/reactions and photochemical dissociation....

But how is any of that affected by an extra neutron?


texts: Mechanism of dehydrogenation with nosylate

texts:
What is the mechanism of the attached reaction? How could nosylate do the dehydrogenate the species?

The reaction is from this synthesis (46th IChO preparatory problem 26):


texts:
I was reading Silberberg's principles of general chemistry when I noticed that it says that the mass of carbon12 is exactly 12 amu.
But when I calculated the total mass of its components    (6 protons : 1.00727 amu each , 6 neutrons : 1.00866 amu each and 6 electrons : 0.000548 amu each) it was obviously greater than 12. Why is that?

My explanation was that some of the mass is converted to energy but I don't know whether it was true or not.

And I'm sorry if my English is not good.


texts: How slow is a ester reaction without a catalyst? (in a whiskey barrel?)

texts:
The typical description of a high school esterification reaction of an alcohol and an organic acid uses a strong acid catalyst like $\ce{H2SO4}$; otherwise the reaction is said to be "slow".

I would like to know, how slow? For context I am interested in the esterification reaction which happen in the time frame of distillation of whiskey and whiskey maturing in a barrel.

New spirit (what goes into a barrel to age and become whiskey) is approximately 60% EtOH, 39% water and less than 1% (I think) other alcohols, and organic acids like acetic and lactic acid.

How long would this system take to come to equilibrium, without any catalyst? (Hours, days, months, years?)


texts: Can sulfuric acid itself be electrolysed?

texts:
We all could know by now that water can be electrolysed by adding some sulfuric acid.:)

But is it possible that the sulfuric acid itself becomes electrolysed when the concentration of the acid in the water gets higher ?

Would it give sulfur dioxide or sulfur trioxide ?


texts: How to find the mass of the solute given a concentration as a mass fraction?

texts:
Formalin is a $37\%~\mathrm{W/W}$ solution of methanal in water. What mass of water must be added to $250~\mathrm{g}$ of methanal to make formalin.

Here's what I've done so far. It's wrong though. According to my book answer is $430~\mathrm{g}$ $\ce{H2O}$.

$$\frac{Cw}{w} = \frac{\mathrm{m\ solute}}{\mathrm{m\ solution}} \cdot 100\%$$

$$37 \% = \mathrm{\frac{m\ solute}{250} \cdot 100\ \%}$$

$$\mathrm{\frac{37}{100} = \frac{m\ solute}{250}}$$

$$\mathrm{0.37 \cdot 250 = m\ solute}$$

$$\mathrm{m\ solute = 92.5\ g}$$

Where have I went wrong? Am I completely off or at least close?


texts:
Which of these substances is more soluble in $\ce{CCl4}$?

  $\ce{CH3F}$
  $\ce{I2}$
  $\ce{Na2SO4}$
  $\ce{HCl}$

How do I even solve this kind of exercise?

My guess is that $\ce{CCl4}$ is non-polar. Therefore the substance we're gonna need must be non-polar as well. The only non-polar substance is $\ce{I2}$ so that should be the answer.

Is my reasoning fine and, more importantly, is there another way to solve this kind of problem? What if they give me two options that are non-polar?


texts:
I'd really like to know what compound this formula is and don't know if there's any software for that matter, if anyone could help me :)
(With a sw suggestion or the compound identification)


texts: How are non-Stoichiometric compounds determined?

texts:
For solids where the compound contains defects, the stoichiometric equation deviates from the "pure" one. How are these compounds determined? I am looking in my chemistry book but I do not see anything on it. Are there some resources on this?

UPDATE:

After doing some thinking, I considered the Auger Electron Spectroscopy technique used to study the composition of surfaces in materials science. These , I believe, are typically used to study the amount of defects in materials. I do not know how this would be applied to the situation I described above though (as this is only applicable to surfaces). I will continue searching.


texts: Magnetic and acidic properties of nitric oxide

texts:
I was faced with the following question:

PART C – CHEMISTRY
Which one of the following properties is not shown by $\ce{NO}$?

It combines with oxygen to form nitrogen dioxide

Its bond order is $2.5$

It is diamagnetic in the gaseous state

It is a neutral oxide

I am confused about (3) & (4). I know $\ce{NO}$ reacts with water & oxygen to produce $\ce{HNO2}$, and then $\ce{NaOH}$ to produce $\ce{NaNO2, N2O, H2O}$. So, obviously it's acidic.
But there is one unpaired electron in the $\ce{N}$ atom. So, I see no reason for $\ce{NO}$ to be diamagnetic in gaseous state.
But, these questions do not have two correct answers. So, one of them has to be wrong. I am not sure which one.


texts: Can an antioxidant be considered a catalyst?

texts: I'm doing some research and I've come across antioxidants which are described as substances that slow down the oxidation process. Based on this definition, could antioxidants be considered catalysts? Because, a catalyst is described as something that changes the rate (not nessecarily making it faster?) of a chemical reaction but remains unchanged during the reaction.


texts: What does the equilibrium constant mean for reactions with very small concentrations?

texts:
When you calculate the equilibrium constant for a reaction with a higher concentration of reactants, the answer is fairly intuitive. For example, for the reaction:
$$\ce{A + B <=> C}$$
Where we have $0.10 M$ of A, $0.30 M$ of B and $0.45$ M of C the equation for the equilibrium constant is:
$$ K = \frac{[0.45]}{[0.10][0.30]} = 15$$
This is relatively intuitive, we can see that the concentration of C is larger than the product of A and B and so saying the products are favoured makes sense.
However, an issue comes about when you consider really small amounts of all of them. For example, for the same reaction
$$\ce{A + B <=> C}$$
If we have $2.4*10^{-4} M$ of A, $2.4*10^{-4} M$ of B and $7.5*10^{-6} M$ of C we have the equation:
$$ K = \frac{[7.5*10^{-6}]}{[2.4*10^{-4}][2.4*10^{-4}]} = 130$$
In this case, the equilibrium constant suggests the products are favoured but if you look at how much product we have compared to reactants there's so much more reactants than products. The constant makes sense since multiplying two numbers less than 1 will get a smaller number but it's confusing when you consider the implications that has on the equilibrium. My immediate assumption is that I am misunderstanding the relationship between the equilibrium constant and the concentrations of species in the reaction and if this is the case is there a more intuitive way of looking at this?


