texts: Why Aren't Chlorides Of The Noble Gases As Prevalent As Their Fluorides?

texts:
I can't find the answer to this question on this SE website, and I apologize for the repetition if it has been answered before. It is my understanding that compound formation has only been observed for the noble gases argon, xenon, and krypton, while no compounds have ever been observed for neon and helium, and that this might have something to do with both the decreased ionization potential of larger noble gas atoms and the high value of electronegativity of the halogen (usually fluorine) that bonds with the noble gas atoms to form compounds. So, my question is why aren't compounds formed from argon, xenon, and krypton bonding with chlorine, bromine, and iodine as prevalent as those formed from those noble gases and fluorine? Could the smaller size of the fluorine atom be a reason for its apparently higher reactivity?
-John


texts: What causes the DNA fragments to stop moving in gel electrophoresis?

texts:
I'm currently studying VCE BioChemistry, and we're studying the separation of DNA strings of different lengths via gel electrophoresis.

(This involves having 'clumps' of DNA at one end of a gel medium and applying an electric current, pushing the DNA strands across the gel. Different sized strands move at different speeds through the gel)

At some point, the strands stop moving such that there is a distribution of strands across the gel. What causes the strands to stop?
Surely they'd continue until the end of the gel.

If suppose the electric current could be stopped, thus causing the strands to stop moving, but how would one know when to stop the current?


texts: What are the fumes that form above liquid nitrogen?

texts: What is the composition of liquid nitrogen fumes? Is direct contact with these fumes harmful?


texts: Still struggling with Huckel rule and aromaticity

texts:
I'm still learning huckel rule and aromaticity in different compound.
For the 1-methoxy-1,3,5,7-octatetraene, is it correct that it has 8 electrons inside the cycle, but since they will be 8, then it is antiaromatic?
And for the Imidazole, is it 6 electron inside because the N: doesn't contribute to the pi, or is it 8?


texts: Are nucleophilic aromatic substitutions stepwise or concerted?

texts:
Recently, there has been a lot of discussion about nucleophilic aromatic substitution (SNAr) reactions apparently being concerted instead of stepwise (e.g. Krämer, K. Textbook aromatic substitution mechanism overthrown. Chemistry World, 23 July 2018):

This is in contrast to the usual mechanism taught at an undergraduate level, where the anionic Meisenheimer complex is considered to be an intermediate:

What is the current consensus on the mechanism, and what evidence is there for it?


texts: What is the name for the relationship between two elements in the same group?

texts:
I'm looking for a specific term which can be used to describe two elements in the same group of the Periodic Table. This would be useful since elements in the same group tend to have similar chemical/physical properties.
For example, is there a word that could fill in the blank: "X is a _______ of Y", where X and Y are in the same group? It has to be something that is generalisable to all groups, not just one particular group, so terms like "alkali metals" or "halogens" are too specific.


texts: Do 1 mole of both dioxygen gas and its atoms occupy 22.4 litres at STP?

texts:
The ideal gas law states:

  One mole of an ideal gas will occupy a volume of $\pu{22.4 liters}$ at STP.

Does this mean that both

$\pu{1 mole}$ of $\ce{O}$  would occupy $\pu{22.4 L}$ (or if this doesn't usually occur in nature, say \pu{1 mole }of $\ce{He}$ or any another monoatomic gas)
$\pu{1 mole}$ of $\ce{O2}$ would occupy $\pu{22.4 L}$

I am assuming the answer is yes based on:

reading the ideal gas law definition, it wouldn't make sense if it was true only for $\ce{He}$ but not for $\ce{O}$.
in class when we are finding the volume of e.g. $\pu{100 grams}$ of $\ce{Cl2}$, it was always $\frac{\pu{100 grams}}{(2\times\pu{35 grams} \text{[molar mass of $\ce{Cl2}$]}} \times\pu{22.4L}$  and not $\pu{1\times35 grams}$

But why? Wouldn't $\ce{O2}$ contain twice the amount of $\ce{O}$ matter and hence take up twice the volume?


texts: Dilute FeCl3 colour is darker at 5e-4M than at 5e-3M. Why?

texts:
I did two different dilutions of $\ce{FeCl3}$ (within a $\pu{1h}$ timespan) from $\pu{0.05 M}$, and the one with $\pu{5E-4 M}$ concentration looked a darker orange than the one with $\pu{5E-3 M}$.

The picture shows on the left: $\pu{5E-3 M}$ (I erased the label on the flask); on the right: $\pu{5E-4 M}$

I did a test with litmus paper, which showed that the more concentrated one ($\pu{E-3}$) was more acidic, which makes sense. I also did a rates test ($\ce{FeCl3 + H2O2}$), and the more concentrated one made the reaction happen faster, which again makes sense. Why, then, does the more concentrated $\ce{FeCl3}$ look lighter coloured?

Since I had made the more dilute one ($\pu{E-4}$) before, I thought there might have been more time for the ferric hydroxide to precipitate and form a darker colour. But I had only left it for $\pu{1h}$. I also thought that since the more concentrated one looked greenish, $\ce{FeCl2}$ might have been made, yet this does not seem plausible as $\ce{FeCl3}$ is more stable.


texts: What are the methods used to measure the concentrations of these anions?

texts:
Chromate and dichromate anions has the following equilibrium in acidic solution:

$$\ce{2CrO4^2- + 2H3O+ <=> Cr2O7^2- + 3H2O}$$

How can one experimentally measure the concentration of each ion at a certain equilibrium?


texts: How to find the final pressure excerted by a mixture of gasses which are then released from a vessel after succesive fillings?

texts:
The problem is as follows:

  $5\ \mathrm l$ of oxygen at $2\ \mathrm{atm}$ of pressure and $10\ \mathrm l$ of nitrogen at $4\ \mathrm{atm}$ are collected in a vessel of $2\ \mathrm l$ in capacity. Then $25\ \mathrm l$ of the mixture is released from the vessel at the pressure of $760\ \mathrm{mmHg}$. Find the final pressure of the mixture if the temperature doesn't change.

What I've attempted to do to solve this problem was to use this equation from gasses. However, it seems tricky as there's no specific information of the temperature only it mentions that it doesn't change.

$$pV=nRT$$

The way how I thought to approach this problem was that if I could obtain the moles of each gas and add them both I could find the final pressure in the container.

Then as the temperature is held constant I could use this equation using Boyle's law to get the new pressure.

$$\frac{p_{1}V_{1}}{T_{1}}=\frac{p_{2}V_{2}}{T_{2}}$$

(Assuming $T_1=T_2$). However, I'm confused at exactly why was I given the pressure of $760\ \mathrm{mmHg}$. Is it to stress the fact that gas can escape from the vessel if the pressure outside is lower?

Well here's what I did:

For oxygen:

$$(2\ \mathrm{atm})(5\ \mathrm l)=\left(n_{\ce{O2}}\right)(0.082\ \mathrm{atm\ L \ mol^{-1}\ K^{-1}})(T_1)$$

$$n_{\ce{O2}}= \frac{121.9512}{T_1}$$

For nitrogen:

$$(4\ \mathrm{atm})(10\ \mathrm l)=\left(n_{\ce{N2}}\right)(0.082\ \mathrm{atm\ L\  mol^{-1}\ K^{-1}})(T_1)$$

$$n_{\ce{N2}}= \frac{487.8048}{T_1}$$

Then adding those moles together results into:

$$n_\text{total}= \frac{121.9512}{T_1} + \frac{487.8048}{T_1}$$

$$n_\text{total}= \frac{609.7560}{T_1}$$

Using this amount of moles, I am given the volume of the vessel hence I can know the pressure.

$$(p)(2\ \mathrm l)=\frac{609.7560}{T_1} (0.082\ \mathrm{atm\ L\ mol^{-1}\ K^{-1}})(T_1)$$

$$p= 25\ \mathrm{atm}$$

Finally this pressure can be used to get the new one using the equation shown above:

$$\frac{25\ \mathrm{atm} \cdot 2\ \mathrm l}{T_{1}}=\frac{p_2\cdot 25\ \mathrm l}{T_1}$$

Therefore I'm obtaining $2\ \mathrm{atm}$.

But this option doesn't appear in any of the alternatives for this given problem. What could I be overlooking, can someone help me?


texts:
What are the products formed when vinyl chloride reacts with dimethyl copper?

I thought the product formed would be propene. But answer given is PolyVinylChloride. How does polymerization take place?


texts: Do melt flow rate and density tell you everything about pure HDPE?

texts: I understand that melt flow rate and density can be used to classify HDPE. Does this mean that if I have the melt flow rate and density of an HDPE (with no additives), then I can know its other material properties?


texts:
I found that from many definitions reducing sugars are those which contain free aldehyde or ketone group which can reduce reagent like Tollen's Reagent.But I have also read that ketones get oxidized only with very strong oxidizing agents like alkaline KMnO4 or acidified potassium dichromate under vigorous condition.So according to what i read,then i could say that fructose is a non reducing sugar as it won't be able to reduce weak oxidizing agents like Tollen's Reagent.

But its also said in my textbook that all monosaccharides are reducing sugars.But fructose is a monosaccharide.Then how can it be a reducing sugar.Please explain me if there is any misconceptions from my side.


texts: Differences between KOH and phosphorus pentoxide as drying agents?

texts:
The most common drying agent I encountered when using a vacuum dessicator was phosphorus pentoxide in the form of Sicapent. But I've recently encountered people using KOH as a cheaper alternative (in a practical course for students, where such costs are amplified due to the high number of students).

What are the differences between KOH and phosphorus pentoxide as a general purpose drying agents to remove water? Is there a difference in effectiveness? Are there classes of substances where you can't use one of those drying agents?


texts: Radical formation via tritium to helium decay

texts: Following on from this question about tritium water, I was wondering whether the decay of tritium to helium-3 has ever been used in organic synthesis. Such a transition would presumably result in no strong $\ce{C-He}$ interaction and thus radical or cation formation at $\ce{C}$.


texts: Accelerated Oxidation Of Iron When Coating Breaks

texts:
I was presented with the following information:

If iron is painted, then oxygen and water are prevented from contacting the metal, and corrosion is avoided.
Sometimes the iron is coated with a thin layer of another metal, such as Tin (the layer of Tin keeps oxygen and water away from the iron)
If the layer of Tin is worn away or scratched, the presence of Tin will actually accelerate the corrosion of the underlying iron. (http://www.mikeblaber.org/oldwine/chm1046/notes/Electro/Corrode/Corrode.htm)

I understand why Iron would be oxidized when the coating breaks, as an observation of the reduction (oxidation) potential would show that it is more favorable to oxidize iron, over tin.

However, the portion I am confused on is:

Why would corrosion be accelerated?

The passage I was reading suggested that it was because Tin acts as a cathode and thus would accelerate the corrosion, but that does not make a lot of sense to me. As I would see it, there would be little difference whether the Tin is there or not, and thus the reaction (corrosion) should not be accelerated, but simply as quick as it would have been without the coating.

