texts: Does iron in water become visible when being heated?

texts:
I'm using ground water to provide my daily needs: Laundry, bath, toilet, ... I don't use it as drinking water, but I do cook with it.

What I noticed is that when using the water cold it appears as water from a bottle, but when I start to heat the water it turn orange as if the iron becomes more visible? It also is visible from water coming out of the boiler.

Does iron in water become visible when the water is being heated?

Another fun fact, just for information, when it rains a lot the orange color is more dense.

Greetings.


texts:
What is the charge of Silicon dioxide ions? I can't find it anywhere.

It seems to be 0?

Also is there anywhere I can find these on my own?


texts: Cleaning silver - which method is better?

texts:
What is the advantage of this approach over polishing the silver with an abrasive?

"Silver tarnish is an outer coating of silver sulfide, $\ce{Ag2S}$, formed when silver reacts with trace quantities of air-borne hydrogen sulfide, a smelly gas produced naturally by the digestion of food in living animals.  Silver atoms in silver sulfide have lost electrons to sulfur atoms in creating ionic bonds.  You can remove this tarnish with home electrochemistry.  Convert silver atoms back to their elemental state by restoring their electrons.  Sulfur atoms won't relinquish electrons to silver, but with the proper connection, aluminum atoms will.  Add about a liter of water with several heaping tablespoons of baking soda to an aluminum pan that has been scoured clean.  If you don't have an aluminum pan, use several large strips of aluminum foil at the bottom of another pan.  Bring the water to a boil and remove it from the heat source.  Slowly immerse a tarnished piece of silver; you'll see an immediate effect as the silver and aluminum make contact.  (Add more baking soda if you don't see this.)  Also, as silver is brought back to its elemental state, hydrogen sulfide is released back into the air.  You'll smell it!  The baking soda serves to remove a thin and transparent coating of aluminum oxide, which normally coats aluminum and thus prevent direct contact.  The baking soda also serves as a conductive ionic solution to permit the passage of electrons from the aluminum to the silver."


texts:
How do I theoretically predict the acidity order of the following para-halophenols?
(experimental $\mathrm{p}K\mathrm{a}$ values beside each)

parafluorophenol (9.92)
parachlorophenol (9.41)
parabromophenol (9.17)
paraiodophenol (9.30)

Experimental acidic strength order: parabromophenol > paraiodophenol  > parachlorophenol  > parafluorophenol

At first, I thought of simply using the -I effect to determine the stability of these phenol derivatives. Since -I effect is shown best by fluoro group, therefore charge delocalisation would be best in the fluoro derivative's anion. But then at the same time, there's +M effect of fluoro group too. This answer emphasises on the dominance of inductive effect of chloro group over its mesomeric effect. Is this applicable to fluorine too?

I also thought of intermolecular hydrogen bonding that would be strongest in parafluorophenol decreasing its acidity.

Quora answers here associate the higher acidity of 4-chlorophenol to the presence of vacant d- orbitals in chlorine atom, but "d-orbitals'" usage by a third period element is debatable.


texts: Geometries of SCl2(OCH3)2 and SF2(OCH3)2

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I am not able to understand the difference between structure of $\ce{SCl_{2}(OCH_{3})_{2}}$ and $\ce{SF_{2}(OCH_{3})_{2}}$.

I am already well versed with Molecular Orbital and VSEPR theories. I found the geometries,
but don't understand why they are:

Why is the $\ce{F}$ at axial positions and $\ce{Cl}$ on the other hand in equatorial positions? (I am not able to understand Bent's Rule to be straight-forward, I have read Wikipedia already.)


texts:
Having to separate freshwater crabs for commercial fisherman while on the boat, we dump the crabs in ice water, as crabs aren't as aggressive and bite less when cold.  There's only so much room on the boat for carrying ice, and the ice melts too quickly in the wooden box filled with water and ice in order to "slush" the crabs.  We've been unable to work full days, running all of our crab traps, as we run out of ice before a full-day's work.  Any ideas of how to slow the melting process of the ice while in the water used for slushing the crabs?  Thanks for your time and knowledge.
"


texts: Why is the size of Al3+ less than that of Li+?

texts:
Why is it so that the size of $\ce{Al^{3+}}$ is lesser than $\ce{Li+}$?

I'm a bit confused about this one as the aluminium(III) ion is composed of 10 electrons and 13 protons, while the lithium ion has only 2 electrons and 3 protons.

Electronic configuration of $\ce{Al^{3+}}$ is $\mathrm{1s^2 2s^2 2p^6}$ and that of $\ce{Li+}$ is $\mathrm{1s^2}$.

Now, it seems obvious that the size of $\ce{Al^{3+}}$ should be greater than that of $\ce{Li+}$, but it is actually the other way around. Why is this? I think that it is a kind of exception, but if anyone can explain the reason behind this, it will help me in my upcoming tests.


texts: Sulfates and persulfates as accelerants in black powder?

texts: I saw there was a few black powder posts on here so I'd like to pose a question. Would sulfates or persulfates like the oxidixer soduim persulfate be a good replacement for some percentage of the nitrates or usual sulfer content of black powder? Pursulfates are used as an ingredient in flash powder for pyrotechnics and is a strong oxidizer to combustibles, so I assume it would make a good accelerant in some concentration. Would it perform under the pressures and speeds needed for an old fashioned firearm, or would it be too corrosive to be practically used?


texts: How to distribute the Boltzmann energy to internal and external motion?

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If we have an isolated pentane molecule at room temperature (RT) the Boltzmann energy $(E=k_\mathrm{B}T)$ is approxately $0.59\ \mathrm{kcal/mol} \overset{\wedge}{=} 207\ \mathrm{cm^{−1}}$. There is not enough energy for an electronic or vibrational excitation, so the molecule is in its electronic and vibratory ground state. However usually 10–20 rotational states are populated at RT. Can we attribute mathematically (to a first approximation) this $207\ \mathrm{cm^{−1}}$ amount of energy to $x\:\%$ translational energy ($E_\mathrm{kin} = \frac{m v^2}{2}$) and to $(100-x)\:\%$ rotational energy?

This question is related to the question about the internal degrees of freedom for a molecule: Rotational degrees of freedom (3N-5 and 3N-6)


texts: How do I model atoms with Moebius strips?

texts:
This question came to me while I was trying to model the list of elements (Mendeleïev), especially their masses and number of electrons.
It came to my mind that it might be easier to model each element as Moebius Strip with $n$ twists.

If this is possible, is there any literature about this subject? A methodology to do this?

----EDIT----

Ok,
it took me a while to go deep into the subject in order to present "concrete thoughts" but I finally could summarize them into the following spreadsheet:

https://onedrive.live.com/redir?resid=b20ec7aa903ebb07!701&authkey=!AE5lfNOaYgtJWNg&ithint=file%2cxlsx

The model has a R² = 0.9976 (what I think is pretty good as a first try)

Please check the spreadsheet in the following order:

A) Observation VS calculation

B) Racionale ( that presents the reasoning used to make the calculations used by the model)

C) Consequences (the rational consequences of the model --> I'm NOT sure that the reasoning expressed in this table is valid

D) Data ( the data and its source used to make the ratio between 'calculations' and 'observations')


texts: How to know which atom is the central atom in VSEPR theory?

texts:
How to find the central atom? What is the central atom in $\ce{PCl3}$
and  how to find the shape using VSEPR theory?


texts: Selectivity Coefficients of Ion Exchange Resins - Selectivity Reversal with TDS / Ionic Strength

texts:
I'm currently studying ion exchange resins and generally getting a bit stuck on some points of information which I do not fully understand / are not very well explained within the literature.

I understand that resins having varying selectivity or affinity for a particular ion and selectivity generally increases with increased valance number, atomic weight, reduced hydrated radius, etc.

I have seen some information that selectivity reversal will occur when the solution has high TDS e.g., sulphate will have a far higher affinity than chloride for a strong base anion resin within a solution with low TDS; however, at high TDS the affinity of these ions for the resin will be reversed - chloride will have a greater affinity than sulphate.

Any idea whether this is correct and what the mechanism causing this change is?


texts:
Elements $\ce{Co}$ and $\ce{Ni}$ share many similar/same properties and usually if one of them is an example of some group (e.g., ferromagnetism, same possible oxidation states, packing fraction and coordination number in lattice, melting and boiling point,  similar properties of their alloys, etc.), the other is too.

I understand that it may be due to similar sizes and atomic numbers, but many other elements have these properties in common. Can you give any other example of such a pair and why only few of these exist, or why this relationship between  $\ce{Co}$ and $\ce{Ni}$ special?


texts:
Does it mean that if one side of a reaction is favoured, the reaction will shift to the other side? As I was reading up on the van't Hoff equation, it says that an increase in temperature of an endothermic reaction will favour the products. It also showed a graph where lnK increases with temperature (T). But I thought what would happen in this case is the reactants will be favoured and then the equilibrium will shift to the right to de-stress the equilibrium?

So in summary, I'm just quite confused about what it means by favouring a side of an equilibrium.


texts:
Why doesn't cyclohexene have a cis-trans isomer whereas cyclodecene has one?
Is strain a factor?


texts: Why does rounding off the mol values when finding an empirical formula lead to a different result?

texts:
The question I was doing tells you that the compound consist of 49.0% carbon, 2.7% of hydrogen ,and 48.2% of chlorine. And ask you to find the empirical formula.

I did the usual procedure of dividing the percentages by each elements atomic mass. Because the result for carbon was 4.0796, I thought I should rounding to four moles of carbon. And for hydrogen and chlorine the numbers of mole for each are 3 and 1.  I want to check the formula is correct, so I make it 8 moles of carbon, but then the number of mole for hydrogen turns out to be 5 and chlorine 3.

Now there is a new empirical formula. Which one is correct?

PC: when I divided the percentages by atomic mass, I rounded the results to ten thousandth place.


texts: Equation for overall heat transfer coefficient

texts:
The heat flow (in $[\pu{J/s}]$) through the wall of a tube of length $L$ and inner radius $R_0$ is
$$Q = (2πR_0L)U(T_{1\infty} - T_{2\infty}),$$
where $T_{1\infty}$ is the bulk temperature in the inside and $T_{2\infty}$ is the bulk temperature on the outside. The overall heat transfer coefficient reads as:
$$\frac{1}{UR_0} = \frac{1}{h_1R_0} + \frac{\ln{(R_a/R_0)}}{k} + \frac{1}{h_2R_a} \tag{1}$$
where $R_0$ and $R_a$ are the inner and outer radius of the tube, respectively, $h_1$ and $h_2$ are the inner and outer heat transfer coefficients, and $k$ is the thermal conductivity of the wall.
How does Eq. (1) simplify for the $T$-profile shown on the left?

