texts: Oxidation of ethanedioic acid with potassium permanganate

texts:
What are the products of the reaction of 1,3-butadiene with hot $\ce{KMnO4}$ (excess)?

I know that $\ce{KMnO4}$ will first cleave the double bonds and we should get
$$\ce{CH2=CH-CH=CH2 ->[KMnO4] 2CH2=O + O=CH-CH=O}$$
Now the aldehydes will further oxidise to
$$\ce{H2C=O <<=> H2C(OH)2 ->[KMnO4] O=C=O}$$
$$\ce{O=CH-CH=O ->[KMnO4] HOOC-COOH}$$
I don't understand how and why $\ce{HO2C-CO2H}$ would further oxidise to $2 \ \ce{CO2}$?


texts: Why does the rusting process start from the bent/squeezed portion of iron?

texts:
I have noticed that the rusting of iron starts from the squeezed or bent parts of iron piece.
 I want to know what is the peculiar reason for the observation that rusting starts from bent or irregular surface than smooth part of a given iron piece and it spreads to everywhere.


texts: Can the enrichment of Uranium be done via manipulating the boiling/melting point difference between differing isotopes of the same element?

texts:
I have a Physics question for which I could not find the answer on the Internet, so I would like to see if y'all know the answer to it.
I have found that heavy water will have a different boiling point compared to light water, and this trend is present between various isotopes of an element. Based on this research, I have hypothesized that Uranium can be enriched using the procedure below.

Make UF6 (s)

Sublime it in a glass tube

Lower temperature with such precision, that one isotope of Uranium still remains in the gaseous form while another isotope has turned back into a solid.

Separate the gas and solid without disrupting the fragile temperature balance.

Although this link is for Germanium isotopes, it states that there is a 0.15 Celcius change of melting points between isotopes. https://www.sciencedirect.com/science/article/abs/pii/S0921452618300863
So, here are my questions.
Would this apply similarly to Uranium, and how would the use of UF6 affect this boiling point difference?
How exactly does the boiling/melting point change between differing isotopes? And is there a particular formula for finding the melting point for a particular isotope? (I assume it would take in the number of neutrons and some other info)
In addition, is it possible to adjust the temperature of the entire system with decimal grade precision?
Furthermore, would the above setup work at all?
Also, if UF6 is too sensitive, would melting Uranium metal in a kiln with decimal precision temperature adjustability work?
Finally, is there a good, reliable source for melting point differences between isotopes?
I would like to first say that this is all purely theoretical and that I will take no action upon the information obtained; it is all merely a thought experiment to enhance my understanding of Chemistry and Physics. I mean, it's not like I'm gonna make a nuclear bomb; I'm just a normal HS student in the US. If you still think that this information might be dangerous out here, please PM me so we might work something out, like meeting via Zoom/Skype/Phone or something; I am very flexible about that.
I hope y'all have a great day.


texts: Find the Linear Packing factor of FCC [-1 -2 1]

texts: I have been trying to figure out this question, and essentially if I assume that the only atoms that the vector touches are the starting and ending atoms, then I get 0.58. I am trying to find a more formal method for determining linear packing factor for any vector direction in a unit cell. Can someone explain how to do this question without the need more inspection?


texts: Why is the exo product formed in the Diels–Alder reaction between furan and maleic anhydride?

texts:
For most Diels–Alder reactions, the major product is endo because there are favourable interactions between the newly forming pi bond and the electron withdrawing groups of the dienophile.

Why is the reaction between furan and maleic anhydride an exception? From what I understand, the carbonyl groups of the anhydride are electron withdrawing.


texts: Can quantum entanglement affect the chemistry of molecules?

texts:
I recently heard a talk from a physicist about experiments on simple two-atom molecules in vacuum that showed that certain behaviour of the molecules was explained by quantum entanglement. Now this experiment was about creating holes in the inner electron shells of the molecule, so pretty much in the realm of physics and not chemistry. It was also performed in vacuum, and the lecturer himself said that in solution such an effect would likely be destroyed by frequent collisions in the solvent.

I was wondering if there are any examples of chemical behaviour of molecules that can only be explained by quantum entanglement. Does it ever play a role on the scale of chemistry, or is this effect just not relevant on anything beyond the small moleculs in vacuum stage physicists tend to use?


texts:
I'm looking for some suitable solvent for ether cleavage of Guaiacol (o-Methoxyphenol) using aluminium triiodide ($\ce{AlI3}$) with $\ce{DMSO}$. The original paper calls for using hot acetonitrile as a solvent, but I wonder what might be the alternatives. The ideal solvent would be some solvent with only mild toxicity.

What hydrocarbon solvents are a suitable replacement for this preparation?


texts: Why does phenolphthalein form in this reaction?

texts:
This reaction (http://orgsyn.org/demo.aspx?prep=CV1P0476) gives quinizarin as the major product in about 70% yield.

However, when the same reaction is conducted with phenol insteas of p-chlorophenol, the product we get is not 1-hydroxyantraquinone (as would be expected if we only knew the above reaction), but phenolphthalein.

Why does phenolphtalein form instead of 1-hydroxyantraquinone? Would 1-hydroxyanthraquinone form if we added only 1 mol of phenol instead of 2 in the phenolphthalein synthesis?


texts: What happens when you burn salt in paraffin

texts:
My 9 year-old son and I tried to do some extremely amateur flame testing...
We lit a paraffin burner [a little tin of paraffin jelly that came with a marshmallow 'smores' kit!] and sprinkled on about a teaspoon of salt. We got a brief yellow flame (as expected), which dimmed to blue. Then we simply let it burn for a while outside.
After a couple of hours, when it had all cooled down, we discovered that the salt had coalesced into a kind of mass. We removed it and found that it had the consistency of chewing gum. What was left behind was a clear, non-viscous liquid which smelled of paraffin.
We hoped to replicate the flame experiment, using more salt and the 'leftover paraffin' liquid. However, we found that the liquid is non-flammable!
I wondered if anyone could explain this. What exactly did the salt absorb that turned it into 'gum'? What liquid was left behind? And why is that liquid non-flammable?
(I'm delighted that we happened upon something strange and unexpected - much more interesting kitchen-chemistry than an Alka-Seltzer bottle rocket!)


texts: Can the ions of dissolved salts be physically separated with a strong enough external electric field?

texts:
Say you had a arbitrary amount of sodium chloride dissolved in water. Could an external electric field (e.g. the electrically charged plates in Millikan's oil drop experiment) physically pull apart the dissolved ions in the water if it was strong enough? What forces would it need to overcome?

If it is possible, how powerful would the electric field have to be? What would be the outcome if the $\ce{Na+}$ and $\ce{Cl-}$ ions were then physically separated into two different containers?


texts: Are there contradictions about intermolecular forces in the postulates of kinetic theory?

texts:
Regarding the postulates of the kinetic theory, in one place I read:

  There are no intermolecular forces except during the collision between molecules.

And yet in another place this appears:

  Collisions between two molecules do not exert unattractive or repulsive forces.

Aren't these statements contradictory? Are there or are there not intermolecular forces during the collision, according to the postulates of kinetic theory?


texts:
I have 50 ml of a compound I would like to purify. Since the impurities presents have close boiling points (b.p.), I have to use fractional distillation. Am I going to lose significant quantity of my product volume because of loss related to the distillation itself?

If so, what can I do to minimize the loss?

I thought about adding a higher b.p. solvent to the distillation flask so I can distill all the compound without leaving some in the flask. What do think about this method?

Are there any other strategies?


texts: Why is it that the bigger the side-chain is, its hydrogen atoms tend to be more equatorial?

texts:
The most stable cyclohexane form is the chair conformation but on the other hand, the bigger the side-chain of the cyclohexane is, its hydrogen atoms become more equatorial rather than axial, which brings them closer to the cyclohexane's hydrogens.
Shouldn't they arrange in a less energetic, but a more stable conformation?


texts: If an atom had 200 protons, how much neutrons would it need to have to be most likely stable and why?

texts: I know there is a specific proton/neutron ratio but i'm unaware if it applies to atoms with 86 protons and beyond.


texts: Improving protein solubility in Water solvent (food science)?

texts: I am trying to form a solution involving mixing my protein shakes. I am using a vegetable protein and it has poor solubility. Is their another protein I could use to entrap it to improve solubility? What (near) tasteless compound could I use to improve solubility?


texts: Explanation for bond lengths in trans-hexatriene

texts:
Hexatriene is an unsaturated hydrocarbon with six carbon atoms and five carbon-carbon bonds, three of which are double bonds.

However, the bond lengths of the $\ce{C=C}$ bonds are not the same. The middle $\ce{C=C}$ bond has a length of 137 pm while the $\ce{C=C}$ bonds at the end of the molecule have lengths of 134 pm, the length of a standard $\ce{C=C}$ bond. The two carbon-carbon single bonds are 146 pm long, also off from the standard 154 pm length of carbon-carbon single bonds.

Clayden's organic chemistry hints that the explanation has to do with the molecular orbits formed and the conjugation system in the molecule. However, I do not fully understand this explanation.

Why do these carbon-carbon bonds show this unusual bond length behavior? A thourough explanation using MO theory would be appreciated.

References

Clayden, J., Greeves, N., Warren, S. Organic chemistry, 2nd ed.; Oxford University Press: New York, 2012.


texts: Why don't we consider VΔP when we define Q?

texts:
We only define $Q = \Delta U + W_\text{exp}$ (expansion work = $-P\Delta V$).
If heat can cause $\Delta U$ and work, why work is defined only as expansion work in the first place where there are other forms of works, such as isochoric work ($=V\Delta P$)?

Let's say, there is a container with ideal gas $T, P, V$ and $V$ can't be changed by this container. I give it heat therefore $T, P$ changes to $2T$, $2P$. In this constant volume process, expansion work, Wexp is 0. That's why $Q_v = \Delta U$. In the mean time (in this constant volume process), $\Delta H = Q_v + V\Delta P$ and $V\Delta P$ is work done in constant volume process. My question is that why can't we just say this heat $Q = \Delta + V\Delta P$? Do we just ignore the non-expansion work? or is it included in $\Delta U$? or because the definition of $Q$ is $\Delta U+P\Delta V$ originally?

One more thing. I googled it all day and someone wrote that $V\Delta P$ is work in flow process. I can't imagine how matter can flow in the constant volume container, and even though it can flow, what is the relationship between $V\Delta P$? They didn't explain it why so my question get bigger and bigger.


texts: Why do ionic substances with higher lattice energies tend to be less soluble in water than substances with lower lattice energies?

texts: I understand that that energy is required to overcome intermolecular forces holding solute particles together in the crystal, but I don't understand how this relates to lattice energies and respective solubilities in water.


texts:
As far as I know, there have only few truly symmetric hydrogen bonds been observed. Unquestionable is the existence of it in the bifluoride ion, $\ce{[F-H-F]-}$, see also here. There are a couple of more, like in a water hydroxyl complex $\ce{[HO\bond{~}H2O]- @Cu($110$)}$,[1] or in the hydrogen disuperoxide anion $\ce{[O2-H-O2]-}$.[2]

Long time it was believed that malonaldehyde and acetylacetone[3] form keto-enol tautomers with symmetric hydrogen bonds. The reason for this is the lack of resolution of the experiments.

I recently came across the article about substituted malonaldehydes.[4] According to this, if you chose R1 to be an amine and R2 a nitro group, you could end up with a single well on the potential energy surface.