texts:
For the reaction
$$\ce{1/2 N2(g) + 3/2 H2(g) -> NH3(g)}$$
$ΔG$ at $\pu{298.15 K}$ is $\pu{-3980 cal},$ and the change in enthalpy is given by the expression:
$$ΔH = -9.19 - 7.12T + 3.182\cdot 10^{-3}T^2 - 2.64\cdot 10^{-7}T^3$$
Calculate $ΔG$ at $\pu{1000 K}$ from these data. Note: use the expression
$$\left[\frac{∂}{∂T} \frac{ΔG}{T}\right] = \frac{-ΔH}{T^2}$$
integrate the resulting expression of the $ΔH$ given.

This is what I understood so far. Using the given expression of the partial derivative I integrated on both sides:
$$∫\left[\frac{∂}{∂T} \frac{ΔG}{T}\right] = - ∫\frac{ΔH}{T^2}$$
I put the given expression of $ΔH$ on the right side of the integral.
$$∫\left[\frac{∂}{∂T} \frac{ΔG}{T}\right] = - ∫\frac{-9.19 - 7.12T + 3.182\cdot 10^{-3}T^2 - 2.64\cdot 10^{-7}T^3}{T^2}$$
Eliminate the $T$ where I could:
$$∫\left[\frac{∂}{∂T} \frac{ΔG}{T}\right] = 9.19 ∫\frac{1}{T^2}\mathrm dT + 7.12 ∫\frac{1}{T}\mathrm dT - 3.182\cdot 10^{-3}∫\mathrm dT + 2.64\cdot 10^{-7} T^3∫T\mathrm dT$$
$$\frac{ΔG}{T} + C = -\frac{9.19}{T} + 7.12\ln T - 3.182\cdot 10^{-3}T + 1.32\cdot 10^{-7}T^2$$
To get $ΔG$ I evaluated the final expression from $298.15$ to $\pu{1000 K}$ and got that
$$\frac{ΔG}{T} + C = 126.6707439$$

Since the expression from the integral is all temperatures, why I don't get units of energy instead? Am I missing something during the integration?

If I am not missing anything, the $126.6707439$, whatever unit it has, is that the $ΔG$ at $\pu{1000 K}$ I am supposed to get?


texts: Why aqueous ammonia is added to glucose solution to determine optical rotation?

texts:
In order to determine the specific rotation of glucose, it was mentioned in a practical chemistry book that 10g of dehydrated glucose must be dissolved in 80ml of water, then, adding 0,2ml of aqueous ammonia. After 30 minutes, we have to complete with 100ml of water.

For me, I would prepare only a glucose solution to use in the polarimeter.

So why aqueous ammonia have to be added to the glucose solution ? and why completing with 100ml of water after exactly a half-hour? (What happens during that half-hour?)

Note : This is not a homework. I'm a pharmacy student and this is a part of the lab work I'll have next week.


texts: Do alkylhydroxylamines form N-nitrosamines?

texts:
Usual secondary amines can form N-nitrosamines with nitrosating agents, e.g., $\ce{KNO2}$, and are therefore forbidden in metalworking fluids.

But can alkylhydroxylamines form N-nitrosamines with nitrosating agents in metalworking fluids?

I assume the basicity of the N-atom in alkylhydroxylamines is lowered by the inductive effect and the mesomeric effect. But is this enough to prevent formation of N-nitrosamines?


texts:
How do we arrange the following in increasing order of stability?

The answer given is: $5<3<1<2<4$ (numbering according to their order in the image).

My Approach:

I can figure that in the second and the fourth structure, resonance stabilization will be applicable and the fourth structure will be more stable than the second.

But I am not able to figure out how do I arrange the remaining structures.


texts: What do the quantum numbers actually signify?

texts: I know how to calculate them and such stuff, but I wanted to know what they actually signify. I have a vague idea that they have something to do with an electron's position in an atom but what do all of them mean? Any help would be greatly appreciated!


texts: Stability of Halide Salts of Different Metals

texts:
Between $\ce{EuCl3}$, $\ce{RuCl2}$, and $\ce{VCl}$, order in
  increasing stability.

I don't know if this is a dumb question and if the answer is blatantly obvious, but I don't understand how to "solve" this question. Is there a rule that determines the stability of chloride salts / any salt in general that can be applied by just referring to a periodic table?

(My rationale for this problem was that Eu and Ru have 3+ and 2+ charges, respectively, and since Eu's 3+ oxidation state would empty both its s-orbital and d-orbitals and Ru's 2+ state would empty its s-orbitals, the complex would be able to form (Just to show that I've done work) but that honestly seems obviously wrong as well.)

This is not an HW question.


texts: Relating collision theory to rate of reaction

texts:
I want to relate the macroscopic advancement of a reaction, the rate of the reaction, with the microscopic collisions of the molecules. This is the type I have developed so far:

$$u = A^2 \times \frac{n_1}{m^2} \times\frac{n_2}{m^2}\times \frac{(m_1u_1^2+m_2u_2^2)}{E_\mathrm{act}}\times 1/t $$

where $u$ is the rate of reaction in $\pu{mol2 sec-1}$.