$U = k/R_0 \cdot 1/\ln(R_a/R_0)$
$U = h_1$
$1/U = 1/h_1 + 1/h_2 \cdot (R_0/R_a)$
$1/UR_o = (\ln(R_a/R_o)/ k ) + (1/h_2R_a)$

I had seen a similar $T$-profile in one of our exercises and there they used Eq. (1), however when selecting option 1, I get "incorrect answer". How can you tell from looking at the $T$-profle what the equation for the overall heat transfer coefficient will be?
All help and hints are appreciated!


texts:
background :

  As proved by rate of EAS, mesomeric or simply conjugated resonance is weaker for halogens than inductive and make them electron taking, with fluorine almost doing nothing due to strongest mesomeric and strongest inductive among halogens, So, halogens should take electrons away from any system if they do it in a specially conjugated system known for many resonating structures

If we have simple carbocation as shown in the chlorine and carbocation, being right next to chlorine Inductive effect must overpower resonance/mesomeric but why the opposite happens?


texts: My neighbour warned me that saltpetre (potassium (sodium) nitrate) is danger in the certain conditions. Is it possible that it can explode in my garage?


texts: Rate of nitration of C6H6, C6D6 and C6T6

texts: Why the reaction rate (nitration) of $\ce{C6H6}$, $\ce{C6D6}$ and $\ce{C6T6}$ are equal? Can anyone explain this using simple words?


texts: Why are glycosidic bonds always 1->4 in polysaccharides?

texts:
I know 1->6 bond exists too, in amylose for example, but that one seems logical, since the 6th carbon is easier to access.

I understand why the bonds originate from the hemi-acetal carbon, but I don't understand why they are 1->4.

Why not 1->3 or 1->2 ? Since there are hydroxyles on every carbons in the ring?

While I was writing this, I just had an illumination, maybe someone can confirm:

Could it be that, the formation of glucose chains in plants and animals always make use of enzymes and that it is these enzymes which, by the shape of their active site, dictates what the bonds will be?


texts:
I'm getting into alkaloid extraction from various ethnobotanicals. It is a bit frustrating trying to extract alkaloids from ethnobotanicals without good guides out there, and I wanted to make my own techniques and experiments. However, I need to know what the basic outline is for extraction. Are there any guides or basic principles I need to know?

I'm interested in extracting for example Leonurine from Wild Dagga or Mitragyna and 7-OH-Mitragyna from Kratom.

What I was looking for was Acid-Base or Liquid-Liquid extractions.


texts: Why does copper oxidise if it is considered a "noble metal"?

texts:
I'm an electrical engineer and not a chemist, so please excuse me if this is obvious.

When soft-soldering electronic parts, we’re normally taught to clean copper of oxides (like using flux and so on) before soldering. Also I’ve observed that when heating copper to $\ce{\approx 200 ^\circ C}$ copper changes colour and builds an oxide layer. So why is copper considered a noble metal? Shouldn’t it be resistant to oxidation?

If the definition of noble metal is “less oxidation” instead of “no oxidation": Does that mean that gold and silver also build a small oxide layer in the $\pu{25 ^\circ C} - \pu{200  ^\circ C}$ temperature range?


texts:
I was making pasta, and I noticed the pasta boiling over. I thought about it some more, and I realized I had no idea why this was happening. When the lid is on, the foam rises. When the lid is off, the foam dies back. Clearly there's some surfactant at work allowing bubbles to form, and the bubbles are mostly full of steam. If you remove the lid, they cool and condense down to a tiny size. This article is honestly just not specific enough. Why is the starch important?(It also happens with potatoes) How does a polysaccharide, a hydrophilic molecule, become a surfactant(if indeed it does)? Is it phospholipids from the cells that became pasta? Do starch molecules form a polymer and trap steam underneath like a balloon? Is it some kind of hybrid where bubbles are stabilized by viscosity? What's going on here?
This question on seasoned advice tries to tackle it but gets surface tension wrong(I think) so that makes me a little wary of it. Surfactants like soap reduce the surface tension, allowing bubbles to form by letting water molecules spread out into thin films. They also keep your alveoli in your lungs from collapsing. If starches increased the surface tension, wouldn't that reduce the likelihood of forming bubbles by increasing the energetic penalty? High surface tension materials act like mercury.
This answer is all over the internet but doesn't make any sense to me. You need less surface tension for bubbles, surely?
If it's just phospholipids acting as detergent, could I 'boil over' pasta in cold water with a whisk? (I tried this, you can't.)
I considered putting this on seasoned advice, but I'm not interested in how to prevent boil-over(or really any practical results), and the supplied answer there lacks scientific rigor.


texts: Why are temperature and pressure represented as the number 2 in Gibbs' Phase Rule?

texts:
In our class we are learning about Gibbs' Phase Rule; $F=C-P+2$, in which $F$ stands for degree of freedom, $C$ for number of components, and $P$ for number of phases in the system. Our professor told us that the number $2$ stood for Pressure and Temperature, but I don't understand why they are treated as constants when Composition isn't.

I must be missing something obvious, but right now I can't see what it might be...


texts: Existence of tesserane and it's properties

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Could there exist an allotrope of carbon, $\ce{C16}$ where the overall shape of the molecule is a three dimensional representation of a tesseract? And what are its (predicted if unknown/unsynthesised) properties if it does? I imagine this molecule would be highly strained, but I don't know if it shares a stability comparative to cubane's.
The only predicted properties I could find were chemicalize's calculations that it has a high solubility in water, of approximately 1200 mg/ml, and a polarizability of $\ce{17.83 A^3}$ (which has little meaning to me as I don't know typical values of polarizability).


texts:
Recently one of my relatives have fallen ill and was prescribed with some colchicine. Looking at the structure of the molecule, and with nothing much to do, I decided to put my retrosynthetic skills to the test. Here is a picture of my thought process:

Is there a better way to design a synthesis for this compound using the disconnection method.

From 11b, a Birch reduction is carried out to give the qunione 10b. A rearrangement of the ketone with methanediazonium gives 9b. A dihydroxylation with a peroxy acid and subsequent addition of water gives 8b. A double dehydration reaction with sulfuric acid, coupled with the protection of the ketone with propan-1,3-diol gives the seven-membered quinone 7b. A Heck reaction (or Ullmann reaction) with 7a with a palladium catalyst yields 6. (The protection group is thereafter labelled "PG") Friedel-Crafts acylation with ethanoyl chloride yields 5 (although on second thoughts, I should have done the acylation from 7a from the start). A Michael addition is then carried out with $\ce{BuLi}$ to lithiate the ketone to give the terminal imine 4. Since this terminal imine is unstable, a mild reducing agent converts the imine to the amine 3. The ketone is then removed by addition of dithiol and subsequently reduced by Raney nickel to form 2. Finally, a simple condensation reaction between the amine and acetic anhydride, followed by deprotection of the ketone using an acid, yields the final product colchicine, 1.


texts: How to draw a reaction coordinate diagram for SN1 mechanism?

texts:
How would you draw a reaction coordinate diagram for an SN1 mechanism with the following conditions?

each step in the mechanism (there are 2 steps) is favorable
the second step of the mechanism is the rate-limiting step

I believe the RC diagram should look some thing like this, but I am not completely sure.


texts: How do electrostatic analysers act as kinetic energy analysers?

texts:
Consider a mass spectrometer. The ions produced are accelerated across a potential V.

Now, the kinetic energy of an ion with charge q is given by qV. When it enters the analyser with electric field strength E (orthogonal to the trajectory), the radius of the trajectory is given by

r = 2K/qE, where K is the kinetic energy.

Substituting with qV, we get

r = 2V/E

The mass and charge terms disappear! So how exactly is this a kinetic energy analyser? Because as per this equation, all ions, irrespective of charge, mass and kinetic energy must have the same trajectory. Where is the flaw in my reasoning?


texts: Can fluorine act as the central atom in interhalogen compounds?

texts:
Why can't fluorine be the central atom in inter-halogen compounds?

A $\ce{F-F}$ bond is weaker than a $\ce{F-X}$ bond and thus, fluorine should be happy to form inter-halogen compounds. But, why doesn't it act as the central atom?

In my textbook, the reason given is because of the high electronegativity of fluorine atoms. But, how does that affect fluorine being the central atom or not?

If fluorine is the central atom, it can draw electrons from other less electronegative halogens and be happy. Does this lead to instability of the compound?


texts: What is the problem with my desiccant experiment?

texts:
Ok, so here's some context. For my experiment, I wanted to see which desiccant would absorb the most water in a low humidity environment (30% RH). To conduct this experiment, I placed the desiccant into a box with a saturated salt solution (Magnesium chloride) and then placed the box into an incubator to get a constant temperature. Due to practical restraints (and poor planning), I was only able to fix the mass of desiccant to 10g and not the moles of desiccant. I also left the experiment for over 12 hours.

I expected by results to be similar to results I found on the internet but it was nowhere close. My results were:

Silica Gel: 5.84% of its mass absorbed
Calcium Chloride: 7.77% of its mass absorbed
Calcium Sulfate: 6.87% of its mass absorbed
Lithium Chloride (aqueous): 3.02% of its mass absorbed

I'm not sure why my results are so inaccurate I guess. Is it because I didn't use enough desiccants, or is it because I didn't have a direct air flow? I really can't figure out why my experiment is inaccurate....


texts: Why is gold sol used for intra-muscular injection?

texts:
In my textbook it is written that gold sol is used for intramuscular injection. But, actually what is its use? Why would people use such a precious element for injection. Can other colloids be used like silver sol?

Note:I posted this question to get a deeper understanding of what is given in my text about the use of gold sol in intramuscular injection. Googling it didn't help.


texts: Does acetophenone show haloform reaction?

texts:
Although acetophenone is a methyl ketone, as it is aromatic, it is immiscible in H2O so the last step in the haloform reaction should not occur?

I couldn't find any source regarding the haloform reaction of acetophenone.


texts: Is it always reliable the bonding description of a molecular system you obtain using the NBO method? In which cases do you consider that it is necessary to have special care when analyzing the NBO results?


texts: Why does Larmor precession occur in NMR?

texts:
Larmor precession is the phenomenon that in NMR the spin (and by default also the magnetic dipole moment) of protons does not line up with the applied magnetic field but rather precesses around this direction at a certain angle.

The concept of Larmor precession confuses me for several reasons:

The analogy is made to a children's toll which precesses in the gravitational field of the earth. And then it is claimed that since these subatomic particles spin around their axis something similar happens. BUT subatomic particles don't really spin around their axis, rather the spin is a quantum property, so how does that add up?
Second of all it is stated that because of their quantum nature protons can only display 2 states, ie parallel or antiparallel to the magnetic field. But if Larmor precession takes place they are no longer parallel or antiparallel?
The calculation of the energy of the proton in the external magnetic field comes down to:

energy= spin magnetic moment x magnetic field strength

Nowhere is there a cosine to indicate the effect of the spin magnetic moment being of axis. Surely the angle between both must matter?


texts:
My attempt

In the first case:
$\ce{H+}$ adds to the $\ce{OH}$ group, giving us a carbocation. The carbocation thus formed is exceptionally stable due to back bonding. I wonder why would it go under ring expansion even though the strain is not a factor here as the ring strain in a cyclobutane ring is ~$26.3\ \mathrm{kcal/mol}$, and that in a cyclopropane ring is ~$27.5\ \mathrm{kcal/mol}$.

In the second case:
Again the $\ce{H+}$ adds to the $\ce{OH}$ group, giving us a tertiary carbocation with seven hyper-conjugating structures. Why would it go under ring expansion to give secondary carbocation with just two hyper-conjugating structures? I believe is based on ring strain in this case, as the ring strain in a five-membered ring is ~$6.2\ \mathrm{kcal/mol}$, while the ring strain in a six-membered ring is ~$0.1\ \mathrm{kcal/mol}$.

