texts: Calculating the mass of acceptable carbon monoxide in a room

texts:
The acceptable concentration of $\ce{CO}$ in the air is $10\:\mathrm{mg/m}^3$. In
  a room that is $19\:\mathrm{m\times4.0\:m\times25\:m}$, what is the acceptable mass in
  kilograms of $\ce{CO}$?

The room has a volume of $1900\:\mathrm{m}^3$. Since there are $10\:\mathrm{mg}$ of $\ce{CO}$ per $\mathrm{m}^3$, there are $19000\:\mathrm{mg}$ of $\ce{CO}$ in this room. That’s $19\:\mathrm{kg}$.

But the book says the answer is $1.9 \times 10^{-2}\:\mathrm{kg}$. How come?


texts: What are the chemical process responsible for the warping of wood?

texts:
Background:

According to this Wikipedia article:

  Wood warping costs the wood industry in the U.S. millions of dollars per year. Straight wood boards that leave a cutting facility sometimes arrive at the store yard warped. This little-understood process is finally being looked at in a serious way. Although wood warping has been studied for years, the warping control model for manufacturing composite wood hasn't been updated for about 40 years.

Factors contributing to the warping of wood include plant species, temperature and temperature changes, humidity and humidity changes and wet-dry cycles.

Discussion:

I'm not interested in which species are more prone to warping, how to prevent warping by treatments, etc. Nor am I interested in the biological processes of living or freshly cut wood. I'm interested in the processes happening over time on a molecular level that lead to macro-scale warping of wood. Water, in particular, seems to play a major role in the warping of wood, implying that possibly the lignin and cellulose matrix of wood is disturbed by the formation of hydrogen bonds. But if this is the case, or whatever the case, why would the microscale effects not cancel out rather than causing macro scale warping in a particular direction? This may be more of a physical than a chemical question, however.

Question:

What are the chemical process responsible for the warping of processed (as opposed to living or freshly cut) wood?

Edit 1:
A link to an interesting and relevant video was given in a comment, in which several types of wood were placed in a chamber which was evacuated of air, then pressurized with ammonia gas. The video also gave a link to a patent for this process. The following is an excerpt from the patent:

  The rigidity of wood is the result of crosslinking between adjacent cellulose chains by water molecules which hydrogen bond between sites on adjacent cellulose chains. Anhydrous ammonia is extremely reactive with water, and it is believed that anhydrous ammonia scavengers water from wood, breaking the crosslinking between cellulose chains, and permitting the cellulose chains to slide, which renders the wood very flexible so that it can readily be bent or twisted. When the ammonia volatilizes from the treated wood, water vapor reestablishes crosslinking and rigidity.

The reason for this edit is to suggest that the disruption of hydrogen bonding between adjacent cellulose chains, when the wood is dried then rehydrated, for example, may also play a role in "natural" warping. I'm going to look into this more and I hope it gives somebody else a clue to a good answer.


texts:
Suppose I open the drinks cabinet, and pour some of the strong stuff into a saucepan.

Now the boiling point of ethanol is lower than water, so if I boil the mixture for a while, all the alcohol will surely evaporate long before the water does.

But how quickly does the alcohol evaporate? Is it all gone by the time the water starts to boil? Or does some remain unless you boil the mixture for a long time? (How long?) Or maybe the alcohol is gone by the time the mixture starts to get slightly warm?


texts: What are some of the canonical texts for polymers? Is materials science more related to polymers than chemical engineering?

texts:
I am a freshman in college. My major is chemical engineering. I would like some recommendations for a textbook that's an introduction to polymers.

I am wondering whether a major in materials science is more related to polymers than chemical engineering.


texts: Propagating uncertainty with the slope of a tangent line

texts:
I have done an experiment that found the initial reaction rate for a reaction that created gas in $\pu{kPa s^-1}$ by finding the slope of the tangent line at time = 0. How do I propagate uncertainty for this? Is there any uncertainty propagation that has to be done?
$$\text{slope} = \frac{\pu{(99.726 ± 0.01) kPa} - \pu{(99.71753 ± 0.01) kPa}}{\pu{0.076 s} - \pu{0.061 s}} = \pu{0.56 ± 0.02 kPa s^-1}$$
This is what I have so far. My teacher said that the error for the time was so small that it is negligible (but not a perfect number). I do not think using percentage uncertainty would make sense here because you could measure the slope with however big or small numbers you wanted, depending on what two points you chose to use.
I got Vernier Logger Pro to do the tangent and slope calculations for me which is why there are more decimal places than uncertainty. Not rounding until the end. Is that wrong?
These are the instructions I was given:
only a simple treatment is required. For functions such as addition and subtraction, absolute uncertainties can be added; for multiplication, division and powers, percentage uncertainties can be added. If one uncertainty is much larger than the others, the approximate uncertainty in the calculated result can be taken as due to that quantity alone.


texts: Numbering starts from the side that has more locants or from the side that has a more preferable group?

texts:
I came across this question while practicing iupac nomenclature.

Should we number the parent chain from left to right (shown in blue) because there are three cholrine atoms attached to C1 while there are only two alcohol groups attached to C2?

Or should we start the numbering from the right side instead (shown in orange) as alcohol group is preferred over the chlorine group?


texts: Why do certain signals in proton NMR experience extensive splitting despite only having 1 neighbour?

texts:
I came across the compound 3-methylpentan-2-ol. Looking at its proton NMR spectra, it seems there is a lot of splitting for the signal at 4 ppm.

I'm assuming that the 4 ppm represents the proton in the hydroxyl group (since it clearly is much more deshielded than the other protons), but this would mean it only has one neighbouring hydrogen and hence should exist as a doublet.

I just wanted to clarify, is there any reason why the 4 ppm peak has so much splitting despite only having one neighbour? Or otherwise, I have also considered, could I be incorrect in assuming the 4 ppm peak represents the hydroxyl group, and if so why?


texts: Calcium reactivity vs electronic configuration

texts: Calcium is an alkaline earth metal, so it is reactive. But, it has two valence electrons. Don't those two electrons fill up the first energy level? Isn't an atom with a full energy level considered stable? Why is it reactive then?


texts: Why are hydrides of transition metals called hydrogen-deficient?

texts:
My textbook states:

Metallic hydrides are formed by many d- and f-block elements. Unlike saline hydrides, they are almost always non-stoichiometric, being deficient in hydrogen, for example, LaH$_{2.87}$, YbH$_{2.55}$, etc.

After some research online, I found that non-stoichiometric compounds are so called because they don't follow the law of definite proportions, that is, "their elemental composition cannot be represented by a ratio of well-defined natural numbers."
From what I understand, some transition metals form hydrogen bonds with H atoms that fill interstitial spaces between metal atoms in crystal lattices. However, what does "hydrogen-deficient" mean in this context? Apologies if this is an elementary question, but I could not find an answer online.


texts: Do electrons have some volume, area or shape?

texts: I am in 8th grade now and when I was in 6th grade, my science book had diagrams of the electronic configuration of atoms. The electrons were round like spherical balls. Is it true that the electrons have some volume, area or shape and they revolve around the nucleus?


texts: Equation to find specific gravity (or density) from a solution of sugar and water

texts:
Is there an equation or simple way to calculate the final density of a solution made from x grams of sugar and y liters of water?

And would it work in reverse? if we have y liters of water at z density or specific gravity, can we know how much sugar is in the solution?

I'd like to run an experiment for my nephews, something like This.

However, lacking any background in chemistry, the precise math is tough to nail down. It would be great to have some deeper understanding of how this works...


texts: I'm removing an above-ground chlorine pool installed years ago by a previous owner of my house. Looking underneath the pool, I found that the sand on which it's resting is a gold/bronze color with a metallic sheen to it. The pool itself is steel, with patches of rust. Does anyone have any ideas about how the sand might have turned metallic? I'm doubtful that it started off that way, as no above-ground pool retailers I've contacted have ever heard of such a thing. Thanks!


texts: Thought Experiment: Is it possible to preserve the charge imbalance present during molten lead(II) bromide electrolysis?

texts:
Suppose I were to electrolyse some molten lead(II) bromide. According to what I have been taught, the lead ions travel towards the cathode and are reduced at it, while the bromide ions are oxidised at the anode. The movement of the ions creates a charge imbalance (there will be more lead ions near the cathode and vice versa) in the molten fluid.

Suppose I were to let this run for a little while in a vacuum (and siphoning off the $\ce{Br2}$ as soon as it is produced) and non-conducting container. Now suppose I was to quickly put an impermeable non-conducting plate between the cathode and the anode and at the same time remove both the cathode and anode, so separating the molten $\ce{PbBr2}$ into two halves. This will stop the electrolysis but there is already a charge imbalance between the two halves (e.g. the half which originally had the cathode has more $\ce{Pb^2+}$ than $\ce{Br-}$) which has no way to correct itself.

If I cooled down both halves of the mixture now so that they both solidified there would be excess ions on both side which wouldn't be able to recombine. It might even be possible to remove the re-formed $\ce{PbBr2}$ by some method and have just the uncombined ions left on each side. My question is whether this is even possible, and if so what would happen next.


texts: Why in molybdenum disulfide the oxidation state of Mo is IV?

texts:
On one hand, stoichiometrically, it makes sense that in $\ce{MoS2}$ the $\ce{Mo}$ would have +4 and each sulfur would have -2.

(source)

However, in reality, every $\ce{Mo}$ atom is bonded to 6 sulfur atoms and every $\ce{S}$ atom is bonded to 3 $\ce{Mo}$ atoms. Why in such a complex configuration is it still correct to assign such oxidation numbers? $\ce{Mo}$ participates in 6 bonds, so how are they translated into an oxidation state of 4?


texts: Specific reduction of certain functional groups

texts:
Consider the compound $\ce{Alkyl-(4 oxocyclopent-2-ene)carboxylate (A)}$. For example consider-

  Now consider the operations:

  $\ce{1. (A) + (i)BH3/THF (ii) H+}$

  $\ce{2. (A) + H2/Pt}$

  $\ce{3. (A) + H2/Pd-C}$

  Products

  In $1.$ ester group reduced to an alcohol.

  In $2.$ double bond reduced to a single bond, and

  In $3.$ double bond reduced to a single bond, ester group reduced to an alcohol.

However, on the next page addition of $\ce{(i)BH3/THF (ii) H+}$ selectively reduced carboxylic acid when both ester and carboxylic acid were present.

My questions:

$(i)$ I know that $\ce{(i)BH3/THF (ii) H+}$ can reduce carboxylic acid, but I am unaware if it can reduce ester.

$(ii)$ I only knew that, the reduction of ester in presence of carbonyl group could be done by first protecting the carbonyl group (converting it to cyclic ketal by reacting with ethylene glycol) and then using $\ce{LiAlH4}$. Is reaction $3.$ correct?

$(iii)$ Why aren't product $2.$ and $3.$ same? I've always seen the two work same.

Note:

My chemistry teacher gave me few notes for Chemistry Olympiad preparation, so I can not cite source. I don't know how to make compounds, so will completely reside on IUPAC nomenclature.


texts: We were trying the litmus paper test and we found out that tea is acidic. So the question came in my mind and my science teacher could not give me any satisfactory answer: what acids are found in tea?


texts: How to compare the bond lengths of an peroxide complex before and after oxidation?

texts:
The complex $\ce{K6[(CN)5Co-O-O-Co(CN)5]}$ is oxidised by bromine into $\ce{K5[(CN)5Co-O-O-Co(CN)5]}$.

