texts: Which of these functional groups is soluble in aqueous HCl and/or NaOH?

texts:
http://pastpapers.papacambridge.com/view.php?id=Cambridge%20International%20Examinations%20%28CIE%29/AS%20and%20A%20Level/Chemistry%20%289701%29/2015%20Jun/9701_s15_qp_42.pdf

I need some help to solve Q6 biii) of this paper. I got the correct answers thinking that if something reacts with an acid or base, then it dissolves in them. But then I realized that amides and esters also react with both ( though heat is required, so that may be why they aren't said to be soluble ), and I also realized that in general my 'dissolves = reacts' notion is very flawed. So I discarded this concept, and tried to work on it fresh, but I am now very much stuck.

My approach before was this :
Esters do not dissolve in cold aqueous bases or acids, nor do amides or alcohols.
Amines dissolve in aqueous acids. Phenols and Carboxylic acids dissolve in aqueous bases.

From the molecular formula, we know that each compound contains either an Amine or an Amide functional group, so the rest of it is simply working out which combination fits which functional groups. Thanks!


texts: What should be IUPAC name of given compound (see image)?

texts:
I think the name should be 1-carbamoylpentane-3-sulphonic acid, but the answer sheet mentions it as 2-carbamoylpentane-3-sulphonic acid:

Can anyone please explain why the chain starting with methyl group is considered parent chain instead of one starting with amide?


texts:
The $K_\mathrm{a}$ for $\ce{HCN}$ is $6.17 \cdot 10^{-10}$ with a $\mathrm{p}K_\mathrm{a}$ of $9.21$

Thus, the cyanide ion is a strong base.

Also, the cyanide ion is a good nucleophile.

So in the reaction of alkyl halides with $\ce{KCN}$, a mixture of products must be formed depending on the solvent and alkyl group.

However my text suggests that the reaction  proceeds only via $\mathrm{S_N2}$.

Shouldn't the product formed depend on the alkyl group, say for a tertiary alkyl group, the reaction can go via $\mathrm{S_N1}$ mechanism for polar protic solvents and via $\mathrm{E2}$ for polar aprotic solvents and as the cyanide ion is strong base, the reaction is unlikely to go via $\mathrm{E1}$ and due to steric factors $\mathrm{S_N2}$ is also ruled out.

Also is there any  difference if we use $\ce{KCN}$ or alcoholic $\ce{KCN}$?


texts:
In a previous post about how pyridine failed to move much from the baseline of a TLC, I was told to look into "silanol activity". However, I was unable to find a textbook-style description. All the articles I've seen where silanol activity was discussed assumed it was a known prerequisite.
Could anyone explain silanol activity, or direct me to an online explanation please?
Furthermore, if it is referring to an acid–base reaction, would that imply that what I'm seeing on the TLC is no longer pyridine, but rather $\ce{C5H5NH+}$?


texts:
Which of the following is the strongest oxidizing agent?
A) $\ce{I2}$
B) $\ce{Ag^2+}$
C) $\ce{Cu^2+}$

The answer is apparently B) but I think it has to be A) because it is the only non-metal which actually wants to lose electrons. I just wanted to confirm whether it’s an incorrect solution or my own understanding is wrong.


texts: Why does the C-C bond break earlier than the C-F bond in the pyrolysis of perfluroethane?

texts: According to me $\ce{C-F}$ bond is highly polar and thus is a weaker bond as compared to $\ce{C-C}$. Hence, $\ce{C-F}$ should break first in the pyrolysis of perfluroethane. Instead, in J. D. Lee, it is stated that $\ce{C-C}$ bond will break first. Why?


texts: When CO is the by product of certain reactions( burning of coal under limited air supply), how is it treated before releasing in the atmosphere or is it converted to some other form? Can that byproduct be used to synthesize some other compound ?


texts: Other than ultracold lithium gas, are any ferromagnetic or magnetic gasses known or hypothesized?

texts:
I'm dealing with an interactive work of fiction right now, and one proposal is to combine two types of puzzles with a magnetic gas. I know that fermionic $\ce{^6Li}$, when cooled below $\pu{1 K}$, has shown verifiable ferromagnetic properties, but that is far too cold to be applicable to the work's setting.