$A =$ the common area of the substances

$n_1/m^2 =$ the moles per square metre of the first substance

$n_2/m^2 =$ the moles per square meter of the second substance

$u_1$ and $u_2 =$ average velocity of molecules of each substance

$E_\mathrm{act} =$ activation energy of the reaction

Now the molecules of the first substance must bump to the molecules of the second substance with the appropriate orientation. How can I add this to my type?


texts:
Does the spectrum of Methylene Blue change on prolonged exposure to light?
I've studied about the photochemical reactions and about energy transfer reactions. Methylene Blue is a triplet sensitizer used for the production of singlet oxygen through energy transfer reaction, can this formed singlet oxygen attack methylene blue? Why is leuco(colorless) form of Methylene Blue is formed?

One more thing is still confusing me, while the energy transfer reaction we say that energy is transferred from sensitizer to another molecule, but which form of energy is transferred is the light or heat energy, if it is light energy which is transferred then the light of same wavelength is transferred which caused the excitation of the sensitizer?

If anyone can please help me through these confusions...


texts: Helicity in Molecular motors and topological isomers

texts:
I'm working on a project to understand the work of the 2016 Nobel laureates and I've come across a problem of not being able to find the right sources to understand basics of helicity (more specifically right-handed
helicity (M) and lefthanded helicity (P)) to understand things like the diagram below (I understand cis, trans, I don't know much about the (P,P) and (M,M)).

I would like some suggestions for books or articles that would help me learn more about these concepts.

Thanks in advance!


texts: Intuition for why effective nuclear charge increases down a column

texts:
My textbook (Chemistry the Central Science, edition 12, Brown et al.) says that effective nuclear charge increases down a column. Indeed, this is consistent with the values provided by Clementi in the 1960s.

Is there intuition or some qualitative explanation for why effective nuclear charge ($Z_\mathrm{eff}$) for the outermost electrons increases down a column (as opposed to being roughly equal)?


texts: Why is there such a violent reaction when NaCl is formed?

texts: In school I saw how $\ce{NaCl}$ was formed and I noticed that there was a violent reaction. Can someone tell me why there is such a violent reaction? The $\ce{NaCl}$ was formed by reacting sodium metal and chlorine gas.


texts: What is the difference between convection and conduction?

texts:
I was having a conversation with my dad the other day and he described something as happening due to convection, and it dawned on me that I have no real clue what the difference between and convection and conduction is.

I started to do some reading on this and haven't really found any good clarification.

Here is what I do understand:

Convection:

Involves transfer of heat within a single substance by mass flow
Does not take place in solids due to a solid's inability to behave like a fluid
The heat flow is governed by diffusion of higher energy molecules and thus a distribution of that energy evenly, or by advection which basically seems to be bulk diffusion to me

Conduction:

Transfer of heat within a body by diffusion
This diffusion differs from convection because convection supposedly happens through a material carrier
Can take place in solids

Confusion:

No doubt, some of the points I just put up there are wrong or else I basically see no point in making a distinction between convection and conduction when the processes can be described more easily by diffusion which redistributes energy by principle of maximizing entropy.

So why define these two different terms when they are essentially the same process perhaps just happening in different mediums?

Contradictions:

I was looking at the Wikipedia pages, which I usually find to be reliable, for convection and conduction and was only confused more.

For instance, from the conduction page:

  "In gases and liquids, conduction is due to the collisions and diffusion of molecules during their random motion."

Now, from the convection page:

  "Convective heat and mass transfer take place both by diffusion – the random Brownian motion of individual particles in the fluid – and by advection, in which matter or heat is transported by the larger-scale motion of currents in the fluid."

Those two statements seem to be basically the same. The mechanism for the heat transfer is the diffusion of randomly moving moving particles.

On the other hand, the conduction page explains that conduction takes place in solids through,

  "In solids, conduction is mediated by the combination of vibrations and collisions of molecules, of propagation and collisions of phonons, and of diffusion and collisions of free electrons."

That seems like a perfectly good explanation of what takes place when heat is being distributed towards thermal equilibrium in a solid.

Questions:

What about the above statement that conduction in solids is mediated through collisions of electrons and vibrating atoms makes that process conduction rather than convection?

What of the above points are incorrect?

On a molecular level, (i.e. using typical chemistry ideas) what makes a distinction between convection and conduction?

Finally, what is meant by the statement that convection happens through a material carrier?

Does that imply that conduction does not happen through a material carrier? If so, how?

I hope you can see my confusion between these two terms. They seem very convoluted to me.

I would point out that good and correct answer need not address each of my sub-questions specifically because a good answer may clear up my confusion and hence eliminate one of those sub-questions.


texts:
I had an interesting event occur recently: I stuck a screwdriver in a potted plant, for it is the only way that I am able to unlock a certain door. It was left in there for about a month before I needed it again, and, when I took it out, it had what I thought to be rust. I am doubting my original assumption.

I know for a fact that it is not dirt itself, as I vigorously attempted to clean it with suds (though I'm not entirely sure whether or not that was the best approach...).

Question

Does iron a) oxidize in dirt and b) if a), does it oxidize faster in dirt?


texts: What is the role of NaCl in the functionalization of gold nanoparticles?

texts:
In the functionalization of gold nanoparticles (GNPs) through the sulfur-metal bond, this article (among others) states that $\ce{NaCl}$ is slowly added in the GNPs solution after addition of thiol compound.

