texts:
I have an electric mantle that I want to bathe reaction vessels at temperatures up to $\mathrm{750^{\circ}C}$.  Obviously that rules out oils.  What substances are used as bath media at such temperatures?

I was thinking of using lead or Rose's alloy, but wondering if there are more standard high-temperature bath chemicals?  I suppose an ideal one would be both inert to lab steel, glass, and a standard atmosphere, and liquid down to room temperature.


texts: How to generate Density Functional Tight Binding parameters (Slater-Koster files)?

texts:
What is the simplest way (or least complicated way) to generate parameter files (.skf) to be used with DFTB+, for example?

Assuming I want to be able to reproduce geometries for a certain type of molecules, how would I go about it?


texts: An introduction to "oxidation state"/"oxidation number"

texts:
I just can't get my head around oxidation states. They're really confusing! Why do I need to assign a number to some element?

What are oxidation states?
How and why should we assign oxidation states?
Are oxidation states real?


texts: Can you ignite the thermite reaction in a solution?

texts:
As far as I know thermite is a typical redox reaction where $\ce{Al + Fe^{3+} -> Fe + Al^{3+}}$ happens. I guess the activation energy is very high, because you need to split the $\ce{Fe_2O_3}$ into $\ce{Fe^{3+}}$ and $\ce{O^{2-}}$. Probably you need molten aluminium too at $\pu{660°C}$ to ignite it.

I was wondering whether it is possible to ignite thermite in a water solution. Since $\ce{O^{2-} + H_2O -> 2OH^-}$, I guess a very acidic solution could help to start the reaction, since $\ce{OH^- + H^+ <=> H_2O}$. On the other hand it could mean a $\ce{2Al + 6H^{+} \rightarrow 2Al^{3+} + 3H_2\uparrow}$ reaction too.

Any idea whether thermite can be ignited this way, for example with a drop of concentrated acid? Or will it just result hydrogen gas, because that reaction has a lot lower activation energy?


texts:
Why does the basicity of Group 15 hydrides ($\ce{NH_3,~ PH_3,~ etc}$) decreases down the group ?

I know that's because of its Lewis Base nature due to the lone pair but wouldn't the more EN element be less reluctant to give the lone pair ?
 And nitrogen is most EN in that group .


texts:
Why is the Still-Gennari reaction Z-selective?

I guess dipole interactions have the biggest influence here. They somehow destabilize the reversion of the oxaposhpetane to the betaine and prevents formation of the more stable E isomer but I am not sure.


texts:
I am planning on making some homemade soap soon and have read online that breathing in the fume generated from the reaction between lye and water is not recommended because it is "hazardous."

I am a little bit confused because I thought the reaction between lye and water is simply a highly exothermic dissolution reaction and therefore the "fumes" would consist of only steam?

                           NaOH + H2O -> OH- + Na+ + H2O + HEAT

If this fume is corrosive, does that mean there is some gaseous hydroxide as well generated from the heat? Why else would this fume be dangerous?


texts: Priority of carbons attached to chiral group, one with double bonded oxygen, one with two oxygens

texts: I have a chiral carbon. Two of the atoms attached to the carbon are other carbon atoms. One of those carbons has a double bonded oxygen and a methyl group attached. The other has two oxygens and a methyl group. Which carbon substituent has higher priority?


texts: Is there a way to detect bleach residue on a surface?

texts:
I was wondering if there is a way to detect for presence or residue of bleach using household items.

I am curious about either chlorine-based or peroxide-based. It can be any sort of reaction that shows the presence of it. Well, as long as the reaction doesn't produce a lot of heat or is somehow toxic.


texts: What's the standard deviation in bond angle for water molecules at a particular temperature?

texts:
Suppose I have a beaker of water at 20 °C. I want to know the standard deviation of the bond angles between the hydrogen atoms in the water molecules. How do I figure this out?

If I knew that the bond angle was the only possible degree of freedom of the molecules, then I'd be able to use the Boltzmann distribution to calculate this, if I knew the energy of the molecule as a function of bond angle. But I don't know the energy of the molecule as a function of bond angle, and also there are a lot of other degrees of freedom (e.g. the molecules can have overall kinetic energy, or they can be spinning rapidly, or the other vibrational modes of the water molecule can contain some of the energy.

Is there an easy way for me to look up the energy of the water molecule as a function of the positions of the hydrogen atoms? (I guess I could just calculate this myself using my favorite quantum chemistry software.)


texts: How actually do we decide acidity and basicity order?

texts:
In a book, I read two quite contradictory statements.:

$\ce{HIO > HBrO > HClO}$ wrt acidity while

$\ce{HF > HCl > HBr}$.

Aren't they contradictory? If not can anyone please explain the accurate reasoning?


texts: Can there be oxygen dissolved in water in a hydrogen atmosphere?

texts: I'm trying to determine (for a science fiction story) whether a certain type of planet could have a significant amount of oxygen dissolved in water (e. g. produced continuously by some aquatic organism) if its atmosphere was made mostly of hydrogen. Is there a way, or will any oxygen just "pop" out of the water into the atmosphere and react with the hydrogen? I'm assuming the hydrogen pressure would be in the order of 10-100 atm.


texts:
I was reading my school text book and in the segment related to the reactivity of group 13 elements with acids and alkalis it was written:
Boron does not react with acids and alkalis even at moderate temperatures
Earlier it said that it is weakly acidic so I attributed that to it's non reactivity with acids but I can't seem to find any reason why it doesn't react with bases.


texts: Are melting points for mixtures of solids ALWAYS below the melting points of the individual components?

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In every chemistry lab we are taught that mixtures of compounds are going to have melting points lower than either of the components pure melting points.

Is this always true? Or can there be ratios of compounds that would generate a melting point above one pure compound and below the other?

For example, lets take acetanilide (MP: 114 C) and mix it with sodium acetate salt (MP: 324 C) in varying ratios. What would the melting points be for these?

1.) 98% acetanilide, 2% sodium acetate (slightly below 114?)

2.) 75% acetanilide, 25% sodium acetate (slightly above 114?)

3.) 50% of each (significantly above 114?)

4.) 25% acetanilide , 75% sodium actate (below 324?)

5.) 2% acetanilide, 98% sodium acetate (slightly below 324?)

NOTE: I chose these two compounds completely arbitrarily. Perhaps there is literature that has examined melting points for varying ratios of two particular compounds?

Follow up question:

Does there exist a mixture and/or ratio of solids that intermolecularly bond so strongly to each other that the melting point of that mixture is higher than the melting point of the individual components? What about a specific azeotrope with a higher boiling point than the liquids that make it up?


texts: Why is the dipole moment of XeF$_6$ zero?

texts:
In Concise Inorganic Chemistry by JD Lee (4th edition; adapted by Sudarshan Guha), page 73 under the section 3.6 (VSEPR Theory chapter Chemical Bonding):

...according to this theory, the position of the lone pair in $\ce{XeF6}$ molecule should be in axial position and the shape should be pentagonal pyramidal. But this is not observed and the actual shape of molecule is octahedral. This implies that the lone pair is placed at equatorial position, and this explains the structure of $\ce{XeF6}$ shown in figures 3.7 a,b,c.
According to Figure 3.7, $\mu_\text{expected}$ for $\ce{XeF6}$ is not equal to zero. But $\mu_\text{real}(\ce{XeF6})\sim0$ . To explain the above facts, it is considered that the actual molecule is in dynamic equilibrium of all the three structures shown in Figure 3.7. Here it is considered that the lone pair is present in the stereochemically active $s$ orbital and similar structure is observed as $\ce{IF6-}$. But anions like $[\ce{SbX6}]^{3-}$, $[\ce{TeX6}]^{2-}$ ($\ce{X}=\ce{Cl, Br, I}$), $[\ce{BrF6}]^-$,$[\ce{ICl6}]^-$ have been assigned perfectly octahedral structure on the basis of X-ray crystallography and the lone pair is present in stereochemically inactive $s$ orbital.

It is explained the three structures given in the above diagram are in dynamic equilibrium, so dipole moment is zero. But I feel it must be towards the right since the lone pair of electrons stays mainly towards right since the vertical component cancel (structure c and d)
Could you please explain how according to the author, the dipole moment of XeF$_6$ be zero.
Kindly note: I have read this question related to the same passage but a different concept. My doubt is not about stereochemically active or inactive s orbitals but about the non-existence of dipole moment in the given compound.


texts:
Electrodes: Zinc electrodes
Electrolyte: molten sodium iodide

I know that at the cathode, sodium metal will be formed because only sodium ions are present for reduction.

At the anode, originally iodine should be formed with inert electrodes such as graphite. However, since zinc electrodes are used, and zinc metal is a stronger reducing agent than iodide, hence zinc should be oxidised into zinc ions.

My question is: what will be the reaction occurring at the anode? Will zinc ions or iodine be formed? Or is this case of electrolysis even possible?


texts: Harmless & pungent volatile liquid for use in a stage show

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If for some stage play/trick we would like to create some surprising effect in which something with a pungent odor has been released, but at the same time need to ensure that thing be absolutely safe for participants and audience. Is there any organic compound that can do this?

I assume that the compound should be volatile as possible to be effective which reminds me of benzene; however it is detrimental to health. Any recommendation for safer liquids?


texts:
I am trying to understand the structure of elemental, crystalline sulfur. I read that it is face-centered orthorhombic. My question is whether each point on the unit lattice contains a single atom of sulfur or a S6 molecule?

Thanks to anyone reading.


texts: Do molecules with carboxyl groups have properties of carboxyl's sub-functional-groups?

texts:
We're learning about functional groups of different organic molecules, and there are some I'm confused about: carboxyl, carbonyl, and hydroxyl. I was looking online but I couldn't find a direct answer

I know that the carbonyl group is a "-CO", the hydroxyl group is a "-OH", and the carboxyl group is a "-COOH".

We learned that carbonyl groups make molecules a ketone or aldehyde, the hydroxyl group makes molecules alcohols, and the carboxyl group makes molecules carboxylic acids.

Knowing that that a carbonyl group is just a carbon double-bonded to an oxygen, and a carboxyl group is a carbonyl group bonded to a hydroxyl group, then should carboxyl molecules also have all the properties of hydroxyl and carbonyl groups (such as being an alcohol), on top of its new ones? Or, does it only have the properties associated with themselves?

Thanks.


texts:
I was provided with a drug compound which is filling a hydrophobic pocket. The R group is changed and effects on the potency was measured; $\ce{R = -H, -CH3, -CH2F}$ were tested. As expected, the more lipophilic group $\ce{-CH2F}$ had the smallest dissociation constant. However, the question went on to ask me to suggest other groups that could be tested. Investigating more lipophilic compounds would be wise, to further prove that the pocket is indeed hydrophobic.

It was suggested $\ce{-OCH3}$ as one of the groups that could be substituted for R. I am confused, because wouldn't the oxygen be able to form hydrogen bonds, making it hydrophilic rather than hydrophobic?

