texts:
It is common knowledge that tin melts at $449.5~\rm^{\circ}F$ and Lead at $621.5\rm~^\circ F$, and that when these are melted together you simply have an alloy.

What happens, or what product occurs, if you take pure lead to red heat ($1,400$ – $1,500~\rm^\circ F$) in a muffle furnace and cast in pure tin?

The mixture "Blooms" with somewhat small cubic crystals that, when scooped off the top into a receptacle, appears as a sulfur colored scoria that I was not able to re-melt into metal at even $2300\rm~^\circ F$.

I have a photo if I can figure out how to post it.


texts: Copper (II) oxide during CuSO4 electrolysis

texts: I was performing copper (II) sulfate electrolysis (graphite electrodes; 10V; 0,01A) today and I observed black precipitate falling from around cathode. I suppose it's copper(II) oxide. I couldn't find information about this reaction. Have you ever read somewhere about this reaction or do you know it?


texts: What is chemistry considered the study of?

texts:
I am asking this because I have a review question in my physics class which gives me a multiple-choice question.  I have heard and seen elsewhere on the internet (such as wikipedia) that chemistry is the study of reactions and the properties of matter.  That is usually a satisfactory answer, but for whatever reason this question makes me choose between reactions, properties, and matter.  Now I find that the general definition I accepted contains basically all of those, as far as I can tell.  While I don't necessarily need the answer, my curiosity has been aroused and I want to know why the question makes me choose between those answers.

The question is, what is the very basic idea behind chemistry?  Would it be classified as the study of reactions, properties, or matter (and you can only select one)?


texts: Why is it that from a cup of hot coffee, only the water condensates on the inside of the lid? Why aren't there any coffee particles? Does it only have to do with density or is it something else involved?


texts: Ice under very high pressure phase transitions

texts: If you put a piece of ice into a very high pressure chamber and increase the pressure, I can understand how the ice turns to a water state.  But what happens after that?  Does the pressure push the water together into a crystal structure, once again, to make ice, or does the water just stay in its liquid phase?


texts: What are examples of group 14 elements forming dπ - pπ bonding?

texts:
While studying the Group 14 elements, I came across the anomalous behaviour of carbon. In that there was a point:

  Carbon forms only p$\pi$-p$\pi$ type bonding while other elements in the group form p$\pi$-p$\pi$, as well as d$\pi$-p$\pi$ type bonding.

I am searching for molecules in which  group 14 elements form d$\pi$-p$\pi$ bonds.


texts: What determines the electronegativity of an element?

texts: Is it possible to work out without post-Bohrian mathematics?


texts: Which compounds react positively in the aniline dye test?

texts: I read that to test for the presence of phenol groups in an organic compound the aniline dye test can be performed. If the solution has phenol present it gives a red or orange precipitate to confirm the presence, however as a side note it was mentioned that this test is applicable for the detection of small quantities of phenols, which have a free para position. Why is it so?


texts: Choosing hyperconjugation when resonance doesn't give a reason for stability

texts:
Which of the following structures would be least stable?

I initially approached it like this:
As both are allylic carbocations, and that both are in fact resonating structures of the same molecule, so resonance can't be used to judge them. So I went for hyperconjugation. The first molecule has four alpha hydrogens and the second has only one alpha hydrogen.
Since there is more hyperconjugation in the first, it should be more stable. But I also have an intuition that there might be something more that we should have a look upon but I'm not able to figure it out. Should we always choose hyperconjugation as our second option when we can't make judgements using resonance?


texts: What is the SNi mechanism of the reaction of moist silver oxide with a halide?

texts:
I was told by my teacher that the following reaction proceeds through SNi:

Moist $\ce{Ag2O}$ is basically $\ce{AgOH}$, what role does it play in this reaction's mechanism? I think this is what happens, but I am not sure:

$\ce{AgOH}$ attacks $\ce{Cl-}$ and during this process the $\ce{Ag-O}$ bond breaks and an intimate ion pair is formed between the carbocation and $\ce{Cl-}$.
Since a partial bond still exists between $\ce{Ag}$ and $\ce{O}$, $\ce{O}$ is forced to attack from the same side from where $\ce{Cl-}$ left and the reaction proceeds to completion without Walden inversion.

Is my reasoning correct? Or is there a different mechanism?


texts: Do any efforts to construct artificial biochemistries exist and what compounds are they based on?

texts:
I'm a researcher interested in the fields of origins of Life, astrobiology and theoretical biology in general but I must admit I think my knowledge of chemistry outside biochemistry is a little bit limited. I'm well aware of the efforts to construct nucleic acid analogues and to construct expanded genetic codes with amino acids other than those found in the proteins in Nature but I wonder how far can we go as to construct a biochemistry which has nothing to do with our own? Is there anyone who had seriously investigated the question what kinds of compounds can be used to build a chemistry capable of providing the grounds for evolution into something we could classify as a lifeform? What classes of chemical compounds other than nucleic acids, proteins and lipids could develop into a real biochemistry? Are there any chemists who had seriously undertaken an effort to make such an investigation about classes of chemical compounds other than those known in biochemistry and if there are such efforts what molecules are they based on?

P.S. This is a question directed toward theoretical chemistry as much as it is a reference request, so I'm asking anyone who knows something about the matter to put their knowledge in the answer section whether it comes from fields related to biochemistry or not. From what I had researched so far there are some efforts to construct a biochemistry mimicking our own but my question isn't about biomimetics. I wonder could there be a biochemistry radically different from our own and how could I "screen" (or is that even possible) for classes of molecular species which could build it? I'm talking about a biochemistry not based on proteins or nucleic acids or even not having any type of "information" (whatever may stand behind such a word) at all. I'm asking this in the Chemistry SE because my interests are to learn could I select classes of molecular species which could do the job even in theory out of what we presently know about the possible diversity of chemical compounds or is our knowledge of all possible chemical compounds that could generate complex structures still too limited to shed any light on the questions of Life? Are we pass the point where we know enough about chemistry to theorize what molecules we could use to "build" a living organism or is there still a long way to go before we could say we know enough about all the possible molecules that can generate complexity? I want to know the answer to this question from a point of view of chemistry, not biology. I had enough experience with biologists and I could say the ones I met are too narrowed by biochemistry as we know it which I think is far from every possible biochemistry. Can you understand my background? Can you make any suggestions which fields of chemistry I should look into to find the answer to my query?


texts: What is the chemistry behind amalgamation?

texts:
Mercury can form amalgams with metals, such as gold, however how exactly does the "reaction" if you can call it that take place?

My understanding of metal bonds is that the atoms of a metal are surrounded by a "sea" of electrons, however I don't understand how mercury can "penetrate" metals and weaken their structure or "dissolve" them.

How does it do this? Also does this apply to Gallium?


texts: How to simplify these system of equilibrium equations

texts:
What is the pH when $0.025$ mol $\ce{NiCl2}$ is added to $\pu{1.00 L}$ of a $\pu{0.100 M}$ solution of $\ce{HCN}$, if the formation constant for $\ce{Ni(CN)4^2-}$ is $K_f=\pu{1.0e22}$, and the $K_a$ for $\ce{HCN}$ is $\pu{4.9e-10}$?

My approach is as follows:

1) $\ce{\frac{[H+][CN-]}{[HCN]}=4.9*10^{-10}}$

2) $\ce{\frac{[Ni(CN)4^{2-}]}{[Ni^2+][CN-]^4}}=1.0*10^{22}$

3) $\ce{[H+][OH-]}=10^{-14}$

4) $\ce{0.025=[Ni^{2+}] + [Ni(CN)4^{2-}]}$       .............  (mass balance for $\ce{Ni^{2+}}$)

5) $\ce{[CN-] + 0.05 + [OH-] + 2*[Ni(CN)4^{2-}] = 2*[Ni^{2+}] + [H+]}$ ........... (charge balance)

6) $\ce{0.1 = [CN-] + [HCN] + 4*[Ni(CN)4^{2-}]}$ ............. (mass balance for $\ce{CN^{-}}$)

Since the equilibrium constant for the formation of the complex ion is very large, I assume that $\ce{[Ni(CN)4^{2-}] >> [Ni^{2+}]}$, so $\ce{[Ni(CN)4^{2-}] = 0.025 M}$, from the mass balance for $\ce{Ni^{2+}}$.

However, I am not sure what is the next step and what other assumption to make.


texts: A solution is cloudy at lower concentration and becomes clear at higher concentration. Why?

texts:
This might be just an "everyday life science" question. I am a university professor but not in Chemistry so please educate me. Today I was adding some floor cleaner formula to water as instructed by the label. In the beginning, the solution became cloudy. However, as I added more formula, the solution became clear. I am curious why this can be and whether there is a name for such a phenomenon in Chemistry.
More details and pictures:
Just a little bit of formula added to the water; the solution was cloudy:

Then I added more formula; the solution becomes clear:

The cleaner is called "HOOVER FloorMate Grout & Tile Plus".
Out of curiosity, I checked its data sheet which states that it is a :

Blend of proprietary non-hazardous surfactants and polymers.


texts: How to calculate Madelung's constant for NaCl?

texts:
Madelung's constant for $\ce{NaCl}$ is $1.748$.
What I tried to so is sum up all the individual interactions into $1$ component where the $X$s are the nucleus and the electron if it was a $2$ atom system. Is this the correct way to go about it? Thanks!


texts: Flavonoid Xanthine Oxydase Inhibitors vs Hydroxychloroquine

texts:
Regarding COVID-19 and hydroxychloroquine (HCQ), HCQ is known to increase pH in lysosomes by 1-2 orders of magnitude, and also results in lethal intracellular heme overload in parasites responsible for hemolytic diseases.  Question is, if circulating levels of xanthine oxidase (XO) are also known to be increased in hemolytic diseases, if one considers the natural flavonoids Kaempferol, quercetin, or luteolin, which are known xanthine oxidase (XO) inhibitors, antivirals, and anti-oxidants, what would be different about pharmacology of natural XO inhibitors and HCQ?
Is HCQ an XO inhibitor because it results in heme overload in parasites?  What about anti-oxidant properties of HCQ in terms of radical scavenging?  There is no information supporting the notion that HCQ is an antiviral.
Sticking with hemolytic diseases, for which the goal is overload of intracellular heme in parasites, what would happen if a human took high levels of an XO inhibitor that wasn't HCQ during malaria?
XO inhibitors usually result in an overall decrease in uric acid, essentially rendering them as a natural supplement for gout -- i.e., replacement to allopurinol, which has horrendous side effects.


texts: What happens when I use cyclohexanol to prepare cyclohexene?

texts:
I've done a student experiment using cyclohexanol to prepare cyclohexene.

We mix $10.5~\mathrm{g}$ cyclohexanol and $5~\mathrm{mL}$ $85\%$ $\ce{H3PO4}$ in a $50~\mathrm{mL}$ flask, then distill while heating.

I want to know during this process what kind of side reaction happens because I notice there is something light yellow in the flask. After reaction, the liquid remaining in the flask is red and upon it there is something dark green and muddy.

I have a guess that there is some phenol in the cyclohexanol (since cyclohexanol may be prepared from phenol), and that during reaction the phenol oxidized, producing 1,2-benzoquinone (which is red) and 1,4-benzoquinone (which is yellow). Is this idea reasonable? If it is, why does the red color appear later?