What is the role of $\ce{NaCl}$ in the functionalization step?


texts: Is this textbook bonding picture of hybridization in ethene wrong?

texts:
Regarding the above picture, why is the $\ce{C-C}$ $\sigma$ bond composed of two $\ce{sp^2}$ orbitals while the $\ce{C-H}$ $\sigma$ bonds composed of $\ce{sp^3}$ hybrid orbitals? I don't see why; I thought the geometry around the carbons was trigonal planar. Why does hybridization differ across atoms in the molecule?

I'm thinking the textbook authors made a mistake; yes, there are four $\ce{C-H}$ bonds, but this does not mean there is $\ce{sp^3}$ hybridization because there are two carbon atoms, each with two $\ce{C-H}$ bonds and one $\ce{C-C}$ bond. Perhaps the authors mistakenly took there to be one carbon and four $\ce{C-H}$ bond (i.e. methane.) That would be $\ce{sp^3}$ hybridization.

Or perhaps I'm wrong altogether. Please enlighten me!

EDIT: Saw this in another text:


texts: D-Threose: reduction and optical activity

texts:
I've bumped into this exercise:

  Judging by the mechanism of reaction between D-threose and $\ce{NaBH4}$, do you think the final product will be optically active?

To me looks like a reduction, since $\ce{NaBH4}$ is a lightly reductive agent, but then why the answer is "No, the product is not optically active"?

Is it because of the presence of anomers or there are other reasons?


texts: What would be a suitable non-combustible lubricating oil or compound for a very high pressure air compression system?

texts:
This question came up at Engineering SE but remains unanswered.  If we are compressing regular air, not nitrogen, what oil or compound can be used
that would not combust  with the oxygen in the air.  High pressures cause high temperature which would ignite hydrocarbon based oils.  What compressor or pump lubricant would be suitable in these conditions?

With Internet search, I found this compound, but it is a grease intead of oil and there is no mention of ability to withstand high pressure.


texts:
"Wüstite is often represented as $\ce{Fe_{1-x}O}$, where $x$ is some small fraction less than unity. In this nonstoichiometric $\ce{Fe_{1-x}O}$ material
conduction is electronic and the material behaves as a p-type semiconductor, i.e. the $\ce{Fe^3+}$ ions act as electron acceptors, generating holes.

Determine the electrical conductivity of a specimen of wüsite that has a hole mobility of $\pu{3.1E-5 m2 V-1 s-1}$ and for which the value of $x$ is 0.030. Assume that the acceptor states are

saturated, i.e. one hole exists for every $\ce{Fe^3+}$ ion. Wüsite has a sodium chloride crystal structure with a unit cell edge length of 0.437 nm."

My Solution:

4 units of $\ce{FeO}$ for rocksalt structure but for every $\ce{Fe^2+}$ vacancy $2$ $\ce{Fe^3+}$ are needed for electroneutrality, this implies $0.003:1\rightarrow0.24:4$

$$\mathrm{mass}_{\ce{Fe(III)}}=((0.24)(55.85))/((N_a)(10^3))$$
$$=\pu{2.225838592E-26 kg}$$
$$\rho_{\ce{Fe(III)}}=2.225838592\times10^{-26}/(4.37\times10^{-10})^3$$
$$=\pu{266.7 kg m-3}$$
Conductance for a p-type semiconductor is given as: $$\sigma=p(q)(\mu_{h})$$
$$\implies\sigma=(266.7)(1.6\times10^{-19})(3.1\times10^{-5})$$
$$\approx1.3\times10^{-21}\:(\Omega.m)^{-1}$$

I have the feeling this is wrong so any help would be appreciated.


texts: Why does benzene have a D6h point group?

texts: I understand the fact that the molecule has a principal axis of rotation of C6 however when following the point gorup flow chart why is the answer to the second question NO when it contains two C3 axis? Hence the answer should be a YES right? (I understand the molecule has C2 axis as well)


texts:
Does anyone know if the casein/whey cows milk protein can be found within processed lactose?

Some background: our 4-month-old baby was given teething granules. She was then presented with a rash, screaming, etc. When we checked the teething granules (called teetha) we found they contain lactose.

However, from reading it appears that lactose intolerance is extremely rare in the UK and cows milk allergy is much more common.


texts: Bonding in Square Antiprismatic Compounds

texts:
Both $\ce{IF_8^-}$ and $\ce{XeF_8^{2-}}$ have (distorted) square antiprismatic geometries.

I've been wondering how to explain the bonding in such compounds.  Hypercoordinate bonding (as used to explain the bonding in $\ce{PCl_5}$, for example) doesn't seem to work in these cases.  Nor does the resonance explanation used in the case of $\ce{IF7^-}$ (which would involve something like $\ce{XeF_8^{2-} <-> XeF6 + 2F-}$ in this case) seem very strong.  Can the bonding and geometry in the above octacoordinated compounds be explained using  s and p orbitals?


texts: Where does the pH come from in the equation of Standard Hydrogen Electrode?

texts:
$$\mathrm{E=-{2.303RT \over F}pH - {RT \over 2F}\ln {p_{H_2}/p^0}}$$
This is a equation on Wikipedia page of Standard Hydrogen Electrode, but I have no idea where the $pH$ come from.
Since $\mathrm{a_{H^+}=f_{H^+} C_{H^+} /C_0}$, how does the $\mathrm{f_{H^+}}$ disappear?


texts:
Solomons and Fryhle has an example in which they have showed a very simple substitution reaction. The question was to synthesize methyl iodide. What they have done is taken methyl chloride and produced methyl iodide in the presence of $\ce{NaI}$ and ethanol through an $\mathrm{S_N2}$ mechanism.