My question is, how do we classify a compound to be lipophilic? i.e. How do we know if the molecules form hydrogen bonds or not?


texts: Example of chemical reaction with a given form for the kinetic equations

texts:
I’m an applied mathematician looking for examples from various applications fields (right now, chemistry, obviously) to illustrate the following reaction-diffusion system
$$
\begin{cases}
\frac{\partial u}{\partial t} - d_u \Delta u = k_1 v + (k_2-k_3) u - k_4 u^{p_1} v^{p_2} - k_5 u^{p_3+p_4} \\
\frac{\partial v}{\partial t} - d_v \Delta v = k_6 u + (k_7-k_8) v - k_9 u^{q_1} v^{q_2} - k_{10} v^{q_3+q_4}
\end{cases}
$$

Above, all constants $d_u$, $d_v$, $k_i$, $p_i$, $q_i$ are positive, and $p_i,q_i\geq 1$. $k_2-k_3$ and $k_7-k_8$ might be of any sign. The system need not be self-contained — if you need to add a third equation in order to make these two exist, feel free to do so.

If the diffusion part is bothering you, then I’m also fine with
$$
\begin{cases}
\frac{\text{d} u}{\text{d} t} = k_1 v + (k_2-k_3) u - k_4 u^{p_1} v^{p_2} - k_5 u^{p_3+p_4} \\
\frac{\text{d} v}{\text{d} t} = k_6 u + (k_7-k_8) v - k_9 u^{q_1} v^{q_2} - k_{10} v^{q_3+q_4}
\end{cases}
$$

And if the $p_i$ and $q_i$ are bothering you, then one example where they are all equal to $1$ is
$$
\begin{cases}
\frac{\text{d} u}{\text{d} t} = k_1 v + (k_2-k_3) u - k_4 u v - k_5 u^2 \\
\frac{\text{d} v}{\text{d} t} = k_6 u + (k_7-k_8) v - k_9 u v - k_{10} v^2
\end{cases}
$$

One more precision: if $k_2-k_3\leq 0$, then $k_5=0$ is allowed, and similarly, if $k_7-k_8\leq 0$, then $k_{10}=0$ is allowed. Therefore the following system would be a satisfying answer:
$$
\begin{cases}
\frac{\partial u}{\partial t} - d_u \Delta u = \tilde{k}_1 v - \tilde{k}_2 u - \tilde{k}_3 uv \\
\frac{\partial v}{\partial t} - d_v \Delta v = \tilde{k}_2 u - \tilde{k}_1 v - \tilde{k}_4 uv
\end{cases}
$$
(where the constants $\tilde{k}_i$ differ a priori from the previous constants $k_i$).

I looked for actual examples of first-order reversible reactions. I found $\ce{Cu+ <-> Cu^{2+}}$ there but I do not know if having an irreversible reaction “$\ce{Cu^+ + Cu^{2+} ->}$ some product” in this configuration is possible.

Can you think of any “real” chemical system that would satisfy such kinetic equations?


texts:
I wanted to ask an online group of experts/community about how I could improve in chemistry. I study in 10th grade currently and don't get very good grades. Most of the time its a B or C.

I have to select science stream, in which physics, chemistry and maths are compulsory. I am good in physics and maths, but what should I do in chemistry?

I have a hard time grasping concepts like Ionisation Energy, structure of benzene etc. and these are only going to get 100 times tougher next year!


texts: Finding large databases of sphere packings

texts:
Part of my research is investigating sphere packings and their properties.I really would like a large database of sphere packings that I could investigate using a program I have written that tells me certain things about the packings. After doing some research I found some online databases but a lot of them haven't been taken care of so they're riddled with dead links.  I was wondering if anyone knows of any books or websites that have a lot of sphere packings that I could investigate.  Or if there is a way to interpret crystal structures as a sphere packing, seeing how there is a lot of crystal structure databases.

If anyone is confused as to what kind of data I'm looking I just need coordinates of the centers of spheres and their corresponding radii.  These need to form a packing where the spheres are touching like in this paper where the authors have found new bi-disperse packings.  Thanks!

http://pubs.acs.org/doi/abs/10.1021/jp206115p


texts:
We are trying to predict the pH-value of a multicomponent buffer. It consists of:

\begin{array}{lcrr}
\# &\text{Component} &C,\,\pu{mol L-1} &\mathrm{p}K_\mathrm{a1} &\mathrm{p}K_\mathrm{a2} &\mathrm{p}K_\mathrm{a3}\\
\hline
1 &\text{Citric acid} &\pu{2.60e-5} &3.13 &4.76 &6.40 \\
2 &\ce{NaH2PO4} &\pu{5.65e-3} &7.21 & &\\
3 &\ce{(NH4)2SO4} &\pu{2.27e-3} &9.20 & &\\
4 &\ce{NaHCO3} &\pu{1.19e-3} &10.33 & &
\end{array}

Our problem is that we don't know how to combine several equilibria which exist in the solution. Since $\ce{NaHCO3}$, for example, is an ampholyte, it is difficult to tell if it reacts as an acid or a base.

Although this should be a somewhat common problem, we didn't find any formula or method to calculate the pH of such systems. We would be thankful for any idea!


texts:
I am confused regarding the following problem  which asks to arrange the given compounds in decreasing order of their degree of dehydration

My attempt at the solution:
I tried to find out the products and compare their stability:

Now in the first case product is conjugated. So I think it is the most stable.
The second one has 6 alpha hydrogen while the third one has only 3 alpha hydrogen.
Hence order should be 1>2>3
But the answer given is 1>3>2

My second confusion is whether such alpha-hydroxy ketones will follow the E1 or E2 dehydration process. I thought that E1 elimination won't be favourable cause the positive charge next to the keto group will be destabilised. Is it correct?


texts:
I was solving this question and I thought the answer was B>C>A as more the resonance, more the pi electrons are delocalized so more free movement.

However the answer mentions it as B>A>C.

What is wrong with my reasoning?


texts: Balancing redox equations in acidic media: to use H+ or H3O+?

texts:
Is it preferable to balance redox equations with  $\ce{H+}$ or $\ce{H3O+}$? I think the latter, because first, the bare hydrogen proton doesn't exist in water solution. So why write down something we know not to exist?

I ask because in this problem, if we balance using both species, $\ce{H^+}$ and $\ce{H3O+}$, we achieve two different equations. Mass is conserved in both equations as well as charge; all the differs is one coefficient.

So are the two equations equivalent in that they are still describing the same reaction? I think so, because sometimes I see textbook authors write these two equations for $K_\mathrm{w}$:

$$\ce{H2O <=> H+ + OH-}$$

$$\ce{2H2O <=> H3O+ + OH-}$$

However, if we were actually going to run an experiment and needed exact quantities, we would probably prefer the second reaction both above and below because the coefficients in these reactions better represent the chemistry of the system right?

For example, which of the following is "better"?

$\ce{ClO_{3}^- + 6I^- + 6H^+ \leftrightharpoons 3I_2 + Cl^- + 3H_2O}$

$\ce{ClO_{3}^- + 6I^- + 6H_3^+O \leftrightharpoons 3I_2 + Cl^- + 9H_2O}$


texts: Chemical Potential in the Fluorescent Molecule

texts:
I'm reading this paper, which states that the chemical potential $\mu$ is determined by the steady-state balance of up and down transitions in a fluorescent molecule. I am happy with this interpretation. But what I don't know how to verify is the next statement:
"For a high-quantum-efficiency fluorescent molecule illuminated at the earth surface, $\mu$ is usually $0.6$ or $0.7$ times $h\nu$ at the centre of the absorption band".
How would I show that $\mu$ is usually $0.6$ or $0.7$ times $h\nu$ at the centre of the absorption band?


texts: Can solutions of polar covalent compounds conduct electricity?

texts:
I learned in class that solutions of polar covalent compounds are weakly conductive, while ionic solutions are strongly conductive.

But I'm getting different answers online. According to this lecture, "They do not conduct electricity in the liquid state, or when soluble in water, do not conduct electricity in aqueous solution."

I saw in lab, however, that a dextrose (D-glucose) solution weakly conducted electricity, and so did that of levulose (D-fructose).

So can solutions of polar covalent compounds conduct electricity? If so, how? Since it's covalent, it's not like anything can dissociate to form ions, right?


texts: Perfluorobutanesulfonic acid (PFBS) Safety and Toxicity

texts:
I was wondering if anyone had any experience with PFBS or PFOS (perflurooctane sulfonic acid)?
I am thinking about trying to purchase some of these fluorosurfactants in bulk in order to (hopefully) use as a solvent.  However, I have read that PFOS is now banned due to the bad effects on people's health and the environment.  However, they claim that PFBS is a little better (half like of ~1 month in humans compared to ~5.5 years).
So, I was wondering how terrible it would be to be dealing with the pure liquid on a daily basis, with the use of some gloves and a hood. The hood isn't great in terms of suction, but it's at least something. I should also add that the hood is of course open to the air, so there's moisture in the air.
I do deal with chlorosulfonic acid in the hood pretty regularly, and it isn't a huge problem, although I'm not aware of HCl getting trapped in your system for extended periods of time either.
I also hope to be contacting these liquids with chlorosulfonic acid, where I hope that no reactions will occur, but I am not so great at chemistry so I don't know if that is a fair assumption.

I also noticed that they state in the Wikipedia article for PFOS and PFBS that these substances are used in some consumer items.  So, if they are used in consumer items without degrading, how dilute do they have to be to not have strong acute or mild long term health effects?
I figure they would have to be pretty bad in order for 3M to ban PFOS, but I don't know if that was mainly in order to stop the mass use of them in consumer items.

The MSDS for PFBS states that the LD50 for mice is 430 mg/kg, and it shouldn't be contacted with any moisture in air at all  While the Chlorosulfonic acid MSDS states some similar, but more tame, statements about moisture, and it's LD50 in mice is 50mg/kg.

So, I guess my main question is, has anyone used this substance in it's pure form in a normal hood type of environment?


texts: Ionic content of different samples of water

texts:
So I was reading about impurities of in water and I have a question in mind:

So say we have Distilled Water , Deionized Water , Tap Water and Soft water which was softening using dowex resin or any other cation exchange resin.

So my question is which samples would contain anions like $Cl^-$ and $PO_4^-$ and which would contain cations like $Ca^{2+}$ and $Mg^{2+}$?

My speculation is that Tap Water would contain all the stated ions , Deionized water wouldn't contain any, Distilled Water wouldn't contain any and Softened water would contain the anions but not the cations since $Ca^{2+}$ and $Mg^{2+}$ would be replaced by $Na^+$ or so.

Thank You!


texts:
'Mercury' was included in one of the possible answers for this exam question:

Name a metal that an inert electrode could be made from.

My answer was 'platinum' which was also a possible answer, but I’m curious how mercury, which is a liquid metal, could be used as an electrode during electrolysis?


texts: Is the t-butyl carbocation more stable than the benzyl carbocation?

texts:
Various authors have different views regarding stability order of the benzyl and t-butyl carbocations.

$$\ce{PhCH2+ ; (CH3)3C+}$$

In my opinion, resonance effect dominates, so the benzylic carbocation should be more stable. But in the other case, both the inductive and hyperconjugation effects are present, which stabilize the intermediate carbocation.

What should is the correct stability order? Especially when you consider them in SN1 reactions, and what their effect on their rate is.


texts:
I want to put an action figure in orbit but I need to know how to make a secure yet not too  expensive rocket fuel engine. The design of the engine must very primitive and not too complicated.

