texts: Is LiF a weak electrolyte in acetic acid?

texts:
The vapor pressure of acetic acid is 0.033 atm at 25°C. If 5.00g of $\ce{LiF}$ is added to 100g of acetic acid, what would be the vapor pressure of the solution at 25°C?

The lowering in vapor pressure (VP) can be calculated with this equation:

${∆P = X_{solute} * P°_{solvent} * i}$
${∆P}$ is the change (lowering) in VP.
${X_{solute}}$ is the mole fraction of the solute.
${P°_{solvent}}$ is the VP of the pure solvent.
${i}$ is the van't Hoff factor of the solute.

What is the "correct" van't Hoff for this problem, from the perspective of a general chemistry student? I know that $\ce{LiF}$ is not very soluble in water, and I know there are papers on lithium fluoride and acetic acid, but that's all beyond the scope of a general chemistry class.
Therefore, I think it's 2, because $\ce{LiF}$ is expected to be a strong electrolyte. It's ionic, and the solvent is similarly polar (acetic acid has hydrogen bonds). The solvent even resembles water in that both have hydrogen-bonding. So I would expect $\ce{LiF}$ to dissolve fully in acetic acid.
Remember, this is a general chemistry class, and the students aren't expected to know much beyond "like dissolves like." $\ce{LiF}$is polar, and so is acetic acid. So to them, $\ce{LiF}$ should dissolve in acetic acid.
Problem is that I'm in trouble with my supervisor since I told someone that i = 2. My supervisor is telling me that the van't Hoff factor should be 1. I looked over his work to see if he accounted for the dissolving of $\ce{LiF}$when calculating the mole fraction of the solute but he didn't - he just found the mole fraction of $\ce{LiF}$, not the combined mole fractions of $\ce{Li+}$ and $\ce{F-}$.
So, what's the deal with this problem? Is there some weird exception I'm not aware of regarding $\ce{LiF}$ and acetic acid? The van't Hoff factor should be 2, correct?


texts: Is this reaction of 4-chloro-1,1-dimethylcyclohexane SN1, SN2, E1, or E2?

texts:
In the following question, which I tried to solve, I became confused by which way I should proceed.
Here is my thought process:

SN1: If Cl detaches and forms a secondary carbocation, then there's no nearby groups to stabilize it or make a shift to turn it into a tertiary cation.
SN2: I can't make out how exactly SN2 would occur
E1: I can't make out how exactly E1 would occur
E2: There's no stereospecific data given in the question whether the methyl group and the hydrogen lie in one plane or not, so I couldn't make out a way to do anti-elimination.

The Answer is given : E1

so @benzene , This is the E1 product as per the mechanism , Am i right ?


texts:
In Concise Inorganic Chemistry by J.D.Lee (Adapted by Sudarsan Guha, Fourth Edition), on page 82, under section 3.8 - Types of Covalent Bonds (Sigma and Pi Bonds) it is given (for Sulphur dioxide molecule):

  The $\pi$ bonds do not alter the shape, but merely shorten the bond lengths. The bond angle is reduced from ideal $120°$ to $119°30'$ because of the repulsion by the lone pair of electrons. Problems arise when we examine exactly which atomic orbitals are involved in $\pi$ overlap. If the $\sigma$ bonding occurs in the $xy$ plane then $\pi$ overlap can occur between the $3p_z$ orbital on sulphur and the $2p_z$ orbital on one oxygen atom to give one $\pi$ bond. The second $\pi$ bond involves a d orbital. Though the $3d_{z^2}$ orbital on sulphur is in the correct orientation for $\pi$ overlap with the $2p_z$ orbital on the other oxygen atom the symmetry of the $3d_{z^2}$ orbital is wrong (both lobes have a + sign); whilst for a p orbital one lobe is + and the other -. Thus overlap of these orbital does not result in bonding. The $3d_{xy}$ orbital in sulphur is in the correct orientation and has the correct symmetry to overlap with the $2p_z$ orbital on the second oxygen atom, and could give the second $\pi$ bond.

I am unable to understand the part which has been typed in boldface.

We know $d_{xy}$ orbital lies in the $xy$ plane. We also know that $p_z$ orbital lies along the z-axis. Then how can these two orbital participate in $\pi$ bonding?

The following image is my attempt to show bonding in sulphur dioxide. The oxygen atom under consideration is the second one marked with a $\bigstar$.

In the following image the lone pair present in the s orbital is not shown for the sake of simplicity. There will be some distortion in the bonds and sulphur dioxide would be bent and will not be linear. But here it is shown to be linear.

Clearly, for the second oxygen atom, the overlapping of atomic orbitals is not possible due to out of phase approach. I feel the formation of $\pi$ bond between the sulphur atom and the second oxygen atom must take place between $2p_x$ orbital of the second oxygen atom and $3d_{xy}$ orbital of the sulphur atom. Kindly tell whether I am correct or not.

Kindly clarify my doubt.


texts: Why the formation of a fog is observed when triethylamine is added?

texts:
In the procedure for the synthesis of N-anisoyl-2-pyrrolidinone that was given to me, it is written that when triethylamine is added, a "fog" is observed inside the flask.

Triethylamine is added to neutralize the hydrochloric acid that is generated during the reaction, forming triethylammonium chloride.
I searched for similar procedures involving an acyl chloride and an amine, but the formation of a "fog" is never mentioned.
A quick search on the internet gave me no clue.
In my experience I have never witnessed the formation of a "fog" with this kind of reactions.
Since I cannot enter the lab due to the COVID-19 restrictions, I cannot perform the reaction now, can someone help me to understand if and possibly why in this case a "fog" is formed?


texts: Why does the addition of PCl5 increase the rate of dissociation of PCl5?

texts:
$\ce{PCl5 <=> PCl3 +Cl2} $

It's stated in my book that addition of $\ce{PCl5}$  to the equilibrium mixture increases the rate of forward reaction but no reason is mentioned for it.

However, before this the author derived $K_c = \dfrac{x^2}{(1-x)V}$ (using law of mass action at equilibrium ) where V is the volume of the container and $x$ is the number of $\ce{PCl5}$ molecules dissociated from $a$ number of moles initially.
I couldn't relate the "rate of forward reaction" statement to this equation while earlier in case of the reaction:

$\ce{H2 + I2 <=> HI}$

I was able to relate the equation I obtained through law of mass action with the effect of concentration on rate of forward or backward reaction.

Could someone please explain why addition of $\ce{PCl5}$ to the equilibrium mixture increases the rate of forward reaction?


texts: pH of sodium metasilicate anhydrous vs pentahydrate when dissolved in water

texts:
I'm not a chemist and don't remember much chemistry from school, so please forgive a naive question (I've read the Wikipedia article on sodium silicate though).

I'm researching this topic to make a positive photo resist developer for making PCBs.

Will dissolving $\ce{Na2SiO3}$ (the anhydrous form) in water produce essentially the same solution as dissolving $\ce{Na2SiO3*5H2O}$ but in different concentration or are these intrinsically different?
Will $\ce{Na2SiO3}$, if left in contact with open air, eventually hydrate to $\ce{Na2SiO3*5H2O}$?
Also, the Wikipedia article talks about the $\ce{SiO2:Na2O}$ ratio affecting the pH of the water solution. Is the information about this ratio already present in the chemical formula so if I buy $\ce{Na2SiO3*5H2O}$ it is always the same ratio or is this a different parameter that is specified in addition to the chemical formula? (I understand that different concentrations of the solution will produce different pH, but consider equal concentrations)

I believe I need the developer to be an alkaline solution so I need to understand what will affect the pH when dissolving sodium metasilicate in water (e.g. if I need $\ce{Na2SiO3}$ or $\ce{Na2SiO3*5H2O}$, if I need to consider other specifications besides the chemical formula, if I need to consider the shelf life of the chemical if it changes with time e.g. gets hydrated from $\ce{Na2SiO3*5H2O}$ into $\ce{Na2SiO3*9H2O}$).
 Searching electronics forums on the internet I haven't found a clear answer. For some people using this sodium metasilicate as a developer works for some it doesn't develop at all, some add $\ce{NaOH}$ to it but there are places that advertise their sodium metasilicate developer as sodium hydroxide free.


texts: How are N95 masks different from dust masks?

texts: There is a fire raging through my hometown right now. People in the area are advised to be wearing N95 masks to filter out smoke and particulates; and there is misinformation being spread that these masks actually don't work for this purpose. What's the science behind the N95 filter? The Wikipedia page didn't really elaborate.


texts: Which of these carbocations are more stable?

texts:
The line of text that follows this figure in my work-book reads:

  Cation (A) is more stable than cation (B), since the former is resonance stabilized but the latter isn't (due to steric effects).

Don't both carbocations show resonance stabilization? More importantly, isn't cation (B) more stable than (A)?

Based on what I've learnt, the following should occur:

1) Cation (A)

The sp2 carbon (in the isopropyl group) acts as a -M group and causes the shift of a pair of π electrons from the benzene ring towards the $\ce{C-C^{+}}$ bond, thereby creating a double bond in its place. So the resulting structure should look like,

The mesomeric effect would also ensure that the positive charge "travels" across the ring, and decreases the electron density at ortho- and para- positions.
The delocalization of the positive charge across the benzene ring should confer some degree of stability to the carbocation.

2) Cation (B)

Once again, a pair of π electrons from the benzene ring would shift towards the $\mathrm{C-C^{+}}$ bond, leaving behind this:

And again, the mesomeric effect would delocalize the positive charge over the benzene ring and create electron deficient centers at the ortho- and para- positions.

However, the presence of two isopropyl groups at ortho- positions (with respect to the orignal charge-carrying isopropyl group) will result in the "supression" of the positive charge via inductive and esomeric effects, hence, conferring additional stability to this molecule.

Hence, cation (B) should be more stable than (A).

Yet, my conclusion is different from that provided by the book. Well, I guess that the presence of three adjacent isopropyl groups (in cation-B) does seem sterically unfavorable, but how would that prevent resonance effects in the molecule (as the book seems to imply)?

So, is my conclusion correct? Have I arrived at it correctly? If the book's right, then why is it right?


texts: How to calculate the number of water molecules of a hydrate based on mass loss upon heating?

texts:
A $\pu{4.250 g}$ sample of $\ce{Na2SO4.nH2O}$ the sample loses $\pu{2.388 g}$ upon heating. What is $n$ for this hydrate?

Do I first determine the mass of the water than the amount of substance of the sample and than the whole number ratio?


texts: Since all objects on earth are composed of elements, how can I identify the fundamental make-up of objects such as trees, glass, bricks, wood, plastic, shoes, and other entitys?


texts: Deciding which group twists out of the plane when ortho effect takes place

texts:
I'm going to take a few stills from 3D conformers of the following compounds available on PubChem in which ortho effect is applicable to show what I'm referring to.
2-Nitrobenzoic acid:

N,N-Dimethyl-2-nitroaniline:

2'-Aminoacetophenone:

In the compounds above due to steric repulsions between the groups present, one group needs to be twisted out of the plane of the benzene ring. My question is, how do we theoretically explain which group shifts out of the plane, and which doesn't?
To my understanding, two things would effect this; one would be the extra stabilisation/destabilisation of a group due to not being in resonance any longer once it moves out of the plane of the benzene ring, and the second would be the "bulkiness" of the group itself, which would energetically be measured as the group's A-Value.
For the above three compounds in the same order, from the perspective of A-Values (the text in brackets mentions what actually happens):

($\ce{COOH}$ twists out of the plane) The A-Values are $\ce{COOH} = 1.2, \ce{NO2} = 1.0$, so it makes sense for $\ce{COOH}$ to stay in the plane of the ring.