Why did they use ethanol? I have read that $\mathrm{S_N2}$ reactions are favored under polar aprotic solvents and clearly ethanol is not that. Also, since it's a methyl and all substitution reactions on methyl go through $\mathrm{S_N2}$; so how would it affect my reaction if I would't use ethanol?


texts:
What is the hybridization of oxygen in phenol molecule? I assume it is $sp^3$ hybridized because it forms 2 bonds - 1 with benzene, another with hydrogen, as in how oxygen is hybridized in a water molecule - $sp^3$.
Now the problem is, my A - level lecturers insist that it is the p orbital of oxygen that overlaps with the delocalised electrons of benzene ring, not $sp^3$. This means that oxygen can either be unhybridized, $sp$, or $sp^2$ hybridized. So which is true?


texts: What chemistry lab experiements can I do based on the bicarbonate buffer system?

texts: I want to do a chemistry experiment, based on the reactions present in the bicarbonate buffer system. It needs to be heavily chemistry based, rather than biology based-- any suggestions  preferably based on a factor other than pH for the independent variable (pH can be dependent variable)? Especially preferable if they don’t involve the use of a pH meter, and can be clearly tied to chemical principles. Thanks!


texts: A very typical example of a compound of peroxide is $\ce{H2O2}$. When like the title says, will such compounds form, despite usually oxygen will have a oxidation number of 2-?


texts:
How does the electron from the 2s orbital "jump" to the 2p, thus leaving 4 unpaired electrons to form four covalent bonds?

Also, does the octet rule not apply to carbon? If it does, how can it bond with only two electrons? It would lack two more.


texts: Why is in the reaction of hydrogen peroxide and sodium hypochlorite, singlet oxygen obtained? Why isn't triplet oxygen produced instead, as it is thermodynamically more stable?


texts: Is this amide compound electrophilic enough to be attacked by a cyclopentadiene in base?

texts: I am trying to make a fulvene molecule with dimethylamino and phenyl substituents. My worry is that the amide group donates electron density into the carbonyl carbon making it less electrophilic.


texts: Energy of photons of given frequency and number

texts:
I’m having trouble with calculating the energy of $\pu{5.00E10}$ photons of frequency $\pu{1.00E9 s-1}$.
I know that to calculate the energy $E = hf$ is to be used. However, I am unaware as to what to do with the $\pu{5.00E10}$ value and its meaning.


texts: "The centre of positive and the centre of negative coincide" What does that mean?

texts: I'm doing AS level chemistry right now and my teacher told us that when a molecule is non polar , the centre of positive and the centre of negative coincide , I don't really get what he means by that .


texts: Why does mercury decolourise a gold ring?

texts:
I saw that a gold ring decolourised as it got in contact with mercury .
Why does this happen ? Is there any way to reverse this?


texts: How do you know if electron is deexciting or exciting itself?

texts:
I got a question which goes like this:

  According to Bohr's theory, the electronic energy of H-atom in the n th Bohr's orbit is given by $$E_n=\frac{-21.7*10^{-12}}{n^2}J$$ Calculate the longest wavelength of electron from the third Bohr's orbit of the He+ ion.

For longest wavelength transition, we need lowest energy transition. Therefore the electron can de-excite to $n=2$ or excite to $n=4$. I do not need the answer to the question, but I need to know how to know if the electron is exciting or de-exciting.

From what I know, I think it would be exciting to $n=4$ since the energy is lesser than de-excitation energy.


texts: I'm puzzled as to what can happen to phenolic acids when they are heated. (Chemistry, not health or food science) How do they dehydrate? Do they form anhydrides? Also, is it possible for the carboxylic acid part to form an anhydride with an ortho phenol group (given that the COOH group is on a sufficiently long alkyl chain).


texts: Why $\ce{H3PO2}$ does not form an acid salt? I didn't understand the language.


texts: Explain the selectivity in bromination of this compound with two substituted benzene rings

texts: As I know, when $\ce{Br2/FeBr3}$ is added to acetophenone ($\ce{C6H5-CO-CH3}$), Br will substitute a H from the meta position which leads to 3-bromoacetophenone. So why doesn't a Br substitute a H from the right side benzene (connected to the carbonyl group)?


texts: Understanding energy level splitting of an octahedral complex from spin-orbit coupling, 1st and 2nd order zeeman effects

texts:
While studying notes from a couple years ago, I encountered a diagram that I don't have further information on but would like to understand.
While I believe I managed to find sources to guide me through the details of the calculation, there are a few conceptual questions I had, which are summarized at the bottom.
The diagram is for a $d^1$ octahedral complex under a magnetic field:

a) ligand field splitting
b) Spin-Orbit coupling
c) First-order Zeeman splitting
d) second-order Zeeman splitting
a)
The ligand-field splitting is straightforward to me.
b)
The spin-orbit coupling I believe I understand.
The $E_g$ level does not have an electron, and therefore does not undergo any spin-orbit coupling.
For the $t_{2g}$ energy level splitting, I followed the procedure covered on pages 9 and 10 here (the formula is also given on the wiki). The formula for spin-orbit coupling is:
$$\Delta E=\frac{B}{2}[j(j+1)-l(l+1)-s(s+1)]$$
For a $^2D$ term, $l=2$ and $s=\frac{1}{2}$. Then $\Delta E$ would be:
$$j=\frac{5}{2}\therefore \Delta E=\frac{3}{2}B$$.
$$j=\frac{3}{2}\therefore \Delta E=-B$$
I assume in the diagram, $\zeta=B$.