However, there is one response, that left me a bit puzzled. Henry Rzepa wrote:

  Searches of the Cambridge crystal structure database will reveal quite a number of instances of symmetrical hydrogen bonds. These are mostly homonuclear, ie N…H…N or O…H…O. Years ago, we came across a more unusual example, of an (almost) symmetrical N….H….O heteronuclear example (http://dx.doi.org/10.1039/C39890001722 ).

So apparently there exist many. Unfortunately, he doesn't extend us the courtesy of even a single example. If you look on Google Scholar, you do indeed find a few examples of symmetric hydrogen bonds. However, most of them are either "crystallograpically" symmetric, for charged species, or both.

Also Evangelista et al. conclude their paper about malonaldehydes with the following statement, which leads me to believe, that there is no such thing as a symmetrical hydrogen bond in a neutral molecule:

  A remaining goal is the identification of a substituted malonaldehyde with no barrier at all, i.e., a C2v equilibrium geometry.

Since then a few more years have passed, but my search did not turn up any more results.
Do symmetric hydrogen bonds in neutral molecules exist?

T. Kumagai, M. Kaizu, H. Okuyama, S. Hatta, T. Aruga, I. Hamada, and Y. Morikawa, Phys. Rev. B 2010, 81, 045402
S.J Knak Jensen , I.G Csizmadia, Chem. Phys. Lett. 2000, 319 (3-4), 220-222.
Daryl L. Howard, Henrik G. Kjaergaard, Jing Huang, and Markus Meuwly, J. Phys. Chem. A 2015, 119 (29), 7980–7990.
Steven Bachrach, 03 Feb 2009, Malonaldehydes: searching for short hydrogen bonds Also: Jacqueline C. Hargis, Francesco A. Evangelista, Justin B. Ingels and Henry F. Schaefer III, J. Am. Chem. Soc. 2008, 130 (51), 17471–17478.


texts: What would happen if you heat volatile/flammable material in a vacuum?

texts: Fire is an oxidizing chemical reaction, in the simplest sense it needs oxygen and fuel to burn in order to stay alight. But what reaction would you observe from a flammable substance like gasoline or lighter fluid in a vacuum?


texts: Do different oxidation states of the same element have the same emission spectrum?

texts:
I looked at the flames of copper (I) chloride and of copper (II) chloride through a spectroscope and they looked the same. The flame colour is the same too. But since they have different oxidation states, and therefore different electron configurations, should their emission spectra be slightly different?

Would this logic also apply, for example, to elemental sodium in a discharge tube, vs sodium chloride burning in a flame? Would their emission spectra differ?


texts: How can I easily identify if a substance is an acid or base based on its chemical formula?

texts:
I know of the Arrhenius definition, Bronsted Lowry definition and the Lewis definition for acids and bases but I don't know how to apply them on the spot. Also, some chemical formulas (such as acetic acid) throw me off since it has an OH at the end which causes me to think that it's a base when it really isn't.

Any tips/ways to identify if something is an acid or base simply based on its chemical formula?


texts: Why does the $V_{\mathrm{max}}$ of an enzyme not change with competitive inhibition? Shouldn't it decrease since there are fewer active sites?

texts:
My textbook states that $V_{\mathrm{max}}$ doesn't change for competitive inhibition. This makes no sense to me, since decreasing the amount of active sites available should lower the rate of an enzyme catalyzed reaction.

My attempt at rationalizing this is that $V_{\mathrm{max}}$ is dependent on the rate at which the enzyme/substrate complex dissociates into free enzyme + product by the equation Kcat * [E]. So, since it only takes into account the enzyme/substrate complex, we basically don't consider any enzymes with inhibited active sites.

Is that reasonable?


texts: Will Proving or Disproving of any of the following have effects on Chemistry in general?

texts:
I am working on a project relating to-
https://en.wikipedia.org/wiki/Millennium_Prize_Problems

I wanted to list the effects of them being proved or disproved in different aspects of science and maths. It was fairly easy to find such results on physics and maths as the questions primarily come up from them however I couldn't find any reference to effects it would have on our understanding of chemistry.

Is it because there will be no effect at all and that they are the least concern to chemists (in terms of applicability) or if there are then what are they?


texts: Why does gum get harder to chew after a while?

texts:
My Sister asked me this:

  "Why is it that when we chew gum,  it is soft and mushy to begin with , but slowly gets firmer and firmer like after 20 mins of chewing?"

I think  it is because when we initially chew gum it has plenty  of sugar causing rapid salivation and hence mushiness and the rubber polymer is very flexible to begin with and slowly looses its elasticity hence becomes firmer.

Is this the reason?

What is the chemistry involved ?


texts: By which mechanism would azide react with alcohols or alkyl halides?

texts:
$\ce{NaN3}$ produces $\ce{N3-}$ ions. So the reaction with an alkyl halide will either be $\mathrm{S_N1}$ or $\mathrm{S_N2}$.  After some reading, I found that $\ce{N3-}$ is a good nucleophile. Hence the $\ce{S_N2}$ mechanism is followed.
But if I use $\ce{HN3}$ on an alcohol, the $\ce{H+}$ ions produced will help in removing $\ce{OH-}$ as water forming a carbocation. So either $\mathrm{E1}$ (if the alcohol is tertiary) or $\mathrm{S_N1}$ (if the alcohol is primary or secondary) can take place.

Is this correct?


texts: Dehydration of alcohol with Lewis acid aluminum trichloride

texts: I am told that this method yields ONE equivalent of water, but I seem to get two equivalents of water. Also does this mechanism actually work? I've never seen anything like it, but it seems to make sense. Would another Lewis acid such as boron trifluoride also work?


texts: I have been searching around and have found varying answers to the question. What exactly would reaction of $\ce{H3BO3}$ and $\ce{NaOH}$ give? Shouldn't it be a neutralisation reaction as $\ce{H3BO3}$ is an acid and $\ce{NaOH}$ is a base?


texts: Does deprotonation of a hexaaquaion continue until neutral charge

texts:
I learned that deprotonation is the process in which a proton is lost from ligand $\ce{H2O}$ molecules surrounding a central metal ion (I am referring to hexaaqua ions). Also, the process continues until the charge of the complex ion is neutralized.

My question:
Why does it only continue until the charge is neutralized, why don't all the six ligand water molecules lose a proton?


texts: Saturation dissolved oxygen level at pressure

texts:
The saturation level of dissolved oxygen in contact with a moist atmosphere is

$$c = 0.21(p_\mathrm{atm} - p_\mathrm{vap}) K_\mathrm{H} M$$

where the $p_\mathrm{atm}$ and $p_\mathrm{vap}$ are the atmospheric and vapour pressures, respectively; $K_\mathrm{H}$ is the Henry's law constant, and $M$ is the molar mass.

If I take this volume of water away from the atmospheric interface, and reduce the pressure, does the saturation level equation stay the same as above, except swapping out $p_\mathrm{atm}$ for $p_\mathrm{local}$?


texts: What is the definition of thermodynamic stability?

texts:
The term thermodynamic stability is used on this site, but I can't find a good definition. Is is a quantitative or a qualitative concept? Does it apply to a single compound, or a pair of compounds? Does it a relative or an absolute value?
An answer to another question, Thermodynamic stability of benzene derivatives , states

Thermodynamic stability of compounds can be determined by obviously enthalpy of formation ($\Delta H_{_\mathrm f}$) of individual compounds. The enthalpy of formation will be lesser if the compound is formed from its constituent elements enjoys some greater stability.

The enthalpy of formation considers the synthesis of a given compound from the elements. If the enthalpy of formation of two substances like bromomethane and chloromethane are different, it might be due to differences in bond strengths (or electronic states) in the two compounds, or differences in bond strengths (or electronic states) comparing elemental bromine and elemental chlorine.
I do understand the concept of thermodynamically favored product. In this case, there are competing reactions leading to different products. Because they start with the same reactants, there is no issue about the reference state. However,  if I compare two substance with different composition (i.e. not isomers), I don't know what it means to compare their thermodynamic stability. I also understand local and global minima, as discussed in this answer which references a single set of atoms that undergoes transformation. The problem arises when comparing compounds with different sets of atoms.
Thermodynamics usually is pretty well defined. Thermodynamic stability, however, is a bit of a mystery to me.


texts: Synthesis of Haloperidol with 4-chlorobutanoyl chloride and piperidin-4-one

texts:
I searched for a easy synthesis on Haloperidol.

Step 1 and 2 are taken from https://www.slideshare.net/SagarJoshi2/antipsychotics-33785528 (Slide 23). I just tried to work out a way to prepare 4-(4-chlorophenyl)piperidin-4-ol via Grignard.

Does the 4-chloro group has any negative influence on the reaction.


texts: Why is solid sodium chloride white - and for that matter, why are the majority of salts white in solid form?


texts: Where does the water in an egg go on boiling?

texts: Our textbook says that boiling an egg causes coagulation and denaturation of the proteins present in it. Where does the water in it disappear?


texts: Why are indicators used only in the form of dilute solutions? I get that indicators are a form of weak acids themselves, and the extent of their dissociation varies with the pH of the solution they are in.


texts: What is the pressure point where deviations from ideal gas law occur?

texts: I read a lot on deviations from ideal gas law due to low temperature and high pressure and I understand it, but I am curious to what point (the value) does a pressure is considered HIGH pressure?


texts: Is there a mathematical way to determine the bond angles in a molecule without using the standard VSEPR model?

texts: I was wondering if anyone knew of a way to mathematically determine the bond angles in a molecule without using the standard VSEPR model. I was curious if such a thing exists.


texts:
My teacher gave us the equations for zero-order, first-order and second-order reactions as follows:

$$ [A]_t = -akt + [A]_0 $$
$$ \ln [A]_t=-akt+\ln [A]_0$$
$$\frac1{[A]_t}=akt+\frac1{[A]_0}$$

Where a is the coefficient of $A$ in the chemical reaction, but everywhere I've seen, the $a$ is not there. I have the Central Science 12th edition and there's no $a$ either, is my teacher right? Because that value does affect the answer.


texts: Chemical Biology - synthesizing/designing siRNA

texts: I was reading an article on siRNA, and from what I read it sounded like we can edit genes using siRNA. First, did I even interpret this correctly? Second, I read that siRNA was being used to create drugs to help correct mutations. Does this mean that they could also give positive mutations to people? Finally, how does the structure of siRNA differ from that of normal RNA?


texts: Regioselectivity of electrophilic addition of Halogen and Water (Halohydrin) on Alkenes?

texts:
I am currently studying for an organic chemistry exam and I just couldn't come up with a solution to the following question:
Consider the reaction of 1-Propene + Br2 with water as solvent.
Why will the nucleophilic water molecule add on C-2 and rather than on C1 of the Bromonium-Ion?
The answer seems to be, because in the transition state the bonding between Br and C will dissociate quicker than the bonding between O and C will form, which leads to a positive charge on that C-Atom in the transition state and therefore water will add on the more stable "carbokation-like" carbon.
My question is: why does the Br-C bonding dissociate quicker than the O-C bonding forms? (I read that in the pearson organic chemistry textbook). Does it have anything to do with the Hammond-postulate? Or are there any other thermodynamic or kinetics reasons? So I am basically searching for an explanation why one bond would dissociate quicker than a different bond would associate, because I guess that's the reason why there is a partial positive charge that would then be more stable on the higher substituted carbon...
Unfortunately I haven't found an answer on the internet yet and also not in other textbooks.
Maybe you can help :) Thanks!


texts: Given the pH optimum of Angiotensin 1, how do I determine its charge?

texts:
I'm given the following information

I'm then asked to determine the charge of the substrate Angiotensin 1 at the pH-optimum. I have found the pH-optimum to be 6.9.