In this we have to comment on the change on length of $\ce{O–O}$.

But for that we have to find the oxidation number of $\ce{O2}$, so that we can know bond order.

But I am confused, how can I find the oxidation number?


texts: What is the most compact way to store Oxygen? Perhaps I should qualify that as being at room temperature since the most compact form of oxygen is probably liquid oxygen. At room temperature would it be better to store it as rust or compressed air or something else, like hydrogen peroxide?


texts: What type of compound/element might be in these glowing tiles

texts:
I saw these tiles and these as well while surfing the net, they obiviously glow when their electrons are exited to a higher state and then de-exite over a long period to give off visible light.

My question is which chemical might get exited by visible light and them emit back visible light for a long time.


texts:
Why is trans-4-phenylcyclohexane-1-carboxylic acid a stronger acid than the cis isomer?

In the cis-isomer the carboxyl group is axial; and, given the 1,4 distance from the phenyl, why would solvation be any more difficult?


texts:
I am quoting Clayden et al 2nd edition:

The sample is irridiated with a short pulse of radio-frequency energy. This disturbs the equilibrium balance between the two energy levels: some nuclei absorb the energy and are promoted to a higher energy level.

When the pulse finishes, the radiation given out as the nuclei fall back down to the lower energy level is detected using what is basically a sophisticated radio receiver.

Now, my confusion is about the equilibrium of nuclei in higher & lower energy level , after the introduction of radio wave.
Are the nuclei in higher level steady i.e. not radiating and coming back to the lower level constantly?
Or, are they radiating and constantly re-energized by the radio wave till the radio wave is on(still keeping a equilibrium constant between nuclei in lower and higher energy level)?


texts: I need to store small amounts of gas. I already saw devices that look similar to the image below, but I don't know how they are called. Does someone here know how these devices are called? I am also open for alternative ideas. I mainly need some kind of storing devices that works with low pressure and that is capable of pushing the gas back if pressure is removed. A ballon for example wouldnt work since it requires to much force to get the gas inside. It would be awesome if someone here know more and can help me with this.


texts: Will all thermodynamic equations have a linear dependence with moles?

texts:
I'm taking chemical thermodynamics this semester, and currently seeing things like the Maxwell's Relations.

My professor never uses explicitly the variable "n" and always works with molar quantities like $\bar{V}$ and stuff like that.

I think this simplifies the algebra a great deal, and can be useful if you have the temptation to get a "molar quantity". However, I don't like it right now.

I think theres nothing that can assure me that if I were to work with the variable $n$ in my derivations, I won't somehow get a quadratic dependence of my thermodynamic equation with $n$, or logarithmic, who knows.

But it seems that there is always a linear dependence with $n$. This makes physical sense to me, however, how can I prove this to myself? Maybe this is more of a question of mathematics, but it has scientific implications as well.

Thanks.


texts: Enantioselective alkylation of Aldehydes by Dialkylzinc reagents

texts:
Enantioselective catalysis is one of the important reactions in Organic chemistry which has huge applications in practical  basis for synthesis of optically pure natural compounds. In this respect, I came across the following reaction of Aldehydes aimed towards converting them into Chiral alcohol with large enantiomeric excess with the help of (-)-3-exo-(dimethylamino)isoborneol
[( -)-DAIB] catalyst.

The structure of (-)-DAIB is given as below,

The reaction is given as,

If we slightly rotate the molecule and visualise, we will see that here the methyl group has come from the top side of the molecule,i.e. a si-face attack by methyl group on benzaldehyde has occured.  From the picture of the transition state also this picture become clear,( According to our reaction $\ce{R''}$ is methyl and $\ce{R'}$ is Phenyl in the picture)

But my question comes here, Why the orientation of the bigger group (here Phenyl) in the transition state is preferably axial? Shouldn't it be the opposite direction,i.e. shouldn't the preferred orientation be that transition state where the $\ce{R'}$ and $\ce{H}$ are just swapped with this picture ? In that case $\ce{R'}$ is farthest from $\ce{R''}$ and logically should be the most stable transition state. So, the major product will just be the enantiomer of the originally given product. I am unable to find any flaw in this logical approach. Then, why is the transition state is the given one not the proposed one ?

References: -

Soai, K.; Niwa, S. Enantioselective addition of organozinc reagents to
aldehydes. Chem. Rev. 1992, 92, 833-856.;
Noyori, R.; Kitamura, M. Enantioselective Addition of  Organometallic  Reagents to Carbonyl  Compounds: Chirality Transfer, Multiplication, and Amplification.Angew. Chem. Ini. Ed. Engl. 30 (1991) 49-69
Itsuno, S; and Frechet, J.M.J.  Enantioselective addition of diethylzinc to aldehydes catalyzed by polymer-supported chiral amino alcohols. Evidence for a two zinc species mechanism. J. Org. Chem. 1987 52 (18), 4140-4142


texts:
What's the logic behind the following nomenclature: 3,4,5,6-tetrahydro-2H-pyran?

Why not simply 2,3,4,5,6-pentahydropyran? Isn't the hydrogenation of the heterocycle obvious by including hydro- prefix? Specifying 2H-pyran seems to be redundant, unless it carries information about which position was hydrogenated first (which isn't the case).


texts: Applying Raoult's Law to a condensed gas mixture

texts:
So, here's the question which I'm having trouble solving :

Suppose that we condense a gas mixture. At 25 celsius, what will be the pressure of benzene and of toluene over the obtained liquid.

We know that vapor pressures of pure benzene and pure toluene at 25 celsius are 12,7 kPa and 3,79 kPa respectively.  We also previously prepared a solution that has equal molar fraction of benzene and toluene. We had to determine the vapor pression of benzene and toluene. (this is an ideal solution)

This gave us:
 $$p_{benz}=x_{benz} * p^°_{benz}= 0.500 * 12.7 \text{ kPa} = 6,35 \text{ kPa}$$

$$P_{tol}=x_{tol} * p^°_{tol}= 0.500 * 3.79 = 1.90 \text{ kPa}$$
Total pressure: $P = 6.35 + 1.90 = 8.25 \text{kPa}$

Finally, there was another question which asked us what was the composition, in molar fraction, of the vapor in balance with the solution of benzene and toluene at 25 celsius.

This gave us
$$x_{benz} =p_{benz} /P_{total} = 6.35 / 8.25= 0.770$$

$$x_{tol} =p_{tol} /P_{total} = 1.90 / 8.25 = 0.230$$

By the way, here's the answer to my question :

$$p_{tol} = x_{tol} * p^°_{tol} = 0,770 × 3,79  = 2,91 \text{ kPa}$$

$$p_{benz} = x_{benz} * p^°_{tol} = 0,230 × 12,7  = 2,92 \text{ kPa}$$

So, where does the Xtol= 0.770 and Xbenz=0.230 come from ? Thank you


texts: Is it possible for this Iron-Carbon Compound to exist?

texts:
Can this compound be created?

Where the orange is Iron and the black is Carbon.


texts: Numerical on change in degree of dissociation wrt pressure

texts:
The degree of dissociation of $\ce{PCl5}$ is 0.4 at 2 atm pressure and T kelvin. At what pressure will degree of dissociation of $\ce{PCl5}$ be 0.6?

Taking the degree of dissociation as 0.4, I got the partial pressure of $\ce{PCl5}$ to be $\frac{2}{2.33}$. I then thought of taking the degree of dissociation as 0.6 and multiplying the mole fraction of $\ce{PCl5}$ with the total unknown pressure and equating it to the partial pressure of $\ce{PCl5}$. But I then realized that wouldn't the partial pressure change with change in total pressure?
I'm not able to figure this question out. Any help would be greatly appreciated!


texts: Stretching frequency of nitro and nitrito

texts:
I got the values of the stretching frequency of nitro and nitrito ligands from this webpage.
I understand why stretching frequencies are close in nitro and well separated in nitrito. How to explain why nitrito has slightly higher stretching frequency?


texts: Why are these ions classified as isoelectronic?

texts:
According to Chemistry the Central Science 13 Edition, these ions are isoelectronic:

$\ce{Ca^2+}$ (18 electrons); $\ce{Cs+}$ (54 electrons);  $\ce{Y^3+}$ (36 electrons)

Furthermore, the textbook states that the caesium ion is the largest.

Now, every definition I've looked up, including from the book, states that in an isoelectronic series, the atoms have the same number of electrons. Clearly, these don't. I have noticed, however, that they are in multiples of 18, where the Calcium ion is 18, and Caesium is 3 times 18, and Yttrium is 18 times 2.

A friend, who took chemistry 1 a few years ago, recalls that there was some formula (or something) to determine isoelectronic series.

I suspect that they have something to do with the electrons in their valence.

The book does not give an explanation. It moves on to ionization energy.

But it also states that of these three, caesium is the largest, which compounds my confusion since just a few lines up, the book states that the nuclear charge is inversely proportional to the ionic radius, so an increasing nuclear charge (atomic number) means a decreasing atomic radius. It would seem appropriate that the calcium ion has the largest ionic radius since it has the smallest nuclear charge.

Can anyone help?


texts:
I've been creating various Copper(II) complexes using different ligands and predicting their relative hues using Crystal Field Theory by using the spectrochemical series to predict the extent of d orbital splitting on the Copper(II) ion and the resultant colour of the copper(II) complex.

When I added potassium thiocyanate ($\ce{KSCN}$) to a solution containing hexaaquacopper(II) the entire solution turned deep black. Doing some research online and knowing that $\ce{SCN-}$ tends to form complexes with planar geometry I'm fairly certain that the resultant copper(II) complex was $\ce{[Cu(SCN)4]}$.

Because of the relative strength of the $\ce{SCN-}$ ligand compared to the pale blue complex formed with $\ce{H2O}$ I assumed the solution would appear redder in hue as higher frequency wavelengths would be absorbed, however, I fail to see why the entire visible spectrum would suddenly be absorbed. Can this phenomenon be explained with Crystal Field Theory?

Also perhaps my solution was not dilute enough?


texts: What's happening at the beginning of a weak acid titration?

texts:
At the beginning of a Weak Acid/Strong Base titration curve there is a sharp decrease in $[\ce{H+}]$ and a sharp increase in pH before the ratio between the weak acid and it's conjugate base becomes low enough that we have a buffer solution.

What's happening at that point?

My interpretation is that, given the balanced equation:

$$\ce{
CH3COOH~(aq) + H2O(~l) <=> CH3COO- ~(aq) + H3O+~(aq)
}$$

The addition of $\ce{OH-}$ would shift equilibrium to the left by Le Chatelier's principle making the newly generated $\ce{CH3COO-}$ react with $\ce{H3O+}$ to make more $\ce{CH3COOH}$, thereby increasing pH. After that, the $[\ce{H3O+}]$ is so low that the addition of the anion is not enough to keep shifting the equilibrium position to the left, so the remaining weak acid resists the changes in pH with its dissociation.