Any insight would be greatly appreciated! Thanks!


texts: What is the mole fraction in mixture before combustion?

texts:
What is the mole fraction of $\ce{C2H6} / \ce{C3H8}$ in mixture, if both compounds reacted with  $\ce{O2}$ in stoichiometric ratio? Mass of produced $\ce{CO2}$ is $1.819$ times larger than the mass of $\ce{H2O}$.

$$\ce{C2H6_{(g)} + O2_{(g)} -> CO2_{(g)} + H2O_{(g)}}$$

$$\ce{C3H8_{(g)} + O2_{(g)} -> CO2_{(g)} + H2O_{(g)}}$$

I balanced the equations and tried the following:

$\frac{X4M(CO_2)+(X-1)4M(CO_2)}{X8M(H_2O)+(X-1)6M(H_2O)}=1.819$

Which led me to the wrong result.

Could anyone kick me in the right direction?


texts: Why is the probability for the signal at 160 in the bromine mass spectrum twice as high as for the signals at 158 and 162?

texts:
The mass spectrum in Bromine, with the molecules $\ce{^{158}Br2+}$, $\ce{^{160}Br2+}$ and $\ce{^{162}Br2+}$:

As you can see, the $\ce{^{160}Br2+}$ is almost double in intensity compared to the $\ce{^{158}Br2+}$ and the $\ce{^{162}Br2+}$ peak.

The book I am reading simply states that this is because

  The probability of two different isotopes occurring in a $\ce{Br2}$ molecule are twice that of the same isotope appearing in a $\ce{Br2}$ molecule.

This is supported by the $\ce{^{160}Br2+}$ peak, formed from the $\ce{^{79}Br}$ and $\ce{^{81}Br}$ isotopes.
Likewise, $\ce{^{158}Br2+}$ peak is formed from two $\ce{^{79}Br}$ isotopes and $\ce{^{162}Br2+}$ is formed from two $\ce{^{81}Br}$ isotopes.

However, I am confused by the explanation given by the book above.
Why is the probability of two different isotopes occurring in a $\ce{Br2}$ molecule twice that of the same isotope appearing in a $\ce{Br2}$ molecule?


texts: Why is it that less useful energy can be extracted in explosive reactions?

texts: If you extract energy from a substrate (e.g. glucose) step-wise, a lot more free energy is released that can be used. However, if you were to do this in one single step, very little useful energy could be harnessed. Why is that?


texts: Difference between adiabatic and nonadiabatic tunneling for molecule

texts:
What is the difference between adiabatic and nonadiabatic tunneling for a molecule in a laser-field?
Does nonadiabatic tunneling necessarily relate to the Conical intersection or curve-crossing?


texts: Is H2CO3 (carbonic acid) soluble or insoluble in water?

texts: I am asking this because I know that acids are normally aqueous but according to the solubility rules, all carbonates are insoluble.


texts: How much heat is needed to break CO2 down to CO?

texts: I have found that because the oxygen is double bonded to carbon, it takes about $\mathrm{1500\ ^\circ C}$ to break it down from $\ce{CO2}$ to $\ce{C}$ and $\ce{O}$. But, I am curious, would it take less heat energy to break $\ce{CO2}$ down to $\ce{CO}$ and $\ce{O}$?


texts: Interaction between metalic nanoparticles and aggregation

texts: I can't find any publication to deal with aggregation of colloidal metalic nanoparticles. What type of interaction(s) is/are there between aqeous metalic nanoparticles which give(s) rise to aggregation?


texts: Order of Acidic strength: Phosphorus oxoacids

texts:
I was asked to compare the acidic strength of the following phosphorus oxoacids,

I thought the order (of strength) would be $\ce{H3PO4 > H3PO3 > H3PO2}$, because they have three, two and one ionizable $\ce{O-H}$ bonds (that furnish protons / $\ce{H^+}$ ions).

However, looking up the $\pu{pK_a}$ values on the respective Wikipedia pages of each of those acids, suggests the exact opposite order of acidic strength:
$\ce{H3PO2 > H3PO3 > H3PO4}$. Apparently the acid with one $\ce{O-H}$ bond is a far stronger than the acid with three $\ce{O-H}$ bonds!

This is horribly counter-intuitive :-(

So, why is the correct order of acidic strength  $\ce{H3PO2 > H3PO3 > H3PO4}$, and not the other way around as I believed? What was wrong with my analysisi ( acidity in oxoacids $\propto$ number of $\ce{O-H}$ bonds)?


texts: How does the composition of a mixed solvent affect solubility?

texts:
I am trying to find out how varying the proportion of each solvent in a binary (water/ethanol) solvent solution affects the solubility of an organic acid. I know the solubilities of the acid in each solution. Is it as simple as a linear relationship between solvent composition, or is there something else going on?

This question deals with the same topic, and the conclusion there is that it is immensely difficult to predict solubility in mixed-solvent systems. My question is different for two reasons - I only want a qualitative answer, and I know the solubilities for the compound in both pure solvents.


texts:
Which statement is correct about electron orbitals and energy levels?
A. Yttrium, $\ce{Y}$ ($Z = 39$) is the first element in the periodic table with an electron in a f sub-level.
B. The maximum number of electrons in one d orbital is 10.
C. The maximum number of electrons in the 4th main energy level is 18.
D. In a main energy level, the sub-level with the highest energy is labelled f.

I thought B and D are all possible solutions to this answer.
B--the maximum number of electrons in 1 d orbital is 10.
D--in main energy level, the sub-levels in order of increasing energy is s $<$ p $<$d $<$f
So why is the answer only D?
Please advise and sorry in advance for the wrong tags or title name, as I am new to the group and am trying to improve on it.


texts: How is it determined how many electrons are transferred in redox reactions?

texts:
For example, iron and tin(II) sulfate will react to produce iron(II) sulfate and tin:

$\ce{Fe + SnSO4 -> FeSO4 + Sn}$

With the following half equations:

$\ce{Fe + SO4^{2-} -> FeSO4 + 2e-}$

and

$\ce{Sn^{2+} + 2e- -> Sn}$

but where does the "2" come from? Why can't it be:

$\ce{Fe + SO4^{5-} -> FeSO4 + 5e-}$

and

$\ce{Sn^{5+} + 5e- -> Sn}$


texts: When DNA degrades, does any chemical environment preserve sequence information?

texts:
Small bits of DNA information can be found in ancient remains.   In analogy to
old bones becoming mineralized, is there a chemical environment in which the
nucleic acid sequence of the original strand might remain readable though in other, more
stable, chemical form?


texts: Na+ or Ca2+ . Which ion has the larger radius?

texts: Which ion has the larger radius? Some sites say $r(\ce{Na+}) > r(\ce{Ca^2+})$. Any explanation would be appreciated.


texts: Is axis of symmetry considered a true symmetry?

texts:
In most of the books when i read about optical activity of a compound this is what they say:

A compound that does not posses any kind of symmetry is optically active. In other words chiral compounds without having any kind of of symmetry are optically active.

However, this holds true when we refer to plane of symmetry or centre of symmetry, because molecules having axis of symmetry or alternate axis of symmetry are still optically active.

For example this compound possesses axis of symmetry but is still optically active:

And therefore i am totally confused about relation of optical activity with symmetry.

Thanks for answering the question


texts:
I know that in side chain oxidation with the given reagent follows oxidation of benzylic carbon (if atleast one benzylic hydrogen is present). So my answer would be

But in my answer key only it is correct for nitro substituted anthracene. But why? What is the reason?
Thanks for clearing my doubt!


texts: How do we predict the properties of the materials we make through chemical reactions?

texts: I find chemistry fascinating. I've taken a couple of classes and so am familiar with the rudiments of orbital theory, equilibria, acid/base chemistry, and a small bit of organic chemistry. So I can attempt to make predictions about which reactions might happen, but I'd like to know what the properties of the materials made are ahead of time. Is there a way to do this? I know that there are materials composed of the same elements in different structures that have vastly different properties (melting point, color, conductivity, etc.), so what can we actually do to predict these things (i.e. figure out the structure we'll get, and the properties these structures produce)?


texts: Why does pOH increase when pH decreases?

texts:
Let's say you add $\ce{HCl}$ to water. The $\ce{H+}$ ion concentration increases and that causes a decrease in $\mathrm{pH}$. But why would the $\mathrm{pOH}$ increase?

I can't see why added $\ce{H+}$ ions will decrease the $\ce{OH-}$ concentration? Is this because of the water auto-ionization? Is it because, according to Le Chatelier principle, when you add an amount of a component, the reaction will go in the other direction to counteract the disturbance, thus decreasing the concentration of $\ce{OH-}$ to form water?


texts:
Determine the normality of sulfuric acid solution, given that it gives a yellow color with methyl orange and a red color with methyl red.
can someone help me with this? what should do first?
i know that normality = (grams of solute)(factor) / (MW of solute)(liters of solution)


texts: Why does carbocation stability increase in the order 1°, 2°, 3°?

texts:
I'm reading about $\:\mathrm{S_N1}$ and $\:\mathrm{S_N2}$ reaction mechanisms. 1° carbocations are unstable to the point of not having been observed in solution, ever. 2° are more stable, and 3° carbocations are the most stable.

I know that higher stability carbocations do also require less activation energy in their formation. Why is that? Why exactly are they more stable? And is this another way of saying they are also less reactive? Does this in turn mean they require a better nucleophile compared to less stable carbocations?

A small side question. How should I think about resonance structures? You don't view it as changing between the forms, spending more time being the more stable form, but rather as a seamless blend of the forms, with more characteristics of the more stable form, right?


texts: How to prepare glacial acetic acid from sodium acetate?

texts:
What would be the most practical process to prepare glacial acetic acid from sodium acetate?

I'm thinking to react the sodium acetate with an acid to convert the solution to acetic acid and sodium salt but I'm not sure of the most practical way to proceed from here without distillation (which seems impractical).

I think solvent extraction (using a protonated solvent such as $\ce{CH2Cl2}$) then removal of the solvent would be a way but I'm not sure.

I would like to hear from someone who's done it before.


texts: My text seems to say that the high(est) energy orbitals are not valence orbitals - everything else says otherwise. What's true?

texts:
A paragraph in my text reads

  Bonding involves the valence orbitals almost exclusively because these orbitals have the appropriate energies to interact strongly. Examine the electron energy-level diagram of a fluorine atom. The core $1 \mathrm{s}$ orbitals on a fluorine atom are at much lower energies than any of the $n = 2$ orbitals and do not participate effectively in bonding with other atoms. On the other hand, orbitals with $n > 2$ lie at considerably higher energy than the $n = 2$ orbitals. These orbitals can interact, but the resulting orbitals are too unstable to form strong covalent bonds. Therefore, the only orbitals of fluorine that form chemical bonds are the valence orbitals, those with $n = 2$. Typically the highest energy occupied orbitals are the ones used to bond with other atoms.

In contrast this simple paragraph from SparkNotes expresses what I had believed to be the case

  The outermost orbital shell of an atom is called its valence shell, and the electrons in the valence shell are valence electrons. Valence electrons are the highest energy electrons in an atom and are therefore the most reactive.