How do I go about answering this question only knowing the optimum pH and the protein chain that Angiotensin 1 is composed of?


texts: What is the lattice structure of manganese?

texts: A transition element is defined as the one which has incompletely filled d orbital in its ground state or in any one of its oxidation state. Zinc , cadmium and mercury are not typical transition elements because they have fill filled d orbital in their ground state as well as in their common oxidation state. These elements do not show none of the characteristic properties of transition metals like the lattice structure as shown below in picture. They probably do not have proper metal-metal bonding, a characteristic feature of transition metals. But, still they are studied along with the chemistry of transition metals. But what about manganese? It is a core and important element in transition series. Here, X is unknown lattice structure.


texts: Working out pH of solution when excess NaOH is added

texts:
In a pH titration, $30\text{cm}^3$ of $\ce{NaOH}$ is added to $\pu{20 cm3}$ $\ce{CH3COOH}$. The concentrations of both solutions was $\pu{0.5 mol dm-3}$. $K_\mathrm{a} = \pu{1.7 x 10^{-5}}$ for $\ce{CH3COOH}$. Calculate the pH of the solution after all the $\ce{NaOH}$ is added.

Clearly, $\pu{10 cm3}~\ce{NaOH}$ is in excess. So moles $\ce{NaOH}$ in excess $= \pu{0.005 mol}$. Then in the mark scheme, it says $$\left[\frac{\ce{NaOH}}{\ce{OH^-}}\right]=0.005 \times \frac{1000}{50} = \pu{0.1 mol dm-3}$$ and I don't understand where this part has come from.


texts: If I have cider vinegar and want to calculate the total moles of acid found in it, how can I do it? I have the moles of NaOH and I know that it includes both acetic and malic acid but how can I combine them?


texts: Samsung's S-Plasma Ion - scientific basis

texts:
Has anyone come across a scientific study of the S-Plasma Ions that Samsung claims will purify air from microbes, allergens and free radicals? I would prefer publicly available research findings.

The following is a quote from http://www.samsungspi.com:

  The Samsung SPi generates Hydrogen atom ($\ce{H+}$) and Oxygen ion ($\ce{O_2-}$) which reacts together to form Hydroperoxyl radicals which the positively charged biological contaminants then reacts with three hydrogen elements of its protein structure before forming water vapor. Also, the Hydrogen atom ($\ce{H}$) will combine with $\ce{OH}$-radical to form a water vapor and neutralize harmful $\ce{OH}$-radical.

It also matches the description found on the product itself. See http://winniekepala.com/2011/03/ionizer-review-samsung-virus-doctor/ .

Here's a quote from the video on the same site:

  $\ce{H+}$ is born with the help of that plasma in this plus electrode. $\ce{H+}$ is hydrogen with a positive electric charge. Through the air, the $\ce{H+}$ moves to the minus electrode which generates electrons. In here, electron meets $\ce{H+}$ and active hydrogen like me are born.... The electron that is generated in minus electrode in the SPi ion device where [I] am born is naturally combined with oxygen. That is oxygen ion ($\ce{O2-}$). (Active hydrogen and oxygen ion together transform into $\ce{(H-O-O)-}$). $\ce{HOO}$($\ce{HOO-}$) ion envelops the positively charged airborne bio-contaminants and react with three hydrogen constituted of protein components, forming water vapor. This modifies the surface protein or breaks the cell membrane to remove bio-contaminants. $\ce{HOO}$($\ce{HOO-}$) ion reacts only with single cells such as virus or germ but does not react with the human body... $\ce{OH}$ radical is an active oxygen species and one of the highly reactive and strong oxidants. It can be harmful to human's body if exposed for a long time. (Active hydrogen combines with OH radical to form water vapor).

(It has numerous grammatical mistakes which I just copied verbatim).

I would like to know what are the various compounds and radicals mentioned in the explanation, and how the reactions above take place. What is the plasma in the positive electrode, and what is the potential difference between the electrodes that allows the generation of the active hydrogen and oxygen ions? What are the real chemical states of the active hydrogen and the oxygen ions? How do they combine to form the $\ce{HOO-}$ ion? What is the $\ce{HOO-}$ ion and how is it stable enough to go around the room? How does the active hydrogen combine with the $\ce{OH}$ radical?


texts: What functional groups are subsets of the Alkoxy group?

texts:
In a quiz, I was asked to find all of the combinations of organic molecule of $\ce{C4H6O2}$. The combination excludes -COOH, -OH, double bonds and the alkoxy group.

The only problem, as far as I am concerned, is the definition of the term "alkoxy group". According to this Wikipedia article, a Peroxy or Methelenedioxy should be one of the possible combinations allowed. However, the names do have the "-oxy" suffix in them. So I am uncertain whether to include Peroxy's and Methelenedioxy's in the list.

P.S. Below is a picture of the Methelenedioxy group and the peroxy group, respectively,  from the already mentioned Wikipedia article.


texts: Why can't nitrate ion in aluminium nitrate solution oxidise copper when a copper spoon is used to stir the solution?

texts: I have been recently studying electrochemistry and I came across the electrochemical series. A question was asked saying what will happen if a copper spoon is used to stir an aluminium nitrate solution,the answer was no reaction will take place as Aluminium is more stable in its ionic form and copper cannot reduce aluminium ion, but can't nitrate ion which is above copper in the spectrochemical series oxidize copper and be transformed into NO which is more stable than Cu. Why doesn't it happen?


texts: Would hydrogen bond form in these scenarios?

texts: My notes say that hydrogen bonding occurs between a hydrogen atom covalently bonded to a highly electronegative atom ($\ce{N, O, or F}$) and the lone pair of a highly electronegative atom of another molecule. I am wondering if hydrogen bond would form between a molecule with hydrogen atom covalently bonded to $\ce{N/O/F}$ and a molecule with $\ce{N/O/F}$ that has lone pair but is not bonded to hydrogen. For example, it seems like oxygen, ozone, carbon dioxide are soluble in water so they can form hydrogen bond with water though the $\ce{O}$ atom is not bonded to $\ce{H}$. How about $\ce{CH3CH2COCH2CH3}$, the $\ce{O}$ atom has a lone pair, but it seems like it is not soluble in water and cannot form hydrogen bonding with water.


texts: Interpreting from phase diagram whether O2 will float or sink

texts:
The normal melting and boiling points of $\ce{O2}$ are $\pu{-218 ^\circ C}$ and $\pu{-183 ^\circ C}$, respectively. Its triple point is at $\pu{-219 ^\circ C}$ and $\pu{1.14 Torr}$, and it's critical point is $\pu{-119 ^\circ C}$ and $\pu{49.8 atm}$. Will $\ce{O2 (s)}$  float or sink on $\ce{O2 (l)}$?

I quickly sketched the phase diagram of oxygen:

Pressure of the molecules will affect how compact the molecules are in solid and liquid, so I guess we can explain whether it will float or sink using the slope?

How does the slope tell us about the densities of $\ce{O2}$ solid and liquid ?

And in addition, how do I use intermolecular forces to explain this?


texts: How to evaluate enthalpy variation of combustion of sucrose in a constant volume calorimeter?

texts:
Consider combustion reaction (with the formation of $H_2O$ and $CO_2$) of a mass $m$ of  sucrose in a constant volume calorimeter with thermal capacity $C$. This reaction increases the temperature of $\Delta T$.

How do I find $\Delta H$ of this reaction?

Since $$\Delta U= C \Delta T= \Delta H+\Delta n_{gas} R T$$

I would use this formula, but what is $\Delta n_{gas}$ in this case? It should be zero (from textbook) but I do not undersand why it is zero. Furthermore, can I really use this formula even if $T$ is not a constant and there is a variation in temeperature in the reaction?


texts: I was looking at how to dissolve silver oxide (in a solvent). I know that monovalent silver oxide will not dissolve in water, but are there any solutions in which monovalent silver oxide will dissolve? I was looking whether they would do so in alkaline solutions, but I could not find anything.


texts: Is butanoic acid more soluble in water than ethyl acetate?

texts:
I was asked which of the two following isomeric compounds, a carboxylic acid and an ester, was more soluble in water.

I believe both molecules should be somewhat soluble in water as they have polar C=O and C–O bonds, which should allow them to form dipole–dipole interactions with water. However, I'm not sure how the difference in the structures would affect the solubility.


texts: How to purify water with activated carbon?

texts: If I am not mistaken, distilling water does not remove all possible impurities. Chemicals with boiling points less than $100\ \mathrm{^\circ C}$ will be transferred as well. Does the usual tap water contain such (I think there is at least fluoride.)? I read that activated carbon can be used to purify water as well. How is it done in practice? Suppose I first use activated carbon and then distill the water (or in the reverse order). How much impurities there would be still left?


texts:
We've learned in class that epoxide ring openings can be catalyized with acids, and I seem to recall either the professor or a classmate mentioning that they also react with bases, but some quick internet searching didn't turn up anything useful.  Do epoxide rings react with bases, and if so, what is the mechanism?

(Dis)claimer: this is just for my own curiosity/learning, and not being asked as a homework/test question (yet).


texts: The weight of a 2cc glass pharmaceutical flame sealed ampoule?

texts: This is one of the flame sealed type whose neck is broken before use. There seems to be lots of info on dimensions but none with regard to weight.


texts: Water and Ethanol Vapor Phase diagram for specific range

texts:
I am looking for a Vapor Phase diagram for Water and Ethanol where Ethanol would be from 0 to 5%.

The diagrams I have found are for Ethanol concentrations of 0% to 100% and this doesn't allow me the accuracy for the range I have in my process.

If anyone could point me to a table of values that the 0 to 100% diagrams are generated from I can generate a diagram for the range I am looking for.


texts: Reagent notation: meaning of dash(-) and line(|) or slash(\) in reagents

texts:
I've seen a lot of reagents which have a slash between two compounds, such as Lindlar's catalyst which is $\ce{H2}$ along with $\ce{Pd|BaSO4}$. I know that the sulphur is a poison here but in general, what does the \ or | mean? And is it supposed to be a \ or a |? Are both equivalent? Does it mean "and" or "or" or something else?
$\ce{Cr2O3-Al2O3/Mn2O3}$, Also what does the dash mean here? In?
EDIT: This in the context of the reagents mentioned above arrows in organic chemistry. If I'm not wrong,  $\ce{Cr2O3-Al2O3/Mn2O3}$ is used to convert hexane to benzene by cyclization followed by aromatization.


texts: Is it possible to form an 8 carbon ring using a Diels-Alder reaction?

texts: I need to convert the starting material to the product on the right but I was wondering if it was possible to use a Diels-Alder reaction and use $\ce{KMnO4}$ to cleave the ring.


texts: What's the difference between Carvacrol and Thymol?

texts:
What is the difference when it comes to separating Carvacrol and Thymol on HPPLC with reverse phase - C18 column?