I've read some information about hydrazine and hydrogenperoxide but it is too dangerous to use and make at a noncommercial scale. Although I studied some chemistry in highschool, I don't have so much knowledge about this matter. So far my best bet is blackpowder based fuel engine. What do you suggest?


texts: How to calculate the refractive index of mixtures?

texts: In "How to Calculate the Refractive Index of a Formulation", the article outlines a method to find the refractive index of a mixture but the sources don't lead to any evidence regarding its validity. I would like to know the name of the formula used and if it has any limitations because I haven't been able to find any techniques to calculate the refractive index of non-binary mixtures other than this article.


texts: Why are acids characterized by giving hydrogen and bases characterized by receiving it when acid and base reactions are double displacement reactions?

texts: One example of this is $\ce{HCl}$ and $\ce{KOH}$. Why would the acid not just give the hydrogen ion in $\ce{HCl}$ to form $\ce{Cl-}$ and $\ce{KOH2+}$?


texts: Why is the bond angle of sulphur dioxide close to 120°, not 90°?

texts:
Figure 1: Structural data of $\ce{SO2}$. Taken from Wikimedia, where a full list of authors is available.

As can be seen from the structural data, the bond angle of $\ce{SO2}$ is almost precisely $120°$, meaning that the σ-orbitals can be described as almost perfect $\mathrm{sp^2}$ orbitals. This means that the sulphur lone pair is also in an $\mathrm{sp^2}$-like orbital while the fourth orbital of sulphur is of p-type to build a π-system not unlike that of the allyl anion. If sulphur were in the second period, this structure would not be surprising and indeed that of ozone is very similar (see figure 2).

Figure 2: structural data of $\ce{O3}$. Taken from Wikimedia, where a full list of authors is available.

However, atoms of the third and higher periods generally have bond angles which are much closer to $90°$ as can be seen in figure 3 with the structure of $\ce{SF2}$. Typically, this is explained by their greater size which results in larger bond lengths and smaller bond angles, allowing for increased s-character of the remaining lone pairs. I myself have argued in this manner in previous answers. This should suggest an $\ce{SO2}$ bond angle much closer to $90°$, maybe around $100°$ degree as we indeed observe for $\ce{SF2}$ (see figure 3).

Figure 3: Structural data of $\ce{SF2}$. Taken from Wikimedia, where a full list of authors is available.

But sulphur dioxide’s bond angle is $119°$ as stated above. Why does sulphur adopt such a large bond angle? Which factors disfavour the approximately $90°$ arrangement?


texts: Do you say "reduce something to polystyrene"?

texts:
this question may not fit in this forum because it's about English, but biochemistry knowledge is required, so please allow me to make this thread.

When you measure the molecular weight of a polymer, you may use polystyrene standards and say "polystyrene equivalent Mw of --- is..." or "the molecular weight relative to polystyrene (standards) is..."
I have seen these usages in various articles and documents. The other day, however, I ran into an expression, "the Mw was reduced to polystyrene." I understand that it means the same thing, but my question is, do native speakers really say like this?
I googled "reduced to polystyrene" and got many hits, but it seemed many of them were written by Japanese. And when I did the same thing on Google Books, there was only one hit and the "reduced" meant "converted/changed."
So my question is, do you say "reduce to polystyrene" in this particular situation, meaning you use polystyrene standards?

Thank you very much!


texts: Is Pauling electronegativity well-defined?

texts:
Pauling's definition of electronegativity defines the difference of electronegativity between two elements.

Suppose three elements A, B, and C. Then we can calculate $ϰ_a - ϰ_b$, $ϰ_b - ϰ_c$, and $ϰ_c - ϰ_a$ independently. Is the sum of the three values always zero? Why?


texts: Why do polyoxometalates have good electrochemical/ redox properties?

texts:
Many authors are using polyoxomethalates immobilised in carbon nanomaterial as electrocatalysts for energy related reactions (ORR, HER, OER). Other metal alloys have also shown to be successful as electrocatalysts for energy related reactions.

I would like to know what makes polyoxometalates have these good redox properties, is it just because the high valency of the metal/addenda atoms that makes the multiple-electron acceptance ?

If it is possible to give an explanation based on coordination chemistry (molecular orbitals), it would be very helpful.

Thank you in advance.


texts: Difference in acid strength of oxalic acid and malonic acid

texts:
Despite very similar skeletal structures, the difference in acid strength between oxalic acid (ethanedioic acid) and malonic acid (propanedioic acid) is quite significant. What is the reason for that?

It seems that the inductive effect plays a role, but what is the explanation for the inductive effect in oxalic acid as there is same group on opposite sides?

How does the inductive effect plays different roles in both acids?


texts: Is there a reliable chemical theory that predicts pKa based on structure?

texts:
Obviously, there are general stability arguments that can be made to estimate relative pKas, such as evaluating the stability of the conjugate base of an acid, or thinking about how polarized the bond to hydrogen is.

However, is there a theory that can be absolute and account for the many exceptions to the above guidelines? What are the factors that are preventing a rigorous theory from being proposed?


texts: Calculating the pH given number of moles of HI and 500. ml of water

texts: Shouldn't we also add the volume of the HI to the volume of the water (500mL) when we calculate the molarity? My book simply divided the number of mol by 500 mL.


texts: Does an electrically conductive gas exist at room conditions?

texts:
As I know, the gases are insulators, because their particles are mainly electrically neutral, and thus there is no movable charges in them.

But maybe it shouldn't be always so, for example if a gas has a significant proportion of charged particles, I think the electrical conductivity isn't impossible. If at least one of the electrons of its particles bounds very weakly, maybe even at room conditions is it possible to have enough low resistance to be considered as a conductor.

Am I right? Does a such gas already exist? Or there is some mechanism which prohibits this idea?

Extensions:

Maybe a such gas could be considered as plasma, but I think from this aspect we could see the plasma as gas as well.
I am thinking at around 1 atm pressure and 300 K temperature, in the gas, not around the box around it. Electrostatic discharge is also problematic, because in most gases it can happen only far from the room conditions and isn't an equilibrium state.
If there is none, I am looking for the gas which is the possible nearest to the these 3 conditions (300 K, 1 atm, conductive).


texts: Law of Multiple Proportions: What is the significance of small whole numbers?

texts:
I'm new to Chemistry and in my textbook, it describes the Law of Definite Proportions (aka Proust's Law) and then goes on to describe the Law of Multiple Proportions.

The example they give is carbon monoxide and carbon dioxide, where the mass ratio of oxygen to carbon in carbon dioxide is $2.67:1$ and the mass ratio of oxygen to carbon in carbon monoxide is $1.33:1$.

I understand the above example, and I understand that when you compare them in the following way:

$2.67~\mathrm{g}$ (proportion of oxygen to $1~\mathrm{g}$ carbon in carbon dioxide)$/ 1.33~\mathrm{g}$ (proportion of oxygen to $1~\mathrm{g}$ carbon in carbon monoxide) $= 2.00$, a small whole number.

$$\frac{\text{Mass oxygen to 1 g carbon in carbon dioxide}}{\text{Mass oxygen to 1 g carbon in carbon monoxide}} = \frac{2.67~\mathrm{g}}{1.33~\mathrm{g}} = 2.00$$

My textbook doesn't describe what a small whole number is, or what it means … just that, in this example, $2.00$ is a small whole number.

What is the significance of the $2.00$?

I understand that carbon dioxide has double the oxygen. Is this where the $2.00$ plays a role?


texts:
Why can a solvent dissolve only a particular amount of solute?
If we add more solute to the solution, the number of solute particles in contact with water increases. So rate of dissolution should increase, and subsequently, the solubility product should also increase. But why do we have a constant value of solubility product?

P.s. An explanation at the particle level would be appreciated


texts: Can suspensions be separated by centrifuge or by separatory funnel?

texts:
I want to know if we could separate suspensions whose particle sizes are more than $\pu{100 nm}$ like mud by a normal centrifuge?

Could we use a separatory funnel for these situations?


texts:
My understanding says organo-metallic = organic + metallic compunds.

One already known to me is Grignard Reagent ($\ce{RMgX}$).

But would you consider $\ce{NaOMe}$ or $\ce{NaCCH}$ as an organometallic compound? Would you consider $\ce{LiOAc}$, $\ce{LiOMe}$, $\ce{LiN(Me)2}$ or $\ce{LiMe}$?


texts: What do the + and - sign of 2 lobes of the p orbital represent? I know that they are the signs of the electron's wave function but what is their significance?


texts: What is the most convenient way to prepare ferrous oxide (FeO) in the laboratory?

texts:
The Wikipedia page for ferrous oxide states that $\ce{FeO}$ can be prepared by the thermal decomposition of iron(II) oxalate, with the following reaction:

$$\ce{FeC2O4 → FeO + CO2 + CO}$$

And that the procedure is conducted under an inert atmosphere to avoid the formation of ferric oxide.

Sicius' Eisengruppe: Elemente der achten Nebengruppe: Eine Reise durch das Periodensystem states that $\ce{FeC2O4}$ should "slowly" be heated in a vacuum and then rapidly cooled down.

Both of these resources, however, omit critical information as to the preparation process. These questions remain:

At which temperature does this reaction really start occurring, and what is the ideal temperature range to carry out this thermal decomposition?
How "fast" should it be cooled down? And what are appropriate methods to do so?

I'd be very thankful for any additional information on the topic.


texts: Can aluminium form blue-colored solution in liquid ammonia?

texts: I am a high school student and in one class, my inorganic chemistry teacher told group 1 elements with the exception of lithium and group 2 elements with  exception of Be form blue-colored solutions in liquid ammonia (Mg requires an electrolytic process). What are the conditions for a metal to form a solution in liquid ammonia, and which metals (other than what I have mentioned) form blue-colored solution in liquid ammonia? Can aluminium also form such solution?


texts: I am not understanding,why do we have to subtract the charge from the atomic number while finding the number of electrons.


texts: What is an $\ce{NO_x}$ level? I have read some online - but I'm confused as what is used to calculate $\ce{NO_x}$. Reported $\ce{NO_x}$ levels by the government (where I live - Canada) have an $\ce{NO_x}$ level with the attached "On an $\ce{NO2}$ mass basis" What does that mean? I said $\ce{NO_x}$ doesn't exist.


texts:
Beryllium has other fancy applications. It is transparent to x-rays, so it's used in the windows of x-ray tubes, which need to be strong enough to hold a perfect vacuum, yet thin enough to let the delicate x-rays out.

The quote is from the book The Elements by Theodore Gray. Why is beryllium transparent to x-rays?


texts:
I have been having trouble getting decent resolution images and clear data of smooth amorphous carbon thin films prepared by RF bias assisted vacuum deposition. I was using a DLC tip in tapping mode and was able to get some data but is not exactly repeatable, with many more films to analyse acquiring results has been difficult and time consuming. With rms values ~0.125 and variation of hybridisation from CDE contour plots this may be an awkward task with the old machine we have and the point to point variation of conductivity.

Are there are suggestions for tips, scan parameters, scan modes etc. I am no expert with AFM by any stretch so any advice would be helpful

Much appreciated!


texts:
My little brother had to do this experiment at school, but couldn't finish it because of a lack of time. My chemistry knowledge isn't as well as it used to be, so I couldn't be much of an help.