And about the dark green thing: can it be produced by some kind of carbonized organic matter? I have been told that if the $\ce{H3PO4}$ and cyclohexanol were not well mixed, there would be some cyclohexanol carbonization.

(Can I ask one more question?) We are required to compare the chemical properties of cyclohexene and cyclohexane. So we reacted them with $\ce{Br2}/\ce{CCl4}$ respectively, under light or covered by aluminium foil. Should it be different when cyclohexene reacts under light or covered by aluminium foil? I notice the result is slightly different; the reactions in the light become a little opaque.


texts: What is the difference between the esterification and transesterification?

texts: What is the difference between an esterification and a transesterification. Esterification objective is the formation of an ester by reacting an alcohol and a carboxylic acid. I am more concerned transesterification or reference to a journal article.


texts: What does the order of a class mean in a character table?

texts:
I am not from a chemistry background. I am trying to see how the symmetry operations affect the stiffness tensor which led me in the path of understanding character tables. I am looking at the character table for C6v group and I cannot understand what the factor 2 for C6(z) means. Is it representative of the fact that I can rotate in clockwise and anticlockwise direction?
Please let me know if you need any further information.


texts: The effect of hyperconjugation on the stability of alkenes with MO theory

texts:
Hyperconjugation stabilizes carbocations and that makes sense because electrons are given to the empty p orbital.

But how does it stabilize alkenes? Can molecular orbital theory be used to explain it?


texts: Is it correct to write Na2B2O4 as 2NaBO2?

texts:
My teacher wrote the reaction for heating of borax like this:
$$\ce{Na2B4(OH)4 .8H2O->Na2B4O7 + 10H2O}$$
$$\ce{Na2B4O7->B2O3  +Na2B2O4}$$
And told us that $\ce{Na2B2O4}$ can be written as $\ce{2NaBO2}$,is this correct?
If yes then why?


texts: How to calculate RESP charges in a system with addition of user-defined extra-point charge in AMBER?

texts:
I would like to add in extra point of charge in my molecule system (EP) and calculate the resulting RESP charges. Parameters for the EP has been defined in a separate frcmod file. However, I am not sure on how to incorporate the EP into the RESP calculation. I have generated the .esp file beforehand from a QM calculation (Gaussian 09).
Any help would be greatly appreciated.
Thanks!
FYI, I am using AMBER16.
P.S. Somehow cannot post in the AMBER mailing list, hence asking here.


texts: Why we don't we save water by boiling the contaminated water to get the pure steam?

texts:
I see lot of drinkable water wasted in household and industrial activities, water usually gets contaminated with detergents(and other household materials),chemical effluents released from factories .
Why we don't just boil off the contaminated water to get the steam and again condense it to get pure water safe for drinking?

I get this idea from the fact that when we boil out salted water we get all the salt as precipitate thus distilling the water.I don't know much about distillation but I think this process can be economically feasable when done on a large scale.

By this method of treatment,I am considering countries that cannot afford water treatment plants on a large scale and with problem of water scarcity,as this would be quick way to get drinkable water.


texts: Thermodynamics of chemical reactions "at constant pressure"

texts:
Chemical reactions occur at constant temperature and pressure.

Consider a gaseous, equilibrium reaction: $\ce{2NO2(g) <=> N2O4(g)}$. Most questions/textbooks formulate such questions by stating: The reaction happens at ($T$) temperature and ($P$) pressure.
This gives the impression that the surrounding Temperature and pressure are constant.

The first confusion that then arises is: For thermodynamic quantities such as enthalpy that involve pressure, which pressure should we use, internal or external?

After reading some chem.SE answers, it seems to me that $P_{sys}=P_{surr}$ is a basic assumption. However this doesn't seem to go well with the example I mentioned: Since the pressure of the system will be given by $(n_1)RT/V + (n_2)RT/v$, where $n_1$ and $n_2$ are the moles of $\ce{NO2}$ and $\ce{N2O4}$. Clearly, as the reaction progresses, ($n_1+n_2$) changes, and thus,the pressure of the system changes. If the surrounding pressure is kept constant, this beaks the "assumption": $P_{sys}=P_{surr}$.
Am I missing something?


texts:
What exactly is a solubility product, and what is its use?

I've come across this term while reading, and don't have access to anyone who can help me understand this concept.


texts: Why does a neutral atom of beryllium not have any electrons in a p orbital?

texts:
Here's what I understand about quantum number and orbitals, please correct me if anything is wrong:

Electrons enter into these different types of orbitals because they have a higher/lower amount of energy, and we know that the number of electrons varies from element to element along with the energy levels of those electrons in a pretty linear way, conveniently allowing us to organize them into blocks on the periodic table where their highest energy level electron is in one of the many types of orbitals (spdf). I know the energy shell occupied by an electron (the principle quantum number) corresponds with the angular momentum quantum number which determines the magnetic quantum number, which determines the type of orbital an electron is in. I know that all of that is because the electrons in higher energy shells/levels have more energy are thus more likely to be in an orbital such as d or f as opposed to an s or p orbital, for example.

Note that I don't know why the orbitals exist in the exact shapes they do (although I imagine it has something to do with the electrons speeding up or slowing down at certain points making it more likely for us to discover it in a certain spot), or what the threshold is for the amount of energy required to make an electron move into the next type of orbital (d to f, for example).

But, I have one question: why does a neutral beryllium atom with 4 electrons in 2 energy shells/levels not have any electrons in a p orbital?

My reasoning is as follows:

If $n = 2$ where $n$ is the energy shell occupied by beryllium's fourth electron, then $l = 0,1$ and $m_l = \text{either }0 \text{ or }-1,0,1$. If $m_l = -1,0,1$. Then, why isn't this fourth electron in a p orbital?


texts: Why can't we rotate a carbon while checking for chirality?

texts: If I were to rotate the front carbon clockwise by $60^\circ$, it would become achiral. But my text book says that it's chiral. Is it that rotating an individual atom about a sigma bond changes its conformation is that why we can't rotate it?


texts:
Several articles affirm that NO can enhance the glutamate release from the presynaptic site; moreover, glutamate has been recognized as a major brain neurotransmitter and is considered to mediate excitatory transmission at most synapses of the central nervous system.

First point is the following: is the chemical reaction reported here the equation that describes how NO is produced? If yes, is there a way to model this reaction in such a way it can be simulated by using MATLAB? And finally, do you know what are the kinetic properties of this reaction?


texts: How to figure out the most stable conformation of the diastereomer?

texts:
Question 1: Which of the following Newman projections represent the most stable confirmation of the diastereomer of the molecule given below?

I guess my main question is looking only at the Newman projection, how does one determine the stereochemistry?
In the molecule to the right, I get for the first carbon, ($\ce{Et, H, Me}$) R (I flipped it after moving the $\ce{H}$ back) and for $\ce{C}$2 ($\ce{Et, Br, Me}$) I get S.

Question 2: Which of the following Newman projections represents a confirmation of the enantiomer of the molecule given below?

In the same vein, for the second question, I thought I should flip all the stereocenters to get the enantiomer since it is a mirror image. But I am not getting the answers the professor provided to us.


texts: Why are square planar coordination compounds with four different ligands optically inactive?

texts: Why do square planar coordination compounds of type $\ce{[Mabcd]}$ not show optical activity, although they contain 4 different ligands (i.e. chiral central metal atom)?


texts: Why does dilithium have a longer bond length than dihydrogen?

texts:
I've tried MO theory however they both have a bond order of 1. Which means we can not relate the bond order to the bond length.

My thinking -
I think that the h2 bond length is shorter due to only the 1s electrons participating in the bonding. Where as in dilithum we have the 2s electrons participating only. This makes me think that due to Li having a filled 1s subshell, as the 2 atoms approach the 2s electrons are repelled by the other atoms 1s electrons. Once bonded the filled inner core of 1s electrons will repel the other atoms 2s electrons keeping the atoms at a further distance.
I may be wrong any help would be great!


texts: Rutherford's alpha particle scattering experiment for sheets made of different metals

texts: The correct order of increasing number of alpha particles passing undeflected through the foils of Au, Ag, Cu and Al of 1000 atoms thickness each in an alpha scattering experiment of Rutherford would be?


texts: Why the tendency of ClO3 to form dimer is high?

texts:
I read that tendency of $\ce{ClO2}$ to form dimer is less and that of $\ce{ClO3}$ to form dimer is more.

I can understand the reason for the former because the unpaired electron is more delocalized in this case. So, if an electron is localized, i.e. it is at rest then the tendency of the molecule to form dimer will be high. Whereas if the electrons are delocalized, i.e. it is moving, then the tendency of the molecule to form dimer will be less.

I don't understand why the tendency to form dimer in the case of $\ce{ClO3}$ is high. There are vacant $\mathrm{d}$ orbitals with chlorine. Then why is that?


texts: How to determine if a reaction proceeds via SN1, SN2, E1 or E2 mechanism?

texts:
Give the main product and reaction type: SN1, SN2, E1 ,  E2.

As the 1-bromohexane is primary and the nucleophile a strong unhindered base, the reaction should be a SN2 reaction. However, the solvent $\ce{EtOH}$ is a polar protic solvent which favours SN1/E1 reactions. In addition, the temperature of the reaction is quite high and high temperatures favour the formation of elimination reactions, thus the reaction should be E1.
But an E1 doesn't require a strong base, or else an E2 reaction would take place at the beginning. So does that make this reaction an E2 reaction? Am I thinking correctly on how to consider all the different parts of the reaction?


texts: Total number of “hyperconjugable” hydrogens in 1-(3-ethyl-4-methylphenyl)-2-methylprop-1-ylium

texts:
How do I find the total number of “hyperconjugable” structures for 1-(3-ethyl-4-methylphenyl)-2-methylprop-1-ylium?

I read some sources stating that the total number of “hyperconjugable” structures is equal to the total number of α-hydrogen atoms. But which carbon is taken as the alpha carbon in a compound having no functional groups, just carbons?


texts: Is it possible to normalize the concentration equilibrium constant between different reactions for comparison?

texts:
A follow up question from this answer:

  Compare:
  $\ce{A(aq) +B(aq)->AB(aq)}$
  $\ce{2A(aq) +B(aq)->A2B(aq)}$

  We have two similar reactions but the equilibrium constants can vary by a huge amount due to the presence of a second A atom in the reactants.  Similarly, with a constant solid/liquid concentration (activity = 1) the equilibrium constant effectively ignores that product or reactant.

Is there a way to "normalize" the $K_c$ of reactions like that shown above, such that a fair comparison can be made, regarding whether one reaction is more product favoured than the other?


texts: Can nitrous dioxide develop when copper and dilute nitric acid react?

texts:
When doing an experiment in the laboratory with copper, dilute nitric acid and finally hydrochloric acid, the first reaction between copper and dilute nitric acid should end in nitric monoxide, cupric nitrate and water:
$$\ce{3 Cu(s) + 8 HNO3(aq) -> 3 Cu(NO3)2(aq) + 4 NO(g) + 2 H2O(l)},\tag{R1}$$
but somehow nitric dioxide, a reddish-brownish gas appears with a poignant smell, develops from this type of reaction:
$$\ce{Cu(s) + 4 HNO3(aq) -> Cu(NO3)2(aq) + 2 NO2(g) + 2 H2O(l)}.\tag{R2}$$
There was 5 mL of nitric acid and as we added nitric acid we quickly covered it with a watch glass. Then we put it in a sand bath instead of heating it normally with a Bunsen burner. Unfortunately, I cannot as it was one of the experiments that we just wanted to know what was going to happen and write down our observations and conclusion.


texts:
I have a question regarding the delocalised electron in graphite. There has been conflicting information between books.