I had thought that the outermost shell, the valence shell, the most energetic shell, and the shell involved in molecular bonds were all the same thing. However, the quoted paragraph of my text says otherwise. Where have I gone wrong?


texts: Why do large cations stabilise large anions and small cations stabilise small anions?

texts: I see this trend from enthalpy change of decomposition data, though I struggle to find a decent explanation for why.


texts: Brownian motion modeling of surface reaction

texts:
I am interested in simulating a reaction-diffusion system, where particles subjected to Brownian motion can react when they reach a specific surface. The reaction is simple:
A $\rightleftharpoons$ B
The equilibrium rate constants are the following:
$k_f(E)=k_0exp(-cE)$ [forward reaction, A$\rightarrow$B],
$k_b(E)=k_0exp(+cE)$ [backward reaction, B$\rightarrow$A];
where $k_0$ and $c$ are two constants and $E$ is a generic driving force. Note that $E$ varies with time.
How should I parameterize the reaction probabilities, for the particles which reach the surface?


texts: Nucleophilic Substitution (ion pair mechanism)

texts:
Carey and Sundberg (2007) talked about how in ion-pair mechanisms, azide ions tend to attack ion pairs, not the free ions, why is this the case?
Also, ions tend to be solvated, how does a nucleophile sort of break through the solvent shell to reach the inner electrophile? I'm interested in the mechanism behind this process


texts: Flexibility of long-chain aliphatic compounds

texts:
PubChem is unable to generate the conformers of Z-6-Heneicosen-11-one? The website says that the molecule is too flexible

What does flexibility of a molecule mean in this context? I understand that it is a long chain compound, but I assumed that the bonds are rigid and do not flex? In layman’s terms, how does one quantify flexibility? Is it flexible like a skipping rope or like something else?


texts: Why Platinum, Gold, Carbon are inert? In electrolysis, it's not react in anode because anode is doing oxidizing, but how about cathode? Are they still inert?


texts: How can I figure out whether a reaction is endothermic or exothermic without its enthalpy value?

texts:
I already know the way to determine whether if the given reaction is exothermic or endothermic by the enthalpy values. But is it possible without enthalpy values, and just by looking at the reaction?

So as far as I know there are two types of chemical reactions, namely one way reactions and reversible reactions.

So how can I determine this factor in one way reactions and reversible reactions?

I guess that for reversible reactions we can use equilibrium constants such as $K_p$, $K_c$, but I am not quite sure whether it is correct. On the other hand, I feel that there is no such way to determine what I want in one way reactions. So how can I decide it?


texts: How to treat skin corrosion by sodium hydroxide?

texts: I'm under training of becoming floorman in the rig. We use a lot of chemicals and one of them is caustic soda or sodium hydroxide. In case it touches my skin can you tell me of ways to treat it? I have thought of neutralizing it by slowly going less basic by using for example household ammonia then hand soap then sea water.


texts: Unknown white precipitate in electrolysis of water

texts: I was electrolysing water using a copper anode and zinc cathode.  The water was from the tap and where I live is very hard.  I was using about 20V between the two electrodes.  As I applied the voltage, a white precipitate formed around the anode.  What is strange is that I can't replicate this using any other type of metal as the anode.  Any ideas on what this might be?   Or, I suppose a better question is: are there any ideas on how I can find out what this was?


texts: Superscript open circle notation in formula

texts:
I may be only a physicist but I'm familiar with the superscripted dot to indicate a radical.  In a paper I'm reading the authors have also used a superscripted open circle.  I can't find any reference online or in my physical chemistry textbook (Atkins). Here's an example:

As you can see they've done this a few times, and also used the dot to indicate a radical.  This is in a published paper "Photocatalytic degradation pathway of methylene blue in water", Houas et al., Applied Catalysis B: Environmental (2001).  I'm starting to wonder (given the OH◦ in the text and OH• in the equation) if it's a typo, but I'd be surprised if something so glaring could get through review or even proofreading by coauthors.

So does the open circle have a meaning of its own?


texts:
In the design of a celebratory pyrotechnic (firework), there exists a gunpowder explosive charge at the center of the firework and pyrotechnic "stars" lining the circumference of the explosive. The "stars" are composed of an oxidizer and a fuel such as KNO3 oxidizer and charcoal as a fuel. If the oxidizer is removed from the "stars", is it reasonable, upon detonation, to assume that the now vapourized "star" will combust only with the detonation of the gunpowder explosive charge without the need for an oxidizer in the "star" composition?

See this page for a diagram and composition of materials: http://www.instructables.com/id/How-to-Make-Fireworks/


texts: How do I get Mass spectrometry graph, history, and Infra-red spectroscopy graph for Secnidazole?

texts:
My chemistry teacher wants me to create an academic poster for a recently-discovered biologically important organic molecule with chirality that is relatively small and is also recent.

Secnidazole (also called Solosec) seems to fulfill these requirements fairly well, however I have no clue on how I would be able to obtain the mass spec or infra-red spec of it, as they doesn't seem to be listed online anywhere. As well as this, there doesn't seem to be a listing for what organisation created it or anything either.

How do I either get a rough approximation of the results, or find a legitimate set? Bonus points for directing me to the history of the molecule.


texts: Why is potassium phosphate KH2PO4 in this reaction?

texts:
This is a continuation of this question because the first thing that came in my mind is that why potassium phosphate in this reaction is $\ce{KH2PO4}$ and not $\ce{K3PO4}$?

In the wikipedia article of phosphate ion ($\ce{PO4^3-}$), it is written that:

  Aqueous phosphate exists in four forms. In strongly basic conditions,
  the phosphate ion ($\ce{PO4^3-}$) predominates, whereas in weakly
  basic conditions, the hydrogen phosphate ion ($\ce{HPO4^2-}$) is
  prevalent. In weakly acidic conditions, the dihydrogen phosphate ion
  ($\ce{H2PO4−}$) is most common. In strongly acidic conditions,
  trihydrogen phosphate ($\ce{H3PO4}$) is the main form.

So, $\ce{FeCl2}$ must somehow be acidic in aqueous solution so as to protonate potassium phosphate $\ce{K3PO4}$ to $\ce{KH2PO4}$. Is this statement true? This question throws some light on acidity of chromium chloride in aqueous solution but is it applicable to iron chloride as well?

In the previous question, the homework question was write the equation of reaction of Iron(II) chloride and potassium phosphate. So, students can assume the reaction to be $\ce{FeCl2 + K3PO4}$ to simply yield iron(III) phosphate or iron(II) phosphate and potassium chloride but why make the reaction complex by assuming potassium phosphate $\ce{KH2PO4}$.

Iron hydrogen phosphate are new in this world and has been recently synthesised and as not as stable as iron phosphates. So, can we just assume that reaction of Iron(II) chloride and potassium phosphate to yield iron (II or III) phosphate and potassium chloride?


texts: Is the first ionization energy in oxygen slightly more than nitrogen?

texts:
Why is the first ionization energy in oxygen slightly more than nitrogen?

In nitrogen: $\ce{[He] 2s^2 2p^3}$
In oxygen: $\ce{[He] 2s^2 2p^4}$

This tells me that it should be easier to remove an electron from oxygen than it is for nitrogen as the electron in oxygen is slightly further away from the nucleus meaning lesser nuclear charge.

But why is it harder to remove an electron from oxygen, i.e. why is the first ionization energy of oxygen higher?


texts: Convert CIF file to SDF file using free Linux-compatible software other than Avogadro or OpenBabel?

texts:
I am trying to convert http://crystallography.net/cod/2236556.cif to a file that I can open in Avogadro without some bonds disappearing. See this crystal structure is of tianeptine hydrochloride, yet many of the bonds are not shown when I open the CIF in Avogadro.

This is what the CIF is meant to be rendered like (shown in PyMOL):

while this is what I see in Avogadro (also displayed like this in Avogadro 2):

note how so many bonds are not shown properly. I suspect if I could convert the molecule to SDF or CML or some other 3D chemical format I'd be able to fix this issue and Avogadro will be able to render the file properly.

I have tried doing the file conversion with OpenBabel but the files generated look, when viewed in PyMOL or Jmol (which render the CIF fine), just like the CIF does in Avogadro with all the disconnected atoms.


texts: Mass Transport and Ion Transport - Li-ion Batteries

texts:
I am new to the field and trying to grasp the theories/ physical phenomena behind the Li-ion batteries. I came across two phenomenons 'Mass transport' and 'Ion transport'.

As I understood Mass transport is the Diffusion process (Fick's First law) which describe the transport mechanism how Li-ions are transported from one electrode to the other through the electrolyte.

Now, I wonder what is covered by the Ion transport equations which are based on Fick's Second law and Stokes-Einstein equation.

As I understood, they both describe the same thing [probabl two parts of the same phenomena which is Mass (which is Li-ions) transport through the electrolyte]. But I don't quite get it, Could someone please shed some light on this matter? Any explanation including explanation relating to physical phenomenon is much of my liking.

Many thanks in advance.


texts: Relation between chemical kinetics and chemical equilibrium

texts:
In my chemistry book, the law of chemical equilibrium is derived from the law of mass action:

For a reversible chemical reaction $$\ce{aA +bB\rightleftharpoons cC + dD}$$ where $a$, $b$, $c$ and $d$ are stoichiometric coefficients in the balanced equation, we have, from the law of mass action, the rate of the forward reaction $$r_\mathrm{f} = k_1 \ce{[A]^a[B]^b}\label{1}\tag{1}$$ where $[\ce{A}]$ represents the concentration of $\ce{A}$ and so on. The rate of the backward reaction is $$r_\mathrm{b} = k_2\ce{[C]^c[D]^d} \label{2}\tag{2}$$
At equilibrium, $r_\mathrm{f} = r_\mathrm{b}$, so, we have $$\frac{k_1}{k_2} = \frac{\ce{[C]^c[D]^d}}{\ce{[A]^a[B]^b}}$$ Replacing $\displaystyle \frac{k_1}{k_2}$ by $K_\mathrm{c}$, we have
$$K_\mathrm{c} = \ce{\frac{[C]^c[D]^d}{[A]^a[B]^b}}\tag{3}\label{3}$$
which is the law of chemical equlibrium. $K_\mathrm{c}$ is supposed to be constant, for any concentration of the reactants, at a particular temperature.

However, in chemical kinetics, they tell us that the rate equation, derived from the law of mass action is not always correct. That is, the exponents of the concentration terms in the rate equations may not be equal to their stoichiometric coefficients. If this is true then, the above two rate equations ($\eqref{1}$ and $\eqref{2}$) may not be correct for a particular reversible reaction.
Then, how can we apply the law of chemical equilibrium on every reaction, without experimentally verifying the rate equations? If the rate equations derived from the law of mass action are wrong, then the value of $K_\mathrm{c}$ obtained by the final equation will not be constant.


texts: What is the difference between carbon and charcoal filters?

texts:
I'm confused about the difference between carbon and charcoal filters.
Ultimately, charcoal contains carbon but I have come across an exam question that asks for their individual roles in a water filter.

I have done some research and found this page that states that 'activated carbon' and 'activated charcoal' can be used interchangeably.

Would any of you be so kind as to help me decipher the individual role of carbon filter and a charcoal filter in an ideal water filter?


texts: Can an excessive reactant amount result in a longer reaction time?

texts: I am performing an experiment with DTZA and Ferrate. After a point of increasing the DTZA concentration too much the Ferrate takes longer (lower reaction rate) to react with the DTZA. Is this something reasonable or is it due to error?


texts: Is these a pair of diastereomer or identical compound?

texts: I attempted on this question (e) and found out that they are diastereomers, but the answer from the book is that they are identical. I worked out the configuration at each of the centres for the molecules then compare the results. If you find that one is RS and the other is SS then you'll know that they differ at only one stereo-centre and hence I think the book is wrong. I've got this question from Solomons: Organic Chemistry, 11th edition..


texts: Predicting sigma bond overlap strengths of s-s, p-p, s-p, sp-sp etc

texts:
How can we qualitatively predict $\sigma-$bond strengths of overlap between:

$\ce{s-s}$
$\ce{s-p}$
$\ce{p-p}$
$\ce{sp-s}$
$\ce{sp-p}$
$\ce{sp-sp}$

etc.?