Source: Advanced Problems In Organic Chemistry, MS Chouhan, 11th edition; Chapter - Hydrocarbons (Alkenes); Question 180 in latest edition


texts: Does product induced poisoning qualify as a rate limiting step?

texts:
I have a question about whether a particular situation qualifies as a rate limiting step. I have a catalyst that under normal conditions gets poisoned when products accumulate on the catalyst surface. I interpret that as the product desorption as being a rate limiting step, but is that true?

I also thought that that a rate limiting step means that the rate of the reaction equals the rate of that step, but in reality what I see is that the initial rate in the case where the product sticks and when you can desorb the product is the same, but just that you get an abrupt halt in reactivity once the catalyst is full of product. Conversely, by tweaking the conditions where i can cause the product to desorb it just will keep that initial rate up for 10,000 times longer.

Does that still mean that product desorption is a RLS or is there a better way to describe this poisoning event?

Thanks!


texts:
We all know that the density of the nucleus is very high.

Nuclei are made up of protons and neutrons, and while protons have the same charge, they are closely packed in a nucleus. How does the repulsion between protons not break apart the nucleus?


texts:
I found this link trying to explain it: Why pyranosides do not mutarotate? however, I don't understand a step of the reasoning.
Why is it that acetalisation needs a stronger acid than for hemi-acetalisation? I was wondering why can't the mechanism be similar to the the one for the mutarotation of glucose as shown below:

Couldn't the $\ce{O}$ break the bond, and then instead of forming the aldehyde, rotate the $\ce{O-CH3}$ group and then reform the bond?


texts: How do chemical bonds increase molecular refractivity?

texts:
I see that the molecular refractivity of a compound consists of the refractivity indexes of its composite atoms and chemical bonds, and that the refractive index $n$ of a substance increases with its polarizability $\alpha$, as described with the Lorentz-Lorenz equation:

$$
{n^2-1\over n^2+2} = {4\pi N \alpha \over 3},
$$

where $N$ is the number of molecules per unit volume.

I think that the formation of a covalent bond restricts the electron cloud of its composite atoms, delaying its release of an electromagnetic wave after being stimulated by a wave of the same frequency, and decreasing the wave length of the resulting created by the interference between the two electromagnetic waves affected and unaffected by the electron cloud. In the same way, I would explain the comparatively high refractivity index of a double bond between the same atoms as a stronger restriction of the shared electron cloud, delaying the release of an electromagnetic wave later than the covalent bond.

So I want to know, is there anything fundamentally mistaken with my interpretation?


texts: Is it possible for the iodine atom in periodate ester to be octavalent?

texts:
Recently, I was reading Clayden's Organic Chemistry (2nd ed.) and I chanced upon this diagram on p. 443 (as shown below) showing an octavalent iodine in the periodate ester. I found this rather puzzling as I thought that the maximum possible valency of iodine was seven. I am well aware that bonding schemes such as the 3-centre 4-electron bonding scheme allow central atoms to make more than the number we would expect the atom to make conventionally. However, this is the first time I am seeing octavalent iodine and thus, I would just like to confirm if it is in fact, possible for iodine to be octavalent.

Reference

Clayden, J., Greeves, N., & Warren, S. (2012). Organic Chemistry (2nd ed.). New York : Oxford University Press Inc.


texts: Why are bonds ionic when the electronegativity difference between bonded atoms is greater than 1.7?

texts:
I'm learning about how to recognise whether a bond is ionic or covalent, based on the difference in electronegativity between the two bonding partners, $\Delta \chi$.

What I have now is a formula:

If $\Delta \chi = 0$, then the bond is nonpolar
If $0 < \Delta\chi \leq 1.7$, then the bond is polar covalent
If $\Delta \chi > 1.7$, then the bond is ionic

But I don't know how scientists determined that formula, the history of it and which experiment indicates that formula.


texts: What is the exact electronegativity differece value of determinig whether a compound is ionic or covalent? Is it 1.7 or 2.1?


texts: What is the mechanism for the reaction of alkenes with diborane and chloramine?

texts:
$$\ce{CH3-CH=CH2 ->[B2H6/THF][NH2Cl/H2O, Δ] Product (P)}$$
What is $\ce{Product (P)}?$

First of all, in this reaction I performed hydroboration to form an alkylborane. But I don't have any ideas what to do next. I tried a lone pair attack of nitrogen on the boron atom of the alkylborane, but what should I do next? What is the product and by what mechanism is it formed?


texts: Why so much color change in synthesis of triphenylmethanol?

texts:
In lab today, I prepared a solution of Grignard reagent (phenylmagnesiumbromide) in anhydrous ether. I then added a solution of diphenylmethanone in anhydrous ether (AKA benzophenone) to the Grignard reagent and observed a brilliant array of color change.

Immedietely when the first drops of the benzophenone were added to the cloudy grayish grignard mixture (grey color due to impurities in starting magnesium), the reaction turned a dark purple before quickly changing to a crimson red, before once again changing to a bright pink. As more benzophenone was added, the reaction mixture changed, once more, to a milky white color and promptly hardened.

I understand the white final color and hardness is due to formation of my intended product: triphenylmethoxide magnesium salt...

But WHAT in the world was happening in that reaction with all those fantastic color changes?


texts: On Electrochemical Cells and Salt Bridges

texts:
We're studying the topic Electrochemistry at school now, and I've got a few doubts regarding electrochemical cells and salt bridges.

What I am going to do is listing out (point-wise) what I understood from class, and then pose my questions (in bold). The logic behind listing out what I understood about the topic beforehand? I've a very strong feeling I'm harboring some serious misconceptions regarding the topic, so if I list out what I do know, then hopefully someone can alert me to an incorrect point, and also correct it.

LHC - Left half cell (contains the anode, which is negatively charged in electrochemical cells)
RHC - Right half cell (Contains the cathode, which is positively charged in electrochemical cells)

During the course of the reaction,

In the LHC, metal atoms of the electrode release their electrons to the anode and enter the solution as positive ions.
The positive metal ions, under the influence of the negatively charged anode, accumulate around the anode, resulting in a Solid-Liquid Junction. The Solid-Liquid Junction is also known as the Helmholtz Double Layer.
Similarly in the RHC, negatively charged ions (formed from the electrolyte solution) accumulate around the cathode, resulting in another Solid-Liquid Junction.
It is the potential difference between the LHC and RHC Solid-Liquid Junctions potentials that gives rise to the emf which results in the flow of electrons (electric current) from the LHC to the RHC via the metal wire that connects their corresponding electrodes.
However, as the reaction proceeds, the quantity of positive and negative ions builds up (in the LHC and RHC respectively). So much, that these ions under their mutual attraction, override the force of attraction that binds them to the electrodes and accumulate at the porous asbestos partition that separates the two half cells. This is called the Liquid-Liquid Junction. The formation of the Liquid-Liquid Junction comes at the cost of the Solid-Liquid Junctions, which disintegrate.

As the Liquid-Liquid Junction potential doesn't involve the electrodes, it cannot set up a potential difference across them, therefore no current flows along the wire. This is why an electrochemical cell stops generating current after some time has elapsed.
This problem can be overcome by use of a salt bridge, which in effect, neutralizes the net charges on either side of the asbestos partition, thus releasing the ions back into the solution. These ions are once again attracted by the electrodes, and the two Solid-Liquid Junctions are re-established. So current once again begins flowing through the wire.

I'd appreciate it if anyone could proof-read those points. Also I have doubts whether the Solid-Liquid Junction can also be called the Helmholtz Double Layer.
I made these points in class, and I let my teacher go through them, and he's in agreement with them, so I don't think this is a case of talking down the points wrong, at least not with respect to what was mentioned in class.

Now I asked my teacher, Q1: Screw the partition. Why not simply have the two half cells in separate compartments kept at a distance from each other, instead of using a 'partial' barrier like the porous asbestos partition? Wouldn't that eliminate the possibility of a Liquid-Liquid Junction being formed?

His answer: Well they're ions buddy, so they'll attract each other anyway and accumulate at the sides of the compartment, after all....they're charged. So even though that wouldn't result in a Liquid-Liquid Junction, there still wouldn't be any potential difference across the electrodes, so nil current. Plus, if you separate the compartments like that, it'll just take up space;  compact electrochemical cells are more convenient to use.

Q2: Is my teacher entirely right here?

And yet again, Q3: Are all the points I've mentioned correct?


texts: What happens when butane and methane both absorb 100 J of heat?

texts:
Two cylinders, one containing 1 mole of $\ce{C4H10}$ gas at $\pu{1 atm}$ and the other containing 1 mole of $\ce{CH4}$ gas at $\pu{1 atm}$, are at $\pu{288 K}$.  If each gas absorbs $\pu{100 J}$ of heat under conditions of constant volume, which of the following is true?
  (a) The temperature of the $\ce{CH4}$ increases more than the temperature of the temperature of the $\ce{C4H10}$.
  (b) The internal energy of both the $\ce{CH4}$ and the $\ce{C4H10}$ decreases.
  (c) The heat capacity of the $\ce{C4H10}$ is less than the heat capacity of the $\ce{CH4}$
  (d) The entropy of both the $\ce{CH4}$ and the $\ce{C4H10}$ decreases.
  (e) The heat transferred to the $\ce{C4H10}$ is greater than the heat transferred to the $\ce{CH4}$.

The correct answer is (a). I am trying to eliminate answers, but I seem to get stuck.

We know that (b) is clearly false as we've added heat and no work is done, therefore the internal energy for both gases must increase. Likewise, (d) is false as the entropy should increase as the molecules have more heat and become more disordered. Finally, (e) is incorrect as we transferred $\pu{100 J}$ of heat to both systems.

But here is where I get stuck. I can't seem to eliminate (c) from just the information given.


texts: Why are noble gases used in "neon" lamps

texts: Neon lamps are lamps that contain noble gases... They light due to the presence of energetic levels for electrons (according to the definition of it in books). But I don't understand yet why noble gases are used in such lamps. Any help please?


texts: Hydrogenation at atmospheric pressure in amateur environment

texts:
I was planning on doing some small scale hydrogenation practicals at atmospheric pressure (probably from Vogel) and ran into a couple of questions. I will be using the "balloon method" (described in Procter's Advanced Practical Organic Chemistry book) as I consider it an easier technique for small scale reactions than constructing a Brown hydrogenation apparatus. Note that I'm working in an amateur environment (i.e. my home lab which does not have a fumehood). Now for the questions:

What rule of thumb can be used to determine the amount of catalyst (in these cases $\ce{Pd/C}$) needed per mole of hydrogen used (I suppose these two variables are depending on each other)?
There are different types of $\ce{Pd/C}$ out there: 3%, 5% or 10% $\ce{Pd}$ by weight, with or without a variable amount of added $\ce{Pb}$, different solvents (mostly I see is water) and also there are different bases available, not just palladium on carbon. I understand that $\ce{Pb}$ is added to poison the catalyst such as with Lindlar catalyst, but if total reduction is required then why would this be necessary? Also how would I decide between 3%, 5% or 10% $\ce{Pd}$ by weight?
What is an effective method for generating the hydrogen to fill the balloon with? I suppose that normally a pressurized hydrogen tank would be used for this, but I find this overkill for the reaction I'm planning. Furthermore, the use of  pressurized hydrogen tanks is not quite without danger and I'm not trained to handle them safely.
Why would it be required to flush the reaction mixture with an inert gas after the hydrogenation has completed? I understand that this is necessary because the dissolved hydrogen gas can ignite and possibly explode when, while filtering the catalyst, the catalyst spontaneously ignites (e.g. when the catalyst is not suspended enough and direct contact with the atmosphere is possible). However, why is an inert gas advised? What is wrong with ordinary air?
What is the function of Celite when filtering the catalyst?
How many times can the $\ce{Pd/C}$ catalyst be reused? How would you spot whether or not your catalyst has become too poisoned to be successfully used in hydrogenation?


texts: Does the way a reaction with gas moles shifts depend on Q or number of moles on either side of the reaction?

texts:
Given a container with the reaction $\ce{C2H4{(g)} + HCl{(g)} -> C2H5Cl{(g)}}$, if we inject $\ce{C2H5Cl{(g)}}$ to the container, what will happen?