($\ce{NMe2}$ twists out of the plane) A-Values $\ce{NMe2} = 2.1, \ce{NO2} = 1.0$ so it makes sense for $\ce{NMe2}$ to stay in the plane.

($\ce{COMe}$ slightly twists out of the plane) A-Values $\ce{NH2} = 1.6, \ce{COMe} = 1.17$ so it makes sense for $\ce{NH2}$ to stay in the plane.

(data from here and here)
I understand that A-Values are not the only thing which we need to consider, since resonance plays a part (maybe even other stuff?), but I haven't been able to figure out convincing reasoning as to why in the above examples the group which shifts out of the plane does so. Does the volume occupied by the groups play a crucial part as well, since so far I am yet to come across a compound in which the smaller group (by volume) shifts out of the plane? Are A-Values even relevant to such a scenario?
(I'm looking for a list of factors which need to be considered, whether this can even be explained/predicted theoretically, and/or explanations for the any of the above compounds. I understand that this could be slightly lengthy, so I'd be more than happy for answers which address any one of these, but I feel talking about the three compounds was necessary to explain the question properly, and hence the somewhat broad question.)


texts: Soap and rain water, why does it not rinse off?

texts:
I am in Papua New Guinea at the moment, where rain water harvesting is the most common way of getting water.
When washing hands, the soap feels hard to rinse off, and my skin feels "greasy".

I read around a bit here and here and I think I understand what is said: essentially, sodium stearate in the soap separates into sodium and stearate ions, which then precipitate with other ions (like Calcium, into calcium stearate) and get rinsed away. But in very soft water, there are sodium ions rather than calcium ones, so this reaction is slowed down a lot, resulting in the greasy feeling.
As it turns out, I have access to hard ground water at the same time, and the difference is very obvious: with hard water, soap is rinsed off instantly.

My question now: I assume rain water has in fact almost no ions in it (I'm thinking Sodium ions mostly), and I would therefore assume that the Sodium stearate dissolves very easily, but has no replacement ion to precipitate with, therefore sticks to the skin.

Is this the right explanation or are there other factors at play in the explanation about that greasy feeling?


texts: How do I get irreducible representations?

texts:
I'm currently trying to do a problem where it asks me to "show that the irreducible representations spanned by the atomic x-, y-, and z- coordinates is independent of the choice of local coordinate system. Use the diagrams below."

I know the general process is to determine the irreps for the separate coordinates. So, when I attempted to do the first one, by doing the symmetry operations to the x vectors from the D3h character table. However, it did not work as well. So now I don't know where to go with it. Please help and thank you.


texts:
I was supposed to identify this compound by knowing its molecular formula and the following spectra:

$1\mathrm{H}\ (\mathrm{s},\ 9.67\,\mathrm{ppm})\\
1\mathrm{H}\ (\mathrm{quartet},\ 7.73\,\mathrm{ppm})\\
1\mathrm{H}\ (\mathrm{quartet},\ 7.30\,\mathrm{ppm})\\
1\mathrm{H}\ (\mathrm{quartet},\ 6.63\,\mathrm{ppm})$

My question is: how come we get quartets for the protons on the furan ring? I can see it getting doublets and triplets, but it seems impossible for them to couple with the aldehyde proton (which, in itself, doesn't couple with any of them).


texts: Determining the exact charge of ions that will be formed by an atom using the periodic table

texts:
I don't know how to obtain the "exact charge of the ions" that will be formed by each atom mentioned. I also have to figure out whether they are positive or negative.

Hydrogen, for example, can form the ion:

$$\ce{H -> H+ + e-}$$

Now if I were to try to get the exact charge for say, boron using only the periodic table, how would I do so?


texts: Why 2p Orbitals overlap more effectively than 3p orbitals?

texts: So, for example, looking at HF and HCl, we see that the 1s orbital of the H overlap with the 2p orbital of F more effectively. Which argument can i use to explain that? Density?


texts: Nomenclature of common naming of alkynes vs alkenes; both -ene?

texts: Is there a difference between common naming of alkenes vs alkynes? Why is Ethylene the common name for an alkene and acetylene for an alkyne? Isn’t acet- the common form of naming ethyl groups anyway so why is ethyl used in a common name?


texts: Different values of concentration of product at equilibrium

texts:
$\pu{60g}$ of acetic acid and $\pu{46g}$ of ethyl alcohol are mixed with each other at a constant temperature and allowed to attain equilibrium. At equilibrium $\pu{58.2g}$ of ethylacetate and $\pu{12g}$ of water were present: find the concentration equilibrium constant ($K_\mathrm{c}$)

Here is my solution:

The correct answer is 4 but I'm getting 3.7 something. When I calculate x with the help of made of water it is slightly different than when I do it with the mass of ester. Shouldn't they both give the same answer? If not, which substance should I use?


texts:
Say I have a soft, possibly porous object. I want to coat it with a material,

Resistant to boiling water and some scraping
Not hazardous, at least after the coating
Largely transparent

The idea is to take, say, a fruit with the insides removed and to make a cup or a vase out of it.

Is there something I could buy or make at home for this?


texts: An electric potential is generated when a liquid moves with respect to a solid (streaming potential). Is the reverse true?

texts:
Streaming potential is an electrochemical phenomenon that a that relates
electric currents with the relative movement of solid and liquid phases in contact with
each other.

So when a liquid moves past a solid a potential is generated. The equations for the values of the potential and current generated can be found in this Wikipedia article. My question is, is the reverse true? If I applied an electrical potential difference (instead of applying a pressure difference), would a pressure difference be generated?


texts: Best way to remove Aluminium from "silvered" glass?

texts:
Requirement is simple(!) - I have 30mm silvered glass balls that are originally Christmas tree decoration that I want to use in a very unconventional manner in a physics experiment. As far as I can tell the Aluminium is external. The balls are exceptionally delicate and the glass probably somewhat stressed i.e. they break easily if scratched.

So, would dilute NaOH be suitable or is there a better solution?
Another requirement is that ideally the treatment does not raise the surface energy of the glass


texts:
In the following halogenation reaction:

  At which position will halogenation take place?

It is obvious that the halogenation will take place at a 3° Carbon atom (the rates of halogenation for 3°,2°,1° atoms follow the ratio 1600:82:1 or thereabouts). The question is which 3° atom? I labeled the atoms as shown:

I believe that halogenation will take place at A because the cyclopropyl ring can stabilize the free radical formed at A better than the 6-membered ring. A similar question that deals with carbocations is here, which shows the stability of the cyclopropylmethyl carbocation. Can a similar logic also be applied to free radicals? Please confirm.


texts: Does UV water purification cause cancer?

texts:
I found out that a relative is using a machine that performs UV water purification at home (for drinking).

There seems to be a distinct difference from the water that is not purified by it.

Is it possible that this use of UV radiation may lead to cancer in humans?


texts:
If I have aniline in acid and fuming $\ce{SO3}$, will it reversibly sufonate? I am worried that the nitrogen will be protonated and reduce the nucleophilicity of benzene ring to the point where sulfonation just isn't possible and instead you just get a salt? Or is it possible that you only get mono-sulfonation?

Here is my reaction scheme:


texts: Inflection point, slope, and equivalence point in a titration

texts:
My textbook, Harris 7th Edition Quantitative Chemical Analysis, says:

  In titrations involving 1:1 stoichiometry of reactants, the equivalence point is the steepest point of the titration curve. This is true of acid-base, complexometric, and redox titrations as well.

My question is, does this apply to all acid-base titrations (strong-strong and weak-strong)? My intuition seems to say that it only applies to strong-strong, but I may be incorrect.


texts: Validity of rationale for balancing chemical equations

texts:
The reason given for balancing chemical equations is the law of conservation of mass. They say that we balance equations with keeping in mind that atoms of every element included in the reaction must be equal on both sides of equations. And they just add some coefficients for this purpose.

But I apprehend why is the amount of substance not brought under consideration while doing this?

For example when we write,

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

That is; until we don't know how much of $\ce{H2}$ and $\ce{O2}$ was included in the reaction, how can start to balance it? How can we decide that atoms are not equal on both sides?  However, the molecular formulas given above are only representing the substances.


texts: Specific Heat Ratio for a perfect gas mixture

texts:
I am reading Rocket Propulsion Elements by George P. Sutton & Oscar Biblarz, 9th Edition. In the fifth chapter, I was introduce to the specific heat ratio k for the perfect gas mixture, Eq. 5-7. Without explanation the Equation was stated as follows:
(5-7) $k_{\text{mix}} = \frac{(C_{p})_{\text{mix}}}{(C_{p})_{\text{mix}}-R'}$
From Thermodynamics I know,
(a) $k_{j} = \frac{(C_{p})_{\text{j}}}{(C_{v})_{\text{j}}}$ ; Species specific heat ratio
(b) $R_{j} = \frac{R'}{\mathfrak{M}_{j}}; $ Species Gas constant equal to Univ. Gas constant over Molar Mass of species $\text{&}$
(c) $R_{j} = (C_{p})_{\text{j}} - (C_{v})_{\text{j}}$ ;Mayer's Formula for species
So, it seems to me that Eq. (5-7) should instead include the mixture gas constant $R_{\text{mix}}$ in the place of the Universal gas constant, $R'$.
I tried to derive Eq. (5-7) from Eqs. a, b, and c without success. Can someone clarify the derivation of Eq. (5-7) to me?


texts: How is the atomic number of a beta particle zero?

texts: In my textbook, $\ce{β-}$ particle is denoted as $_{-1}e^0$. This means that the atomic number of $\ce{β-}$ is $\ce{-1}$. But that doesn't make any sense. Also, how is the mass number of $\ce{β-}$ zero? I mean it must have some mass right? How can it be massless?


texts: How to form an acetal from an enol ether?

texts: I am having trouble understanding how the protecting group (ethylene glycol) is applied to the alkene next to the ether of highlighted step above. I thought maybe TsOH protonates the alkene as seen in the mechanism below so that it forms a carbonyl but it doesn’t seem right as a carbocation should be found on the tertiary carbon. I have no idea if I am going about this correctly, any suggestions?


texts: What is the difference between SBA-15 and MCM-41?

texts: I'm trying to understand the difference between these two mesoporous materials.  They both have the same polys-siloxane backbone and surface silanol groups, the same hexagonal pores, and yet I don't understand why they are different materials.


texts:
I recently tried to make a cheap solid fuel out of sugar. First I attempted burning the sugar cube directly, which did not work well even using a blowtorch. This was expected. Then I attempted to use paper ash, and it could be lit with a lighter. However the flame went out quickly and that would not be usable for anything.

How can I make sugar burn completely? My aim is to have it burn as well as hexamine, although I realize that is probably quite impossible to do at a reasonable cost or else it would already have been done.

One idea I have had is to mix a small amount of oxidizer into the sugar - not enough to make it into a rocket-candy type fuel, but just enough to accelerate combustion. Another idea I have thought of is to mix some charcoal, combustible oil, or wood into the sugar as a secondary fuel. I won't be able to do these experiments for quite some time due to a lack of resources.


texts: Surely, by the same logic, any atom with a moderate electronegativity (carbon, phosphorus, silicon) can form a polarise covalent bond with an atom with a high electronegativity (fluorine, oxygen). Giving that carbon, phosphorus or silicon a partially positive charge (just like hydrogen), allowing it then to form a 'hydrogen bond' with another atom with a high electronegativity (fluorine, oxygen). Is it called a hydrogen bond because it most commonly occurs with hydrogen? Or is it that a hydrogen bond with carbon, phosphorus or silicon is instead called a carbon bond, phosphorus bond and silicon bond? Since you don't need a hydrogen to make an atom high electronegativity partially negatively charge, surely those atoms around atom would be paritally postive to balance the charge?


texts: The concept of normal coordinates of a molecule

texts:
Sometime ago I had posted the What is the origin of "normal" in normal coordinates and normal modes? in math & sci history problems. Nobody was sure for the reason for using the word normal there - it was an interesting discussion though. The concept of normal coordinates is transiently brought in vibrational spectroscopy in undergraduate textbooks but rarely explained in detail. Certainly, the concept is borrowed from mechanics.