My school-book says $\ce{s-s}$ overlap bond strength is greater than $\ce{s-p}$ overlap which is greater than $\ce{p-p}$

Another book Inorganic Chemistry by JD Lee states this:

Are the facts stated in the above books correct or justified? Is there any order of orbital overlap strengths? If so can we predict it qualitatively?


texts: Basicity comparison between pyridine amines and other compounds

texts:
In cases 1, 2, 3, the compounds will resonate, thus giving them more stability.

Firstly, I want to know whether nitrogen has a +M effect? (due to it having a lone pair of electrons?)

In case 1, resonance occurs and the electron density above the $\ce{NH2}$ group is delocalised, even in the cases 2, and 3, this is true. But in 1 the $\ce{N}$ is at the para-position, while in 2 the $\ce{N}$ is at the meta-position. How would that affect the order?

It would help if someone could hint at the factors coming into play here.

Case 4 is non-resonating, so it would be the most basic, right? How do I arrange the rest in order?


texts: Why are most glow-in-the-dark things green?

texts:
I've noticed that many glow-in-the-dark objects you can purchase in the store are green. Occasionally I would come across something that was orange or blue, but mostly it seems that green is the ubiquitous glow-in-the-dark color.

Does this have anything to do with common wavelengths of light emitted from the relaxing of electrons in some of the more common phosphorescent compounds? Are some phosphorescent compounds just more readily available or "safe" for use in toys?


texts: How does Gaussian 09 normalize the excitation coefficients?

texts:
When I did excited state calculations with Gaussian 09, I was asking me on how those values are normalized because a simple sum over the squared of the coefficients did not yield 1.

So ... how are those coefficients normalized then?


texts:
In electrochemistry, the Nernst equation tells us the cell potential for non-standard conditions. I read that the factor $\frac{-RT}{nF}\ln{Q}$ accounts for difference in cell potential due to differing Gibbs Free Energy due to changing temperature and concentration.

This difference in Gibbs Free Energy is only due to entropy right? Because enthalpy is a constant? So obviously, entropy significantly interferes in the process of electrolysis.
And yet, it is ignored in virtually all spheres of chemistry. I'm beginning to doubt my chemical intuition because of entropy effects, and faith in it can only be restored if entropy really was negligible. So it is negligible or not? If not, why is it always ignored?


texts:
I am used to thinking of exothermic reactions as being defined as having negative $ΔH.$  However, I also am used to hearing/thinking of exothermic reactions as "releasing heat".

Since change in enthalpy $∆H = Q + VΔP,$ it seems that enthalpy and heat flow $(Q)$ are not strictly the same thing. Is it not therefore possible to have a reaction which absorbs heat $(+Q),$ but has a decrease in pressure, such that the product $-VΔP > Q,$ thus both absorbing heat and being exothermic (or if exo-/endothermicity is determined by $Q,$ then an exothermic reaction with positive $∆H)?$

As a sort of corollary, is there an example of a thermodynamic process that changes only the pressure (thus $V∆P)$ with no heat flow or $PV$ work? $(Q = 0 = PΔV)$


texts: What is the appropriate way of writing the Iron/thiocyanate equilibrium?

texts:
I understand the theory, but am struggling to answer the following discussion questions:

(i)
Why isn't this represented by: $\ce{Fe^{3+} (aq) + 3 SCN- (aq) <=>  Fe(SCN)3 (aq)}$
Why do we dilute the solution with water?

(ii)
I don't understand what the question is asking, can someone please explain

(iii)
I understand this.

(iv)
I am unsure, can someone suggest a reason.

(v)
I understand this.

(vi)
Constant volume of container?

ADDITIONAL QUESTIONS:

I thought ALL equilibrium reactions needed to be in a closed vessel - so if this experiment was conducted in an open test tube, wouldn't this be an error? How would this affect the accuracy of the results - would it be under/over estimated and why?


texts: How can the electronic structure of pentaaquanitrosyliron be explained?

texts: The magnetic moment of $\ce{[Fe(H2O)5NO]^2+}$ is 3.87 Bohr magneton, which implies that there are 3 unpaired electrons. Since iron is in $+1$ oxidation state (due to charge transfer with nitrosyl group), it's electronic configuration is $[\ce{Ar}]\ \mathrm{3d^7}$. Having 3 unpaired electron is only possible if the 4th and 5th electron enter the higher energy orbital $\mathrm{e_g}$ (crystal field theory). The $\mathrm{t_{2g}}$ or the lower energy orbital has 5 electrons. Why do the 4th and 5th electron enter $\mathrm{e_g}$ despite a strong field ligand (nitrosyl group) being present?


texts: Chemical kinetics of a reversible reaction

texts:
I am having trouble with the following question:

  Consider the following reversible reaction in which the reaction is first order in both
  directions: $$\ce{[A] <=> [B]}$$ $k_\mathrm a$ is the rate constant for the forward reaction and $k_\mathrm b$ is the rate constant for the reverse reaction.

  If only reagent $\ce{A}$ is present at $t = 0$, such that $[\ce{A}](t = 0)$ = $[\ce{A}]_0$ (and likewise for $[\ce{B}]_0$), then at all subsequent times $[\ce{A}]+[\ce{B}] = [\ce{A}]_0$. Write down a differential equation for $\frac{\mathrm d[\ce{A}]}{\mathrm dt}$ where $[\ce{A}] \equiv [\ce{A}](t)$ is the concentration of the reagent $\ce{A}$, and hence show that:

  $$[\ce{A}]=[\ce{A}]_0\frac{k_\mathrm b+k_\mathrm a \exp[-(k_\mathrm a+k_\mathrm b)t]}{k_\mathrm a+k_\mathrm b}$$

Here's my attempt:

$$\frac{\mathrm d[\ce{A}]}{\mathrm dt}=-k_\mathrm a[\ce{A}]+k_\mathrm b[\ce{A}]\tag{1}$$

Then using the identity in the question:

$$\frac{\mathrm d[\ce{A}]}{\mathrm dt}=-k_\mathrm a[\ce{A}]+k_\mathrm b([\ce{A}]_0-[\ce{A}])\tag{2}$$

Rearranging...

$$\frac{\mathrm d[\ce{A}]}{\mathrm dt}+(k_\mathrm a+k_\mathrm b)[\ce{A}]=k_\mathrm b[\ce{A}]_0\tag{3}$$

I believe that this is a first order linear differential equation with the integrating factor: $\mathrm e^{\int (k_\mathrm a+k_\mathrm b)\,\mathrm dt}=\mathrm e^{(k_\mathrm a+k_\mathrm b)t}$ Thus:

$$\frac{\mathrm d}{\mathrm dt}\left([\ce{A}]\mathrm e^{(k_\mathrm a+k_\mathrm b)t}\right)=k_\mathrm b[\ce{A}]_0\mathrm e^{(k_\mathrm a+k_\mathrm b)t}\tag{4}$$

$$[\ce{A}]\mathrm e^{(k_\mathrm a+k_\mathrm b)t}=\int k_\mathrm b[\ce{A}]_0\mathrm e^{(k_\mathrm a+k_\mathrm b)t}\,\mathrm dt\tag{5}$$

This gives me:

$$[\ce{A}]\mathrm e^{(k_\mathrm a+k_\mathrm b)t}=k_\mathrm b[\ce{A}]_0\frac{\mathrm e^{(k_\mathrm a+k_\mathrm b)t}}{k_\mathrm a+k_\mathrm b}+c\tag{6}$$

But this doesn't give me the final result if I put in the boundary conditions. Where have I gone wrong?


texts: I am looking for the names of some environmental alkylating agents (in context of DNA damages) found for example in the fume produced by industry. Most of the papers which I have found is concentrated on cigarette smoke, chemotherapy ect. I found something about methyl chloride, that is produced by plants and fungi, but also industrially. However there is no more details about that industrial part and in general the amount of methyl chloride in the air is rather low. Are there more relevant examples? Also I came across the information that alkylating agents may be found in food, but again there was no details.


texts: Is there a method to recover camphene from sublimation at ambient conditions?

texts:
Camphene solidifies and sublimates at ambient room temperature below 45°C. I'm aware that a glass funnel is often used to separate mixtures through sublimation of the volatile component (in this case camphene) from another material.

Is it possible to recover sublimated camphene using this or another method?


texts: I need a simple explanation of dative bonding. I am a student that has learnt simple covalent bonding and ionic bonding, but I need help to learn dative bonding. This if for an urgent assignment, so please help. Thanks.


texts: Predicting dissociation energy of diatomic iodine computationally

texts: In one of my classes we used ORCA with three different functionals: BP86, B3LYP, and M06-L, all with the basis set def2-SVP. In addition to calculations we did it experimentally by a Deslandres table and a Birge-Sponer plot. The experimental values for the most part match the values given in NIST, however for the three functionals my $D_{0}^{"}$ value is twice as big as the value given in NIST, and I don't know why. Thanks!


texts: SpectroVis spectrophotometer values changing after pulling cuvette out

texts:
I am required to write a research paper for school in a specific subject and I have chosen to write mine in chemistry.
I am investigating the kinetics of the Briggs-Rauscher oscillating reaction.
I am using a spectrophotometer to take samples of the reactants and determine the absorbance at 460nm every 45 seconds to calculate the rate at which iodine is produced.
However, I am using a spectrovis spectrophotometer, who's calibration values change without me doing anything and sometimes do not register the fact that iodine concentration has increased. Is there anyway I can fix this problem and prevent the readings from changing?


texts: Scientific Reason for Salt Solution Gaining Volume

texts:
A little background to this question: my mom placed a glass with salt and enough water to just cover the salt in a room to "absorb negative energy" out of the room at her office. It obviously "worked". So when I arrive home from university she asked me if salt water draws moisture out of the air — and explains to me what happened.

The scientist part of me is curious, because you cannot "absorb negative energy" using salt water. So I placed salt in a glass, covered it with enough water and left it overnight. To my surprise, the volume of water increased by around 20-25%, the glass is significantly more fill.

My question is this: why?

I have 2 thoughts:

Somehow the ions in the solution as the salt dissolved have charges that repel other molecules making more space in between molecules and therefore increasing the apparent volume.
Because it is a salt solution some form of osmosis occurs to actually absorb moisture out of the air.

My next idea is to redo this later today but weigh the glass and solution first to see if it gains mass. That would support 2. If no mass gain, then I assume something similar to 1 is happening.

Thoughts?

P. S. I am an applied mathematician so I have no background in the specifics of chemistry and how molecules and ions etc. etc. interact.

P. S. S.: I also couldn't find an answer to this on the internet. IN FACT salt added to water appears to reduce the volume in a lot of information I read.


texts: What was the experimental setup and/or reasoning that Amedeo Avogadro, in 1811, used to arrive at the conclusion that "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules"?


texts: Using group theory to make molecular orbital diagrams

texts:
Because of Orthocresols' meta post I ask this question about application of group theory to molecular orbital theory.

In my undergraduate lecturers, we've seen many examples of making qualitative MO Diagrams by inspection of what orbitals could line up to form bonding / anti bonding orbitals.