I thought of this in two different ways and got two different answers:

If we inject $\ce{C2H5Cl{(g)}}$, $Q>K$ so reaction will shift to the left, leading to the formation of more $\ce{C2H4{(g)} and HCl{(g)}} $.
Injecting  $\ce{C2H5Cl{(g)}}$ also increases the pressure I suppose, and if you increase pressure, the reaction will shift to the side with the least moles of gas. In this case, it will shift right, forming more $\ce{C2H5Cl{(g)}}$

Which answer is correct?


texts: Clash between thermodynamic and kinetic processes

texts:
I have often come across reactions where kinetic and thermodynamic processes give completely different outputs. I was told that in such cases check temperature, if temperature controlled, then take thermodynamic product otherwise if reaction is very fast (not temperature controlled) then consider the kinetic product.

I was also told that if there is a case where you can't decide whether it is temperature controlled or speed controlled, then always take the thermodynamic product.

My question is: Why will thermodynamic processes have an upper hand in the latter case?
CH2CHC(CH2)CH3 what MAJOR product does it produce on giving 1 equivalent HBr?


texts:
Rotation around the double bond of azobenzene is restricted because it would distort the P orbital overlap between the nitrogen atoms. However, in the $n \rightarrow \pi^*$ excited state ($S_1$), the rotation is no longer hindered and it can isomerize.

I don't understand why this is the case. You are taking an electron from the non-bonding orbital, and moving it into the pi-antibonding. However, the $\pi$-bonding is still present, so I see no reason why the rotation would be unrestrained. Is it something about the interaction between the electrons in the $\pi^*$ with the $\pi$ that weakens the double bond? And if so, how?


texts: Reaction of anisole and succinic anhydride in presence of aluminium chloride

texts:
Predict the structures of the intermediates/products in the following reaction sequence:

In the first step, I know that aluminium chloride  is playing some role,  as otherwise hydronium ion would have reacted with succinic anhydride  to give succinic acid.
I thought of the following two possibilities:

Friedel Crafts: But till date, I have only seen Friedel Crafts type reactions and have not seen aluminium  chloride complex with either acid or anhydride. I could also not find it on Google.

Chloride formation: But I have also never seen aluminium chloride forming a chloride in reaction with anhydride. I am not sure if it does that, does it?

So, what is the reaction mechanism for the formation of (A)?
Source: Joint Entrance Exam (JEE) 1996 India


texts: Calculating Air Density and Effect of Air Composition

texts:
I have to calculate density of atmosphere, assuming that it is:
79% : N2
21% : O2

Does the percentage of gases affect the answer, and how can we find the density with such little information?


texts: What are the subfields of chemistry that work very closely with biology?

texts:
Background information:
I'm not sure if this question belongs here; but i'll risk the down-votes to ask it.

I'm currently doing an undergraduate program, and it's in chemistry. I am torn between doing chemistry and biology and ideally the nicest compromise would be biochemistry. However I have a horrible ineptitude for biochemistry.

My question is, what subfields of chemistry work very closely with biology?


texts: Are there any dangers while handling cobalt dichloride?

texts:
I use a desiccant named Drierite to remove water from air in experiments. It is composed of $98\%\ \ce{CaSO4}$ and $2\%\ \ce{CoCl2}$. Every once in a while the Drierite gets saturated with water vapor and it must be dried out so it can be used again.

According to the manufacturer you put the chemical in a lab oven, set to $230\ ^\circ\mathrm{C}$ until it turns blue. The cobalt dichloride $\ce{CoCl2}$ is an indicator that turns blue when dry and pink/purple when saturated. One of my coworkers noted that cobalt dichloride is a carcinogen, and now he wants me to stop heating it in the lab oven because of the vapor it is giving off that we are breathing.

Could cobalt dichloride give off anything that would cause a person harm espcially when heated to $230\ ^\circ\mathrm{C}$?

I have looked at the safety data sheet but it is not very helpful. It does say that cobalt dicloride is a carcinogen but not how or when it is transferred.


texts: Positive vs. negative heat of solution confusion

texts:
Given that I have absolutely zero formal (or informal) education in chemistry (sorry about that), I'm struggling to get my head around what appears to be repeated confusions of the term "heat of solution" with regards positive vs. negative. As a specific example, the Wikipedia entry on Erythritol states:

  Erythritol has a strong cooling effect (endothermic, or positive heat of solution) when it dissolves in water

However, many other sources, including a number I found via Google Books suggest that Erythritol has a negative heat of solution. For example, this table extract from Food Science, an Ecological Approach:

  Erythritol: Noncaloric (0.2 kcal/g), high digestive tolerance, zero glycemic index, does not promote tooth decay, good heat and acid stability, high negative heat of solution.

This is frustrating as I'm trying to find something that has the opposite heat of solution to counteract erythritol's cooling effect, but since many sources seem to contradict each other, I'm struggling to find what I'm looking for.

Which is correct? Or am I using ambiguous terminology?


texts: Is Blue Silica Gel more harmful than the Orange ones?

texts:
I am currently searching for a portable dehumidifier but notice that most of them come with a indicator that actually using the Blue Silica Gel, which I believe that it may contain Cobalt Chloride.

So, I would like to ask,
(1) if that is the case, would the portable dehumidifier become a harmful product?
(2) would an Orange Silica Gel contain other harmful chemical that is currently not found?


texts:
Why is that carbonyl bonds are stronger than those of alkenes? It's a basic question but I've never really thought much about it.
I've read several times that carbonyl bonds are shorter and you need to apply a higher amount of energy to break them. Why is that so?

Is it due to the electronegativity of oxygen, which pulls the bonding electrons near it, thus attracting the carbon as well?


texts: Is water a possible fuel for jet engines?

texts:
Jet engines can run on almost any fuel, and the operating temperatures of modern jet engines' hottest sections are anywhere between 3000 and 3150 degrees F (1648 and 1732 degrees Celsius). Does that mean that a hydrogen on-demand system could work on modern jets?

Water is pumped and heated first by the exhaust section, then directed towards the hotter sections of the engine (when hot enough to not cause cooling and lower engine efficiency) where it's broken down into hydrogen and oxygen at a heat above 1472 degrees F (800 degrees Celsius), then those gases are pumped into the engine for combustion.

The advantages are that firstly, water is abundant and therefore cheap. Even sea water could be used because at those temperatures it's easy to design a system that would get rid of the impurities that would otherwise corrode critical engine parts.

Secondly, it would save on manufacturing costs given that non-heat critical parts in the exhaust section would not need to be made of sophisticated and expensive materials and alloys given the cooling effect of water.

Thirdly, the costs of the fuel weight would be reduced given that the energy density of hydrogen is twice that of fossil fuels, so less would need to be carried. And most importantly, the environment problem would be solved in aviation given that there would be little or no carbon dioxide emissions.


texts: FMO analysis of the [3,3] Sigmatropic reaction regarding geometry. Is it accurate?

texts:
While studying the reasons behind the stereospecificity of [3,3] Sigmatropic reactions, I ran into an image portraying both possible transition states for the reaction: The Chair TS and Boat TS. The complete FMO orbitals were only drawn for the Chair TS and the final geometries of the products was shown for both transition states:

I find it a little bit hard sometimes to visualize the three dimensional transitions that result in a specific configuration, so I tried to complete the FMO analysis with the orbitals for the Boat TS and to draw the sigma-bond rotations necessary to create constructive overlap between the lobes. I came up with the following:

On the Chair TS we see the σ* shaded lobe is perpendicular to the shaded lobe of the π HOMO from the double bond next to it (having a 3D model would make it easier to see because in the drawing they seem aligned, but they are actually perpendicular). The sigma-bond would then have to rotate 90º inward for effective constructive interaction, "throwing" the R-Group outwards and resulting in the E-configuration seem in the product. The other σ* lobe also rotates 90º in the same direction (I forgot to draw the arrow there, but it would be the same as the one beside the shaded lobe), but for some reason this rotation result in the regular "cyclic-like" geometry for that double bond (Z-configuration?).

If it wasn't hard enough to visualize it on the Chair TS, it gets worse on the Boat TS. I came up with the orbital configuration as seem in the image. First, I got a little confused about the σ* shading, because the whole premise for the shading had to do with constructive overlap where the double bonds would occur. But there I had to draw opposite phases on the lower part. That, I believe, is because initially they were aligned with the same phases (as in the Chair TS), but the conformation twisting threw the constructive phases in opposite directions. Anyways, to reach constructive overlap the sigma-bond next to the substituted carbon would have to rotate close to 90º counter-clockwise, while the other sigma-bond would have to rotate almost 180º. That explains why this transition state is so unfavorable, but I'm still struggling a bit with the geometry. The 180º rotation sounds like it would result in the unsubstituted double bond pointing out of the "cyclic-like" shape as seem in the product. But I can't clearly see how the 90º rotation throws the R-Group inward in a Z-configuration geometry. Instead, I came up with another orbital configuration possible that might be the correct one:

In that orbital configuration the sigma-bond of the substituted carbon wouldn't have to rotate, and we would have the R-Group pointing inward like in the product.

Which orbital configuration is correct, if any? Is my reasoning about the sigma-bond rotations and the resulting products geometry correct? Do you have any tips when it comes to visualizing geometrical issues on more complicated molecules?


texts: What are the disadvantages of using the InChI format?

texts: What are the disadvantages (if any) in producing and using the InChI format of chemical compound representation in chemoinformatics? Are there any particular problem one can face when using InChI?


texts: Convoluted explanation of different types of Raman scattering

texts:
I am currently studying the textbook Surface-Enhanced Raman Spectroscopy -- Bioanalytical, Biomolecular and Medical Applications by Marek Procházka.
I just read this passage from chapter 2:

Rayleigh scattering arises when the energy of the molecular system both before and after the scattering process is the same ($\hbar \omega_{\text{s}} = \hbar \omega_{\text{inc}}$). The occurrence of inelastic light scattering can be explained by classical theory in terms of a modulation of the incident radiation $E_{\text{loc}}(\omega_{\text{inc}})$ by a vibrating molecule with frequency $\omega_{\text{vib}}$. Raman frequency can be smaller $\omega_{\text{inc}} - \omega_{\text{vib}}$ or larger $\omega_{\text{inc}} + \omega_{\text{vib}}$ than that of the incoming photon $\omega_{\text{inc}}$. When the incident radiation is shifted to a lower frequency (lower energy), the scattered light is called Stokes shift. In this type of scattering the energy is transferred to the vibrational mode of the molecule which ends up in a higher vibrational energy state. Similarly, when the incident radiation is shifted to a higher frequency (higher energy), the scattered light is called anti-Stokes shift. In this type of scattering the energy is transferred from a vibrationally excited molecule, which ends up in a lower vibrational state after the scattering event. The scattering process when an intermediate “virtual state” does not correspond to a real energy level of the molecule is called normal Raman scattering (NRS)$^2$.
$^2$ The term “RS” is often used for RS under nonresonant (normal) conditions, term “normal RS” (or sometimes classical RS) is used to distinguish it from resonance RS under resonant conditions. Note that there is also the case of preresonant RS.