There is a test tube (Tube A) filled with $\ce{CuO}$ and urea. With a glass straw, this is connected to a second test tube (Tube B), which is filled with lime water (which is if I recall correctly $\ce{Ca(OH)2}$?)

A quick sketch:

I really wanted to recreate this at home but I sadly don't have the tools for it.

The question here is: what happens when tube A is heated? (What happens to the material in tube A? What happens to tube B? What is left behind in A? etc).

My guess would be that $\ce{CO2}$ would flow from tube A to B, but I am not sure even about that.


texts: Is blending 15% methanol with petrol a good idea?

texts:
I just came to know that the Government of India is going to implement a scheme under which 15 percent methanol will be blended with petrol and which will reduce the cost of the fuel by 10 percent.

I want to know that how would this practically affect all the machines where petrol is being used as fuel? Will those machines have to be reengineered to work with the new blended petrol or would those machines work the same way they worked with normal petrol? How would their efficiency be affected?


texts:
How would you name this compound?

4-bromo-2-methylpentan-3-one
or
2-bromo-4-methylpentan-3-one


texts: Strength of intramolecular vs intermolecular hydrogen bonds

texts: Why are intramolecular hydrogen bonds weaker than intermolecular hydrogen bonds?


texts: Stereochemistry of cyclic hemiketal formation

texts:
$\hspace{5cm}$

I know that the acid protonates the carbonyl oxygen and this opens a pathway to an intramolecular cyclization reaction because the $\ce{-OH}$ group will attack the carbonyl carbon and a six-membered ring is formed.

I know that the carbonyl part is flat, and that the $\ce{-OH}$ can either attack from either the re or the si face. I'm not concerned about that. What happens to the methyl group on the wedge? Does that change depending on which side the $\ce{-OH}$ attacks the carbonyl? I am having a hard time visualizing what might happen to it.


texts: What is the systematic name of a "double benzene"?

texts:
Consider the molecule representation below. What is the systematic name of that molecule?

Could it possibly be 3,4-hex-2,6-anebenzene?


texts: If I have $\ce{HCl}$ and I put it in water, it will form ions. But, if I take $\ce{HCl}$ and put in benzene, it won't. How do you know that? If I had other substances, how would I know if it forms ions or not?


texts: Synthesis of 2-methyl-4-nitrophenol from benzene?

texts:
Benzene first reacts with the reagents $\ce{CH3Cl/AlCl3}$, to attach a methyl ($\ce{CH3}$) group to the benzene ring.

Then I suggested reacting with $\ce{OH-}$. Because the methyl group is an activator, it will cause the $\ce{OH-}$ electrophile to attack either in the para or ortho positions. In this case I suggest it will attack the ortho position. Now we have two activators, hydroxyl and methyl, but because hydroxyl is a stronger activator, the position where the next molecule attacks will be controlled by the hydroxyl group.

The next electrophile that attacks is the $\ce{NO2+}$, through the reaction $\ce{HNO3/H2SO4}$, the nitro group will attack the para position of the benzene and we get our final product 2-methyl-4-nitrophenol.

However, I am not 100% sure if the methyl group should be introduced first to form toluene or the hydroxyl group to form a phenol.


texts: In a typical band diagram of a half-metal, the band structures for electrons of up and down spin are different. Why is this so?


texts:
I know that you can't always trust Wikipedia, so I just want to check something regarding their kinetic isotope effect page.

The first example implies that $\sideset{^{12}}\ C$ and $\sideset{^{13}}\ C$ can be used to determine whether a reaction is $S_N1$ or $S_N2$:

  ...In the nucleophilic substitution reaction of methyl bromide with
  cyanide, the kinetic isotope effect of the methyl carbon, in this case
  defined as $k_{12}/k_{13}$, was found to be 1.082 ± 0.008 ... The observed
  methyl carbon kinetic isotope effect is indicative of an $S_N2$
  mechanism."

No explanation appears to be offered for this inference. I know that the reaction will not proceed via $S_N1$ because of the unstable carbocation but (how) does the KIE datum predict an $S_N2$ mechanism?


texts: I am searching for a molecule that is edible for human, reacts to liquid by generating $\ce{CO2}$ or a similar gas and that leaves behind a clear liquid, similar to sodium bicarbonate but without the milky whiteness.Any ideas?


texts: Percolation network analysis with 1H MAS solid state NMR

texts:
Assume you have a composite rubber that was produced in an extrusion process and it consists of a basic polymer with some additives.

One of the additives does not get
mixed with the basic resin but forms a percolation network in the resulting resin. Is it possible to get some quantitative information
on this percolation network using 1H MAS solid state NMR spectroscopy?

What if the percolating additive is very similar to the basic resin?
If 1H MAS solid state NMR spectroscopy is in no way suitable for such an analysis, what other methods can you think of to get some
information like this?


texts: Building a Salophen-Complex with Iron(III) and Cyanate

texts:
I prepared the compound in (1). Now I want to prepare the complex with a cyanate ligand (2).

Is it possible to prepare Fe(OCN)3 or should I form the chloro-complex first and then change the Ligand?

I searched for available salts, however there is no iron salt. There are only potassium cyanate, sodium cyanate and other salts. Is there a particular reason why iron salts are not available?


texts: Which of the following octahedral complexes absorbs the photon with the longest wavelength, λ?

texts:
I wonder which of the following absorbs photons with the longest wavelength, $\ce{[Cr(CN)6]^3-}$, $\ce{[Cr(SCN)6]^3-}$ and $\ce{[Cr(H2O)6]^3+}$.
I know the one to absorb the highest wavelength should also have the highest spin. Since all of these are coordination isomers, I think the strong-field ligands should have higher energies (making the answer $\ce{[Cr(CN)6]^3-}$).
I hope someone can clarify the relation between ligand field strength and energy. Any help is much appreciated!


texts: Rule to determine the total number of elements in a period

texts:
If each orbital can take maximum of 3 electrons, then total number of elements in 2nd and 4th periods respectively are = ?

I am not aware of the rule which helps to determine the total number of elements in a period.


texts: There are plenty of compounds out there with unknown standard molar entropies. I know that molar entropy has a strong dependance on the physical phase, molecular weight, and number of atoms. So is it feasible to use these parameters to roughly estimate the molar entropy of, for example, ammonium acetate?


texts:
Okay I ran into this question in homework.

A 100.0 ml sample of 0.20M HF is titrated with 0.10 M KOH. Determine the pH of the solution after adding 200 ml of KOH. The Ka of HF is 3.5 x 10-4?

Oh yeah its multiple choice

3.46
10.54
8.14
9.62
7.00

I've found answers to similar questions.Here

But I come into a different problem with this question. The HF and the KOH cancel out each other for they have the same amount of moles

I assume what ever we're looking at on the other side will have 0.02 moles and is an acid

HF -> 0.1L * 0.2M = 0.02 mol
KOH -> 0.2L * 0.1M = 0.02 mol
HF-KOH = 0

I beleive this means I can't use the hasselbach equation so I did this:

(M of ???) = 0.02 mol / 0.3 L = 0.667*10^(-2)
3.5*10^(-4) = x^(2) / (0.667*10^(-2))
sqrt(3.5*10^(-4)*(0.667*10^(-2))) = x

so there is another way of solving it

I have had some feed back on this reaction: "You assume the first reaction goes to completion when the Ka is not that high"

If it doesn't go to completion what do I do?!

I really just need to see how this works out and know why things are happening


texts: While extracting benzoic acid from ether with $\ce{NaOH}$ solution, an emulsion forms between the layers. On the other hand, when aniline is extracted from ether with $\ce{HCl}$ the separation proceeds smoothly. Why does the emulsion form in the former case?


texts: Are homemade batteries economically practical?

texts:
Every kid who has been to a science fair knows that you can make a battery with a lemon, a potato, a penny and a nail. I've never done this and I'm not entirely clear on how it works beyond a hazy recollection of undergraduate-level chemistry class; but I gather that you do not need to use a lemon and potato as your power source but can in fact use any number of substances willing to donate or accept electrons.

My question is this: are there any home-made batteries that can produce sufficient electrical energy that its cheaper to make them yourself rather than plug your appliance into the wall or use store-bought batteries

I realize that there are a number of variables here that might make a significant difference in whether its cheaper to use established electricity sources or create your own so for arguments sake lets say that I am trying to:
- charge a cell phone/laptop
- run a microwave long enough to make popcorn
- keep a refrigerator cold

Lets also consider the dual possibilities that I:
- live in a city apartment and have to buy all my fuels and materials
- live on my own far where I can grow as much produce as I want to devote to making batteries

If there are other good fuel sources that could be a logistic variable; let me know in the comments so I can edit the question accordingly.


texts: How to balance the disproportionation reaction of manganate anion in basic conditions?

texts:
$$\ce{MnO4^2- (aq) -> MnO2(s) + MnO4^-(aq)}$$

How would I balance this in basic conditions? I know we need to separate this into two half reactions but how do we do this if there is only one reactant?


texts: Is the electronegativity value ever used in calculations, or is it just a number assigned to each element?

texts: Does the electronegativity only qualitatively describe bond polarity, or does it have any quantitative use? Is it possible to describe electronegativity in terms of other periodic properties, like valence electrons, $Z_{eff}$, etc. (thus eliminating the need of a separately defined value)?


texts: Reaction between magnesium metal and sodium hydroxide: Does this even happen?

texts:
Came across this question in a book:

  Among aluminum, zinc, tin and magnesium, which metals (if any) will react with an aqueous solution of sodium hydroxide to displace dihydrogen?

The answer to the question is : Aluminum, zinc and tin.

Their reasoning?

  Under normal conditions, magnesium metal does not react with an aqueous solution of sodium hydroxide.

Given that the book does not go on to explain the rationale behind this one-liner, naturally my question would be: "Why not?"

QUESTION:

Why doesn't magnesium react with an aqueous solution of sodium hydroxide and release dihydrogen?

[@paracetamol thinks]

Initially, I was under the impression that they were talking about the oxide layer that forms over magnesium metal (the very reason we buff the surface of magnesium ribbons with sandpaper before igniting it), which would give the reaction a slow start. Then, the statement could've been: "Magnesium metal does not immediately react with aqueous sodium hydroxide (owing to the presence of an oxide layer)".

But earlier on in the chapter, there is explicit mention of the reaction between aluminum metal ( which also naturally come with an oxide coat) and aqueous sodium hydroxide, to form sodium aluminate and dihydrogen. There was no mention of an oxide layer hampering the reaction.

[@paracetamol thinks harder]

I then (cursorily) looked at the Electrochemistry aspect of the reaction; because whenever we're asked if a metal reacts with a mineral acid (to liberate dihydrogen), we're expected to flip open our table of standard electrode reduction potentials and say:

  Metals having a higher electrode reduction potential than that for the reaction $$\ce{2H^{+} -> H_{2}}$$ (which is arbitrarily taken as zero volts) will be able to liberate dihydrogen from the solution. However, metals such as copper, silver, mercury, etc which have a lower standard electrode reduction potential than that for $H^+$ will not liberate dihydrogen.