How can we explain the concept of normal coordinates? What is the need of a new set of coordinates if x, y, z can show also the displacements of an atom from its mean position? Let us take the example of a non-linear molecule like water.

Edits
More specifically, how would we mathematically define a normal coordinate for the oxygen(s) and hydrogen during a normal mode vibration of water molecule? Or a "normal coordinate" is a global displacement coordinate for the whole molecule for a given normal mode vibration. Water has 3 IR active modes. Do we have only 3 normal coordinates $q's$ for water? Wikipedia shows a simplistic picture of a normal coordinate $q$ as a measure of displacement but from little bit of reading Herzberg's other specific monographs by Wilson, the concept of normal coordinate does not seem that trivial.


texts: Why doesn't the current stop in neon lamps when all the atoms have been ionized?

texts: My personal experience (which could be wrong) tells me neon lamps can theoretically run on forever or at least a very long time. If current is the flow of charge why doesn't it stop once all the atoms have been ionized? Do these atoms they continuously loose and gain electrons? If so why then doesn't the light concentrate to the side of the cathode were all the ions attract to?


texts:
I have studied that the Grignard reagent $\ce{RMgX}$ reacts with $\ce{CO2}$ to form $\ce{RCOOH}$ after acid hydrolysis. But does the same apply for sulfur dioxide?

Grignard reagents are good bases and also good nucleophiles.
So the alkyl anion will attack the electron deficient carbon atom in $\ce{CO2}.$

But in the case of $\ce{SO2}$ the following conditions aren't present.
First of all, sulfur is more electronegative than carbon. Secondly, sulfur has a lone pair of electrons which the carbon lacks. So this should further discourage an attack by the Grignard's alkyl anion.

So, what actually will happen when Grignards are treated with $\ce{SO2}?$


texts: What are the most important resonance structures of 5-aminocycloheaxa-2,4-dienone?

texts:
Show, by means of curly arrows and electron shifts, the resonance contributors to the structure given below. Suggest which one would not be a major contributor and state why.

This is a question from my exam. I do not understand where I went wrong. My effort is placed at the end (along with a request).

Also, my TA removed 1 point out of 7 for a reason. Can anyone decipher for what? There's the writing in red but it is illegible to me. I don't understand to what he refers by 8 and 6 t or +, or whatever he wrote.


texts: Why does cobalt have no negative charge?

texts:
I would like to know why cobalt cannot have a negative charge (or at least why a negative charge for cobalt isn't typical). I am not sure where I have gone wrong in my reasoning.

The electronic configuration for cobalt is:
$\ce{Co}$: $[\ce{Ar}] 4s^2 3d^7$

Clearly, you could give cobalt a $+2$ charge in order to get a more stable ion as follows

$\ce{Co^{2+}}$: $[\ce{Ar}] 3d^7$

And from there, you could go further and remove $2$ more electrons from the $d$-orbital to become even more stable like this:

$\ce{Co^{4+}}$: $[\ce{Ar}] 3d^5$

If this logic is correct, then could I apply this same thinking but for adding electrons? Such that

$\ce{Co}$: $[\ce{Ar}] 4s^2 3d^7\to$ $\ce{Co^{3-}}$: $[\ce{Ar}] 4s^2 3d^{10}$

Since the $d$-orbital has been filled, the atom should have become more stable. Is it true?

Thus, am I able to argue that Cobalt has $3$ main ion charges: $+2, +4, -3$?


texts: How to identify ions by their quantum number?

texts:
If the quantum numbers of an ion are given, how can we identify this ion by its quantum numbers?

For example :

  n = 3; $l$ = 2; $m_l$ = 0; m$_s$ = + ½

What I have so far: $n$ is 3 and $l$ is 2 which corresponds to $d$, so the last shell is $3d1$, therefore we have 21 $e^-$ and the answer will be $\ce{Sc}$ ion (from the periodic table) and the answer I got is $\ce{Mn^{2+}}$.   Is this the correct approach?


texts: Why is magnesium sulfate more soluble in water than that of strontium and calcium sulfates?

texts:
Magnesium sulfate is soluble in water. Its solubility is $\pu{26.9 g}/\pu{100 mL}$ at $\pu{0 ^\circ C}$ $(\pu{35.1 g}/\pu{100 mL}$ at $\pu{20 ^\circ C})$.[1]
However, both calcium sulfate $(\pu{0.21 g}/\pu{100 mL}$ at $\pu{20 ^\circ C})$ and strontium sulfate $(\pu{0.0135 g}/\pu{100 mL}$ at $\pu{25 ^\circ C})$ are much less soluble in water. [2] and [3]
Moreover, magnesium hydroxide is less soluble than calcium hydroxide and strontium hydroxide.
Since the magnesium ion has a smaller radius, shouldn't magnesium sulfate be less soluble than calcium sulfate and strontium sulfate?


texts: Help finding a thixotropic suspension with specific properties for 3d printing

texts:
I currently doing research on 3d printing on circuit boards. The technique we are using is to put a conductive material, I.e ceramics/metal in a gel/polymer, to print the suspension and then when is complete to sinter away the gel/polymer. The problem I am having is the suspension needs to be thixotropic. Furthermore it must have a high viscosity i.e 500 cpa under low shear and to quickly drop to low viscosity as the shear increases

So far the closest thing I have been able to find is in this paper but if you look at the graphs none of them have a high enough viscosity and more importantly the drop to low viscosity under increasing shear is too shallow.

I have tried to use models like the ones in this paper but I am finding it quite difficult.

Does anyone have any suggestions to find more materials like the one I require? Thanks


texts: How to define the atom numbers in unsaturated hydrocarbons correctly according to IUPAC?

texts:
I would like to address the compound below.

This compound on elaborate elongation would result in this structure.

But is the below given numbering correct? I am just wondering that what if the same compound is given numbering, starting from that carbon which is assigned 7th number in the first elaborate diagram (second diagram), by doing so, triple bonded substituent will also get the least number, as shown in the below given diagram.

I have a similar problem with this compound:

What if you just reverse the numbering? By reversal I mean, the carbon assigned 1st number should be given the last number, am I violating any rule? If I do that, by numbering the compound in reverse order, we get least number for the methyl chain substituent, so is it necessary that methyl group substituted in the side chain should get the highest possible number?

In short, I mean, is the below given numbering valid or not?


texts: Which of these chlorides is more reactive?

texts:
We do learn that for $\mathrm{S_N1}$ reaction the rates are tertiary > secondary > primary > methyl. The reasons mentioned are usually inductive and hyper-conjugative effect.

But which of the effects is more dominant? So, let's take two chlorides, ethyl chloride and isobutyl chloride, which will be more reactive to $\mathrm{S_N1}$? If we refer to inductive effect, then isobutyl chloride should be more reactive. But if we refer to hyper-conjugation, then ethyl chloride should be more reactive.

Which is more reactive actually?

Note: Which carbocation is more stable, the ethyl- or 1-propyl-carbocation? is not the same as this as I am not satisfied with the answer there. That question compares the stability of carbocation while I am comparing the reaction rates which may depend on kinetic factors too. Actual data could be helpful.

Also, the isobutyl cation rearranges to a tertiary cation. Does the stability of rearranged carbocation affect the rate of reactivity?


texts: Why 1 mole of H2 occupied the same volume occupied by 1 mole of O2?

texts:
I'm asking a question about the volume occupied by gasses in standard temperature and pressure.
My textbook said that a mole of any gas occupies $\pu{22.4 L}$ at standard temperature and pressure.
But $\ce{O2}$ is greater than $\ce{H2}$ in size

I asked my teacher why the volume occupied by 1 mole of $\ce{H_2}$ is equal to the volume occupied by $\ce{O_2}$ at standard temperature and pressure, but he seemed to not know the answer, and I remain confused.
Please answer in simple words.


texts: How exactly do you measure the free energy of a reaction?

texts: It is to my understanding that ΔG can be positive or negative given whether the reactant is exothermic or endothermic.  How would you go about measuring the energy (in joules) of a reaction using the heat of the reaction?


texts: Why do copper (II) complexes contain so many valence electrons?

texts:
Consider tetraaminecopper (II) ion. $\ce{[Cu(NH3)4]^2+}$ or $\ce{[Cu(NH3)4(H2O)2]^2+}$.
The copper(II) ion has the electron configuration $\mathrm{[Ar]\ 3d^9}$. How do the 4 electron pairs from the ammonia ligands form the coordination bond with the copper ion, if the 3d subshell is almost entirely occupied?


texts: What is the solvent and what is the solute?

texts:
This question is and I am learning about mixtures, solutions, solutes, solvents, and other terms related to these words.

I know that a solute is the substance being mixed with or dissolved into the solvent.

Substances and mixtures: are these solvents and solutes correct?

coffee with milk - solvent:coffee , solute:milk
salt water - solvent:water , solute:salt
air freshener - solvent:air , solute:scent
brass - solvent:zinc , solute:copper


texts: How to determine whether the enthalpy of solution is positive or negative by calorimetry?

texts:
How can we determine if the enthalpy of solution of a compound is positive or negative?

In order to make a clear idea about what I mean, take the following problem:

A 3.5 g sample of $\ce{NH4NO3}$ was added to 80. mL of water in a coffee cup calorimeter of negligible heat capacity. As a result, the temperature of solution decreased from $21.6 \ ^\circ\text{C}$ to $18.1\ ^\circ\text{C}$. Calculate the enthalpy change of the solution ($\Delta H_{\text{sol}}$ ). (specific heat of the solution = $4.18 \frac{\text{J}}{\text{g}\cdot ^\circ\text{C}}$; density of water $1.00 \frac{\text{g}}{\text{mL}}$)

Answer: $+28 \frac{\text{kJ}}{\text{mol}}$

Why it is positive despite there is a decrease in temperature?


texts: Why do all radioactive decay series terminate at lead?

texts:
Thorium series:

Uranium series:

Actinium series:

Why do all the radioactive decay series terminate at lead isotope? Why not hydrogen?

(All pictures were taken from Wikipedia.)


texts: Effect of pressure on solubility of salts

texts:
The volume of certain saturated solution is greater than the sum of the volumes of the water and salt from which it is made. On increasing pressure solubility of this salt
(a) Increases
(b) Decreases
(c) Remains unaffected
(d) Can't be predicted

The solution says

Density of product < Density of reactant [mass of reactant = mass of product]
So on increasing pressure equilibrium shift toward higher density solid or liquid.

According to Le Chatelier's Principle, shouldn't equilibrium be shifted towards the side of low density when pressure is increased?
Is my interpretation of the Principle wrong or is the solution of the answer wrong?


texts:
this might be a stupid question but I am really confused at the moment. I'm currently preparing for an exam in computational chemistry. In the lecture I noted always down that the exchange term (Pauli-Principle), which arises as part of the two-electron functions is not determined in Hartree-Fock and added to the cusp-problem, when two electrons come close together. Those two then form the correlation energy, which is determined in post-Hartree-Fock methods.

