texts: What reaction happens between glucose and ammonium chloride when drying?

texts:
I have the following observations:

When I put a solution of glucose (80 g/ℓ) and ammonium chloride (20 g/ℓ) in a drying cabinet at 37°C (maybe a bit warmer) a brown substance forms when all (or most) of the water has evaporated.
When I add water to the reaction product, the substance dissolves within minutes (under shaking), but the resulting solution is brownish.
From this I conclude that a reaction happened and the brown colour isn’t just the colour of some salt crystal.
If I perform the same procedure on glucose solution or ammonium chloride solution alone, nothing similar happens, which indicates that it’s not a reaction with the air or the container. PS: If I redissolve the product of drying ammonium chloride alone, the result is acidic (pH of 5 or lower for 1 g/ℓ).
No browning happens if I replace ammonium chloride with sodium chloride, which indicates that chloride is not responsible for the reaction.
The same thing doesn’t happen in the presence of water.
Even when the solution has already been dried to a highly viscous sludge, I still don’t observe any browning.
It only happens in final stage of drying.

My questions are:
What reaction is this, why does it only happen when drying, and is there some way to prevent this, e.g., with a lower temperature?
I ideally want to get a dried residue containing glucose, ammonium, and chloride in my container.
Just filling in the powders doesn’t help, because I cannot do this efficiently and precisely.
What I found so far is this:

Typical browning reactions of sugar (Maillard reaction, caramelisation) require much higher temperatures or additional ingredients.
According to the paper Reactions of Free Sugars with Aqueous Ammonia, some reactions between sugar and ammonia happen at this temperature, but with a low yield and in the presence of water.


texts:
I want to address two exceptions in the trend of ionization energy across the period, that are causing me problems:

Taking the second period as an example :

The two exceptions from the general trend are the ionization energies of B lesser than Be and that of O less than N.
My teacher told me the reason to both was that half filled and fully filled orbitals of N and Be are more stable and hence require more energy to pull off an electron. He also said that this affects only the next element in the period for a change in trend( he never said why though).
This place and my textbook tells me that the reasons are:

1) Be,B :

The electron is to be removed from the 2p orbital in B and the 2s orbital in Be. The 2s orbital penetrates more into the nucleus and hence it is more difficult to remove an electron form Be than  from B.

Question: In that case why doesn't this apply to C? Shouldn't it be easier to remove one of the electrons from C's 2p orbital than Be's 2s orbital just like the B's 2p orbital? And so shouldn't the ionization energy of Be must be more than C too?

2) N,O:

N 1s2 2s2 2px1 2py1 2pz1
  O 1s2 2s2 2px2 2py1 2pz1

The reason I have understood here is that there are two electrons in the 2px orbital of O and because of electron-electron repulsion, it is easier to remove an electron from here as opposed to the 2px orbital of N which had only one electron.

Question: Why doesn't this apply to F?

F 1s2 2s2 2px2 2py2 2pz1

F has paired electrons too like O in the px and py subshells. Wouldn't there be repulsion here too? And hence why isn't it easier to remove electrons from F than is it to from N which doesn't have any paired electrons at all? Why is the ionization energy of F more than N instead?

The same problems can be seen in the next period.I hope they can be sorted out with the same logic that i am missing for this period.

Finally, was what my teacher said just a simplification of everything I found in the link and the textbook? Was he trying to convey the same thing? Or are they two complete different explanations?


texts: How to convert benzamide to benzylamine?

texts:
Question
  Benzamide can be converted to benzylamine using

  A) $\ce{Br2,\ KOH}$
   B) $\ce{PCl5}$
   C) $\ce{LiAlH4}$
   D) $\ce{NaBH4}$

My answer:

Reducing agent is used so C and D options both must be correct but since its single choice answer, I do not know which is more appropriate. Any help?
Also, what does option A and B reagents do to amides?


texts: Finding vendor information programmatically

texts:
I have a large collection of structures (>10,000) that I've gathered from literature searches and I would like to find out which of those can be obtained from vendors.  I know that eMolecules and ChemSpider provide such information, but getting that information for 10,000 structures in daunting.

On eMolecules, I can load a list of SMILES, search the databases, and download the results.  The download process is not very robust, though, and I have to reconstitute a lot of pieces of information.

ChemSpider provides additional information regarding vendors, and I've tried using the ChemSpiPy API, but I consistently get an error from the ChemSpider server.  Obviously something has changed with respect to the server that the API doesn't account for.

Are there other suggestions for where/how I might gather such vendor details for a very large collection of structures?


texts: Predicting the solution with the highest boiling point

texts:
I am facing problem with the following question:

Predict which solution will have the highest boiling point in increasing order?

$1~\%$ solution of $\ce{C6H12O6}$

$1~\%$ solution of $\ce{NaCl}$

$1~\%$ solution of $\ce{ZnSO4}$

$1~\%$ solution of  $\ce{(NH2)2CO}$

I know that more is the van ’t Hoff factor more will be the elevation in boiling point and hence the solution will have more boiling point. Hence 1. should have the lowest boiling point followed by 4. But I am not sure about options 2. and 3.


texts: Does the arrangement of atoms around a chiral carbon matter?

texts: In other words, are these two structures equivalent?


texts: Is cobalt(II) in the hexaamminecobalt(II) complex high spin or low spin?

texts:
I want to determine the  electronic configuration of $\ce{Co}$ in $\ce{[Co(NH3)_6]Cl2}$ with Crystal Field Theory.

I know that since the complex is octahedral, there would be degeneracy breaking and the d-orbitals would undergo splitting to form a $\mathrm{t_{2g}}$ level having $3$ orbitals and an $\mathrm{e_g}$ level above that with $2$ orbitals.

As cobalt is in the $+2$ oxidation state, it would have a $\mathrm{d^7}$ configuration.

Thus, if the complex is high spin, the electronic configuration is $\mathrm{(t_{2g})^5}\ \mathrm{(e_g)^2}$ and $\mathrm{(t_{2g})^6}\ \mathrm{(e_g)^1}$ if it is low spin.

This is where I ran into a problem, what type of complex is this?

Ammonia is generally considered strong field ligand, but it is weaker than say, $\ce{CO}$ as it is a σ only donor.

Wikipedia does not give anything definitive and I get inconclusive/contradictory information elsewhere on the Internet, so can someone please clarify whether the electronic configuration of cobalt in $\ce{[Co(NH3)_6]Cl2}$ is high spin or low spin?


texts:
Show that the limiting fraction of association of a base in water, as
  the concentration of base approaches 0, is $$\alpha=\frac{10^7 K_b}{(1+10^7\times K_\mathrm{b})}.$$

I have tried this problem for a long time and have made little progress. Here is what I have tried:

We know that:

\begin{align}
K_\mathrm{b} &= \frac{\ce{[HB+]}\ce{[OH-]}}{\ce{[B]}}\tag{definition}\\
\ce{[HB+]} + \ce{[H+]} &= \ce{[OH-]} \tag{charge balance}\\
\ce{[H+][OH-]} &= 10^{-14} \tag{$K_\mathrm{w}$ at $\pu{25^o C}$}\\
\text{initial concentration of base added} &= \ce{[B]} + \ce{[HB+]} \tag{mass balance}
\end{align}

I know that the limiting fraction of association is
$$\alpha = \frac{\ce{[HB+]}}{\text{initial concentration of base added}} = \frac{\ce{[OH-]}}{(\ce{[B]} + \ce{[HB+]})},$$
but I'm confused about how to proceed from here. I tried putting $\alpha$ in terms of $\ce{[OH-]}$ to get a cancellation, but that proved difficult. How do I proceed?


texts: Why are nitro compounds with at least one alpha-H soluble in NaOH?

texts:
Are all the nitro-compounds having at least one alpha-$\ce{H}$ soluble in $\ce{NaOH}$? And what does solubility has to do with alpha-$\ce{H}$?

I was reading about tautomerism today and got stuck on this thing. Is it due to its conversion to the enol form? Does the keto form also show this? What could be the possible reasons?


texts: Hydroxyl group to free amine in polyethylene glycol using CDI?

texts:
For converting $\ce{OH}$ of methylated polyethylene glycol. The first step is converting hydroxyl group to imidazole carbamate as an active intermediate. But what about the next step?

If I will add primary amine containing group to form carbamate linkage, how can I convert it to a free amine?

Reference: Zhou, S.; Wang, J.; Wang, G.; Jiang, Z.; Ren, H. An approach to developing high dielectric constant nanocomposites based on polyrotaxane derivative. European Polymer Journal 2017, 90, 312-322. DOI: 10.1016/j.eurpolymj.2017.03.037.


texts:
Is my pipette a blow-out pipette?
I suspect that it is a blow-out pipette, though the double lines aren't rings. My guess is it is a TC blow-out pipette. It's a big 50 mL pipette, longer than my arm.
I wonder, how am I supposed to know? I also have another one with a single dark band on the top.
EDIT: This video explains how blowing out a pipette is actually done.


texts:
Our professor only told us that A is favored, and B is not getting formed. I thought about the resonance structures and saw a contradiction to that what the prof told us. To be honest I think my argument with the resonance structure is not strong enough, because it does not explain the prefered product. Why is structure B disfavored?

@jerepierre: I checked again. You're right! I'm sorry for the wrong re-drawing. Although the above discussed reaction with deprotonation was also dictactical important.

The correct starting material is in fact a alpha,beta-unsaturated ketone which is reduced by Li/NH3!

This is the correct reaction:


texts: Would any alkene possibly aromatize with proper conditions?

texts:
I was reading about 2 specific reactions: polymerisation of alkene and aromatization of alkane (of a sufficient size).
I thought why can't, having a condition that favored both these reactions be created, there exist a chain reaction where an alkene starts polymerizing and when the chain becomes long enough, it aromatizes.

It's just a thought that I had but I can't figure out if it IS possible.


texts: Oxidation states of iron in Roussin's salts

texts:
For preservation of meat, sodium nitrite is usually added and as a result $\ce{NO}$ is then formed. Consequently, $\ce{NO}$ reacts with the sulfur and iron atoms from decomposition of proteins, forming $\ce{[Fe4S3(NO)7]-}.$ X-ray crystallography shows that the complex anion has a structure as shown below:

  a) Blacken all the circles corresponding to iron atoms and add symbols Fe(A),
  Fe(B), Fe(C) and Fe(D) beside the circles in the sequence of top → left → right.

  b) The configuration of 3d electron shell of the iron atoms has been studied with modern structural analysis. Knowing that the mean oxidation number of the
  four iron atoms is $–0.5$, give their configurations of 3d shell, respectively.
  Assume that each iron atom adopt sp hybridization.

  $\ce{[Fe4S3(NO)7]^{–}}$ anion can be reduced and a new complex $\ce{[Fe2S2(NO)4]^{2-}}$ is formed

  c) Give the oxidation state of each iron atom with Arabic numerals.

  d) $\ce{[Fe2S2(NO)4]2-}$ can be converted into $\ce{[Fe2(SCH3)2(NO)4]^{n}}$, a carcinogen. Which of the following three species is added to $\ce{[Fe2S2(NO)4]^{2-}}$ : $\ \ce{CH3+}$,$\ \ce{•CH3}$ or $\ \ce{CH3−}$?