(I'm only willing to suspend the user's belief so much.)

I know that on heating above the Curie temperature for a material, magnetic properties dissolve; but what that temperature is varies quite a bit. (I've seen them between $\pu{90 K}$ and $\pu{1400 K}$, which is pretty radical.) Has anyone yet discovered another molecule that remains magnetic in a gaseous phase? Are any of them at least hypothesized?


texts: IUPAC naming of 1,2-disubstituted cyclohexane derivative

texts:
I'm facing the challenge of naming this molecule:

We have to name it as an alkyl-substituted cycloalkane, since the ring has more carbons than the longest substituent (isopropyl). My questions:

When numbering carbons on the ring, we can start counting from either the methyl group (1-methyl...), or the isopropyl group (1-isopropyl...). Which one should I start with? Or do I need to start numbering with the substituent which name comes first, alphabetically?
I set the carbon number 1 on the methyl substituent, giving me the following name: 1-methyl-2-isopropylcyclohexane. However, my book says the correct name is: 1-isopropyl-2-methylcyclohexane. So the solution managed to sort the name both numerically and alphabetically. Is this what I need to do? Is the name I gave incorrect?
Which prefixes count towards alphabetically-naming a compound? Which prefixes don't? All I know is that the numeric prefixes like di- or tri- don't count. Are there any others which don't count either?


texts: Assay over 100% (L-Cysteine Hydrochloride Monohydrate)

texts:
In reading a COA (Certificate of Analysis), I came across an Assay line:

The Assay is 100.5% where "Lower Limit" is 98.5 and "Upper Limit" is 101.0

This product is L-Cysteine Hydrochloride Monohydrate.  How can the Assay be over 100%?

I have found this statement: "If the substance under test is purer than the standard, the assay comes more than 100 pct."  If that is the case, then the question becomes, where can I find out about this standard?


texts: Correctness of DSC curve for polyamid or polyester

texts:
I did a DSC on a part of an alternator car belt. We already found out that it should by a polyester or a polyamid. But then we got the following DSC curve:

How is it possible that the glass transition temperature is around 39°C for a polyamid or a polyester?


texts: Platinum-coated razor blades for making a fuel cell

texts: My daughter wants to construct a fuel cell for a school project. Budget is tight and platinum as preferred catalyst expensive. I know that Gillette razor blades are coated with platinum. Would there be a way to use old razor blades for making a fuel cell?


texts:
Can anyone explain Heisenberg's uncertainty principle and it's derivation.
Im a 12th standard student.Please make it simple enough for me to understand.


texts: What is the order of the following compounds based on polarity?

texts:
What is the order of the following compounds from more polar to less polar?

  Hydrochloric acid,
  Methanol,
  Hexane,
  Petroleum benzene

I know that $\ce{HCl}$ has the largest polarity. Hexane I guess has the less. I guess the order should be like:
$\ce{HCl}$ > Methanol > Petroleum benzene > Hexane

Is this correct? I'm not sure of the place of petroleum benzene.


texts:
Silicon dioxide, in the form of quartz, is in abundance around my local area and I would be interested in creating silicon as a separate element.
My problem is that I don't know what to react silicon dioxide with to reduce it to silicon. I have read that it can be reduced with carbon but I couldn't find any information about the temperatures this takes place at. I am also aware that a thermic reaction can take place between aluminium and silicon when mixed with sulfur but I don't have any aluminium powder.
Thank you in advance.


texts: Does the density of a liquid and gas phase of a substance(nitrogen or water) converge when reaching critical point

texts: I know that the there is no difference in density in a liquid and a gas phase of a substance after the critical point. But I do want to know if this difference in density is more continuous or if it is more like a big step when reaching the critical point? I.e if we are like 0.01 Kelvin beneath the critical point of water (with the critical pressure). Is the difference in density still big at this point or is it near zero?


texts: Temperature in the Maxwell-Boltzmann Distribution

texts:
I am attempting to generate the probability for the specific speed of a molecule using the Maxwell-Boltzmann distribution, but I cannot decide on which temperature I should use in the equation.