Then in DFT we have several attempts to solve the exchange part, and I took a note back then, that basically in DFT or in the Kohn-Sham approach, as we do not know the DFT-functional, you create something, that looks like a Fock-operator, with the difference, that it also contains the exchange part.

Now I looked at some tasks and one question was why you do not simply take the HF expression for the exchange part and insert it into the DFT equations. I was a bit shocked what this expression might be and it turns out, when I look into other scripts I cannot find any note that in modern HF the exchange part would be neglected in any way.

So for simple HF (not post-HF) calculations, is the exchange term calculated as well and the only thing you miss would the the correlation?


texts: Difference between vapor-phase transport and vapor-phase deposition?

texts:
I am currently studying the textbook Physics of Photonics Devices, Second Edition, by Shun Lien Chuang. In a section discussing The Invention of Semiconductor Lasers, the author says the following:

  At the Solid State Device Research Conference in July 1962, an MIT Lincoln Laboratory group and RCA Laboratories reported extremely high efficiency (85% to 100%) electroluminescence from GaAs diffused junction diodes. Semiconductor lasers were invented during September to October 1962 by four groups within 30 days [9-12] (see the review article by Dupuis in Ref. 13). They were led by Robert N. Hall of General Electric Research Development Center, Schenectady, New York; Nick Holonyak Jr. of General Electric, Syracuse, New York; Marshall I. Nathan of the IBM Research Laboratory, Yorktown Heights, New York; and Robert Rediker
  of the MIT Lincoln Laboratory, Lexington, Massachusetts. Among the four groups, only Holonyak's laser diodes and light-emitting diodes (LEDs) were created from single-crystal GaAs$_{x}$P$_{1 - x}$ alloy material grown by vapor-phase transport and were the only devices emitting in the visible region.

I had already read about vapor-phase deposition in a textbook on MEMS (microelectromechanical systems), but I was not familiar with vapor-phase transport. Reading about these two methods, they sound very similar, and I'm unsure if they're just different names for the same thing, or whether there is some difference between them. I would greatly appreciate it if someone would please take the time to explain the difference between, if any.


texts: contradiction between Gibbs energy variation and redox potential

texts:
Let's consider the following two redox reactions;

$\ce{C_2H_4O_2 + 2\;O_2 -> 2\;HCO_3^- + 2\;H^+}$
$\ce{C_2H_4O_2 + 1.6\;NO_3^- -> 2\;HCO_3^- + 0.8\;N_2 + 0.8\;H_2O + 0.4\;H^+}$

Considering that the standard Gibbs energies of formation of the involved chemical species are the following;

$\ce{C_2H_4O_2}$: -393.8 kJ.mol-1
$\ce{HCO_3^-}$: -586.9 kJ.mol-1
$\ce{NO_3^-}$: -111.3 kJ.mol-1
$\ce{H_2O}$: -237.2 kJ.mol-1
$\ce{O_2$, $N_2$, $H^+}$: 0 kJ.mol-1

Then the standard Gibbs energy variation associated to those reactions are respectively -804.4 kJ.mol-1 for the oxidation of acetic acid by oxygen and -816.0 kJ.mol-1 for the oxidation of acetic acid by nitrate.

It appears that the oxidation by nitrate is more exergonic that the oxidation by oxygen in standard conditions, when computed this way.

However, the redox potential of $\ce{0.25\;O_2 + H^+ + e^- -> 0.5\;H_2O}$ is +0.811 V, while the redox potential of $\ce{1/5\;NO_3^- + 6/5\;H^+ + e^- -> 1/10\;N_2 + 3/5\;H_2O}$ is 0.746 V. I haven't found any data for the redox potential of acetic acid, however the redox potential of its electron acceptors indicates that an electron transfer from acetic acid to oxygen should imply a larger Gibbs energy variation than an electron transfer from acetic acid to nitrate (according to the $\Delta G = nFE$ formula), which contradicts what has been previously computed from Gibbs energies of formation.

I am new to electrochemistry, so what did I misunderstand here?


texts: It is a common observation that a concentrated solution of hydrochloric acid kept in the lab fumes. What is the chemistry behind this phenomenon? Does $\ce{HCl}$ somehow react with the moisture in the air due to its hygroscopic nature?


texts: Which sodium citrate is used in silver nanoparticles production?

texts:
In my studies, I have a group project to realise: to make some $\ce{Ag}$ nanoparticles using Turkevich method (boiling $\ce{AgNO3}$ with sodium citrate in water). In most of articles authors write about using sodium citrate solution, but when I searched for this compound on Sigma-Aldrich, they offer me a wide range of compounds named "sodium citrate". Mono-, di-, tri- sodium citrate.

Searching for a more specific description, I found this article:

http://www.sciencedirect.com/science/article/pii/S1878535214003645

Here they wrote citrate's formula. It is tri-sodium citrate. But Sigma-Aldrich offers it in hydrated versions. Which version should I use? Is hydration even relevant when I'm going to boil it in water?


texts: Why does CH3CH(OH)CH2CH3 give iodoform test?

texts:
The iodoform test is given by compounds containing $\ce{-(C=O)CH3}$ group or compounds which can be oxidized to such.
$$\ce{ CH3CH(OH)CH2CH3}$$

Is a 2 degree alchohol and even though it were to be oxidized it would not contain a $\ce{-(C=O)CH3}$ group but according to a question asked by JEE in 1997 it as a matter of fact does give the test.

HOW?


texts: What apparatus is needed to get a balloon full of anhydrous carbon dioxide from solid carbon dioxide?

texts: I'm currently planning a research project (new to this) and we need to bubble CO2 through our reaction mixture, however we are not able to use compressed gas so have been advised to pass CO2 from dry ice over a drying agent and syphon it into a balloon. Is there any literature on this procedure, any help much appreciated.


texts: Overall enthalpy balance on a mixing process

texts:
Let's say I have a mixing process involving $\ce{A}$ and $\ce{B}$ at temperatures $T_\ce{A}$ and $T_\ce{B}$, respectively. The $\ce{AB}$ mix is at temperature $T_p$. Our $ΔH_\mathrm{mix}$ is defined at $\pu{25 °C}$ (i.e., our reactants/products are not at the reference temperature) and we know its value. What would be the overall balance?

It is my understanding that we would have 3 steps:

Use the amounts and heat capacities of $\ce{A}$ and $\ce{B}$ and find $ΔH$ (open system) from their specified temperatures to the reference temperature $\pu{25 °C}$. This is $ΔH_1.$
Use the amount and heat capacity of $\ce{AB}$ mix to find $ΔH$ from the reference temperature to $T_p$. This is $ΔH_2.$
Finally, $ΔH = ΔH_2 + ΔH_\mathrm{mix} + ΔH_1.$

That is to say, the overall $ΔH$ is the sum of all the steps required to get the initial state(s) to the final state.

I have been told by my lecturer, however, that it should be

$$ΔH = ΔH_2 - ΔH_\mathrm{mix} - ΔH_1$$

Why are $ΔH_\mathrm{mix}$ and $ΔH_1$ subtracted?


texts: What is the explanation for this stereochemical product?

texts:
I have this reaction with a dr = 96:4 but I can't explain the product theoretically. I suppose it is some orbital interaction?

My hyporthesis is that there is a $\pi$-$\sigma^{*}$ interaction between the alcohol-group ($\sigma^*$) that draws electrons out of the $\pi$ orbital of the double bond? I cannot formulate it really. And why the ratio is so pronounced.


texts: Balanced equation for the hydration of cyclohexene to synthesise cyclohexanol

texts:
I'm trying to determine the full balanced equation for a hydration of cyclohexene to synthesise cyclohexanol using concentrated sulfuric acid as catalyst and distillation as the extraction method. I'm not quite sure if I have done the balancing right, and if the notation is correct.

Here is my attempt:

$$\ce{C6H10 ->[][{\ce{H2SO4}}] C6H12O4S ->[][{\ce{H2O}\, + heat}] C6H13O^+ + HSO4^- <->[\ce{H2O}] C6H12O + H3O+}$$


texts: Do we have a reasonable assurance that relative atomic mass is constant throughout the universe?

texts:
I know atomic mass can be (over) simplified as the average mass of all isotopes of a given element weighted by the ratio of their natural occurrence. I also know that, as far as we know, refining relative atomic mass is a matter of finding new significant figures, not finding new isotopes. Are we reasonably sure these ratios won't change as we explore the universe?

As an over simplified example, do we have a reasonable certainty that 70% of the Calcium on Mars won't turn out to be Ca-41?


texts: How can I measure the amount of quinine in a home-made tonic water?

texts:
I'm into mixology, and lately I've been looking into experimenting with home-made tonic water, by extracting quinine (quinine salts) from cinchona barks in an acidic aqueous solution. I've read a bit about the potential dangers of quinine overdose, so I want to make sure I know how much the amount of quinine is in my extract.

I know it is fluorescent under UV; I thought maybe there might be a minimum quinine-to-water ratio for fluorescence. If this is the case, I can dilute the solution gradually until the solution is no longer fluorescent. However my knowledge on this subject is fairly limited.

Is there a home-accessible way of measuring the amount of quinine in an aqueous solution?


texts:
I cannot find a definitive equation that describes the incomplete combustion of a hydrocarbon. Equations $1$, $2$ and $3$ are some of the variations I have found.

Is it,

$(1)$ $\ce{C_xH_y + O_2 \rightarrow CO + H_2O}$,

$(2)$ $\ce{C_xH_y + O_2 \rightarrow CO2 + CO + H_2O}$ or,

$(2)$ $\ce{C_xH_y + O_2 \rightarrow CO2 + CO + C + H_2O}$?


texts: How to separate a racemic mixture of 1,2-diols

texts:
[upjohn dihydroxylation]2I want to ask that i synthesise R-substituted-1,2-Diol with (ee=1:1) ratio of R-, S- with the help of Upjohn Dihydroxylation. i try to seprate it by different mobile phasese but failed to separate, then i try -OTBS at primary alcohol by wish that may it work and make two seprate points at TLC but i failed, i need both R- and S- enantiomers of Diol.
my question is that what possible method can i use to separate two diols completely or make enantio-selective diol by using different conditions like by Sharpless method.


texts: Non-zero current flow through an electrolytic cell, when an electric potential lesser than that needed for electrolysis is applied?

texts: For instance, the potential needed for water splitting is $\pu{1.23V}$. However, there is current flow even at lower potentials (say $\pu{0.5V}$). Clearly, there is no redox reaction happening in the cell as evidenced by lack of bubbles. What is the cause of this current?


texts: Is converting SMARTS to SMILES a "lossless" operation?

texts:
The following three different SMARTS strings represent the same structure - at least when depicting it (e.g. at Uni Hamburg Smarts viewer).

SMARTS:
[#6]-1=[#6]-[#6](-[#6]-[#6](-[#6]-1)-[#6])=[#8]
[#6]-1-[#6]=[#6]-[#6](-[#6]-[#6]-1-[#6])=[#8]
[#6]-1-[#6](-[#6]=[#6]-[#6]-[#6]-1-[#6])=[#8]

Also, the chemical structure represented in SMILES leads to only one string, at least only one I can think of.

SMILES:
CC1CC=CC(=O)C1

Now, I do know the differences between SMARTS and SMILES, and I do know what the symbols in SMARTS mean. Still, I tried several softwares to find any differences in the use between SMARTS and SMILES representation for that specific case, and couldn't find any.