My Attempt

a)

I don't have any real reason to why I chose those 4  atoms. I chose them since they were the 4 biggest atoms in the ring and made sense they would alternate with the sulfur atoms in the ring. Is there a more solid explanation?

b) Firstly, why do the iron atoms have a negative oxidation state, doesn't it 'give' its electrons to the sulfur and nitrogen atoms since it is more electropositive? I look up negative oxidation states of iron and I found out when bonded to carbonyl compounds, the iron atom usually has a negative oxidation state. So is the $\ce{NO}$ ligand in this case acting like $\ce{CO}$?

The answer is Fe(A) has 3d7 configuration while the others have a 3d9 configuration. Could someone please give an explanation for this.

c)

I have drawn what I think is the structure above, but I have the same problem as part b)

d) I have no idea. I am guessing the methyl cation since the iron atom has a negative oxidation state (I am guessing from part c) hence it will more likely react will a cation rather than an anion or radical.


texts:
Ultramarine blue ($\ce{Na2Al2SiO8 + Na2S}$, a sulfide-silicate complex containing sodium and aluminium) is insoluble when mixed in water and gives a blue color appearance to the water solution.
Which chemical (from my understanding, it should be acid) can be used to make the blue color disappear in water (absorb the coloring agent)?

Possibly $\ce{H2SO4}$ will absorb the sodium, releasing $\ce{H2S}$. I want to understand basically

What is the coloring agent (is it sodium only)
Which chemicals can I think about to remove the color (absorption of coloring agents)


texts: Someone has argued that the table sitting in front of us is 'frozen'. I do agree that the table has a freezing point. The table has a melting point, but that is beyond the ignition point and the boiling point is even further beyond that. If an object only exists in one state can you call it frozen? Secondly, I think that there is some disconnect because I was arguing more from a sociological stand point. I think that the definition is more subjective. If I call a wooden bowl frozen, it would hinder the meaning of the sentence from an outsiders stand point. What do you think? Can you say that the table in front of you is frozen?


texts: Modifying a TLC mobile phase in order to increase the RF values

texts:
You are running a TLC using 50% ethyl acetate in hexane and find the resulting $R_f$ values are too low. How would you modify the TLC mobile phase in order to increase the $R_f$ values?
Would the hexane and ethyl acetate be considered the mobile phase/solvent?


texts: How to know which ionic compound have the highest lattice energy without knowing the values of the radii?

texts:
Given two ionic compounds, for instance:

$$\ce{CaS} \quad \mathrm{or} \quad \ce{KCl}$$

What is the procedure to predict which of the two have the highest lattice energy (in absolute value)?

(Suppose that I do not know the values of radii of the atoms but I can only look at the periodic table).

I know that I must look at the ratio

$$\frac{Z_1 Z_2}{r_1 + r_2} \propto E_\text{lattice},$$

where $r_1 + r_2$ is the distance between the two atoms in each molecule of the compound, $Z_1 Z_2$ is the product of atomic numbers of each element in the molecule.

But, for example, in the case above I have both $r_1 + r_2$ and $Z_1 Z_2$ bigger for $\ce{KCl}$ then $\ce{CaS}$, so I cannot say (without knowing the numerical values) if one of the two ratios would be higher.

Am I missing something?


texts: What caused a colour change when I mixed two different dish soaps?

texts:
I recently purchased "organic" dish soap refill made from saponified coconut oil and potassium soap (full ingredient list). Instead of waiting for the old dish soap (Dawn) to be completely finished, I just poured the refill into the bottle.
The refill was a translucent yellow, and Dawn is obviously translucent blue. However, as soon as they made contact with each other, some chemical reaction clearly happened and the whole thing turned into opaque dark brown. The resulting liquid still has cleaning properties but doesn't seem to be equivalent to either of the soaps alone.
I tried to figure out what could have possibly reacted, but couldn't figure it out. Thought I'd try here.


texts: Assigning Peaks and Determining J Values for Mata-Disubstituted Benzene

texts: I need to determine as many J values as I can for 3-methoxybenzaldehyde. The peaks overlap a lot, and I don't see the expected ddd or dt pattern that I would expect for the hydrogen on carbon 6. The HSQC I was given has the clearest peaks for the H NMR, so I attached that. Maybe someone with more NMR experience can help me tease apart the signals?


texts: Empirical formula when given percentages?

texts: A binary compound of lead and oxygen contains $90.66 \% \ce{Pb}$. What is the empirical formula for the compound? How do I use the percentage to get to the normal formula, then how do I change the normal formula to empirical?


texts: When multiple sources give the content of an ingredient my an unqualified percentage, can I safely assume this is by weight? Or; it's not a wart

texts:
I am trying to make a simple scented shampoo and body soap for my own use and for Christmas gifts.
I statr with a base of 32 oz – (a bit under a kg) of a mild commercial castille soap (Dr. Bronner’s Peppermint) to which I have added modest amounts of essential oils ranging from 2 tablespoons (lavender) to a few ml (jasmine  and pine needle) down to a few drops (vetiver, bergamot). Because I have dandruf on my head and psoriasis on my elbows, and because I know both of the other people I am gifting use cosmetics containing exfoliants, I decided to add one percent of salicylic acid to the shampoo. Over-the-counter cosmetics use up to 2 percent, and prescription shampoos are available with up to six percent. This seemed adequately cautious for a first-time emdevor, and assuming thee percentage was by weight, I added a bit under10 gm of powdered salicylic acid to the almost a kg of shampoo.
Here is my question: at least half of the salicylic acid has not gone into solution after considerable agitation. This make me wonder if I am not adding too much salicylic acid because I am measuring the percentage incorrectly. Should I be measuring the shampoo by dry weight? Or reconstituting the salicylic acid somehow before weighing it? Or defining the percentage in molar terms? Or should I be doing something else to encourage solubility (boil it?) or to make it into a suspension or something?
I was hoping to try it out, but I thought I should try to establish that I am not using way too much acid.  A 24 percent solution is sold as wart remover.  I clearly don’t want to apply that on my head.


texts: Is there any difference between a completely filled orbital and an half-filled one?

texts: Is there any reduction in size of the orbital for a half-filled orbital? Is the probability at any point of finding an electron doubled if there are two electrons instead of one? Is there any difference at all? I'm trying to understand the quantum mechanical model. Thank you in advance!


texts: Is a supersaturated solution still a solution?

texts:
Given that a solution must be a homogenous mixture, and having crystallized solids at the bottom of a solution is most definitely not homogenous, can a supersaturated solution still be technically defined as a solution?

On that note, is it possible for a solution to have more solute than solvent and remain in solution form?


texts: How should a triple bond be depicted in skeletal structures?

texts:
Draw the skeletal structure for the following compound:
  $$\ce{HOCH2CH2OCH2C#CCH2CH(CH3)2}$$

I can't figure this out.

I can draw it up until the triple bond. My professor marked off because the triple bond was not drawn correctly.

So, is the triple bond depicted any differently from the other bonds in the molecule? If so, why?


texts: Amino acids: why is charge found by comparing pH and pKa and not pH to pKa + log [A-]/log[H+]?

texts:
I am working on problems such as :

The charges on the side groups at each pH are found by the following rule:

at $\ce{pH < pK_a}$, $\ce{H+}$ on, protonated
at $\ce{pH > pK_a}$, $\ce{H+}$ off, deprotonated
at $\ce{pH = pK_a}$ , neutral

But why can we compare $\mathrm{p}H$ and $\mathrm{p}\ce{Ka}$ directly?
I just started my amino acids topic. In all my acid and base questions we always compared $\mathrm{p}H$ to $\mathrm{p}K_a$ using the Henderson Hasselbalch Equation:
$$\mathrm{p}H =\mathrm{p}K_a +\log \left( \frac{\ce[A^-]}{\ce{[HA]}} \right)$$
So why do we now compare $\mathrm{p}H$ to $\mathrm{p}K_a$  directly?


texts: How long would it take to dissolve someone using fluoroantimonic acid?

texts:
After writing an answer on worldbuilding.SE, I came here to ask a question. How long would it take to dissolve a human body using fluoroantimonic acid?

I understand that since the human body isn't homogenous, it's a bit tough to get the exact calculation, but lets say we create a mannequin using the material in the human body that fluoroantimonic acid takes the longest time to dissolve - how long would it take?


texts: How to determine the reactivity of a set of compounds that may undergo nucleophilic substitution?

texts:
Which of the following compounds is most reactive under $\mathrm{S_N1}$ conditions?

  Arrange the following compounds in order of decreasing rate of $\mathrm{S_N1}$ hydrolysis:

  A. II > III > IV > I
  B. IV > III > II > I
  C. III > IV > II > I
  D. I > II > III > IV

Both these questions are based upon the rate of reactivity of $\mathrm{S_N1}$ reaction.

1) In this I thought the answer should be B because the rate of $\mathrm{S_N1}$ reaction depends on the ease of formation of carbocation. Being more electronegative, the electron density between carbon and chlorine bond is quite shifted towards chlorine, so it should be easier for chlorine to leave, hence forming the carbocation. Options A, B, and C allow the carbocation to be resonance stabilized so D cannot be the answer.

But the answer given is A.

Where am I wrong with this logic? I guess it might be because of more polarizing power of iodine, if it is this, then how are we supposed to figure out which one will be the dominating factor?

2) I think we check this on the basis of carbocation stability as well. Carbocation will be formed as $\ce{Br}$ leaves. Alkyl chain is electron releasing, so it must increase the electron density on the benzene ring which should be better for the stability of carbocation (as there is more electron density on the benzene ring to stabilize the positive charge). Hence the answer should be I > II > III > IV

But the answer is A.

Where am I wrong with my logic in both?


texts: Raman Spectroscopy: How to calculate their constants?

texts:
$^1{\ce{H2}}$ is interrogated with a laser of wavelength lambda = 532 nm and vibrational Stokes transitions are observed at S(0) = 14302.206 cm$^{-1}$, Q(0) = 14638.442 and O(2) = 14992.823 cm$^{-1}$.

Estimate ωe (cm$^{-1}$)
Determine B1 (cm$^{-1}$)

I know the band origin = Q(0). I also know from rovibrational spectra that

$ ω_0 = ω_e -2ω_eX_e$.

Could someone please help me answer this question and explain?

If there are any additional resources I could read on these topics that would be great too.


texts: Acidity of aldehydes and ketones and enolate formation

texts:
In most academic courses you'd learn that aldehydes are more acidic (lower $\text{p}K_\text{a}$) than ketones due to the lower electron donating effect of the proton compared to the alkyl group of the ketone.

However, when talking about condensations, for example, it's not a weird choice to form a ketone enol over an aldehyde enol on the basis of "thermodynamic stability due to a more substituted alkene under thermodynamic control". Yet, $\text{p}K_\text{a}$ is the measurement of such stability, and thermodynamically the aldehyde enol is more stable. Adding to this, a following argument is that "aldehydes react much quicker towards nucleophilic attack than ketones". I agree with this, but weren't we just discussing thermodynamic control?

The questions are then:

Is it valid to use the "more substituted alkene" to argue a step on a mechanism under claims of thermodynamic control?
Can this type of argument be coupled with a kinetic one like the example provided as well? I.e. is it valid to mix thermodynamic and kinetic arguments one in the same? (e.g. this intermediate forms because it's more thermodynamically favored, and the next one forms because it is kinetically favored).