Some books said the delocalised electron in graphite exists $\bf{between}$ layers.
Some said the delocalised electron in graphite exists $\bf{within}$ the hexagonal layer.

I support the second statement, because carbon has electronic configuration of 1s2 2s2 2p2. Graphite has sp2, therefore leaves 1 p orbital. And the giant pi bond should be extended over the layer, instead of between.

I am not sure my evidence is sound.
Any advice would be greatly appreciated. Thank you in advance.


texts: Is there a way to fine tune a laser to excite the electrons of a particular molecular bond into dissociating?

texts: I don't know if this makes any sense, but I came up with this in my head: if each molecular bond in any molecule had a specific *signature wavelength of dissociation", this would be the exact wavelength of the laser beam necessary to excite the electrons involved in that one particular bond and no other bonds in the molecule into dissociating homolytically. Is this theoretically sound in any way?


texts:
When oxygen is adsorbed on iron metallic surface, does it create $\ce{Fe-O}$ bonds like the one in iron oxide? Can it be considered as a monolayer of iron oxide on the surface?

If not, how is the atomic bond of adsorbed oxygen and iron? How much is it strong? and what is its difference with normal chemical bond in iron oxide molecule?


texts: How to determine amount of CO₂ in soda water

texts:
I've got a problem in determining the amount of $\ce{CO2}$ in soda water. Basically, I have boiled some purified water to remove the dissolved gas.  By using a SodaStream machine, I made carbonated water.

After that, I have tried to determine the amount of carbon dioxide through titration with phenolphthalein and also $c(\ce{NaOH})=0.1~\mathrm{mol/L}$ sodium hydroxide.

The problem is I am not sure if this is the correct method to determine the amount of dissolved $\ce{CO2}$ in water.


texts: Why does Be have a higher ionization energy than B? I know that it has a filled 2s orbital, but what's the more accurate explanation?


texts: Is hydrogen good to be used in cars? How much of traveling can a car do with medium sized balloon filled with hydrogen? Is it worth it?


texts: Conformers with extremely high energy barriers?

texts: What are some conformers with very high energy barriers? When we think of e.g. the butane conformers, at room temperature, the conformational change plays almost no role. I was wondering how molecules look like that are almost exclusively in one energy valley or the other (so something like 50-50, not 99-1) and hence might even have different physical properties, depending on the conformation it is in.


texts: Deposition of saturated solution and affect of evaporated water

texts:
20g of water is evaporated from 200g of saturated solution of KNO3(aq) at 60°C by heating and the solution was cooled to 20°C. How many grams of KNO3 were deposited? The solubility of KNO3 in 100g of water is 32 at 20°C and 109 at 60°C.
I have a doubt on "20g water is evaporated from 200g KNO3" statement. I'm assuming that as 20g evaporated that means the initial saturated solution has mass of 220g. This is at 60°C. I also assume the solubility in g/L.
Now, at 60°C the max amount of solution that can dissolve is 109. Thus, if we get 220g this leaves $220-109=111g$ of solvent that is not dissolved.
Then, if the saturated solution is cooled down to 20°C, the solubility will decrease to 32g/L while the amount of precipitation we have remains the same. This leaves $111-32=79 grams$ of KNO3 precipitated. Therefore, the final amount of KNO3 deposited is 79g.
Did I treat the amount of water evaporated in a correct way? I'm not sure whether the water is affecting the total concentration or 'overall' volume of the saturated solution.


texts: Is the valency of carbon satisfied in graphite?

texts: Graphite has hexagonal parallel planes. In a hexagonal structure the carbon atom has three bonds. Since the valancy of carbon is 4 is the valency satisfied in graphite?


texts:
Molar conductivity increases with decrease in concentration. This is because the total volume, $V$, of solution containing one mole of electrolyte also increases. It has been found that decrease in $\kappa$ on dilution of a solution is more than compensated by increase in its volume. Physically, it means that at a given concentration, $\Lambda_m$ can be defined as the conductance of the electrolytic solution kept between the electrodes of a conductivity cell at unit distance but having area of cross section large enough to accommodate sufficient volume of solution that contains one mole of the electrolyte. When concentration
  approaches zero, the molar conductivity is known as limiting molar conductivity and is represented by the symbol $E^\circ_m$. The variation in $\Lambda_m$ with concentration is different (Fig. 3.6) for strong and weak electrolytes.

Can anyone explain what does this sentence mean : "it has been found that decrease in k on dilution of a solution is more than compensated by increase in its volume"

Molar conductivity : $\kappa \times V$ ($\kappa$ is specific conductance), $V$ is volume of solution containing 1 mole of electrolyte.

I understand that molar conductivity increase with decrease in concentration. But at the same time this sentence is contradicting that because it says the decrease in "$\kappa$"(specific conductance) is more than increase in volume Which should decrease molar conductivity. I am confused.


texts: Should the normal mode of vibration leading to the transition state be removed?

texts: I would like to know whether the normal mode of vibration of the reactant should be deleted when calculating $\Delta ZPE$ and $\delta G_{\text{corr}}(T)$, where $\Delta ZPE$ is the zero-point energy difference between the minimum and the TS and $\delta G_{\text{corr}}(T)$ is the difference between the thermal corrections of the minimum and the TS. In the TS with $N$ atoms there are $3N-7$ degrees of freedom. Should I use the same number of vibration in case of the reactant, as well?


texts: What are the applications of quantum field theory to chemistry?

texts: I have a physics background and I learned how quantum field theory is applicable to condensed matter physics, and since some parts of condensed matter physics overlap with chemistry I was wondering if there are any direct applications of QFT to chemistry as well. Also what are the research areas in chemistry that use QFT, because I'm considering doing my graduate work in chemistry and it would be cool if I could use QFT in chemistry as well.


texts: Over time what happens to soluble liquids with different densities

texts:
I have a case with two liquids: Water and another chemical which is miscible in water.
The chemical has a density of 800 g/l so it's 20% less dense than water.

Initially the chemical was mixed with the water but now it has been sitting stagnant for 20 years.

Since such a long time has passed what could I expect to see in terms of the mixing of the liquids? Will the different densities have caused the two liquids to separate? Will there still be a trace of the chemical dissolved in the water?


texts: What polymer can be dissolved in ethanol and is insoluble in water?

texts: I need a polymer with parameters noted above. How to determine the solubility theoretically? Hansen/Hildebrand solubility parameters? Wypych is not the ultimate solution...


texts: Can I convert elemental nitrogen to nitrous oxide?

texts: Can I convert nitrogen to $\ce{N2O}$, to conduct barking dog reaction, where it's needed as oxidizer?


texts: Does this general hybridization rule really apply?

texts:
So this rule is known about hybridization that:
if 4 groups (atoms/pairs of electrons) are attached to the atom -> sp3
if 3 -> sp2
if 2 -> sp
but isn't that true only to specific elements only like carbon/oxygen/nitrogen..?
If you take CCl4, C is sp3, but chlorine has 4 groups around it but it's still not sp3 nor hybridized, it's just an sp3-p bond.
Even for nitrogen like in pyrrole, nirogen has 4 groups around it but it's sp2 because of resonance.
but can someone make it clear? to which elements does that rule apply? what elements undergo hybridization? what elements can they ask about in college regarding that?
Thank you


texts: Mass percent and mole percent of a composition

texts:
The Problem
A gas mixture contains hydrogen, carbon monoxide, and carbon dioxide. Calculate:
a) The mass% hydrogen if the mixture contains 15 mol% $\ce{CO}$ and no $\ce{CO2}$;
b) The molar composition if the mass fraction of $\ce{CO}$ and $\ce{CO2}$ are both 0.35.
My Attempt
I first calculated the molar masses:
molar_mass$\ce{H2}$ = 2.01588 g
molar_mass$\ce{CO2}$ = 44.0095 g
molar_mass$\ce{CO}$ = 28.0101 g

a) The mass% hydrogen if the mixture contains 15 mol% $\ce{CO}$ and no $\ce{CO2}$;

Since the mixture contains 15 mol% $\ce{CO}$ and no $\ce{CO2}$, then the mol% of $\ce{H2}$ must be 85.
I set the mixture equal to 10 mols. This means that there are 1.5 moles $\ce{CO}$ and 8.5 moles $\ce{H2}$. I then converted these values to grams.
1.5 mol $\ce{CO}$ = 42.015 g $\ce{CO}$
8.5 mol $\ce{H2}$ = 17.135 g $\ce{H2}$
The total grams is 59.15 g.
The percent of $\ce{H2}$ would then be 29% since 17.135 / 59.15 = 0.29.

b) The molar composition if the mass fraction of $\ce{CO}$ and $\ce{CO2}$ are both 0.35.

Since the mass fractions of $\ce{CO}$ and $\ce{CO2}$ are both 0.35, the mass fraction of $\ce{H2}$ must be 0.3.
I set the mixture equal to 100 g. This means that there would be 35 g $\ce{CO}$, 35 g $\ce{CO2}$, and 30 g $\ce{H2}$.
Converting these to mols:
35 g $\ce{CO}$ = 1.25 mol $\ce{CO}$
35 g $\ce{CO2}$ = 0.795 mol $\ce{CO2}$
30 g $\ce{H2}$ = 14.88 mol $\ce{H2}$
This gives us a molar composition of
0.88 $\ce{H2}$;
0.07 $\ce{CO}$;
and 0.05 $\ce{CO2}$.
My answers matched up with the solution key, but did I solve this question in the 'right' way? Or is there a better/quicker alternative?


texts: Why is Charcoal such an excellent adsorbent?

texts:
Charcoal (also activated charcoal) is known to adsorb a huge variety of substances including a variety of paints, dyes and many different kinds of ions. Moreover, the amount of adsorption at normal pressure and temperature is high. I know physisorption requires high capacity of Van-der-waal bonding with the adsorbate which is favoured by surface atoms with large, easily-dispersed electron clouds and chemisorption requires actual chemical bond formation which requires highly reactive surface atoms. Charged species get adsorbed to form a double layer when the surface is charged, either due to ionization or due to polarity.

  But charcoal possesses none of the structural specialities required to
  be a great adsorbent. Neither it has charged centres (unlike colloidal
  proteins, or metal sols) nor it has a very high reactivity (Charcoal
  is almost the final product of combustion of wood, bone, sugar etc and
  is supposed to be immune to further oxidation even at considerable
  temperature). Why is it then an excellent adsorbent?


texts: Why isn't PBr3 used to halogenate tertiary alcohols?

texts:
I've been looking into activation of alcohols for nucleophilic substitution, and I've come across a series of reactions that differentiate between primary, secondary and tertiary alcohols. I've seen it written in multiple places that reagents like thionyl chloride and phosphorus trihalides aren't used for tertiary alcohols, but that strong acid is used instead. I was wondering why this was the case, because surely an activated alcohol has a good enough leaving group to progress through an SN1 mechanism.