Carvacrol elutes first, is that because it is ortho?


texts: Comparison of rate of reaction in bromination and chlorination

texts:
I did research, about this one but the data and other things prove chlorination is faster than bromination, because chlorine is more reactive. But, some data says reaction of chlorine is more exothermic then bromine, that is the reason. But, if this is the case, then according to me bromination should be faster. Because, less energy is needed to start bromination and less energy will be given out in formation hydrogen bromide.
And how reaction being more exothermic or less exothermic determines the rate of reaction?


texts: I have been searching google and didn't found any links that describes how  this process is performed - I mean the chemical procedure, not the process of taking the blood from the vein.


texts: Are atom coordinates in molfile necessary to produce a valid InChI identifier


texts: Water-water vapour equilibrium above the boiling point

texts:
Consider $\ce{H2O_{(g)} -> H2O_{(l)}}$ at $\pu{105^{\circ} C}$. Under these conditions it is false that:
(1) $T\Delta S_r$ is negative.
(2) Relative humidity is 100%.
(3) $|\Delta H_r|>|T\Delta S_r|$
(4) $P_{\ce{H2O_{(g)}}}>\pu{1 atm}$
(5) $|{\Delta G_f}_{\ce{H2O_{(g)}}}|=|{\Delta G_f}_{\ce{H2O_{(l)}}}|$

Been trying to understand this question. Here is my reasoning:

True, because $T$ is positive $\pu{(105 + 273)K}$ while $ΔS$ should obviously be negative because the final entropy is lower than the initial entropy. We are after all going from water's gaseous state to its liquid state. There are fewer degrees of freedom in water's liquid state.

If there is an equilibrium between water vapor and water liquid, then by definition relative humidity is 100%. The air is saturated with water vapor to the point where it can't even hold the water vapor and water vapor exists in a dynamic equilibrium with liquid water. From Wikipedia:

Saturated air is really just air which contains water vapor in equilibrium with a liquid water source.

False, because $ΔG$, not $ΔG^{\circ}$. $ΔG$ for a system at equilibrium is always $0$. $ΔG^{\circ}$, not necessarily $0$. So we have $0 = ΔG = ΔH - TΔS$. This implies $ΔH = TΔS$.

True. For liquid water to boil, vapor pressure must equal atmospheric pressure. Similarly for water to condense, atmospheric pressure must equal vapor pressure. Also, vapor pressure is solely dependent on temperature of the pure liquid. The below statement is from UC Davis' ChemWiki. I would think that adding solute would change the vapor pressure (and yes it does, and it's discussed further down the page of the site).

Vapor pressures are dependent only on temperature and nothing else.
Taking into consideration that water boils at $\pu{100^{\circ}C}$, we may conclude that at $\pu{105^{\circ}C}$, the vapor pressure of liquid water is greater than $\pu{1 atm}$. And therefore, for this equilibrium to exist, both the vapor pressure of liquid water and the atmospheric pressure of gaseous water must be equal and thus greater than $\pu{1 atm}$.

This is true. This would make $ΔG = 0$ since $ΔG = G_{\text{(products)}} - G_{\text{(reactants)}}$.

I would like to know if my reasoning is correct.


texts:
Is there a reasonably priced option for colorimetry at home? Is this even a good option to accomplish my goal?

I'd like to roughly determine the concentration of a chemical in an ethanol extract from a natural product. It has a definite color. I would be able to buy small quantities of the purified product from a chemical supplier. Based on my recollections of college chemistry, I should be able to make a solution of known concentration and compare them with a colorimeter to determine how much I've extracted. Would this be reasonable, or should I be looking at another way of doing this?


texts: How to determine the sign of the enthalpy of formation?

texts:
During the formation of $\ce{Al2O3}$ from 5.4 grams of $\ce{Al}$ and enough oxygen, the temperature of 2 kg of water climbs by 20 degrees. What’s the enthalpy of formation of $\ce{Al2O3}$ (per mole) ?

What I tried:

The balanced reaction:

$$\ce{4Al + 3 O2 -> 2 Al2O3}$$

5.4 grams of $\ce{Al}$ are 0.2 moles.
If 2 kg of water climbed by 20 degrees then 40 000 calories were invested during the reaction.
To get one mole of $\ce{Al2O3}$ we need 2 moles of $\ce{Al}$ , therefore the enthalpy of formation (per mole) of $\ce{Al2O3}$ is 400 000 calories. However, the correct answer is −400 000.

Can someone please explain the negative sign?


texts: I am using a calculation software called CASTEP, within Materials Studio, and I want to make a "movie" of my geometry optimization, but don't know how to. CASTEP allows one to do many many different types of calculations, and one of the simpler ones it does is a geometry optimization for a unit cell. I remember hearing that it was possible to show a "movie" of the geometry optimization. This "movie" would show all of the steps from the beginning atom positions in the unit cell to the final converged one. I don't know how to make this "movie" and was wondering if someone else knows how.


texts: How do I calculate the grams of a product after a reaction?

texts:
If you mix $50\,\mathrm{mL}$ of $2.5\,\mathrm{M}$ $\ce{HCl}$ with $100\,\mathrm{mL}$ $2.5\,\mathrm{M}$ $\ce{NaOH}$, you will get sodium chloride. If such reaction occurs only at $50~\%$, how many grams of sodium chloride will you get?

Well, I guess that the reaction is like

$$\ce{HCl + NaOH \to NaCl + H2O}$$

Since the concentration is the same for both reagents ($2.5\,\mathrm{M}$), I imagine that the concentration will be the same for the products?

So we got $2.5\,\mathrm{M}$ of $\ce{NaCl}$. However, to get the grams I first need to know the moles of $\ce{NaCl}$. I know that the concentration is $2.5\,\mathrm{M}$, but what of it? What can I do to get the moles of the resulting $\ce{NaCl}$?


texts: Reaction between Polyvinylpyrrolidone (PVP) and NaOH

texts:
I am using polyvinylpyrrolidone (PVP) as a dispersant in a reaction. The reaction contains concentrated NaOH (pH of the  NaOH solution is 12 to which PVP is added). When I add the PVP, the solution turns yellow. Should this happen?
I was thinking that because of this color change, maybe there is a side reaction that is occurring between PVP and NaOH. I found this article that says PVP reacts with sodium hydroxide to form a gel. But I could not find any other sources that mentioned anything like that article
The temperature of the solution is 25 °C and under agitation to help dissolve the PVP.


texts: Does DMT-Acetate become Polar in H2O, with added NaCl?

texts:
I'm extracting DMT (N,N-dimethyltryptamine) from Acacia confusa via acid/base. I extracted the DMT with $\ce{H2O}$ and acetic acid, converting it to DMT-acetate.  Here, I used a non polar solvent, naptha, to defat the material, causing an emulsion.

I used $\ce{NaCl}$ to break the emulsion, this caused a thick layer of black tar to form on top of the aqueous solution, and a glossy black tar on the bottom of the vessel.  I need to freebase the DMT acetate; however, I'm concerned that DMT-acetate migrated into one of the two polar layers.  (Correction: Either the non polar layer on top or gunk layer at the bottom)

How can I confirm if this is so? Does $\ce{NaCl}$ cause DMT acetate  (or any acetate) to become polar in $\ce{H2O}$? Why and how? Will the DMT acetate have migrated into any of these two polar layers?


texts: Determination of pKa and molar absorptivity coefficient using spectrophotometry

texts:
An indicator BPB (Brophenol Blue) is used and dissolved in solutions of various known $\mathrm{pH}$. Then, the absorbance of each solution at 590 nm was measured and the question asks for molar absorption coefficient of the $\ce{HIn}$ form and $\ce{In-}$ form at the 590 nm wavelength.
Derive the relation of absorptivity coefficient $\varepsilon(\ce{HIn})$ and $\varepsilon(\ce{In-})$ to the total concentration of indicator and also the $K_\mathrm{a}$ for the indicator.
Hint: plot the value of $A$ vs $\mathrm{pH}$.

I don't know how to interpret the resulting graph. I tried to derive a relation, but it is not linear with respect to $\mathrm{pH}$. Here I'm determining the relations of absorbance to $\mathrm{pH}$, trying to interpret the graph of $A$ vs $\mathrm{pH}$, but the relations are not linear.
$$[\ce{HIn}] + [\ce{In-}] = c(\text{BPB})$$
$$K_\mathrm{a} = \frac{[\ce{H+}][\ce{In-}]}{[\ce{HIn}]} \quad\to\quad [\ce{In-}] = K_\mathrm{a}\frac{[\ce{HIn}]}{[\ce{H+}]}$$
$$
\begin{align}
A &= \varepsilon(\ce{HIn})\cdot c \\
  &= b\cdot\left(\varepsilon(\ce{HIn})\cdot [\ce{HIn}] + \varepsilon(\ce{In-})\cdot [\ce{In-}]\right) \\
  &= b\cdot\left(\varepsilon(\ce{HIn})\cdot[\ce{HIn}] + \varepsilon(\ce{In-})\cdot K_\mathrm{a}\frac{[\ce{HIn}]}{[\ce{H+}]}\right) \\
  &= b\cdot[\ce{HIn}]\left(\varepsilon(\ce{HIn}) + \varepsilon(\ce{In-})\cdot\frac{K_\mathrm{a}}{[\ce{H+}]}\right) \\
  &= \frac{b\cdot c(\text{BPB})}{1 + \frac{K_\mathrm{a}}{[\ce{H+}]}}\left(\varepsilon(\ce{HIn}) + \varepsilon(\ce{In-})\cdot\frac{K_\mathrm{a}}{[\ce{H+}]}\right)
\end{align}
$$


texts: Why do tungsten and chromium have different electronic configurations?

texts:
Why is the outer structure of tungsten $\mathrm{5d^46s^2}$ instead of $\mathrm{5d^56s^1}$?

I try to explain this in comparison  with outer structure  of chromium $\mathrm{4d^55s^1}$  taking into consideration  5d orbitals have lesser energy than 6s orbitals in tungsten by saying that the size of the energy gap between the 3d and 4s orbitals lesser than size of the energy gap between the 5d and 6s orbitals, and the repulsion between electrons in the structure$\mathrm{5d^46s^2}$  more than  the repulsion  in the structure $\mathrm{5d^56s^1}$ which can push the electron from 5d to 6s to produce the lowest energy structure.

I need qualitative answer?


texts: What is the reason for decomposition of layered cathode materials?

texts:
Articles like this claim oxygen can evolve from layered metal oxide cathode materials when charging the Li-ion battery.
Is it the high positive potential given to the cathode while charging pulling the electrons from the chemical bonds of the cathode materials and thus cause the decomposition to evolve oxygen?
If not, what is the cause of the evolution of oxygen?


texts: Percent degree of dissociation of gas by pressure

texts:
I stumbled across the following interesting problem:

Assume that you have started to live on a new planet where standard pressure condition is $\pu{2 bar}$, standard concentration is $\pu{1 M},$ and all types of gases behave as an ideal gas. On this planet, you are asked to determine equilibrium conditions for the reaction below:
$$\ce{XY4(g) <=> X(s) + 2 Y2(g)}$$
$K^\circ = \pu{1.1455E-9}$ (at $\pu{298 K}$).
Calculate the percent degree of dissociation for $\ce{XY4}$ at $\pu{298 K}$ where total pressure is $\pu{0.2 bar}.$

Since the equilibrium constant is very small, I approximated that the pressure of $\ce{Y2}$ at equilibrium is insignificant. Therefore I got:
$$p(\ce{Y2}) + p(\ce{XY4}) = \pu{0.2 bar}$$
$$p(\ce{XY4}) = \pu{0.2 bar}$$
I don't know how to proceed from here though and how to calculate the degree of dissociation.


texts: Is it known for sure that bases feel slippery because of the production of soap/surfactant?

texts:
Discussion around the question Why does bleach feel slippery? has started me thinking about the saponification explanation for the slippery feeling of basic solutions.
According to Wikipedia:

Alkaline drain openers can dissolve hair (containing proteins) and fats inside pipes via alkaline hydrolysis of amide and ester respectively:
$$\ce{RCONH2(amide or proteins)+ OH− → NH3 + RCOO−}$$
$$\ce{RCO2R’(ester or fats)+ OH− → R'OH + RCOO−}$$

and just above that:

Essentially, the hydroxide ions from the basic lye attack the carbonyl carbons of the fat, which eventually kicks off the hydrophobic tails of the triglyceride (tristearin/fat) to isolate glycerol.