(I realize question 2 may be broader than this, but I'm trying to keep this in the sense of mixed aldol condensations)


texts:
I am really confused about the rate law. From my understanding, the rate law gives an equation that tells us the rate of the disappearance of the reactants. So, for example, the rate law of the reaction $\ce{2 NO + O2 -> 2 NO2}$ is as follows
$$\text{rate of disappearance of reactants} = k \, [\ce{NO}]^2 [\ce{O2}]$$
My biggest confusion stems from the fact that the rate law gives one uniform rate for the disappearance of all the reactants, which makes no sense to me. For every $\ce{O2}$ used, two $\ce{NO}$ are used, so how can they be disappearing at the same rate?
Hopefully, it makes sense where I am coming from, and I would appreciate any help trying to clarify this for me.


texts: Calculating the pH of a dilluted aqueous KOH solution

texts:
Calculate $\mathrm{p}\ce{H}$ of an aqueous solution of $0.01\:\mathrm{nM}~\ce{KOH}$ in water.

I think that water also has $\ce{OH-}$ ions in concentration of $10^{-7}\:\mathrm{M}$ (since $\mathrm{p}\ce{H}=7$)

So the total concentration of $\ce{OH-}$ after mixing the solution with water would be:

$0.01\:\mathrm{nM} + 10^{-7}\:\mathrm{M} = 10^{-11}\:\mathrm{M} + 10^{-7}\:\mathrm{M} \implies 1.0001 \times 10^{-7}\:\mathrm{M}$

and given that $\mathrm{pH} = 14 - \mathrm{p}\ce{OH}$

$\implies 14 - \log(1.0001\times10^{-7})$

$\implies \mathrm{pH} \approx 7$

Does this make sense?


texts:
I have worked with a somewhat long reaction sequence and got stuck on this last step. Im not sure if the entire sequence is even correct but this is what i came up with. Is this a possible reaction, if so, what is the product?
Thanks


texts: Why must NaOH be kept dry during storage?

texts: Why should the Erlenmeyer flask used to store $\ce{NaOH}$ be dry? Why should it be kept covered at all times?


texts: Degenerate semiconductors /N type dopants/Low fermi level

texts: In extrinsic semiconductors the donor level of some N type dopants is lower in energy than some other dopants . For example as we move from the V  to the VIII group if we draw the band diagram the fermi level gets lower and lower. I am interested to know if by denegerately doping the intrinsic semiconductor with 'low fermi level' N type dopants what will happen.Will a new impurity band form inside the band without any band tailing?And which interesting new properties could this have?


texts: What is Polymer Environmental Resin (PER)?

texts:
I'm no chemist and I probably wouldn't understand any technical answer but...

I'm investigating the environmental impacts of various materials as compared to PVC and this is one that crops up regularly as a more environmental alternative.

Unfortunately there does not seem to be any authoritative information on the web concerning this material.

I'm beginning to think that this is a green-washing propaganda move by the phthalate/heavy metal free PVC industry as a move avoid mentioning PVC in product advertising.

Anyway I would welcome any information on what exactly PER is and what it is made from.

Thank you.


texts:
So I have a question concerning a reaction mechanism for the reaction below.

I know for certain that I get the alfa anomer, but I can't explain it. When I draw out the mechanism it doesn't make sense to me.

I think what throws me off is the NGP from the Ac- group since it would 'force' the beta configuration. I was then considering anomerization of the beta anomer to the alpha anomer, but when I look at mechanisms for this I can't see how it would be possible when I have a bromide on C-1.

I was then wondering if the endocyclic oxygen gets protonated in the first step rather than the exocyclic oxygen in the mechanism I drew, but that would lead to NGP again because we get an oxocarbenium ion.


texts: Piece of equipment similar to syringe for gas collection

texts:
I'm looking for the name of a piece of equipment similar to a syringe. The only difference is that this item is made entirely from glass. The purpose of this equipment is to collect gases.

Here is a photo of two of these pieces of equipment connected to a gas-washing bottle:


texts: I have heard many times that when there is the “right balance” of protons and neutrons the atom will be stable, and therefore it will decay to achieve this stability. But what about this supposed balance of protons and neutrons makes it stable? Does it have to do with quarks? Density? I am quite curious as to what causes this.


texts: IUPAC nomenclature of cycloalkadienes with substituents and alkenes on the same carbons

texts:
Consider the following organic compounds:

Compound $(1)$ has two double bonds, which I'll label $C1$ and $C4$ such that the methyl group is attached to $C1$ and thereby assign lowest numbers to all functional groups and substituents. Officially its name is 1-methylcyclohexa-1,4-diene.
Generally we try to give just enough information to be able to reconstruct the original compound, but not too much. With that in mind, I feel that compound $(1)$ should be named simply 1-methylcyclohexa-4-diene:

Since it ends in -diene, it's understood that there are two double bonds.
Since it ends in -4-diene, it's understood that one of them begins at $C4$.

If the second double bond were located after $C4$, the numbering is backwards; instead of, say, -cyclohexa-4,6-diene, it should've been named -cyclohexa-1,3-diene.
If the second double bond were located at $C2$ or $C3$, then priority was given to the methyl substituent over the alkene functional groups. Rather than calling it 1-methylcyclohexa-2,4-diene, it should've been named 5-methylcyclohexa-1,3-diene.
Therefore, the only option left is for the second double bond to be at $C1$, and therefore specifying 1-methylcyclohexa-1,4-diene is extraneous.

Following a similar line of thought, compound $(2)$ ought to be named just 1-methylcyclohexa-3-diene, rather than its proper name of 1-methylcyclohexa-1,3-diene.
Taking this logic to an extreme, the third compound should be named 1,4-dimethylcyclohexadiene, instead of its proper name of 1,4-dimethylcyclohexa-1,4-diene, because the same logic used above to determine that the second double bond is located at $C1$ should be sufficient to determine the locations of both double bonds in this case, where they both have substituents!
Why in all of these cases, and others like them, do we specify both locants of the alkenes, when one (for compounds $(1)$ and $(2)$) or none (for compound $(3)$) is sufficient?


texts: Why is [1.1.1] propellane more stable than other small members in the propellane family even though it seems to be under the greatest strain?  What makes a small propellanes stable, or in general, any propellane stable?


texts: Coarse-grained force field for ion–water interactions

texts: I want to simulate, at a very coarse grained level, the interaction of water molecules with metal ions, specifically Calcium and Potassium. Is there a standard force field for this. I was told to use to the Martini potential but it doesn't seem to have metal ions...


texts: Why does potential chemical energy decrease with increasing oxidation of carbon?

texts:
I saw an interesting spectrum in my biology class the other day. On the left end was methane - the least oxidized form of carbon - and the most energetic form of carbon (at least relative to what else was on the slide). On the right end was carbon dioxide - the most oxidized form of carbon - and the form with the lowest energy.

Now, I do agree with the slide - we can combust methane but we can't combust carbon dioxide - at least I don't think we can.

However, is there an intuitive explanation of why increasing oxidation state correlates with lower potential energy, at least for carbon?

Does increasing oxidation state correlate with lower potential energy for all elements?

Why does it seem that oxygen forms rather strong bonds with other elements in many cases?


texts: How does a lower pH change the alcohol concentration of wine?

texts: I have been told it that when the pH of wine is lowered the alcohol concentration will decrease because of Le Chatelier's Principle. Which states; if a  equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change. How can I best expand on this?


texts: What gas has the highest refractive index?

texts:
Coming from this answer on the Worldbuilding stack, I'm trying to find a gas with a high refractive index in the visible light wavelengths. The highest index on this site, is chlorine at 1.000773. Is this the highest a gas can be? Or is there a fundamental limit on the refractive index of a gas?

As a note, I am not looking for the densest gas or the densest inert gas. Density does not seem to be correlated with refractive index in this case, as chlorine is not especially dense and the very dense perfluorobutane is not especially refractive.


texts: Why is cytosine far more vulnerable to hydrolytic deamination than both adenosine and guanosine? Here's the source for the claim (the half-life is 340 years at 298 K, which is much smaller than that of adenosine and guanosine).


texts: Can artificial sea water be prepared by mixing sea salt with water?

texts:
I am looking for ways to easily prepare artificial sea water. The chemical composition doesn't have to exactly match that of natural sea water. On-line I can find recipes to prepare sea water. But I was wondering, can I just buy natural sea salt and dissolve it in fresh water (Until I get the required salinity ).

The commercial shrimp farms in my region, that use natural sea water cause enormous environmental damage. That is the primary motivation behind my interest in artificial sea water. I want to explore if artificial sea water can be a eco-friendly sustainable alternative.

My intention is not to breed shrimp, but just to grow the shrimp that I get from hatcheries. And yes, I am planning to get the help of people with relevant expertise in this. I just want to gain some prior knowledge and experience before I go for their help.

Some of my present concerns are similar to those of oceanarium though on a much much smaller scale :-) Like them I also want to prepare sea water, which I can control to my exact needs. Locally we get these "raw sea salt" used for industrial purposes, which are claimed to be very similar to natural salts found in sea. They do not contain iodine, caking agents or any other additives etc. I am guessing probably the sea salts that oceanarium imports might be same as these (probably of much better quality).


texts: Oil refinery - How many plates are needed for a 10 degrees difference in temperature?

texts:
I am having some trouble going about this question. My first thought is to set up an ASTM separation equation to figure out the difference, but I do not know how to incorporate the reflux ratio which is 0.5.

ASTM: TBP 50% --> 550 (heavy oil)-300(light oil)= 250 degrees

reflux ratio is 0.5. Do I multiply the ratio by number of plates and then take $\frac{\pu{250 ^\circ C}}{\text{reflux}\times \text{number of plates}}$ to get the answer of 10 degrees?


texts: Best way to raise pH without alkali metal?

texts: I have a process that requires pH~14-14.5 to work. I’ve been achieving this with concentrated NaOH solutions, but the Na cations are later causing side reactions which are detrimental.  Is there any organic base/non-alkali base that has the solubility in water and pKa to reach these pH values?


texts: Why are pi bonds only formed when sigma bonds are formed?

texts: While studying about bonding there was one statement that "pi bonds can only be formed only with sigma bonds" as we know that in double bond there is 1 sigma bond and 1 pi bond but then one question arises: Why is a pi bond formed only when a sigma bond is formed? Is it possible to form a pi bond without any formation of a sigma bond?


texts: Would the mixture of vinegar and baking soda make a cleaning agent?

texts:
I've seen it suggested countless times that combining vinegar and baking soda is a great home cleaning solution, but this always seemed like nonsense to me.

I recognize that baking soda, a base, can eat away at certain kinds of grime and that vinegar, an acid, can operate similarly on different kinds of grime.

Mixed together, of course, the two create a neat foaming reaction and I think this is where the alleged myth would originate - people see the violent foaming and assume cleaning is occurring.

Isn't it true that the two are primarily reacting with each other and yielding only a relatively inert and neutralized sludge?  That the mix reacts with any grime less than they would if both were applied in isolation against the grime?  I assume that the only plausible benefit from this mix would be in any pockets of non-neutralized components floating on the foam and physically reaching new areas of grime that the individual volumes would not cover.

But I guess there could be more to cleaning effectiveness besides pH!