Does this make any sense?


texts: Role of THF in oxymercuration of alkenes

texts: I am trying to self learn solomon's organic chemistry book, but there is no explanation over why we should use THF in oxymercuration. After a quick search I found out that THF help stabilize in hydroboration, but is it the same for oxymercuration? and I still don't understand why and how THF can help stabilize in hydroboration.


texts: Chemical Equilibria - Fraction Bound equation based on Kd, [R], [L], [RL], is actually an average?

texts:
Let's say 150 stem cells express exactly 150 copies of the same mebrane antigen X. While all differentiated cells express exactly 15 copies of X. To the cell mixture you add a large amount of 0.2 μM solution of antibody to X. The $K_D=$ 4 μM.
If you experimentally analyze the number of antibodies bound per stem cell, you will find that it is not constant.  Explain why, even for cases where the number of antigens expressed is the same, the binding follows a binomial distribution?

I found the fraction bound to be $\frac{1}{\frac{K_D}{\left[L\right]}+1\:}=f_{bound}$

I scaled the [L] contribution by the number of antigens expressed per cell, so for the differentiated case, I scaled 0.2 μM by 15, and for the normal case, I scaled 0.2 μM by 150.
the differentiated case has a lower $f_{bound}$ because it has less ligands.

To describe the binomial distribution for binding part

the antigens exist in the environment of the beaker (or wherever the reaction is taking place) so they can exchange antigens? resulting in some cells $f_{bound}$ being lower. How exactly the interaction takes place occurs stochastically.  <--- want help clarifying this part


texts: How can a neutral atom attract electrons when it's supposed to have zero charge?

texts:
A neutral atom is an atom with an equal number of protons and electrons

We know the force of attraction between the proton and electron is equal
and assuming that:

one proton's positive charge attracts one electron.
The "neutral" in a neutral atom means electrically neutral.

How can a neutral atom attract electrons when it's supposed to have zero charge ?


texts: The Evasive Ether: Existence of diethynyl ether?

texts: I tried to find online whether the compound diethynyl ether, $\ce{HC#COC#CH}$, exists in a stable state at STP, mainly out of curiosity, but also because it would be interesting to study the properties of a molecule with such interesting characteristics (eg. the very long bent shape, the highly exposed oxygen atom, the potential for multiple different polymerization reactions). However, I spent about 30 minutes scrolling through page after page of search results with only results about diethyl ether, and came up empty-handed. I'm wondering if anyone here has any info/sources/knowledge about this evasive ether. I've included some images to clarify what molecule I'm talking about, as well as to possibly help jog your memory. Any and all information/data about the molecule is appreciated.


texts: Deuterated solvents vs. regular solvents

texts: Working on dissolving aspartame and i was wondering if it dissolves well in methanol will this mean that it dissolves well in deuterated methanol ?


texts: How do copper sulphate and the like change crystal structure on adding water of hydration?

texts:
Copper sulphate, in its hydrated form, is crystalline, whereas the anhydrous form is amorphous.

Gypsum has a similar story-- on heating the crystalline dihydrate we get an amorphous hemihydrate. (Gypsum in fact has two different crystalline forms of the dihydrate, and has an anhydrous form as well).

I've never really grasped how the water makes it crystalline. I suspect it has to do with the relative sizes of the compounds being re-compensated by ligands, but I'm not sure. How does the water affect/create the crystalline properties?


texts:
Working on a practice exam. The question is

  A volume of gas contains
  0.25 moles of $\ce{CO2}$
  0.30 moles of $\ce{N2}$
  0.15 moles of $\ce{O2}$

  What is the partial pressure of $\ce{O2}$ if the total pressure was $690\ \mathrm{mmHg}$ and the temperature was $25.0\ \mathrm{^\circ C}$

I know the formula is $p_a=\dfrac{n_aRT}{V}$

So far I know that

$n_a = 0.25\ \mathrm{mol}$

$R  = 0.0821\ \mathrm{l\ atm\ K^{−1}\ mol^{−1}}$

$T = 298\ \mathrm K$

But I can't seem to figure out volume. I was reading somewhere that volume is directly proportional to The amount of moles, but maybe it has something to do with the total pressure. I'm a little lost.

The only thing I can think of would be getting volume via the Ideal Gas Law as well. Would that work?


texts: Reaction of formic acid with bridged bicyclic compound

texts:
Write the mechanism for:

I've been able to add part of the product, but am having trouble with the ring formation. Here is my attempt:


texts:
What is the systematic name of this compound:

My try: 3-propylpentane.


texts: I'm currently working on a project using Iron(III) acetylacetonate, which in the wikipedia page it's written Tris(acetylacetonato)iron(III), and it says it's the IUPAC name, maybe it's obvious but I'm a little confused about the nomenclature, why acetylacetonato instead of acetylacetonate, couldn't it be Tris(acetylacetonate)iron(III)? Is one name better than the other?


texts: Why does a buffer work best at the pH closest to its pKa?

texts: I think I'm having trouble understanding exactly how the $\mathrm{p}K_\mathrm{a}$ relates here on a conceptual level. For example I know that carbonic acid works somewhat well as a buffer at $\mathrm{pH}$ near 7, since its $\mathrm{p}K_\mathrm{a}$ is relatively close, but why is that exactly?


texts: Dependence of the angle of rotation on the wavelength of plane polarized light

texts:
Wavelength difference is a big deal, I know. It can solely change the whole interaction between the chiral molecule & the light. But I am not sure what's the mechanism by which light of different wavelengths produces different angles of rotation.

So, why and how wavelength matters?


texts: Constitutional isomers of cis-1,2-dibromocyclopentane

texts:
The following is a problem from 'Fundamentals of Organic Chemistry' by McMurry-

  Draw two constitutional isomers of cis-1,2-dibromocyclopentane.

Constitutional isomers must have different connections. But the question specifies everything including the spatial arrangement. I don't get how there can be constitutional isomers for the above-mentioned compound.


texts: Why do some nucleophiles attack at the carbonyl group while others at an alpha-carbon in ketones?

texts: I was reading about the iodoform reaction and it stated that $\ce{OH^-}$ attacks at the $\alpha$-carbon and makes a substitution reaction possible. But there is also the possibility of attacking the carbonyl group directly and forming a gem-diol. Why doesn't that happen?


texts: In which pH range are silica-based TLC plates stable?

texts: I am trying to understand why the experiment asks for raising the pH of a fairly acidic solution. The analytes should not be affected by it, so I thought the silica plate might be. Are silica-plates vulnerable in acidic conditions and, if yes, what happens?


texts: What is the process of connecting two molecules under removal of one molecule of water?

texts:
Certain molecules can be joined by the removal of water in a process called:

Hydration.

Hydrolysis.

Neutralization.

Condensation.

I know that the process of hydration is defined as, "A compound produced by combining a substance chemically with water."
The process of hydrolysis is defined as, "The chemical breakdown of a compound due to reaction with water."
Neutralization is a chemical reaction in which an acid and a base react quantitatively with each other.
Condensation is the conversion of a vapor or gas to a liquid.
The answer is most likely (1), but I'd like some feedback and explanation of these definitions!


texts: Does a stoichiometric coefficient represent molecules or moles of a substance?

texts:
I understand that the one mole of atoms is equal to $6.02\times10^{23}$ atoms. However, when I used various resources to learn about stoichiometry, they showed me a balanced equation:

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

and said "2 moles of water" decomposed to form "2 moles of molecular hydrogen" and "1 mole of molecular oxygen". It is my understanding that there are only 2 molecules of water, not $2 \times 6.02 \times 10^{23}$ molecules of water and so on with the other parts of the equation as well. Could someone please clear up my confusion?


texts: What is the link between hydrogen production and potassium oxide?

texts:
Is there an industrial process that produces hydrogen with potassium oxide as a catalyst?

Or is there a process for the production of potassium oxide that has hydrogen as a by-product?


texts: Lines on inside of hexagonal shapes of structure diagrams

texts:
just a simple question from me today...

I was looking at the structure of Norepinephrine for a school project and was curious about the diagrams on the Wikipedia page for it.

I was wondering why hexagons are used in this diagram and what the purpose of the three lines on the inside of the hexagon mean.


texts: Mechanism for ring contraction from 2-methylenecyclobutanol to 1-methylcyclopropanecarbaldehyde

texts: I am stuck between two paths. I was going to protonate the alcohol to give a better leaving group, leaving a 2 degree carbocation and then go on with a hydride shift. But, I'm not sure what that may turn out to look like, and when exactly the ring is supposed to contract. Or, I was going to have the alkene attack the acid, but after that I wouldn't know what to do with the alcohol.


texts: Why is imidazole considered an electron deficient heterocycle?

texts:
A paper I'm looking at1 mentions a few electron deficient heterocycles:

  electron deficient heterocyclic compounds such as di(azines), benzothiazole and imidazole...

What are the criteria to determine whether a heterocycle is electron deficient or not? (Why is imidazole considered electron deficient, for example?)

Reference

(1) Bureš, F. Fundamental aspects of property tuning in push–pull molecules. RSC Adv. 2014, 4 (102), 58826–58851. DOI: 10.1039/C4RA11264D.


texts: Is there a known chemical that makes it possible to control the opacity of a large surface?

texts:
I have this idea of creating a large domed ceiling/roof for a building that can be made clear to see the actual sky, or made fully opaque/dark grey/black to project an artificial sky onto.

I know that things similar to this effect have been chemically achieved such as UV-activated sun glasses and remote controlled window tint, but I haven't been able to find much information that explains how this kind of thing is done chemically.

What options, chemically speaking, exist for making a large glass surface transform between being clear and opaque?

I'm looking for any known chemical that can do this in the form of a tint applied to a glass surface, or a liquid filling a hollow glass surface, or even a gas filling a hollow glass surface.

To be absolutely specific, I'm describing a chemical that can be either modified or added/removed to/from/within a glass surface to systematically control nearly full opacity or nearly full clarity of a layer applied to or contained within the surface of a curved glass panel.

Note: The opacity transition should be efficiently repeatable, meaning, the effect shouldn't deteriorate significantly with repetition.


texts: Calculating the Presence of Anthocyanin in a Solution

texts:
I've produced a red cabbage solution (boiling red cabbage in water basically), and would like to calculate the concentration of the red cabbage/anthocyanin in the solution. How is this accomplished?

Thanks


texts: What molecules can be eliminated in condensation polymerization?

texts: Is there any specific rule to what kind of molecules can be eliminated in condensation polymerization? From Wikipedia I found that "small molecules" like $\ce{H2O}$ can be eliminated. Is there a more accurate criteria to what these "small moecules" are?


texts: Can acidic conditions break disulfide bonds

texts:
I am denaturing a protein using organic solvent and acid (49:49:2% water:methanol:acetic acid), but I want to maintain the disulfide bonds.

My chemistry knowledge isn't good but disulfides are broken under reducing conditions and the reaction also uses free protons:

So I wanted to check if acids could break disulfide bonds without reducing conditions.


texts: Aren't hydrogens on less substituted groups more electrophilic?

texts:
I am having some trouble understanding the behaviors of some Alkene reactions that I have been studying. I took two semesters of O-chem a couple of years ago and am trying to refresh before an advanced class, but I have found two reactions in my studies that aren't making sense.