So I wonder if I could use SMILES in that case, or if there's any danger of missing information, for example when searching for substructures?


texts: How does steric hindrance cause sulfur hexafluoride to have almost no reaction chemistry?

texts:
Sulfur hexafluoride ($\ce{SF6}$) is, according to the Wikipedia page, a hypervalent substance.  However, according to the page in regards to $\ce{SF6}$ reactions:

  There is virtually no reaction chemistry for $\ce{SF6}$. The main contribution to the inertness of $\ce{SF6}$ is the steric hindrance of the sulfur atom, whereas its heavier group 16 counterparts, such as $\ce{SeF6}$ are more reactive than $\ce{SF6}$ as a result of less steric hindrance

The linked steric hindrance provides many examples of how that chemical process works, but specifically, what steric hindrance (or any other) mechanism results in $\ce{SF6}$ possessing virtually no reaction chemistry?


texts: Equilibrium constant. Can it be reached?

texts:
Consider the reaction below:

$$\ce{A + B <=> C}$$

Suppose that the equilibrium constant for this reaction is $K = 10$.

I then prepare a reaction vessel with volume of $\pu{1 dm^{-3}}$ which contains $1$ molecule of $\ce{A}$, $500$ molecules of $\ce{B}$ and $1$ molecule of $\ce{C}$. Thus the initial concentration of each species (in $\pu{mol\cdot dm^{-3}}$) will be $1/N_\mathrm{A}$, $500/N_\mathrm{A}$, and $1/N_\mathrm{A}$ respectively, where $N_\mathrm{A}$ is the Avogadro constant.

As a result the initial reaction quotient is $N_\mathrm{A}/500$.

Now, am I right in saying that this system cannot reach equilibrium, since the only possible values of the reaction quotient are $+\infty$, $0$, or $N_\mathrm{A}/500$?

Does this arise because there simply is not enough of each reactant/product in order to reach equilibrium? I feel like this system must reach equilibrium but I'm struggling to see how the value of $K$ can be reached in this closed system.

In a bimolecular reaction step (such as the one shown above), the rate constant for the forward reaction has units $\pu{M-1\cdot s-1}$. I have learnt that if the concentration of $\ce{B}$ is increased significantly, then the Gibbs free energy of the $\ce{A + B}$ mixture will increase because the activation energy has a concentration dependence. Is this true, and is equilibrium only reached once this Gibbs free energy decreases again?

This is confusing as I am used to the Gibbs free energies of the reactants and products remaining constant while the relative amounts of each change throughout the course of the reaction.


texts: Does the name 4-nitrodiphenylmethane follow the IUPAC rules? It doesn't make sense to me. How can you assign a locant of 4 when your stem name is just methane?


texts:
Okay, so I'm trying to derive an important formula which states that -
                             ∆G(r) = ∆G° + RTln( RQ )
where ∆G(r) is the instantaneous rate of change of Gibbs energy with respect to moles of reagent consumed (am I right on this?) I'm hight confused because I have 'almost' derived it but due to some conceptual difficulty I'm not able to get the exact formula!

NOTE:
(1) Please ignore any non expansion work done on the system and tell my mistake as simply as possible because I have just started thermodynamics.

(2) The line above G represent molar Gibbs energy of substance. The small letters on the side of the symbol of reactent are the stochiometric coefficients.

(3) Many times I see variations of this formula, instead of ∆G(r) they simply use ∆G, there is a difference between two. Is this formula valid if ∆G is used instead of ∆G(r) in left hand side of equation? Also don't see any 'sense' in using ∆G because if ∆G is there then we need the initial and final quantities of the substances in the reaction but in the reaction quotient we plug the instantaneous activities of reactents and products.

I'm getting the above equation but a stochiometric coefficient is also included in this ! Obviously it is wrong. Kindly tell me my mistake.


texts: Which materials/compounds expand in response to cold temperatures?

texts:
Which materials or compounds expand in response to cold temperatures?
This material or compound should expand at a slow (but constant rate), from about 0–20 months when in the following temperature range −25 °C to −10 °C.

Also, the compound should not react with plastic or be toxic to humans or the environment.

Please explain why the compound does this as well.


texts:
Nitrogen dioxide (NO2) is a reddish brown molecule, while its dimer nitrogen tetroxide (N2O4) is colorless. Can you give a reasonably detailed explanation for this from electronic structure theory?

Previous queries were not answered because the question posed was deemed to be too broad.


texts: Physical Chemistry: Calculating ΔG, ΔH, ΔS on a given equation

texts:
This question was brought in class, but I have no clue if my answer is correct or not.

I wonder if you guys can double check my answer.

  Between $\pu{0 ^\circ C}$ and $90 ^\circ C$, the potential of a cell with $n=2$, is given by:
  $$\frac{E}{v} = 0.35510 - 0.3422\times 10^{-4} T - 3.2347\times 10^{-6}T^2$$

  where $T$ is the Celsius temperature. Calculate $\Delta G, \Delta H,
 \Delta S$ for the cell at $50 ° C$.

My answer:

\begin{align}
  E &= 0.35510 - 0.3422\times 10^{-4}\cdot 50 - 3.2347\times 10^{-6} (50)^2  \\
    &= 0.35510 - 1.711\times 10^{-3} - 8.08675\times 10^{-3} \\
    &= \pu{0.3453 V}\\[2ex]
\left(\frac{\partial\Delta G}{\partial T} \right)_P
   &= -\Delta S\\
   &= -nF\left( \frac{\partial E}{\partial T}\right)_P \\
   &= -nF \cdot (-0.3422\cdot 10^{-4} -6.4694\cdot10^{-6}\cdot T) \\
   \text{at $50 °C$,} \implies &= nF\cdot(3.5769\cdot10^{-4}) \\
   &= 69.02 = -\Delta S\\
   \therefore \Delta S &= \pu{-69.02 J//mol} \\[2ex]
 \Delta G &= nFE \\
   &= -2\cdot \pu{96485 C//mol}\cdot \pu{0.3453 V}\\
   &= \pu{-66633 kJ//mol}\\[2ex]
\Delta H &= \Delta G + T\Delta S\\
   &= \pu{-66633 kJ//mol}
      + (\pu{50 ^\circ C} + \pu{273.15 K})\cdot(\pu{-69.02 J//mol})\\
   &= \pu{88.926 kJ}
\end{align}


texts: Naming the spin system present in ethyl butanoate

texts:
I am to identify the spin system of ethyl butanoate, but I am confused as to how I should start.

I know that chemically equivalent but magnetically inequivalent nuclei should be denoted as $\ce{AA'A''}$ or $\ce{BB'B''B'''}$, etc., whereas magnetically equivalent nuclei are denoted as $\ce{A3}$, etc.

But there seem to be many chemically nonequivalent protons in this molecule.
Should I just put down this: $\ce{A3B2C2D2E3}$? How can I determine if the $\ce{CH2}$ protons are not magnetically equivalent, i.e. couple differently to neighboring protons?


texts: Which side of the C-O-C bond breaks in esters during hydrolysis in basic medium?

texts:
When an ester undergoes hydrolysis which side of the $\ce{C-O-C}$ breaks for instance in the following example:

I believe the first is correct but is it a rule that the salt of a carboxylic acid is formed (and then of course in the presence of $\ce{-OH}$ an alcohol also forms)?
Basically which carbon does the original O of the $\ce{C-O-C}$ stay with?


texts:
Predict the products of the controlled oxidation of 2-methylpentan-2-ol.

From what I know, since 2-methylpentan-2-ol is a tertiary alcohol, there should be no reaction. However, my textbook states that the product includes 2-methylpentanone.

Edit: In response to the comments, my textbook neither specifies the isomer nor mentions any given conditions. I hate Nelson


texts: How do I find out if ions are oxidised/ reduced based on half cell potentials?

texts:
Assuming standard conditions, answer the following questions.
  (yes/no)

  Is $\ce{Fe^{2+}(aq)}$ capable of reducing $\ce{Cr^{3+}(aq)}$ to $\ce{Cr^{2+}(aq)}$?
  Is $\ce{Sn^{2+}(aq)}$ capable of oxidizing $\ce{Fe^{2+}(aq)}$?
  Is $\ce{Cr}$ metal capable of reducing $\ce{Fe^{2+}(aq)}$?
  Is $\ce{VO^{2+}(aq)}$ capable of oxidizing $\ce{Fe^{2+}(aq)}$?
  Is $\ce{H2(g)}$ capable of reducing $\ce{Ag+ (aq)}$?
  Is $\ce{Cr^{3+}(aq)}$ capable of oxidizing $\ce{Fe^{2+}(aq)}$?

I have

yes
yes
no
yes
yes
no

What am I doing wrong?


texts: How to write mass balance equation for the scenario when molecules are getting generated inside an sphere?

texts:
I am working on the physical understanding of diffusion through a nano machine(a shell with hollow interior in which molecules are produced) and have taken few assumptions:

There is rate $r_T$ with which molecules are produced inside this machine, and  we are not concerned with the production process.
The machine is spherical shell and emitting molecules through pores on its body.
We are diffusing in an infinite radius sphere where the center of the nano machine coincides with the center of sphere and is stationary.
Let the radius of the spherical be $r+\delta r$ where r is the radius of inner side region where mass is getting produced with rate $r_T(t)$ and $\delta r$ the width of shell. $j_1$ is flux per unit area.
Assuming that there is a porous outer through which molecules are diffusing with Partition coefficient 'H'.

Now I am trying to write mass balance equation for it so as to get diffusion flux in terms of concentration.For this I apply this formula:
input +generation-output-consumption=accumulation
Taking its rate/differential form, I know that rate of accumulation in $\delta r$ will be zero.

so, by somewhat same approach as when we have a spherical solute dissolving sparingly in water I got:
$$r_T(t)+(4\pi r^2j_1)_r - (4\pi r^2 j_1)_{r+\delta r}=0$$ and when I try to solve it taking $\delta r$ to be very small and dividing both sides by the volume of the shell, I got this equation:
$$\frac {r_t(t)}{4\pi r^2 \delta r}=\frac{1}{r^2} \frac{d (r^2 j_1)}{dr}$$

which seems to be unbalanced, further applying it to Fick's first law doesn't make any sense. How should I proceed in my case? Is my mass balance equation wrong?
$$$$


texts: Electrolysis of aqueous copper (II) nitrate

texts:
There are two copper blocks sitting in the $\ce{Cu(NO3)2 (aq)}$ solution, a battery is attached onto both of them, providing enough energy to start the reaction.

Since solid pieces of copper are involved, $\ce{Cu}$ must be considered in the reduction potential as well.

However, looking at the half reaction for copper:
\begin{align}
  \ce{Cu (s) &-> Cu^2+ (aq) + 2e-}&
  (E^\circ &= \pu{+0.34 V})
\end{align}

Compared to nitrate:
\begin{align}
  \ce{NO3- (aq) + 4H+ (aq) + 3e- &-> NO (g) + 2H2O (l)}&
  (E^\circ &= \pu{+0.96 V})
\end{align}

Since it produces more energy, I believe the second half reaction will occur instead.