This works fine for simple things, but I know it's possible to use symmetry to also work out mathematically which orbitals can mix with which other orbitals by using group theory.

Perhaps using example of water could somebody show how this could be achieved?


texts:
Does Corey-Seebach reaction with conjugated enones undergo in a direct or conjugated fashion?

Can the two sulfur atoms soften the carbanion enough for it to undergo conjugated addition? If not, would addition of Cu(I) enhance the proportion of conjugated addition?


texts: Can nanotechnology reduce electrode losses in electrochemical cells?

texts:
I'm just curious about this topic, as most portable, "clean" energy sources or carriers (in the sense of not being a primary energy source -fuel cell hydrogen, for example) are in essence electrochemical reactors, and most of the current work in the field is aimed at reducing irreversible losses at the electrodes, be it because of discharge overpotential, or polarization because of mass transfer along the membrane electrolyte; and of course, in making this structural elements cheaper.

Also, a lot of proposed and existing waste treatment and recycling processes aimed at recovering rare and/or active metals (such as lithium from Li-ion batteries) involve at least one electrochemical unit op.

I wonder if nanotechnological advances, such as increasing the surface area of electrode materials or increasing the effecive diffusivity of relevant species in solid porous electrolytes, can reduce this irreversibilities, perhaps making use of cheaper raw materials than noble metals (i.e. platinum). I would also appreciate any references to current work in this applied field.


texts: Why does an OH bond absorb a higher frequency than a CH bond?

texts:
I'm wondering why a bond between an O and an H is going to absorb a higher frequency than a bond between a C and an H (any hybridization).

O is heavier than C in terms of atomic masses, and I'm assuming the O-H bond will be weaker because of the electronegativities, so why would it absorb a higher frequency?

Thank you.


texts: Filling a buret tip before an experiment

texts: I have a question that asks if the buret tip is not filled before the experiment what would happen (effect on molarity for acid/base titration). The way I'm thinking about it, it's not like you're putting a pre measured solution into it. You fill it as high as you fill it and you can't put anything in without getting the tip filled up too, so I don't see where that will change anything. Am I thinking about that right?


texts: How to interpret orbital transition in TDDFT?

texts:
Consider the following TDDFT run with GAMESS:

!   File created by the GAMESS Input Deck Generator Plugin for Avogadro
 $BASIS GBASIS=N311 NGAUSS=6 $END
 $CONTRL SCFTYP=RHF RUNTYP=ENERGY TDDFT=EXCITE  DFTTYP=B3LYP $END
 $CONTRL ICHARG=0 MULT=1 $END
 $TDDFT NSTATE=9 $END
 $STATPT OPTTOL=0.0005 NSTEP=99 METHOD=RFO UPHESS=MSP HSSEND=.T. $END
 $SYSTEM MWORDS=1000 PARALL=.TRUE. $END
 $SCF DIRSCF=.T. DIIS=.T. DAMP=.T. $END

 $DATA
Title
C1
O     8.0     0.00000    -1.27900     0.00300
C     6.0    -0.00000    -0.05800     0.00100
C     6.0     1.29700     0.69100    -0.00000
C     6.0    -1.29800     0.69000    -0.00000
H     1.0     1.35900     1.32900    -0.90600
H     1.0     1.35900     1.33200     0.90300
H     1.0     2.15700    -0.01300     0.00100
H     1.0    -2.15700    -0.01400     0.00100
H     1.0    -1.35900     1.32900    -0.90600
H     1.0    -1.35900     1.33200     0.90300
 $END

From this we obtain the following part of the output. (The complete calculation can be found here.) How can we interpret the orbital transitions, in terms of for example $\mathrm{n}\to\sigma^*$ or $\pi\to\pi^*$?


texts: Why are sigma bonds stronger than pi bonds?


texts: Copper plating with electrolyte not working (Cu(OH)2 vs CuSO4)

texts:
I've been experimenting using electroplating, and I recently made a solution by placing two copper pieces connected to a voltage source, in water. I suspect that this created copper(II) hydroxide, as it matches the color of that specific solution (green-blue) and doesn't stay dissolved in the water (it sinks to the bottom after a day).
A lot of people use copper(II) sulfate for an electrolyte during copper electrolysis, so I assumed $\ce{Cu(OH)2}$ would work the same, but if doesn't seem to be. A coin was attached to the negative wire, copper was attached to the positive wire, but attempting to copper plate a coin in this solution has failed.
Why is that? Both copper(II) hydroxide and sulfate have $\ce{Cu^2+}$. Shouldn't that be attracted to the negative wire, and append the copper to the desired item?
Why does $\ce{Cu(OH)2}$ not behave like $\ce{CuSO4}$ during electrolysis?
I don't know too much about chemistry so if you explain it in simple terms, I would appreciate it!


texts: Does BET theory apply to type H3 and H4 isotherm for calculating surface area?

texts: BET applies to type 2 and 4. That is basically unanimous.


texts: Can you determine whether a compound can form given particular elements?

texts:
Say you are given a set of particular elements, such as Dy, C, I, Er, P. Is it possible to determine whether a compound exists with all of the given elements and no more?

If not, is it possible to find this out if given the number of a particular element, such as; two hydrogen and one oxygen where you could come to the conclusion that $\ce{H2O}$ is possible.


texts: How does Boudouard reaction influence the temperature?

texts:
I've a question that is giving me a lot of troubles:
I'm depositing and gasifying Carbon by varying a flow rate of $\ce{CO}$ and $\ce{CO2}$ and by using the Boudouard reaction ($\ce{2CO -> C + CO}$). When I'm depositing carbon, I notice from my Temperature sensor at the outlet of the test-house, an increase of temperature (and I associate this both to the exothermic nature of the reaction but also to the fact that part of $\ce{CO}$ that didn't react is then burned into $\ce{CO2}$ in a furnace that surrounds my test-house. The problem is that I have a Temperature sensor also at the inlet and this shows a decrease of T when I deposit carbon and an increase when I am gasifying it (which is the contrary of what is expected). Do you know any possible reason for this strange behavior?


texts:
So I'm trying to figure out how to titrate the reducing sugars on honey without generating iodine.

The reaction so far I think I could do is do a Fehling reaction with $\ce{Cu}^{2+}$and then back-titrate the remaining with EDTA, but I'm not sure that the EDTA wouldn't solubilize the $\ce{Cu2O}$, or be able to displace the tartrate.

Some sources I've looked say that this can be done as a direct titration using methylene blue as an indicator, but they haven't given a pH range, even if the reaction is fast enough to be done as a direct titration.

Any thoughts?


texts: Why is the units of rate constant dependent on the order of the reaction?

texts:
In many textbooks, it is written that

For order (m + n), the rate constant, k has units of mol1−(m+n)·L(m+n)−1·s−1

However, by the Arrhenius equation, k can be expressed as

k = PZexp(-Ea/RT)

and its unit doesn't seem to change with the order.
I think if reaction velocity, v is defined as

v = k([A]/cref)m([B]/cref)n

like the definition of equilibrium, the unit of k becomes mol·L−1·s−1 and it looks more reasonable. Am I wrong?


texts: Do we use activities or concentrations in the rate expression?

texts:
The equilibrium constant of a reaction is a dimensionless quantity due to the fact that we use activities instead of concentrations(in moles/liter).
But, in the rate expression for a reaction, do we still use activities?

If this is so, then isn't the unit of the rate constant always (moles/litre-sec), since these are the dimensions of the rate of a reaction ?


texts: What are computed energies in DFT and FF methods relative to?

texts:
I am not talking about zero-point energy.

I wish to understand how the energy of a system is calculated relative to a zero baseline. This is best explained with an example.

From DFT, the energy could be:

Isolated H = -13.6 eV,
H2 = -31.8 eV

What are these numbers related to? What would be a system at 0 eV? Or what is the zero baseline from which these number are calculated from?

I have also noticed that force-field energies tend to be positive. What is the zero baseline here?

In summary:

What is the DFT baseline?
What is the Forcefield baseline?


texts: The major product of the following reaction

texts:
Here,1,2-dibromobutane is reacted with
i) alc. $\ce{KOH}$
ii) $\ce{NaNH2}$ in liq. $\ce{NH3}$

According to me, since alc. $\ce{KOH}$ causes dehydrohalogenation, using Saytzeff's rule the product obtained after reaction (i) should be one of the either:

And after reaction (ii), since $\ce{NH2-}$ is a strong base, an E2 reaction proceeds and again using Saytzeff's rule the final product should be:

However, according to the answer key the final product obtained is given as:

Can someone help by explaining where and how I went wrong in my attempt to solve the question?


texts: Will gaseous ionic compounds be free moving ions?

texts:
I knew while learning about electrolysis that if the ionic compound is molten it becomes free moving ions.

If that is the case, what will happen if I continued heating till it reaches the boiling point so that the ionic compound evaporates?

Will it still be free moving ions?

Also, shouldn't the result be more efficient at electrolysis than in the liquid state due to increased mobility of ions? If not, why?


texts: Do more double bonds cause a bigger number of stereoisomers in cycloalkenes?

texts:
If trans double bonds cause cycloalkenes to be chiral, does a second trans or maybe cis double bond induce another chiral plane and hence four stereoisomers are possible for the given cyclodiene?

The question is based upon these previous questions:
Are all higher cycloalkenes chiral?
Why is trans-cyclooctene chiral?


texts: Why does ammonia react with water to produce hydroxide?

texts:
My question relates to dissolving $\ce{NH3}$ in water and how it produces $\ce{OH-}$ for the reaction $\ce{NH3 + H2O -> NH4+ + OH-}$?

I know that the $\mathrm{p}K_b$ of $\ce{NH3}$ is $4.8$ and $\mathrm{p}K_a$ of $\ce{NH4+}$ is $9.2$ so $\ce{NH3}$ is a stronger base than $\ce{NH4+}$ is an acid. But why the free $\ce{OH-}$? I am now taking organic chemistry and all I am reading is how strong $\ce{OH-}$ is and how it can attack anything slightly positive. So why is the above reaction favorable towards creating $\ce{OH-}$?

Actually any acid-base reaction that is creating $\ce{OH-}$ as a free species?


texts: Sn1 mechanism and concentration of neucleophile

texts: Why is low concentration of neucleophile  preferred in Sn1 mechanism?


texts: Sodium Peroxoborate reacting with Sulfuric Acid and Potassium Permanganate

texts:
This is one of the reactions I had to undertake in a lab. I think the reason for the test in the first place is to test for the peroxoborate anion in the solution.

From my understanding what's happening is that sodium peroxoborate will liberate $\ce{H2O2}$ when reacted with sulfuric acid. Adding the $\ce{KMnO4}$, the hydrogen will react to reduce $\ce{Mn(VII) ->Mn(II)} $ and form $\ce{O}$

I'm having difficulty interpreting this into balanced chemical equations. This is what I've tried but not sure if it's correct

$$\ce{Na2[B2(O2)2(OH)4] + H2SO4 ->Na2SO4 +B2O3 +2H2O2 +H2O}$$

This equation shows the liberated $\ce{H2O2}$ but not sure how to write a reaction now where $\ce{KMnO4}$ is added.