At the top of page 13 of the e-book found here: http://crab.rutgers.edu/~alroche/Ch08.pdf ... I see that the water molecule is attacking the carbon with two methyl groups on it... but wouldn't the carbon with only one methyl group be more electrophyllic? Because of induction, I would think that the carbon with two methyl groups would be more stable than the other, and so the carbon with less substituents would be more electron-poor.... So why does the water attack the more substituted carbon?

Secondly, in the image below (sorry it's turned), where the second proton transfer is taking place, you see the water molecule pulling the hydrogen off of the more substituted carbon. But wouldn't the hydrogens on the methyl group adjacent to the positive charge be way more electrophyllic, thus creating a double bond on the end of the chain?

I appreciate any help on this. Thanks for your time and effort!


texts: What is the structure of [Co(NH3)5SO4]+?

texts: What is the structure of $\ce{[Co(NH3)5SO4]+}$? If sulfate is a bidentate ligand, then the coordination number of cobalt would become 7. How is this possible?


texts:
The pKa of carbidopa is 7-8 of the base hydrazin. Is this because of the zwitter form with the acid? Why is the basicity so low? If it can form a zwitter ion wouldnt  the pKa be higher?

https://en.wikipedia.org/wiki/Carbidopa


texts:
I wonder what's the exact meaning of throughput in chemistry synthesis, eg. in organic synthesis or production of pharmaceutical products. For instance, what are their units? How are they measured?
I've read one paper mentioning their production methods have a high throughput and production rate (https://pubs.rsc.org/en/content/articlelanding/2013/sc/c3sc50859e#!divAbstract).
Are these two concepts the same thing?
Share with me your thoughts. Thanks a lot!


texts:
I have recently performed an experiment in which I tested the affects of phytotoxic cations on the rate of germination of the common navy bean. I did this out of  curiosity, as I have recently been researching arsenic (III) and arsenic (V) mobility in water systems, and I wanted to know weather or not it was the mobility of the ion or its general toxicity to a cell that is more influential on the overall phytotocicity. Generally, arsenic (III) is much more toxic due to the fact that it is so mobile while arsenic (V) is less toxic due to the fact that it is less mobile. After testing the oxygen usage in each of my different germination environments, I was quite surprised at the results. I had placed 100 navy beans in 1 molar solutions of copper, lead, iron, and cobalt chloride (the lead chloride may have been a little under 1 M, as it is not very soluble in water); in each of these solutions, I let these beans germinate for 12 hours and then tested the oxygen output of each sample. Here were my results:

I did not think the mobility of these ions would have such an effect, as I know lead is less mobile than other cations in water systems; however, my major problem is interpreting the top three results, all of which gave fairly similar results. I am having trouble figuring out where this result is coming from. I know that all of the ions are phytotocic to some degree, and I would expect all of the ions to have a detrimental affect on the germination of the seeds. Is it more likely that these findings are the result of the phytotocicity of the ions or the mobility of the cations across the cellular membrane?


texts: Most efficient level of theory for sulfur-containing proline analogues (one that will work)

texts:
I'm modelling a small set of proline analogues - extra functional groups, sulfur in the ring. Using Gaussian / DMACRYS.

--functional B3LYP EmpiricalDispersion=GD3BJ --basis_set 6-311G**

or

-fun B3LYP EmpiricalDispersion=GD3BJ -bas 6-311G**

Would EmpiricalDispersion=GD3BJ go under -fun, or would it go under --additional_args? (If so, please show how, I can't get this to run correctly, unsure of the syntax)
To model this more accurately, PBEPBE has been suggested, pure DFT rather than hybrid functional, so there is increased accuracy. Is there a sufficient increase in accuracy for the increase in computational time, or is it better to apply dispersion corrections to B3LYP? (Or PBEPBE and corrections?) Is there another level of theory you would suggest trying?
The electrostatic interactions seem to be over-modelled using B3LYP / 6-311G**, is there a basis set / functional combination (without or with corrections) that would not over-estimate the energy of the + / - charge interactions? (I've tried CAM-B3LYP, but doesn't work on my system.)


texts:
Substituted phenols or polyhydroxy phenols have their general name apart form IUPAC names. The general names comes from the source it is found like:-

Catechol (1,2-dihydroxybenzene)- obtained from catechu
Cresol (methylphenol) - obtained from creosote, a component of coal tar
Gallol (1,2,3-Trihydroxybenzene) - synthesized from gallic acid which is obtained from  oak galls, not a compound of gallium which many people get confused.

But what about resorcinol? Why is it named so? Is it resourceful? It is primarily obtained from argan oil. So, it should be named as arganol. But it is not so.

Same thing happens with phloroglucinol. Various sources are there but none of them matches with the general name.


texts:
My textbook mentions that:

  Iron is unable to be totally reduced... the most common non-zero oxidation states of iron is (o for oxidation, r for reduction) are: +2r, +3, +4o, +5o, +6o.

I thought it maybe meant going to $\ce{Fe^4+}$ (as the most reduced I commonly see is $\ce{Fe^3+}$), but then upon googling there is also $\ce{Fe^5+}$ ions, so how far does it have to go until it is totally reduced (if this is even what it meant by totally reduced)? Edit: Sorry, got reduction and oxidation mixed up (thanks for pointing this out DVSA). However, my question still stands, though replacing the above with more to e.g.  $\ce{Fe^4-}$ than  $\ce{Fe^3-}$  .

The question, for context, is below (I have already typed up what I think are the relevant parts above). FYI the answer is D, but I want to know what B means.


texts: Solubility product constant of copper(II) bromide in water

texts:
One of the questions from chegg.com mentions $K_\mathrm{sp}(\ce{CuBr2}) = 6.3\cdot 10^{-10}$, but I suspect this value might be incorrect.

Could anyone confirm or refute that $K_\mathrm{sp}$ value?

For CuBr I found Ksp values of 6.3x 10-9 and 4.0x 10-8 which is around that range. One explanation would be that the website would have wrongly attributed the Ksp of CuBr to CuBr2.

I wish Springers had the exact same paper for CuBr2, that would be just perfect. It's a solid source for the CuBr dat

As Ivan points out, wikipedia lists the solubility of CuBr2 in water as 55.7 g/100 mL (20 °C), but without listing any source. Though this value is more likely to be correct, I'm still stuck between two undocumented values that aren't close to indicating the same thing.

Buttonwood shared the link to a paper regarding CuBr which is a solid source as to it's solubility. Anything regarding CuBr2 even close to being that good would be perfect!


texts: What were the expectations of Rutherford's gold foil experiment?

texts:
At the time when Rutherford's gold foil experiment was performed, Thomson's plum pudding model was believed to be true (at least by Rutherford himself and his students).
With this model in mind Rutherford predicted that most of the alpha particles will be deflected by at most a fraction of a degree (sourced by this Wikipedia page), but why?
In my opinion, since according to the plum pudding model the mass of an atom was assumed to be uniformly distributed and the atomic mass of gold is nearly 50 times larger than the mass of an alpha particle, and gold is solid, therefore much less intermolecular space will be present, so, most of the alpha particles should rebound or get deflected by a large angle.
Help me improve my opinion.


texts:
In other site, someone claimed that pure water is very corrosive.

Water distilled for some laboratory uses (like the Z-pinch reactor) is distilled to 0.00000009% purity, and is caustic enough to burn through most things.
Water, purified enough, cannot be distributed through stainless steel pipes. Instead, they use glass pipes to transport it within the plants where it's made.

For sure, caustic is not the correct word, since water is neutral.
But, is it that corrosive? Or is it even less than water with salt?


texts: How can I convert the number of particles per liter to gram per liter? I know the size of these particle and so, I calculated the volume and then by the density I calculate the mass. After that I don't know what to do


texts: Bond orders in the 3c-4e bond and 3c-2e bond

texts: According to D. P. M. Mingos, in his book Essential Trends in Inorganic Chemistry, the bond order of the three-centre four-electron bond is approximately 0.717, which is one divided by the square root of 2. However, in the case of the three-centre two-electron bond, the bond order is 0.5. This would imply that the former is stronger than the latter. However, both of them have similar-looking molecular orbital diagrams. In the case of the former, the nonbonding MO is filled while in the case of the latter, only the bonding MO is filled. Thus, from the MO perspective, why would these two bonds have different bond orders?


texts: deduce chemical properties of a compound from elements

texts:
If we know the properties of two elements e.g Oxygen and Hydrogen.

We know the following properties

sound speed
boiling point
melting point
refractive index
etc.

given that information, is it possible to deduce the properties of a compound such as water H2O without resorting to chemical experiments? i.e deduce its boiling point


texts:
Wikipedia states:

  Strontium peroxide is produced by passing oxygen over heated strontium oxide. Upon heating in the absence of $\ce{O2}$, it degrades to $\ce{SrO}$ and $\ce{O2}$.

I found some literature about what temperature is needed but I did not find any literature about the condition of oxygen pressure. If I do annealing of $\ce{SrO}$ at $\pu{800 ^\circ C}$ in $\pu{0.5 atm}$ oxygen, will I form $\ce{SrO2}$?


texts: Why might a planar, conjugated molecule be higher in energy than a nonplanar system?

texts:
I have a small molecule (23 atoms) for which I want to verify parameters in a molecular mechanics force field.

My first step is to look at the potential energy as a function of the dihedral angle, defined by these four atoms:

The results for the dihedral scan, rotating the guanidino tail from 0 to 360 degrees in increments of 5, looks like this:

Alright, something is funky around the 0 and 180 degree structures. Honing in on 180, and performing a QM scan with increments of every 0.1 degrees, I see this:

There is a gap between 177.1-178.2 and between 181.5-182.6, where the QM optimization failed. Checking the plateau and either side of the plateau, what I find is that the plateau structures are all planar, whereas on either side of the plateau, some hydrogens come out of the plane (consistent on both sides of the plateau). For example, this is an overlay of two structures: blue = 178.2° = planar = higher energy. Red = 177.1° = nonplanar Hs = lower in energy. (front view and bottom side view)

Let's assume that the QM calculations are to be trusted (this was run using a few different levels of theory). A mere 1° causes this shift between planarity and nonplanarity. Intuitively, if we think about the ring system being the same in both cases, this makes no sense, as a planar molecule should be better conjugated and thus lower in energy, correct? What other factors might account for this phenomenon?


texts:
I made nylon in a lab with these procedures -

1) Collect 30mL of sebacoyl Chloride dissolved in hexane

2) collect 30mL of 1,6-hexanediamine dissolved in water .

3) Transfer the beaker containing sebacoyl Chloride in hexane and carefully pour the solution down the side of the beaker containing 1,6-hexanediamine in water , such that the hexane layer floats on TOP of the water layer , without mixing the layers.,

I got these procedures from the Internet .

Now , I got a few doubts and questions ..

In the past , dichloromethane was used as the Solvent for the sebacoyl Chloride reagent. However dichloromethane is not environmentally friendly solvent and hexane was chosen to replace it in the experiment ...

a) how does switching it to hexane change the experimental procedures ?

b) What physical and chemical properties of the Solent must be considered when switching ?

c) why is hexane a good alternative in this experiment ?