So I am not sure if the "saponification" explanation for why a small amount of a fairly strong base feels slippery between thumb and forefinger really says that the reaction has produced a true soapy surfactant or that it should really say that it is lubrication by glycerol-like compounds that generate the intense slippery feeling.
Wikipedia also says:

The Stratum corneum (Latin for 'horny layer') is the outermost layer of the epidermis, consisting of dead cells (corneocytes). This layer is composed of 15–20 layers of flattened cells with no nuclei and cell organelles. Their cytoplasm shows filamentous keratin. These corneocytes are embedded in a lipid matrix composed of ceramides, cholesterol, and fatty acids. (emphasis added)

Corneocytes are keratinocytes and named as such because of the abundance of keratin protein filaments they contain.
I seem to remember my very smart high school chemistry teacher telling us that the breakdown of protein was also important, but I don't remember the production of soap as being so central. So I'd like to ask if there is any actual empirical evidence - ideally with a scientific reference, that demonstrates which molecules present between the fingers in this situation is primarily responsible for the slippery feeling. Potential candidates might include:

Soap/surfactant,
Glycerol produced from hydrolysis of "finger lipids",
Broken down protein products, or
the pre-existing inter-cellular lipid layers that would be exposed by the removal of successive layers of cells within the stratum corneum.

below: Epidermal layers, from here.


texts: Can amorphous polymers have a melting temperature as well as their glass transition transition temperature?

texts: Above the Tg, amorphous polymers are described as viscous liquids. What then would they be likened to above their melting point, should they have one?


texts:
I am a little confused about how point groups give information about MO of polyatomic molecules.

Is it true that all molecules of a given point group such as, $\mathrm{C_{2v}}$, will have the same MO diagram, the only thing that will change is the number of electrons?


texts: Verifying data acquired from a molecular dynamics simulation

texts:
This question is about verifying a system simulated with MD. I am currently building a model of a two phase gas-liquid system, where I initially have $\ce{N2}$, $\ce{CO2}$, $\ce{Ar}$, $\ce{He}$ and $\ce{CH4}$ in the gaseous phase and $\ce{Na+}$ with $\ce{Cl-}$ in an aqueous phase, which is modeled with TIP3P water. The most abundant component of the gases is $\ce{N2}$, which comprises over 95% of the gas.

I have a certain, non-ambient $p/T$ setting with a relatively high pressure (30-40 kbar). My idea is to study partition coefficients using molecular dynamics in multiple different $p/T$ settings. I'm currently using OPLS/AA force field which models intramolecular potentials with harmonic potentials and intermolecular potentials through Ewald-summation and LJ-612 -potential.

Currently I have just equilibrated the system, so that $p,T,V$ and $E$ do not fluctuate much. Before moving onwards with this system, I would like to verify that it produces reasonable data which is on par with other classical computational simulations.

I have noticed that there are not many papers which have focused on a system similar to mine, and I'm probably not going to be able to find an exact match in which to compare to. So, while I've been looking through the literature, I've looked at the following parameters to get a feeling of how well the system is behaving:

Radial Distribution Functions (RDF).
Partition Coefficients of the gases.
Long term behaviour of the system (no odd behaviour such as crystal forming etc.).
Densities of phases ($\rho_{\text{gas}} < \rho_{\text{liquid}}$)

So far these have all been quite reasonable. Are there any other standard methods and/or values that I should be looking at? I am obviously constantly reading through literature to find other results for comparison.


texts: Mixing Supplements - Will the Distributions Remain?

texts:
I am combining various vitamins and minerals into a food supplement for my dog and I currently measure each powder individually for each batch of food each week.  The supplements are in powder form but have varying grain sizes.  Examples include copper, zinc, dicalcium phosphate, kelp powder, table salt, Vitamin E, Vitamin B-12.

If I were to make a giant batch of the supplements above using the proper proportions can I safely measure out of that large batch the appropriate volume each week or will the various consistencies / densities of the powders unevenly distribute making the weekly scoops proportionally unbalanced?

Is there some piece of equipment that could be used to mix the powders guaranteeing even distribution for batch usage?

Thank you in advance for any advice.


texts: Why is $\ce{N2}$ (dinitrogen) not a Lewis base even with two lone pairs?


texts: What happened to this stainless steel tool when exposed to vinegar?

texts:
Based on an article I found online about how to disinfect hygiene tools I've been soaking nail clippers and similar items in a mixture of white vinegar, dish soap, and warm water for a few hours in a plastic sandwich container.

So far it's been fine, but recently did it with a stainless steel cuticle nipper and after taking it out and rinsing it and drying it off, the metal had turned a dark gray color it's giving off a foul odor.

What happened to the metal, and is the tool still safe to use?

For reference, here is a photo of the tool (on top) and a different one showing what it used to look like (bottom).


texts: Why is hydroxide ion the strongest base only in water?

texts: My professor mentioned that hydroxide ion is the strongest base when we only consider aqueous solutions. Then why don't the strongest bases outside of aqueous solution, like superbase, remain the strongest in water?


texts: Convert lactose in milk to Galactooligosaccharides

texts:
There are few articles describing the conversion of lactose to GOS on Wiley Online Library with different enzymes. Yet none of them really talks about what % of the lactose in milk can be converted to GOS.

Is it possible to convert all lactose to GOS, and still be able to consume the milk/dairy product?


texts: We haven't learned this in class yet, but after looking online, and through my textbook, I can't seem to find a definite answer. I am hopelessly and utterly lost.


texts: Decrease of volume by half in equilibrium - with specific numbers- how to solve?

texts:
$$\ce{CO (g) + Cl2(g)<=>COCl2}(g)$$
  We have
  2 mols of $\ce{CO}$, 1 Mol of $\ce{Cl2}$,and 9.765 Mols of $\ce{COCl2}$
  contained in 1 L.
  The system is currently in equilibrium.

  We then decrease the volume by half to 0.5 L

  What will be the new concentration in equilibrium of CO?

I tried calculating at first the constant of concentration;

$Kc=\frac{[\ce{CoCl2}]}{[\ce{CO}]\times[\ce{Cl2}]}$

I found it to be $4.8825$

then I calculated the concentration with the new Volume:

$[\ce{CO}]= \pu{2mol}/\pu{0.5L}= \pu{4 M}$

$[\ce{Cl2}]= \pu{1mol}/\pu{0.5L}= \pu{2 M}$

$[\ce{CoCl2}]= \pu{9.765mol}/\pu{0.5L}= \pu{19.53 M}$

obviously this wasn't in equilibrium so I went to do this:

$\ce{CO + Cl2<=>COCl2}$

$4M-x$, $2M-x$,  $19.53+x$

(as the number of mols in the products is smaller and the system wants to fix the increase in pressure)

When I calculated all of this in the Kc formula it came to me that the Concentration of CO increased, and is now larger than 2 M ,
and in the textbook answers it is stated that it is supposed to be less than 2M, how is it possible?

I would be very glad for help with calculations and technique of solving as well!


texts: Could a 'polymer' be formed by hydrogen bonding?

texts:
For example, given you had a molecule with a carboxyl functional group on either side, could it form a continuous chain of dimers? I understand this may not fit under the definition for polymer but I lack better terminology to describe such a thing. For Example:
Alternatively;


texts:
I working on the Navy study guide for their nuclear engineering programs and I am not a Chemist.  Thus, I have come here to try and develop a better understanding of the subject matter.

Why is pH important in materials selection?


texts: How does polarimetry account for the orientation of the molecules?

texts: If you have some sample in solution (of a pure R substance), wouldn't the individual molecules all have a random orientation in space? Or do the photons emitted into the solution cause all of the molecules to align? Or is it just that, statistically, a given percentage of the particles will have an orientation which corresponds to the polarized light source.


texts: Writing pressure equilibrium constant expression for a reaction with a single solid product

texts:
How would you write the $K_\mathrm p$ expression for the reaction: $$\ce{4 Ag(s) + O2(g) \rightarrow 2 Ag2O(s)}$$

I know normally it would be products over reactants, but there is a solid on the product side and they aren't included, so I don't know how you would write it?


texts: How would you determine the RDS from the rate and order of a reaction

texts:
I know what a rate determining step is, and also have knowledge about zero order and first order reactions. But, in one of my tests, I was unable to solve the following question:

  A hypothetical reaction A2 + B2 --> 2AB has a rate law, Rate = k[A2]1 [B2]0 and mechanism of reaction is

  Step-I: B2 --> 2B

  Step-II: A2 --> 2A

  Step-III: 2A + 2B --> 2AB

  The correct statement is

  A) Step-I of mechanism is rate determining step of the reaction

  B) Step-II of mechanism is rate determining step of the reaction

  C) Step-III of mechanism is rate determining step of the reaction if step I and II are reversible

  D) Step-I and Step-III both are rate determining step of the reaction if step II are reversible

The correct answer is option B, but how would you approach the problem and solve it?

EDIT: What if rate was given as

1) Rate = k[A2]1 [B2]1

2) Rate = k[A2]2 [B2]1


texts: Deuteration of following enone - mechanism?

texts:
What happens when the above compound is subjected to DCl in MeOD? As a result of tautomerism, I'd expect at least 7H atoms, two alpha to carbonyl carbon (right side), and five at gamma position (two on one position and three on the other); to be replaced with deuterium.

However, I'm not clear about the mechanism that'd be followed to achieve the same. And at the same time I'm not sure if there will be an 8'th replacement at alpha position to the carbonyl carbon (left side).

I know that the hydrogens on the right alpha position is replaced due to enolization and I think I got the mechanism for this, but the rest is a blank for me at the moment.

If someone could please help  provide a detailed mechanism, it'd be really helpful. Thanks a lot.


texts: Calculating Equilibrium Partial Pressures Given Kp and Mass

texts:
For the reaction
  $$\ce{AsCl5(g) <=> AsCl3(g) + Cl2(g)}$$
  at $550$ K, the equilibrium constant ($K_p$) is $9.81$. Suppose that $3.150 \ g$  $\ce{AsCl5}$ is placed in an evacuated $600$ ml bulb, which is then heated to $550$K.

  What is the partial pressure of $\ce{AsCl5}$ at equilibrium?