I begin by finding all the species/ions I have:

$\ce{Cu^2+}$
$\ce{NO3^-}$
$\ce{H2O}$

Taking a look at the Standard Reduction Potentials at 25°C:

For my SOA (strongest oxidizing agent) half-reaction ($\ce{NO3^-}$):
\begin{align}
  \ce{NO3^- + 4H+ + 3e- &-> NO + 2H2O}&
  (E^\circ = \pu{+0.96 V})
\end{align}

As for my SRA (strongest reducing agent) half-reaction ($\ce{H2O}$):
\begin{align}
  \ce{2H2O &-> O2 + 4H+ + 4e-}&
  (E^\circ &= \pu{-1.23 V})
\end{align}

For the balanced reaction I have:
\begin{align}
  \ce{4NO3- + 4H+ &-> 4NO + 2H2O + 3O2}&
  (E^\circ &= \pu{-0.27 V})
\end{align}

Some observations that can be made are that:

Nitric gas is forming at the anode
Oxygen gas is forming at the cathode
At least $\pu{0.27 V}$ must be put in

My question is:

Did I do all of this correctly? There's no answer key and I'm pretty sure that I might have made a mistake somewhere.
What would happen if you placed a necklace at the cathode?


texts: Help with Forster distance conversion for FRET

texts:
For my project on Fluorescence, I'm trying to simplify the equation for the Forster distance (I obtained this from the Lakowicz book). To keep track, the units are in square brackets.
$$R_0 = \left(\frac{9000\kappa^2\Phi_D\ln(10)}{128\pi^5N_An^4}J(\lambda)\right)^{1/6} \approx 0.211 (\kappa^2n^{-4}\Phi_DJ(\lambda))^{1/6}\, [Å]$$
I'm using $J(\lambda)$ in units of $M^{-1}cm^{-1}nm^4$ but for some reason I can't seem to obtain the $0.211$ no matter how I do the conversion. I always seem to be off by a factor of $10^{-3}$, which I can't seem to locate.
For reference, $J(\lambda)$ is the overlap integral:
$$J(\lambda) = \frac{\int_0^{\infty} F_D(\lambda)\varepsilon_A(\lambda)\lambda^4 d\lambda}{\int_0^{\infty} F_D(\lambda) d\lambda}$$
For example, I simplified $R^6_0$, attempting to convert to Angstrom:
$$8.79\times10^{-25}\kappa^2\Phi_Dn^{-4} J(\lambda) [mol\,M^{-1}\,cm^{-1}\,nm^4]$$
$$=8.79\times10^{-25}\kappa^2\Phi_Dn^{-4} J(\lambda) [0.1m^210^{-36}m^4]$$
$$=R^6_0 = 8.79\times10^{-62}\kappa^2\Phi_Dn^{-4}J(\lambda) [m^6] = 8.79\times10^{-2} \kappa^2\Phi_Dn^{-4}J(\lambda)\,[Å]^6$$
Which, upon taking the 6th-root, I don't get the number $0.211$. If the power is $10^{-5}$ I do get the number.
What am I missing?
Any help appreciated. I'm not sure if I'm overlooking something painfully obvious, but I can't see it.
Cheers!


texts: Ozonolysis: mechanism for reductive workup of ozonide using Zn/Acetic Acid/Water

texts:
What is the mechanism for the reductive workup of an ozonide using zinc/acetic acid/water? Many sources online show the mechanism using DMS instead:

https://www.khanacademy.org/science/organic-chemistry/alkenes-alkynes/alkene-reactions-tutorial/v/ozonolysis-1

https://www.youtube.com/watch?v=PcO49xCb4Gs


texts: Number of total stereoisomers of a piperazine derivative

texts:
How do I find out the total number of stereoisomers of 3,6-dimethylpiperazine-2,5-dione?

As far as I can see, the compound has two chiral carbons. Would the nitrogens make a difference? They seem chiral as well (three different groups and a lone pair).

My book says there are 3 total stereoisomers, but I expected more. It has considered only two chiral carbons, and nothing has been said about the nitrogens. Why?


texts: Which combinations of orbitals lead to pi bonds according to Valence Bond Theory?

texts:
How many of the following combination of the orbitals will lead to formation of $\pi$-bonds with $z$ axis being the internuclear axis:
$$p_x+p_x,\,p_z+p_z,\,p_y+p_y,\,d_{zx}+p_x,\,d_{zy}+p_y,\,s+p_y,\,d_{yz}+d_{zy},\,d_{zx}+d_{zx},\,d_{z^2}+s$$

My attempt/Understanding:
According to  Valence Bond Theory, any orbital having any relations with $z$-axis or $z$ related planes should form $\sigma$-bonds. This is because $z$ is internuclear axis and these orbitals will have direct overlapping, forming $\sigma$-bonds.
Rest orbitals will form $\pi$-bonds by lateral overlapping, so I counted them as answer $(4)$:
$$p_x+p_x,\,p_y+p_y,\,s+p_y,\,d_{xy}+d_{xy}$$
But answer given is $(6)$, and it is not mentioned which are orbitals are counted. So, please tell which orbitals are to be counted for, and tell any flaws in my understandings, if any.


texts: How to determine the order of acidity of the following dimethyl nitrophenols

texts:
This is how I went about it, although I got a wrong answer:

3,5-Dimethyl-4-nitrophenol (2) shows the nitro group to be sterically hindered, due to which it should go out of plane and this will be an example of the steric inhibition of resonance. Hence, there will only be a weak withdrawing inductive effect, and no resonance. Thus, this should be the least acidic.
4,5-Dimethyl-2-nitrophenol (3) shows a hydrogen bonding between the nitro and the hydroxyl group, due to which there will be a lower tendency to release the proton. Hence, even this should be less acidic.
Between 2,6-dimethyl-3-nitrophenol (1) and 2,4-dimethyl-5-nitrophenol (4), (1) should be weakly acidic due to the hyperconjugation destabilisation caused by the two methyl groups, and hence the answer should be (4), with lower hyperconjugation, lower induction from the methyl groups, and higher induction from the nitro group (no resonance at the meta position).

However, the answer is given to be (2), which I ruled out first.

Can someone please explain what is happening, and where I've gone wrong?


texts: Why does nose grease knock down the head on beer and soda?

texts:
Freshman year, my first semester, I was taught many things.  One important trick I learned was when I was passed a beer in a 12 oz. plastic cup, I could eliminate the fresh foamy head by wiping my nose and touching it to the top of the foam.

I thought to do this recently with soda (as it seems soda head is more persistent).  The trick works there too.

What is the chemistry behind this?  Is it the salinity?  Could I use something less revolting than nose grease to do the same trick?


texts: Stability of carbocation intermediates: secondary alkane versus primary allyl?

texts:
Say I have the following carbocations:

The first is secondary; the second is resonance stabilized, but primary.  Which is more stable and why?

I've been looking around in my textbooks and haven't been able to find a comparison.  This site compares alkane and alkene intermediate stability, but only with the same degrees of substitution.


texts: Gas evolution in reaction between zinc and HCl

texts: So I was doing a chemistry lab for school, and we were analyzing how the concentration of a solution affects the rate of a reaction. In order to do this, we used the inverse burette method for the reaction between zinc and HCl, which would produce hydrogen gas. We had an Erlenmeyer flask connected to the burette by a red tube, and the reaction would occur in the flask. I noticed that the flask stayed blurred, meaning that the hydrogen gas would be trapped inside of it. I asked my teacher if that meant that the pressure was not enough for the hydrogen to displace the water, but he said that was wrong. I cannot think, however, another reason for that. I would appreciate any help.


texts: How do I calculate the amount of preservatives one would need for a cleaning solution?

texts:
I plan on making a very simple cleaning solution to clean metal contacts on PCB boards. It cannot contain anything that is flammable or hazardous so I've come up with the solution below.

Distilled Water ~92%
Ethoxylated Alcohol (CAS 68439‐46‐3) ~5% "surfactant"
Tetrasodium Glutamate Diacetate (CAS 51981-21-6) ~1% "chelating agent"

I am not making this solution in a perfectly sterile environment so I would like to add a preservative to increase shelf life. I've been researching for weeks and I cannot find anything definitive. I just want something that will easily dissolve into the solution above and not be harmful to metal. The solution will be applied to the metal via a cotton swab. Even if I find a suitable preservative how would I go about calculating how much to use?
My ideas for preservatives:
I think Citric Acid (CAS 77-92-9) would be okay. I think a combination of Methylchloroisothiazolinone (CAS 26172-55-4) and Methylisothiazolinone (CAS 2682-20-4) would be okay as well.
Other concerns are: Do I need an emulsifier? Is there an additional non-hazardous chemical I can add to decrease drying times?


texts: Determine if the following change is an oxidation, a reduction, or neither

texts:
The following reaction is not a complete reaction. Determine if the change is an oxidation, a reduction, or neither:
  $$\ce{CrO4^{-2} -> Cr2O7^{-2}}$$

I know that the answer to this problem is neither, but I don't have any idea as to how that answer is reached. Could anyone give me a hint? I am familiar with oxidation, reduction, and oxidation numbers.


texts: Struggling to understand wavevector K for deriving energy levels in reciprocal space

texts: I don't really understand why, when deriving wavefunctions for arrays of atoms, the wavevector k is introduced and the general idea surrounding momentum space. please help!!


texts: Why does helium seem to exhibit an ionization energy affected by the shielding of electrons?

texts:
According to Wikipedia, the shielding effect only happen in atoms which have more than 1 electron shells. The core electrons repel the electron in the valence shell. However, I have heard some lectures mention the shielding effect on helium atom when they explained why the first ionization energy of $\ce{He}$ is not exactly 2 times more than $\ce{H}$.

Why is this? According to the definition of shielding effect, there shouldn't be one in $\ce{He}$ atom.


texts: What is the meaning of scores when comparing reaction classes in the KEGG database

texts:
With respect to related R class in KEGG website:
http://www.genome.jp/tools-bin/relclass?RC00064   What is the biological or statistical relevance of the score? How is it computed? And does it signify the bonding strength of how probably it is for a pair of compounds to be an R pair?
Note: This may be a silly question to all chemists, but not for me, i am a computer science student , and my research field in bioinformatics and so i have to study both biology and bit of chemistry, so please just dont close the question or be harsh on me, I have very little knowledge in chemistry and also googling doesn't help much. I asked this question in Biology forum, they closed the question and asked me to ask it here


texts: Why does an acid salt possess acidity as well as basicity?

texts:
For example, $\ce{BaHPO_{4}}$ has acidity of 2 and basicity 1.