Thanks in advance !


texts: Is this the NMR spectrum of 3-methyl-1-butanol?

texts: It is a $\ce{^1H}$-NMR spectrum and I think the signal near 3,61 ppm is the CH2 group next to the hydroxy group. But which signal is the hydroxy group and which protons are in the multiplet?


texts: Conversion of benzenediazonium chloride to benzene using lithium aluminium hydride

texts:
Why does benzenediazonium chloride get converted to benzene upon
reacting with $\ce{H3PO2}$ and not $\ce{LiAlH4}$ ?
Also, what is the reaction mechanism of the reaction with $\ce{H3PO2}$
?

This Wikipedia page list all kind of nucleophilic substitution reaction on aromatic compound why can't $\ce{LiAlH4}$ / $\ce{H-}$ react like one of these to give benzene and expel nitrogen.
I just wanted to add that it's up to my knowledge that $\ce{LiAlH4 / H-}$ can't reduce the double bond of Benzene, because when styrene reacts with $\ce{LiAlH4 / H-}$ it gives ethyl benzene.

Update
I was just researching (on google) for the mechanism where I came across this site suggesting the mechanism to be radical and as follow :

But still there is one problem the side products don't match this site states the side product to be $\ce{H3PO3}$ and $\ce{HCl}$ but as stated above the side products must be $\ce{H2PXO2}$.


texts: Effects on Stretching Frequencies in Organometallic Complexes

texts:
If you added a negative charge to $\ce{Mo(CO)_6}$ how would this effect the $\ce{CO}$ stretching frequency in an IR spectrum?

My thoughts are that it would lower the $\ce{CO}$ stretching frequency because the metal would be able to donate electron density to the $\pi^*$ orbitals of $\ce{CO}$. Does this reasoning sound plausible?


texts: Confusion in unit cells of crystal system

texts:
Unit cells are divided into two main types

Primitive
Non-primitive

Primitive includes simple cubic lattice whereas non-primitive includes fcc bcc end centered..

Among the seven types of crystal systems orthorhomic crystal system posses both primitive as well as non-primitive unit cells i.e. face centred body centred rnd centred and simple cubic but the cubic system posses primitive , body centred and face centred arrangements only.

My question is if face centred is possible in cubic system why is not end centred type of unit cell arrangement possible in cubic system if there is no sort of hindrance in vacant space as in orthorhombic which posses all types of unit cell arrangements.


texts:
Definition

The ortho position refers to the two adjacent positions on a benzene ring.

The meta position refers to the positions separated by one carbon atom on a benzene ring.

The para position refers to the opposite position (separated by two carbon atoms) on a benzene ring.

Background

The dictionary.com pages for ortho, meta, and para state that they are independent from the prefixes ortho- (correct), meta- (after; beyond; a higher level), para- (alongside) respectively.

However, I suspect that the meta position is just after the ortho position, so it is named meta ("after" in Greek).

Question

How did these words become affiliated with the positions on a benzene ring?


texts:
I have noticed that if you put household or other chemicals in bin liners or freezer bags the plastic doesn't keep the chemicals in. Rather they travel through the bag material and out into the air. However I have noticed that some bin liners have stronger material and are better than others.

Perhaps it will depend on which chemical is in the bag. However I guess I am asking about pollen, pesticides,washing detergent and general cleaning chemicals.

Is there a specific type/grade of plastic bin liners that I can get that will, generally speaking. keep odors in? Actually it doesn't have to be pvc any bag material which does the job will do however I guess PVC bags are most easily accessible so would like to know what options there are. See through bags are preferable.


texts: What's the hybridization in diphosphorus molecule?

texts:
I read that diphosphorus has 2 phosphorus atoms joined by a triple bond (ie) it has one sigma bond and 2 pi bonds with 2 lone pairs ( 1 lone pair on each atom). I'm confused about the hybridization of the orbitals. Phosphorus in excited state has one 3s orbital, three 3p orbitals and one d orbital .

If sp2 hybridization takes place, it will form one sigma bond and what about the other 2 hybridized orbitals what would become of them? I'm confused on the lone pair part :/

If the above even took place, would the unhybridized p orbital form pi bond with the unhybridized p orbital of the other phosphorus. And the same would go for the 2 d orbitals. Am I correct on this??

note :https://socratic.org/questions/does-nitrogen-n2-and-oxygen-o2-goes-through-hybridization-how-can-i-know-when-hy

Here it says that "Diatomic molecules don't need hybridisation that is phosphorus would be using p pi p pi bonding which it could never do cuz of large diffuse orbitals !!


texts:
We have to compare melting points of $\ce{LiH}$, $\ce{NaH}$, $\ce{KH}$, $\ce{CsH}$. I know the melting point of an ionic compound is more than that of a covalent compound.

So according to Fajan's rule, ionic character increases in $\ce{LiH}$, $\ce{NaH}$, $\ce{KH}$, $\ce{CsH}$. As ionic character increases, melting point should also increase in $\ce{LiH}$, $\ce{NaH}$, $\ce{KH}$, $\ce{CsH}$.

But actually, the melting point decreases in $\ce{LiH}$, $\ce{NaH}$, $\ce{KH}$, $\ce{CsH}$. What could be the reason behind this?


texts: Why is negative charge more stable on sulphur than on oxygen?

texts:
Consider this problem:

Which is more acidic, $\ce{MeOH}$ or $\ce{MeSH}$?

According to my teacher:

To determine which is more acidic, figure out which forms the more stable conjugate base. In this case, $\ce{MeS-}$ is more stable than $\ce{MeO-}$. In general stability reduces in the order: $$\ce{RS- > RP- > RO- > RN- > RC-}$$

Why is the compound with $\ce{S-}$ or $\ce{P-}$ more stable than that with $\ce{O-}$? I know that oxygen is more electronegative than either sulphur or phosphorus. Shouldn't the descending order start with $\ce{RO-}$?


texts: Semi-Infinite Potential Square Well: Negative Potential

texts:
I am having trouble with a problem involving a Semi-infinite potential square well:

I have written down some notes that I added to the post. I have problems understanding the physical situation. See the figure in the notes. When the potential is just shifted upwards, so that the $V(x)=0$ region is $0<x<a$, I have no trouble understanding the solution. However, I am just really confused about the negative potential.

As you will see in the notes, I have interpreted Region I as a bound state (e.g. an electron bound to a proton). Region II, I believe, is the free state (e.g. "bound" electron in energy level $n=\infty$), since $V(x) = 0$.  Is this correct?

I face some troubles with the boundary conditions, as one of my wave-functions simply disappear!


texts: Solubility of N-[(4-hydroxy-3-methoxyphenyl)methyl]acetamide at different pH

texts:
The molecule below is a simplified analog of capsaicin. Explain in which of the following options, it should be most soluble:

  aqueous HCl (pH = 1)
  aqueous NaOH (pH = 14)
  pure water (pH = 7)

  N-[(4-hydroxy-3-methoxyphenyl)methyl]acetamide, National Center for Biotechnology Information. PubChem Compound Database; CID=606880

I chose aqueous NaOH, because then the molecule will be completely deprotonated, which will make it more soluble. Please tell me if this is correct.


texts: Difference between tendency of benzene and thiophene to undergo sulfonation

texts: Why does thiophene possess a greater tendency to undergo sulphonation than benzene? I came across this reaction which employs the use of sulphuric acid to separate thiophene from commercially prepared benzene.


texts: When a liquid (in my case I used butane) under high pressure is released into the air, it becomes gaseous, and the container seems to get colder. Why is it that turning a liquid to a gas requires energy when it was simply pressure that was keeping it a liquid? Where does it get this energy? Would the gas formed be colder, or no?


texts:
Haloalkanes aren't very soluble in water because they can't form hydrogen bonds, and the energy required to break hydrogen bonds in water etc is higher than the energy released when new bonds between the haloalkane and water are formed.

But as fluorine forms hydrogen bonds why couldn't a fluoroalkane form hydrogen bonds with water thus become more soluble in water?


texts: Acorrect range of concentrations for the reactants in the equilibrium reaction

texts:
What would be a correct range of concentrations for the reactants in the equilibrium reaction, $\ce{Fe^3+(aq) + SCN-(aq) <=> FeSCN^2+}$?

For a Chemistry project I am measuring the effects of changing the concentration of $\ce{Fe^3+(aq)}$ on the yield of $\ce{FeSCN^2+(aq)}$ produced. I'm going to use a spectrophotometer to calculate the absorbance of the products.
I was wondering what amounts of concentrations of $\ce{Fe^3+(aq)}$ and $\ce{SCN-(aq)}$ would be suitable.
My research suggests that I should set the spectrophotometer to around $\pu{450 nm }$and that the domain of the concentration of the product $\ce{FeSCN^2+(aq)}$ should be between $0 \le [\ce{FeSCN^2+(aq)}] \le 2 \times 10^{-4}$. Since I don't know the equilibrium constant, I would need to look at literature to find out what concentrations would be ideal since when absorbance > 1, the relationship is no longer linear.
I'm only varying the concentration of $\ce{Fe^3+(aq)}$ in 10 intervals (currently $\pu{0.1-1 mol/dl^3}$), the concentration of the $\ce{SCN-(aq)}$ will be kept constant.
What would be the ideal concentration range for $\ce{Fe^3+(aq)}$ and the ideal concentration for $\ce{SCN-(aq)}$?
ps. I am adding $\ce{HCl}$ as a neutralizer to the $\ce{Fe(OH)-}$ formed since it distorts the colour of the solution.
I am also using $\pu{20 ml}$ of $\ce{Fe^3+(aq)}$ solution and $\pu{20 ml}$ of $\ce{SCN-(aq)}$ and $\pu{10 ml}$ of $\ce{HCl}$.


texts: What is the geometrical structure of OF₂?

texts: Is it linear, angular, triangular or tetragonal? Well, since $\ce{O}$ has 2 electron matches of his own, I think it's tetragonal, but in wikipedia it is angular... Why? What about $\ce{CS2}$, is it linear?


texts: Find the Structural Formula of Hydrocarbon Compound X

texts:
There is a specific compound $\ce{C3H6O}$ that exists as hydrocarbon compound X. It does not react with metallic sodium, bromine does not lose it's color when applied to the compound, and does not give the silver mirror reaction when ammonium silver nitrate, in fact it doesn't react.

I've realized since it does not react with sodium, it cannot have a hydroxyl functional group, and that since bromine does not give the discoloration reaction, the Carbons of the compound cannot have double bonds. And obviously, if it does not give the silver mirror reaction, than it cannot be an aldehyde or a carboxyl acid. However, the answer that the book gave was $\ce{CH3COCH3}$. Am I doing something wrong here?


texts: I was told that 'water' was the most common material in the universe and I disputed that claim. I was met with the argument that hydrogen and oxygen were the most common atoms in the world so water was as well. If this is true, then how come we can't find water anywhere in outer space? It must be the collection of 2 hydrogen atoms and 1 oxygen atom that is so rare then?


texts: In ionic solids such as NaCl, do the cations fill interstital holes in the cation's cubic close pack structure?

texts: Are binary ionic solids like $\ce{NaCl}$ comprised of a cubic close packed structure of the anions with the cations filling interstital holes or do the cations and the anions contribute to the cubic close packed structure equally? I am really struggling with solid state chemistry - any help would be gratefully received. Also any suggestions for good learning resources on this topic would be great. Thanks.


texts:
I have a solution of water and oil mixed to as much as possible, since they won't actually mix. The supply is coming down a pipe at a relatively fast rate and I need to separate it so that the water goes down a pipe and the oil goes through another pipe.
How would this be done, without waiting days for it to occur?


texts: What is the mechanism of halogen displacement?

texts:
We teach (ad infinitum....) that a more reactive halogen will displace a lesser halogen from a compound.  And yes, the halogen is a halide ion in the compound.  Now I think about it, it's usually in solutions, so the halide is nominally solvated and surrounded by water (as hydronium ions?).