When I compared the standard electrode reduction potentials of aluminum, zinc, tin and magnesium, I've observed that all of them have electrode reduction potentials that are higher than the electrode reduction potential for $H^+$. Meaning, that all those metals (magnesium included) should be able to displace dihydrogen from the solution, at least, from the high-school electrochemistry perspective.
 (Yes, I know the textbook mentions an alkali in the question, but what I'm trying to point out is, that since the four metals have higher electrode reduction potentials that $H^+$, then they ought to behave the same way. So if aluminum, zinc and tin can liberate dihydrogen (as the textbook claims) then why not magnesium too?)

[@paracetamol Googles]

I Googled my question, and arrived at this Quora post. Same question as mine, but it's generated such lackluster answers, that they would only be worthy of...well...Quora. O:)

[@paracetamol bamboozled]

I can't for the world figure out why magnesium doesn't react with aqueous sodium hydroxide (if it doesn't). Anyone?


texts: Comparison of acids to dissolve phosphates

texts:
I am currently reading this German paper on the dissolution of phosphates by acids and chelants.
The authors do a "fast-test" of the dissolving power of different acids which goes as follows:

For each test, increasing quantities (10-50ml) of 0.1 n acids are
added to 100 mg of tricalcium phosphate and agitated for 1 hour. The
residue is filtrated and weighed.
For 0.1 n hydrochloric acid 20ml suffice for complete dissolution of
100mg tricalcium phosphate. Citric acid [...] shows >90% dissolution
with 40ml.

Not being a chemist I am having trouble interpreting this. What quantity is effectively being controlled by specifying 0.1 n acid? The paper is from the 60s. I thus suspect that n stands for normality but I am not sure.
What exactly is being measured?

The speed at which different acids dissolve the material? (Why then vary the volume of acid?)
The quantity of acid needed to dissolve a given of material? (Measured in what exactly? What does the volume effectively stand for? Moles?)
Something else?

Edit 1
J M's answer makes this much clearer. I still have some problems though:

Regarding normality: Does this ensure that the same concentration of protons is in each solution? I assume this is not the same as "constant PH" as some acids may be strong acids while others may be weak?

If even more citric acid was added, there would still remain 10% residue? Why did they not try with 50ml citric acid? With this test there are two variables that change: volume and residue. Does this not make it difficult to compare the results of different acids? I would understand a test like this: how much acid is needed to dissolve the material 100%. Then one could compare easily.

Regarding weak acids: Once one of the available protons from the citric acid has reacted, should not another previously non-dissociated acid molecule dissociate (to keep the dissociation proportion in equilibrium) and keep everything going to dissolve the material without any residue? Given infinite time, why do not 30ml citric acid also dissolve 10 mg of 100 mg of tricalcium phosphate?

I am still not quite sure however what the point of this test is. Should it not be reasonably easy to calculate this using the reaction equations and $\mathrm{p}K_\mathrm{a}$ of the acids? (See reaction equation below.)

Thought experiment: If not the acid quantity was the limiting factor but the amount of solution what would limit the reaction: i.e. infinite supply of acid molecules (high acid concentration) and infinite supply of phosphates but finite volume for the solution to take up the reaction product: Would the reaction be limited by the solubility of the reaction products? I assume, in this case a strong acid would be advantageous, right?

Reaction Equation
If I understand the papers I read correctly, one can dissolve 15 moles of $\ce{Ca_3(PO_4)_2}$ with 60 moles of $\ce{HCl}$ or 20 moles of citric acid (disregarding the fact that it is a weak acid?!):
$$\ce{ 15 Ca_3(PO_4)_2 + 60HCl -> 15Ca(H_2PO_4)_2 + 30 CaCl_2 }$$
$$\ce{ 15 Ca_3(PO_4)_2 + 20 CitH_3 -> 10 Ca(Cit)_2 + 25 Ca(H_2PO_4)_2}$$


texts: Wavelength of an electron removed from an atom of hydrogen

texts:
I have the following exercise:

  Determine the wavelength of an electron removed from an atom of hydrogen, in gas state, by a photon of wavelength of 45 nm.

So what I immediately thought was to apply De Broglie equation having

$ \lambda_{electron} = \frac{h}{m_{electron} v_{electron}}=\frac{h}{\sqrt {2 m_{electron} K_{electron}}}$

Ok then I thought that I need to calculate the kinetics energy of the electron.

Well if this was the photoelectric experiment with a metal we would have:

$K = h\nu - W$

But this is an atom we don't have an extraction energy W. Should I use the 1st ionization energy or is there other formula for calculating the kinetics energy of the electron.

Thanks!!


texts: Extraction of Activated Carbon from Lignin

texts: I'm currently working on a research project which involves the extraction of activated carbon from lignin. I'm already aware of the method of preparation using an alkali along with lignin products but I'm looking for more offbeat ideas that haven't been done before. Some suggestions would be great.


texts: Are dopant ions on a crystal lattice free or bonded?

texts:
This question seems simple but I don't seem to find many answers right away for this.

When you make a crystal doped with ions (like a luminescent phosphor) and the ions then become a defect in the crystal structure and still have emission lines similar to the free ion, is that ion really free? Or is it actually in some kind of bond?

I mean, if it did make a ionic or molecular bond, it wouldn't be a free ion anymore, the energy levels and the probabilities for the electron transitions would be very different, but the crystal has a luminescence that's similar to the free ion.

Of course there will be interactions, the electron transitions won't have the same probabilities of the free ion (you do see some lines of emission been strengthened, weakened  and/or shifted when you use a same ion in different crystals), but it's quite similar in the overall.

Saying the kind of defect an atom is on a lattice (like interstitial or substutional) only tells me about the geometry and array of the atoms on the lattice.

But I want to know about the chemical bonds they're making (or not).

Are they just "trapped" inside the structure by electrostatic repulsion without making an actual bond with any molecule around them?

Thanks!


texts: Use of fractional distillation in organic chemistry

texts:
Can fractional distillation be used to distinguish between:
1) d/l form of a compound
2) geometrical isomers of a compoun (Cis and Trans)


texts: How do I visualise bicyclo[4.4.1]undeca-1,3,5,7,9-pentaene?

texts:
While reading my organic chem book, I came across this compound:

Since this is an exercise question, I do not know the name of this compound.
I am unable to visualize this compound (how it looks out of the paper) as I have never come across two rings joined by a bridge-like structure, my book says it is a methylene bridge.
I appreciate your assistance in determining the structure of this compound.


texts: Tendency of formation of complexes in Group-1 elements

texts:
My book states the following:

Down the group(Group-1), tendency to form complexes decreases due to decrease in charge density$\bigg(\frac{\text{charge}}{\text{radius}}\bigg).$ This results in decrease in ion-dipole interaction between metal atom and the approaching ligand.

My logic-
There is a sudden availability of inner d-orbital while moving from 3rd period to 4th period. This can help accommodate the incoming lone pairs. So the tendency to form complexes must increase.
So combining the two facts, the trend should be irregular- decrease down till sodium, suddenly increase in potassium, and then slowly decrease till Caesium.
Can you provide any insight into the theory I have given above?


texts: When I name an organic compound, I follow a preferential order like so: http://www.masterorganicchemistry.com/2011/02/14/table-of-functional-group-priorities-for-nomenclature/ But I don't understand why this order exists. And intuitively (to me at least), a triple bond has a higher preference than a double bond... then why is the order like in the link, i.e., double bond preferred over triple bond? Is there any chemistry behind this?


texts:
what phenomenon takes place during catalytic activity of Pd and Pt during hydrogenation ?
in some books it is given as absorption,in others adsorption .some say that it is occlusion .
please help me


texts:
I tried one experiment. I started with ordinal yellow zinc screws.
The screws were sumberged in bath of two parts of $4.7\%$ solution of $\ce{NaClO}$ and one part $\ce{NaOH}$. The screws turned silverish in color. Then, I submerged them into vinegar. Vinegar turned them black. I am now wondering what actually happened. The bath of $\ce{NaClO}$ and $\ce{NaOH}$ is used to blacken the steel, but it doesn't work with zinc. The vinegar can be used to remove zinc.
But why it was black after that bath?
I was expecting that it would need another bath in $\ce{NaClO}$ and $\ce{NaOH}$ to become black.
Another control screw which wasn't in first bath was just stripped of zinc layer and got a steel color.


texts: Why does the outside of a plastic cooking oil bottle get sticky over time?

texts:
Cooking oil (I've observed it with canola oil, if that matters) is not ordinarily sticky. When I buy a plastic bottle of it, the outside is not sticky.

But when use some of it, then return after a few weeks, I find that the outside of the bottle is sticky. Why is this?

It does not appear to happen with olive oil in glass bottles.


texts: Why doesn't the particle in a ring model have a potential energy term?

texts:
I was thinking of the "particle on a ring" problem as a subdivision of a bigger problem, i.e. the hydrogen atom. While in the hydrogen atom problem, the Hamiltonian contains a potential energy term, the Hamiltonian in the "particle on a ring" problem does not.

Why is it so? What are its implications in the mathematical solution to the problems?


texts: Extracting sulphur from hot springs with medieval technology?

texts: For the sake of a dungeons and dragons game. Could sulphur be deposited on/extracted from hot springs water through evaporation or other proess?


texts: Can ML algorithms be applied to predict the products of a chemical reaction given a set of reactants?

texts:
How would the training data look like ? Would it be a set of reactions ? What would be a good algorithm to run on the data ?

Wolfram Alpha does have an interface for chemistry, but does not seem really robust. The other databases for chemical reactions seem to work on a static database.

The ultimate goal is to predict the products given a set of reactants. Any suggestions will be helpful !


texts: Predict photochemical decomposition of organic compound?

texts:
Is it possible to predict wether an organic compound will photochemically decompose?

Also, is it possible to predict the products which it will decompose into?


texts: Determining exponents in a rate law with different data

texts:
Here is the experimental data: Note all concentrations are the initial amounts

\begin{array}{cccc}
\text{Experiment} & \ce{[C2H4Br2]} &\ce{[I-]} & \text{Initial rate of formation of }\ce{I3-}\\\hline
1 & 0.127 & 0.102 & 6.45\times 10^{-5}\\
2 & 0.343 & 0.102 & 1.74\times 10^{-4}\\
3 & 0.203 & 0.125 & 1.26\times 10^{-4}\\\hline
\end{array}

$\mathrm{Rate}=k\ce{[C2H4Br2]}^m\ce{[I-]}^n$

We can determine the exponent $m$ easily because experiment one and two have the same initial $\ce{[I-]}$. However, when determining $n$, there is no data that has the same initial concentration. What the solution manual does is the following:

$$n=
\dfrac
{\ln \left(\dfrac{\mathrm{Rate}_{3}\cdot [\ce{C2H4Br2}]_2}
{\mathrm{Rate}_{2} \cdot [\ce{C2H4Br2}]_3}\right)}
{\ln \left(\dfrac{[\ce{I-}]_3}{[\ce{I-}]_2}\right)}=\dfrac{\ln \dfrac{(1.26\times 10^{-4})(0.343)}{(1.74\times 10^{-4})(0.203)}}{\ln \left(\dfrac{0.125}{0.102}\right)}=1$$

My question is, why are they multiplying the rate of the third experiment with the initial concentration from the second experiment and then multiply the rate from the second experiment with the initial concentration of the third experiment. I don't see any correlation with these numbers and how they can be used to determine the exponent.  Any thoughts?


texts: What does being an "elementary substance" mean?

texts:
Which of the following isn't an elementary substance?