Am I right or are they?


texts: Can halogens exist in their elemental state in nature?

texts:
Question 7 from the 2015 Australian Chemistry Olympiad was:

Which list below gives non-metals that can be found in their elemental form in nature?
(a) neon, phosphorus, fluorine
(b) helium, hydrogen, iodine
(c) helium, carbon, fluorine
(d) nitrogen, chlorine, sulfur
(e) oxygen, chlorine, phosphorus

I was somewhat confused when all the options included reactive elements such as sulfur, phosphorus and the halogens. I know neon is a noble gas and is present in minute quantities in the atmosphere, and nitrogen and oxygen gases are present as diatomics.
However, where are hydrogen, phosphorus, sulfur, fluorine, chlorine and iodine found in their elemental forms in nature? (Answer is B)


texts: Why do people still use the mole (unit) in chemistry?

texts:
I know that the mole is widely used in chemistry instead of units of mass or volume as a convenient way to express amounts of reactants or of products of chemical reactions.

I'm wondering why people in chemistry still excessively use it for their measurement? To be backward-compatible and consistent with traditional textbooks? Why they don't simply express their quantity measurement per atom, per unit volume, per molecule or etc.?


texts: What does "a metallic oxide has 40 % oxygen" mean?

texts:
Question
  If a metallic oxide has $40\,\%$ oxygen, find the equivalent weight of
  the metal.

This amounts to finding the atomic weight of the metal and the charge on the cation (in effect identifying the metal itself).

I didn't know how to do this, so I looked up the solution. It goes as follows.

  Solution
  Assume the oxide has the formula $\ce{MO}$. Let the atomic weight of $\ce{M}$ be $x$
  Then
  $$\frac{16}{x + 16} = \frac{40}{100}$$
  Simplifying and solving for $x$ yields
  $$x = 24$$
  Thus the metal is magnesium and the equivalent weight is $12$.

My problem is, how can we assume that the metallic oxide has the formula $\ce{MO}$? For all we know, the metallic oxide may be $\ce{M2O}$ or $\ce{M2O3}$. In fact, if we assume the latter formula we get

$$\frac{48}{2x + 48} = \frac{40}{100}$$

giving

$$x = 72$$

which I believe is Hafnium.


texts:
The above are two compounds.

The objective is to find if the compounds are identical/enantiomers/diastereomers

I can see a plane of symmetry if we keep the $\ce{H-C-CH3}$ in the plane. So, concluding it as identical looks great.
but, if so, how can one transform the first compound to the second?

Applying, CIP rules, we might invalidate the P.O.S. The solution given for this question is "identical".
Update:(attempt)
I have somehow manipulated the bonds such that I can prove the identity. Even though it is extremely-sterically hindered as indicated in the comments section (Now moved to chat). The forceful manipulations are done keeping in mind, not to break any bonds and only .

However this again proves that the molecules are not identical.
Now, since it is proposed that these molecules are different, can I get a lab or computer synthesized version of both molecules? Upon many search attempts, I could get this document which discusses about the same cyclohexene ring but Deuterium instead of the $\ce{CH3}$ at the bridge head and substituted oxygen ions.


texts:
I've noticed that adding a chunk of ice cream to soda makes the soda fizz slightly near the soda-ice cream interface. I thought it was a physical effect due to the temperature, but adding ice has no effect.

It still can be a physical effect due to solubility, or it may be a chemical effect.

I'd like to know which it is, and the details of the mechanism.


texts: Is steric inhibition of resonance or steric inhibition of protonation dominant in o-toluidine?

texts:
I wish to know which effect out of steric inhibition of resonance (SIR) or steric inhibition of protonation (SIP) is dominant over the other when comparing basicities of o-toluidine and aniline:

Case 1, using only SIR effect
We see that due the bulky methyl present on o-toluidine there is inhibition of resonance which increases the availability of nitrogen's lone pair. Hence, we can say o-toluidine is more basic than aniline (as nitrogen's lone pairs are in resonance with benzene).

Case 2, using only SIP effect
If we consider that methyl's bulkiness shields the lone pair of nitrogen from protonation in o-toluidine and no such inhibition or shielding happens in aniline, we can conclude that aniline is more basic than o-toluidine.

Both these cases are contradictory. Can anyone please resolve the discrepancy?


texts:
The pKa of vinegar is 4.76. If I know the  pH of the vinegar, what would be the formula for determining the percentage acid base on the relationship between pH, pKa and concentration? Can you show the formula so that I only need to plug in the ph?

I am not a chemistry student and I have not done these kinds of calculations. I am searching for a convenient way for farmers in developing countries to quickly approximate the strength of vinegar. The final test would be done in a lab but I need a way for them to test vinegar other than titration because titration can seem more like witchcraft than science to the uninitiated.


texts: Electrons jumping from 1 water molecule to another

texts:
Electrons can be anywhere in the universe and where they are is random.

But they are still discrete particles and thus it takes energy for electrons to move.

Is it possible for an electron to jump from 1 water molecule to another causing $\ce{H2O^+}$ and $\ce{H2O^-}$ to form?


texts: Why is my NaCl solution seemingly saturated, when I followed the recipe for an isotonic solution?

texts:
I prepared an isotonic solution of table salt in water following this recipe: 1 leveled coffee spoon of salt in 0,5L of water.

9g/L would be an isotonic solution, a leveled coffee spoon is commonly given as 5g - close enough. I use water from the tap, which was freshly boiled in a water cooker. The water is not chlorinated, I don't know the hardness.

However, even given hours of time, a significant amount of salt doesn't go into solution - visible as turbidity/precipitation. How can this be?

I need the solution to flush my child's nose, so I don't want to use too much salt.


texts: I know that electrical work or surface tension work are examples of non expansion work but is there an example of a system where expansion and non expansion work are taking place simultaneously.


texts: How can you simulate the effect of a solvent on a polymer in an MD simulation?

texts:
I'm doing a molecular dynamics simulation of polymer melts and I want to include the effect of a good/bad solvent on the melt. How can this be done?

My simulation models polymers using a bead-spring model and the interactions forces are Lennard-Jones for pair interactions and FENE for bonding forces.

Edit:

FENE stands for Finite Extensible Nonlinear Elastic. It's a log based elastic force.
The potential function used, Lennard Jones + FENE is described here (http://lammps.sandia.gov/doc/bond_fene.html)


texts: How does Polytetrafluoroethylene (Teflon) differ from Polyvinylidene fluoride (PVDF) as a protein binding membrane material?

texts:
PTFE and PVDF (durapore) are both used in protein binding filter membranes (Millipore specifically). Chemically speaking the two polymers differ quite significantly due to the additional fluorides and molecular weight. Their protein-binding properties also differ. I'm curious about how the chemical differences affect their properties as a membrane material.
From what I understand, the durability between the two is quite different. The PTFE membranes are used for the filtration of organic solvents where as the PVDF membranes are generally for low protein binding. Furthermore the PTFE membranes typically require a polyethylene support.
I don't believe that the degree of polymerization or the architecture; if we were dealing with a copolymer I expect differently. Based on my molecular intuition, I would imagine that this is completely based on the chemistry of repeat unit.
My question concerns a few things. What makes the PTFE a better solvent resistant polymer? The other is how does the reduced number of fluroides result in reduced protein binding?

Teflon/PTFE

PVDF


texts: Why do negative oxidation states not extend to -8?

texts:
There are oxidation states from -4 to +8

Why do the negative oxidation states not go all the way down to -8? I mean if an atom is hypervalent meaning that it can have more than an octet than that means it can have potentially 8 bonds(counting a double bond as 2 bonds and a triple bond as 3 bonds respectively) to other atoms more electronegative than itself and thus Xenon can have a +8 oxidation state and some metals can as well.

Doesn't that also mean that a hypervalent atom can have 8 bonds to other atoms less electronegative than itself and thus have a -8 oxidation state?


texts: Process parameters of typical chemical processes

texts:
I am researching to opportunity of heat recuperation in the chemical industry be means of high temperature heat pumps. However, I am having some trouble with finding suitable applications. I would like to find overviews of processes (e.g. drying, distillation, thermoforming...) that clearly indicate the heat demand of the process with the corresponding temperature at each state. I also need the temperatures and amount of heat released by cooling processes or waste heat sources (the heat pump will transfer this heat to the heat demanding process).
I searched a lot in literature but I found few suitable cases. Does anyone happen to know about certain papers or websites where I can find typical temperature and heat demand/released values of chemical processes ?
A nice example is illustrated in this figure


texts: How to derive the total number of molecular orbitals based on the given number of atomic orbitals?

texts:
If four orbitals on one atom overlap with four orbitals on another atom, how many molecular orbitals will form?

Why are there eight molecular orbitals and not four? Is not, in molecular orbital theory, each atom's orbital overlaps with another atom's orbital to form a bond?


texts: With there being many particles reacting together forming different shapes of molecules, is there even a slight possibility of some cyclo or benzene miraculously forming into a chain?


texts: Reaction of glucose with 2,4-dinitrophenylhydrazine (DNPH)

texts:
In its open-chain form, glucose possesses an aldehyde group; however, glucose does not test positive with 2,4-dinitrophenylhydrazine (which typically forms a yellow/orange/red precipitate with carbonyl compounds).

Why is this so? Is this a reflection of the cyclic hemiacetal form (where the aldehyde group is not present)?

Both forms are in equilibrium so I'd expect it to give a positive test.

Consider also that glucose gives a positive test in both the Tollens' and Benedict's test. While it is true that less than one in hundred exists in the aqueous solution as the cyclic form, this is not sufficient to explain why it does not give a positive test with 2,4-dinitrophenylhydrazine but yet gives a positive test in Tollens' test and also in Benedict's test.


texts:
As known, work done on the system is: $$\mathrm{d}W = -P_{\text{ex}}\mathrm{d}V $$
However, I have some ambiguity about this equation:

Why is there $P_{\text{ex}}$? Pressure of a gas contained in a cylinder is by definition the force that gas exerts on a piston divided by a area of a piston. But, by the Newton's third law piston exerts the same force on a gas, and so, why is the infinitesimal work not $\mathrm{d}W = -P\mathrm{d}V$?
Some can argue, that we use whatever pressure the thing doing work is pushing against. But I don't accept it. It would be correct if I regarded a gas and a piston as a one system. However, system of interest is only a gas, on which a piston exerts the force with the same magnitude as a gas exerts on a piston, which is $P_{\text{gas}}$.

My calculations:

$$ m\frac{\mathrm dv}{\mathrm d t} = F_{\text{ext}} - F_{\text{gas}}=S(P_{\text{ext}}-P_{\text{gas}}) = S\bigg(P_{\text{ext}} - \frac{nRT}{V_\mathrm{i}-Sx} \bigg)$$
$$ mv\frac{\mathrm d v }{\mathrm dx} = S\bigg(P_{\text{ext}} - \frac{nRT}{V_i - Sx}\bigg)$$
After intergration:
$$ \frac{mv^2}{2} = \int_0^x{SP_{\text{ext}}\mathrm dx} - \int_0^x{\frac{SnRT \mathrm  dx}{V_i - Sx} } = P_{\text{ext}}\Delta V - nRT\ln\bigg(\frac{V_\mathrm{i}}{V_\mathrm{f}}\bigg) $$
Rearrange, we get:
$$ P_{\text{ext}}\Delta V = W = \frac{mv^2}{2} + nRT\ln\bigg(\frac{V_\mathrm{i}}{V_\mathrm{f}}\bigg)$$
There, on the right side, first term is just an energy gain of a piston. The second term is familiar, it's work on the system in reversible process.

So work done on the system is the same as it would be if process was reversible. Why then infinitesimal work is $\mathrm d W = P_{\text{ext}}\mathrm d V$ and not just $\mathrm d W = P_{\text{gas}}\mathrm d V$ ?


texts: Predict melting point of water CaCl2 solution

texts:
I'm doing a science project for my school. I experimentally measured the melting point of water-salt solutions, and I want to compare my results to theoretical melting points, but I encountered a problem.