The only thing I can think of is that the alcohol is too sterically hindered to effectively react with the activating agents. But I have seen a reaction scheme that substitutes a tosyl group from a tertiary alcohol via SN1, which confused me even more.

Any help is greatly appreciated.

Edit: I forgot to mention that I've also seen specified that the Mitsunobu reaction works only on primary and secondary alcohols, and I really hope all of these are linked in some way because that would make this a lot easier.

Edit: from https://www.masterorganicchemistry.com/2015/03/10/tosylates-and-mesylates/#four


texts: Copper plating, is sulphuric acid necessary? Alternative to H2SO4?

texts:
Many links and tutorials on copper plating use a solution that contains copper sulphate / sulphuric acid and hydrocloric acid.

In Sweden, Sulphuric acid is almost impossible to get a hold off. You need a license to buy it, and it costs 100 USD to get one...

What does the H2SO4 do in the electrolyte? Is there an alternative to the acid?

I want to plate PCB copper clads.


texts: What is the process of turning ionic silver solution into colloidal silver solution?

texts:
I've looked at a number of different colloidal/ionic "silver solution generators."  After my research I'm under a few impressions and if they're wrong please let me know.

I also am wondering what the product is that one generator sells to add to the ionic silver to create colloidal silver and is it safe to ingest?  I've already seen enough information to believe that ionic silver is safe. I'm wondering if the additive that turns ionic silver into colloidal silver is safe.

Impressions:

When you set up a silver generator, either homemade or store bought, you send a current through two pieces of silver in distilled water.  The particles released into the water are ONLY ionic silver.

Will colloidal silver form over time?  Will ionic silver precipitate or remain suspended?

I could easily build a machine to do this rather than buy one from a dealer that seems to withhold info to either prevent comparisons or to prevent laymen from building their own.  I'm looking for any and all comments related to this topic.  Thanks

To reply to GM's answer: I hesitate to put up pictures or links to the commercial generators since I'm not sure if that would violate the TOU and I have no interest in advertising for anyone.  I imagine if the commercial generators, which work on same principal as the home made ones, didn't generate at least ionic silver they'd have some explaining (lawsuits) to do to someone and they've been on the market for years.


texts: Mechanism for Diels–Alder of alkene with substituted thiophene sulfone with loss of sulfur dioxide

texts:
I came across a synthesis of centrohexaindane that has the following steps:

This is a Diels–Alder reaction that gives an aromatic ring. I know that alkynes will give this reaction as follows:

But in the scheme, after the initial Diels-Alder to form the product with bridging $\ce{SO2},$ it cannot just lose $\ce{SO2}$ to become aromatic. Does the molecule with the bridging $\ce{SO2}$ get oxidized to have two double bonds like in the second image and then lose $\ce{SO2}?$
The sulfone is the only possible oxidizing agent here (toluene solvent doesn't seem like it would oxidize) and Wikipedia says on its page on sulfones that:

Sulfone is a relatively inert functional group, being weakly basic(compared to sulfoxides). They are non-oxidizing.


texts: Why is dipositive dilithium more stable than neutral dilithium?

texts:
According to J.D Lee, compounds with fraction bond number are unstable. I calculated that the bond order of $\ce{Li2^2+}$ is 0.5 while that of $\ce{Li2}$ is 1. Hence, $\ce{Li2^2+}$ must be less stable than $\ce{Li2}$ due to half bond character.

But, in reality, $\ce{Li2}$ is more stable than $\ce{Li2^2+}$. Why is it so?


texts: What is the final temperature of each substance upon absorbing 2.25 kJ of heat?

texts:
Suppose that $\pu{28 g}$ of silver is initially at $\pu{29.0^\circ C}$. What is its temperature upon absorbing $\pu{2.25 kJ}$ of heat?

My work: $2250 = 0.240 \times 28 \times t - 29$

Solve for $t$ and I get $\pu{340 ^\circ C}$. But the correct answer is $\pu{370 ^\circ C}$ and I have no clue how to get there.


texts: So I'm basically doing an experiment where I measure the effect of pH on the yield of alcohol within the acid catalyzed hydration of ethene. Essentially, all other details aside, I get a mixture of ethanol and ethyl chloride solutions at the end of my experiment. I want to find the total amount of either. I want to use a simple method to determine the amount of each in the solution. I want to avoid using fractional distillation, if possible. I need help to do this.


texts:
Background: I have a journal from my childhood. I applied glue (uhu brand. this one) to the papers almost 10 years ago.

Q: Is there a way to dissolve the glue and make the pages readable?


texts:
Why would the hydrogen sulfide ion be a better nucleophile than a bromide ion?

My professor says that hydrogen sulfide ion is a better nucleophile.

I thought I could determine the better nucleophile was based on available electron density and polarizability. The bromine ion has more available electron density and is more polarizable than the $\ce{HS-}$. Why would it be less nucleophilic?


texts: Plausible Mechanisms for Polyketide Formation from Phloroglucinol

texts:
I am working on modifying the reaction below. I am adding the sulfonate (ignore the sulfonic acid groups shown) groups so that polysubstitution of the phloroglucinol does not occur. In terms of the reactivity of the sulfonate, there should not be any issue, as it is not acidic and will not interfere with the potassium hydroxide in the first step of the original reaction; however, I am worried about how the electron withdrawing properties of the sulfonate will affect the overall reaction. The paper does not attempt to explain the reaction mechanism of this particular step, so I am not sure how exactly this form of substitution will affect my reaction. My only guess as of now is that the keto-enol tautomerization is a stabilizing factor of the final product, rendering substitution of the -OH groups unfavorable; however, this still does not predict how this reaction would be affected by sulfonate groups?

Edit: New possible mechanism for reaction


texts: I was wondering if someone could tell me why do we write down 'x' in front of $\ce{H2O}$ in the reaction that takes place to form rust on an iron material. I searched for it and went through many websites but couldn't get a specific answer so please someone help me.


texts: Certain reduction reactions require electrons as reducing agents. Is the overlapping of orbitals is necessary for electron transfer? I mean if a element $\ce{X}$ is heated and it gives out thermionic electrons then can an oxidizing agent $\ce{Y}$ acquire it and get reduced? If so then will it acquire fast moving electrons or slow moving electrons? What will happen if the inert gas is replaced by $\ce{CO2}$ in an cathode ray tube?


texts: How do IR spectrometers produce light spanning the entire infrared spectrum?

texts:
An IR spectrum covers thousands of wavenumbers, typically $\sim 4000$ to $\pu{400 cm-1}$.

How are the spectrometers able to generate different wavelengths of light covering this entire range of wavelengths?


texts: Negative hyperconjugation stabilizes tricyclopentane derivate

texts: As far as I know, negative hyperconjugation means, that we have electrons that are transferred from a p- or $\pi$- to a $\sigma^*$-orbital. In the lecture, we analyzed a TMS-substituted tricyclopentane derivate (tricyclo[2.1.0.0$^{2,5}$]-pentane-3-one). Apparently, the first one on the left can't be deprotected even by TBAF or boiling MeLi, but the second one easily. If I could deprotect the first one, we'd obtain a 3° carbanion that would do negative hyperconjugation with the TMS group. Would't this be favourable and should be readily feasible?


texts: How can I change the bond type (single, double) of an existing bond in Avogadro?

texts: I have a molecule extracted from the PDB. When I load it into Avogadro, it has some misplaced bond types. I want to correct this, by setting the bond type (single, double) for these bonds. How can I do this?


texts: Assigning Re and Si face for Carboxylic group

texts: Suppose I have a compound $\ce{CH3COOH}$ and I have to assign Re and Si faces. Which of the two oxygens get a higher priority and why?


texts: Why ester reaction with one equivalent of Grignard reagent produces ketone?

texts:
While reviewing my old materials before an external exam which also covers these topic I stopped by one of the reactions - Grignard w/esters:

From what I remember, and what my notes are also telling me, Grignard is performed by creating Grignard reagent containing alkane & MgX. Then, such complex attacks the carbonyl leaving oxygen with a negative charge, which easily deprotonates water creating 2° alcohol.
However, when done with ester, which contains a good leaving group the reaction produces ketone. Is this only because no aqueous workup is performed after the first round?


texts: Why does the mole-fraction equilibrium constant depend on pressure and volume?

texts:
The ratio of rate constants for the forward and backward reactions gives us the equilibrium constant, $K_c$. For a sample reaction:

$$
\ce{A \underset{k_{-1}}{\overset{k_1}{<=>}}  P + Q}\quad \Longrightarrow \quad K_c = {k_1\over k_{-1}} = {C_P C_Q\over C_A}
$$

Per kinetic theory, rate constants depend only on temperature and the presence of any catalysts:

$$
k_i = A_i e^{-E_{a,i}\over RT}
$$

Thus, their ratio (i.e., the equilibrium constant, $K_c$) also must depend only on temperature:

So: Why does $K_x$, the mole-fraction equilibrium constant, depend on pressure and volume?


texts: Infra red stretching frequency of carbon monoxide ligand in borane carbonyl compared to that of free carbon monoxide

texts:
Why is the infrared stretching frequency of $\ce{CO}$ in the borane carbonyl $\ce{BH3CO}$ more than that of free $\ce{CO}$?
Is there any real explanation for this?
There will be a small amount of hyperconjugation of $\ce{H}$ atoms from boron to carbon which would increase the electron density of carbon closer to boron due to which the $\ce{CO}$ bond strength should weaken.
Am I wrong anywhere or there is any other theory that explains this?


texts: Is there any selectivity between the C-2 and C-4 positions of pyridine in SNAr reactions?

texts:
In nucleophilic aromatic substitution (SNAr) reactions on pyridines, displacement of leaving groups at C-2 and C-4 is favoured because the negative charge in the intermediate can be delocalised onto the nitrogen atom.

However, is there any intrinsic difference in the rates of substitution at C-2 and C-4 (assuming the leaving groups at both positions are the same)? If so, why?


texts: What is the significance of increasing (and decreasing) the number of ionic releaxation steps in a plane wave DFT calcuation?

texts: The number of ionic relaxation steps is one of the adjustable parameters while setting up a DFT calculation using a commercial code such as VASP. I was wondering what's the significance of this value?


texts: Why does adding an acid speed up electrolysis of water?

texts: I've read in several places that when electrolyzing water into $\ce{O2}$ and $\ce{H2}$, that adding a salt or an acid will speed up the process. Why is this?


texts:
At each electrode-electrolyte interface there is a tendency of metal ions from the solution to deposit on the metal electrode trying to make it positively charged. At the same time, metal atoms of the electrode have a tendency to go into the solution as ions and leave behind the electrons at the electrode trying to make it negatively charged. At equilibrium, there is a separation of charges and depending on the tendencies of the two opposing reactions, the electrode may be positively or negatively charged with respect to the solution. A potential difference develops between the electrode and the electrolyte which is called electrode potential. When the concentrations of all the species involved in a half-cell is unity then the electrode potential is known as standard electrode potential.

Above is an excerpt from my book.

It says that at equilibrium the potential difference develops between electrode and eletrolyte and it is electrode potential.