Any help would be much appreciated. I've been strugging with this for a while and there isn't much information online.


texts:
I'd like to melt alumina in a slow, controlled manner.
So I thought a graphite crucible with a tungsten wire wrapped around it for heating would be a good start.  To reduce heat losses, I put that crucible inside an outer crucible.
Question 1 - can I get away with Al2O3 for the  outer one, given that the radial temp profile will be something like 1/r .  If not Al2O3 then what - Al2O3 would be nice as it has the lowest thermal conductivity that I can find of the refractory materials I looked at (W,SiC, C, BN)  .  And should I fill the annular space with e.g. YSZ powder (the quartz fiber I used to use for this kind of thing wont handle 2000C - is there some other fiber or 'wool' that can be used?)
Finally, can I zets the melt from above with microwaves conducted thru a waveguide - will the electrical  conductivity of the graphite be trouble or maybe help matters due to eddy currents?


texts: Confusion about direction of dipole arrow in alpha-helices and other molecules

texts:
I understand that molecular dipoles are electric dipoles. And electric dipole moment vectors point from the negative to the positive charge.

In class we learned to draw these special molecular dipole arrows (with a "plus" at the beginning) that point from the positive to the negative partial charge. I also see these arrows all over the internet, e.g.:

But for alpha-helices, the dipole moment points from the C to the N terminus. And the detail always shows the arrow pointing from the oxygen (negative) to the hydrogen (positive):

Should I just accept that even though an alpha-helix is a molecule like water, the "standard" way to draw its molecular dipole arrow is in the opposite direction than what people normally draw for water and other small molecules?

Edit: Another image, from a recent publication, but without macro-dipole arrow...:


texts: How to find the strongest base using stability arguments

texts:
Answers: The most acidic is D and the most basic is A.

So first off I compared A with B:

I'm kinda confused on this. I looked at the base NH one and saw that when it was protonated it lost its aromaticity. So as a result, the NH²⁺ one must be an unstable acid, thus it is the stronger acid. The stronger acid must have the stronger base on the same side, thus I concluded that A is stronger than B. Is this the correct way to think about it?

Then, I compared A with D:

I'm unsure about this as well.

When I compare the two bases on each side (the O⁻ and OH⁺ one), I see that the O⁻ one is more stable (on the left side), thus it is the weaker base, meaning the OH⁺ one (on the right side) is the stronger base. However, that is not right as A is the strongest.

However, when I compare the two acids on each side. I see that the OH one (right side) is more stable, thus it must be the weaker acid, so its conjugate base which is the O⁻ one must be stronger. This way of thinking got me the correct answer. However, I'm still unsure if this is the reason why as I was always told to compare the charged species.

Also E doesn't have a lone pair to donate, so I neglected that in the conversation of the strongest base. For C, it just didn't seem likely to me.


texts: What is the Purpose of an Electrolyte in a Galvanic Cell?

texts:
I understand how a galvanic cell works and the purpose of erverything such as the ssalt bridge and the electrodes, however I don't understand why an electrolyte is required. For example, consider this scenario.

I have a copper electrode in one beaker, connected by a wire with a voltmeter to a graphite electrode in another beaker. The copper electrode is immersed in water while the graphite electrode is immersed in lead ions. There is also a salt bridge connecting the two beakers. Now my question is, will there be a reading in the voltmeter?

I believe that there should be one since copper is more reactive than lead so copper ions will form while solid lead will form on the graphite electrode. However my school teacher said it won't work as there is no electrolyte in the first beaker. Why does it make a difference if there is an electrolyte or not?


texts: Sulfur belongs to the same group as oxygen. Then why oxygen exists as an $\ce{O2}$ molecule while sulfur exists as $\ce{S8}$ molecule? What's the chemistry behind this?


texts: What is a "period" of the periodic table?

texts: I'm familiar with the periodic table / periodic system, but I wonder why it's called "periodic" since there seems not much periodic about (there seems to be little or no predictability of which elements are stable) and from physics I know Z-value of elements and that is not periodic either. So what is a "period" in this context?


texts:
Why is weight of 1 mole of substance equal to atomic/molecular mass in grams?

According to me, it happens because mole has been defined in such a way. It is defined as the numbers of particles in $\pu{12 g}$ of $\ce{^{12}C}$. If it were $\pu{24 g}$ instead of $\pu{12 g}$, then the weight of 1 mole of substance would equal 2 times the atomic/molecular mass in grams.

Please correct me if I am wrong somewhere (or maybe everywhere).


texts: Can five membered ring form through Friedel-Crafts alkylation?

texts: Our teacher told us that five membered ring can’t be formed through Friedel-Crafts alkylation but acylation is OK. Why is that? Is it because alkylation is an unfavored 5-endo-trig reaction but acylation is 5-endo-dig, thus favored?


texts: How do you explain the formula Fe3O4 using the ionic compound theory?

texts:
I don't understand at all how the ionic bonding in $\text{Fe}$$3$$\text{O}$$4$ works. The oxygens all together have $4(–2e)=–8e$ net charge. But we cannot give the three irons equal positive charges to balance this: $8/3$ isn't an integer!
And anyways, what kind of iron is in $\text{Fe}$$3$$\text{O}$$4$? It can only be either Fe(II) or Fe(III), and none of them fits in here.

A diagram demonstrating the chemical structure of $\text{Fe}$$3$$\text{O}$$4$ with supporting explanation would be preferable. I'm only an 8th grader, so advanced chemical concepts won't be comprehensible to me. The lattice structure would be too huge for me to handle, so pointing out a single molecule/piece of that compound will be more helpful.


texts: Can you lower the alcohol concentration of a drink using vegetable oils?

texts:
The log POW of ethanol is −0.18 according to Wikipedia, i.e. in a two-phase system ethanol would preferrably accumulate in the aqueous phase, but not by much.

Suppose I wanted to lower the alcohol concentration in a drink, how well would adding some vegetable oil, mixing and removing the top layer with a straw work? What other parts of the drink are likely to accumulate in the oil? Which (unwanted) side effects can I expect?

Edit: Definition of Drinks

I'm interested in the effects on different types of drinks/alcoholic beverages from low-alcohol content beers to wines, whiskeys, vodkas and Stroh.

PS: While this may sound like a question for the cooking subsite, I am only interested in the chemistry.


texts:
I think I have figured out the IR spectrum for benzophenone. Would it be that the sharp peak in the middle (1700 cm^-1) is for the ketone and the little peaks pass 2900 cm^-1 rang are the sp2/sp3 carbons from the benzene rings?

Also, I have an H-NMR spectrum for the same compound and I know there are only three peaks because the compound is symmetrical. But I am confused on how to determine the J values for each hydrogen.

Can someone kindly assist?


texts: Fehling's solution - What is the shelf life of the unmixed A & B components?

texts: If you prepare two separate solutions of Fehling's A and Fehling's B, what is the shelf life likely to be? Will the effectiveness of the solution diminish over time? The literature recommends preparing these solutions separately and storing them in rubber stoppered bottles. I assume this means that atmospheric air will affect the solution. My thought is that carbon dioxide will dissolve in the solution and form an acid, which would lead to a false positive result later in the Fehling's reagent test for carbohydrates.


texts:
I am trying to keep a 1000 ml Erlenmeyer flask submerged in a deep cooking pot filled with water. I tried tying the flask to a metal plate, but it was too light unfortunately.

Is there a purpose built piece of equipment for this or a commonly accepted method?


texts: Why does the O atom of N-phenylnitrosamine donate its lone pair towards H+ when O is more electronegative than N?

texts: Nitrogen has lone pair as well which it can donate towards the proton but instead we see the oxygen being protonated despite being more electronegative. Also, this is not like the next part where $\ce{H3O+}$ is formed which is a good leaving group.


texts: Is the rate of an SN1 reaction really independent of the type of nucleophile?

texts:
Suppose we take two reactions

$\ce{(CH3)3CCl + H_2O \rightarrow (CH3)3COH +HCl}$

$\ce{(CH3)3CCl + CH3OH \rightarrow (CH3)3COCH3 +HCl}$

I know in $\mathrm{S_N1}$ reactions the RDS (Rate Determining Step) is the formation of a carbocation intermediate.

But I am quite certain that methanol is a more bulky and weaker nucleophile, as compared to water. Should that make the rate of the second reaction lower than the first reaction (after the RDS is crossed)?


texts: What does it mean if I am unable to write RS configuration for a compound?

texts:
We had to write all possible optically active monochloro derivatives of 2-methylbutane.
I was unable to write RS configurations for 1 and 3, since they have carbon atoms with more than one same groups attached to them (they are achiral). Does that mean they are optically inactive?
P.S. I’m still a beginner at this...


texts: Can I make a buffer from two different weak acids or bases?

texts:
Can I make a buffer using two different acids/bases? For example, adding 1 mole of acetic acid and 1 mole of ammonia?

The only information I can ever find is that I can make a buffer using only an acid (or base) and its conjugate base (or conjugate acid). So, carbonic acid and carbonate, $\ce{H2CO3}$ and $\ce{HCO3-}$.

Why do I need a conjugate acid-base pair and not two random weak acid-base pairs to make a buffer?


texts: Properties of a macroscopic amount of virus

texts:
The mathematics YouTube channel Numberphile just published a video entitled "All the World's Coronavirus Fits in a Coke Can" in which mathematician Kit Yates makes a Fermi estimate that all the SARS-CoV-2 coronavirus particles in the world would fit in a can of Coca-Cola (thereby missing the opportunity to make the pun that they would fit in a can of Corona beer).
What would the physical and chemical properties of such a macroscopic amount of coronavirus -- or even viruses in general other than coronavirus -- particles be? Would the mass as a whole seem solid or liquid-like? Would it be sticky? Would the viral particles attract or repel each other? What would it look like? Would it be transparent or opaque? What color, texture, smell, or other physical and chemical properties would it have?


texts: What is the chemical formula(s) for liquid potassium-based soap?

texts:
Many places say that liquid soap is generally potassium-based, while the solid stuff is sodium-based.
But, while I have found several sites saying that solid soap is usually sodium stearate, I can't find any place that gives a specific name(s) to the chemical(s) in liquid potassium soap...


texts: Can the steric nature of a carbon be quantified?

texts: With respect to this question as suggested by a user (he asked me to ask this as a separate question), I wanted to know if there is any way in which steric hindarance of an organic carbon be quantified, as to a value that would indicate how bulky a compound is.


texts: Resonance stability: ester vs. thioester

texts:
My problem set solution cites:

  "Although sulfur is less electronegative than oxygen, overlap is a
  more important consideration.  Sulfur is a member of the third period.
  As a consequence, a sulfur atom is larger than an oxygen  atom and the
  C–S bond is longer than the C–O bond, contributing to poorer overlap."

However, I don't quite understand why a longer bond length would contribute to poor orbital overlap, and how greater overlap contributes to more stability.


texts:
I understand that ate complexes can result from the addition of carbanions to neutral aluminum alkyls.

I was wondering what the balanced equation for this reaction is/what the structure would be in solid state - like does it dimerize?

$$\ce{2 LiCH2CH3 + Al2(CH2CH3)6 -> ?}$$


texts:
Is there an automatic way to generate conformers for radical like systems (spin multiplicity is doublet)? My system for the study is a substituted fullerene with a missing H atom from the functional group.