But how?

Does the halide lose the electron to give a radical, or does the halogen dissociate to radicals, or to ions, or is there an intermediate Cl2- ion, for example?  I realise this is several questions, but the major question is unaffected by my speculation.  All I have found is the bald statement about displacement and reactivity and the table we always draw.


texts:
I've always thought that orbitals lead to a loss of symmetry, and have never been able to give myself a satisfactory answer to this.

I'll explain via an example:

Let's take an $\ce{N^3+}$ atom. It's perfectly spherical, and has no distinguishing 'up' and 'down'. There is no set of 'preferred coordinate axes' for it since it has spherical symmetry (except the nucleus, but I doubt that matters).

Now, let's give it three electrons. They arrange themselves in the $2p$ orbitals, one in each (by Hund's rule). Now, suddenly, the atom has lost its spherical symmetry — we have a distinct triplet of orthogonal directions separate from the others.

This leads to these questions:
How can symmetry 'break' this way? Are the directions of the axes 'hidden' in the atom beforehand? Are they themselves wavefunctions (though a wavefunction of wavefunctions sound odd to me, this explanation makes sense-random events can break symmetries)

So, I'd like a clear explanation of how/why the symmetry breaks.


texts: How to store distilled water without introducing impurities?

texts: How can I store distilled water without introducing impurities?  I'm going to be doing so electrical studies of pure water and ice and I need a way of keeping the water pure during the experiments.  The water needs to remain relatively pure (I'm not yet entirely sure how relative yet), over at least the course of $1$ day.  What is a good container that won't be leeching any salts or other chemicals into the water?


texts: Strongest hydrogen bond between neutral molecules?

texts:
It is known that very strong hydrogen bonds can occur in charged systems, such as $\ce{[F-}\ce{-H+-F-]}$, while hydrogen bonds in neutral systems are much weaker in comparison.

What is the strongest known hydrogen bond within the following specifications?

both donor and acceptor monomers are neutral, and remain neutral upon association (no ionic bridges);
heterodimers are allowed (e.g. hydrogen fluoride and ammonia);
must be a single-site hydrogen bond - excluding dimers stabilized by multiple hydrogen bonds such as nucleobase pairs.


texts:
People are using filters to remove $\ce{CO2}$ from the air.

What are this filters made of and are there any other substances that attract $\ce{CO2}$?

How is $\ce{CO2}$ absorbed or attracted to these substances?

P.S: Sorry, I did not get any suitable Tags for this.


texts: Calculation of dispersion energies for organometallic complexes with Gaussian

texts:
I've tried to calculate dispersion energies of some organometallic complexes with the  Gaussian software using WB97XD/Gen (6-311+G**/LANL2DZ) level of theory because I have Au as heavy metal.
The calculation doesn't even start and ends by link 301 error.
The job section # opt WB97XD/gen pseudo=read

And the output's last line was
R6DRO: No vdw radius available for IA=79
Error termination via lnk1e in /home/pctci/g09/l301.exe

My input file was perfectly drafted, I don't know what the problem is.
Anyone could help me please?


texts: What is the hybridization of chlorine in vinyl chloride?

texts:
Is chlorine in vinyl chloride sp2 or sp3 hybridized?

Calculating using steric number it is found to be sp3 hybridized. But according to I. L. Finar* it is sp2.

*I.L. Finar: Organic chemistry Vol.1 Fundamental principles. Sixth Edition. Orient Longmans: 1973. Page 328.


texts: Neutralization of Sodium Azide using Ammonium Cerium Nitrate

texts:
I'm using Ammonium Cerium Nitrate to neutralize phosphate-buffered saline solutions containing 0.1% Sodium Azide. I add 0.55 grams of Ammonium Cerium Nitrate into 100 mL of this 1XPBS + 0.1% NaN3 solution and am able to neutralize the NaN3.

Will the resulting solution have any negative, harmful, effects if flushed down the drain? My main concern is polluting ground water or corroding our sewerage system.


texts: Can I anodize an aluminum coating on steel to have better corrosion inhibition for the steel?

texts: I am planning to coat aluminum on steel and I want to give the steel its maximum corrosion protection. Is anodizing the coating necessary?


texts: NAMD free energy calculations (FEP, Alchemical)

texts:
I am trying to calculate the absolute free energy of a protein-ligand-complex using the free energy perturbation theory.

Following the alchemical route in this tutorial, I have calculated eight MD-simulations over 24 lambda values (500ps each).

1/2: Ligand in protein (Ligand restraint, forward/backward)

 Ligand ->(forward) vacuum ->(backward) protein

3/4: Ligand in water (Ligand restraint, forward/backward

 Ligand ->(forward) vacuum ->(backward) water

5/6: Ligand in protein (Ligand restraints scaled, forward/backward)

 Colvars 1 ->(forward) 0 ->(backward) 1

7/8: Ligand in water (Ligand restraints scaled, forward/backward)

 Colvars 1 ->(forward) 0 ->(backward) 1

The free energy contribution of 1/2 and 3/4 is calculated with the  ParseFEP-tool. All colvar contributions were printed to the output file for each lambda value.

$\Delta G_{1/2} = -152.65 ~~~~ \Delta G_{3/4} = 152.1$

Is it sufficient to integrate the curves for each colvar and sum them up afterwards?

$\Delta G_{5/6} = 12.3 ~~~~ \Delta G_{7/8} = 1.84$

Do I have to subtract the colvar contribution from binding and solvation energy to get the absolute binding free energy?

$\Delta G = (\Delta G_{1/2} - \Delta G_{5/6}) - (\Delta G_{3/4} - \Delta G_{7/8}) = -11.1\,$kcal/mol


texts: How to determine the specific heat of aluminum?

texts:
I have a question from my AP preparation book that I got wrong and do not understand the explanation:

  A student designs an experiment to determine the specific heat of aluminum. The student heats a piece of aluminum with a mass of $\pu{5.86 g}$ to various temperatures, then drops it into a calorimeter containing $\pu{25 mL}$ of water. The following data is gathered during one of the trials:

  Initial Temperature of $\ce{Al}$: 109.1
  Initial Temperature of $\ce{H2O}$: 23.2
  Final Temperature of $\ce{Al + H2O}$: 26.8

I correctly calculated the heat gained by the water ($\pu{376.2 J}$), and the specific heat of aluminum ($\pu{0.78 J/g*C}$). However, how do I calculate the enthalpy change for the cooling of aluminum in water? The book's procedure is as follows:

$$\frac{\pu{5.86g}~\ce{Al}}{\pu{26.98g}~\ce{Al}} = \pu{0.217 mol}~\ce{Al}$$

$$\frac{\pu{376 J}}{\pu{0.217 mol}} = \pu{1730 J//mol} = \pu{1.73 kJ//mol}$$

I see that one may calculate specific heat by dividing the heat gained by water by moles of aluminum and converting to kilo-joules per mole in this scenario. However, why is that? What is the reasoning behind this procedure? How would you phrase this procedure to apply to this general type of question?


texts: Finding equilibrium constant for the reaction between non-stoichiometric mix of gaseous components

texts:
$$\ce{CH3OH(g) + NOCl(g) <=> CH3ONO(g) + HCl(g)}$$
The volume of the container is $\pu{433 cm^3},$ $T = \pu{50 °C}.$ Methanol was added until the pressure was $\pu{50.1 mbar},$ then $\pu{0.059 g}$ of $\ce{NOCl}$ was added. At equilibrium the partial pressure of $\ce{NOCl}$ is $\pu{27.6 mbar}.$
Calculate $K.$

I assumed that $\pu{50.1 mbar}$ was the partial pressure of methanol (I do not know if this is correct) and calculated the initial partial pressure for $\ce{NOCl}$ from the ideal gas law:
$$p = \frac{nRT}{V} = \frac {(\pu{0.059 g}/\pu{65 g/mol})\times 8.314\times 323}{\pu{4.33E-1}} = \pu{5.63 Pa} = \pu{5.63E-5 bar}$$
Then
$$
\begin{array}{cccc}
&\ce{CH3OH(g) &+ &NOCl(g) &<=> &CH3ONO(g) &+ &HCl(g)} \\
&\pu{0.0501 bar} && \pu{5.63E-3 bar} && 0 && 0 \\
&\pu{0.0501 bar} - x && \pu{0.0276 bar} && x && x\\
\end{array}
$$
When I then solve for $x$ I get a negative value which isn't correct. Is $\pu{50.1 mbar}$ supposed to be the total pressure and if yes, how do I use that then? The correct answer for $K$ is $1.33.$


texts: What nuclei need to be NMR active in an HMBC experiment?

texts:
I recently had a discussion where I was told that in an $\ce{^1H}/\ce{^13C}$-HMBC experiment coupling through an $\ce{C-O-C}$ ether bond would not be observed with the reasoning that O is not NMR active. That somehow surprised me as I thought only the "end nodes" in the coupling needed to be NMR active. So I have the following two questions:

Do the nuclei in-between need to be NMR-active?
Does the end node X need to be NMR-active?


texts: What kind of filter can remove zeolite dust from ethanol?

texts:
I only really have high school level knowledge of chemistry, and also I don't really own any lab equipment.
I'm using 3A zeolite molecular sieves to dry ethanol (and sometimes isopropanol) and they seem to be working great.
However, I'm always left with a bunch of dust.
I can let the dust settle over night and then pour off the top in the morning, but it's still got an orange tint to it. I can keep repeating that process but it starts to take a really long time.
I tried running it through a coffee filter but the particles are too small for the coffee filter to catch.
What should I look for in a filter paper / what other material could I use to filter the remaining dust out of the ethanol?
I don't want to distill it, I don't have the setup for that.


texts: How to set up equation for buffer reaction?

texts:
For buffer equations, how can you tell what to react with water?

For example, if I have a 1 M acetic acid solution and 1 M sodium acetate solution (a conjugate acid-base pair) mixed together and am asked to find the pH, how do I know how I should write the equation?

Do I react acetic acid with water to give me the products, or sodium acetate with water to give me a different set of products?


texts: If you place a piece of paper created by a laser printer, e.g. fax paper or some receipts, on top of a piece of normal paper you have drawn on with a Bic Marking 2300 permanent marker, the image transfers to the fax/receipt paper? Do any non-toxic solvents heat up as they evaporate? If so, would that explain the reaction between the paper and ink?


texts: Crystal field splitting of other orbitals

texts:
According to crystal field theory (CFT), $\mathrm{d}$-orbitals of central metal atom splits due to non uniform repulsion of ligands around the metal atom. Why isn't $\mathrm{p}$-orbital splitting discussed?