But at equlibrium, should not the electrode potential should be zero as at equlibirum there should not be any tendency of reaction to occur?


texts: Can we break double bonds by using laser and heat?

texts:
If it is possible then give an example for it. That chemical reaction is in this process.
step 1: {Reactant + heat(sunlight)} gives weakened bonded product1
step 2: {product1 + laser} gives {one solid product + one gas product}


texts: Variation in pressure for a gas phase reaction

texts:
Predict how the total pressure varies during the gas-phase reaction
  $\ce{N_2}(g)+ 3 \ce{H2}(g) \rightarrow 2 \ce{NH3} (g) $ in a constant volume container.

Reference: Atkin's Physical Chemistry, Tenth Edition, Chapter 20, Exercise 20A.1 (b) on page 870

My attempt at a solution: Assuming ideal gas behaviour we know that pressure is proportional to number of moles (volume and temperature held constant). Also, by observing the reaction stoichiometry the final pressure should be half the initial pressure as the no. of gas moles changes from 4 to 2

Initial no. of moles $n_i = n_{\ce{N2}} + n_{\ce{H2}}$ with no ammonia present.

at an arbitrary instant in the reaction $\alpha$ is the fraction of $\ce{N2}$ that has reacted.

So total no. of gas moles: $n = [n_{\ce{N2}}(1-\alpha)] + [n_{\ce{H2}}-3\alpha n_{\ce{N2}}]+ 2\alpha n_{\ce{N2}} $ ; the first two terms being the change in no. of moles of reactant and the last one being the no. of moles of ammonia produced.

This simplifies to, $n = n_{\ce{N2}} + n_{\ce{H2}}-2\alpha n_{\ce{N2}}$

What I think the question wants from me is a $P$ at an arbitrary instant given as a fraction of $P_i$ i.e $P_t= $$P_i$*[term depending on  $\alpha$]. Also substituting $\alpha$ = 0 or 1 should yield $P_i$ and $\frac{1}{2}P_i$ respectively.

For that, I am guessing the expression for $n$ should be expressed as a fraction of $n_i$.  However, I can't seem to think of the necessary algebra to obtain such an expression.

EDIT: Inspiration struck, what if I do the following:

$n = n_{\ce{N2}} + n_{\ce{H2}}-2\alpha n_{\ce{N2}}$

gives,

$n = (n_{\ce{N2}} + n_{\ce{H2}})(1-2\alpha \frac{n_{\ce{N2}}}{n_{\ce{N2}} + n_{\ce{H2}}})$

which is the same as, $(n_{\ce{N2}} + n_{\ce{H2}})(1-2\alpha .\chi_{\ce{N2}})$ where $\chi_{\ce{N2}}$ is the initial mole fraction of nitrogen in the reaction mixture

so, $n = n_i(1-2\alpha .\chi_{\ce{N2}})$
and consequently, $P_t = P_i(1-2\alpha .\chi_{\ce{N2}})$

Would this be a valid expression for describing the variation in pressure during the gas phase reaction described above?


texts: is it possible to store formic acid longer if frozen?

texts:
I would like to know if formic acid (concentrated to 85%) is stable (no chemical reaction) when frozen.
Is it a good solution to store it for many years?


texts:
I've noticed that water obtained from melting ice cubes (by keeping them in the open) tastes different from water cooled to the same temperature.

Furthermore, the taste goes away if you keep it in the open for a sufficient duration of time.

I can think of these possible explanations:

Dissolved gases being released
Something to do with the crystal structure of ice
Something to do with dissolved minerals

The Internet is giving me all sorts of varying answers.

Exactly what chemical differences exist between meltwater and cold water?


texts: Unlike polyethylene that there are LDPE, HDPE, or LLDPE, when it comes to polypropylene the issue becomes about copolymer (homo/ copo/ block copolymer) or location of methyl group (isotactic/ atactic/ syndiotactic)? Why does polypropylene not have designations based on density?


texts: DOSY-NMR: How to calculate the volume of the molecule from the diffusion coefficient?

texts: DOSY-NMR allows for the determination of the diffusion coefficient of the analyte molecule. How do I calculate the volume/radius of the molecule from the diffusion coefficient?


texts: A reversible exothermic reaction between a molecule in an excited triplet state and a reducing agent

texts:
Say I promote a molecule to a triplet state via repeated electronic excitation events.  Here, this is going to mean that an electron from the HOMO level, originally with a spin-UP and spin-DOWN electron, will be promoted to the LUMO level such that its spin is the same as the electron left-over in the HOMO level (we can then use the Pauli exclusion principle to partially understand that the triplet state will generally have a longer lifetime than the typically higher energy singlet state).  The classic example of a molecule in a triplet state is oxygen (though here, this is also the ground state, which is somewhat unusual):

Prior to returning to the ground state via phosphorescence or a reverse intersystem crossing event, let's say that the triplet $T_1$ state molecule reacts with a reducing agent via an exothermic bond formation process, and that the reaction is reversible.  Consider that there are numerous instances where triplet state reactivity is higher than ground state reactivity.

The following two things are unclear to me:

(1) When the reducing agent dissociates, is the molecule in the $T_1$ triplet state or the $G_0$ ground state?  If the molecule is still in the triplet state, can it enter the ground state while remaining bound to the reducing agent?

(2) Call the energy gap between the relevant $T_1$ triplet state and the $G_0$ ground state $E_1$.  Call the energy released into a surrounding thermal bath by the reducing agent reacting with the molecule in the $T_1$ triplet state $E_2$.  Must $||E_2|| > ||E_1||$?

My guess is that the pair of electrons donated by the reducing agent will necessarily set  $||E_2|| > ||E_1||$ and that the molecule will be left in the ground state upon dissociation of the reducing agent since the electrons will be reallocated to properly satisfy spin-pairing requirements.


texts: Delta G values for Pyruvate--> Alanine vs. Oxaloacetate -> Aspartate ->Asparagine

texts:
What are the delta G values for the mammalian (human) biosynthesis of alanine from pyruvate, and for the conversion of oxaloacetate to asparagine? (assuming no particular cellular restriction or other systemic pressures like catalysis or anabolism)

I am aware that oxaloacetate must be converted to aspartate and then to asparagine.  Based on the fact there are two steps to that conversion, I assume that cumulatively the delta G value is higher for the oxaloacetate to finally get to asparagine. So I want to know how much of a difference there is in the delta G values of these two conversions.

This is NOT a homework question, it is to better my own understanding.  I would welcome peer-reviewed literature, or other resources if you deem them applicable.


texts: Is there a paper glue that is NOT dissolved by acetone?

texts:
Short version of the question: I need a spray-on glue that will stick paper to wood that isn't dissolved by acetone.

Long version: I am trying to glue paper on wood. It's a big sheet of paper and I need it stuck on throughout because then I cut the wood-with-paper-on-it into pieces with a laser cutter. Therefore, I'm using a spray glue that can cover the whole sheet of paper quickly and evenly. I have tried a couple different glues. After the pieces are cut, I want to spray an acrylic coating over the resulting pieces to seal them.

The process works except for one problem: if the acetone in the acrylic spray seeps through, it dissolves every glue I have tried. I try to go light with the acrylic, but more than 50% of my pieces end up with the paper coming loose from the wood. I can glue it back on later, but that means that the positioning of the paper is way less precise and the edge seal isn't there, making it susceptible to water damage.

Are there any glues anyone knows of that meet this challenge?
(I suppose, alternatively, is there an inexpensive sealant that doesn't use acetone? But I know the acrylic will hold up to the abuse these playing pieces are going to take, so I am hesitant to swap out that part of my process.)


texts:
Three professors argue it is non-polar.

My professor argues that it is a monopole, like most ions.

The structure of the triiodide ion places a negative formal charge on the central iodine atom. The molecular geometry is also linear (at least according to VSEPR), and its electronic geometry is trigonal bipyramidal. Given the high amount of symmetry, shouldn't triiodide be non-polar? Sure, it might have a charged central atom, but so does carbon dioxide.

What's the answer?


texts: What does a change in temperature do to the concentration of gases at equilibrium?

texts:
I am confused about a specific part of Le Chatelier's Principle. My question revolves around a homework assignment question:

$$\ce{2SO2(g)  + O2(g) <=> 2SO3(g)} \qquad\Delta H^\circ = -198.2\:\mathrm{\frac{kJ}{mol}}$$
Comment on the changes in the concentrations of $\ce{SO2}$, $\ce{O2}$, and $\ce{SO3}$ at equilibrium if we were to increase the temperature of the system.

Now I understand that increasing the temperature of an exothermic process will cause the equilibrium to shift towards the left (in the direction of the endothermic reaction); however, what does the temperature do to the concentrations of the gases?  I think it does nothing, but I am not sure.


texts: Why for compounds of elements in a group with larger anions have nearly constant lattice enthalpy?

texts:
Why do compounds of elements in a group with larger anions have nearly constant lattice enthalpy?

In the reasons for the decrease of the solubility of sulphates of alkaline earth metals, it is given that:

  "the size of anions being much larger compared to cations the lattice enthalpy will remain almost constant within a particular group"

I am unable to understand the reasons behind it.

When I was searching I also found that larger cations stablise larger anions and small cations stabilise small anions. I didn't understand this.
Please explain.


texts: How to interpret m quantum number values?

texts:
If one electron has the quantum numbers $n = 4,\ l = 3,\ m_l = +2,\ m_s =-1/2$ and another electron has the quantum numbers $n=4,\ l= 3,\ m_l = -2,\ m_s=+1/2$, what are the similarities between the orbitals in which the electron's are found?

My answer is : They have the same number of energy shells. They have the same shape. Their orientations are different and they have different directions of spin.
I checked the answer and it said that the first one lies on the $x$ and $y$ axis and the other one will lie between the $z$ and $y$ axis. But how do they know that? If $m_l= +2$, does that necessarily mean it lies on the $x$ and $y$ axis. And if $m_l = -2$, does that mean it lies between the $x$ and $y$ axis?


texts: Can two positive ions be next to each other in a formula?

texts:
Let's say I want to find the oxidation numbers of the atoms in a chemical formula.

For example: In $\ce{H3AsO3}$,

Oxygen has a $-2$ charge. They're $3$ of them, so its $-6$

Hydrogen has a $+1$ charge. They're $3$ of them, so its $+3$.

So arsenic must have a charge of $+3$ for all the charges to add up to be $0$? Correct?

However, my professor keeps telling me to keep the positive oxidation numbers away from each other. I thought it only applied when drawing Lewis structures or resonance structures.

Is that a rule when writing a formula?


texts: How semi-permanent hair dye stays in place?

texts: Semi-permanent hair dye washes off after several months. What mechanism(s) keep the dye in the hair? (I assume it's not primary chemical bonds, otherwise it would be permanent)


texts: Why is a buffer solution most effective when concentrations of salt and acid are the same?

texts: Why does a buffer work most effectively when the concentration of salt and acid is 1:1?


texts: How much volume of oxygen will be required for complete combustion of 40 ml of acetylene and how much volume of CO2 and H2O will be formed?

texts:
How much volume of oxygen will be required for complete combustion of 40 ml of acetylene and how much volume of $\ce{CO2}$ and $\ce{H2O}$ will be formed?

After balancing the left-hand side produces 5 volume of oxygen and 2 volume of acetylene. However, the right-hand side produces 4 volume of carbondioxide and 2 volume of water. Why doesn't the volume on LHS and RHS match? Or how is it matched?