In particular, it is this part that I don't understand:

$^2$ The term “RS” is often used for RS under nonresonant (normal) conditions, term “normal RS” (or sometimes classical RS) is used to distinguish it from resonance RS under resonant conditions. Note that there is also the case of preresonant RS.

This is written so convolutedly that I do not at all understand what it is saying, nor can I distinguish between the different types of RS (Raman scattering) that it is referring to. I would greatly appreciate it if people would please take the time to clarify this.


texts: Hydroxy Protecting Groups that are not Cleaved Under Acidic Conditions

texts: I am currently designing a synthesis requiring the use of hydroxy protecting groups. The problem I am having is that the protecting group must be able to survive highly acidic conditions. I would have loved to use a TMBS protecting group since it can withstand LAH, lewis acids, and strong base; however, not acidic conditions. I really do not want to have to use a t-butyl ether protecting group, as its removal requires very harsh conditions. I will provide a scheme indicating all of the conditions I have proposed so far (this scheme is just a rough draft, so there are a few reagents that I have changed to be compatible with the reaction, but the general conditions should remain the same). Does anyone know any protecting groups that would match this criteria? I am only referring to replacing the TMBS protecting group on the second intermediate.


texts: Nitrobenzene and other monosubstituted benzenes 1H vs 13C NMR assignments

texts:
The reported 1H NMR spectrum for nitrobenzene has three signals corresponding to H2/H6, H3/H5 and H4, respectively. The signals (ppm) appear at 8.25 (H2/H6), 7.71 (H4), and 7.56 (H3/H5). This is, the ortho protons are the most deshielded, followed by the para, and, finally, the meta. This makes sense when rationalizing the inductive effect of the nitro group by resonance, which makes the ortho and para carbons deficient in electrons, hence deshielding them. Furthermore, the ortho protons are closer to the nitro group, hence they are the most deshielded of all, so the from more to less deshielded: ortho > para > meta.

However, the reported 13C NMR spectrum shows signals at 148.3 (ipso), 134.7 (para), 129.4 (meta), 123.5 (ortho). So from more to less deshielded, the positions are now ipso > para > meta > ortho. Why is the trend so different for the carbon-13 NMR?

Also the trends for other monosubstituted benzenes are:

Benzonitrile. 1H NMR: ortho > para > meta; 13C NMR: para > ipso > ortho > meta. Here the trend changes a bit as well, but now only between ortho and para.

Benzaldehyde. 1H NMR: ortho > para > meta; 13C NMR: ipso > para > ortho > meta.

Aniline (EDG). 1H NMR: meta > para > ortho; 13C NMR: ipso > meta > para > ortho. Here the trend is inverted, but why would the para still be more deshielded than the ortho as seen in all the other cases?


texts: Significance of Temperature in Gibbs Free Energy

texts:
Why is it important to know the temperature of both reactants and products of a reaction in order to determine change in the Gibbs free energy of the reaction?

Is it because temperature has an effect on both enthalpy and entropy? Or is it because of some other reason I am missing?

Any help on this would be great. Thanks!


texts: What are the units for m in the average kinetic energy formula?

texts:
For the equation $E_k=\frac{1}{2}mu^2$ what does the $m$ variable represent?

I would say mass but the textbook does not say explicitly that it is anything.


texts: Find H3O+ of weak acid salt solution which compose of solute that can gain and give protons

texts:
Find $[\ce{H3O+}]$ of 0.100 M $\ce{NaHCO3}$ ($K_{\ce{H2CO3},1}=4.45×10^{-7}$, $K_{\ce{H2CO3},2}=4.7×10^{-11}$)

My work is: $$\ce{HCO3- + H2O<=>H2CO3 + OH-}$$

Initial: $[\ce{HCO3-}]$ = 0.100 M, $[\ce{H2CO3}]$ = 0, $[\ce{OH-}]$ = 0
Change: $[\ce{HCO3-}]$ = -X, $[\ce{H2CO3}]$ = +X, $[\ce{OH-}]$ = +X
Equilibrium: $[\ce{HCO3-}]$ = 0.100 - X, $[\ce{H2CO3}]$ = X, $[\ce{OH-}]$= X

$K_{b2}=\frac{Kw}{K_{a1}} = 2.25×10^{-8}$
$K_{b2} < 10^{-3}: 0.100 - x = x$
$K_{b2} = \frac{x^2}{0.100}$
$X = [\ce{OH-}] = 4.47×10^{-5}$ so $[\ce{H+}] = \frac{10^{-14}}{[\ce{OH-}]}$, $[\ce{H+}] = 2.11×10^{-10}$

And the second equation is
      $$\ce{HCO3- + H2O<=>CO2 + H3O+}$$
For this equation $K_{a2}=4.7×10^{-11}$
So when I compared $K$ value between both of these equation, I will get $K_{b2} >> K_{a2}$ (more than $10^3$ times). So I think increase $[\ce{H3O+}]$ which occur or $[\ce{CO2}]$ can be ignored. So my answer $[\ce{H3O+}]$ is equal to $2.11×10^{-10}$ M.

But the solution in my book is:
From the formula:
$[\ce{H3O+}]= \sqrt{\dfrac{K_1 K_2 × [\ce{NaHCO3}] + k_1 k_w}{[\ce{NaHCO3}] +K_1}}$

$[\ce{H3O+}]=4.6×10^{-9}$ (solution answer)

Do I approximately second equation false or $K$ value is false or another thing?


texts: Heat effect on diluting concentrated NaOH solution

texts:
I am an engineer in water treatment and have a chemistry question. In water treatment we dose $32\%$ sodium hydroxide solution for $\mathrm{pH}$ adjustment and there is a concern that our dosin lines must be $100\%$ dry before introducing the $\ce{NaOH}$ solution. This is the problem as they have been pressure tested with water and there is water residue in them.
Will $32\%$ sodium hydroxide solution react violently with cold water? It is my understanding that the reaction only occurs when solid sodium hydroxide (lye) is dissolved in water and since my $\ce{NaOH}$ is already in solution then this reaction will not take place. Is this correct?


texts: Why would T1 relaxation time change ~20 fold between solvents for the same substance?

texts:
I have a simple, completely conjugated pyridinium salt with MW of ~300 g/mol. The molecule consists of regular non-labeled atoms (only C, H, N).

If the 1H T1 relaxation time for this molecule is measured in DMSO-d6 the T1 values of all of the protons are within the expected range (9 sets of protons with T1 values of 1.4-2.1 s).
However if the 1H T1 relaxation time for exacty the same molecule is measured in CDCl3 the relaxation times differ up to 20 times (9 sets of protons with T1 values of 0.04-1.9 s). The 1H relaxation is especially fast at the pyridinium ring (2 sets of pyridinium ring protons with T1 values of 0.04 and 0.07 s and further removed protons from the pyridinium have T1 values of 1.5-1.8s).

From what I have read in the literature the relaxation times usually differ up to 2-fold.
Any ideas why this is the case?


texts: How does a spectrophotometer measure absorbance based on the intensity of detected light?

texts:
We know that $\displaystyle A = -\log\frac{I_t}{I_0}$, where $I_0$ is the intensity of light without a sample absorbing, and $I_t$ with the sample. For determining the absorption $A$, we need both $I_t$ and $I_0$, but how does a spectrophometer detector measure $A$ knowing only $I_t$ ? (The detector is placed after the sample in the optical path, so it does not measure $I_0$ in front of it.)
Does the detector measure $I_t$ or the ratio $I_t/I_0$ ?


texts:
When looking up names for simple organic molecules, the idea of a preferred IUPAC name (PIN) often comes up.

My understanding was that the PIN was meant to provide a unique and unambiguous name for a given molecule based upon strict applications of the IUPAC guidelines for nomenclature.

Whilst some PINs are clearly applications of these formal IUPAC guidelines, other PINs are trivial names. To give some examples:

Acetic acid (PIN, but trivial name) rather than ethanoic acid (systematic
IUPAC name)
Propan-2-one (PIN and systematic IUPAC name) rather than acetone (accepted but trivial)
Phenol (PIN, but trivial name) rather than benzene (systematic IUPAC name)

Clearly most people still refer to these molecules as acetic acid, acetone, and phenol; but it seems arbitrary that some trivial names are also the PIN whilst others are not (that is not to say that the other names are forbidden, as pointed out in the comments, with reference to P-10 of the recommendations).

  Why do we need the PIN, and why does it not always conform to the strict application of the IUPAC guidelines?


texts: Why does rdkit's `AllChem.ReactionFromSmarts.RunReactants` return a tuple of tuples?

texts:
In rdkit, the function AllChem.ReactionFromSmarts.RunReactants returns a tuple of tuples. Does anyone know what the two dimensions are for? From the (admittedly few) examples I've seen, the inner tuples are always just one molecule.

The docstring says,

RunReactants( (ChemicalReaction)arg1, (tuple)arg2) -> object :
apply the reaction to a sequence of reactant molecules and
return the products as a tuple of tuples

example:

from rdkit import rdBase, Chem
from rdkit.Chem import AllChem, Draw
rxn = AllChem.ReactionFromSmarts('[c:1][c:2][c:3]>>[c:1][c:2]([F])[c:3]')
m = Chem.MolFromSmiles('c1ccccc1')
ps = rxn.RunReactants((m,))

((<rdkit.Chem.rdchem.Mol at 0x10be03818>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef92f0>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef9a28>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef99d0>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef9768>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef9920>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef96b8>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef98c8>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef95b0>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef9710>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef9558>,),
 (<rdkit.Chem.rdchem.Mol at 0x10bef9ad8>,))

The reason I ask is that I want to put the products into a pandas dataframe (already accomplished) and label the columns and indices according to the intended scheme.


texts: Which salts give the sodium carbonate bead test?

texts:
Apart from the borax and the phosphate bead tests, there's also this one.
It's  done by heating the white bead of sodium carbonate and the salt with potassium nitrate; green and yellow colours indicate the presence of manganese and chromium respectively.
I've only seen these two examples for this test. Are there any more?


texts: IUPAC name of trisubstituted benzene ring

texts:
What is the IUPAC name for the compound shown below? I named it as 6-Bromo-3-hydroxy benzonitrile according to the numbering scheme in 1b, since the priority order is $\ce{-CN} > \ce{-OH} > \ce{-Br}$.