Ozone
Sulfur
diamond
quartz

I don't get what elementary substance means.
By seeing the options and the word elementary, I guess it means something like pure or obtained in its original form.


texts: Bulging Li-ion battery – is it an immediate danger? What’s the likelihood of explosion?

texts:
I have a macbook battery that shows as completely dead (doesn’t hold the laptop on even for a second). It now started bulging, and in last week it inflated to about 50 % extra thickness, like this – I can see the inflated battery packs filled with gas.

How big of a danger is to keep a battery like this at home? Will the reaction stop, or will it continue and will the pressure rip through the battery packs?

If that happens, will the battery combust? Internet is full of videos of exploding batteries, but what’s the real likelihood? One in a million? Or one out of two if it swells like this?

I found an advice to keep the battery in a bucket of salty water, does that make sense (I remember that water + lithium = intensive fire)?

How are Li-ion batteries disposed of when I take them into store?

I ask here, because I couldn’t find a qualified answers on the internet, only scare articles about explosions and vague conflicting advices. Thanks!


texts: What is the name for a reaction with a solid product rising from its container?

texts:
The reaction between sugar and sulfuric acid is well known to produce a solid column of rising carbon which may leave its container.  A very similar rising column may also be produced from high temperature pyrolysis of certain organic substrates.

Is there a name exclusive to the type of reaction that produces a rising column?


texts: How to make Lithium medication from scratch

texts:
I take lithium carbonate as a medication. I was watching an "apocalypse-style" movie recently, which made me wonder how hard it would be to make my medication from scratch if I could no longer buy it. Some thoughts:

I might be able to make it from batteries containing lithium, but in an apocalypse, those might be too valuable. Maybe there are other sources of recycled lithium.
According to wikipedia, much of the world's lithium comes from brine pools in South America. I currently live on the California coast. I assume we don't have these...brine pools? Would it even be possible to obtain what I needed locally from natural sources?
I have read that lithium carbonate breaks up in your blood, so maybe any form of lithium would work, not necessarily lithium carbonate.
How would I figure out the dosage and the purity of my product? Lithium is well-known for its therapeutic level being close to its toxicity level.
What kind of equipment would I need?
How would I get my blood lithium level checks done to make sure I wasn't overdosing?

NOTE:
I'm just curious. I'm not planning on actually abandoning my cheap store-bought meds for my amateur attempts at following a recipe I read online that could likely poison me.


texts: Which side of an aluminum foil should I put in contact with food?

texts:
Aluminum foil has two sides: a matte one, and a shiny one.
My question is: which one should I put in contact with food?

Criteria are lowest risk of toxicity and best qualities for food preservation (e.g. do not favor oxidizing, or react with acid nor alkaline ingredients)

For information, I've come across these several explanations; they are however contradictory (and might not be accurate):

Both side have same properties. The difference in terms of appearance is only due to the manufacturing process. (Two foils are laminated at the same time, so each foil is in contact with the rolls on one side only — hence the asymmetrical look). In this case, we can use both side of the foil.
Aluminum foil is actually made of two layers: one of aluminum, another that is coating. The surface of the aluminum layer that is in contact with atmosphere oxidizes and turns into aluminum oxide — hence the matte side.In that case, we should use the shiny side, since aluminum oxide is not that healthy.


texts: Why doesn't Epsom salt dissolved in water act like sulfuric acid?

texts:
People take baths in it so it clearly doesn't. But if epsom salt is the salt of sulfuric acid when it dissolves the chemical ions present in sulfuric acid should also be present in the bath water and in abundance enough to melt you.. right?

I also remember that water autodissociates into hydronium and hydroxide, so my other question is why wouldn't plain water simultaneously be a acid and a base and also just melt you?

If there's a trillion (or whatever) water molecules next to your skin and even a tiny fraction of them turn into an acid and some of them turn into a base, there'd cumulatively be a lot of acid on your skin. I can't imagine adding salt which would also ionize could help things.


texts:
In lab I did several different runs to create a phase diagram for the mixture between biphenyl and naphthalene. My phase diagram is attached, just for visual purposes. My question is I'm supposed to validate my phase diagram by using the following formula to calculate the enthalpies of fusion for both compounds.

$$\left(\frac{\mathrm dT}{\mathrm dX}\right)_{(T=T_\mathrm m)} = \frac{RT^2}{\Delta H_\text{fusion}}$$
I understand how to do the math, however I'm trying to figure out where that formula comes from to better understand the relationship between the enthalpy of fusion and the phase diagram. Thanks!

A side question is where could I find an accepted value of the eutectic temperature for this mixture to compare my results with?


texts:
Why would air be considered homogeneous in its gaseous state (by Wikipedia and several other sources) even though its concentration keeps varying with time?

A homogeneous fluid as i think of it is as follows: If I take a small part of the fluid the number of particles of each kind is always the same.


texts:
I am attempting to optimize interactions for a series of random and test molecules to a protein using docking software. The software uses QM/MMGBSA to calculate free energy in joules (yes it is not a measurement but it is very corollary). Larger molecules automatically have more free energy because they have greater potential energy. I would like to divide the free energy by the amount of atoms in the molecule or the molecules total Dalton. The idea would be to normalize the energy and provide the amount of calories associated with the bond. I asked a professor at a university about measuring the efficiency of a bond in this manner and he said he was unsure what joule/mass would provide. It does appear that the amount of bond calories is able to properly classify with correct magnitudes of viability 2 positive controls and 1 negative but I need this idea to pass peer review. Is my rationalization of the joule/Dalton reasonable?

I am measuring the binding energy of azttp (AZT triphosphate), gtp (Guanine triphosphate) and AZTppppA (AZTP+AMP) on HIV Reverse Transcriptase wild type (8ICO). I am used 8 high quality conformers and independent docks with QM/MMGBSA for my negative sample (AZT+AMP), 5 conformers for my major positive sample (AZTTP) and 1 conformer for the minor positive sample (gtp). I have two or three high quality conformers through the same processes for each of my test samples.

HIV RT has a tunnel where nucleotide analogs pass through with a pocket where if a molecule binds effectively it is accepted but if it fails it is phosphorylated and excreted. I am attempting to create a metric which can be used to measure the effectiveness of a binding and allowing me to infer (only) probability of rejection. Since the window/box for the docking is small and does not change for each test subject I would like to consider HIV-RT a constant.


texts: There is a formation of silver mirror in the silver mirror test. why does the silver does not precipitate, it forms the mirror in the silver mirror test? Is there any test that copper can form mirror? Why silver can form silver mirror but copper cannot?


texts: What are the states of HX when reacting with alcohol and alkenes respectively, and Br2 when reacting with benzene?

texts:
I couldn't find this in any textbooks, so I guess I will ask this here. What is the physical state of $\ce{HX}$ when reacting with alcohol (nucleophilic substitution) and alkenes (electrophilic addition) respectively?

For electrophilic substitution of benzene with bromine, what is the state of bromine?  (e.g. aqueous, liquid, solid)

If possible, can you explain why they have the particular state?


texts: In a nucleophilic substitution reaction, does the other atom to which the nucleophile is bonded matter?

texts:
For example,

1-bromopropane + $\ce{NaSH ->}$ Propanethiol + $\ce{NaBr}$
vs.
1-bromopropane + $\ce{H2S ->}$ Propanethiol + $\ce{HBr}$

Which is more valid, and why? Or are they equally valid?


texts: Henry's law and O2 concentration in alveoli blood

texts:
Can Henry's law be applied to find $\ce{[O2]}$ in alveoli blood? This kind of question appeared in an another forum and I've been struggling to find a definitive answer. My initial thought was 'no', because Zumdahl's Chemical Principles book says that

  Henry's law is obeyed most accurately for dilute solutions of gases that do not  dissociate or react with the solvent. $\ce{O2}$ will bind to the haemoglobin in the blood. Given this reaction in the solvent, $\ce{O2_{(g)}}$ in blood does not follow Henry's law.

However, a quick google search turned up multiple sources that use Henry's law directly to find the dissolved oxygen concentration (which is about $2\%$ of total oxygen):

http://www.umich.edu/~projbnb/cvr/O2transport.pdf
https://www.ncbi.nlm.nih.gov/books/NBK54103/

What I failed to understand is why the dissolved oxygen is linearly proportional to the partial pressure while the oxygen dissociation curve is not. Is there something I'm missing?


texts: Hybridisation of carbon atom in cyclopentadienyl anion

texts:
How do I figure out the hybridisation of the carbon with the negative charge?

One logic is that it is an $\mathrm{sp^3}$ carbon because there are 3 sigma bonds and 1 lone pair around it.

Another reasoning, though, is that it is $\mathrm{sp^2}$; we don't count the lone pair, because it is in conjugation with the double bonds.

What is the correct explanation?


texts: To find the value of x in a metal chloride MClx

texts:
A solution containing 0.1 mol of a metal chloride MClx requires 500 ml of 0.8 M AgNO3 solution for complete precipitation. The value of x is:

(a) 1
(b) 2
(c) 4
(d) 3

Please answer with an explanation.


texts: Out of the given reagents, find the ones to be used to convert benzene to p-aminophenol

texts:
$\ce{Br2/FeBr3}$
$\ce{CH3Cl/AlCl3}$
$\ce{KMnO4}$
$\ce{HNO3/H2SO4}$
$\ce{NBS}$/hv
$\ce{NaOH}$
$\ce{Sn/HCl}$
$\ce{NH4SH}$
$\ce{NaBH4}$

I'm able to get the amino group onto the ring by using 4 and 7.
But I have no idea how to get $\ce{-OH}$ in para position (also specify the order).


texts: Identifying the D/L form of any aldose or ketose in cyclic form

texts:
I understand that the compound above is  a ketose because it has a furanose ring. But, how do we know that it is a "D" form?

  Is there any general rule by which I can identify if any given aldose/ketose is in D/L form?


texts: Is there a crystal structure of ammonia in ionic form?

texts: Like solid $\ce{PCl5}$, does solid $\ce{NH3}$ exist as $\ce{[NH4+][NH2-]}$ (i.e. ammonium amide)?


texts:
How were the properties of bile acid sequestrants like cholestyramine discovered? The earliest reference to the chemical I could find was the following article which does not discuss the history of the drug:

Glueck CJ, Fallat R, Tsang R. Pediatric familial type II hyperlipoproteinemia: therapy with diet and cholestyramine resin. Pediatrics. 1973; 52:669-79. [IDIS 37416] [PubMed 4355362]

Does this kind of drug exist in nature or is it purely synthetic?


texts: Is there a single or double bond between S and O in propanethial S-oxide?

texts:
I am doing some research on propanethial S-oxide, a chemical produced by onions. I am trying to find out whether they have a single or double bond between the sulfur and oxygen atom. I have seen both from different sources, simply search it up on Google Images. Is this because there is resonance going on? Also is this considered a sulfinyl functional group (I am guessing no because it cannot be on the end of a chain)?