I used this equation to calculate the melting point depression: $\Delta T = b \cdot i \cdot K_\mathrm{f}$. I also compared my data to a phase diagram. I expected my measured melting point would be on the liquid line. But these two methods give me a different prediction. A phase diagram tells me that $\ce{CaCl2}$ would be much more effective at lowering the freezing point of water while the above equation tells me otherwise.

Here is a comparison: Purple indicates the melting point calculated with the equation. The black line is the liquid line on the phase diagram.

Which method is correct and why is there such a big difference?

(I didn't encounter this problem with $\ce{NaCl}$ solutions, the two methods gave more or less the same predictions)

EDIT: my math was wrong on the graph i posted, here is the corrected graph:


texts: Different behavior of bromine radical with alkenes

texts:
Let's assume we have propene and it's undergoing two different reactions: a Kharasch reaction and allylic substitution reaction.

In both reaction bromine radicals are formed, and the attacking particle is definitely bromine radical, but in one case it goes to the double bond and addition happens, in the other - it breaks C-H bond, making an allylic radical.

Why in these two similar reaction, where the most "powerful" piece is the Br radical, such different products are formed?

My guess is that even if an allylic radical is formed in the case of using HBr and peroxide, the first molecule it meets is HBr, which makes H add to the radical and frees the Br radical again, so no effective interaction happens in summary. And in the case of allylic bromination the Br radical cleaves the C-H bond, since it is like less stable in the allylic position, and the next molecule this radical meets is either NBS or Br2, depending on the reagent.


texts: Dynamic viscosity of gas mixture (appropriate estimation)

texts:
What estimation of the dynamic viscosity $\eta = f(T)$ $([\eta] = \pu{Pa·s})$ of the gas mixture components would you recommend during adsorption at a low temperature, approx. $\pu{293 K}$ to $\pu{333 K},$ and a relatively low pressure?
Gas mixture contains $\ce{N2}$ (the major component), $\ce{CO2}$ and $\ce{H2O}$ in the form of water vapor.
I assume the gas mixture to be ideal.
About a year ago, I use to calculate the dynamic viscosity using Lennard–Jones coefficients for a slightly different conditions if I recall correctly. However, I cannot find my calculations, hence I wanted to check whether using these coefficients would be relevant for such case.


texts: what is the white fuzz left behind on basement floor after puddle evaporated

texts:
My basement is quite dry (knock on wood!).  Recently I brought into the basement for the winter a table from outside.  The table had some ice stuck to it which I couldn't remove, so I simply let it melt on the floor of the basement.  After the puddle that formed evaporated, an interesting artifact was left behind along the the perimeter of the puddle.  It's a raised white line of fuzzy material.

Here's the puddle's perimeter

And here's a close-up of the line that's left behind with a clothespin for scale

Is this efflorescence?  I did some googling, and this is what seems most likely, but I don't know much about chemistry and thought I would ask those who would actually know.  Is it something else?

Thanks.


texts: What chemical reaction happens on worn out metal handles?

texts: I randomly came across a picture of this. It's the comparison between right handed and left handed people. As more people use the door handle, the metal becomes more faded and turns gold color. What is this gold color underneath and why does friction between your fingers and the door handle cause this reaction?


texts: I left a bottle of water in the fridge for the past three months. I took it out today. There was a block of ice in it. How?

texts:
How is this even possible?

I know my fridge is not freezing items. The bottle was sitting at the back and I totally forgot about it. I went to empty it and heard a clank and noticed there was ice in it. How does this make any sense? I don't think that the fridge is disproportionately cooling some regions to below zero. And if so, why would the bottle have a mix of that block of ice and water in it then?


texts:
Why H$_2$Te is a good reducing agent than H$_2$O .

I think it should be opposite as in water , oxygen has only tendency to release electrons .


texts: Why does oxygen have less negative electron gain enthalpy than sulphur?

texts:
Oxygen has less negative electron gain enthalpy than sulphur.

This statement is given in my book with a short reason:

  due to compact size of oxygen

I'm unable to understand why. I would appreciate any worthy explanation for this.


texts: Sodium Sulfate or Sodium Carbonate for electrolysis in water

texts:
I am not a chemist but I have a question regarding electrolytes in electrolysis.
I have done a lot of reading but cannot find the answer I'm looking for regarding Sodium Sulfate (or Sulfide)
I intend to clean a film off a Stainless Steel plate, so that will be my cathode.
For my Anode I will be using a Platinum coated Titanium plate.
At a small scale I have been using Sodium Carbonate (Na2CO3) and it has worked fine, however I intend to scale it up to ~1m^2 plates for the Anode and Cathode, as well as 150A @ 15v DC for ~3min in Deionised water with many repeats, so temperature rise of the water should also be accounted for.
I would like to make this as safe/clean as possible and am considering switching out the electrolyte at this stage to something more stable. I have read that Sodium Carbonate can precipitate directly onto the electrodes at high currents. I believe this is not an issue with Sodium Hydroxide but want to avoid that for obvious reasons. I have stumbled upon Sodium Sulfate as an alternative but very little information on its breakdown and potential pollutants. Is there any other that I am missing/suggestions?
I will be using a fume hood, however Sodium Chloride is definitely not an option.
Thanks for your time,
Tea
Edit:
So I have done some reading and have mostly worked out the half equations of Sodium Sulfate (Na2SO4):
Cathode:
(2)H+ + (2)e- -> H2(g)
Anode:
(2)O2- -> O2(g) + (4)e-
Remaining in aqueous solution:
NaOH (aq) + S (?)
As an update then, can I ask what, if anything, happens to the NaOH and Sulfur?
Also, what form will the Sulfur remain in? I assume it will try to re-bond with oxygen, which will be abundant in the system? Will either be outgassed?
Assuming the NaOH is constantly building up, at what point does it become overwhelming in the system and need to be removed?
Thanks so much for reading this far.
tea


texts: Specific Heats for Non-Constant Processes

texts:
Why can the specific heat at constant Pressure ($C_p$) be used to calculate the change in enthalpy as $\text{d}H = C_p\text{d}T\newcommand{\d}{\text{d}}$ for processes that are not even at constant pressure?
I have $\d H = C_p\d T + V\d p$. Why do we neglect the $V\d p$ term? For gases, $V$ the specific volume, can be very large, so an increase in pressure could have a non-negligible effect on the enthalpy. Is it so? Or not?


texts:
In the reaction of $\ce{LiAlH4}$ with carboxylic acids, deprotonation is followed by a step in which $\ce{O-AlH2-}$ acts as a leaving group. The mechanism is given here in this answer.
$\ce{LiAlH4}$ does not, however, reduce alcohols. Why doesn't a similar reaction occur with alcohols - deprotonation, followed by substitution by a hydride ion and removal of $\ce{O-AlH2-}$?


texts: Is tea powder better dissolved when put in hot water?

texts:
I usually make tea by adding two spoons of tea powder to water at room temp. and start to heat it. My friend said it will be better to add the powder once the water starts boiling. She said that it will dissolve tea more easily because of the sudden temperature difference experienced by tea powder.

Does it make a difference? Why?


texts: Would magnesium and calcium hydroxide undergo a single replacement reaction?

texts:
Can calcium hydroxide react with magnesium (if given sufficient activation energy) to produce magnesium hydroxide and calcium, in the same way that NaOH + $\ce{Mg} \ce{->} \ce{Mg(OH)2} + \ce{Na}$ ?

Or, is calcium's electronegativity (or some other factor) prohibitive of this?


texts: Do molecules containing only carbon exist?

texts:
Why doesn't carbon form bonds with itself to form a molecule? Carbon shows the property of catenation, so why doesn't it form a cyclic molecule such as:
 C = C
 ‖   ‖
 C = C


texts: Mechanism for the chlorination of Fluorene with NCS?

texts: From literature, it was described that fluorene can react with NCS and conc. HCl to produce the 2,7-diCl derivative. Please help me understand the mechanism.


texts: What would happen if I combined this polymer and this metal (assuming I can)

texts:
So let me explain, I recently found out about a material called sorbothane (which is a polymer). Now, sorbothane is special because not only does it highly efficiently absorb shock, but also highly absorbs vibration.

However, when it does this, it temporarily loses its shape, so I was wondering, what would happen if I combined it with a strong yet light metal like titanium? (Note: I am 17 and don’t know a whole lot about chemistry.)


texts:
How are compounds which have a bond between an oxygen atom and a halogen atom named according to IUPAC rules? For example this compound:

I looked in many sites, but couldn't find how such compounds are named.
Also what is their seniority compared to alcohols, esters, ketones, and carboxylic acids? Or are they always a prefix?


texts: Oscillation of particle in harmonic oscillator

texts:
In harmonic oscillator, as vibration quantum number increases then does the distance of oscillation of particle from the mean position where there is minimum potential energy increases?
If yes, then the expression of potential energy $(kx^2/2)$ which we derived from Taylor expansion of potential energy at mean position should not hold as we neglect high powers terms $(x-x_0)^3$ etc.but as x increases so we can't neglect high power terms. Then the expression of quantized energy $(n+1/2)\hbar\omega$ which we get by solving Schrödinger equation also doesn't hold.

The wave function diagram also shows that the distance from mean position increases as vibration quantum number increases.

Please tell me where is flaw in my argument.


texts: Wikipedia defines a cluster as an ensemble of bound atoms or molecules that is intermediate in size between a molecule and a bulk solid. What is meant by a bulk solid? I can't find a definition anywhere? Further, is this a good enough definition?


texts: Why are we still using cis/trans system while the E/Z system is better than it?

texts:
I am currently learning about Alkenes. It is given that cis/trans isomerism is either ambiguous or doesn't even apply in cases where the alkene is trisubstituted or tetrasubstituted. To solve this problem, we make use of the E/Z system of classifying the diastereomers of alkenes. In some cases both the methods of classifying diastereomers works.

My doubt is, why are we still using cis/trans system while the E/Z system is better than it? Is the cis/trans system better than E/Z system in some way?


texts: Why are some molecules unable to absorb infrared radiation?

texts:
Methane $\ce{CH4}$ is symmetrical and non polar, and so is oxygen $\ce{O2}$. But $\ce{O2}$ doesn't absorb IR. Why is that? People say that if a molecule can change its polarity then it will absorb IR, but I don't understand how a molecule changes its polarity while absorbing IR.

Please try to keep your answer simple — I don't have a strong background in infrared spectroscopy.


texts:
CO2 has sp hybridization and no lone pairs on carbon.

For some reason calculation with VSEPR gave sp2 hybridization and lone pair on carbon.


texts: Why is the melting point of tert-butyl alcohol 140 °C higher than that of sec-butyl alcohol?

texts:
This is one of the most drastic differences in a physical property I've ever seen for two such similar molecules, and in a simplistic sense anyway the difference lies in the opposite direction from what one might expect.  tert-butyl alcohol is completely sterically hindered from participating in H-O hydrogen bonding so it would seem to be limited to van-der-Waals interactions. sec-butyl alcohol interactions should be dominated by van-der-Waals forces, but should also have some ability to participate in hydrogen bonding.  Furthermore, sec-buty alcohol has a slightly larger van-der-Waals surface.

These are such common reagents and the unusually high melting point of tert-butyl alcohol is so well known that there is a surprising dearth of information on theoretical or experimental evidence available (in my searching anyway) explaining the reason for this $\pu{140^oC}$ disparity in melting points.