Why does this so? Its basicity is 1 because it has 1 replaceable hydrogen ion.
But why does this have acidity?


texts: What is defined by part by weight in the definition of equivalent weight?

texts: According to my book, equivalent weight is defined as the ‘number of parts by weight’ of an element that interacts with 1.008 parts by weight of hydrogen. It is dimensionless while gram equivalent weight has gram as units. But in https://en.wikipedia.org/wiki/Equivalent_weight, equivalent weight and gram equivalent weight are same. I’ve two questions: Which one is correct, my book or Wikipedia? And what is ‘number of parts by weight’?


texts: Why do we use the Schotten-Baumann synthesis method for the synthesis of amides?

texts: Recently, I learnt about the Schotten-Baumann synthesis method. I know that this synthesis method was invented to overcome the problem of neutralising the acidic by-products of the amide synthesis reaction without introducing strong basic nucleophiles to compete with the amines. The alternative to this synthesis method would be to use two equivalences of the amine, allowing the 2nd equivalence of the amine to act as a base to neutralise the acidic by-product. I would like to enquire more about the differences between these two synthesis methods. In particular, I would like to know the advantages and disadvantages of each of these synthesis methods.


texts: Can someone help with the nomenclature of this metal complex. MarvinSketch is giving me trouble

texts:
I’m trying to get a name for the structure above using MarvinSketch for my undergraduate senior thesis. This is the first time I’ve had to draw a metal complex in MarvinSketch, and I’m having trouble getting the program to name it as is.
Right now, using the “structure to name” feature, the name I’m getting is 8,14‐dimethyl‐2-λ-4,20-λ-4,21-λ-4,27-λ-4‐tetraaza‐1-cobaltaheptacyclo[12.6.6.11,9.02,7.015,20.021,26.013,27]-heptacosa2(7),3,5,9(27),10,12,15(20),16,18,21(26),22,24‐dodecaene‐1,1‐diol, and I’m pretty darn sure that’s wrong.
I think this issue is that I drew the water molecules as being attached to the carbon via coordinate bonds but the polypyridine ligand as being attached by normal single bonds. I did this because the program wouldn’t even give a name if all bonds were drawn as coordinate bonds, and if I try to show the water molecules being attached by normal bonds, the program always either gives the waters a formal charge or removes one of the hydrogens to make it an -OH bonded to the cobalt.
I was wondering if someone could help me figure out how to get the program to properly name this complex, and perhaps also help me get the program to stop adding a formal charge/removing one of the hydrogens from the waters if I change the bond type to not be coordinate.
This is not a very important part of my thesis so if there’s no relatively easy way to get the IUPAC name I’m not going to worry about it (though it would be nice). I also unfortunately don’t have access to books on nomenclature from my school with us being remote.
Thank you very much


texts: Is the 12-6 Lennard Jones potential a good description of van der Waals interaction energy?

texts: It seems to me that the Lennard Jones potential oversimplifies the more complex nature of van der Waals forces. However, in most of the MD simulation package, this is generally accepted.


texts: Is there a way to cheaply transfer (plunge by pushing) a viscous liquid in to another container without plunger-to-tube discharge?

texts: Could anyone offer a suggestion as to how an economy-minded chemist ought to implement a DIY-ed positive displacement alternative to the following:


texts: What is the mechanism for this reaction?

texts:
The closest reaction I can find is Lossen rearrangement but in that hydroxyamic acid is first converted to its derivative but how will that be possible here?

Moreover, even if I make an amine in this step I cannot proceed further, how will the amine and alcohol react in the next step? Any hints would be appreciated.


texts: Why does adipic acid give a cyclic ketone on heating while glutaric acid and succinic acid give a cyclic anhydride?

texts: Why does adipic acid give cyclic ketone on heating while glutaric and succinic acid give cyclic anhydride?


texts: I am asked to identify the highest and lowest energy conformations for the following bond-line structure (I think it is 2,2-dimethylbutane). I drew a Newman projection (for all 6 conformations) and was able to identify the lowest energy conformation correctly but the textbook solution for the highest energy conformation does not match what I drew. It seems as though the textbook solution is missing a methyl group, and has 3 $\ce{H}$ bonds instead. Can someone please clarify?


texts: Why do the atoms in molecular models have the colors they have?

texts:
Molecular models are a great tool for visualizing a molecule in three-dimensional space. These models even appear on the web (practically every chemical's Wikipedia page), and there is a very specific color coding for atoms. After some searching I found that it was called the CPK coloring system. It seems rather intuitive for some elements, like for $\text{carbon}$, $\color{\green}{\text{fluorine}}$, and $\color{\yellow}{\text{sulfur}}$, which use the colors for the elemental forms of these atoms (diamonds aside).

On what basis, though, did Robert Corey and Linus Pauling choose the colors for $\color{\red}{\text{oxygen}}$, $\color{\turquoise}{\text{nitrogen}}$, and hydrogen (I'm not going to do white on white). Were these arbitrary choices that had to be made for these colorless elements, or is there some reasoning behind them?


texts: How many significant figures are appropriate when a new digit is created?

texts:
In my chem class the other day, we were working through a question about average atomic mass. We were given the following information about two isotopes of boron:

Boron-10: Atomic Mass = 10.013, % in nature: 19.8%

Boron-11: Atomic Mass = 11.009, % in nature: 80.2%

For the weighted average (before sig fig rounding), then, Boron 10 contributes 10.013*.198 = 1.982574 AMU, and Boron 11 contributes 11.009*.802 = 8.829218 AMU.

Now, if we were just finding one of these values, we would report 1.98 or 8.93 AMU (to 3 sig figs). Adding these together, we get 10.81 AMU. However, if we follow "convention" and do all rounding at the end, we get 10.8 AMU (3 sig figs).

My question is, which of these is correct? On the one hand, 10.8 is correct since it has the same number of sig figs as the least accurate given value (19.8% or 80.2%). On the other, why should we go from hundredths to tenths precision just because we got a new digit in the least precise position? One could argue that the "10" is essentially its own digit.

Personally, I agree with the response here (Significant Figures Interpretation) that says sig figs don't make a whole lot of sense. But for the purposes of this question, which is the proper way to express the answer?

Thanks in advance!


texts:
Is it possible to work out the x-coordinates related to high symmetry points?
The software I'm using doesn't provide me with that, so I was wondering if there is a way to manually figure it out, as I would like to add high symmetry point labels to an electronic band structure plot.
I found a similar question: https://lists.quantum-espresso.org/pipermail/users/2016-June/035548.html but I don't quite understand whats happening in the equation, if someone could please explain it that would be appreciated.
Thanks


texts: Byproducts of LiAlH4 reduction of amides

texts:
I know that $\ce{LiAlH4}$ is able to reduce amides into amines, e.g. benzamide into benzylamine. However, I am unsure what other by-products are formed as a result.

$$\ce{LiAlH4 + C6H5CONH2 -> C6H5CH2NH2 + H2O + ??}$$


texts: What is the meaning of the slope in a graded dose-response curve?

texts:
A graded dose-response relationship is shown below with the drug concentration on the $\log$ scale on the $x$ axis and the response on the $y$ axis :

According to this website:

Slope:  a useful parameter - when it is shallow, it suggests a greater chance of overlap between desired effects and side-effects, whereas a slope which is too steep suggests that it will be difficult to achieve precise control of the effects.

I want to understand how does the slope as $\frac {Response} {concentration}$ have the meaning mentioned above?


texts: Software for chemical reaction simulation

texts: I wonder, what software packs / environments are available for chemical reaction simulation. The goal is to learn or just rehearse some basic knowledge in chemistry. I suppose there should be some to buy but are there any open source projects dedicated to this?


texts: Calculating standard combustion enthalpy of dodecane from that of heptane & octane

texts:
These are the problem from UKChO-2015.

  Given the standard enthalpy changes of combustion ($\Delta_\mathrm{c}H$) for heptane ($n = 7$) and octane ($n = 8$) are $-4816$ and $-5470~\mathrm{kJ~mol^{-1}}$ respectively, calculate $\Delta_\mathrm{c}H$ of dodecane ($n = 12$).

Any hint on regarding this problem? My efforts are not worth mentionable here


texts:
Does fluorine ever form a double or triple bond?
I wonder if seeming lack of such higher order bonds is related to the electronegativity of fluorine.


texts:
Is it possible by any means or by using some reagents to convert
hexane to 1,6-dibromohexane? The yield should also be good.


texts: Determine minimum C-H bond length in ethane derivatives

texts:
Which of the following compound has minimum C-H bond length?

  ethane
  ethene
  1,2-dibromoethene
  1,2-dibromoethane

How can we know the comparison of $\ce{C-H}$ bond length (not $\ce{C-C}$)? Also, there is not any reagent given, so that we would do dehydrohalogenation reaction at it. How to compare it simply?


texts: Material with refraction index similar to Si

texts:
I am looking for a material with a refractive index over the visible spectrum , which is close to the refractive index of Si, but which does not oxydise in air.

Do you know of any such material ?

Thank you.

Edit:
Some more information. A optical reflector should be build from Si. I will not go into the detail, since it is irrelevant to the question, but I will provide all necessary information. The list is ordered according to importance:

The complex refractive index should be close to Si over the entire visible spectrum
The material should not oxydize in air
The working conditions should be between -30°C to 60°C.
Not necessary, but it would be great if epitaxy on single-crystal silicon is possible.


texts: On the directing nature of these groups in electrophilic aromatic substitution

texts:
These three groups are listed in our workbook. I don't know the answer and our teacher isn't sure either:

(each has a free valency through which it is attached to a benzene ring):

Diphenylhalomethyl
Difluoromethyl
Dichloromethyl

Now, I've read and understood this question - How does hyperconjugation lead to the directing properties of alkyl group? Therefore, I think that the groups 2,3 are deactivating (due to -I effect of fluorines and chlorines) yet o/p directing due to hyperconjugation with the H atom. On the other hand, the first group should be meta directing since it has only -I effect and no +/-M or hyperconjugation.

I googled for the complete list of directing groups but I could not find these types of groups.

  Is my reasoning - and hence answer - correct? Or is there another answer, and why?


texts: Michaelis–Menten kinetics applied to a solution with two enzymes

texts:
Two enzymes are added to a solution containing a tow concentration of a substrate that they can both use. Which statement is correct?
A. Both enzymes will use equal amounts of the substrate.
B. Neither enzyme will be able to use the substrate.
C. The enzyme with the lower $V_\mathrm{max}$ will use less of the substrate than the other enzyme.
D. The enzyme with the lower $V_\mathrm{max}$ will use more of the substrate than the other enzyme.

Why is the answer to this question D? Shouldn't it be C?


texts: Titration curve, how to find equivalence point

texts:
If you have a graphed titration curve and have points near the equivalence point like

6.85 pH at 54.60mL titrant added and
8.01 pH at 54.73mL titrant added

is there any good way to find a more exact volume at which the equivalence point was reached other then taking a guess between those two volumes?


texts: Why is lithium the most reducing alkali metal, and not caesium?

texts: Caesium has a larger size, and the effective nuclear charge that the valence electron experiences will be far less compared to that of lithium's, right? But lithium is still considered the strongest reducing agent among all the alkali metals, and this is evidenced by its large and negative reduction potential. Why is this so?


texts:
At $25\ \mathrm{^\circ C}$ the vapor in equilibrium with a solution containing carbon disulfide and acetonitrile has a total pressure of $263\ \mathrm{torr}$ and is $85.5\ \mathrm{mol}\text{-}\%$ carbon disulfide. What is the mole fraction of carbon disulfide in the solution? At $25\ \mathrm{^\circ C}$ the vapor pressure of carbon disulfide is $375\ \mathrm{torr}$. Assume that the solution and the vapor exhibit ideal behavior.

I was gonna use Raoult's law but like how is the molar percentage different from the molar fraction, isnt it the molar fraction times 100? also I checked the solution manual and it had the molar fraction sign but with an L or V above it, and theres no such thing in the boook, can anyone help or explain what is that?


texts:
According to my chemistry textbook, 2-hydroxy-1,2,3-propanetricarboxylic acid is represented as:

But 5-bromoheptanoic acid is given as:

In the former naming, propane is considered in the base chain while the COOH carbons are not. In the latter one,  the COOH carbons are considered in the base carbon chain.