I have tried using different conformer generators for this purpose (Baloon, RDKit, Obabel, Fullmonte, CCDC's Conformer_generator) but none of them successfully yielded out any conformers. I do not know how to run MD of such a system for which there is no general force-filed available. I have also tried to go through the AMBER tutorial but was unsuccessful: http://ambermd.org/tutorials/basic/tutorial4b/

I would really appreciate if anyone can suggest something that actually works for the system in consideration.

Thanks in advance.


texts:
I have seen this reaction many times:

  $\text {Phenol}+\text{Zn}\ce {->}\text{Benzene}+\text{ZnO} $

But what is the mechanism?! Tried a lot but couldn't cook up one...

Thanks for any help...


texts: Mechanism of reaction between substituted aniline and potassium thiocyanate in presence of bromine and glacial acetic acid

texts:
Im currently doing this project where in we are synthesizing 2-amino-6-substituted benzothiazole by using p-substituted aniline with potassium thiocyanate in presence of bromine and glacial acetic acid.

My question is: how does the cyclization take place?

I know that the amino group of aniline is ortho and para directing so the phenyl thiocyanate is formed as the intermediate but then this intermediate reacts with bromine in presence of acetic acid to give 2-amino-6-substituted benzothiazole ... I do not get that step.

Please provide me with the mechanism as to how the cyclization takes place with those two reactants.


texts: How do I find the thermal effect of this reaction?

texts: I have graphite turning into diamond.I need to find the thermal effect of this reaction.How would one write that?I'm not sure how to proceed here.The teacher told us to use oxygen?


texts:
I came upon this box of matches, it's probably from a little before 1900 and has significance for my family history, and I would like to add it to my "box o' historical items" but I'm concerned about flammability.  I know that old negatives can combust spontaneously, is there a similar danger with matches?  Can the matches be chemically changed (by dipping the tips in something, for example) that will make them inert?

EDIT

This is a strange question as it straddles the line between history and chemistry.  I've also asked this question on history.stackoverflow.com.


texts: Why is the boiling point of water and ammonia so different?

texts:
Boiling point of water is 100 degrees Celsius, while boiling point of ammonia is minus 33 degrees Celsius, which makes 133 degrees difference. Now when we discuss value of boiling point, we also say that it depends on inter-molecular forces, and in case of both water and ammonia I can see two such forces: London dispersion forces and hydrogen bonds. Relative molecular mass of water is 18 amu, and relative molecular mass of ammonia is 17 amu, so unlikely we can explain the difference in boiling points by difference in London dispersion forces: as they depend on mass, the LDF should be about the same for two compounds. Speaking about hydrogen bonds, it looks as each molecule (water or ammonia) is able to form 4 hydrogen bonds. And in this way amount of hydrogen bonds again should be about the same. So what is an explanation for the difference in boiling point between water and ammonia?

UPDATE: I found some sort of explanation, which partially seems OK, but I see at least one problem with it though:

  Notice that each water molecule can potentially form four hydrogen bonds with surrounding water molecules. There are exactly the right numbers of δ+ hydrogens and lone pairs so that every one of them can be involved in hydrogen bonding. This is why the boiling point of water is higher than that of ammonia or hydrogen fluoride. In the case of ammonia, the amount of hydrogen bonding is limited by the fact that each nitrogen only has one lone pair. In a group of ammonia molecules, there aren't enough lone pairs to go around to satisfy all the hydrogens. That means that on average each ammonia molecule can form one hydrogen bond using its lone pair and one involving one of its δ+ hydrogens. The other hydrogens are wasted. In hydrogen fluoride, the problem is a shortage of hydrogens. On average, then, each molecule can only form one hydrogen bond using its δ+ hydrogen and one involving one of its lone pairs. The other lone pairs are essentially wasted. In water, there are exactly the right number of each. Water could be considered as the "perfect" hydrogen bonded system.

Source: http://www.chemguide.co.uk/atoms/bonding/hbond.html

OK, so each ammonia molecule forms 2 hydrogen bonds and so does each hydrogen fluoride molecule. Their masses are 17 amu and 20 amu respectively (difference is very small). Boiling point of fluoride is 19.5 degrees Celsius, while boiling point of ammonia is minus 33 degrees Celsius, which makes 53.5 degrees difference. So what is an explanation for the difference in boiling point between hydrogen fluoride and ammonia?


texts: Is there a real detection limit in NMR spectroscopy?

texts:
From what I've read, my impression is that with a sufficient number of scans etc., one can get spectra from even very dilute samples (S:N ratio ~ $\sqrt{\text{NS}}$). Obviously, this is not always possible in practice and it is not necessarily efficient use of instrument time.

However, assuming that (1) we have infinite instrument time and (2) the sample is indefinitely stable, is there still a true detection limit? If there is, where does it arise from?

[Unrelated: this question originally came about because I was reading a paper by Gschwind on CEST (J. Am. Chem. Soc. 2018, 140, 1855), but I realise that that technique is dealing with short-lived intermediates – hence my insertion of assumption (2).]


texts:
I wanted to calculate how many interstitial sites (tetrahedral and octahedral) are present in a simple unit cell and their location and radius.
I am guessing they are at the center of unit cell and at the center of each edge.
But can someone please confirm it and explain this in detail? Thanks


texts:
A reaction $\ce{A + 2 B -> C}$ is carried out in constant volume at $\pu{227 ^\circ C}$. the volume is $\pu{2 L}$. There is no $\ce{C}$ at the beginning. $[\ce{A}]_0 = \pu{0.035 mol L-1}$. $\ce{B}$ concentration changes over time.

  \begin{array}{l|cccccccc}
t~(\pu{min})& 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 \\
\hline
[\ce{B}]~(\pu{mol L-1}) & 0.09 & 0.066 & 0.05 & 0.039 & 0.033 & 0.028 & 0.024& 0.023
\end{array}

  a) At $t = 5$, what is the conversion rate?
  b) Calculate the reaction rate of $\ce{C}$ by using graph method according to $\ce{C}$ at time $0$ and $6$.
  c) Calculate the total pressure at time $3$.
  d) If this reaction should have done at constant pressure what would be the volume change rate?

I answered the a, c and d questions, but I am not sure about it. I can not solve question b, graph method, these were my exam questions and I want to know correct answers. Here are my answers:

Part a.

$$t = \pu{5 min}$$
$$\ce{\underset{0.035}{A (g)} + 2 \underset{0.09}{B (g)} -> C (g)}$$

$\ce{A}$ is a limiting reactant. At constant volume

\begin{align}
[\ce{A}] &= [\ce{A}]_0 (1 - x) \\
[\ce{B}] &= [\ce{B}]_0 - 2x[\ce{A}]_0
\end{align}

$$\pu{0.028 mol L-1} = \pu{0.09 mol L-1} - 2 \cdot \pu{0.035 mol L-1} \cdot x \to x = 0.886$$

Part b.

$$-\ln{(1 - x)} = kt$$
$$t = 6$$
$$0.024 = 0.09 - 2 \cdot 0.035 \cdot x \to x = 0.943$$
$$-\ln{(1 - 0.943)} = 6k \qquad \color{red}{?}$$

Part c.

$$p_T = C_T RT$$
$$0.039 = 0.09 - 2 \cdot 0.035 \cdot x \to x = 0.728$$
\begin{align}
[\ce{A}] &= 0.035 (1 - 0.728) = 9.52 \cdot 10^{-3} \\
[\ce{B}] &= 0.039 \\
[\ce{C}] &= [\ce{A}]_0 \cdot x = 0.035 \cdot 0.728
\end{align}
$$C_T = 0.074$$
$$p_T = \pu{0.076 mol L-1} \cdot \pu{0.082 L atm mol-1 K-1} \cdot \pu{(273 + 227) K} = \pu{3.034 atm}$$

Part d.

$$\epsilon = \frac{1 - 3}{3} = -\frac{2}{3}$$
$$V = V_0(1 + \epsilon x) \qquad \color{red}{?}$$


texts: Confusion in the name of this organic compound

texts:
I think the name of the above compound should be 3-Ethyl-2-methylcyclohex-1-ene. However, according to my book (Organic Chemistry Resonance DLPD, page #43, question #5), this organic compound is 6-Ethyl-1-methylcyclohex-1-ene.

A quick Google search shows relevant results for the later name but not for the former.

As far as I know as a high school student, substituents should be given the lowest number and double bonds should be given the number 1 whenever possible.

The name I thought of first satisfies these conditions better than the name the book gives as the answer.

What did I do wrong? Which rule did I not follow?


texts: Why does pouring soda slowly and smoothly seem to keep more of the carbonation?

texts: So, I caught myself gently pouring a can of soda into a cup of ice (making sure that there was room for air to move through so the stream of soda from the can to the cup was consistent and even) instead of just haphazardly tilting and dumping the entire thing in there as quickly as possible. I was doing this in part to prevent spills at my desk, but also to keep the carbonation present in the soda. This got me wondering: why does pouring soda quickly cause it to fizz more and lose carbonation?


texts: Wurtz reaction with two different alkyl halide

texts:
$$\ce{C5H11Cl + C4H9I + 2Na ->}$$
Is this possible in a Wurtz reaction? I want to add 2 different alkyl halides with two different halogens. I'm curious if two different types of halogen on the alkyl reactants is possible.


texts: How do I create a spreadsheet containing the coordinates and predicted bond angles, molecular properties, torsion properties, etc of a molecule?

texts:
On a previous answer here (https://chemistry.stackexchange.com/a/30841/876) I was informed in the comments that OpenBabel & Python terminal could be used to print the data contained in the property matrices of Avogadro (more info can be found here How do I print property matrices in Avogadro?). I should be clear, however, most of the files I want to be able to do this for are CIF files where the bond angles and lengths are not explicitly mentioned in the files, so these properties may need to be predicted by the software. So I felt I couldn't be the only person interested in this so I thought I'd ask this question on this site.

I would like any answer to be suitable for those operating on Windows machines, if possible. I have Python & OpenBabel installed on my 64 bit Windows 7 PC, so I believe this shouldn't be a major issue, hopefully.


texts:
I have a question that gives two concentrations and asks for the mass of HCl formed by the reaction.

I have two concentrations:

250mL of 4.00M $\ce{H2SO4}$, and

250mL of 1.00M $\ce{NaCl}$.

Here is the balanced reaction equation:

$\ce{H2SO4 + 2NaCl ->Na2SO4 + 2HCL}$

I know how to find the mass once I find the moles, molecular weights and then grams by multiplying the two.

However, how do I add those two concentrations? I assume the mixture will be at least 500mL, but how do I add the molarity?

Thanks!


texts: Do commuting operators always share the same eigenfunctions? Could you kindly explain to me if this is true or false and examples for this, as I am a little confused.


texts: Comparing basic strength order of amines

texts:
In the above question I was asked to compare the basic strength order.
So I did it like this:

The Nitrogen in I and II will not participate in resonance so the only effect it could produce is inductive (-I) .
Now the compound IV has less resonating structures than the other compounds so the the Nitrogen atom will have larger electron density.

So IV should be most basic then III > II > I because of (-I) effect.
But my book mentions (C) as the answer.

How? Any help will be appreciated


texts: How do three-electron bonds work in MO theory?

texts:
When we're taught MO theory in basic chemistry, a rule-of-thumb hammered into our heads is that an orbital takes up to 2 electrons with opposite spins. Sigma or pi bonds are represented by stable bonding orbitals. Orbitals sometimes have just the one electron (radicals) but are much more stable with the pair.