Does anyone know of a concise, coherent explanation for this observation?


texts: Calculating reaction products programmatically?

texts:
I was wondering if there was a known algorithm which could calculate simple reaction products - not anything organic, but things like

$$\ce{NaBr + LiF -> NaF + LiBr}$$

While these are quite easily to be worked out mentally, I cannot think of an easy way in which these reaction products could be predicted. Is there some software which does this (most I have found simply uses databases of known reactions), or even better an algorithm which does it?


texts: Find the electrode potential of a solution

texts:
I'm stuck with the next exercise.
What  is the electrode potential (against NHE) in the solution prepared by adding 90 mL of $\ce{ KI }$ 5.0 M to 10 mL of $H2O2$ 0.10 M, with a buffer at pH 2.0?
First I wrote the reduction half-reactions
$$ \ce {I2(s) +2e- ->2I-} $$
$$ \ce {H2O2 +2H+ +2e- ->2H2O} $$
then I wrote the complete reaction where $ \ce {H2O2} $ reduces and $ \ce {I-}$ oxides with the number of initial and final moles
$$ \ce {H2O2 +2H+ +2I- ->2H2O + I2(s)} $$
$ \ce {Initial:   0.001 n H2O2 , 0.045n 2I-  } $
$ \ce {Final:   x  H2O2 , 0.043+x  2I-   } $
and as the products are solid or liquid they have standard concentrations
Since it is not easy to know x, I proceeded to use Nernst's equation to find the potential of the electrode with the pair of iodes and knowing that the $E$ for this is $0.5345 V$
$$\ce {E = 0.5345 - \frac{0.05916}{2} log({\frac{0.043n}{0.1L}}})^2 = 0.5305V$$
but when I see the correct answer it appears as $0.419V$ and I don't know where is my mistake :c thanks for read. <3


texts:
Can Grignards react with diatomic halogens as to perform an substitution reaction?

I'd imagine that the first part of making the reaction work - polarizing the halogen as to prepare to pull it apart - would be easy for a Grignard. Hell, even alkene pi bonds can polarize halogens sufficiently; why can't a Grignard?

So in essence, can phenylmagnesiumbromide react with $\ce{Cl2}$ to make chlorobenzene? The other product of this reaction would be $\ce{Cl-}$ ... which I could see combining with the $\ce{MgBr+}$ in some way.


texts: Mechanism of the reaction of an alkene with excess HI in presence of CCl4

texts:
Problem

Answer

 2-iodopropane

Question
I thought of Markovnikov's rule and suggested 1,2‐diiodopropane as the the final product:

Apparently, this is wrong. I can not figure out the mechanism of this reaction (will $\ce{HI}$ dissociate in the presence of $\ce{CCl4}?)$ And what is the significance of excess $\ce{HI}$ here?


texts: I think elements can be broken down, but their definition says otherwise, why?

texts:
Elements are made up of quarks, right?
and physicists have smashed atoms into one another to get quarks, right?

Then if the first two statements are true then elements can be broken down into simpler substances.

If I am right, then can someone give me a better definition?


texts:
Consider this reaction:
$$\ce{Fe^{2+} (aq) + S^{2-} (aq) <=> FeS (s)}$$
The equilibrium constant for the reaction is $1.6 \times 10^{17}$ at $\pu{298K}$. If equal volumes of $\pu{0.06 M}$ of $\ce{Fe^2+}$ and $\pu{0.2 M}$ of $\ce{S^2-}$ are mixed, the concentration of $\ce{Fe^2+}$ at equilibrium is found to be $A \times 10^{-17}$. Find $A$.

Let $x$ amount of $\ce{Fe^2+}$ is converted to $\ce{FeS}$. Then
$$K = \displaystyle {\frac{1}{(0.06 - x)(0.2 - x)}}$$ Which then leads to the quadratic equation
$$ x^2 - 0.26x + 0.012 - 6.25 \times 10^{-18} $$
Solving this the $A$ I got is not the answer.
Answer is $8.93$


texts: How on the quantum level do the notch filters used in Raman spectroscopy remove only a select wavelength of light?

texts:
From what I have gathered regarding the schematics of Raman spectrometers, the notch filter is used to remove a narrow range of light corresponding to that of the laser used to excite the sample. How is this accomplished? I can't find a reference which can explain the physics as to why the filters work. I was thinking that the molecules which make up the filter would absorb at a very selective range. But then why wouldn't one get 'light contamination' from the Raman scattering due to the filter itself? How is this avoided or is the filter in some way immune to the Raman scattering effect?
I assume this can only be explained with QM but if it can be explained more simply I would welcome that response as well.

Edit:
I had this question after watching this video https://www.youtube.com/watch?v=tRrOdKW06sk . If the notch filter is an interference filter as suggested in the comments, the semantics of the question changes to encompass that of interference filters. What is actually occurring at the atomic level so that the angle at which the incident light strikes the filter determines its ability to pass through the filter? Is this due to crystal structure possibly? Why does this angle affect transmittance vs. reflection?  And finally why will the laser still only allow one specific wavelength to transmit?


texts: If A is a stronger acid than B then is B necessarily a stronger base than A?

texts: It seems like this must be true. So if it is could someone please prove this?


texts: is rydberg constant and rydberg unit are same?

texts: i want to ask a question that.is rydberg constant and rydberg unit are same. UNIT OF RYDBERG CONSTANT IS m^-1, right? Then what is rydberg unit.


texts: What does all chromatography have in common?

texts:
We're learning about chromatography in class, and I'm confused about all the different types (e.g. those that separate liquid-liquid solutions vs. those that separate liquid-solid solutions vs. those that separate solid-solid solutions, etc.).
Could you provide a summary of the similarities between all forms of chromatography? (just an overview, do not require specifics)


texts: If nothing sticks to Teflon, how does Teflon stick to frying pans?

texts:
The most notable characteristic of polytetrafluoroethylene (PTFE, DuPont's Teflon) is that nothing sticks to it. This complete inertness is attributed to the fluorine atoms completely shielding the carbon backbone of the polymer.

If nothing indeed sticks to Teflon, how might one coat an object (say, a frying pan) with PTFE?


texts: When you increase the temperature such that change in Gibb's free energy becomes zero, does Keq = 1 at that temperature?

texts:
$$\Delta G = \Delta H - T \Delta S$$

say for example, both $\Delta H$ and $\Delta S$ are positive. So assuming $\Delta H$ and $\Delta S$ do not change or change minimally with temperature, if you increase the temperature until $\Delta G = 0$, is the equilibrium that you reach an equilibrium in which reactants and products are in standard conditions i.e. $K_\mathrm{eq} = 1$?


texts: What is the product formed in the reaction of dimedone and benzaldehyde?

texts:
I'm having a hard time deducing the structure of the product formed when dimedone and benzaldehyde react in the presence of catalytic piperidine. I think that a Knoevenagel reaction will get me to this product:

but the answer says that the product has a molar mass of 368 g/mol. The product above is only 246 g/mol. What else can have occurred?


texts: In the graph provided, which of the substances is the most efficient in acting as an antacid?

texts: If every dot represents the addition of 0.1 g of the respective base. I suppose that the best would be the one that reaches the highest pH, in the shortest time, for example Calcium Carbonate, but if that is true, why are other antacids used that reach lower pH?


texts: Find amount of benzoic acid in dissolution

texts:
Solubility of benzoic acid in water at $\pu{0^\circ C}$ is $\pu{1.7 g/L}$ and given the fact that $\pu{37 mL}$ was used to dissolve $\pu{1 g}$ of benzoic acid. How much of the benzoic acid would be left over given these conditions?

I have tried using $c = m/vM$ to convert $\pu{1.7 g/L}$ to a form given the $\pu{1 g}$ and the $\pu{37 mL}$ actually used. How would I find out how much is left over?


texts:
I noticed that the melting point for non metals decreases across a period (i.e. melting point of nitrogen is higher than oxygen, oxygen's is higher than fluorine, so on). It is significantly more noticeable for chlorine and argon. Why is this? Furthermore, I a question came up in my homework asking sulfur (S8) had a higher melting point than phosphorus (P4). Their explanation was that sulfur is a larger molecule, but I don't see how this affects melting point. Is there a better explanation?

Note - this is the graph I was referring to for melting point: http://antoine.frostburg.edu/chem/senese/101/periodic/images/meltingpoint.gif


texts: Whether copper can combine with oxygen in equal proportion?

texts: Copper sulphide contains 66.6% copper and sulphur trioxide contains 40% sulphur. According to law of reciprocal proportions copper is 80% in copper oxide. The calculation: In the first, for 33.4% sulphur, there is 66.6% copper. In the second, there is 40% sulphur. Therefore, in the resultant there should be 80% copper. My question is why cannot we calculate the other way round:In the second, for 40% sulphur there is 60% oxygen; therefore, for 33.4% there should be 50% oxygen. Hence, the resultant combination should have equal proportion of copper and oxygen. Is there any such substance?


texts: Do these lead plates have a protective coating? Is it possible to test?

texts:
I've just begun teaching chemistry and physics at a local school. We're just getting started on radioactivity and i was looking through the schools supplies when i discovered these soft heavy grey plates used for measuring decay through walls. I've measured the plates' density and IT matches that of lead.
The thing is that i know new sets of these have a coating that prevents lead exposure, i am however, unsure wether these plates have that coating. Sone have a greenish coating I recognize from my own time in school, but the others I am unsure about

L: Coated plate. R: plate in question


texts: What is the quantum mechanical explanation of X-ray diffraction?

texts:
One topic in crystallography that I've found a surprising dearth of information on is what the fundamental interaction behind the interaction of the X-ray and atom. Pretty much every book just treats them as classical waves instead of explaining the quantum mechanics behind it. By this I don't mean that interference that leads to diffraction, but what actually happens when the X-ray interacts with the electron cloud.

The only description I've found so far is in Glusker, Lewis and Rossi that talks about:

  "When X rays hit an atom, the rapidly oscillating electric field of the radiation sets the electrons of the atom into oscillation about their nuclei. This oscillation has the same frequency as that of the incident radiation. The result is that the electron acts as an oscillating dipole that serves as a source of secondary radiation with the frequency of the incident beam."

and goes on to note that this is coherent scattering and there is no wavelength shift.

Which doesn't make a ton of sense, isn't oscillating about the nuclei an old pre-quantum explanation of orbitals? Is this saying that this is similar to fluorescence/phosphorescence where the photo is absorbed, then another emitted? That is what most of the other grad students I've talked to have assumed, but if that was the case I'd expect a Stokes shift, the direction of emitted radiation to be random, and I don't see why you'd get a $180^\circ$ phase shift.

The other explanation I've heard is that you are actually sloshing electrons around within their orbitals, with the same frequency as the X-ray, similar to when you are dealing with optical properties, but I'm not sure what the mechanism for the interaction would be in this case.


texts: T1 spin-lattice relaxation times, deviation from exponential relationship

texts:
For longitudinal relaxation, one would think that the magnetic moment obeys this simple relationship

$$M_z = M_0\left[1 - 2\exp\left(\frac{-t}{T_1}\right)\right].$$

However there is always a point of inflection when magnetisation is zero. Does anyone knows why?

edit: I deleted the image and added some from my own experiment for mineral oil.