In addition, is the C double-bond S part in this molecule considered a thial functional group? A Google search indicates that the atom bonded to the sulfur must be a hydrogen for it to be a thial. If not, what type of functional group (if any) exists between the C, S, or O?


texts: Is it possible to calculate energy of electron in any orbital and atom in Schrödinger wave model theory?

texts: Is it possible to calculate the energy of electron in any orbital and atom in the Schrödinger wave model theory? If so, how? E.g. energy of the $3s^2$ electron of the $\ce{Na-}$ ion.


texts: The difference between one pot synthetic method and one step reaction

texts: I often read in the papers of organic synthesis that the reactions can be carried out in one-pot method, and the others can be realized in one-step. I want to know the difference between one pot and one step in organic synthesis.


texts: Can I change viscosity of an HDPE polymer?

texts: I want to make composite with HDPE and wood, but when I melt it I have problem to mix them, because this polymer have high viscosity.


texts: How to calculate percent error for absolute zero?

texts:
In chemistry lab, we did an experiment with water of various temperatures to extrapolate a value for absolute zero based on experimental pressure values for water at different temperatures. Naturally, the data is a little off -- even though absolute zero is $0 K$, my extrapolated value is about $15 K$.

One of the questions in the post-lab asks us to calculate percent error, and I'm a little confused. I thought (and this post confirms) that percent error was calculated by dividing by the expected or "actual" value. In this case, however, the actual value is $0$, and you can't divide by zero.

How do you calculate percent error for absolute zero?

Using Celsius values doesn't really make much sense to me, because the Celsius scale is not absolute; $-273.15$ is essentially an arbitrary number.


texts: How phenyl shift is possible in Benzil-benzilic rearrangement?

texts: We know C-C bond is much stronger than C-OH bond (because similar sized atoms have maximum overlap)as in case of phenyl-cabonyl carbon bond. Also due to resonance there is double bond character in phenyl-carbon linkage.Then how does that bond break to give phenyl shift?


texts: Why a catalyst is not consumed in a reaction when all steps are reversible?

texts:
It is said that a catalyst speeds up the rate of a reaction but is not consumed (assuming no side reactions take place). Suppose we have the following reaction:
$$\ce{A + B <=> C} $$
catalysed by $\ce{X}$ in the following steps:
$$\ce{A + X <=> A-X} \tag{1}$$
$$\ce{A-X + B <=> C + X} \tag{2}$$
Each step is reversible so every step has an equilibrium constant $K$. So an amount of $\ce{X}$ should be present as the intermediate $\ce{A-X}$ even after the catalysed reaction has reached equilibrium. That means that the amount of catalyst that we have added to catalyse the reaction is not the same after the reaction has reached equilibrium. So why we say that a catalyst is not consumed through the reaction?


texts: Does the van der Waals force not affect the alkali metal 's trend of decreasing melting points down the table?

texts: Melting and boiling points increase further down the halogen group, but they decrease further down the alkali metal group. I know that the former's trend has to do with the van der Waals force, but I don't understand why it is not applied to the alkali metal group. Please explain why the halogens are affected by the van der Waals force and the alkali metals are not.


texts: How are ions transported in solid state electrolytes?

texts:
Consider an inorganic solid state electrolyte in a solid state Li-on battery. It being solid means that the atoms or ions that make up the solid itself are not mobile. Then how do the ions move through the solid electrolyte to reach the electrodes when charging/discharging.
Moreover, is there an electrode potential between the cathode and the solid electrolyte in a solid state battery? If there is, what causes it? I mean, usually, electrode potential is the result of the lithium metal atoms in the cathode and the lithium ions of the electrolyte solution forming an equilibrium (Li ⇌ Li+). In case of solid electrolyte, all of the ions that makes up the electrolyte is stationary. So the solid electrolyte does not have Li+ ions on its own and thus there are no Li+ ions in the solid electrolyte to form an equilibrium with the lithium atoms of the cathode.
Please correct me if my knowledge is wrong anywhere. Thank you for your time.


texts: Why does increased conjugation in a molecule cause the wavelength absorbed to decrease (i.e. why does a red-shift occur)?

texts:
I was recently looking at a paper about novel organic dyes for efficient dye-sensitized solar cells and one point the authors made was that out of the two dyes mentioned the one with a larger pi-conjugated system had a red-shift compared to the other one.
I understand that a larger pi-conjugated system would increase the stability of the molecule and decrease the gap between the HOMO and LUMO energies, but how would this cause a red-shift?


texts: Why is Retention factor for Iodide greater than Bromide?

texts:
I did a separation of Bromide and Iodide ions using paper chromatography technique for 0.3% solutions of Bromide and Iodide of sodium. I got the  Retention factor equal to ~0.71 for Iodide and ~0.47 for Bromide.
So, I want to ask if ion size is playing any role in deciding this retention factor? Or, is there some another perspective that I am missing here? Specifically, what is the reason for this difference?


texts: Fermentation of different types of sugar

texts: I'm searching for the difference in the fermentation of muscovado sugar, honey and sugar cane. I have used a specific microbiota to to ferment these three types of sugar and have to explain why I've got different results regarding acetic acid and ethanol production in the final beverage, as well as different amounts of sucrose, glucose and fructose in same.


texts:
Nitrogen dioxide is dimerized to form dinitrogen tetroxide according to the equation
$\ce{2NO2 -> N2O4}$. How do two molecules of one compound fuse to form another?


texts: Is supercriticality dependent on partial presssure, or total pressure?

texts:
Supercritical CO2 is commonly used as a solvent in organic chemistry (notably in industrial processes like decaffeination). I presume that in such cases, the CO2 is typically pure, or very close to it.

But suppose you had a mixture of, e.g., 50% CO2 and 50% nitrogen. Pure CO2 becomes supercritical at approximately 31C and 73atm; particularly in terms of its solvent properties, would the CO2 in that mixture also demonstrate supercritical properties at 73atm total pressure, or would it be necessary to double the total pressure, producing 73atm partial pressure of CO2? Or is the interaction more complex than that, with mixture of CO2 and N2 having a joint critical point different from either single gas?


texts: Estimating protein binding and disassociation

texts:
I don't have a background in the area of drugs or pharmacokinetics/Pharmacodynamics but I am trying to understand about protein binding. I was going through this paper.

If $C_b$ is the concentration of the bound drug

$C_f$ is the concentration of the free drug

$C$ is the total drug concentration

$P$ is the concentration of protein binding sites (bound and free)

$K_d$ is the disassociation constant of the drug protein complex

For a one compartmental model the free drug can be found through:

$C_f=\dfrac{-(P+K_d-C)+\sqrt{(P+K_d-C)^2+4 K_d C}}{2}$

The assumptions used in this derivation are:

Binding occurs only to plasma proteins and follows simple
saturation kinetics. The binding process can be described by a single
macroscopic dissociation constant.
Binding equilibrium is achieved virtually instantaneously with
respect to distribution and elimination.
Aside from binding, all other processes (ie., distribution and
elimination) are linear.
Distribution and elimination processes operate only on free
drug.

My question is in how to determine the parameter values of $P$ and $K_d$.
The article has given certain properties of the drug but not a way in how these parameters are found.

The given details on a drug are:

1.The drug has a molecular weight of 150.

Drug binds only to serum albumin, whose concentration is 4.4% and whose molecular weight is 67,000.
At sufficiently low drug concentrations, the drug is 89% bound.
The distribution volume is 50 ml./kg.
Free drug has a half-life of 30 min.

Using these details is there a way to estimate the parameters of $P$ and $K_d$ and if so please explain how they can be derived.


texts: Why does ethanol have a stronger cooling effect on the body than water?

texts:
Why does ethanol have a stronger cooling effect than water (i.e. it feels cooler when dropped onto one’s hands) even though water has a higher heat of vaporization compared to ethanol?

If we drop a unit amount of both ethanol and water on two body surfaces (both at same temperature), which substance will lower the temperature of the surface more after complete evaporation?


texts:
Various sources such as https://news.ycombinator.com/item?id=7679154 speculate that graphene will combust at higher temperatures.

Is this true? Is the flash point/ temperature of combustion for graphene known?


texts: Selectivity in aldol condensation of 7-oxo(6,6-²H₂)octanal

texts:
I am supposed to find the product of the following reaction:

I know that six-membered rings are more stable than five-membered rings, but the C-D bonds are stronger, so it confuses me where will the attack happen.


texts: Can diamond be grown on copper wires using chemical vapor deposition techniques?

texts:
I am asking this as a follow-up to another question I asked earlier. It is regarding how to make higher voltage transformers. Diamond is a good dielectric material and would be good for using as a dielectric barrier for wires wound into transformers. However, diamond is much too brittle to coat the wire and then wind, so my question is this:

Can diamond be grown on copper wires wound into a transformer shape using chemical vapor deposition techniques?


texts: Reactivate dried up ink of ballpoint pens

texts:
According to this question, ballpoint pens start writing intermittently when the ink is drying up. In other words, the ink is becoming more viscous and does not flow any more.

Are there ways to make it flow again?


texts: How to charge titanium dioxide particles for a DIY e-paper capsule?

texts:
I'm trying to make a single e-paper capsule (1 cm × 1 cm) at home. At first, I tried to charge the $\ce{TiO2}$ particles by putting them in $\ce{H2O}$ with $\ce{NaOH}$ and then putting that whole solution in baby oil, but it turns out I shouldn't have any water in the whole process. I also tried adding a surfactant (liquid soap) but it also has water. Water is a problem because it forms micelles around the $\ce{TiO2}$ particles and prevents proper spreading. How do I charge the $\ce{TiO2}$ particles without water (and $\ce{NaOH}$). What oil-soluble surfactant I can use that doesn't contain water? Does anyone know any details about how the chemicals of the e-paper display work?

I researched a lot and it turns out the big companies use complicated processes and mixing different chemicals with expensive lab machines to produce the desired charged $\ce{TiO2}$ solution. Is there any way I can do it at home?

From the abstract of an article describing a TiO2 preparation protocol$^1$:

  It was found that highly charged TiO2 particles could be prepared by milling 1.0 g of TiO2 particles, 0.5 g of silane additive as a charge controlling agent and 0.5 g of dispersant in 100 mL of cyclohexanone as a suspension fluid for 8–10 h using pot mill, followed by treatment with 0.4 g of acetic acid.

What is a common silane additive used as a charge controlling agent? And what would be an appropriate dispersant here?

Can anyone here recommend additional preparation protocols, perhaps something that might be considered a "standard recipe"?

References

Park, Lee, Park, Jin, Choi, Hae, Han, Yoon Soo, Kwon, Younghwan, Choi, Hyung. Fabrication of charged particles for electrophoretic display.
Current Applied Physics 6(4):644-648.


texts: Why does ozone have higher entropy than oxygen?

texts:
$$\ce{3O2(g) -> 2O3(g)} \qquad \Delta H^\circ (\pu{298 K}) = \pu{+142 kJ mol^-1}$$

Since the RHS of the equation contains less number of gaseous molecules, naturally I expected the $\Delta S$ to be negative. In fact, while solving many thermodynamics questions relating to sign of $\Delta S$, I used this concept to get the correct answers (we were even taught this, that's why).

However, this appears to be an exception as this reaction does happen (thermodynamically possible due to negative $\Delta G$). It's given in my textbook (page 186, NCERT Chemistry) and the textbook accounts for it stating that the reaction has $\Delta S > 0$ without mentioning the reason for it.