However, the answer given in the book is 2-Bromo-5-hydroxy benzonitrile, which implies the numbering scheme in 1a. Please help me to identify whether my answer or the book's answer is correct.


texts: How can there be an enthalpy of formation for gaseous water?

texts: Under standard conditions( 1 bar and 298.15 K), water will be in the liquid state. So how can you find the enthalpy of formation for gaseous water at standard conditions(as found in the back of all chemistry textbooks)?


texts: Does a sulfuric acid/nitric acid mixture dissolve PTFE (ie. teflon)?

texts:
In our lab, we commonly use a mixture of sulfuric acid and nitric acid to clean borosilicate glassware.  I'd like to clean some PTFE pieces in there, too, but not sure if they will dissolve or not.

Does anyone have any first-hand experience with this, and know whether or not a sulfuric acid/nitric acid mixture dissolve PTFE?


texts: Did O₄ turn out to explain why liquid oxygen appeared to defy Curie's law? If not, what does?

texts:
Wikipedia's Liquid Oxygen says:

The tetraoxygen molecule ($\ce{O4}$) was first predicted in 1924 by Gilbert N. Lewis, who proposed it to explain why liquid oxygen defied Curie's law. Modern computer simulations indicate that, although there are no stable $\ce{O4}$ molecules in liquid oxygen, $\ce{O2}$ molecules do tend to associate in pairs with antiparallel spins, forming transient $\ce{O4}$ units.

The paragraph is a bit ambiguous and doesn't rule out that the "transient $\ce{O4}$ units" do not explain why "liquid oxygen defied Curie's law", so I'd like to ask:
Question: Did $\ce{O4}$ turn out to explain why liquid oxygen appeared to defy Curie's law, at least in some way? If not, or not completely, what does?


texts: In situ preparation of Potassium Tert-Butoxide

texts:
I am attempting to prepare potassium tert-butoxide. I was going to suspend anhydrous toluene and anhydrous tert-butanol, dissolve (reflux) the potassium metal (pure), then distill the excess tert-butanol as a benzene azeotrope.

2 questions.

The metal comes stored in mineral oil. Should I rinse it in toluene to get the oil off?
How will the presence of oxides effect the reaction (if at all). If so, how can I mitigate this?


texts: Openbabel is not converting Gaussian Z-matrix

texts:
I ran into an issue when OpenBabel (a great and extremely useful problem) could not convert my custom-generated Gaussian Z-matrix to XYZ format. The problem is that probably major flaw of OpenBabel are very terse error messages (mostly just "0 molecules converted", and even with ---errorlevel 25 option I got only:

==============================
*** Open Babel Audit Log  in ReadChemObjectImpl
  OpenBabel::Read molecule Gaussian Z-Matrix Input
==============================
*** Open Babel Audit Log  in Clear
  Ran OpenBabel::Clear Molecule
==============================
*** Open Babel Audit Log  in ReadChemObjectImpl
  OpenBabel::Read molecule Gaussian Z-Matrix Input
==============================
*** Open Babel Audit Log  in Clear
  Ran OpenBabel::Clear Molecule
0 molecules converted

). Some other file was converting just fine, with no obvious differences between their contents! I spent a long time trying to understand what is wrong with the second file, but to no avail.

The file which converts without any problem:

# This is a dummy route line, required for OpenBabel for the conversion

   This molecule contains 26 atoms.

0 1
C
C   1    1.4141
C   2    1.3856  1    117.29
C   1    1.4077  2    121.06  3    -1.09
C   4    1.4088  1    121.27  2    2.37
C   3    1.4075  2    121.95  1    -0.93
C   3    1.5118  2    128.77  1    -176.79
C   7    1.4378  3    105.16  2    175.55
C   6    1.5156  3    108.80  2    -176.32
N   8    1.4317  7    122.53  3    -177.58
C   10   1.3629  8    120.12  7    -146.43
C   11   1.3942  10   120.44  8    -178.97
C   12   1.4024  11   119.82  10   -3.12
C   13   1.4110  12   118.94  11   1.63
C   10   1.3704  8    119.11  7    32.69
O   7    1.2445  3    125.27  2    -1.31
O   9    1.2448  6    124.96  3    -179.37
H   2    1.0882  3    121.72  6    -181.70
H   4    1.1010  1    119.57  2    -178.73
H   5    1.0951  6    121.12  3    179.30
H   11   1.0928  10   115.87  8    1.70
H   12   1.0908  11   118.95  10   178.60
H   13   1.0963  12   120.77  11   182.82
H   14   1.0959  13   121.94  12   -180.61
H   15   1.0855  10   115.78  11   178.99
H   1    1.0923  2    119.78  18   0.45

The file which fails to convert:

#T HF/3-21G Opt Integral(Grid=SG1)

  H2O2 H2O2 GeometryOptimization GeomOpt GeometryOptimization 1

0 1
O
H   1    1.0
O   1    1.4  2    105.0
H   3    1.0  1    105.0  2    176.0
O   1    5.0  2    90.0   3    90.0
H   5    1.0  1    105.0  2    52.5
H   5    1.0  6    105.0  1    178.0

This is OpenBabel version 2.4.1 on Debian 10.

P.S. I sincerely don't know whether this question belongs better to the Chemistry StackExchange or to other forum, but I presume the question might appear to be useful for someone someday.


texts: How to identify if a material is perovskite or not?

texts:
This is more of a materials science question, but I believe many of you have referred NIST Inorganic Crystal Structure Database (ICSD) database.

I am collecting a database of perovskite materials and got a little bit confused on how the structure type is defined in the ICSD website.

Please find a screen shot of ICSD results on lead zirconate titanate (PZT) material.

Here, when mole fraction $\ce{Zr}=0.52$, the 'Struct. Type' is defined as $\ce{FeNbPb2O6}$. Does it mean that PZT material when $\ce{Zr}=0.52$ is not perovskite? And in general if the column 'Struct. Type' does not start with 'Perovskite,' does that mean the material is not perovskite?

Finally, sometimes I see the structure type named 'Elpasolie' or $\ce{LiNbO3}$ (disordered). Are these also perovskites? (or double perovskites?)


texts:
You need to prepare $\pu{250.0 mL}$ of an aqueous solution of ethanol in the concentration will be $\pu{0.500 mol L-1}$. You have $\pu{100 mL}$ of a commercial solution of ethanol in water $(35.0\% \,V/V)$ available. The density of ethanol (pure) under these conditions is $\pu{0.7893 g mL-1}$ and that of water is $\pu{0.9970 g / mL}$.
1.What volume (in $\mathrm{mL}$) will you need to withdraw to prepare this solution?
2.What is the mole fraction of ethanol in the resulting solution?

Answer to (1)
We can prepare $\pu{250 mL}$ of $\pu{0.5 mol L-1}$ solution of ethanol by diluting $\pu{20.85 mL}$ of $35 \%$ $\ce{C2H5OH}$ (density $\pu{0.7893 g/mL}$) with distilled water to a volume of $\pu{250 mL}$.
The dilution is therefore made by adding $\pu{229.15 mL}$ of water.
However, the volume of a liquid obtained by mixing measured volumes of different solutions is not always precisely the sum of the component volumes.
Calculation
Source (B): $35 \%$ solution of $\ce{C2H5OH}$ (density $\pu{0.7893 g/mL}$)
The molar concentration of a solution of a chemical species A is the number of moles of that species contained in one litre of the solution (not in one litre of the solvent).
$$C(A) = \pu{0.5 mol/L}$$
$$\text{Molar concentration} = \frac{\text{Density} \cdot \text{Weight percent} }{ 100\cdot \text{Molecular weight}}$$
$$C(B) = \frac{d(B) \cdot w(B)}{100 \cdot M(B)}$$
$$C(B) = \frac{\pu{789.3 g/L} \times 35 \%}{100 \times \pu{46.0684 g/mol}}$$
$$C(B) = \pu{5.99662675499909 mol/L}$$
The number of moles of solute in the diluted solution must equal the number of moles in the concentrated reagent.
\begin{align}
V(A) \cdot C(A) &= V(B) \cdot C(B) \\
V(B) &= \frac{V(A) \cdot C(A)}{C(B)} \\
V(B) &= \frac{\pu{0.25 L} \times \pu{0.5 mol/L}}{\pu{5.99662675499909 mol/L}} \\
V(B) &= \pu{2.08450525782339 \times 10^{-2} L} \\
V(B) &= \pu{20.85 mL} \\
\end{align}
Answer to (2)
We have
\begin{align}
C(B)  &= \frac{\pu{0.125029667842 mol}}{\pu{20.85 mL}} \\
&=\pu{5.99662675499909 mol/L}
\end{align}
Now we have to add $\pu{229.15 mL}$ of water to $\pu{20.85 mL}$ of commercial solution of ethanol to make it $\pu{250 mL}$.
$\pu{229.15 mL}$ of water has a mass of $\pu{229.15 g}$. This means that there are $\pu{12.7197 mol}$ water because the molar mass of water is $\pu{18.0153 g}$
\begin{align}
\text{Mole fraction of ethanol}&= \frac{\text{Number of moles of ethanol}}{\text{Number of moles of solution}} \\
&=\frac{\pu{0.125029667842 mol}}{(\pu{0.125029667842 mol} +\pu{12.7197 mol}}\\ &
= \pu{0.009734 mol}
\end{align}

Are my answers to both questions correct? If they are incorrect, where am I going wrong?


texts:
What does the value of the pH meter mean when there aren't any hydronium ions in the substance being tested?
How does the pH meter show a value which fluctuates as non-aqueous solvents are being tested? I thought that the pH meter only measured hydronium ions. Is there any way that this value actually means something in terms of acidity and basicity?


texts: How to calculate the average quadratic velocity of carbon dioxide from given data?

texts:
I am working on this question, and I am unsure of how to proceed. The question is:

  There is $31.7~\mathrm{g}$ of $\ce{CO2 (g)}$ in a container. The partial pressure of $\ce{CO2}$ is $2.62~\mathrm{atm}$ and the volume of the container is $26.8~\mathrm{L}$. What is the average quadratic velocity ($\mathrm{m/s}$) of the $\ce{CO2}$ in the container?

I think that the formula I should use is this one: $V = \sqrt{3RT/M}$, but I am unsure on how to find the temperature.


texts:
These two molecules are both aromatic:

However, the first molecule has a halogen substituent and is named "bromobenzene". The second molecule has a chlorine and a hydroxyl group and is named "4-chlorophenol". Assuming there was no alcohol group, how would we know when to use benzene or phenyl?

I thought the following:

therefore, shouldnt the first molecule have been written as "bromophenyl" and not as "bromobenzene"?


texts: Does coffee have the ability to dissolve less sugar into it than water?

texts: Like water can absorb such and such an amount of sugar, can coffee absorb less as it already has coffee in it.


texts:
For the reaction

KCl + MnO2 + H2SO4 -> K2SO4 + MnSO4 + Cl2 + H2O

I have Mn going under oxidation from +4 to +2
I have Cl going under reduction from -1 to 0

Then after using my teachers method o multiplying the oxidation and reduction atoms I have

4KCl + 1MnO2 + H2SO4 -> K2SO4 + 1MnSO4 + 2Cl2 + H2O

However I'm not sure I'm on the right track, but if I am, what are the next steps to completely balance the equation?


texts: Wurtz Reaction with acidic alkyl halides

texts: My chemistry book says we cannot use alkyl halides containing acidic hydrogen for Wurtz reaction. Why is this so?


texts: What are the degrees of freedom (from Gibbs phase rule) for an azeotropic mixture?

texts:
For an azeotropic binary mixture, the number of phases is 2 and number of components are 2. So, according to Gibbs phase rule, the number of degrees of freedom should be 2. But, the right answer is 1.
Can someone explain this?


texts:
Say I would like to calculate the heat produced by the following reaction:

$$\ce{2SO2 + O2\longrightarrow2SO3}$$

I have calculated the moles of the reagents. I can't seem to figure out how to calculate the heat of the reaction.