On checking NCBI Pubchem, I found the following:

https://pubchem.ncbi.nlm.nih.gov/compound/16217547#section=Top
https://pubchem.ncbi.nlm.nih.gov/compound/5-Bromovaleric_acid#section=Top

Why are the carbons of carboxylic acids excluded in the former name but included in the latter?


texts: Interaction of trifluoroacetates with acetylcholinesterase

texts:
There exists a substance called TMTFA, or 3-(N,N,N-Trimethylammonio)-2,2,2-trifluoroacetophenone. It is known for being able to inhibit acetylcholinesterase at femtomolar concentrations. The TMTFA-AChE adduct resembles the tetrahedral transition state through which the hydrolysis of acetylcholine by the enzyme normally proceeds, and this adduct is stabilized by the electron-withdrawing trifluoromethyl group present in the TMTFA molecule. This inhibition is reversible.
While there have been studies regarding trifluoroacetophenones and their interactions with AChE, I haven't been able to find studies exploring the interactions between AChE and trifluoroacetates, such as 3-(N,N,N-trimethylammonio)phenyl trifluoroacetate or 2,2,2-trifluoroacetylcholine. Would these, and other, esters of trifluoroacetic acid inhibit AChE or be hydrolyzed normally? If it's the former, then what are the typical inhibitory concentrations of such esters? What is the shape of the adduct of the ester with AChE? How long would they remain bound to the enzyme? Have any studies been done regarding the bioactivity of such esters?
References

Nair, H. K.; Seravalli, J.; Arbuckle, T.; Quinn, D. M. Molecular Recognition in Acetylcholinesterase Catalysis: Free-Energy Correlations for Substrate Turnover and Inhibition by Trifluoro Ketone Transition-State Analogs. Biochemistry 1994, 33(28), 8566–8576. DOI: 10.1021/bi00194a023.
Harel, M.; Quinn, D. M.; Nair, H. K.; Silman, I.; Sussman, J. L. The X-Ray Structure of a Transition State Analog Complex Reveals the Molecular Origins of the Catalytic Power and Substrate Specificity of Acetylcholinesterase. J. Am. Chem. Soc. 1996, 118(10), 2340–2346. DOI: 10.1021/ja952232h.


texts: Anion formation in an alpha particle-neutral atom interaction?

texts:
How can an alpha particle/beta particle/gamma rays interacting with a neutral atom lead to an anion forming? Because i can see how they cause loss of electrons leading to cations forming, but how can anions form?
cheers


texts: What kinds of molecules will experience hydrogen bonding (inter and intra)? Why does it occur for some H atoms but not others?


texts: What is the mean curvature of nitrates and nitrites?

texts:
I am reading the book Soft Matter Physics - Synthetic and Biological Self-Assembling Materials from Hamley and particularly page 201.

I started to think how this packing occurs in case of molecules or molecular patches, particularly in case of nitrates and nitrites because they have highest priority set by WHO in their drinking water guideline.
The curvature can be defined as the amount by which a geometric object deviates from being flat.

You can assume that these molecules clamp together such that there is no other interactions.

How can you approximate the mean curvature of nitrates?


texts: I know there are different types of salts like Himalayan salts table salts etc. I was wonder do different types of salts have a different level in salinity when dissolved in water.


texts: How to partially hydrolyze triglycerides?

texts:
How to partially hydrolyze triglycerides for food application?

I want to make a mixture of mono- and diglycerides starting from triglycerides.


texts: Are allylic three degree alcohols oxidized by the Jones' reagent via a classical carbocation intermediate?

texts:
I know the mechanism for Jones' oxidation is (picture from Organic Chemistry by Clayden):

and it proceeds through a chromate ester. And in general we understand that the Jones' reagent $\ce{H2CrO4}$ cannot oxidize three degree alcohols.

However, in my book, a question asked to oxidize the following three degree, allylic alcohol:

The solution proceeded via a carbocation intermediate to eventually form 3-methylcyclohex-2-en-1-one.

I wish to ask if this a correct solution. Does this reaction really occur? That too in the way it is described? If so, why isn't it described in any other book, even as an exceptional case? (Most other books simply accept that three degree alcohols cannot be oxidised) Or is this a by-product or a low-yield reaction?

Source: MS Chouhan; Advanced Problems In Organic Chemistry; 11th ed; Q19; Alcohols, Ethers, Epoxides


texts: Which term for heat energy in calorimetry is correct in scientific usage?

texts:
In calorimetry several terms are interchangeable:

Lower Calorific Value
Lower Heating Value
Net Calorific Value
Net Heating Value

The following terms also appear to have identical meanings:

Higher Calorific Value
Higher Heating Value
Gross Calorific Value
Gross Heating Value
Gross Energy

So far I can think of several factors affecting which term should be used.

In the days of the early discoveries of calorimetry, Latin was just
as much of a research language as English, so interchangeability of
the terms calorimetric (which derives from the Latin word calor
meaning heat) and heating would be understood.
The word value sounds like a non-specific reference to a number.
The unit Calorie is not part of the SI standard though it is derived
from SI units.  In the context of describing the energy required to
raise the temperature of water it may be appropriate.

It seems like gross or net heat energy would be the best term for scientific usage.  Does any standard or consensus exists which defines which of these terms are best to use?


texts: How can I predict if a reaction will occur between any two (or more) substances?

texts:
I am new to chemistry and I find it fascinating. I am trying to learn about chemical reactions and I was wondering if there was an easy way to quickly tell if any combination of chemical substances would produce a reaction and what product(s) if any might be formed.

For example, if I pick any two random substances $\ce{A}$ and $\ce{B}$, can I determine if a reaction will occur and predict the products?

$$\ce{A + B -> \ ?}$$

More specifically, let's say I just learned that chlorine bleach (sodium hypochlorite) can be made by a reaction of sodium hydroxide and chlorine with sodium chloride as a byproduct:

$$\ce{NaOH(aq) + Cl2(g) -> NaOCl(aq) + NaCl(aq)}$$

Is there a way that I could have predicted this reaction (and any other) before I learned about it? I do not want to memorize the outcome of every combination o that I can answer questions about chemical reactions. I am hoping there is a short list of simple rules that govern all chemical reactions that I can commit to memory and then apply to any combination of substances. I might also like to be able to develop a simple computer program built around an algorithm for these reactivity rules that can sample databases of known substances and predict new reactions.


texts: Nice textbook illustration of microwave spectrum for a nearly free internal rotation?

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Is it possible to find a nice textbookish example of experimental data for an internal rotation of a molecule, in which the rotation is nearly free? For example, 1-butene is supposed to have a nearly free rotation about its middle bond.

It would be fun, for example, to be able to show a microwave spectrum for this molecule that demonstrates the evenly spaced photon energies of a rotor.


texts: Reaction with tin(IV) iodide and hydrogen peroxide

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Today I reacted tin(IV) iodide $\ce{SnI4}$ (dissolved in water) with hydrogen peroxide. This produced a yellow/brown colour (I'm guessing due to formation of $\ce{I2}?).$

I then added some petroleum spirit which gave a bi-phasic system which was a clear/pink/ light purple colour on top and an orange-brown yellow underneath.

I'm struggling to find out what reactions have occurred here, can anyone please help?


texts: Is it possible to distinguish between cyclohexanol and cyclohex-2-en-1-ol with simple chemical test?

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Primary, secondary and tertiary alcohols can easily be distinguished by using reagent tests such as:

The triiodomethane test for $\ce{R-CH(CH3)OH}$ alcohols.
Lucas' reagent to distinguish between three alcohol groups.
A combination of reagents to distinguish between three alcohols. For example, dichromate to distinguish between tertiary and primary/secondary alcohols and subsequently Fehling's solution to distinguish between primary and secondary alcohols.

Would it be possible to distinguish between two secondary alcohols? For example, between cyclohexanol (1) and cyclohex-2-en-1-ol (2) using simple chemical tests?


texts: Dirac notation when bra and ket aren't vectors

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So, I know that
$$
\langle \psi_j(x)|\psi_k(x) \rangle =\int_{-\infty}^{\infty} \psi_j^*(x) \psi_k(x) \,\mathrm{d}x
$$
and I was wondering that if this is because of the inner product rule as with vectors? Like $\langle a|b \rangle$, but the $\psi$ isn't a vector, so how would this work in this case?


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I am doing a project on the physics of the spaceX raptor engine. I believe it is made out of a certain type of inconel alloy. I want to understand why this alloy has the properties that it does, but I don't know anything about materials science. I am a senior physics major.
I am looking for a good introductory text/texts that will give me insights into the properties of inconel so I can explain why it doesn't flare at high temperature+pressure in my paper.
Any other advice would be welcome as well. Thanks for the help!


texts: Function of sodium amalgam and CO2 in formation of aldohexose

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There is this following conversion in my book:

$$\gamma-\text{Lactone}\ce{->[Na/Hg +CO2]}\text{Aldohexose}$$

I'm not sure how this reaction takes place. I searched for mechanisms and couldn't find one.What's the function of CO2? Any help is appreciated.


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This is a question regarding the crystallization of $\ce{KAl(SO4)2 . 12 H2O}$. I have an idea of what to do (I'll explain later in the explanation), but I would like to hear other suggestions encase the following ideas do not work out.

I placed a specific amount of the salt into hot distilled water and began stirring, later setting it out to grow my seed crystals. I have been waiting for the past 3 days to receive any potential seed crystals, however, I have not received even one. I noticed that over the 4 days a significant amount of water has evaporated, and at the bottom of the beaker has accumulated a white powder I'm assuming is the $\ce{KAl(SO4)2 . 12 H2O}$. I fail to understand why it has not crystallized into a small singular crystal?

My idea is to scratch the bottom of the beaker (it is new) to provide a location for the crystal to begin it's growth. Another idea pertains to adding more solute ($\ce{KAl(SO4)2}$) into the solution. Honestly, I don't know why I would add more solute if I am seeing the powder fall out of the solution. This should mean it is already saturated. Finally, I am deciding about adding some of the undissolved salt from the packet, into the solution. Hopefully this would provide a nice "infant crystal" (I am aware that there is no such thing an "infant crystal", I simply want to refrain from referring to "seed crystal" since these are not my seed crystals.) for my ions (dissolved solute) to latch onto and form my seed crystals.

Any suggestions would be appreciated.

Just to mention, my final technique drives through a more mathematical approach. I found the molar solubility from the $\mathrm{p}K_\mathrm{sp}$ of the crystal ($\mathrm{p}K_\mathrm{sp}$ of salt from aqion.de) I did my calculations to see a total of 0.3 grams of $\ce{KAl(SO4)2}$ per $1~\mathrm{mL}$ of water to obtain a saturated solution. Aesthetically, this doesn't make any sense to me. I feel the website I used may not have provided accurate experiments to reveal the $\mathrm{p}K_\mathrm{sp}$. If you can link me to any other websites or locations I would be more than grateful.


texts: Reaction of iron(III) oxide with nitric acid

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I'm currently working in a project in which I have to convert the iron oxides present in iron ore slime into ferric nitrate.

Iron ore slime is which has the particle size of below $\pu{0.15 mm}$ is being discarded as waste during the mining and processing stages iron ore and it will be stored at the tailing dam. It is estimated that $18~\%$–$25~\%$ of tailing will be generated during the processing of iron ore. The major compositions of iron ore slime are hematite, quartz, alumina, mica. So basically, it consists of ferric oxide and alumina, silica, magnesia, calcia, etc. impurities. I wanted to extract the iron part of the slime by converting it into water soluble ferric nitrate leaving behind the insoluble impurities. Even if some soluble impurities like clacium nitrate is formed then its not a problem.

I tried treating the slime with nitric acid both concentrated and dilute but no reaction was observed.
Please suggest me some useful ways to get ferric nitrate from iron ore slime — or any other steel industry waste product like mill scale, slag etc.


texts: Is it possible, given a target temperature, to create an alloy that melts at precisely that temperature?

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Assuming the target melting points are between the melting points of mercury and tungsten, is it possible, given a target temperature, to create an alloy (or compound) composition that has a direct (say eutectic) transformation to liquid at +/- one degree of the target temperature?

If yes, is there a method for identifying the elements to use based on the target temperature?


texts: Origin of different colour for thio analogue of indigo from blue to red

texts: Why the thio analogue of indigo is red? What is the reason behind change of colour from indigo to red just by change of N to S. What I get is that there will be electronegativity, lone pair availability, MO energy factors playing here but I am not getting exact answer.