Is it correct that 100 ml of oxygen and 40 ml of acetylene produce 80 ml of $\ce{CO2}$ and 40 ml of $\ce{H2O}$? If so, what happened to 20 ml on the right hand side?


texts: Can I use pure zirconium as an anode in electrolysis?

texts: I read that zirconium is not very reactive even when supplied with a current in an electrolyte. If I had a sizable piece of it, can I use it to perform electrolysis for rust removal of items? Would it have the same or similar results to graphite which results in a less messy process, namely the black film left on parts? Is it toxic?


texts:
Is there a formal definition or algorithm that can take a list of reactions and tell me whether it contains a set of species that can produce itself autocatalytically?

It is clear that the following reaction is autocatalytic:
$$\ce{
A + B \to 2 B
}$$
B appears on both sides of the equation, so it's a catalysis reaction, and there is an extra B produced on the right, so it catalyses its own production from A.

But the following reaction scheme can also be considered to contain autocatalysis:
$$
\ce{B + C \to D + E\\
A + D \to 2C}
$$
If this system starts out with plenty of A and B, together with one molecule of C, then the C molecule can react with a B to produce a D, which can then react with an A to produce two C's — whereas, without the initial "seed" molecule, no reactions will take place. (I'm neglecting reverse reactions here of course, but hopefully it gets the point across.)  The autocataltic cycle can easily be seen in the following diagram, where circles represent species and boxes represent reactions:

Another non-obvious example of autocatalysis is a reaction scheme of this form:
$$\ce{
A + C \to C + D\\
B + D \to D + C + E}
$$
Here, C and D each catalyse the production of one another from the precursors A and B. I'm aware of Kauffman's definition of reflexively autocatalytic sets, which applies to schemes of this form, but would miss an autocatalytic cycle of the kind shown above, since it doesn't consist of single-step catalysis reactions. So I'm looking for a definition of autocatalysis that would include both cases, as well as (hopefully) other, more complex schemes that I haven't yet thought of.


texts: Are CaOCl2 and Ca(OCl)2 same or different?

texts: Are the two compounds same? Also, which one is considered bleaching powder? Please explain their differences on the basis of their structures also.


texts:
A complex formulated as $\ce{Cs_x[NbCl6]}$ has spin-only magnetic moment $\mu_{s.o}$ of approximately 2 B.M. From this value calculate how many unpaired electrons are present.

Spin-only magnetic moment is related to the number of unpaired electrons by the formula

$$\mu_{s.o}= \sqrt{n(n+1)}$$ where $n$ is the number of unpaired electrons.

I let $\sqrt{n(n+1} = 2$ and solved for $n$. I got two values one $+$ and one $-$. Do I just take the positive value and round it to the nearest whole number. In this case I got $n_+= \sqrt{5} - 1 \approx 1.2$.

Does this mean there is $1$ unpaired electron?


texts: How do I write many cyclic voltammetry curves in Nova?

texts:
We are making an electrochemical research on supercapacitors that involves checking stability of our material. That requires repeated writing of cyclic voltammetry curves. Our goal is to write at least 2000 of them, but there is a problem with Nova software (version 1.8, to be specific): if we want to write even 50 cycles, Nova complains that "only last 30000 point will be written". We can adjust how many points are plotted, but when it comes to 2000 cycles, it's impossible to extract any information from them (15 points per one curve is just ludicrous).
Has anyone dealt with such problem? Is there a simple solution?


texts: What kind of interacion is there between a nanoparticle and its functionalizing coating?

texts: The functionalization of nanoparticles (with coatings such as polymer ligands; see image) are very common (for example, DNA-functionalizied gold nanoparticles). What's the type of interaction between nanoparticles and their coatings? And why is it more favorable than forming aggregations of the the nanoparticles?


texts:
I require Congo red indicator for an experiment I wish to perform involving dipping a cellulose sponge into an acid and a base.  I first want to dye the cellulose sponge with Congo red, and observe the color change of the sponge as I place it in acids and bases.

Congo red apparently binds to cellulose and thus is suitable for this experiment.  Unfortunately the laboratory doesn't have this indicator at the moment.  Are there any other indicators that could be used for this effect instead?


texts: Can an aqueous solution conduct electricity forever?

texts:
We know that pure water does not conduct electricity, but salt water is a decent conductor. This is commonly explained by saying that “the ions carry the current through the solution”, which is an incomplete explanation, because it does not  indicate what happens when all of the ions have migrated to the electrodes.

More complete explanations of conduction through a salty solution (like this one or this one) rationalize the conduction of electricity in terms of a reduction reaction that takes place at the anode and an oxidation reaction that takes place at the cathode. In the case of salt water, chlorine gas ($\ce{Cl2}$) is formed at the anode and hydrogen gas ($\ce{H2}$) is formed at the cathode.

This explanation seems reasonable, but it implies that the conduction of electricity through a solution is fundamentally different than the conduction of electricity through a wire. A copper wire is (usually) unchanged, even after a large amount of electricity passes through it. In contrast, when electricity passes through salt water, two chemical reactions occur (one at each electrode), which fundamentally change the composition material.

This implies that it is not possible for an aqueous solution to conduct electricity forever. Since we are driving a chemical reaction, we are either consuming our salt (forming $\ce{Cl2}$ gas in the case of an NaCl solution or plating it onto the electrodes in other cases), or we are consuming the water by forming $\ce{H2}$ or $\ce{O2}$ gas.

This is surprising to me. So, I’m asking if my thinking is correct: is it possible for an aqueous salt-containing solution to conduct electricity forever, or it will it always eventually consume the reactants and stop conducting electricity as I have surmised?


texts: How to know which reduction and oxidation reactions occurred?

texts:
We just had a lab experiment on galvanic cells and we used 0.5 M and 1 M iron(III) nitrate solution at the anode (iron electrode) and 1 M and 0.5 M copper(II) nitrate solution at the cathode (copper electrode) for runs 1 and 2, respectively.

How can I determine which redox reaction occurred? There are many possible reactions $(\ce{Cu^2+ + e- -> Cu+}$ or $\ce{Cu^2+ + 2e- -> Cu}).$ The experimental cell potential we got was 0.48 V and 0.44 V. Temperature that we recorded was 28 °C and 29 °C for runs 1 and 2.


texts:
Could someone perhaps check the rules of thumb that I use for estimating the carbon footprint of hydrocarbon fossil fuels- I'm using schoolboy chemistry theory, and possibly falling into schoolboy traps.

2 litres of LPG weigh 1 kilo
4 litres of petrol/gasoline weigh 3 kilos
6 litres of diesel fuel weigh 5 kilos

If I assume- can I?- that the above fuels are saturated hydrocarbons, propane or longer, with two hydrogen atoms for every carbon atom, then 7 kilos of fuel correspond to 6 kilos of carbon, which in turn correspond to 22 kilos of CO2.

This is a simplistic view, which doesn't take account of the production and distribution impact of road fuels, but if say, I fill up my 1980 Land Rover- whose environmental impact of manufacture ended 37 years ago- with 100 litres of LPG, I can think : 100 litres of fuel, 50 kilos of hydrocarbons, 42 kilos of carbon. I've got to deploy 42+ kilos of biochar before I can drive on with a clear conscience.

Thanks for any help.


texts: Synthesis of the tetrachloroaluminate(III) anion

texts:
Looking for random chemicals, I found a reference on the anion and thought that it could be synthesised from common laboratory reagents:

$$
\begin{align}
\ce{2 Al + 2 NaOH + 2 H2O &-> 2 NaAlO2 + 3 H2}\\
\ce{NaAlO2 + 4 HCl &-> NaAlCl4 + 2 H2O}
\end{align}
$$

The first reaction obviously occurs at high yield at STP. Does the second reaction occur at STP or not? If not, how can the $\ce{AlCl4^-}$ ion be synthesised?


texts: Entropy of Activation and Temperature Dependence

texts:
I am trying to understand the extrapolation of enthalpy $\Delta H^{\ddagger}$ and entropy of activation $\Delta S^{\ddagger}$ from the Eyring equation. It's typically cast as:

$$\ln\left(\frac{k}{T}\right) = \frac{-\Delta H^{\ddagger}}{RT} + \frac{\Delta S^{\ddagger}}{R} + \ln\left(\frac{k_\mathrm{B}}{h}\right)$$

where $k$ is the rate, $T$ is the temperature, $R$ is the ideal gas constant, $k_\mathrm{B}$ is the Bolztmann constant, and $h$ is the Planck constant. However, the entropy itself also has a temperature dependence in principle (i.e. harmonic oscillator entropy is a function of temperature). Is there a way to determine the temperature dependence of the entropy of activation from the Eyring equation for a real experiment?


texts: Arrange in the order of their reactivity of SN2 reaction

texts:
Here in case of (1) it is more favorable towards SN1 reaction as it will create benzyl carbocation which is very stable.
(2) Here it is more favorable towards SN1 as it is first of all allyl carbocation and in resonance with the benzene and the double bond.
(3) It is allyl carbocation, so it is less favorable to SN1 than (1) and more favorable to SN2.
(4) It is the most favorable towards SN2 reaction.
Hence the order of reactivity towards SN2 reaction should be
(4) > (3) > (1) > (2)
But the answer is
(2) > (1) > (3) > (4)
Why?


texts: Chirality of symmetrically substituted biphenyl

texts:
I am facing trouble with the following problem: is 2,6-dimethyl-2',6'-dinitro-1,1'-biphenyl chiral?

My idea is that there is a axis of symmetry along the line joining the two benzene molecules. Hence it should be achiral.
However my book states it otherwise.


texts: Does the ignition point of flammable substances changes when provided a pure oxygen atmosphere?

texts: I'm wondering if autoignition point decreases for substances when provided higher oxygen concentration.


texts: Solubility of alcohols in non-polar solvents

texts: The solubility of an alcohol in a non-polar solvent (like hexane) increases with size of the alcohol, as the non-polar chain increases. However, as the chain keeps increasing, will the solubility eventually start to drop because the molecule becomes too large?


texts: Is [7]сirculene aromatic or anti-aromatic?

texts:
This compound is called [7]circulene and is one of the examples of non-planar aromatic systems (1). From the first overview of this compound, it is observed that there are 7 benzene rings so one would conclude that it is an aromatic compound:

There are $7 \times 4 = 28$ $\pi$-electrons, so this compound satisfies the criteria of anti-aromacity. Then how come this compound is aromatic?

(1) Smith, M. March’s advanced organic chemistry: reactions, mechanisms, and structure, 7th ed.; Wiley: Hoboken, New Jersey, 2013, p. 48, compound 40.


texts: Carbocation formed from neopentyl halide is primary in nature. So it is not stable. Although it undergoes rearrangement reaction to form tertiary one, now it can undergo SN1 easily. So if we say it undergoes directly in SN1 will it be okay?


texts:
I was looking into machinable wax, and found it's based on dissolving LDPE into melted wax. While I understand the normal salt dissolving in water process, I'm not really sure how plastics can dissolve into wax. Do the plastic chains unravel and get suspended in the wax?