How can I calculate the heat of a reaction with moles of reagents?


texts: Why does dry ice "dissolve" so quickly in water?

texts:
I just stumbled across an ancient video of some people putting a 60 pound block of dry ice in a swimming pool. Pretty cool stuff.

It's pretty interesting to me that in the video, the dry ice sublimates much quicker in the water than in the air.

I am wondering why this might be? Is it possible that water is acting as some sort of catalyst? If so, how can I picture this on a microscopic level? (That might not be possible to answer but the catalyst portion is.)

I was thinking that the $\ce{CO2}$ might be motivated to form carbonic acid, and by Le Chatelier's principle, the dry ice would sublimate even faster.

I'm not so sure that makes sense though...

I don't know. Any thoughts?


texts: Winkler's method in the absence of iodide

texts:
I'm currently doing an IB chemistry individual investigation on the effect of adding bleach to water on the water's dissolved oxygen content. I've used Winkler's method for this and I'm just wondering whether it is possible to do Winkler's method without the presence of iodide ions $(\ce{I-})$, i.e. without adding chemicals like potassium iodide?

I used $\ce{NaOH},$ $\ce{MnSO4},$ $\ce{H2SO4}$ in this experiment (and $\ce{Na2S2O3}$ as the titrant) and I'm not too sure whether I used potassium iodide. However, I've obtained a result and found out a relationship where the dissolved oxygen content increases as I add more bleach into the water.

So my question is: is it possible to do a Winkler's method experiment without the presence of iodide ions? If so, could I know how my experiment worked?


texts: The importance of the cold chain in the food and the pharmaceutical industry

texts:
There are these everyday things that one should know as a scientist and especially as a chemist, but which never come to light in an academic curriculum — at least not in mine.
One such thing is the purpose of imperative non-disruption of the cold chain. It is clear that there are plenty of reasons why it is crucial to transport food and also pharmaceuticals in a refrigerated condition. On the one hand, it reduces the risk of bacteria proliferating significantly, but it also prevents labile substances from decomposing or reacting with other ingredients. So far, so good. But why shouldn't you cool down products again once the cold chain has been interrupted?
I have read, for example, in the package insert of a pharmaceutical product that the drug should always be stored below 25 °C. In pharmacies, the product is kept in the refrigerator, and I, as the consumer, should continue storage in the refrigerator if possible. If this is not feasible for me, e.g., due to lack of space, the storage temperature should not exceed 25 °C. It is also pointed out that I should not keep the drug in the refrigerator after storage at room temperature. This reminded me of the wise words of my grandmother, who said that fish, for example, should only be frozen once because otherwise, it will go bad. With many other foods, similar claims are made. Since these indications can be found across countries and cultures, I assume that there are known scientific reasons for this, but I am not aware of them. I can't figure out why it should be bad to refreeze a defrosted piece of meat or why I shouldn't put my medicine in the refrigerator on hot days anymore after storing it at room temperature for a while.
Maybe a few food chemists and/or pharmacists can shed some light on this.

Edit: Poutnik and Julian, I wish I could accept both of your answers. I find it difficult to decide which answer is "the best", as they both address a different aspect of my question which they explain in a very understandable way. I have decided to mark Julian's answer as accepted since he — despite his long membership — has a much lower reputation than Poutnik.


texts: Electronegativity (Oxygen and Phosphorus)

texts:
What makes an element electronegative. I understand, for example, $\ce{P(OR)3}$ is less basic than $\ce{PR3}$ because the oxygen in $\ce{P(OR)3}$ is more electronegative than P, so it pulls electron density away from the phosphorus, making the lone pair less available, and so, in turn making the phosphite less basic than the corresponding phosphine.

But, what about the oxygen makes it more electronegative than the phosphorus? Is it because of effects of shielding and penetration(?)* that makes oxygen better at pulling electron density. (because it has a higher Zeff)

*I don't think I fully understand what penetration is,so if does have something to do with penetration, could you explain from which orbital will the electrons penetrate to and from, directly referring to oxygen and phosphorus.


texts: How to calculate the molar mass of a protein from its osmotic pressure?

texts:
I am unsure how to go about solving this question. I know how to get the osmotic pressure, but where do I go from there?
I can't use the gas law since the protein is not a gas.

$\pu{2.38 g}$ of a protein is dissolved in $\pu{100 mL}$ of water at $\pu{25^\circ C}$. The solution rises to a height of $\pu{8.5 cm}$ in an osmometer (a device for measuring osmotic pressure). What is the molar mass, in grams per mole, of the protein?
Data: assuming the water ls pure, then the osmotic pressure $\pi = \rho gh$, where $h$ is the height of the water, $\rho$ is the density of water ($\pu{1 g/cm^3}$),and $g$ is the acceleration due to gravity ($\pu{9.81 m/s^2})$.

UPDATE: I've spoken with a masters student (my TA) about this and it turns out that the way to solve this is to use an osmotic pressure equation which is identical to the ideal gas law, but only because it is an approximation. If this question is unlocked I would be happy to share my answer.


texts: Can a stereospecific / stereoselective reaction produce a racemic mixture of enantiomers?

texts:
I think I have my terms mixed up but I'm confused about the concept of stereoselectivity / stereospecificity as they relate to reactions with alkenes.

For example, hydroboration is a stereospecific reaction. It leads to syn addition across an alkene. However, you can form a racemic mixture from it because you can add from either the top or bottom faces.

I think this is a good depiction of what I mean. It seems to me that hydroboration is called stereospecific because it does syn (rather than anti and syn). But it still forms two different stereoisomers, so how can we still call it stereospecific?


texts: How do Cryocoolers that use Helium as Coolant work?

texts: I was unable to find elaborate information on helium based Cryocoolers. I like to know how they use helium to cool samples to cryogenic temperatures and why helium is the best option as a coolant.


texts:
I am a high school student reading about the second law of thermodynamics, and one of the equations given was the free energy change in dilution.
$$\Delta G_{\text{dil}} = -RT \log(C_1/C_2)$$
This implies that as you make a solution more dilute, the free energy decreases. However this equation does not take into account the entropy change in breaking a solid crystal, which I would expect to be highly positive as the crystal is a highly symmetric arrangement. Also it assumes ideal solution.
If we take into account the entropy change in breaking up the solid crystal, we see that the free energy increases while diluting, and also increases in breaking up the solid , that is, concentrating. So I would expect a minima in the free energy vs concentration curve. My guess is it might be the saturation point?
Is my reasoning correct? If it is, then is it possible to calculate the minima?


texts: Will this series of reactions work to produce potassium phosphate?

texts:
I want to end up with a solution or anhydrous sample of potassium phosphate with which I can grow larger crystals. I want a challenge and something to do so I don't want to buy potassium phosphate, I would rather make it myself.

I don't have access to a lot of chemicals but I do have a fair amount of monoammonium phosphate, (or ammonium dihydrogen phosphate), from a crystal growing kit. I plan to heat this until the ammonia is released to leave behind phosphoric acid to which I can then add water to have an acidic solution. I will then dissolve potassium carbonate from corroded alkali batteries into water and add this to the phosphoric acid. The products will then be carbon dioxide, water and potassium phosphate.

My question is will these reactions work and how easy/difficult will it be. I am sorry if this makes no sense at all because I have done my research for this on Wikipedia and it isn't exactly a 100% reliable source. Thanks.


texts: Compare the boiling points of isobutane and 1-butyne

texts:
Question: Compare between the boiling points of isobutane and 1-butyne

The answer to this question is given as 1-butyne has higher boiling point than isobutane.

My approach: I have been taught a few concepts (which I learnt for granted), in my organic chemistry class:

The carbon with a longer chain has a higher boiling point than its isomer with more branching or a shorter hydrocarbon chain. (Kindly correct me if I am wrong here and provide an explanation)

From here I decided that butyne will have a greater boiling point (though I made an incorrect assumption), and luckily my answer came out to be correct, but I am not convinced about the reason for it. Please help with the correct explanation for this question.
I have a proposition that since the electronegativity of $\mathrm{sp}$ hybridisation carbon is very high (only a little bit less than nitrogen), will it show hydrogen bonding? This justifies the given answer.
If it does not show hydrogen bonding, why so? All conditions are fulfilled, a highly electron deficient hydrogen is present and electrons are present in the $\pi$ bond between the carbons. Please help.


texts: Why do iron objects leave black marks on laminate countertop

texts:
My over 30 years old laminate kitchen countertop had accumulated a lot of marks over the years that no cleaner would remove.  I finally gave up and decided to use chlorine bleach on it knowing that the bleach may damage it.  The bleach removed all the marks — looked like new.
There is only one unfortunate side effect: iron objects, e.g. cast iron, that come into contact with the countertop leave permanent black marks even a year after bleaching.  I suspect that the bleach damaged the seal on the countertop since I doubt any chemical residue from the bleaching would remain after a year.  On the other hand how could an over 30 year laminate countertop still have any kind of seal?
Any idea how I can prevent the black marks from iron objects?
Cheers and thanks.


texts:
If substance A boils at a lower Temperature than substance B under atm. pressure, can it be that under some other condition, say, elevated Pressure or under vacuum a reversal of the trend occurs?

i.e. substance B boiling lower than substance A?

Is this phenomenon known? What are some examples?

In other words, If the vap. pr. of A is higher than B at one given T there's no fundamental reason for that inequality to persist at all temperatures, correct?


texts: Are anions stronger bases than (different) neutral molecules?

texts:
I need to compare the basicity of 2 molecules: a negatively charged $\ce{O}$ attached to a t-butyl (t-butoxide), and a neutral $\ce{N}$ with 3 ethyls attached to it (triethylamine).

These are completely different molecules, so by instinct, I would say that the one with the negative charge is probably more basic. But, is there a more formal way of figuring it out (not experimentally)?


texts:
(+)-Clopidogrel (sold as Plavix) is a common pharmaceutical used to help combat the risk of heart disease. The World Health Organisation lists Plavix on its list of 'essential medicines' due to its broad efficacy, low toxicity and low cost (less than 1USD/month in the developing world).

Many industrial routes rely on racemic synthesis and resolution, however syntheses of a single isomer have been reported.

The molecule makes an interesting target as it requires the synthesis of an unusual heterocyclic core, as well as the challenging stereocentre which is prone to racemisation.

Some ground rules:

the synthesis must include formation of the heterocyle (the whole thing, both rings), and a way for setting the stereocentre
you can start from anything you like (subject to the above condition), but it must be available in the Sigma Aldrich catalogue


texts: Why is the bond length of CO+ less than that of CO?

texts:
According to molecular orbital theory, the bond order of $\ce{CO}$ is 3. When $\ce{CO+}$ is formed, the bond order decreases to 2.5, and thus the bond length should increase.