For example, I have a very, very cold liquid (let's say 70 K) at room temperature (we'll call that 296.15 K), but would I use the temperature of the liquid in the equation, or should I use the temperature of the air around the liquid?


texts: Taking kinetic readings for the Briggs–Rauscher oscillating reaction

texts:
I am current doing the IB diploma program where we are required to do an extended essay which is a form of a research paper on a specific subject. I chose chemistry.

I am analysing the kinetics of the Briggs–Rauscher reaction, adapting my experiment from the paper by Schmitz and Furrow [1].

The paper appears to use a spectrophotometer to measure iodine concentrations which I have tired, however the readings failed since the reaction needs to be continuously stirred. Another alternative they have used is to use an ion selective electrode to determine iodide ions in the solution however I don't have access to this.
I do have an AgCl reference electrode and was considering trying method from this YouTube video, however I lack a potentiostat and the ion-selective electrode. I was wondering if anyone could tell me any tricks on how to build this electrode if possible as I couldn't find anything online.

Alternatively, is there any other recommended way to determine the kinetics of this reaction. I would like to not have to use a stopwatch to clock the oscillations since that does not provide me with much detail.

References

Schmitz, G.; Furrow, S. Kinetics of the Iodate Reduction by Hydrogen Peroxide and Relation with the Briggs–Rauscher and Bray–Liebhafsky Oscillating Reactions. Phys. Chem. Chem. Phys. 2012, 14 (16), 5711–5717. https://doi.org/10.1039/C2CP23805E.


texts:
If 130.0 mL of 3.0×10−3 M Na2SO4(aq) is saturated with CaSO4, how many grams of would be present in the solution? [Hint: Does the usual simplifying assumption hold?]

My answer is still wrong. What have I done wrong?


texts: What is difference between H⁺ and proton?

texts: What is difference between $\ce{H+}$ and a proton?


texts: Confusing definition of the term precision

texts:
According to the textbook, we say a measurement is precise when series of measures are close to each other.

But in real use, I feel like the term is used in a different meaning.

For example, scale A weighs to cube of lead and displays 10.5g while scale B displays 10.4977g.
In this case, one say the measurement made by scale B is more precise than that of A. That is, scale B can distinguish more fine weights than A.

Isn't this usage of the word precise different from textbook definition? Please explain clearly the real usage of the term precise.


texts: What is the actual voltage to the standard hydrogen electrode and why is it used?

texts:
Why is the standard hydrogen electrode chosen to be of 0 voltage, what is its actual voltage and how could that be calculated experimentally?

Also, why is it that we cannot measure the voltage or potentials of the range of electrodes and we must use the standard hydrogen electrode?


texts: Titration with EDTA and Eriochrome black T

texts: I have a titration of Calcium Ions with EDTA. When I reach a volume of 9.6mL I the liquid turns slightly blue and after that the more I add the bluer it becomes. Now at what point is my titration finished? When I notice the first change or as soon as adding more EDTA doesnt change the color?


texts: Is temperature just the phenomenon of particles colliding against an object?

texts: This is just something that I thought up while doing busy work at my job. Is the sensation of heat simply coming from particles colliding with your, say, hand? Are they transferring energy more to objects because they have higher velocities, and thus heat can hurt? (Sorry, this isn't a more cohesive question...).


texts: Determining geometry of coordination compund without experimental data

texts:
How can I determine if a coordination compound has a tetrahedral or square planar geometry without any experimental data (such as magnetic spin) by just looking at its formula?