While this justifies the occurrence of one-electron bonds, like that of the dihydrogen cation, it does not smoothly explain the occurrence of three-electron bonds like in nitric oxide and dioxygen. If we draw a straightforward MO diagram for nitric oxide with the "two electrons per orbital" rule, we end up with a lone electron in a antibonding pi orbital. "Antibonding" seems to imply the lone electron is sitting at its host atom, but that's not the case. Where does this lone electron go? Does it "merge" with one of the bonding sigma or pi orbitals and if so how do we know which one? Is this just a shortcoming of MO theory?


texts: Carbon decrease from 1-octyne to 1-hexene

texts:
I am to turn 1-octyne to 1-hexene.

Method 1

1) Reduction using sodium metal in pure ammonia to an alkene.

2) Halohydrin formation; the -OH installs at the more substituted carbon due to its greater ability to stabilize positive charge (this always confused me; the more substituted carbon is both more positive in character and has more electron-donating methyl groups?)

3) Conversion of OH to a good leaving group (-OTs) using a sulfonate ester and a weak base, pyridine.

4) E2 elimination using NaOH and heat. Because of resonance and sheer bulk and negative induction the OTs(-) should make for a better leaving group than Br-. So the internal alkene is formed.

5) Two-part one step ozonolysis; creation of aldehyde.

6) Reduction of carbonyl with hydrogen and transition metal to terminal alcohol.

7) Conversion of terminal alcohol to a better leaving group using tosyl chloride and pyridine again.

8) Use of LDA to deprotonate and create the terminal alkene.

Method 2

Also we can take another route with the brominated alkene; we can use OsO4 and basic hydrogen peroxide to create a 1,2 (vic) diol, which can be cleaved by periodic acid, and this creates a primary alcohol, which we convert to a good leaving group using tosyl chloride and pyridine, and we can eliminate. Same number of steps, but just something different that I thought of. Well, perhaps slightly simpler since there isn't a need for a two-step process (ozonolysis).


texts: Does chloroantimonic acid exists? What do we get when we mix hydrochloric acid and antimony pentachloride and is the mixture stronger or weaker than fluoriantimonic acid. How about bromo and iodoantimonic acids?


texts: Why does O2 gets less compressed as compared to CH4 when pressure is applied

texts: As I understand that the compression depends on the attractive forces between the molecules. And considering that both $\ce{O2}$ and $\ce{CH4}$ dont have any dipole-dipole interaction with their respective molecules. The attractive forces should just be van der waals forces, that depend on mass and surface area of contact between the molecules only. $\ce{O2}$ having more mass and more surface area of contact than $\ce{CH4}$ (as $\ce{CH4}$ is spherical in shape) should be compressed more.


texts: What is exactly meant by position of equilibrium?

texts: I'm confused with the terms "position of equilibrium" and "equilibrium shifting towards left/right". I do have a vague picture that if a reaction shifts to the right, for example, it basically means that the reaction is now biased towards the products. But I'm not thorough with it. Does it mean that the rate of forward reaction is now faster than the rate of backward reaction, which would mean that the reaction isn't at equilibrium anymore?


texts: How is molecular orbital theory used in drug research?

texts:
I was reading up on MO theory and came across a particular section:

  Application: Computational Chemistry In Drug Design

  While the descriptions of bonding described in this chapter involve many
  theoretical concepts, they also have many practical, real-world applications. For example, drug design is an important field that uses our understanding of chemical bonding to develop pharmaceuticals. This interdisciplinary area of study uses biology (understanding diseases and how they operate) to identify specific targets, such as a binding site that is involved in a disease pathway. By modeling the structures of the binding site and potential drugs, computational chemists can predict which structures can fit together and how effectively they will bind.

Whilst I can see from the idea of in-phase and antiphase combinations of wave functions that you could potentially 'match' two atomic orbitals together but I am confused as to how this happens over a large molecule and the binding site of the target?


texts:
I've been taking an chemistry class online (for fun only) and one of the questions in the homework threw me a bit. Here's the wording:

"Draw the Lewis structure for a nitrogen atom attached to. two methyl groups ($\ce{CH3}$) and one oxygen atom."

OK, so I know that $\ce{NO}$ is a free radical due to the odd combined valence, i.e., the octet rule isn't satisfied. Will that carry over when the $\ce{NO}$ bonds with the two methyl groups?

Here's the sketch of what I did:

Lastly, what's the name of this compound? This is not part of the HW question; I'm just curious.


texts: How can I solve a non-cubic crystal structure?

texts:
Say I want to solve the crystal structure of barium sulfate, and I want to not only determine crystal type and the lattice parameter, but also the orientation of the oxygen atoms on the sulfate anion. How do I proceed? All I have is the powder X-ray diffractogram (i.e. intensity vs $2\theta$ for the compound).

I don't want to use any existing software as this is more about learning how crystal structures are solved. I have looked at books and they seem to be incredibly difficult to follow.


texts:
In general, fluoride ion affinity, ammonia binding energy, photoacoustic IR spectra of adsorbed species (pyridine, CO) are used to measure the Lewis acidity of a material.
But in the computer simulation method, such methods are not suitable to calculate nanoclusters Lewis acidity because of the susceptible electronic environment of the system
[if extra species placed near a nanocluster, nanoclusters change their configuration and
form chemisorption as nanoclusters are unstable (tend to form bigger species: nucleation.
Furthermore, it might be a global minimum (GM)].

Thus, I concluded that calculating electron affinity (EA) might be the most suitable method to calculate the Lewis acidity of nanoclusters (overall, not for each cation/active site).
What do you think about the method to calculate the Lewis acidity for the nanoclusters system?
or is there a method to calculate the Lewis acidity of each atom site for the nanoclusters system?


texts: How many watts would I need to get CO2 from 30 °C to 4000 °C in 1 hour

texts:
Scenario: After reading some articles on new sorts of ways to deal with $\ce{CO2}$ in the atmosphere, a question came to mind: If I had 100 kg of $\ce{CO2}$, and I would like to heat it up from 30 °C to 4000 °C in a given period (lets say 1 hour), how much energy would I need? What would that be in watts? And from there, assuming a solar panel with 20 % efficiency for 1 m² (therefore 200 watts/hour), what would be the area of solar panels needed to reach heat the $\ce{CO2}$?

Obs: From my very forgotten knowledge of Chemistry from high school, I found the specific heat for $\ce{CO2}$ should be 1000 to 1800 kJ/(kg K), and from this page http://www.heatweb.com/techtips/useful.html I got a formula and tried calculating it, but my units are probably all wrong, because the value was considerably low. I then multiplied 100 kg * 1500000 * 3970 °C. With the energy value, I divided by time (1 hour) to have the output in watts.

Obs2: I know that I am forgetting or do not know about many other limitations (such as the dissociation above a certain temperate). I also know that it would be inefficient and very costly, but would nonetheless like to find out the values, to try and figure what would be necessary for this procedure.

Question: Is this a viable way to do this calculation? What else should I consider?


texts: How come ancient Egyptian ink didn't fade during thousands of years?

texts:
This ink's main ingredients were charcoal, honey and gum arabica.

I understand charcoal is carbon and it would remain black for long time or forever just like coal. But gum arabica is organic and I would assume it would decay just like any organic material thus breaking the carbon bond and then carbon would've just turned into dust and disappear from papyrus or clay vessels, but apparently that's not the case.


texts: Is there a way to experience peppers’s endorphins effects without the burning sensation?

texts: When preparing dinner, my friend and I sometimes argue over the amount of pepper. It is often ‘too hot’ for him while I enjoy the heat effects (endorphins) of capsaicin (chili peppers) and piperine (black pepper). Is there a way to experience the endorphins effects of pepper without a burning sensation?


texts: How to use dispersion correction with M06-2x in Gaussian 09 or 16?

texts: I would like to perform an optimization calculation using the functional M06-2x using the BJ dispersion correction in Gaussian 0.9. However, I can't find the parameters for this functional as I found for example for B3LyP. Has anyone worked with this?


texts: Acidic strength of organic acids. Substituted PhCOOH acids

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Could someone please explain the order of acidity of ortho, para and meta substituted benzoic acids with the substituent as methyl group?
Methyl group operates +I and +R effect, I believe.


texts: How can chlorine have 10 electrons around it in chlorine trifluoride?

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I'm relatively new to chemistry, and while doing some exercises about $\ce{ClF_3}$ I tried to draw where the electrons are. I checked Google and got this:

How is this structure possible? From what I've learned from high school every element wants 8 valence electrons. From the figure, $\ce{F}$ has 8, but $\ce{Cl}$ has 10.


texts: I have prepared ferrous sulfate solution in water. After some time, brown precipitates observed. How to prevent the same?

texts: When ferrous sulfate solution is prepared in water, after some time, brown precipitates appear, how to prevent the precipitates.


texts: Can water be included in an ICE table if it is not the solvent and is a product?

texts:
The question that I have is whether you will count water in a Fischer esterification equilibrium problem where the equation is

carboxylic acid + ethanol --> ethyl acetate + Water

We need to find the concentrations of the different components at equilibrium and are also given the equilibrium constant. I know that if water is a reactant and the solvent you do not count it when finding x for the concentrations, however, in this problem, it is specified that the water is not a solvent and the moles of water are given. I've looked in multiple sources and none have said if there is an exception with water like this.

Also, in the problem, it only refers to the water as "water", so it doesn't state that the water is pure/a pure liquid.

Thanks!


texts: I am getting two different products based on the Cram and Felkin-Anh models as shown in the diagram. Any explanation?


texts: High specific energy solid material for cryogenic work

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I would like to know a few (solid) materials that have a very high heat capacity (specific heat?) that can absorb cold energy very well, and hold that cold for quite a while from 77K to 90K (at least 5 hours)

I am using a high tech stirling heat pump to cool down superconductors (along with very good insulation around the superconductors) to 77K. But I want to put that material around/on the superconductors, to maximise the time they stay cold. I would hold the heat pump against the material for perhaps 30 mins, and cool-down that material. Having an ability hold "cold energy" very well, and not release it too easily, would be needed. The material would need to handle cryogenic temps very well and not expand/contract too much (hence desire for a solid). That material would probably be inside a 2mm walled copper box (with superconductors strapped to the outside of that box)


texts: How would I find the molarity/concentration of a gas using pV = nRT?

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The problem I'm working on is:

At $\pu{1100 K}$ and a total pressure of $\pu{1 atm}$, $\ce{SO3}$ is $75.0\%$ dissociated.
$$\ce{2SO3(g) <=> 2SO2(g) + O2(g)}$$
Assume $\pu{1.00 mol}$ of $\ce{SO3}$ was present before dissociation.
Calculate the molarities of $\ce{SO3},$ $\ce{SO2},$ and $\ce{O2}$ at equilibrium.

I've already found the moles at equilibrium to be $\pu{0.25 mol}$ for $\ce{SO3},$ $\pu{0.75 mol}$ for $\ce{SO2},$ and $\pu{0.375 mol}$ for $\ce{O2}.$ I'm just not sure how to go about finding their molarities.


texts: What causes Starch's lump creation when solvent (butter/water/oil) is added and how to prevent them

texts: When liquid(water/butter) is added to starch lumps of starch are formed. Which are completely dry from inside. Adding more solvent doesn't seem to help therefore it is not a case of saturated solution. So what does cause the lump formation ? and how can it be prevented ?