In this scenario, the sample is placed under a large longitudinal z-magnetic field. To measure T1, a 180 degree pulse is applied to flip Mz, then a 90 degree pulse after time t. Mo is the equilibrium longitudinal magnetic moment.

I don't think this is due to the mixture of compounds, because it is observed in all samples I tried e.g glycerine, Fe(NO3)3.


texts: What is the hybridization of the nitrogen in the azide ion?

texts: In the azide ion, there is a symmetrical arrangement of three nitrogen atoms. If I've been told to figure out the hybridization of each nitrogen atom, what's the best way to go about doing this? My initial guess was that the central nitrogen was sp hybridized and then the other two were sp2, but I can't seem to justify my guess.


texts: Numbering heteroatoms and groups in benzene derivatives

texts: Can someone please explain why the carbon in 8-hydroxyquinoline is numbered 8, while in 1,10-phenanthroline the nitrogens are numbered 1 and 10? I'm counting carbon atoms and just cannot see why the hydroxy is in position 8 and nitrogen atoms are in positions 1 and 10.


texts: Is there any theory more advanced than MOT?

texts:
I am currently going through molecular orbital theory(MOT), I should appreciate it's a very nice theory and it's helping me to fill the gaps of normal hybridization concepts and valance bond theory(VBT). But I am unaware about it's limitations seemingly it's the most advanced theory and have the capability of explaining everything. Although we know everything has it's limitations so if exist then what are they?
It will be also interesting to know about some modern viewpoints, accepted or proposed theory, and concepts regarding this stuffs.


texts: Is it safe to use lab-grade calcium nitrate as a fertilizer?

texts: I want to use lab-grade calcium nitrate in my hydroponic system (as a fertilizer) to grow lettuce, is it safe?


texts: Determine the concentration of hydrogen cations to prevent precipitation of monocalcium phosphate?

texts:
Determine the $\ce{[H+]}$ needed to just prevent precipitation by $\ce{H2PO4-}$ in a $\pu{0.25 M}$ $\ce{H3PO4}$ solution that has $\ce{[Ca^2+]} = \pu{0.15 M}$.
  The $K_\mathrm{a1}$ of $\ce{H3PO4}$ is $7.1 \times 10^{–3}$. The $K_\mathrm{sp}$ of $\ce{Ca(H2PO4)2}$ is $1.0 \times 10^{-3}$.

For this problem, I first found the $\ce{[H2PO4-]}$ present in the solution when it becomes saturated, which is $\pu{8.2 \times 10^-2 M}$. So I interpreted this as at equilibrium, there is at most $\pu{0.082 M}$ $\ce{H2PO4-}$ present in the solution. When I went to set up my ICE chart for $$\ce{H3PO4 <=> H2PO4- + H+},$$ I put $\pu{0.082 M}$ as the equilibrium value of $\ce{[H2PO4-]}$. However, the answer key wrote

  $
\displaystyle
K_\mathrm{a1}
= \frac{\ce{[H+][H2PO4-]}}{\ce{[H3PO4]}}
= \frac{x (0.082 + x )}{(0.25 - x )}$

meaning that $\pu{0.0082 M}$ is the initial concentration and the equilibrium concentration of $\ce{H2PO4-}$ is $0.082 + x$. But if this was the case, then wouldn't $\ce{Ca(H2PO4)2}$ precipitate since there's more than $\pu{0.082 M}$ at equilibrium?

I think I'm probably misinterpreting the question, so any clarification on what's happening here would be appreciated.

edited - MaxW
Added image (cut and paste job for needed parts...) of problem from 2002 U. S. NATIONAL CHEMISTRY OLYMPIAD NATIONAL EXAM—PART II


texts: What is the correct unit for the equilibrium constant?

texts:
I have the following equation

$$K_a = \dfrac{c\alpha^2}{1-\alpha},$$

with units $c= \pu{mol/cm^3}$ and $\alpha$ is the same. I'm not sure how to get the correct units for $K_a$. What I have come up with so far is

$$K_a= \pu{mol^2/cm^6}.$$


texts: Water-soluble powder for traction on wet floor

texts: Do you know of a substance that can be used for traction on a wet floor and dissolve over time and will not corrode steel?


texts: what's the ratio of atoms of these two isotopes?

texts:
here is a question says
:

I know that atom's number is found by =  $6.022*10^{23} * mol$

but how this formula is used here is what i dont know

what's the $idea$ of this question?


texts: What will "Efavirenz amino alcohol methyl carbamate" look like?

texts:
I'm translating a text in which a possible derivative (produced by harsh conditions) of this drug is mentioned:

Its name is put as "Efavirenz amino alcohol methyl carbamate".

I wonder what it will look like.

The carbamate group, according to Wikipedia, will look like this:

And there will also be an alcohol (hydoxyl) group and an amino group somewhere. Will there be two nitrogens, or will the only nitrogen atom particiape both in the "amino group" described in the name and in the "methyl carbamate"?


texts: about Markovnikov's rule, is it wrong to think of it with MO theory?

texts:
Markovnikov's rule stated 'The hydrogen ends up attached to the carbon of the double bond that had more hydrogens to start with.' And many books give it a reason applying stability of carbocation. Carbocation stability is also important for Hammond postulate and rate of a reaction.

But the way I'd like to interpret it is using molecular orbital theory and hyperconjugation. If say C-H sigma bond in assymetric alkene(ie propene) hyperconjugated with pi* orbital, then the other carbon which have no hyperconjugation effect has more orbital coefficient (more pi orbital electron density). This means that the carbon without alkyl substituent is naturally more reactive to take proton. After that, we have tertiary carbocation, proceeding rest of reaction.

I used this concept a lot when I solve problems and found it very useful. However, I just figured that no books, no questions, no google infos suggested this idea at all. so, is this way of thinking wrong? if it's wrong, how so? if it's right, why nobody use it and why all curriculum stress Markovnikov's rule?

(I tried to find a image of asymmetric alkene MO but i couldn't. There is no image of it. But in a book, Oxford Organic Chemistry by Clayden, page 890 has similar image I was looking for. It's HOMO of 1,1-dimethylbutadien. 4th carbon has bigger orbital than the others as pi2 MO)


texts: Evaporating the water of a solution of only carbonate ions and water gives?

texts:
I have a solution with only $\ce{CO_3^{2-}}$ ions and water.

What would happen with the carbonate ions if I were to evaporate the water of that solution (in a vacuum)?


texts:
I am trying to make a mixture of the following ingredients: distilled water, alcohol, aluminum sulphate and glycerin.

The problem is that when I add alcohol to the water and aluminum sulphate mixture (the aluminum sulphate is completely dissolved), the alcohol solidifies the aluminum sulphate again, so I am left with even more solid aluminum sulphate then in the beginning.

What I need is for the mixture to be completely mixed, clear and without solids.

Thank you everyone for your time!


texts: Chemical bond-covalent-valence electrons OH-

texts: I would like to ask how many valence electrons took part in creating chemical bond in $\ce{OH-}$? Is the minus related to $\ce{O}$ or to $\ce{H}$? Are there any spare valence electrons which didnt take part in creating chemical bond in $\ce{OH-}$?


texts: How can you find the concentration of copper(II) ions in a solution of 0.5 mole copper(II) chloride and 0.5 mole of copper(II) sulfate?

texts:
The question I'm trying to answer is below and the answer is C.

I tried finding the total moles of copper(II) ions first by using mole ratios for copper(II) sulfate and copper(II) chloride, obtaining an answer of 0.42 moles. Then, I used $n=cv$ and obtained the concentration, using the volume in the question in litres, of 0.84, which is incorrect. Now, I'm sure my method incorrect but I can't think of another way to this.


texts: I have conducted many searches on this subject with regards to agents which cross the blood brain barrier. I have read about lipoic acid. Is anybody on here aware of any studies or findings which show effective mercury binding and transportation from the brain?


texts:
How does crystallisation happen and why?

I have been told that when a solid is dissolved in a liquid solvent, an equilibrium is set up between processes of dissolution and crystallisation. But if this is so then why does all solute dissolves (I am talking about an unsaturated solution), isn't it supposed to recrystallise simultaneously too?
I am certainly missing a lot and most importantly what crystallisation is and how and why it happens?

I don't want to know anything about the separation technique using the principle of  crystallisation. Just want to know the principle itself.


texts: Why is the bond angle of AB3E1 approximately 109.5?

texts: Since there are 3 B atoms and the angle between each atom is equal, shouldn't the bond angle be equal to 120?


texts: In cleaving ethers with both SN1 and SN2 mechanisms possible, which occurs first?

texts:
What are the products when tert-butyl ethyl ether is cleaved with concentrated $\ce{HI}$?

My answer is iodoethane and tert-butanol, but the correct answer is ethanol and 2-iodo-2-methylpropane.

I know that the ethyl side goes by an SN2 mechanism because it is a primary R group, and the t-butyl group would be SN1 because it is tertiary. However, why would the SN2 reaction not happen first?


texts:
Consider 1,2,3,4,5,8‐hexahydronaphthalene:

If one equivalent of ozone is added, then which double bond will undergo ozonolysis?

If it attacks the more electron rich one, then unstable 10 membered ring will form, and if it attacks the other,less sterically hindered one, stable 6 membered ring having 2 branched aldehydes will form.

What will actually happen? What factors decide this?


texts: Neutralization reaction between ammonia and nitric acid

texts:
Complete and balance the following molecular equation (in aqueous solution); include phase labels. Then, write the net ionic equation.
$~\ce{NH_3 + HNO_3 -> ?}$

I thought that the acid $\ce{HNO3}$ would just give its hydrogen to $\ce{NH3}$ and make the resulting reaction:
$$\ce{NH_3 + HNO_3 -> HNH_3 + NO_3}$$
However the correct answer is $\ce{NH_3 + HNO_3 -> NH_4NO_3}$. Why is this?


texts: Which form of chromium oxide is formed naturally in the atmosphere?

texts:
I'm trying to figure out which form of chromium oxide forms naturally in our atmosphere, i.e., if you take a piece of elemental $\ce{Cr}$ from vacuum to a normal, room temperature environment with air, does it form $\ce{CrO}$ on the surface? Or $\ce{Cr2O3}$? Etc.

This site says:

  Chromium (III) oxide, $\ce{Cr2O3}$ is the main oxide of chromium.

So it seems like it might be that one, but "main" is pretty vague. Does anyone have a more definitive answer, with a source?

thank you!


texts: Why doesn't this question violate the conservation of mass?

texts:
Combustion of of $0.255 \space g$ of isopropyl alcohol produces $0.561
 \space g$ of $\ce{CO_2}$ and $0.306 \space g$ of $\ce{H_2O}$.  Determine the
  emperical formula of isopropyl alcohol.

I'm not asking how to solve this problem, but why this doesn't violate the conservation of mass?  Shouldn't the initial combusted mass equal the sum of the resultant masses?


texts: Why the valence shell configuration of Lead is 6s2 6p2?

texts:
Acoording to energy rule the electronic configuration is in order of 6s 4f 5d 6p but when writing valence shell configuration we write 6s after 4f and 5d.Why is it ?

Take Lead as an example.


texts: What will be the product of this reaction

texts:
I suspect the answer is either one of C or D, but how do I know which one?
Since such a stable carbocation is being formed, I can't choose whether the reaction will be an Sn1 or Sn2 (elimination semms unlikely).