For example, what is the geometry of the following complexes:

$\ce{[CoCl4]^2-}$
$\ce{[Ni(CN)4]^2-}$
$\ce{[CuCl4]^2-}$

Do they have a Jahn-Teller distortion?


texts:
The question is to find the product in the following reaction-

In the answer given, they have replaced Cl with I and inverted the configuration at that carbon(Finkelstein reaction).
But $\text{I}^-$ being a good base, wouldn't it first take away O's acidic H and then $\text{O}^-$ will show Neighboring Group Participation attacking the carbon with chlorine and finally resulting in retention of configuration?


texts: Calculations of concentrations in two different equilibria

texts:
I'm a high school student, and I'm learning about acid dissociation equilibrium.
I wanted to make the idea of Le Chatelier's principle rigorous in math, so I decided to take to it with some calculus. It was all fine with just the acid equilibrium:
$$\begin{align} K_a = \frac{\ce{[H3O+][A-]}}{\ce{[HA]}} \end{align}$$
My thought process was to call $\ce{[H3O+]}$ $c_1$, to call $\ce{[A-]}$ $c_2$, and to let $c_1$ increase by some small $dc$. By Le Chatelier's principle the backwards reaction will be favoured, and both $c_1$ and $c_2$ will change by some other $dc_2$. In this light, the total change in $c_1$ would be $dc_1 = dc + dc_2$.
Plugging into the equation for $K_a$, noting that $K_a$ is constant throughout the changes in each concentration, and observing that $\ce{[HA]} = c_0 - c_2$ (where $c_0$ is the concentration of $\ce{HA}$ before any dissociation), you can get an expression for the change in $c_2$ in terms of the initial change in $\ce{[H3O+]}$, namely:
$$\begin{align} dc_2 = -\frac{c_2 ^2}{c_0 K_a + c_2 ^2}dc \end{align}$$
This can be used to find the final change in $c_1$:
$$\begin{align} dc_1 = -\frac{c_0K_a}{c_0 K_a + c_2 ^2}dc \end{align}$$
This is (pretty much) a system of differential equations. Now I'm not that experienced with systems of differential equations, but I knew enough to solve this particular system.
However, I then tried the same thing with the ionic product also taken into account:
$$\begin{align} K_w = \ce{[H3O+][OH-]}. \end{align}$$
Call $\ce{[OH-]}$ $c_3$, and change it by $dc$. Long story short, this makes $c_2$ change by some $dc_2$, $c_3$ change by some $dc_3 = dc + dc_3'$ (where $dc_3'$ is the amount the concentration changes strictly after $dc$ has been added) and it makes $c_1$ change by some $dc_1 = dc_2 + dc_3'$. Plugging all of this into the two equilibrium expressions as before gets a system of three differential equations:
\begin{align} \frac{dc_1}{dc} &= -\frac{ac_1/c_2^2}{(c_1+c_3)(1+a/c_2^2)-c_3}; \\
\frac{dc_2}{dc} &= \frac{c_1}{(c_1+c_3)(1+a/c_2^2)-c_3}; \\
\frac{dc_3}{dc} &= \frac{ac_3/c_2^2}{(c_1+c_3)(1+a/c_2^2)-c_3},
\end{align}
where $a = c_0K_a.$
Problem is, this system of differential equations looks... ahem viciously unsolvable. So much so that I doubt that the process I took to get to it was right. So is the way I'm doing this correctly, or is there a more efficient and less calculus-y route? Also, what is this field of study even called? I couldn't find any resources on these types of calculations, which is why I'm on here.


texts: What happens if you mix two insoluble liquids but with the same density?

texts: Would it make two separate phases? or would it make something like and emulsion?


texts:
Back in April, there was an article in new scientist discussing the work of Lee Cronin, who postulated that molecules of a certain complexity must be biological.

  Cronin has developed a way to measure the complexity of a molecule by
  counting the number of unique steps – adding chemical side groups or
  ring structures, for example – needed for its formation, without
  double-counting repeated steps. To draw an analogy, his metric would
  score the words “bana” and “banana” as equally complex, since once you
  can make one “na” it is trivial to add a second one.

  Any structure requiring more than about 15 steps is so complex it must
  be biological in origin, he said this week at the Astrobiology Science
  Conference in Mesa, Arizona.