Why does the diagram obtain different coefficients ($-\frac{1}{2}\zeta$ and $\zeta$)? Did I do this wrong?

c)
I think I might have understood this one, using the following link. I'll be referencing equations from this link for these two sections. I'm substituting the Bohr Magneton, $\mu _B$ with simply $\mu$, as it renders better this way, and replacing $B_{ext}$ with $B$ for the same reason.
In deriving equation 8.15 from the link, I am confused what is meant by the line

let the hermitian, unperturbed hamiltonian $H_0^\dagger =H_0$ "act to the left" on $\langle n^0|$

I have never used an operator to "act to the left." I've always applied it toward the right.
Assuming it somehow works out to $E_n^0$, I understand how theorem 8.1 is obtained:
$$E_n^1=\langle n^0|H_I|n^0\rangle$$
They apply the above theorem in equation 8.25 with $H_I=H_z$, where
$$H_z=\frac{\mu}{\hbar}(L_z+2S_z)B$$
to obtain:
$$\Delta E =\mu (m_l+2m_s)B$$
In my diagram above, $m_l=2$ and $m_s=\frac{1}{2}$, so
$$\Delta E = \mu (2\pm 1)B=3\mu  B-\mu B$$
$$= 2\mu B$$
That seems to match the diagram (where $B=H$).

Why does the $E_g$ level split into two double degenerate levels, and the ground state $\Gamma _8$ (4) not split at all?

d)
For second-order splitting, the linked PDF provided this formula (theorem 8.3):
$$E_n^{(2)}=\sum_{m\ne n}\frac{\left| \langle m^0|H_I|n^0\rangle \right| ^2}{E_m^0-E_n^0}$$
I was unsure how this relation was true:
$$(\langle n^0|H_I|m^0\rangle )(\langle m^0|H_I|n^0\rangle )=\left| \langle m^0|H_I|n^0\rangle \right| ^2 $$
but otherwise followed the derivation. Accordingly, the numerator indicates the 2nd order zeeman correction is simply the square of the first order correction; however, the denominator I did not follow, namely:
$$E_m^0-E_n^0=3\zeta$$

Where does this $3\zeta$ come from?
Similar to the first-order splitting, why do the energy levels experience different types of splitting?

summary of questions

In section b), why are my splitting coefficients different from the diagram?

In section c) of the diagram, why is the highest-lying energy level in the diagram split into two double degenerate levels, the middle-lying energy level split into two singly degenerate levels, and the lowest-lying energy level not split at all? I assume the answer to this question will also explain why the second-order splittings in section d) are also inconsistent with each other.

In section d) of the diagram, how does the $3\zeta$ term in the denominator for the energy splitting come about?

What is responsible for certain energy levels being doubly degenerate after following splitting from the Zeeman Effect?

Where does the term symbol splitting according to the projection of total angular momentum along the axis of the magnetic field, ie. $j_z=j,j-1,...-j$ fit in here? Aren't these also separated in a magnetic field?


texts:
I'm a collector of historical artifacts, and one of the most common methods to preserve them is waxing. And one of the best options out there is Renaissance Wax, a microcrystalline wax. The reason it is considered superior to natural options like beeswax is that it is PH neutral, meaning it will not corrode the artifact over time with its acid content.

My only hesitancy to continue using it would be that it is petroleum based. I'm curious if any natural waxes offer the PH neutrality that RW does, as well as being just as long lasting for protecting items from moisture.


texts: Alphabetization rule in case of consecutively placed substituents

texts:
This is the compound:

I am stuck on assigning the locants to the given halo substituents. We know that all halogens are of equal priority. So, using first point of difference, we get either an $\ce{I \rightarrow Br \rightarrow Cl}$ path or a $\ce{Cl \rightarrow Br \rightarrow I}$ path. I am confused as to which of the two paths I should choose. I could choose alphabetical order, but the bromine in between is ruining the alphabetical order of C-I

Is there any new theory that I am missing?


texts: What will be the product of following Wolf-kishner reduction?

texts:
Question

Attempt

1.Wolf kishner would reduce double bond oxygen to alkane.

2.Also since water is present acetal should break.

3.SnAr doesn't seems possible due to adjacent bulky groups.

So according to me answer should be C
 But why am I wrong?
Please help.


texts:
The problem gives that the solubility of Silver dichromate is $8.3\times10^{-3} g/100mL$. I need to find $K_{sp}$ which is supposed to be $2.8\times10^{-11}$.

$K_{sp}$ is $\ce{[Ag+]^2[Cr2O7^{2-}]}$

I changed the $8.3\times 10^{-3}$ from g/mL to mol/L and got $1.9\times 10^{-8}$.

Silver dichromate breaks into 2 Ag and one dichromate.

So that would be $(2 \times 1.9\times10^{-8})^2 \times ( 1.9\times10^{-8})$

That's what I did but it's not giving me the right answer. Where am I going wrong here?


texts:
My professor says that the internal energy of a gas is the sum of its kinetic energy and potential energy: $U = E_k + E_p$.

It also says that the root-mean-square speed of gas molecules is $v_{rms}=\sqrt{\frac{3RT}{M}}$. Rearranging this formula gives: $E_k = 1/2*M*v_{rms}^2=3/2*R*T$.

Further, my textbook also says that the potential energy of an ideal gas is 0, because there are no attractive or repulsive forces in the gas.

Then, it seems as though the first equation becomes: $U = 3/2*R*T + 0 = 3/2*R*T$, but we know that the internal energy of an ideal gas is not always $U = 3/2*R*T$; it changes based on the state (constant temperature or constant pressure) and the geometry of the gas molecule (monatomic, diatomic, or nonlinear).

What am I missing?


texts: Calculation of dispersion energy in Gaussian 09

texts: How can I calculate the dispersion energy using Gaussian 09? Where is it printed in the output file when using wb97xd/cc-pvdz sp? If it isn't printed by default, what flags can be used to turn printing on?


texts:
Given a solution with a $\ce{S^{2-}}$ (sulfide ion) concentration of $2.76 \times 10^{-15}$ mol per litre, and $K_s(\ce{FeS})=4.90 \times 10^{-18}$, calculate the solubility of $\ce{FeS}$ in this solution.