So at the moment, I understand that
$$\ce{K_p=$$\frac{(P_{AsCl3})(P_{Cl_2})}{(P_{AsCl_5})}$$}$$
And that using a rearranged Ideal Gas Law I can get
$$\ce{P=$$\frac{n(0.0125mol AsCl5)*R*T(550K)}{V (0.6L)}$$}$$
Giving me $$\ce{0.94 atm}$$
but I'm not sure where to go from here. Can somebody help by pointing me in the right direction?


texts: Why do certain groups withdraw/ donate electron to double bond or conjugated system in resonance effect?

texts: Why for the Resonance effect certain group of substituents/functional group donate electron from the double bond or to a conjugated system while some withdraw electron from the double bond or to a conjugated system? What causes the groups/substituent to withdraw or donate electron causing +R and -R effect?


texts: Will O or S accept an electron more easily?

texts: O has more electronegativity than S but S has more Electron Gain enthalpy than O. How do we decide, which one pulls the electron more easily? In other words, Electron gain enthalpy dominates or electronegativity ?


texts: Measuring energy required or generated in gasification

texts:
The typical equation used to measure heat is as follows:
$q = mcΔT\\
\text{Where, }\\
q = \text{heat} (\pu{J}) \\
m = \text{mass} (\pu{g}) \\
c = \text{specific heat capacity} (\pu{J g^-1 K^-1})\\
ΔT = \text{change in temperature} (\pu{K})$
This is meant to measure the change in thermal energy (i.e. net potential energy of a system).
Gasification is a process that takes hydrocarbons (often fossil fuels) and produces carbon monoxide, hydrogen, carbon monoxide, and several other substances (as a gaseous mixture) by submitting it to a gasification agent. Sometimes oxygen is used, though other agents can be used; nonetheless, combustion does not take place. The mixture is known as syngas.
The process occurs in settings where temperature is greater than $\pu{700 °C} (\pu{973.15 K})$. However, I am not entirely certain how energy is measured — I imagine we are using changes in enthalpy.
If anyone has knowledge of this subject, please enlighten me. Gasification and syngas are espoused as alternatives to recycling and incineration (since the latter are not always environmentally friendly or economically feasible).


texts: Oxidation and reduction in organic chemistry

texts:
Why is it that in order to make an carboxylic acid from an alcohol you oxidise it twice...

ie alcohol + 2[O] ---> carboxylic acid

...but to get back to the alcohol you reduce it four times?

carboxylic acid + 4[H] ---> alcohol

My understanding was that oxidation is the opposite of reduction, and in organic chemistry [O] means addition of an oxygen atom or removal of a hydrogen atom, with [H] meaning the opposite.


texts: Is there a difference between energy levels and electron shells?

texts: Is there any difference between energy levels and electron shells, or do they mean the same thing? Does the number of energy levels remain constant when progressing across a period?


texts:
Why is zinc oxide yellow when hot and white when cold?

Is it yellow because of the flame used to make it hot?


texts: Why is $\mu=0$ for p-dinitrobenzene ? How can the dipole moments of the two Nitro groups exactly cancel each other ? Shouldn't it have a non-zero, albeit feeble, dipole moment ?


texts: How is phosphoryl chloride attaching an aldehyde to benzene?

texts:
This reaction was part of an organic scheme I was doing:

I thought that $\ce{POCl3}$ just converts the OH group into Cl, but looking at the chemical formula for A, I noticed that A has an extra carbon compared to the starting material.

It turns out that A is

I'm very confused as to how that aldehyde group was added to the benzene ring. Where is the additional C coming from?


texts: sp2 hybridized carbon versus sp3 hybridized silicon

texts: Carbon's most commonly found allotrope is graphite/soot/fullerene/carbon nanotubes which are all $\mathrm{sp^2}$ hybridized forms of it, while silicon being its first periodic twin is mostly found in the $\mathrm{sp^3}$ hybridized form in bulk, while formation of silicene is extremely difficult. While in the case of carbon, diamond is the one which is harder to find, what is the reason for this discrepancy?


texts: What can be done to increase the yield of a product in a chemical reaction that has reached equilibrium?

texts:
Let's take the following reaction that has reached equilibrium

$$\ce{CaCO3 (s) <=> CaO (s) + CO2 (g)}$$

What can be done to increase the yield of calcium oxide ?

My initial thought was to remove the carbon dioxide produced in the reaction mixture. I understand that this is correct since, according to Le Chatelier's principle, the reaction would shift to increase the yield of the products.

Why wouldn't adding more calcium carbonate lead to a shift to the products and hence lead to a greater yield of the products? Doesn't more reactant mean more product?


texts:
Why doesn't my stainless steel Thermos get really really hot? Seems like a fairly straightforward question.

A few notes:

I was looking and found (obviously different values because steel is an alloy) that $$0.35~\mathrm{\frac{J}{g\,K}}\leq C_{p,\,\mathrm{steel}}\leq 0.55~\mathrm{\frac{J}{g\,K}}.$$
Obviously, that is just a rough range, but that is a very small heat capacity as is usual of metals.

Why then, does my 200 degree Fahrenheit coffee not heat up the stainless steel mug super quickly!

And even more baffling to me: Why in the world would it be a really good insulator?

It's entirely possible that I am devoid of any understanding of how insulation works, but I thought things which are bad conductors of electricity made good insulators. While stainless steel isn't praised for its electrical conductivity, I thought a material had to be about as bad as a gas at conducting electricity to be crowned with the title of "good insulator." I would just imagine that stainless steel, being metallic in many ways, would be a better conductor than that.

So what's going on? Why isn't my Thermos reaching 200 degree Fahrenheit?


texts: Are SN1 reactions pseudo unimolecular first order reactions?

texts: I believe the the Solvent (present in excess) helps in ionisation of R-X to carbocation in Rate Determining step so shouldn't the Rate Determining step be a pseudo-unimolecular reaction as 2 molecules are involved but solvent species has no role in determining the rate?


texts: Differences between phenols and alcohols

texts:
I know phenols are more acidic as compared to alcohols, but are they considered different from alcohols?

Sure, you can study something as a subset, but are phenols considered a subset of alcohols, or are they considered as completely different from alcohols? My confusion is due to the fact that both of them contain a hydroxyl group.


texts: How to add two hydroxy groups to 1,5-diphenylpentan-3-ol with as high as possible yield?

texts:
From 1,5-diphenylpentan-3-ol (above), how to add the two hydroxy groups in red (below)?
Is there any proven successful synthesis route to 1,5-diphenylpentane-1,3,5-triol with higher yield (40 % or above)?


texts: How can I know which molecule is more stable when bond order it's equal?

texts:
So, I was wondering, I have these molecules $\ce{O^+2}$, $\ce{O^-2}$, $\ce{O2}$ and $\ce{C^+2}$.
When I try to find their bond order and their magnetic nature I get this:
$\ce{O^+2} = \frac{1}{2} \left( 10 - 5 \right) = 2.5$ - Paramagnetic
$\ce{O^-2} = \frac{1}{2} \left( 10 - 7 \right) = 1.5$ - Paramagnetic
$\ce{O2} = \frac{1}{2} \left( 10 - 6 \right) = 2$ - Paramagnetic
$\ce{C^+_2} = \frac{1}{2} \left( 7 - 4 \right) = 1.5$ - Paramagnetic
You can note that $\ce{O^-_2}$ and $\ce{C^+_2}$ have the same bond order and are also paramagnetic, but how can I know which one is more stable so I can arrange them in stability order if $\ce{O^-_2}$ and $\ce{C^+_2}$ have the same orders?
Thanks!


texts: What is the mechanism of this pyrylium synthesis?

texts:
In this preparation, http://www.orgsyn.org/Content/pdfs/procedures/CV5P1106.pdf, 2,4,6-trimethylpyrylium perchlorate is prepared from 4 molecules of acetic anhydride and 1 molecule of t-butanol.
However, I cannot find a mechanism of this reaction, nor can I think of one. Could someone please provide the mechanism? Thanks.


texts: Can different groups within a single molecule photoisomerize at different wavelengths?

texts:
Azobenzene undergoes trans → cis photoisomerization when irradiated with light with a wavelength of 300–400 nm.

By adding electron withdrawing groups, the wavelength can be red-shifted.

If I were to make the molecule shown below, would it be possible to selectively photoisomerize around each of the $\ce{N=N}$ at different wavelengths?


texts: Neutralization of alkali solution by a mix of strong acids

texts:
$\pu{0.1 M}$ $\ce{HCl}$ and $\pu{0.2 M}$ $\ce{H2SO4}$ solutions are mixed in equal volume. This solution is diluted to double the volume. Find the volume of $\pu{0.1 M}$ $\ce{NaOH}$ which can be neutralized with $\pu{20 mL}$ of the former solution.

The answer is $\pu{50 mL}$.

I have tried a bit, but the answer I get is wrong. Let volume be $V$ at the beginning, therefore, no. of moles of $\ce{HCl}$ is $0.1V~\pu{mol}$, no. of moles of $\ce{H2SO4}$ is $0.2V~\pu{mol}$.

Total volume of solution after dilution is $4V$, therefore, no. of moles of $\ce{H+}$ in the solution is $(0.1V + 0.4V)/4V$.

No. of moles of $\ce{Cl-}$ in the solution is $0.1V/4V = 1/40$.

No. of moles of $\ce{SO4^2-}$ in the solution is $1/20$.

Since $\ce{NaOH}$ reacts only with $\ce{Cl-}$ and $\ce{SO4^2-}$, therefore total moles of $\ce{NaOH}$ needed is $(1/20 + 1/40)(20/1000) = 1/100~\pu{mol}$

Therefore, $\text{volume needed} = \text{molarity/no. of moles} = 0.1/0.01 = \pu{10 L} = \pu{10000 mL}$.

I Don't Know what I am doing wrong.

I tried again using some of the suggestions given: for the first step of mixing H2SO4 and HCl, M1V+M2V=M3(2V),
which comes as M3=0.5/2.
Then for dilution,
(0.5/2)*2V=M4*4V
thus M4=0.5/4.
Taking 20ml, (0.5/4)*20=0.1*x,     [0.1M of NaOH]
thus x=25ml.
Why doesn't this work??


texts: Use of concentrated sulfuric acid in Fischer esterification

texts:
Concentrated sulfuric acid is often used as a catalyst in Fischer esterification reactions. To my knowledge, the role it plays in the reaction is not as a reducing agent or dehydrating agent but only serves the role of creating an acidic environment, as seen in the mechanism.

Thus, dilute sulfuric acid would be sufficient. In fact, it would be better since it ionises to give an even more acidic solution. However, chemists choose to use the concentrated one instead, suggesting that the role of sulfuric acid is more of a reducing agent. Is there a reason for this?


texts: How to calculate Lennard-Jones potential with quantum mechanical methods

texts:
I want to know the procedure to calculate the Lennard-Jones potential for a metal-halogen pair (specifically vanadium-chlorine). Is it possible to calculate using any QM packages like Mopac, NWChem, or Gaussian?

I am specifically looking for values of A and B in the 12-6 potential.


texts: How to prevent Ag2O from decomposing to Ag on Aluminum

texts:
I have silver oxide in an ink formulation. When I apply it (in small quantities) over aluminum and heat the resulting (to evaporate the solvent), the monovalent silver oxide seems to decompose to Ag. The temperature I am evaporating the solvent is around 30-40˚C. The decomposition of Ag2O to Ag occurs at a temperature over 200˚C. However, I am aware that aluminum is a good conductor of heat, so even though the temperature was only 30-40˚C, Ag2O could have deposed because the temperature on the aluminum surface could have been around (or higher than) 200˚C.

My question is, is there a way to solve this problem. How can I still use aluminum and not worry about decomposing Ag2O to Ag when evaporating the solvent? Do I have to further reduce the temperature and is this the only solution? I tried to research this concept but couldn't find anything.

Thank you so much for your help.


texts:
newbie here.

I'm asking a question that is related to hygrometer calibration.

I read in sensitive digital hygrometers, it is stated that saltwater test should not be used to calibrate as it will damage the electronics (resistor?) that is used for measurement.

But how does this ring true? Saltwater does not evaporate, or do they?


texts: Phosphoric acid has basicity of 3 i.e it can loose 3 $\ce{H+}$ while phosphorous acid has basicity of 2. Why is phosphorous acid more acidic than phosphoric acid? Acidity refers to the ability to liberate protons. Phosphoric acid liberates more protons than phosphorous acid (as the basicity of phosphoric acid is 3 and that of phosphorous acid is 2). Why then is phosphorous acid more acidic than phosphoric acid?


texts: Is it possible to form bubbles of ionized hydrogen and ionized oxygen under the right pressure/temperature conditions during electrolysis of water?

texts: When we run a current through water (pure or not), $\ce{O_2}$ forms at the anode while $\ce{H_2}$ forms at the cathode. If I understand correctly, as water is already slightly ionized, $\ce{H}$'s snap together (and so do $\ce{O}$'s) during the electron exchange. Is it possible to apply enough heat or enough pressure to water to prevent $\ce{H}$'s and $\ce{O}$'s from snapping together and so we could thus form bubbles of ionized hydrogen and ionized oxygen?


texts:
Look at the structure for sulfate:

Why does sulfur form so many covalent bonds. Its valency is only $-2$, it only needs two electrons, yet here it's getting $6$.