Does anyone know how to use Cronin's method to measure complexity?


texts: Is reduction potential and stability related?

texts:
Suppose the half reactions:

$$\begin{split}\ce{Na^+    +  e^-   &->  Na} ~~~~~~~~~~~~&\text{ $E^o = -2.71$}\\
\ce{Cu^{2+} + 2 e^-  &->  Cu} &\text{ $E^o = +0.34$}\end{split}$$

Can I say that $\ce{Na+}$ is more stable than $\ce{Na}$, so $\ce{Na+}$ has negative potential to reduce? If so then can I also say that $\ce{Cu^2+}$ is less stable than $\ce{Cu}$ so $\ce{Cu^2+}$ has a positive potential to reduce?


texts: Why elements with high atomic mass (like tungsten) are used in the production of X-rays, in the Cathode-Ray Tube?

texts:
I was studying about the production of X-rays, and was struck at how elements having high atomic mass (like tungsten) are used for the production of high energy X-rays. I am wondering why low atomic mass elements are not used for the production of high energy X-rays.

I have read that "tungsten has the highest melting point of any metal, and because over 99 percent of the energy put into the X-ray tube to produce the beam is turned into heat energy, the ability to dissapate the heat without loosing structural integrity is critical".


texts: To predict if a substance is deliquescent

texts:
FeCl3,FeSO4 and CuSO4 all are deliquescent solids.

  Is there any way to predict this without knowing this fact?
  I am looking for a way to predict if a substance is deliquescent for my upcoming exams.


texts: Why is an alkyne more acidic than an alkene? Or, why is acetylene more acidic than ethylene?

texts:
pKa acetylene ~ 25

pKA ethylene ~ 44

I'm not looking for the "because alkyenes are sp hybridized and more s character means their electrons are held tighter" answer because I'm not the biggest fan of hybrid atomic orbital theory.

Is there an alternative answer that looks at this question from a Molecular Orbital (MO) Theory perspective instead? Or maybe a different conceptual analysis as to why the electron pair is more stable on the alkyene carbon than an alkene carbon? Does magnetism (from the ring of charge in the triple bond) somehow have an effect?

Or is it really as simple as the fact that the because the pi electrons are higher energy and farther away from the nucleus, the remaining electrons participating in sigma bonding must counteract the strong Coulombic pull from the carbon nucleus by moving closer to it?


texts: What is the hybridisation of hydrogen in methane?

texts: I am trying to understand hybridisation. In methane carbon has $\mathrm{sp^3}$ hybridisation, but what is the hybridisation of hydrogen? Is it $\mathrm{sp^3}$? If yes then why?


texts: Isn't the dual behaviour of subatomic particles contradictory?

texts: I recently came across Molecular Orbital Theory. In this, if two electrons are bonding, their waves merge and they form a proper bond. But this is directly opposite to the particle theory, according to which they should repel each other as they have like charges.


texts:
I'm trying to figure out what my optimal current density would be in respect to the limiting current density.

How do you calculate concentration polarization and limiting current density in an electrolytic cell. There are two copper electrodes and a $2\:\mathrm{M}$ copper nitrate solution. The average current density was $0.375\:\mathrm{A\:cm^{-2}}$.

I know the Tafel expression ($\eta a=a+b \log i$) can calculate the voltage drop but can I find the limiting current density just like that in the image?


texts: The type of H-NMR spectra observed for S=PF2H and other inorganic molecules similar to this

texts: I was hoping to learn more about the types of splitting observed in inorganic molecules such as S=PF2H. I am familiar with the typical splitting patterns associated with the study of organic molecules studied by C and H NMR. We know that H and F have a spin of 1/2, in reading about the effects of fluorine in on H NMR, it appears that fluorine relaxes in a similar way to protons when pulsed by a radio frequency. Since the two nuclei have the same spin but are different types of nuclei altogether and impact each other according to the Nuclear Overhauser Effect, what kind of signals would be given by an H NMR for the molecule? Would we see signals corresponding to fluorine given that it has the same spin as the proton?


texts: Can I engrave borosilicate glassware without compromising its structural integrity?

texts: Can I use a pen engraver (the kind that's like a tattoo gun with a diamond tip) to engrave my initials on labware without compromising it? I am in a lab space with a shared acid wash, and my glassware keeps getting boosted. I'm worried about e.g. heating a beaker and having it shatter because of the propagation of microfractures potentially caused by the engraver.


texts: Is an ionic bond more like a covalent bond or an intermolecular force?

texts:
I have asked a question loosely asking this, where I confused terms and did not specify what I wanted to know here, so I formed a new question.