I calculated this by letting the concentration of $\ce{Fe^{2+}} = x$, therefore the concentration of $\ce{S^{2-}} = 2.76 \times 10^{-15} + x$.

Therefore $4.90 \times 10^{-18} = x(2.76 \times 10^{-15} + x)$.

Upon solving this as a quadratic equation, I arrive at the result of $2.14 \times 10^{-9}$ mol per litre.
[EDIT: $2.21 \times 10^{-9}$ mol per litre]

The answers to this problem state to ignore the contribution of $\ce{S^{2-}}$ from the $\ce{FeS}$ as it is negligible, and state that the answer is actually $1.78\times10^{-3}$ mol per litre.

Which method is correct?


texts: Reactivity comparison between benzaldehyde and acetaldehyde

texts:
One of my teacher says that $\ce{Ph-CHO}$ is more reactive than $\ce{CH3-CHO}$ in performing nucleophillic addition reaction because $\ce{—Ph}$ is planar and thus offers less steric hindrance as compared to $\ce{—CH3}$ which is tetrahedral.
My other teacher gives the reason that the partial positive charge developed on the carbonyl carbon is resonance stabilised in $\ce{Ph-CHO}$ which makes the carbonyl carbon more prone to nucleophillic attacks.
What I think is that $\ce{—Ph}$ has its −I effect which deprives the carbonyl carbon of some amount of its electron density and thus makes it more prone to nucleophillic attacks.
I want to know which reason is more correct in explaining the reactivity of  benzaldehyde over acetaldehyde or if there is some other reason please specify.
The main thing I want to know by this is that whether planar substitutents offer less steric resistance than tetrahedral or not, and whether a partial charge on carbon can be stabilised by resonance or not.


texts: Why is the dipole moment of ethyl chloride larger than that of vinyl chloride?

texts:
The dipole moment of ethyl chloride is 2.10 D (J. Mol. Struct. 1990, 216, 9–26), and that of vinyl chloride is 1.42 D (J. Chem. Phys. 1960, 32 (1), 205–209).

Why is this the case? I would have thought that hyperconjugation would lead to vinyl chloride possessing a larger dipole moment instead.


texts:
One day, there was a fly in my house. I really hate insects flying around me, but I don't want to catch it with my hands, so I sprayed some insect repellent directly onto the fly to try to get rid of it.
This is the insect repellent that I used.

Sticker reads:

"Wirkstoff basierend auf Zitronen-eucaluptusöl"

"Active ingredient based on lemon-eucalyptus oil"

When the insect repellent hits the fly, it slowed down and stopped flying, but it's still moving slowly on the window, so I applied the insect repellent again.
Eventually, the fly completely stopped moving, so I assume it's dead. Does the insect repellent actually killed the fly, or just stunned it?


texts: What happens when you run house electricity through salt water?

texts:
What happens when you run house electricity (120VAC) through salt water? (with standard copper wires!)

Well, in https://youtu.be/dcrY59nGxBg , an interesting experiment was conducted to find out!

At the end of the video, however, I noticed the salt water became rather dark and murky, and I'm wondering what happened inside.

Did the copper wires just corrode into some  kind of precipitate?
$$\ce{Cu(s) + H2O(\ell) -> CuO(s) + H2(g)}$$
$$\ce{Cu(s) + 2H2O(\ell) -> Cu(OH)2(s) + H2(g)}$$

Was there chlorine gas even created too?
$$\ce{2H+(aq) + 2Cl^{-}(aq) -> H2(g) + Cl2(g)}$$


texts: How to calculate the quantum yield of a photochemical process?

texts:
I have that $\pu{100 ml}$ of an aqueous solution containing $\pu{1.0 mM}$  $\ce{H2O2}$, $\pu{100 mM}$ $\ce{CH3OH}$ and $\pu{200 mM}$ DMSO are exposed to monochromatic light with a wavelength of $300$ nm. The incident light intensity is $\pu{2mW/cm2}$ and the exposed area is $\pu{4cm2}$. The absorbance of the solution at $300$ nm (which depends only on  $\ce{H2O2}$) was measured to be $0.25$. Only the homolysis of $\ce{H2O2}$ to two hydroxyl radicals needs to be taken into consideration. The hydroxyl radicals formed react with  $\ce{CH3OH}$ at a rate constant of $\pu{1.0E8M^{-1}s^{-1}}$ and with DMSO at a rate constant of $\pu{2.0E9M^{-1}s^{-1}}$. The product of the reaction with $\ce{CH3OH}$ is formaldehyde ($\ce{CH2O}$). The concentration of formaldehyde as a function of reaction time was measured and is given below. Based on the data below, determine the quantum yield for photoinduced homolysis of $\ce{H2O2}$.
$$
\begin{array}{rl}
\hline
\textrm{time}/\pu{h} & [\ce{CH2O}]/\pu{M} \\
\hline
0 & 0 \\
1 & \pu{7.7E-7} \\
2 & \pu{1.5E-6} \\
3 & \pu{2.3E-6} \\
4 & \pu{3.1E-6} \\
5 & \pu{3.8E-6} \\
\hline
\end{array}
$$