Here's a video of the process.


texts: How are elements used in the human body (for example) encoded for in the genome?

texts: Given that bones require calcium and iron is used in red blood cells, how are these materials gathered by the developing organism? Is it possible that very small quantities used as "references" are somehow stored in the human egg? Or is there some way of encoding for an element in DNA without any amount of the element already available?


texts: When to use chromatographic separation vs vacuum-assisted rectification distillation?

texts:
I'm trying to understand a bit more about industrial scale separation processes. One particular element I'm interested in is the question as to when chromatography (HPLC or Simulated Moving Bed) may be preferable to vacuum-assisted rectification distillation.

My first thought would be that chromatography sees its greatest industrial use when processing & separating easily damaged compounds, or to select an individual compound for separation through ion exchange chromatography. This, by comparison to vacuum-assisted rectification distillation, where differing vapor pressures allow for high-purity separation -- but requires the addition of heat to material that may destroy easily-damaged compounds. Would love some help on this! Thank you!


texts: What is a good resource for learning about the intermolecular bonding in water beyond high school?

texts: I'm writing a paper for school on boiling water at various temperatures and pressures, but only noting cases wherein high temperatures were achieved without boiling under low pressure (metastable states). I haven't been able to find a good explanation for this phenomenon other then the chaotic nature of boiling coming from heterogeneities. I believe it is because of the high surface tension, but I have not been able to find any in depth resources for intermolecular bonding (in water) other than at the high school level (hydrogen bonding). I'm just looking for some guidance, thank you.


texts: Orbital Electronegativity Considerations in Resonance Structures

texts:
After consulting three organic chemistry texts (Wade, Klein, and Brown), only one actually clearly delineates a few guidelines for picking the most significant resonance structure. The others mention the same factors (maybe less one or two). So in sum, the important factors to consider are:

1) A filled valance shell is preferable to a partially filled valance shell.

2) The more covalent bonds the better.

3) Least separation of oppositely signed charges. I'm thinking this is a Coulombic effect. Some books imply formal charge through the term "charge" but what about partial charges (which are much more reflective of true charges than formal charges. Which one should I really be looking at? Least separation of opposite formal charges or opposite partial charges?

4) Negative charges should generally be assigned to the more electronegative elements; the opposite is true for electropositive elements. Again, formal charge misleads - consider the ammonium ion (positive formal charge on nitrogen; negative partial charge on nitrogen). Again, one book implies formal charge but really, isn't looking at partial charges a bit more informative?

5) Unmentioned factor in any of the three textbooks: What about hybridization? If we have a molecule with two nitrogens, one $\ce{sp}$ hybridized and one $\ce{sp^2}$ hybridized but otherwise identical, shouldn't we also take into account "orbital electronegativity" - i.e. the ability of hybrid orbitals with higher s-character to better stabilize negative charge (and conversely higher p-character better stabilizes positive charge)?

6) Unmentioned factor in any of the three textbooks: Induction? Shouldn't induction also play a role in resonance stabilization? Resonance delocalizes electron(s); can't induction further stabilize electrons? debunked.


texts: Do liquid O₂ and N₂ form ideal solutions?

texts: I suspect they do, but could not find data on this. (I mean at temperatures near those used in the distillation of liquid air.)


texts: Abundance of sulfur containing compounds in the air

texts:
I noticed a piece of jewelry has tarnished, so I looked up information about silver tarnishing. I read that this is due to the formation of silver sulfide on the surface of my necklace and that the sulfur is pulled from the air.

My question is, how abundant are sulfur containing compounds in the air? I know sulfur is by no means rare, but I guess I'm just confused as to why pretty much everything silver ends up tarnishing -- a box of silverware unopened for years can be tarnished.

How abundant are sulfur containing compounds in the air? Is the tendency of silverware to tarnish often/easily due to reactivity? If so, why doesn't carbon react to silver in the same manner and thus give way to a carbon-based tarnish?


texts: Why does the ionic product of water remain constant after addition of non-neutral solute?

texts:
In my textbook, it is given that the ionic product of water $K_\mathrm{w}$ remains constant even when a non-neutral solute such as an acid is added to it.

$$K_\mathrm{w} = \ce{[H3O+][OH-]}$$

When a strong acid is added to water, the concentration of $\ce{[H3O+]}$ increases. Yet the $K_\mathrm{w}$ must remain constant. But how? How does the concentration of $\ce{[OH-]}$ decrease?


texts: Should I be worried about the waste from "sugar rockets" and other potassium nitrate fireworks?

texts:
"Sugar rockets" or sparklers made of metal fillings, potassium nitrate and some carbon compound are easily made, and there is a lot of tutorials and videos on the internet suggesting them as relatively safe and non toxic DIY fireworks.
However reading on the potassium nitrate reaction, it decomposes to potassium nitrite when heated. This compound is toxic, and is suspected to be mutagenic as well. It is also an oxidizer on its own.
So I have safety concerns and questions:

Do the charred remains of potassium nitrate fire experiments need to be handled as toxic waste?
If potassium nitrite is an oxidizer, what does it decompose to when burned along with a carbon compound?


texts: MO diagram for pentaamminechlorocobalt(III)?

texts:
I was considering the MO diagram for [Co(NH3)5Cl]2+, and figured it’d be as follows:

5 sigma interactions from the NH3 ligands; by reducing a reducible representation one obtains 2A1 + B1 + E

2 pi interactions (pi donation from Cl- px and pz orbitals), which have symmetry E

And the cation atomic orbitals, which we just read off the character table.

Unfortunately this results in a lot of confusing interactions in the MO diagram.

What would the MO diagram look like, and are my group orbitals correct?

Thanks!


texts: Would gas come out of solution in an infinite volume?

texts:
Say I have an infinite volume of water with some level of dissolved air in it. I lower the pressure to below the gas' saturation pressure. Does the air come out of solution if there are no interfaces (nuclei) for it to begin? If so, what is the driving force behind the formation of the bubbles? Are there any estimations of the time that it would take to form a bubble of a given size, or an estimation of the equilibrium size of said bubble? Presumably it would be a balance between the surface tension, radius and the water pressure (like $P + 2S/R$)...

To give some motivation, I have a cavitation tunnel where I can apply a pressure field to a large volume of water. In the literature, people speak of homogeneous nucleation where fluids below saturation pressure start to release their gas as bubbles, and I'm struggling to understand how that occurs.


texts:
Predict whether these $1.0~\mathrm{M}$ solutions are acidic, basic, or neutral. Lets start with $\ce{CH3NH3+NO3-}$

How do I approach a problem such as this?

I certainly do not know all the chemical compounds that exist thus what is my method?

I am guessing that $\ce{NO3-}$ does not hydrolyze and $\ce{CH3NH3+}$ does.

Thus, $\ce{CH3NH3+ + H2O -> CH3NH2 + H3O}$ = ACID

(b) $\ce{NaI~(aq)}$

$\ce{Na}$ does not hydrolyze and neither does iodine, but why?

(c) $\ce{NaNO2}$

$\ce{Na}$ again does not hydrolyze but from the first example neither does $\ce{NO2}$

Does this have something to do with either the solutions have a hydrogen atom or $\ce{OH-}$ molecule?


texts: I plan to store D-cell batteries in a winter home.  The shelf-life is finite: is there any reason not to freeze or refridgerate the batteries to extend the shelf life?


texts:
The question is this:

  You want to make oxirane from ethene and oxygen gas:
  $$\ce{2 C2H4 + O2 -> 2 C2H4O}$$
  The flow into the reactor is constant at $\pu{200kmol/h}$ of $\ce{C2H4}$ and $\pu{90kmol/h}$ of $\ce{O2}$. Only 6% of the ethene reacts in the reactor. 98% of the unreacted ethene flowing out of the reactor is filtrated and recycled (sent back into the reactor). Oxygen and oxirane passes through the filtrator.

  Calculate the flow of gas out of the filtrator:

  with no recycling, and
  with recycling.

There has to be something wrong with the question (or my translation of it, sorry) because given this information the net amount of ethene in this system is just going to increase.


texts: Most combustion happens involves the fuels burning in an oxidant. But there seems to be no reason that it cannot happen in the opposite way. Are there any experiments on oxygen burning in hydrogen? Or some oxidant in solid state (like $\ce{KMnO4,KClO3,}$...) burning in a reductive gas?


texts: How much precipitation occurs for a given ionic product?

texts: Let us say we have a salt AB in water. Suppose the ionic product exceeds the solubility product at a particular temperature. Now, I know that the ions will precipitate out of the solution. My doubt is, how much of the ions will precipitate? By saying "precipitation starts", do we mean that all the ions will precipitate, or will some ions remain in the solution?


texts: Temperature Dependence of The Conductivity of Electrolytic Solutions

texts: I have learned in my chemistry text books that the conductivity of electrolytic solutions increase with the increasing of temperature because the ions of electrolytic solution move faster by getting more thermal energy. But a question arose in my mind if there exist any mathematical equation which can describe the conductivity of electrolytic solutions as a function of temperature. I searched about it on internet but I got nothing satisfactory. Does any equation exist which can model the electrolytic conductivity as a function of temperature?


texts: Calculating percentages of microstructures in equilibrium phase diagrams (engineering)

texts:
So I have an equilibrium phase diagram of steel and I am asked to 'Calculate the proportion of pearlite in the microstructure of 0.4 wt% C steel just below the eutectoid temperature (727 °C).'

I have been using the forumlas

$Wa=\frac{Cb-Co}{Cb-Ca}$%

$Wb=100-Wa$%

$Ca=weight$% of (Carbon in this example) at the first intersection point on the eutectoid line.

$Cb=weight$% of (Carbon in this example) at the second intersection point on the eutectoid line or the bottom of the 'V'. I don't know how to explain any better sorry.

So looking at my diagram, I see that $Ca=0.022wt$% Carbon and $Cb=0.76wt$% Carbon, and $Co$ is just 0.4%.

So $Wa=\frac{0.76-0.4}{0.76-0.022}$%

$=0.487805%$%

This is where I am confused. What exactly is Wa? Is that how much ferrite/austenite/cementite that is in the pearlite then? Or how much pearlite is at that point compared to ferrite? And in any case, what does that mean Wb is?

Any help would be much appreciated. Thanks


texts: Which plastic can be partially broken by pressure easily?

texts:
I need to create a container which hold ~150 to 500 ml water. My plan is to create something like a inverse cone. I will apply pressure (~20psi) on the top of the cone and I want to create a hole at and only at the tip of the cone.

I plan to make the tip of the cone thinner, so that it will  be easier to be break. However, I am new to plastic. Would anyone please give me some suggestion of material that I should use?

Thanks


texts:
Air is 1% argon.  Argon is heavier than air.

Why doesn't the argon concentrate in low-lying areas, choking out life there?


texts: Do Sulfuric Acid and Calcium Hydroxide Completely Neutralize One Another?

texts:
I just completed a unit test at school in which there was a simple fill in the blanks question which asked:

  Would 1 mol of sulfuric acid and 1 mol calcium hydroxide in water form an acidic, basic, or neutral solution?

The answer I wrote was neutral.

My reasoning was that sulfuric acid ($\ce{H2SO4}$) has two protons it can donate, and calcium hydroxide ($\ce{Ca(OH)2}$) has two protons it can accept. However, after the test I realized that H2SO4 dissociates into HSO4- which is a weak acid and won't dissociate completely.