The same thing happens with phosphate.

Phosphorus has a valency of $-3$, yet, it forms $5$ covalent bonds.


texts: Is it likely that increased understanding of quantum physics will change our understanding of chemistry?

texts:
Reading that the large hadron collider will be up and running with twice as much energy in March 2015, I was curious whether our understanding of subatomic particles has changed our understanding of chemistry.

Edit: To attempt to narrow down the question to something with a definitive answer: has the discovery of subatomic particles changed experimental chemistry?  If so, what is an example?


texts: Relative levels of the two most prominant glutamate species at pH 4.7

texts:
Calculate the relative levels (i.e. ratios of concentrations) of the two most prominant glutamate species at pH 4.7.

I know that the Henderson–Hasselbalch equation is to be used which is
$$\mathrm{pH=p}K_\mathrm a + \log_{10}\mathrm{\frac{[A^-]}{[HA]}}$$

For one glutamate species, this would change to
$$\mathrm{4.7=2.19 + \log_{10}\frac{[A^-]}{[HA]}}$$

and for the other species it would be
$$\mathrm{4.7=9.67 + \log_{10}\frac{[A^-]}{[HA]}}$$

I know there are some other variables I need to figure out to solve the equation, but I'm not sure how to go about finding them with the information given.


texts:
I am expanding $2p_{x},2p_{y},2p_{z}$ (slater type )orbitals in gaussian STO-3G basis as follows,

$$|2p_{x}\rangle=C_{1}x\exp(-\alpha_{1}r^{2})+C_{2}x\exp(-\alpha_{2}r^{2})+C_{3}x\exp(-\alpha_{3}r^{2})$$

$$|2p_{y}\rangle=C_{1}y\exp(-\alpha_{1}r^{2})+C_{2}y\exp(-\alpha_{2}r^{2})+C_{3}y\exp(-\alpha_{3}r^{2})$$

$$|2p_{z}\rangle=C_{1}z\exp(-\alpha_{1}r^{2})+C_{2}z\exp(-\alpha_{2}r^{2})+C_{3}z\exp(-\alpha_{3}r^{2})$$

I thought the value of $C_{1},C_{2},C_{3},\alpha_{1},\alpha_{2},\alpha_{3}$ are the same for all the $p$ orbitals. I tried to evaluate the following two integral $$\langle2p_{x}2p_{y}||2p_{y}2p_{z}\rangle=\langle2p_{x}2p_{y}|2p_{y}2p_{z}\rangle-\langle2p_{x}2p_{y}|2p_{z}2p_{y}\rangle$$
where,
$$\langle2p_{x}2p_{y}|2p_{y}2p_{z}\rangle=\sum_{i,j,k,l}C_{p_{x}i}C_{p_{y}l}C_{p_{y}j} C_{p_{x}m}\int d^{3}\vec{r_{1}} \int d^{3}\vec{r_{2}}  x_{1} e^{-\alpha_{i}r_{1}^{2}}y_{1}e^{-\alpha_{l}r_{1}^{2}}\frac{1}{|\vec{r_{1}}-\vec{r_{2}}|}y_{2}e^{-\alpha_{j}r_{2}^{2}}z_{2}e^{-\alpha_{m}r_{2}^{2}}$$
The above integral vanishes completely. I think something went wrong in the basis I have chosen or does it really vanish ? I guess my STO-3G expansion is wrong. Can someone help me fixing this please ?


texts: Effective nuclear charge and repulsion of electrons

texts: Effective nuclear charge increases across a period. This is justified because number of protons increase in nucleus across a period, and there's no change in the number of "shielding" electrons. However, wouldn't valence electrons repulse each other? Why does this repulsion not seem to matter for effective nuclear charge?


texts: Carbocation rearrangement with expansion of five-membered ring?

texts:
I am confused with this particular problem.

I began the problem with a mechanism as following. In the beginning $\ce{H+} $ protonates the alcohol and leaves as $\ce{H_2O}$. Then everything is about carbocation rearrangement.

But then my professor gave out a different answer saying that ring expansion doesn't happen.

Why doesn't ring expansion take place? Isn't a six-membered ring more stable than a five-membered ring? I am not sure where I am making the mistake.


texts: How Can I Induce Corrosion Electrochemically?

texts:
I'm very interested in measuring corrosion in metal alloys, particularly in salt solutions. I understand metals corrode over time, however, I was wondering if it's possible to electrochemically "speed up" or induce further corrosion in saline solutions? How would I go about this electrochemically? I've considered applying a specific current / potential and utilising it to induce oxidation, however, I have not found much in the way of literature actively seeking to induce / speed up corrosion, most are content to investigate over longer time periods.

Many thanks.


texts: What makes ceramic coated pans fail? Is it reversible?

texts:
If one reads reviews on ceramic glazed cookware (esp. frying pans) one pattern becomes apparent: the pan is awesome at first, nothing sticks to it, even with little to no oil. Then, after a few months the non-stick properties more or less plummet and the pan may become worse than stainless steel pans.

As to why that is, I've read multiple claims. Some say (or assume) that the non-stick layer erodes/dissolves/gets damaged. But to my humble knowledge ceramic is harder than steel, so that seems somewhat simplistic of an explanation. Some sources say that the coating reacts with oil when overheated (which will happen on high settings of the stove) and that residue is what dimishes the non-stickiness.

That sounded more plausible to me and I wondered if that proccess can be reversed/undone in some way?

So the first part of my question: how does a ceramic pan deteriorate? If it's not plain "erosion", what can be done to restore its properties? I'm afraid to scrub if harder for the fear of scrathing it.


texts: Specific conductance of 0.1 M acetic acid

texts:
Find specific conductance of $\pu{0.1 M}$ acetic acid given that its molar conductivity is $\pu{4.6 S * cm2 * mol^{-1}}$.

I used the formula $\Lambda_m = \kappa/c$, where $\Lambda_m$ is the molar conductivity, $\kappa$ is the specific conductance and $c$ is the concentration of the electrolyte in $\pu{mol/L}$.

What's confusing me is the value of $c$. At first I thought it should be the given molarity, but according to my text book $c$ is the concentration of the electrolyte. Now the acetic acid molecule does not conduct electricity, rather its constituent ions do. So shouldn't the value of c be the concentration of its ions which turns out to be $\pu{\sqrt{1.8} \times 10^{-3} mol/L}$ (using the equation of the acidic dissociation of acetic acid)?

Also the answer given was $\pu{4.6 \times 10^{-4} S * cm^{-1}}$.


texts: What is the influence of glass type on silver mirror making?

texts:
I'm considering the reaction wherein ionic silver (from the dissolved nitrate) is reduced by glucose in the presence of NaOH and forms a metalic silver layer on glass.
Reading through several topics here on stackexchange it seems that it still hasn't been clearly elucidated what exactly is happening on the glass surface for reduced silver to deposit onto / bind to it (instead of just precipitating out as a powder in solution).
I'd like to know if/how glass type might affect the process:
Can I get as perfect of a mirror on a borosilicate surface as on pure SiO2 glass?
Is the silver layer in either case uniform or will is be porous at the molecular level?
I've read that a slow reduction is key. Is it so that a silver mirror is qualitatively better produced at lower temperatures (or with highly diluted reagents) over a long time than by gently heating the solution?
Could a large temperature gradient between the solution and the glass surface be advantageous for the reaction to proceed much faster on the surface than in solution (e.g. mixing a solution at 10C into a glass container whose surface is brought to 80C)?
How can the process be optimized to produce a perfectly insulating silver layer at the molecular level?


texts: Predicted number of signals in proton NMR spectroscopy

texts:
Given the molecule,.

I can predict that there will be 4 signals present in the NMR spec. Problem is, the quiz says 5 is the correct answer. My question is, are alkene hydrogen not chemical-shift equivalent?


texts: What's causing my energy calculations to be wrong?

texts:
I'm calculating the energy density of certain flammable compounds in MJ/kg. To do this I compare the sum of the bond strengths of the reactants to the products and then extrapolate the energy density from the difference in the molar binding energy of each compound.

For methane my result was almost exactly 50 MJ/kg while the Wikipedia result says it's 55 MJ/kg.

For ethanol my result was 28.6 MJ/kg while Wikipedia says it's 26.4 MJ/kg

I don't expect my calculations to be spot on but I didn't expect them to be this off.

What are the possible reasons for my calculated energy density to be quite different than the supposed actual values?


texts:
In perturbation theory, wave function of a perturbed system can be expressed in a power series of some $\lambda$ as $\psi^{(0)} + \lambda\psi^{(1)}+\lambda^2\psi^{(2)}......$.

Then we express Hamiltonian operator as $H^{(0)} + \lambda H^{(1)}$.

Introduction of $\lambda$ in $\psi$ can be understood but why we introduce $\lambda$ in Hamiltonian operator and what is the significance of this $\lambda$ factor.


texts: Which molecule has maximum bond angle amongst BF₃, BCl₃ and BBr₃?

texts:
$\ce{Br}$ is the least electronegative from the given compounds. So, in $\ce{BBr3}$ the electrons will be the closest towards boron and thus due to electron-electron repulsions $\ce{BBr3}$ will have maximum bond angle.
Steric hindrance due to large size of bromine atom can be a factor too.

But the bond angles are same according to most of the websites.


texts: Aromatic ring substitution: how are MNT and DNT further nitrated if nitro groups deactivate benzene rings?

texts: This is probably a common question because it involves TNT precursors, but if an $\ce{NO2}$ group deactivates benzene rings toward electrophilic aromatic substitution reactions, then how can toluene be tri-nitrated? I understand that the methyl group will donate electron density and activate the ring toward the first substitution, but after two nitrations I'm sure the nitro groups slow the third substitution. So what's the trick? How does toluene get three nitro groups?


texts: How can you estimate how much of a substance will dissolve in a given lipid?

texts: How can you estimate how much of a substance with a known partition coefficient and other physical/chemical data regarding the substance will dissolve in a given lipid? In particular I would like to know the answer to this question in the context of the blood-brain barrier (BBB).


texts: Adsorbable Organic Halides (AOXs) in bleach residue

texts:
I have a question regarding using household bleach, and wonder if someone knowledgeable can help, please?
I have used household bleach (sodium hypochlorite, sodium hydroxide, coco alkyldimethyl, amines, N-oxides, non-ionic surfactants) to bleach mold that had formed in my bathroom on the tiles. I probably used too much, undiluted, and the result has been large patches of salt residue which have formed on the bath tub.  I use the bath tub to shower, and to be honest, I hadn't removed some of the residue for a while, but when I have tried, it is quite stubborn.
I believe the breakdown of bleach results in harmless compounds, but I have read that a small percentage consists of adsorbable organic halides. My concern is, are these harmful, if they get in shower/bath water? Do they stick to the salt residue, or are they washed away quickly? The salt residue does not come off easily when rinsing, so are there no longer AOXs present, or are they potentially leaching into the water from the residue over time? I sometimes have cuts/dry skin so wonder about the possibility of absorption, and any risk this may pose.
Many thanks.