Argument: As in case of square planar complexes $\mathrm{(dsp^2)},$ $\mathrm{p}$-orbitals are involved which are facing different conditions of repulsion. So, $\mathrm{p}_{xy}$ must have higher energy than $\mathrm{p}_{xz}$ or $\mathrm{p}_{yz}.$ This happens in case of trigonal pyramidal structure too.


texts: What dynamical features allow for the existence of a liquid-liquid transition?

texts:
Recently it has been shown theoretically[1] and then experimentally[2] that a liquid-liquid transition (LLT) takes place in pure supercooled water. That is to say, two distinct liquid phases have a direct transition between each other on the phase diagram. This was a very controversial result as I understand it (and is something people have argued about for a while apparently). It is not the existence of an LLT that is controversial, but rather the existence of an LLT in water.

I am rather confused by this whole idea, however. Ordinarily, when we talk about phase transitions, there are very clear dynamical and energetic reasons why the transition should take place. For instance, water has hydrogen bonds that get weaker and weaker as the temperature increases because the molecules deviate from the minimum energy structure more often which leads to repulsion. Thus, the existence of a phase change from liquid to vapor must exist because at some point the repulsions overcome the attraction. Similar kinds of arguments can be thought of when going from the liquid to solid, and even from solid to solid.

I cannot think of a similar simple competition which makes it clear to me why a liquid-liquid transition should ever happen. I have looked at ref. [3] which makes it clear that the two phases (of this mixture, not water) display different average hydrogen-bonding arrangements, one of which is bimodal. It isn't so surprising that there could be two different hydrogen-bonding arrangements in a phase diagram. What does surprise me is that the path between two hydrogen-bonding arrangements is not smooth.

So, to say it as simply as I can, what competing interactions are responsible for the existence of a LLT in water?

One important point is that all the qualitative features of this transition were described by the TIP4P 2005 water model in ref. [1]. TIP4P has a potential energy function described by Lennard-Jones forces. This confounds me even more because the physics exists in a simple Lennard-Jones fluid with only pairwaise interactions.

References:

[1]: Singh, R. S., Biddle, J. W., Debenedetti, P. G., & Anisimov, M. A. (2016). Two-state thermodynamics and the possibility of a liquid-liquid phase transition in supercooled TIP4P/2005 water. The Journal of chemical physics, 144(14), 144504.

[2]: Zhao, Z., & Angell, C. A. (2016). Apparent First‐Order Liquid–Liquid Transition with Pre‐transition Density Anomaly, in Water‐Rich Ideal Solutions. Angewandte Chemie, 128(7), 2520-2523.

[3]: Bruijn, J. R., van der Loop, T. H., & Woutersen, S. (2016). Changing Hydrogen-Bond Structure during an Aqueous Liquid–Liquid Transition Investigated with Time-Resolved and Two-Dimensional Vibrational Spectroscopy. The journal of physical chemistry letters, 7(5), 795-799.


texts: Would sodium salicylate dissolve in HCl?

texts: I've been searching around the web and the consensus seems to be sodium salicylate dissolves poorly in HCl because it would form salicylic acid. However, I don't understand why forming salicylic acid product (which is poorly soluble in water) would make sodium salicylate (which is the reactant) dissolve poorly in HCl. If HCl doesn't contribute to making it more soluble, wouldn't the polarity of the water molecule dissolve it anyway?


texts: Oxidation of aluminum and manufacturing of electrolytic capacitors

texts:
My background is in electrical engineering. Recently I saw instructions on how to manufacture electrolytic capacitors at home by mixing sodium bicarbonate (baking soda) to distilled water, submerging two pieces of aluminum foil into the mixture and applying electrical current through the pieces until current dropped to almost zero. The instructions I followed are here:

https://rimstar.org/science_electronics_projects/make_electrolytic_capacitor.htm

The end result was satisfactory.

However, as I have only very basic knowledge in chemistry, I have only a very vague understanding of what happened, and I would like to understand it in more detail. The article did not explain it very well and I haven't been able to obtain good explanation elsewhere either.

I understand that the current somehow oxidizes the aluminium to form an insulating aluminium oxide layer on top of another one of the plates.

So I would like to pose the following questions regarding this experiment:

Why is distilled water required? I understand that distilled water is basically tap water except its impurities such as charged ions have been removed. This, I believe, makes the water much less conductive. But don't we need the water to conduct? I believe the water, as the electrolyte, acts here as the other plate of the capacitor, with the oxide layer insulating it from the other plate in the final product.
What is the role of the sodium bicarbonate? What exactly does it do in the chemical reaction? We are using distilled water, but then we add sodium bicarbonate to it.
What is the reaction formula of the oxidation? Could you show me how the water, sodium bicarbonate and the aluminium react together to form aluminium oxide, and what is the role of the electric current? I understand that this oxidation of metals, such as aluminium, happens in air as well, and this method simply "accelerates" this process to produce a thicker, more insulating layer.

I would greatly appreciate if somebody could help me understand this process!


texts: How can a weak base act as a strong nucleophile (and vice versa)?

texts:
Carboxylate ion ($\ce{RCOO-}$) is a weak base as the negative charge on oxygen is delocalised due to resonance. So, it has less tendency to donate lone pair of electrons to H+ ion. Similarly, it has less tendency to donate lone pair of electrons to a carbocations. But in my textbook, it is given that, it acts as a weak base but strong nucleophile. Why does it act as strong nucleophile?
LDA (lithiumdiisopropylamide) is a strong bulky base. Why it is considered as a weak nucleophile?


texts: Potassium thiocyanate and iron(II) acetate

texts:
I am trying to find the net-ionic equation for the reaction of potassium thiocyanate and iron(II) acetate.

It seems reasonable to me that the molecular equation is

$$\ce{2KSCN + Fe(CH3COO)2 -> 2CH3COOK + Fe(SCN)2}$$

which would give the net-ionic form

$$\ce{SCN- + Fe^2+ -> Fe(SCN)2}$$

My chemistry teacher says the correct form is

$$\ce{4SCN- + Fe^2+ -> Fe(SCN)4^2-}$$

First I don't know what molecular equation would give rise to this. Second, why in the world is my guess, which is simpler, wrong and this one correct?


texts: How does one calculate oxidation states?

texts:
For example, how could I calculate the oxidation state of lead in $\ce{PbS}$? Or for that matter how would I calculate it for sulfur? Or I have two unknowns, for example sulfur in $\ce{PbSO4}$? Do I assume that lead has a 2+ charge and therefore a +2 oxidation state and since it has ? Or is there something that I am missing? Additionally, from all the reading that I've done I've only found a rule for bromine, chlorine, and iodine in binary compounds, what happens if they are in a compound with more than two elements? For example $\ce{COCl2}$. How would someone calculate the oxidation state of carbon? This stuff is really confusing for me and I apologize if this seems really basic or I have missed something.

I have read the introduction to oxidation states post, and it was a very well written answer, however it still did not help things click. I still feel like I am missing something


texts: Why do we use hydrochloric in the test for sulfate ions but nitric acid for halide ions?

texts:
Recently, I have learnt about testing for ions in qualitative analysis (BBC Bitesize).

The link above which I used for reference mentions that for the test for sulfate anions, hydrochloric acid $(\ce{HCl})$ is used to ensure that there is no presence of carbonate ions.  For the test for halide ions $(\ce{F-},$ $\ce{Cl-},$ $\ce{Br-},$ $\ce{I-},$ etc), nitric acid $(\ce{HNO3})$ is used instead, for the same purpose.

I would like to know why the acids used are different, since they serve the same purpose.

Update: $HCl$ cannot be used for removal of carbonates in halides since $HCl$ contains the $Cl-$ halide.  However, as to why nitric acid cannot be universally applied to all, I am still unsure.


texts: To extract caffeine from coffee, I tried reacting it with baking soda to make tannins more soluble. I then put in salt to push caffeine out of solution. I saturated it with salt and then mixed the solids with acetone to get the caffeine out. There is also some salt in the acetone. Washes with water should remove the salt and tannin salts leaving behind the caffeine(not pure). Would this procedure work? Is there another procedure that would be more efficient and not require DCM.


texts: Difference between catenation and allotropy

texts: Can anyone tell me what the difference between catenation and allotropy is? I would like the basic explanation.


texts: Reaction of nitrobenzene with sodium metal in ethanol

texts:
The reactant is nitrobenzene(only) and reagent is Na metal in solvent liquid ammonia along with ethanol (which i am assuming is playing the role of proton donor please correct me if i am wrong).

The first thing that comes in mind is "alkyne" but there is not any alkyne in nitrobenzene( not even in its resonance structures).How this reaction will proceed?

In answer, the DBE is just reduced by one.I was also trying what if it was toluene?Can i have a explanation based on mechanism?


texts: Comparing O−O bond length in hydrogen peroxide and dioxide(2−) ion

texts:
Problem

How can we qualitatively compare the bond lengths between $\ce{H2O2}$ and $\ce{O2^2-}?$

Answer

 Bond length in $\ce{O2^2-}$ is slightly larger than in $\ce{H2O2}.$

Attempt
I tried using molecular orbital theory, but since both have peroxide $\ce{O2^2-},$ the differentiating factor must be some sort of repulsion, but I'm not getting it.


texts: Can we dissolve salts with higher lattice enthalpy by providing heat?

texts:
It is well-known that

A salt with a higher lattice energy will not dissolve at all, because then $\Delta_{\text{sol}}H^\ominus$ will be negative.

So, the reaction should be endothermic, right? My question is:
If then we provide heat to the reaction, then we should be able to dissolve such salts. Is this true?


texts:
I am studying chemistry from the book titled "Fundamental Chemistry for Cambridge O Level" written by Rosemarie Gallagher and Paul Ingram.
On page 17, it states that

  oxygen boils at −219 °C and freezes at −183 °C.

Isn't this incorrect? Should it not be the other way round?


texts: Graphical representation of reductive powers of NaBH4 and LiAlH4?

texts:
I don't know whether this is a valid question, I will delete it if it is inappropriate.

I am looking for a graphical representation of the reductive powers of $\ce{NaBH4}$ and $\ce{LiAlH4}$. Such as this

but then including acyl chlorides and the other important organic functional groups.


texts: Is there any mathematical or logical proof that carbon with 4 different groups would be chiral?

texts:
In chemistry; chirality is generally defined in 2 ways.

Lord Kelvin's definition: "I call any geometrical figure, or group of points, chiral, and say it has chirality, if its image in a plane mirror, ideally realized, cannot be brought to coincide with itself" (source: 1. chirality.org , 2. Biochemistry book by Lubert Stryer.)

"If a tetrahedral (sp3) carbon atom contains a different chemical group on each of its 4 hands, the central carbon atom is called chiral. Though there are some exceptions where we do not found any chiral carbon still some compounds can be chiral. Chiral molecules cannot be superposed with their 3-dimensional mirror image" (common classroom-definition for chirality).

But it seems the first definition is the basic definition; and the second definition seems to be a corollary or application of the first definition.
Now I want to know; is it possible to 'prove' or 'derive' the second definition (better to say second statement or second description) from the first (Lord Kelvin's) definition mathematically or geometrically or logically? and if possible then how to prove the second definition from the first definition?
This question is related but different from this question


texts: How to determine relative polarity (basic procedure)?

texts:
I am taking AP Chemistry, and have noticed that I can identify a polyatomic polar molecule, but struggle to determine which molecule is the most polar given a set of several polar molecules.