But do I need to transform this fischer projection to some other form for me to easily answer this question?


texts: Balanced Chemical Equations of the preparation of sodium peroxoborate

texts:
I know the chemical equation for the reaction of borax with sodium hydroxide and hydrogen peroxide

$$\ce{Na_2[B_4O_5(OH)_4]\cdot6H_2O + 2NaOH + 4H_2O_2 ->2Na_2[B_2(O_2)_2(OH)_4]\cdot6H_2O + 3H_2O} $$

Now when we were doing the experiment to prepare sodium peroxoborate we added, the $\ce{NaOH}$ first and then $\ce{H_2O_2}$. How do I write the chemical equations for the borax with just the sodium hydroxide and then that product with the hydrogen peroxide. Essentially how do I break the balanced chemical equation that I have into two different steps.


texts: Acid-catalysed Reaction of Ketone with Benzene to Make Benzyl Alcohol

texts:
Benzene shows electrophilic substitution reactions. Normally, anything that can generate a carbocation shows, for example, a Friedel-Crafts alkylation reaction. I wanted to know if this reaction is also possible: taking an aldehyde or a ketone with an acid, which will protonate the oxygen atom and generate a carbocation - followed by electrophilic attack on benzene. This reaction can even go further by protonation of the alcohol and forming another carbocation for a second substitution - as I've shown in the picture below.
I couldn't find this anywhere, though it seems a simple way to make a benzyl alcohol - why isn't it more frequently carried out like other cases like Friedel-Crafts Alkylation, or Acylation, etc.?

Something almost identical happens in synthesis of DDT using chloral and chlorobenzene.
www.liceoagb.es/quimiorg/petroquimica_webquest/aad/DDT.ppt


texts: Is the amount of substance of acid and base always equal at the equivalence point?

texts: Does the amount of substance of acid always have to equal the amount of substance of base at the equivalence point? I know it "works" for monoprotic acids and monobasic bases, but what if we had a diprotic acid and monobasic base?


texts: Determining sulfate content in Mohr's salt

texts:
I am practicing problems for my chemistry test and I am stuck on the following problem:

The value of $x$ in $\ce{Fe(NH4)2(SO4)2 ⋅ xH2O}$ can be found by determining the amount, in moles, of sulfate in the compound.
A $\pu{0.982 g}$ sample was dissolved in water and excess $\ce{BaCl2(aq)}$ was added. The precipitate of $\ce{BaSO4}$ was separated and dried and found to weigh $\pu{1.17 g}.$
Calculate the amount (in moles) of $\ce{BaSO4}$ in the $\pu{1.17 g}$ precipitate. And calculate the amount (in moles) of sulfate in the $\pu{0.982 g}$ sample of $\ce{Fe(NH4)2(SO4)2 ⋅ xH2O}.$

I was able to do the first part of the question:
$$n (\ce{BaSO4}) = \frac{\pu{1.17 g}}{\pu{233.38 g mol-1}} = \pu{0.005 mol}$$
But, I am unsure of the second part. Any help would be appreciated.


texts:
The respective configutations of a and b are...?

I tried to find the answer for a (for me is: 2S, 3S) but I'm not sure of my results, can someone help me?


texts: In solid Iron, what is the charge of the positive atom?

texts:
I'm familiar with the sea model of metals. What I'm curious about is: exactly how many electrons are lost by the iron, to be absorbed into the sea of electrons? For a general metal, how many electrons are lost to the sea of electrons?

Thanks


texts: In an isothermal process, how can the change in internal energy be 0?

texts:
It was written in my textbook,

$$
\mathrm{d}U =
  \left(\frac{\partial U}{\partial T}\right)_V \mathrm{d}T
 +\left(\frac{\partial U}{\partial V}\right)_T \mathrm{d}V
$$
If the process is isothermal, $\mathrm{d}T = 0$. So, the equation reduces to:

$$
\mathrm{d}U = \left(\frac{\partial U}{\partial V}\right)_T \mathrm{d}V
$$

I was told, $\mathrm{d}U = 0$ in an isothermal process, does that mean $\mathrm{d}V = 0$, or  $\left(\frac{\partial U}{\partial V}\right) = 0$? But how is it possible that $\mathrm{d}V=0$ in an isothermal process, or $\left(\frac{\partial U}{\partial V}\right) = 0$?

If someone could explain what am I doing wrong, that would be very helpful.


texts: What bond\crystal has the most regular pattern (i.e. least irregularities)?

texts: Salt is a famous regularly repeating cubic crystal, but there are always natural deformities and flaws present. I have heard that graphene is an extremely uniform substance. With these in mind, what is the most regular crystal pattern, natural or man-made?


texts: pH Dependency of IR Stretching Frequency in CO-binded Heme Protein

texts: If one consumes CO, then CO binds with Heme Protein forming a Fe-CO bond. My question is if there will be any pH dependency on IR Stretching Frequency, i.e. ν(CO) and ν(Fe-CO). And if there is, then what will be the result?


texts: Unusual oxidation states of alkali metals

texts: When going through list of oxidation states on Wikipedia I encounterd there that sodium, potassium, rubidium  and caesium exhibit oxidation states of -1, but not lithium, even though its electronegativity is more than that of the others. How's that possible? Can some one provide an example.


texts: Computing two-electron integrals with an STO-3G basis set

texts:
I am trying to implement a restricted Hartree-Fock calculation using an STO-3G basis set, for fun. I managed to perform this calculation where only $\mathrm{1s}$ orbitals are present ($\ce{H2}$ and $\ce{HeH+}$) as explained in Szabo and Ostlund's book. In this book, authors give explicit formulas for overlap, kinetic, nuclear-electron, and electron-electron integrals for $\mathrm{1s}$ orbitals and they work correctly.

In order to generalize my calculation to systems containing $\mathrm{2s}$ and $\mathrm{2p}$ orbitals (for $\ce{H2O}$ and $\ce{N2}$), I used the general formulas I found in Cook's book for the electron-nuclear and electron-electron integrals. In this case, I obtain results that are slightly different from Szabo's book:

$$E_\text{tot}(\ce{H2O}) = -74.4442002765 \text{ a.u.}$$

instead of

$$E_\text{tot}^\text{Szabo}(\ce{H2O}) = -74.963 \text{ a.u.}$$

This is obviously problematic since orbital energies suffer from the same error and this leads to an erroneous ionization potential (0.49289045 a.u. instead of 0.391 a.u., a difference of approximately 63 kcal$\cdot$mol$^{-1}$).

Since I checked my code multiple times and I wrote the two-electron computation code from scratch twice, I was wondering if there is a typo in Cook's book. Is there is a good reference where I can find the (correct) formula to compute two-electron integrals of gaussian functions (in Cartesian coordinates) with arbitrary angular momenta? At the moment I am not looking for a very efficient (recursive) algorithm to perform this task, I only need an exact formula like the one proposed in Cook's book.

Sources:

[1] Szabo and Ostlund, Modern Quantum Chemistry, Dover, 1989.

[2] Cook, Handbook of Computational Chemistry, Oxford University Press, 1998.


texts: How to calculate the number of waters of hydration?

texts:
I have three questions about waters of hydration, the first two of which I'm really stuck on:

A sample of cobalt(II) nitrate hydrate was heated to remove all the water of hydration. The hydrate was found to be $65.96\%$ oxygen. Calculate the number of water molecules associated with each formula unit of cobalt(II) nitrate.
Epsom salts is $\ce{MgSO4.xH2O}$. The hydrate was found to contain $71.4\%$ oxygen. Calculate the  value of $x$.
Zinc nitrate $\ce{Zn(NO3)2.xH2O}$ contains $21.98\%$ zinc by mass. What is the value of $x$?

I have absolutely no idea for the first two questions.

For the third:

Assume $\pu{100 g}$ of material
$\pu{21.98 g}$ of Zn = $\pu{0.3284 mol}$ of $\ce{Zn}$

I couldn't get any further than this.


texts: My chemistry teacher told me that $\ce{Al(OH)4^-}$, $\ce{Pb(OH)4^2-}$, $\ce{Zn(OH)4^2-}$ are called complex ions. So will they break down in some conditions and give out $\ce{OH-}$ to show alkaline property or just remain neutral?


texts: Does the rate constant depend on pressure?

texts: I have read in some books that when pressure increases, the number of effective collisions increases. Hence, $k$ depends on pressure. Is it true? If so, then why doesn't $k$ depends on concentration? The number of effective collisions should increase here also.


texts: Reduced-pressure (vacuum) evaporation/drying of 15 liters of aqueous solution

texts:
I have 15 liters of aqueous solution inside an aluminum stock pot which rests upon a hot plate. I want to reduce the boiling point from 150°C to 100°C using reduced pressure.

What is the most economical way efficiently to dry the solute? Economical means does not require specialty equipment (i.e., laboratory vacuum pumps, expensive cold traps, etc.)?

I own a water aspirator pump (attaches to sink, 27.4 in Hg maximum vacuum, 6 liters/minute) and a 2-stage electric vacuum pump (15-micron, 3CFM) that I use for degassing epoxies. I don't know whether either of these will be of any use here.


texts: What is the hybridisation in dimolybdenum?

texts:
Dimolybdenum's $\mathrm{4s}$ and $\mathrm{4p}$ orbitals are full. It is going to use its $\mathrm{4d}$ and $\mathrm{5s}$ orbitals to form a sextuple bond (2 $\sigma$, 2 $\pi$, 2 $\delta$). I am wondering if the $\mathrm{4s}$ and $\mathrm{4p}$ orbitals are going to hybridize with the $\mathrm{4d}_{z^2}$ orbital (the one forming the first $\sigma$ bond) and the $\mathrm{5s}$, given the differences in energy. The hybridisation would be $\mathrm{ds^2p^3}$, which is certainly uncommon.

If so, do the $\mathrm{s}$ and $\mathrm{p}$ lone pairs always hybridize, even if they don't form any bonds?


texts: Not a chemist, needs help with a calculation regarding addition of HCl to sodium formate solution

texts:
As stated I am not a chemist, but I need help on a question I have.

Assume I have a Formic acid 75% and I add between 5-10 kg to 1.000 liter of water. If I wanted to add sodium formate and HCl 37% to water and achieve a similar result  with regards to pH and "pure" undissociated formic acid how much of each product would I need to add?

I have calculated, probaly wrong, that I would need 8 ml of HCl to 1.000 L to lower pH to around 4 which is close to pKa of FA (3,75), but I do not know if this will give me the same amount of undissociated FA as the original scenario.

For my application idea pH is less important than undissociated (antibacterial) FA.

Hope someone takes up the (over my head) calculation challenge


texts: Which part of the reaction of potassium with water releases more energy?

texts: When potassium is reacted with water, hydrogen is given off, which is normally ignited by the heat of the reaction and combusts. How much energy is given off by the burning hydrogen compared to the potassium reaction?


texts: What is the largest known zero-point energy for a molecule?

texts:
I was surprised to find out that the zero-point energy (ZPE) for the ground state of $\ce{BH3}$ is a few thousand $\pu{cm-1}$, because for molecules I usually work with, it's much smaller. Does anyone know the largest recorded ZPE?

I have recently asked a similar question: What is the biggest known difference between $r_e$ and $r_0$?


texts: Mistake in finding bond angles in VSEPR theory

texts:
Find the bond angles as indicated, in the compounds given below, according to VSEPR theory-

I got: $109.5^\circ$(6),$109.5^\circ$(7),$109.5^\circ$(8) for the compound (d). But the given answer says it is wrong. But I don't know why. Everything else I got them right.