However, the bond length of $\ce{CO+}$ is found to be less than $\ce{CO}$. How is that so?


texts:
The atomic weight of an element, is it accurate to say that another way to think of it is the expected value of that element's weight if we were to sample one at random from the environment?

Are man-made versions counted as part of the weight? I'm new to chemistry but for example let's say we had a typical carbon-12 and we just started removing/adding neutrons at will, resulting in a whole bunch of various isotopes of carbon. I don't know if it's even possible to do that but say we had carbon-6, carbon-7, carbon-8, ... etc etc etc and so on until whatever isotope of carbon can't hold any more neutrons. Would those be counted?


texts: Obtaining energy and wave function for excited states

texts:
Suppose I have done a HF calculation and obtain the energy and wave function of ground state. If I want to produce the spectrum of the specie (say Hydrogen molecule), should I use CI (configuration interaction) method? In general how can I obtain energy and wave function of excited states?
Sorry if my question is awkward, because I'm new


texts: Why does ionization increase from Li to Be?

texts: If ionization energy decreases from $\ce{N}$ to $\ce{O}$ due to the pairing of electrons (causing electric repulsion and greater potential energy) in the $\mathrm{2p}$ orbital in the $\ce{O}$ atom, then why doesn’t ionization energy decrease from $\ce{Li}$ to $\ce{Be}$ as electrons are paired in the $\mathrm{2s}$ orbital?


texts: Which MO approximation best fits with lab results and observation?

texts: I understand that there are many different methods that can be used to approximate the set of MOs for an arbitrary molecule, as the actual quantum mechanical description is taxing to calculate. I just wanted to know which computational method comes closest to reality. B3LYP/6-31G(d) seems to be a popular choice, but I realize that there many others such as RHF/STO-3G, MP2/MINI, etc.


texts: Chemical equilibrium for simultaneous dissociation reactions

texts:
While calculating the adiabatic flame temperature for the following combustion reaction:

$$\ce{\Phi\, C2H6 + $3.5$\,(O2 + $3.76$\,N2) -> $a$\,CO2 + $b$\,CO + $d$\,H2O + $e$\,H2 + $f$\,O2 + $g$\,N2}$$

Where $\Phi$ is the equivalence ratio.

To determine the product composition ratios $a$, $b$, $d$, $e$, $f$ I need to make mass balance on $\ce{C}$, $\ce{O}$ and $\ce{H}$ and then use two $K_{p}$ (Chemical equilibrium constant) relations. Then solve this system of equation simultaneously.

My question is about the elementary reactions of dissociation I should use to apply $K_{p}$ equations, As I could have the following scenarios happening (regarding dissociation):
\begin{align}
\ce{CO + H2O &<=> CO2 + H2}\\
\ce{CO2      &<=> CO + $0.5$\,O2}\\
\ce{H2O      &<=> H2 + $0.5$\,O2}\\
\end{align}

I only need two equations for $K_{p}$ which two should I use and why?


texts: Polarity of alcohols and their miscibility in water

texts:
I am an AP Chemistry student and there is a small detail concerning polarity of molecules that I am confused about.

My review book (Princeton review) says that ethanol has stronger intermolecular forces than methanol because it has a large molecular mass and is therefore more polarizable and more soluble in water than methanol.

Yet, my chemistry textbook says that both ethanol and methanol are miscible in water, but the more the carbon chain increases, the less miscible it becomes. Further supporting this statement is the fact that methanol is less soluble in hexane, a nonpolar substance, than ethanol. Therefore ethanol is less polar. Plus, heptanol is hardly soluble in water, but according to the Princeton Review's logic, it should be even more soluble in water than methanol because it has a larger molecular mass.

So, which is it? Does the addition of CH3s make a molecule more or less polar, and more or less miscible in water?


texts: Why can't a galvanic cell be a single cell?

texts:
I get that galvanic cells require a salt bridge to maintain neutrality so the cathode doesn't become saturated with electrons, but why is a two-cell setup required? Wouldn't the spontaneous reaction occur and neutral conditions be met if Cu and Zn electrodes were placed in a solution of NaCl?

And vice versa, couldn't an electrolytic cell work just fine with a salt bridge?

This website (and many others) leads me to believe that galvanic cells must have a salt bridge and electrolytic cells must be a single cell. My intuition says that's not right though. Is it because you don't want undesirable compounds reacting at the electrodes? I'd think you'd want the same for both EC cell types if that was the case and electrolytic cells would use salt bridges as well (eg proton exchange membranes).
http://chem.libretexts.org/Core/Analytical_Chemistry/Electrochemistry/Electrolytic_Cells


texts: Why is O2 (Oxygen) colorless and odorless while O3 (Ozone) is a pale blue gas with a distinctively pungent smell?

texts: Why does adding one more oxygen molecule to the bond make it smelly and have color?!


texts: On what principle do electric alcohol detectors work?

texts: I know that normal alcohol detectors work on the principle that potassium dichromate oxidizes alcohol . On what principle does an electric alcohol detector work?


texts: Molar extinction coefficient a measure of the probability of a photon of the associated wavelength being absorbed?

texts: Obviously the molar extinction coefficient is not equal to the probability of a photon of the associated wavelength being absorbed, but is it a measure of the probability i.e. the higher the value of the molar extinction coefficient, the higher the probability of absorption of the photon per molecule?


texts: Effect of Synergic Bonding on Bond Lengths in Metal Carbonyls

texts: Consider the metal carbonyl, pentacarbonyl iron(0). There exists synergic bonding between the central metal atom, iron and the neutral carbonyl ligands. This strengthens the metal-ligand bond but because electron density from the filled orbitals of the Iron atom is pushed into the anti bonding orbital of the $\ce{C-O}$ bond, it is weakened thereby increasing bond length. My question was to what extent does the $\ce{C-O}$ bond length increase. Also, is this increase uniform? The reason for my doubt was, the compound has a trigonal bipyramidal type geometry. So the axial metal-ligand bonds are weaker than the equatorial ones. I felt that synergic bonding would not take place to the same extents in the axial and equatorial case - the synergic bonding would be stronger in the equatorial case and weaker in the axial case. Is that so?


texts: How to selectively convert benzene to p-nitrotoluene?

texts:
I converted benzene into toluene by Friedel-Crafts alkylation reaction.
Then by nitration I got two compounds o-nitrotoluene and p-nitrotoluene.

Is it possible to get only p-nitrotoluene?


texts: Increasing C-alkoxycarbonylation of enolates

texts:
I am working with N-tosyl-2-piperidone and attempts to use the lithium enolate of this compound to perform an nucleophilic acyl substitution reaction on an several chloroformate esters in THF has lead to multiple products. The major side product of this appears to be the vinyl carbonate, formed by O-attack of the enolate on the chloroformate ester.

I have used the cyanoformate analogues with success, but benzyl cyanoformate is impressively expensive and if I can avoid synthesizing it (with sodium or potassium cyanide), I would prefer to do so.

Does anyone know of a procedure for increasing the C-addition product of a reaction like this?


texts: Dispersion of Lithium Ions in Nature (Ratio Similar to Isotopes?)

texts: I'm working on a project that identifies average characteristics of different elements. I'm stuck on lithium, I can't find a way to ratio lithium I and lithium II that symbolizes how it is in nature. I tried looking around on the internet but I haven't found any mention of ratios to ions only ratios to isotopes. Does anyone know of anything that might help?


texts:
I recently took a test and one of the questions was:

  Which procedures will allow a student to differentiate between solid sodium sulfate and solid sodium sulfite?

  I. Make solutions of each and look for a precipitate when added to $0.10$ M barium nitrate.

  II. Add crystal of each to $0.10$ M HCl and watch for bubbles.

  III. Make solutions of each and test with a pH indicator.

The answer is 2 and 3, however, I incorrectly answered 2 only. I have actually thought a long time about this question.

Why is III also correct, if sodium sulfate and sodium sulfite are both basic and would turn pH indicator the same color?


texts: Washing up liquid is wet and it is added to water. Why does it not come in a half size package and you add the water yourself? In the same way washing powder is?


texts: It asks about the basicity. All have the same hybridization so through inductive effect, 3 should be the most acidic. I feel that my assumption is wrong. Can anyone help? The answer is 3>4>1>2.


texts: What is the relation between absolute temperature, and rates of diffusion and effusion of a gas?

texts:
According to Graham's diffusion law, rate of diffusion is directly proportional to square root of temperature but rate of effusion is inversely proportional to square root of temperature.

Why is this so? I would assume that rate of effusion would also increase with increase in temperature due to increased speed of the gas.


texts: Li2O + 2KCl =2 LiCl +K2O: Is it a feasible Reaction?

texts:
$$\ce{Li2O + 2KCl <=> 2LiCl + K2O}$$

I got this reaction on a test question paper. With three other options, it was asked whether this reaction is feasible or not?

I googled it and found the reverse reaction of at every webpage I looked. So, it seems to me it isn't feasible.

I think that the reverse reaction is feasible because $\ce{LiCl}$ is quite covalent in nature(Fajan's rule) So, for becoming more ionic in nature $\ce{Li+}$ makes bond with oxygen ion. (I now think it's a bogus reasoning)

What could be the reason behind it? Is it feasible?


texts: Lead's affinity for oxygen in the cupellation refining process

texts:
My inorganic chemistry textbook1 says:

Cupellation is a process, where crude gold is taken in a small bowl called cupell and melted in the presence of air. Due to high oxygen affinity of $\ce{Pb}$, it is converted to $\ce{PbO}$ (volatile) and escapes from the system.

Now, the affinity for sulphur and lead is explained by HSAB (soft acid-soft base). But how to account for the affinity of oxygen (hard base) and lead (soft acid)?
References

Guha, Sudarsan. Concise Inorganic Chemistry for JEE (Main and Advanced). 4th ed., Wiley India Pvt. Ltd., 2017.


texts:
A question regarding the Michaelis-Menten curve. For those of you who are well-versed in chemical kinetics(or even better, enzyme-kinetics) you most likely have come across this curve before. It is a hyperbolic curve, eventually reaching a plateau, where the Initial velocity(reaction rate) of the reaction is given as a function of the substrate concentration. Befofe I go on to say what has been bothering me I just want to remind that once the curve has reached a plateau this is known as the maximal initial velocity and it is caused by enzyme saturation by the substrate.

Now what has been truly bewildering me is the fact that when these experiments are done the enzyme concentration, which is always kept constant, is always much much lower than the substrate concentration(even when the substrate is at it's lowest concentrations). I'm talking about Enzymes having nanomolar concentrations while the substrate is five or six orders of magnitude higher. Surely the amount of substrate is already more than enough to saturate the enzyme from the get-go with the smallest concentrations. How is this not so?? When I saw the ratio of enzyme molecules to substrates I figured it is way more than enough to saturate the enzymes thus as a result the Michaelis-Menten curve wouldn't make sense and that the curve should start of as a plateau at the maximal initial velocity and just stay that way forever. I hope this wasn't too confusing.

Thanks for any attempts at an explanation


texts:
I am trying to make sodium acrylate by neutralizing acrylic acid with sodium hydroxide. I further want to photo-pattern it, which requires the addition of photoinitiator to sodium acrylate.

The problem is acrylic acid and photoinitiator are soluble in ethanol, but NaOH is not. Hence I'm looking for a common solvent for sodium acrylate and the photoinitiator.