What are the differences and similarities between ionic bonds and covalent bonds and ionic bonds and dipole-dipole interactions?

It seems to be that an ionic bond is nothing but a stronger dipole-dipole interaction. The only difference is where the electrons are.

For example, let's take a sodium cation and chloride anion bond. The sodium had its electron taken away from it. It is now positive. Chloride had an electron added to it and it's feeling negative. Now the two will attract because of these charges.

Now let's take two water molecules. The hydrogen of one will be positive because it is less electronegative and thus the electron density will be greater around the oxygen, which is more electronegative, making it negative. Now the hydrogen of one and the oxygen of another will attract due to the charges.

It seems like the only difference is that if you split the sodium chloride and the water's hydrogens and oxygen, the sodium and chloride will still have a charge, but the hydrogens and oxygen will not.

By textbook, a dipole-dipole interaction is an intermolecular force while a covalent bond, as well as an ionic bond, is a chemical bond. It seems to me that, yes, the forming of ions is a chemical reaction, but the ionic bond is an intermolecular force.


texts:
This question was inspired from the following questioN:

I thought the answer would be either A (maybe accounting for larger sizes?) or B (Bent's rule) but apparently the answer is D. Can someone explain why this is so?

This question is #54 on the 2010 USNCO Part 1


texts: What is the chemical test for identification of benzophenone?

texts:
How to identify that a unknown compound is benzophenone?

My working:-

First I added 2,4- DNP(2,4-Dinitrophenyl hydrazine) to the compound. Yellow-orange crystals were formed which indicated presence of carbonyl group. Then, I added Tollen's reagent to the compound. It did not gave silver mirror which means aldehyde group is absent. So, it must be a ketone. So, I added m-Dinitrobenzene to the compound. It did not gave violet colour. Alternatively, I added Sodium nitroprusside to the compound. It did not gave a red color. Both the test is for confirmation of ketone compound.

I asked my teacher what is the unknown compound. He said that it is benzophenone. Also, in the practical book where all the chemical test were mentioned, it was mentioned  as a side-note that benzophenone does not give the above mentioned test. So, what is the chemical test for identification of benzophenone?


texts:
I've been using SLES to break surface tension in some water solutions. However after a year or so it seems like the ability to break surface tension seems to wear off in the solutions. So my question is if this is supposed to happen? Does Sodium Lauryl Ether Sulphate lose its ability to break surface tension over time?

The SLES im using has also begun to smell bad from the tank, which made me curious about it wearing off or getting too old.


texts: Seeing Copper has an exceptional electron filling in its valence shell(4s1 3d10), the way I see it is that on +1, a d10 configuration should be more stable and hence easier to attain than a d9 which would come on +2. Or is there some reorganisation of electrons? Either way, please help explain. Thank you.


texts:
The isotope of hydrogen, tritium, is indeed radioactive resulting in $\ce{^3He}$ through beta decay.

But what of the radioactively 'stable' isotope deuterium?

Are all deuterium atoms destined to be deuterium for eternity or is there any process other than radioactive decay that could lead to transition such as say $\ce{^1H}$?


texts: what the solution of this problem, negative absorbance values in UV-vis spectrum

texts:
In my project, I take the UV-visible spectrum of reaction between pyridinium chlorochromate and N-acetylcysteine. In some wavelengths, the absorbance value is negative for example it is (-0.006, -0.002, -0.003){negative but very small}.