Why is the entropy of ozone more that that of oxygen? Is there any simple explanation to it?


texts:
I am trying to use TGS 2602 sensor of air contaminants. I would like to test if my circuit is working as intended. For that purpose I need to generate fumes of one of the gases the can be detected by the sensor.

I thought that I would go for ethanol. I tried holding vodka soaked cotton ball near the sensor - to no avail. Later on I tried spilling vodka around the circuit and placing more vodka soaked cotton balls around. I also covered the whole thing with a cardboard box (with gaps at the bottom between table and the box). Again there was no considerable effect. Vodka is essentially ~40% ethanol and water mix (by volume).

Can you say by that short description that I managed to generate between 1 and 100 ppm ethanol gas? If not, can you propose a robust and safe method of producing such a gas?

Please be aware how the sensor looks. It is enclosed in a metallic case with small holes on the top surface.


texts: Cyclisation of acetone on reaction with conc. H2SO4

texts:
Mechanism for reaction of acetone with concentrated $\ce{H2SO4}$:
The product is supposed to be mesitylene, and on various sites I found the reason behind it to be aldol condensation And some sites provided me with unusual products( as for a high school student)

Does this reaction have a reasonable reaction mechanism or do we just have to mug this up?

What are these cyclisation kinda mechanisms called?

Do they have a category that is to be understood?


texts: What is the correct way to clean spectrophotometry cuvettes?

texts:
The lab I started working in has a spectrophotometer with cuvettes. The cuvettes need to be inspected and cleaned regularly. The senior people in the lab are in disagreement as to the correct procedure for cleaning them. Some recommend soap and a bristle brush with running water, others just suggest leaving them to soak in an ethanol solution.

The question is twofold;

a) Is there any risk that the brush will scratch the glass?

b) Is there any advantage to the soap method? If not, I am wasting an hour of my boss' time and money.


texts: Can you heat Bismuth crystals to reset the oxide layer for new colors?

texts: I'd like to get a bismuth crystal with small structures and deep blue colors for a ring I want to make. I can find these properties in different crystals online but never together. Can I just take a crystal with the right shape and blowtorch it to create a new oxide layer? Would I first have to chemically remove the thin oxide layer?


texts: Why is methyl parathion less toxic than ethyl parathion?

texts:
According to the PubChem pages on ethyl parathion and methyl parathion (pages 11 and 12 of the toxicity section, respectively), methyl parathion is significantly less toxic than ethyl parathion. The difference in LD50 values depends on the route of administration and the animal to which the pesticides were administered, but it is significant.
For instance, parathion has an intraperitoneal LD50 in mice of 3 mg/kg, the LD50 for methyl parathion administered in the same way is 5.4 mg/kg, making it almost two times less toxic than parathion. Methyl parathion differs from regular parathion in that, in methyl parathion, the ethyl groups are replaced with methyl ones.
How does this structural difference contribute to a difference in toxicity? Why is methyl parathion significantly less toxic than its ethyl analog?


texts: Activity Coefficients from Electrode Potentials

texts:
Lets say we want the activity coefficient of $\ce{Cu^{2+}}$ ions in solution. Would we simply setup one half cell of a $\ce{Cu}$ electrode in a known concentration of $\ce{CuSO4}$ and then connect this to a Standard Hydrogen Electrode.

Using the standard electrode potential of the reaction $\ce{Cu^{2+} + 2e-  ->  Cu}$  and the Nernst equation could we determine the activity coefficient of $\ce{Cu^{2+}}$ ions ?

Is this all I would need to do ?


texts: The effect of temperature on equilibrium

texts: If the forward reaction is exothermic, and the reverse is obviously endothermic. I getting rather confused. If the temperature is increased the equilibrium will want to decrease the temperature. However, (this is the bit im struggling with) if I want to decrease the temperature wouldn't you shift it to the left? As the reverse reaction is endothermic, and an endothermic reaction causes a decrease in the temperature or is this incorrect?


texts:
You might have seen in the short 2 minute video here: billionsinchange.com/solutions/limitless-energy that the Billionaire Founder (net worth $4 billion) Manoj Bhargava talks about creating cables from graphene to conduct heat from the underground sections of the earth to the surface.

But as per the properties of graphene, it is only a good conductor if the number of layers is one or very few. Once you start stacking it up, it is just normal graphite and it's conductivity gets reduced.

What's proposed in the video is a cable made from graphene. My question is how is it possible to make a graphene rope without stacking up graphene layers (and thus ending up with graphite) or without converting it into nanotubes?

I would also like to know why stacking up graphene reduces it's conductivity? Why don't the layers behave independent of each other?


texts: How is enthalpy change equal to heat supplied at constant volume?

texts:
We know that:

$$\begin{align}
H &= U + pV \\
\Delta H &= \Delta U + \Delta (pV)
\end{align}$$

Now,

If $p$ is constant,

$$\begin{align}
\Delta H &= \Delta U + p\Delta V \\
&= q_p + w + p\Delta V \\
&= q_p \qquad\qquad  \text{(since } w = -p\Delta V\text{)}
\end{align}$$

If $V$ is constant,
$$\begin{align}
\Delta H &= \Delta U + V\Delta p \\
&= q_V + w + V\Delta p \\
&= q_V + V\Delta p \qquad \qquad \text{(since } w = -p\Delta V = 0\text{)}
\end{align}$$
We also know that at constant $V$,

$$\Delta U = q_V$$

Now my question is that: my book says that at constant $V$, $q = \Delta H = \Delta U$, which I think is false, since I obtained $\Delta U = q_V$, but not $\Delta H = q_v$.

Please tell me where am I going wrong?

Here is a link to the chapter.

Please refer to Pg 161, right column, first paragraph.

Link to chapter: Thermodynamics


texts: When titrating a weak acid should only undissociated acid molecules be considered?

texts:
Let's say we do the titration of a weak acid (acetic acid in this case)  and a strong base (sodium hydroxide) represented by the following equation:
$$\ce{CH3COOH + NaOH -> CH3COONa + H2O}$$

My question is that, since $\ce{CH3COOH}$ is partially dissociated, does $\ce{NaOH}$ react  only with the partially dissociated part or the complete acetic acid solution?


texts: How to dialkylate a cyclohexene, and convert a carbonyl to an alkene?

texts: I'm trying to design a synthesis of D from C. All I can think of is using $\ce{Me2CuLi}$ to add the methyl group to the alkene. I thought maybe then if isobutyl bromide was in the reaction mixture when $\ce{Me2CuLi}$ pushed the negative charge onto the oxygen and it came back down that could do an $\mathrm{S_N2}$ with isobutyl bromide, but I've never seen that before. Then for converting the carbonyl to an alkene I have no idea.


texts:
I recently came across this question in a book.

  Among the metals $\ce{Cr}$, $\ce{Fe}$, $\ce{Mn}$, $\ce{Ti}$, $\ce{Ba}$ and $\ce{Mg}$, the one that cannot be obtained by reduction of its metal oxide by aluminum is:-
  (a) $\ce{Cr}$
  (b) $\ce{Fe}$
  (c) $\ce{Mn}$
  (d) $\ce{Ba}$
  (e) $\ce{Mg}$

So, one method to answer this question is by Ellingham Diagram and to remember the values of $\Delta G^0$(Gibbs free energy change) for oxidation of each metal into its oxide and it's variation with temperature.

So, we can see that $\Delta G^0$ for oxidation of $\ce{Al}$ is much lower than other metals except $\ce{Mg}$ at lower temperatures. Thus, $\ce{Al}$ can reduce other metals except $\ce{Mg}$ at lower temperatures.
Thus, the answer is (e) $\ce{Mg}$.
So, this was the answer based on the experimental data for metals.
Couldn't we determine this answer theoretically as we can't remember all these data?


texts: What I fail to understand is why does trans isomer contain $2$ $\ce{Cl}$ at axial positions but $2$ $\ce{NH3}$ are not taken to be so. Isn't the two $\ce{NH3}$ in the trans isomer in the picture cis to each other?


texts: Which way does this reaction between NaCl and acetic acid naturally proceed?

texts:
Here is the overall formula:

$$\ce{CH3COONa  + HCl <=> NaCl + CH3COOH}$$
(sodium acetate + hydrochloric acid $\ce{<=>}$sodium chloride + acetic acid)

Which way does the above reaction naturally proceed? I've tried Googling this, but different sources seem to suggest contradictory answers, and I can't really tell what's correct.


texts: Is it true that iron (Fe 0+) cannot exist when there's water around?

texts:
So somebody told me that iron metal (zero charge) cannot exist at all when $\ce{H2O}$ is present because it will all turn into rust.
How is this possible? Isn't there some sort of equilibrium?
Does it have to do with the pH/pE? And if iron really can't exist, then what happens if I put an excess of iron into the water?


texts: What is the product of the chemical reaction between phenol and ferric chloride?

texts:
The chemical reaction between phenol and ferric chloride is a test for the presence of phenol. They react with each other to produce a violet complex. However, the reaction is given differently in different links:

$$\ce{3ArOH + FeCl3 → Fe(OAr)3 + 3HCl}$$

source 1 , source 2
$$\ce{6 ArOH + FeCl3 -> [Fe(OAr)6]^3- + 3H+ + 3HCl}$$
source

I guess the 2nd reaction is the appropriate one because it shows the formation of a complex, $\ce{[Fe(OAr)6]^3-}$. How could  $\ce{Fe(OAr)3}$ be considered a complex? It should act like a ionic salt like $\ce{Na^+C6H5O^-}$  or $\ce{NaOAc}$.

So, what is the correct product of the reaction; $\ce{[Fe(OAr)6]^3-}$ or $\ce{Fe(OAr)3}$?


texts: What is the structure & hybridization in singlet and triplet nitrenes ..?

texts:
What is the structure & hybridization in singlet and triplet nitrenes .. some sources say triplet nitrene has sp hybridization with two p orbitals :

http://burton.chem.ox.ac.uk/handout-2.pdf
http://www.egyankosh.ac.in/bitstream/123456789/15753/1/Unit-9.pdf
http://textofvideo.nptel.ac.in/104105038/lec21.pdf
https://d-nb.info/1160442363/34

and some say it has an sp2 hybridization :

https://pubs.rsc.org/en/content/articlehtml/2014/cc/c4cc03016h

https://slideplayer.com/slide/8825904/


texts: Most reactive site for electrophilic aromatic substitution

texts:
I was given a problem in which I had to identify the most reactive site for electrophilic substitution out of the positions 1,2,3,4 (shown in the figure).

My Approach:  Upon drawing the resonating structures of the molecule, negative charge appears on position 3 and 2.

In the resonating structure in which the negative charge is under 3, there is a positive charge under -NO2 group making that structure less stable.
This does not happen with the structure in which the negative charge is under 2.

So I concluded that 2 would be the most reactive site.
But the answer given is '4'.

What is wrong in my reasoning?


texts:
My kids and I were playing with a small plasma globe like this:

After touching it we all noted a faint smell like that created by other high voltage static discharges, which I always understood to be the smell of ozone.

So I guess this is actually two questions:

Is the smell associated with static electric discharge in fact ozone?
Do plasma globes like this create ozone?

(Presumably if the answer is "yes" then it would not be a good idea to leave one of these operating for an extended period in a closed space like a child's bedroom!)