What would be a basic procedure/set of questions to ask myself in determining which molecule is the most polar? I hope my question is not too general...

Thank you!


texts: Identification of an unknown organic molecule from only 1H NMR and 13C NMR

texts:
I am currently trying to determine the structure of my unknown compound with both 1H NMR and 13C NMR spectra.

My H NMR peaks:

1.16 ppm [singlet, 1H], 1.68 [singlet, 3H], 1.75 [singlet, 3H], 4.2 [doublet, 2H], 5.4 [multiplet, 1H], and 7.24 (solvent peak)

C NMR:

18, 26, 59, 77 (solvent peak), 124, and 136 ppm.

I have deduced that my molecular formula is $\ce{C5H10O}$. And I am fairly certain I should have a double bond in my structure. However, I do not know intuitively where this pi bond should be.

What should I be looking for to determine the placement of this pi bond?

I unfortunately do not have characteristic IR peaks to determine whether I have an alcohol, ether, or a ketone.


texts:
I think this picture from wikipedia is wrong because I count:

\begin{align}
\left.
\begin{array}{ccccr}
1&×&1 &= &\ce{1~Y} \\
6&×&\frac{1}{8} &= &\ce{\frac{3}{4}O}
\end{array}
\right\} \text{ gives }\ce{Y4O3}
\end{align}

How would be the correct elementary cell of $\ce{Y2O3}$?

(I didn't found any correct elementary cell using google)


texts:
As far as I could remember, in the same period, a bond to a more electronegative atom implies in a more polar and stronger bond, due to the greater ionic character. However the bond dissociation energy for the C-X series follows the order: C-F > C-O > C-C > C-N. The same for H-X: H-F > H-O > H-C > H-N.
Why are the bonds to nitrogen weaker than expected? (Or, more speficically, weaker than bonds to carbon, where no dipole is formed)
Values of average bond enthalpies I based my question off:

Bond
BDE (kJ/mol)

H-F
565

C-F
484

H-O
463

C-O
360

H-N
388

C-N
305

H-C
412

C-C
348

Sources: Atkins' Chemical Principles, Housecroft's Inorganic Chemistry, http://butane.chem.uiuc.edu/cyerkes/Chem104ACSpring2009/Genchemref/bondenergies.html


texts: Why is HNO3 a stronger oxidising agent than H3PO4?

texts: Why is $\ce{HNO3}$ a stronger oxidising agent than $\ce{H3PO4}$? $\ce{N}$ and $\ce{P}$ have the same oxidation number. Is it the electronegativity difference between $\ce{N}$ and $\ce{P}$?


texts: Show the vibrational frequency of fluorine molecule anion is much lower than that of fluorine molecule

texts:
Basically I need to draw the molecular orbital for $\ce{F2}$ and then answer a bunch of questions about it. I have drawn it correctly, as far as I know, but I don't know how to use it to show that the vibrational frequency of $\ce{F2-}$ is lower than $\ce{F2}$.
I worked out the bond order for $\ce{F2-}= 0.5$  and for $\ce{F2}= 1$. Is this what you use to find it out, or is it something to do with the HOMO-LUMO?


texts: What is the best Electronegativity cutoff for my calculator?

texts:
I have written a Chemical Bond Polarity Calculator application, which many students use for their homework.  I sometimes get questions from these students as to why the cutoff I use is 2.0, and not some other number between 1.7 and 2.1.  I understand that there is no hard and fast rule as to what the cutoff should be.  I just want to know what a real chemist (I'm a computer programmer, not a chemist) would want this particular application to use for the cutoff.  Conversely, would a real chemist want to be able to input the cutoff themselves?

This post indicates that 2.1 is a good cutoff, and this post indicates the number should be between 1.7 and 1.9.  How would the real chemists out there recommend I modify this application?


texts: opening valve separating two volatile solutions

texts:
Let there be two containers A and B containing two volatile solutions (ideal) of  pure liquids P and Q  respectively. The containers are connected by a tube such that only vapours can travel through it but it is initially closed by a valve. Now the valve is opened at $t=0$.
What will be the final equilibrium pressure over the containers?

My  Approach:
I think that final pressure will be somewhere between the pressure of pure liquid P and pure liquid Q, might their average but I can't say for sure.
vapour pressure is a function of temperature so might be there is no change ,if the liquids would have been mixed inn a single container , forming ideal solution with specified mole fraction of each component then I know how to use Raoult' s law but here I don't see the situation being an equivalent one.


texts:
Has anyone seen a version of the iodine clock reaction where instead of the system oscillating between clear and blue it shows blue bands travelling down the vessel?

I ask because someone not unknown to this site has made a version of the experiment with such moving bands and I was wondering if it was worth sending a write up of it to the Journal of Chemical Education or some similar journal.

Clarification:

Apologies if I was unclear, I am asking the phenomenon has been published before or if it is unpublished but already well known.

I know the BZ reaction can produce all sorts of patterns, but I have never seen travelling bands in the iodine clock. A quick Google has found no mention of the phenomenon. I am not asking "is it worth publishing", which I believe is against site rules anyway. I'm just asking about prior art.


texts: How to arrange carboxylic acids (phenylacetic acid and acetic acid) by increasing acidity?

texts:
Why is $\ce{Ph-CH2-COOH}$ more acidic than $\ce{CH3COOH}$ although the equilibrium of ionization lies mainly backward for both of them?

Attempt:
In the ionized form of $\ce{Ph-CH2-COOH}$ we have a $\ce{Ph-CH2}$-group donating its electron to carbonyl carbon while in case of acetic acid we have a methyl group donating its electron to the carbonyl carbon.
But which one of them is stabilized more?


texts: Activity of a chemical species and compound

texts:
While reading a book on Instrumental analysis by Skoog, in appendix part they explain activity of a species.

The relationship between activity of a species and it's molar concentration $[X]$ is given as $a_x=\gamma_x[X]$ where $\gamma_x$ is a dimensionless quantity called the activity coefficient of $X$.

Basically $\gamma_x$ tells about measure of effectiveness with which that species influence the equilibrium in which it is a participant.They say that in the expression of equilibrium constant, activity of the compound is used instead of its concentration.
In high school, we use the concentration of the compound and the activity of a compound is not introduced at that time. But it is also the fact that the concentration of compounds given at that time is very low for which $\gamma_x \to 1$. So $a_x \approx [X]$.
Basically, the question is that what is the need of the concept of activity for using in the expression of equilibrium constant? Without using this concept when the concentration of compounds is high (in this case $\gamma_x<1$ and $a_x<[X]$), what contradicting result we would get?
Also please tell me some reference  where I get the derivation of mean activity coefficient ($\gamma_{+-}$) of an electrolyte $A_mB_n$, given as $\gamma_{+-}=(\gamma^m_A \gamma^n_B)^\frac{1}{m+n}$.


texts: Experimental verification of the field effect

texts:
March's Advanced Organic Chemistry has the following paragraph

  The other effect operates not
  through bonds, but directly through space or solvent molecules, and is called the field
  effect. It is often very difficult to separate the two kinds of effect, but it has been
  done in a number of cases, generally by taking advantage of the fact that the field effect
  depends on the geometry of the molecule but the inductive effect depends only on the
  nature of the bonds. For example, in isomers 1 and 2 the inductive effect of the chlorine
  atoms on the position of the electrons in the COOH group (and hence on the
  acidity, see Chapter 8) should be the same since the same bonds intervene; but the field
  effect is different because the chlorines are closer in space to the COOH in 1 than they
  are in 2. Thus a comparison of the acidity of 1 and 2 should reveal whether a field
  effect is truly operating. The evidence obtained from such experiments is overwhelming
  that field effects are much more important than inductive effects.

The diagram:

I simply do not understand how 2 is more acidic than 1. Since the field effect is greater in 1 , should not 1 be more acidic?


texts: Biological Consequences of Asteroid Mining—Death by Isotope?

texts:
It's been documented that NASA hope to capture an asteroid in 2025, and have subsequent aims to mine that asteroid. If if this is successful, we would expect other asteroids to be mined in the future.

A consequence of this is that relative atomic masses of elements mined—those with two or more stable isotopes—will no longer be faithful to our current periodic table. Ruthenium alone, a high-value rare earth, has five stable isotopes alone, ranging from $^{98}\ce{Ru}$ to $^{102}\ce{Ru}$. The relative abundances of these isotopes are bound to differ in other places other than Earth, and so would the weighted average.

Say after mining our ruthenium, we use it in an electronic device and consequently that device is thrown away. For argument's sake, also say that this ruthenium—of an isotopic distribution never before seen—leaches into the environment and later comes into contact with biological systems. Could it be possible that compounds hitherto considered non-toxic on Earth become toxic to biological systems by virtue of a newly realised isotopic discrimination?

As an example, $^{13}\ce{CO2}$  is effectively discriminated against in uptake by plants in comparison to $^{12}\ce{CO2}$  (due to it being a diffusion limited reaction). Ruthenium is purported to be carcinogenic, but the most abundant isotope on Earth of Ruthenium is $^{102}\ce{Ru}$ which could be effectively non-toxic by virtue of the fact that  compounds containing these atoms takes so long to diffuse, they don't diffuse across biological membranes at all.

If a sample of Ruthenium from the moon found its most abundant isotope in $^{98}\ce{Ru}$, then this would be expected to diffuse much faster than its heavier counterparts. Therefore could it be possible that a compound previously thought of as non-toxic could become toxic via this effect. Does this sound plausible?

NB: I've deliberately missed out other routes of exposure such as ingestion to only consider diffusion controlled reactions.


texts: What is the role of acid in keto enol tautomerism

texts: I have heard about an acid acting as a catalyst in keto enol tatutomerism.I have yet to understand the mechanism of the reaction though.pictorial depictions are welcome.


texts: Are there ways to fully dissociate a complex salt?

texts:
A complex salt is a salt where the metal and ligands do not dissociate in water.

For eg : $\space\ce{K_4[Fe(CN)_6]}$ when put into $\space\ce{H_2O}$ dissociates as : $\space\ce{4K^+} + \ce{[Fe(CN)_6]^{4-}}$

where $\ce{[Fe(CN)_6]^{4-}}$ is a complex ion which cannot be further dissociated.

So, is there any way to dissociate them, either by heating or by adding something? Or will they dissociate in some other solvent? Or is there no way to dissociate them?


texts: Reaction of 1,3 Butadiene with HBr in the presence of peroxides

texts: I have learnt that the reaction of 1,3 Butadiene with HBr depends on the temperature as the temperature determines whether the reaction is under kinectic control or thermodynamic control. I believe that this is due to the hybrid nature of the carbocation and relative stabilities of the products. Will the same effects take place in the presence of peroxides? (because the allylic radical is also resonance stabilized)


texts: What pressure does liquid nitrous oxide need at −45 °C?

texts: What pressure does liquid nitrous oxide need at −45 °C to remain liquid? How can I calculate its pressure required for other temperatures?


texts: How to solve this kind of problems. What determines their stability?