After some research I have consistently found that the neutralization equation is written as: $\ce{Ca(OH)2 + H2SO4 -> CaSO4 + 2H2O}$

Do sulfuric acid and calcium hydroxide completely neutralize  one another? Or was I wrong to say that the resulting solution is neutral.

Could someone please explain why I am right or wrong?


texts: What are analytical expressions for the isothermal change of Gibbs energy?

texts:
The change of Gibbs energy at constant temperature and species numbers, $\Delta G$, is given by an integral $\int_{p_1}^{p_2}V\,{\mathrm d}p$. For the ideal gas law, $p\,V=n\,RT$, this comes down to
$$\int_{p_1}^{p_2}\frac{1}{p}\,{\mathrm d}p=\ln\frac{p_2}{p_1}.$$
We find this logarithm in many formulas in chemistry.

I tried and failed to find a general formula for $\Delta G$ for the Van der Waals gas (see this question on the physics board).

It makes me wonder:
Is there even another case of a chemical situation, other than the ideal gas, where $\int_{p_1}^{p_2}V(p)\,{\mathrm d}p$ or $\int_{V_1}^{V_2}p(V)\,{\mathrm d}V$ is known analytically?

My questions are mostly motivated by the desire to understand the functional dependencies of the chemical potential $\mu(T)$, that is essentially given by the Gibbs energy. For the ideal gas and any constant $c$, we see that a state change from e.g. the pressure $c\,p_1$ to another pressure $c\,p_2$ doesn't actually affect the Gibbs energy. The constant factors out in $\frac{1}{p}\,{\mathrm d}p$, resp. $\ln\frac{p_2}{p_1}$. However, this is a mere feature of the gas law with $V\propto \frac{1}{p}$, i.e. it likely comes from the ideal gas law being a model of particles without interaction with each other.


texts: pH change with pressure in a bicarbonate buffer system

texts: Looking at small scale bioreactors with no added pressure (1atm) compared to a commercial bioreactor which is pressured to 5 psi, where both have the same concentration of sodium bicarbonate, if both reactors are at pH of 7.2, should the pCO2 be the same as well? I've been trying to figure this out using Henry's law as well as the Henderson-Hasselbach equation but feel that the added pressure means that the equilibria for solubility and also acid dissociation should be altered and make the previous question false. Thoughts?


texts:
Which substituent should be placed first (in case of alphabetisation)?

isopropyl-
methyl-

I have come across two compounds: 1-methyl-3-methoxy-4-isopropylbenzene and 1-isopropyl-4-methylcyclohexane

So, is “iso” taken care of in case of alphabetisation? And, are there any special criteria for this operation?


texts:
The following question was given in FIITJEE study material:

At first, I thought it should be elimination. But, soon I realized that there is no heating, plus a primary alkyl halide is used. So, "no elimination".
Then, I thought it would proceed through $\ce{S_N2}$, and hence (B) should be correct, as it involves concerted mech.. But, again I was wrong. Why is it so?

The correct answer given is:

 (D)


texts: Differentiating between Elementary and Non Elementary reaction

texts: Is it possible to tell just by looking(reaction's equation) that whether a given is reaction is elementary or non elementary ?


texts: How do I solve questions pertaining to rate of disappearance and appearance?

texts:
In a reversible reaction $\ce{2NO2 <=>[$k_1$][$k_2$] N2O4}$, the rate of disappearance of $\ce{NO2}$ is equal to:

  $2\frac{k_1}{k_2}\ce{[NO2]}^2$
  $2k_1\ce{[NO2]}^2-2k_2\ce{[N2O4]}$
  $2k_1\ce{[NO2]}^2-k_2\ce{[N2O4]}$
  $(2k_1-k_2)\ce{[NO2]}$

The answer, they say, is (2). I just don't understand how they got it. I find it difficult to solve these questions. Is the rate of disappearance the derivative of the concentration of the reactant divided by its coefficient in the reaction, or is it simply the derivative?

If someone could help me with the solution, it would be great. And please, don't assume I'm just picking up a random question from a book and asking it for fun without actually trying to do it. I have worked at it and I don't understand what to do.


texts: Reduction and oxidation in organic chemistry

texts:
What is the meaning of reduction and oxidation in organic chemistry?
In general chemistry I learned an OIL RIG mnemonic, i.e. oxidation is loss and reduction is gain (of electrons).

But what do we say about their usage in organic chemistry? I have seen their usage a lot of times in the form of reducing agents and oxidizing agents but never really understood it. What really makes a substance a good oxidizing or a good reducing agent?


texts:
I was carrying out an experiment into the effect of temperature changes on the standard potential of a cell.

$$\ce{Zn(s) +2Fe^{3+}->Zn^{2+} +2Fe^{2+}}$$
I used equi-molar concentrations of $\ce{Fe(CN)_6^{4-}}$and $\ce{Fe(CN)_6^{3-}}$. Thus the Nernst equation

$$\mathrm{E^{\theta}_{cell}=E_{cell}-{\frac{RT}{nF}}*ln1}$$ reduces to $$\mathrm{E^{\theta}_{cell}=E_{cell}}$$

We plotted our $\mathrm{E^{\theta}_{cell}}$ values versus T and noticed that our $\mathrm{E^{\theta}_{cell}}$ values were actually increasing with temperature.

I would have expected that these values go down as the concentration of the reactant falls.

I asked my demonstrator and sourced information from different web resources, but can't access a definitive answer.

Any hints even?


texts: Origin of broad CO stretch in infrared spectrum of tricobalt cluster

texts: I'm quite confident that the peaks around $\pu{2000 cm^{-1}}$ are $\ce{CO}$ stretches. But I cannot find any reference on that massive broad stretch following the $\ce{CO}$ stretches. Does it have anything to do with high symmetry?


texts: I am unsure with regards to the specific reason why alkanes are non-polar as I have heard different explanations. My teacher said that it is because, although there is a difference in electronegativity between carbon and hydrogen atoms, the carbon is shielded by the hydrogen atoms from reacting with the external environment and therefore, since only the hydrogen can react, it is non-polar (something along the lines of it is the difference between delta + and delta - ends that actually make a molecule polar). From searching on the internet, however, I have found the explanation that it is because the difference in electronegativity is so small (0.3) that it is non-polar, which makes sense, however it contradicts what my textbook states: That only bonds between elements with equal electronegativity are non-polar. Can someone clear this up for me? Thank you!


texts: How to differentiate the notation of a compounds charge and an anions oxidations state?

texts:
I have had the case a few times. Being given something of this form:

$$\ce{Cr2O7^2-}$$

How do I know whether the $2-$ is referring to the oxidation of the oxygen anion or the charge of the whole compound?


texts:
Quasicrystals are materials that have long-range atomic order but lack the translational symmetry of conventional crystals. All quasicrystalline tilings and packings I have read about thus far, whilst lacking translational symmetry, have rotation axes and reflection planes. I'm wondering if anyone is aware of experimental evidence of quasicrystals which lack reflection symmetry (and thus possess implicit chirality), or can provide a theoretical rationale for why such structures can or cannot exist.

To clarify, a cursory google search turns up a paper interpreting a viral capsid as having chiral quasicrystalline order - Whilst I don't have access to the paper, I specifically exclude this sort of intepretation from consideration as I'm talking about structures with potentially infinite spatial extent, which viruses do not have.


texts: Why don't atoms with expanded valence shells have a formal charge?

texts: I'm working through Chemistry - Principles and Practice, 3rd Edition and I have few complaints so I don't think it's the text. At one point, I was asked to draw the Lewis structure, with formal charge, of SO3. The central sulfur atom has six covalent bonds with the surrounding oxygen atoms. Based on the calculation for formal charge, you'd expect one of +3, but there is none. How am I to know when there is or isn't a formal charge, and why?


texts: How do self-relighting (trick) birthday candles work?

texts:
You may have seen those birthday candles, where, upon blowing them out they smoulder for a bit and then (magically) relight.

How do they work? Why can't regular candles do this (is it possible for a regular candle to relight itself, anyway?)


texts: How can change in entropy be the same for all processes if the entropy production $\sigma$ is present for irreversible processes?

texts:
From the definition of entropy change,
$$S_2-S_1=\left ( \int_{1}^{2} \frac{\delta Q}{T}\right )_{int.rev}$$
From the closed system entropy balance, we have
$$S_2-S_1=\left ( \int_{1}^{2} \frac{\delta Q}{T}\right )_{b}+\sigma $$
where $\sigma$ is the entropy produced within the system, vanishing to zero in the absence of irreversibilities. I don't quite understand how the entropy change between two states is the same for all processes. Is it the case that the entropy transfer in the case of internal irreversibilities present is lower than that of the entropy transfer in an internally reversible process between these same two states, and the entropy production makes up for this difference?


texts: What is the meaning of signs in electrode potentials?

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Question

Suppose you have a cell set up between a copper metal/copper(II) ion electrode and a reference electrode.

Under standard conditions, the emf of this cell was −0.07 V. The standard electrode potential of the copper metal / copper(II) ion electrode is +0.34 V. Hence the standard electrode potential of the reference electrode is:

A: -0.41 V

B: -0.27 V

C: +0.27 V

D: +0.41 V

My attempt:

I was taught this equation: $\mathscr{E} _{cell} = \mathscr{E} _{a} - \mathscr{E} _{b}$

where:

$\mathscr{E} _{a}$ is the emf of the more positive electrode potential

$\mathscr{E} _{b}$ is the emf of the less positive electrode potential

But using this equation, none of the combinations of electrode potentials give -0.07V as the emf.

Thanks


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I have read that the color of colloid depends upon the wavelength of light scattered by the dispersed phase and also in the sense in which the receiver receives the light.
If all of this depends on wavelength scattered and in the sense we see, then what is the actual color of a colloid?


texts: Potential Energy Curve from Hartree-Fock Calculations

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I am currently working on some quantum chemical calculations, in particular looking at dissociation energy curves generated from Hartree-Fock, CI, CCSD and MP2 methods for diatomic molecules. Now, I was always under the impression that in order to get a potential energy surface  (in the Born-Oppenheimer approximation)  one needs the energies for the electronic problem and the nuclear-nuclear interaction:
$$E(R) + V_{\mathrm{NN}}(R) = U(R)$$
Where $E(R)$ is the energy obtained from the solution of the electronic Schrödinger equation, $V_{\mathrm{NN}}(R)$ the internuclear coulomb potential and $U(R)$ the potential energy surface. I have now seen multiple publications and books that draw potential energy curves using only $E(R)$.
So my question: Are these publications/books wrong, or do I have a misunderstanding of how the PES is computed under the BOA?
Example publication: Dutta, A.; Sherrill, C. D. Full configuration interaction potential energy curves for breaking bonds to hydrogen: An assessment of single-reference correlation methods. J. Chem. Phys. 2003, 118 (4), 1610–1619. DOI: 10.1063/1.1531658.


texts: Why do amides react differently with PCl5?

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In a reaction involving $\ce{PCl5}$ and any reactant containing oxygen atom, it generally takes out the oxygen and put chlorine their due to formation of strong bond between phosphorus and oxygen.

But, in case of amides like $\ce{RCONH2}$, when they react with $\ce{PCl5}$, a cyanide is formed. Why?