Also when I take the spectrum of pyridinium chlorochromate alone, there are absorbance values in negative {negative but very small}.

The blank is NaClO4 solution.

what are the reasons for these negative values? And can I negligible these values?

Thank you...


texts: Have I identified the IUPAC name of this ketone correctly?

texts:
$\ce{(CH3)2-CH-CO-CH2-CH2-OH}$

The IUPAC name I came up with was 1-hydroxy-4-methyl-3-pentanone because:

Ketone has higher priority over alcohol
The lowest locant set is achieved by numbering the C bonded to -OH group as 1.

But the answer given states it is 4-methyl-3-oxo-1-pentanol which violates the first rule mentioned above.

Please clarify the discrepancy between my reasoning and the textbook answer.


texts: Corrosive/ Acid cabinet gets wet from time to time

texts:
I have a metallic acid cabinet in a chemistry-based lab which I use store hydrochloric acid, sulfuric acid and ammonia. I also store nitric acid together inside but they are physically separated from the rest by an additional PP plastic case inserted into the acid cabinet.

The issue is that from time to time, I realized that the doors and secondary trays in my acid cabinet will get wet, especially the area near the sulfuric acid, and white powdery crystals sometimes form on the walls of my HCl bottles. I have ensured that I tightly sealed each of the bottles. Can anyone help me out? Is this dangerous? I'm trying to seek a solution before anything serious that might happen.

Also I have a few bottles of unopened, still sealed sulfuric acid which have turned black but the acid is still clear and usable when poured out, is it still alright to use for experiments? Will the results be affected?


texts: What is the appropriate sizing for fiberglass compatible with polyamide?

texts:
I am looking for a chemical coating for glass A fibers, compatible with polyamide. The fibers are uncoated, 100-filament strands of 22-micrometer "A" glass fibers.

We are producing fiberglass in our lab, and we want to size (coat) them with something which can keep the strands together and at the same time enables the fibers to bond with polyamide. We can use materials like PVA to keep the strands together, but then the fibers do not bond with the polyamide (mixing with polyamide happens after we produce the strands and chop them, with 4mm in length).

I am a beginner in composite world so I would appreciate if you can give me details on how and where to buy such chemical, or how to synthesis it myself if possible?


texts:
Which carbocation, formed due to ionisation of the C-Cl bond will be more stable between 2-chloro-2-methylpropane or chloromethyl benzene and why?

At first I thought it should be the  2-chloro-2-methylpropane because from what I know methyl groupss are electron donating groups and benzene rings are almost always electron withdrawing groups, thus the methyl groups will help stabilize the carbocation more. But apparently it is the carbocation of the chloromethyl benzene that'll be more stable and I really can't understand why that is?
I've searched a couple of other sites and gone through my book as well but it doesn't quite explain this.

I tried to upload the images but it would just not let me, so I'll try my best to explain them here.
On the  2-chloro-2-methylpropane the carbocation I'm referring to is the one forming on the central carbon atom and on the chloromethyl benzene its the one on the carbon atom of the methyl group. Hope that makes it clear; both are formed due to losing ionisation of the $\ce{C-Cl}$ bond.


texts:
What are the general ways to treat an accident involving highly concentrated or similarly dangerous acids?

I have a lab instructor who recently debated with our group about treating an acid spill on the skin. According to him, one should immediately rinse off the acid with running water for about 15-20 minutes. He says that one should never apply bases to the site because an Acid-Base is highly exothermic and would only increase the damage.

However, I clearly remember learning once that one should apply baking soda (sodium bicarbonate) to a bee sting or ant bite in order to neutralize the acid and relieve the burning.
I also know that the dilution of an acid in water is done by adding the acid slowly to the water containing vessel because of the heat released in the process. And especially when preparing a dilute solution of sulfuric acid, one wears safety goggles and gently stirs the solution to prevent splashing.