texts: I'm looking to lower the pH of a urine solution from 12 to 7. I'm planning to do it in 2 ways. First is to use a strong acid such as HCl. Secondly, using vinegar, a weak acid. However, I am having troubles calculating the pH in both methods as it other chemicals in urine such as ammonia may react to it. Since it's a theoretical experiment, can I just assume that the acid would only react to water? But how will I do it either way?


texts: Do antimicrobial abilities of copper boilers decrease over time?

texts: As copper boilers age and develop oxide buildup, does this lessen the copper's antimicrobial abilities in killing bacteria? I was thinking since that coating would be on the copper, there would be less contact between it and the water, thus killing less bacteria.


texts: Determination of products in reactions involving carbocation rearrangement?

texts:
How do you determine the migratory "aptitude" of various groups during carbocation rearrangements? Is there a experimentally determined order?
 For example, what will be the product in case of the following pinacol-pinacolone type rearrangement:
$$\ce{(cyclo-pentyl)CH3C(OH)-C(OH)(CH3)(cyclo-pentyl) ->products}$$

Will the methyl group be transferred or the cyclopentyl moiety? The same question arises if the cyclopentyl is replaced with phenyl group? In general, which shifts, methyl, hydrogen, phenyl or any other group, will take place? Or equivalently, what determines which group has a greater tendency to undergo shifts during carbocation rearrangements?


texts: acrylonitrile butadiene styrene and hot water

texts:
ABS melting point is slightly above 100 celsius so if you boil it. It can become a bit moldable right? But at 80 celsius it is stable. So this can be used as sediment filter housing from water heater which doesnt go above 80 celsius.
But in the sediment filter industry. They use glass reinforced carbon constructed housing for the container whose maximum temperature at 80 celsius too.
If ABS is stable at 80 celsius, why do you need for the glass reinforced carbon constructed housing as hot temperature sediment container? Somehow is it possible ABS is metastable at 80 or 70 celsius?


texts: How to determine the specific heat of methanol from calorimeter data?

texts:
A $\pu{25.95 g}$ sample of methanol at $\pu{35.6 ^\circ C}$ is added to a $\pu{38.65 g}$ sample of ethanol at $\pu{24.7 ^\circ C}$ in a constant pressure calorimeter. If the final temperature of the combined liquids is $\pu{28.5 ^\circ C}$ and heat capacity of the calorimeter is $\pu{19.3 J/^\circ C}$ determine the specific heat of methanol. The heat capacity of ethanol is $\pu{2.46 J/(g * ^\circ C)}$.

\begin{align}
  q_\mathrm{methanol} &= -q_\mathrm{ethanol}\\
  msT &= -msT\\
  \pu{25.95 g} \cdot  (\pu{28.5 ^\circ C} - \pu{35.6 ^\circ C}) \cdot  s
    &= -\pu{38.65 g} \cdot  (\pu{28.5 ^\circ C} - \pu{24.7 ^\circ C})
       \cdot  \pu{2.46 J/(g* ^\circ C)}\\
\therefore s &= \pu{1.96 J/(g * ^\circ C)}
\end{align}
The correct answer, however, is $\pu{2.36 J/(g * ^\circ C)}$.
I think that there is a mistake in my solution, because the heat capacity of the calorimeter is given, and I didn't use it.
Could anyone explain where I have been wrong?


texts: Chemical compounds responsible for the colors in flowers?

texts:
I know that anthocyanins are a class of compounds responsible for the purple colors found in flower petals.

  Anthocyanins (also anthocyans; from Greek: ἀνθός (anthos) = flower + κυανός (kyanos) = blue) are water-soluble vacuolar pigments that may appear red, purple, or blue depending on the pH. (same reference as above)

The anthocyanins, when extracted from flower petals with water, can be used as acid/base indicators, producing red colors in acid and blue in neutral solutions (in basic solutions they turn green, yellow, and then become colorless). When I've done the extractions, some red petals produce a red color in acid and maintain the red color at higher pH than purple flowers (see plate below), but some red flowers produce colors that seem to follow the normal progression.

Row 2 from the top was a purple flower, row 3 a red flower and row 4 also a red flower. (pH values start at 2 on the left and increase by 1 pH unit as you move right by adding the water extracts to buffer samples in the wells.)

So, are there other classes of compounds responsible for the red and yellow colors found in flowers? Can the red colors that give a "normal" anthocyanin pH response arise from pigments held in an acidic environment in the plant?   (That may be a biology question, but I'm interested in the chemistry side of where the color comes from.)


texts: relaxed dihedral PES scan: symmetry of the system not reflected

texts:
Using G16 and performing a relaxed PES scan on a dihedral angle, I performed 72 steps where one phenyl group of a symmetric terphenyl is rotated about the C(aryl)-C(phenyl) bond by 5° in every step. I'm using the BP86 functional with the 6-31G basis set. I observe that -180° to 0° will not be the same as 0° to +180°.

In my opinion, rotation of a phenyl group (with a mirror plane which would be perpendicular to the C6 axis in benzene) should result in energies at x° being the exact same as for x°+180°. In the first graphics below, you can see one whole rotation (black dots, scan points 1 to 73) and the scan points 38 to 73 shifted by +180° (red dots). You can see that there is a shift on the abscissa, meaning that the first 180° of rotation about the aryl-phenyl bond are not the same as the second 180°. Interestingly, when rotating more than 360° (3-5 times 360°), the dots will be at the exact same position as 360° earlier - so x° and x°+360° will be the same in every case, while x° and x°+180° are not. Don't think that this is an issue related to convergence?

edit: @TAR86 suggested to have a look at the nuclear repulsion energies to check whether this is an issue related to the geometries produced. The respective image is added below.

edit2: @Martin - マーチン♦ requested an G16 input file to reproduce the problem. I've added the respective file below.

%chk=job.chk
%mem=8gb
%NProcShared=16
#p opt=(modredundant) BP86/6-31G geom=(gic)

dihedral pes scan

0 1
6        5.226229852      2.461878014      0.364189364
6        6.517648681      1.947188819      0.628146249
1        7.127277746      2.400165503      1.416350388
6        7.024836811      0.874189127     -0.119447737
6        6.252002950      0.287970075     -1.134646502
1        6.649922190     -0.550963401     -1.716497030
6        4.963870485      0.783187734     -1.399800460
6        4.455606763      1.856498426     -0.656174766
1        3.460115638      2.254235558     -0.885310716
1        8.028604788      0.493012088      0.098455632
1        4.355515157      0.336549951     -2.194552005
6        5.437910365      4.695855989      1.613350721
6        4.667674122      3.560511364      1.202847170
6        3.339228627      3.414455715      1.655493257
1        2.762287260      2.537249136      1.343693331
6        2.778852196      4.366478962      2.509604334
1        1.728615174      4.291477665      2.812827707
6        3.587531970      5.372572404      3.043834082
1        3.154198853      6.017546127      3.811431515
6        4.962035000      5.490387000      2.719069000
6        5.793408000      6.483337000      3.479780000
6        7.155794401      6.716767843      3.150348234
1        7.690505145      6.040409950      2.477397785
6        7.891233889      7.760301086      3.724625384
6        7.281499938      8.654025495      4.618188277
1        7.854319283      9.475639651      5.062586031
6        5.919284422      8.491819231      4.906055341
6        5.183645944      7.448680994      4.325851576
1        4.106339318      7.414359241      4.527417701
1        8.948095638      7.878562451      3.459649110
1        5.404779334      9.198550838      5.566858766
15       6.836613173      5.254444911      0.492426546
6        6.402468333      4.749060218     -1.232735776
1        5.331395678      4.884562656     -1.457090749
1        6.692781337      3.708789948     -1.428936030
1        6.992612351      5.408972053     -1.892849893
6        6.570730658      7.079097928      0.321764243
1        5.553588175      7.291894513     -0.050476225
1        7.307098080      7.438494888     -0.417840357
1        6.732539811      7.615443003      1.266231462
8        8.252395391      4.848887467      0.884390392

interplanar=Dihedral(22,21,20,12)
interplanar(NSteps=72, StepSize=5.00000)


texts: Adding acid to hard water to prevent limescale deposition

texts:
Acid is commonly used to remove deposited limescale. If I wanted to prevent build-up of limescale in appliances, would it make sense to add acid to the water in the first place if that doesn't harm the appliance?
As far as I understand, limescale gets produced when calcium bicarbonate turns into calcium carbonate when some of the dissolved $\ce{CO2}$ goes airborne, making the water less acidic and thereby shifting the equilibrium from bicarbonate to the less soluble carbonate.
If I now add acetic acid, according to my understanding that should keep the equilibrium on the bicarbonate side. What acid concentration do I need for different water hardnesses if this trick actually works?
I'm thinking of using it in my cleaning robot. The small valves are getting clogged very quickly. A percent of vinegar in the water shouldn't harm the tank. But prevent the clog ups.


texts: If for reversible process, ΔS= 0 for universe (system+surroundings), why would there be non-zero change in gibbs energy?

texts:
As Second Law says, the entropy must increase for universe

$$\Delta S_\textrm{universe}\ge 0$$

Now, we know, $$\Delta G= -T\Delta S_\textrm{universe}\le 0^\dagger$$

For reversible process, $$\Delta S_\textrm{reversible, universe} = 0$$

That would mean $$\Delta G_\textrm{reversible}= 0$$

But does it happen so?

Peter Atkins, in his book writes:

  At constant temperature and pressure, for a reversible process: $\mathrm dG = \mathrm dw'_\rm{rev}\;.$

Now, isn't it contradicting that $\mathrm dG\ne 0$ for reversible process? If $\Delta G= -T\Delta S_\textrm{universe}$, then wouldn't $\mathrm dG= 0$ for $\mathrm dS_\textrm{universe}= 0$ during reversible process?

\begin{align}^\dagger \Delta S_\textrm{universe}&=\Delta S_\textrm{system}+ \Delta S_\textrm{surroundings} \\ &= \Delta S_\text{system}+ \frac{-\Delta H_\text{system}}{T} \\ \implies   -T\Delta S_\text{universe} &= \Delta H_\text{system} - T\Delta S_\text{system} \\&=\Delta G  \end{align}


texts: What causes the deshielding in carbon - carbon bonds?

texts:
I thought of this question while reading through a chapter on Carbon 13 NMR. It's easy to see that in a bond with two different atoms, such as in a bond involving $ \mathrm C$ and $\mathrm O$, that the difference in electronegativity causes a deshielding effect. It's also easy to imagine that the deshielding effect is proportional to the number of electrons involved in the bond. These two facts are consistent with the Carbon 13 NMR spectra for single and double bonds between oxygen and carbon atoms. A single bond between carbon and oxygen generally causes a chemical shift of $ 50 - 100 $ p.p.m. A double bond between these two atoms is close to the $150 - 200$ p.p.m range.

However, there is a discrepancy with this approach when we look at carbon carbon bonds. Firstly, there is no difference in electronegativity between these two atoms, so we would not expect a significant chemical shift, however there is a significant observed chemical shift in the NMR spectra. Let's ignore this for a moment. We have for atoms involved in carbon carbon single bonds a chemical shift in the $0 - 50$ p.p.m. range. In carbon carbon double bonds, a shift of $100 - 150$ p.p.m. is observed. However, we have for carbon carbon triple bonds, shifts of $50 - 100$ p.p.m. observed.

Clearly, electronegativity is not the only factor affecting deshielding. Also, we cannot rely on the assumption that the chemical shift is directly proportional to the amount of bonds between the atoms. So, my question is this: What causes the deshielding between atoms involved in bonding? How can we explain the observed spectra theoretically? Our current theory is clearly inadequate.