I hope this isn't closed off as "off-topic" since it is quite a long question but I genuinely don't know where to start on this. I feel that there is so much information and I can't quite determine what is useful and what has just been added to confuse us.
I wanted to start by writing all the reactions and then use the steady-state assumption to determine the rate equation for $\ce{CH2O}$ but even there I got stuck. From what I have understood two of the reactions are:
$$\ce{H2O2 -> 2OH-}$$
$$\ce{2OH- + CH3OH -> CH2O + 2 H2O}$$
But I don't know how the third reaction with DMSO will look like and can't seem to find anything online. I don't know if the way I am trying to solve this problem is the correct way since I don't really know if I am supposed to solve for  $\ce{CH2O}$ and then plot it to get something from the plot so I would truly appreciate if someone could push me in the right direction or link helpful examples or other useful information that might help me solve this. Thank you!
EDIT
With your help I have tried to being answering the problem but I come across some things that I don't know how to tackle. I began with calculating that the incident light intensity should be $2$ mW/cm$^2$ * $4$cm$^2$ = $8$ mW. By using Lambert-Beers law I calculated the intensity of the outgoing light as:
$$log\frac{I_0}{I} = A$$
$$I = \frac{I_0}{10^A} = \frac{8mW}{10^{0.25}} = 4.49 = 4.5 mW$$
Then the amount of absorbed light is: ΔI = I$_0$ - I = $8 - 4.5 = 3.5 mW$
So from this I can now calculate the denominator of the quantum yield fraction (I call it b for amount of absorbed photons) from the equation:
$$b = \frac{absorbed light}{energy per mol photons} = \frac{ΔIλ}{hcN_A} = \frac{3.5*10^{-3}Js^{-1}* 300 * 10^{-9}m}{6.625*10^{-34}Js^{-1}*3*10^8ms^{-1}*6.02*10^{23}mol}$$
$$= 8.78*10^{-9} smol^{-1}$$
I don't think this is the correct answer since the units don't add up. Should I maybe take the intensity times the number of hours ($5$h) to get the intensity only in Joules?
Then if I write out the rate equations:
$$\frac{d[CH_2O]}{dt}=k_2[OH^*]^2[CH_3OH]$$
$$\frac{d[OH^*]}{dt}=k_1[H_2O_2]-k_2[OH^*]^2[CH_3OH] → [OH^*]^2 = \frac{k_1[H_2O_2]}{k_2[CH_3OH]}$$
which then gives:
$$\frac{d[CH_2O]}{dt}=k_1[H_2O_2]$$
I don't really understand what use I have of this in order to calculate the number of molecules of the reactant which is used..


texts: Unknown anion (one carbon and two nitrogen atoms, charge 2−)

texts:
What's the name of this ion: $\ce{CN2^2-}$? I think that it has this structure:
$\ce{{}^{-}N=C=N-}$.


texts: Why do two atomic orbitals form two molecular orbitals?

texts:
According to molecular orbital theory, two atomic orbitals form two molecular orbitals analogous to waves combining constructively or destructively but how can a wave combine destructively and constructively at the same time to produce two molecular orbitals?

Why don't two atomic orbitals combine to form a molecular orbital that can be BMO or ABMO?


texts:
I'm not a chemist so excuse me if my question will bite your eye or ear.
A resin 3d printing uses polymers that cure under exposure to UV light. There is a special sort of 3d printing resins made for casting metals. Basically these resins produce smaller amount of ash during casting. I'm looking for a way to clean-out a metallic part made from aluminium (or other metals in a list below) from 3d printing-resin-ash that occurs in place of contact with metal.
I'm unable to apply mechanical force to clean out the model due to it's geometry so naturally I would like dissolve the remnants of polymer (supposedly carbon) with some sort of acid or anything else that would eat-out ash while preserving metal as much as feasible.
The list of metals can be any of the following:
Aluminum, chrome, copper, nickel, steel, silver (ordered from most preferable to least preferable)
Is there a chemical compound capable of achieving the goal.
Thank you in advance!


texts: Why don't electrons simply stick to the nucleus on account of being *oppositely* charged, instead of moving around it?

texts:
Why don't electrons stick to the nucleus on account of being oppositely charged charged (the nucleus being positively charged)? But contrary to my intuition, electrons seem to follow a whole bunch of wacky paths (orbitals) around the nucleus (as demarcated by orbital wave-functions). Why is this?

Do note:

I'm not asking "What keeps the electron in orbit". All I want to know, is why electrons don't simply find themselves attached to the nucleus, and why do they even bother moving around the nucleus (in orbitals) at all? My textbooks, unfortunately, make no reference to this issue...they wholeheartedly adopt the "current" QM model of the (hydrogen) atom.


texts:
$$C_x H_y O_z$$

1.What are the units of x,y,z.I've read that they're termed as 'stoichiometric coefficients'.

2.What is the unit of mass proportion of carbon(c) in the fuel?

$$c=\frac{M_{carbon}}{M_{fuel}} .x$$


texts: Why do impacting electrons have a low probability of causing ionization?

texts:
In a section on ionization efficiency and ionization cross section, my mass spectrometry textbook, Mass Spectrometry by Jürgen Gross [1, pp. 38–39], says the following:

  The ionization energy represents the absolute minimum energy required for ionization of the neutral concerned. This means in turn that in order to effect ionization, the impacting electrons need to carry at least this amount of energy. If this energy were then to be quantitatively transferred during the collision, ionization would take place. Obviously, such an event is of rather low probability and therefore, the ionization efficiency is close to zero with electrons carrying just the IE of the pertinent neutral. However, a slight increase in electron energy brings about a steady increase in ionization efficiency.

Why is such an event of "rather low probability"? It seems to me that if the impacting electrons are carrying at least the necessary ionization energy, as the author suggests, then shouldn't ionization occur (be a certainty or, at least, a high probability event)?

I would greatly appreciate it if people could please take the time to clarify this.

References

Gross, J. H. Mass Spectrometry: A Textbook, 3rd ed.; Springer International Publishing: Cham, Switzerland, 2017. ISBN 978-3-319-54397-0.