So which is it? And does it depend on the severity of the burn or type acid?


texts:
A frst order reflection from (111) plane is observed for LiX with 2theta =24.6 degree (X-ray of wavelength 1.54 angstrom). Assuming LiX to be a cubic crystal system, calculate the length of the side of the unit cell in angstrom.
This is a question of JAM 2014, here, the length is considered as a=2a for ionic system in a solution provided by Arihant's book. Why is it so? Is it correct?


texts:
I am trying to make sure I have an accurate understanding of the effect of reciprocal lattice points on diffracting planes and the direction of the lattice point vector.
Is the following statement accurate or have gone wrong somewhere?
Each reciprocal lattice point represents a set of diffracting planes and the direction of the lattice point vector d*hkl is perpendicular to the crystal plan hkl


texts: How many moles NH4Cl must be added to NH3 to create buffer with pH=9?

texts:
How many moles of $\ce{NH4Cl}$ must be added to $\pu{2.0 L}$ of $\pu{0.10 M}$ $\ce{NH3}$ to form a buffer with $\mathrm{pH}=9$? Assume the addition does not change the volume of the solution significantly.

The solution given is as follows:

The equilibrium between $\ce{NH3}$ and $\ce{NH4+}$ is given by-
$$\ce{NH3 + H2O <=> NH4+ + OH-}$$
We know the $K_\mathrm{b}$ value and $\ce{[OH-]}$ from the $\mathrm{pH}$ and $\ce{[NH3]}$ is given, thus we can solve for $\ce{[NH4+]}$. The solution given says that the final answer is given by this concentration multiplied by the total volume $\pu{2 L}$.

I don't follow the logic in the solution. The $\ce{[NH4+]}$ we found was the total concentration of $\ce{NH4+}$ in the solution after adding the salt. But before adding $\ce{NH4Cl}$, there was already some $\ce{NH4+}$ in the solution (we don't know how much).
Thus to find the number of moles $\ce{NH4Cl}$ we need to add, shouldn't we subtract the number of moles $\ce{NH4+}$ already in the solution from the answer we got in the textbook solution?


texts: Reaction between Sodium Thiosulfate and Iron Chloride

texts:
I'm doing a paper on catalytic effectiveness in this reaction, and am trying to identify how the catalysts are speeding up the reaction. Based on what I can find,
$\ce{Fe}$ starts as $\ce{Fe^3+}$, and it will react to form a transitional violet compound, which I think is $\ce{Fe2(S2O3)2}$. This will then break down into $\ce{Fe^2+}$.

I am using various catalysts including iron sulphate, cobalt chloride, etc. However, as far as I can tell, the catalysts are not speeding up the first step ($\ce{Fe^3+}$ to violet compound), but the second (violet compound breaking down to $\ce{Fe^2+}$ and other ions). The catalysts I've used have varying levels of effectiveness. The main 3 factors that would change how catalysts could affect this, as far as I can tell, are electron transfer,complex shape, and ligands. I don't think they are acting to transfer electrons here, and I think all the catalysts would have the same complex shape (octahedral). Therefore, I want to know how the ligands formed from each catalyst (causing it to go from linear monodendate violet compound to octahedral ions) would affect this differently. The catalysts I'm using are copper sulphate, iron sulphate, cobalt chloride, and nickel sulphate. I can't find much information about what is happening in this reaction. If anyone knows what ligands are formed, and how the shape/electrons/ligands of the catalysts are affecting this reaction speed, I would really appreciate it.


texts: Difference between subshell and sub-subshell?

texts: I consider the s p d f orbitals as a subshell, but I have heard about the term sub-subshell. what is the difference between these two?


texts: Why polyethylene (PE), wool (polyamide) and cotton (cellulose) burnt with different smells, while they just product CO2 (and N2)?

texts:
Both PE and cotton produce CO2, but they distinctly have different smells while being burnt (Burning PE has smell of candle wax, while burning cotton’s smell is like burning leaves). Wool produces CO2 and N2 which is odorless, but yet has smell of hair burnt.
  Moreover, they also differ in burning process (PE and wool burns slowly, while cotton burns rapidly). So why there are such differences when their products are similar?


texts: Is water "hardness" dependent more on calcium or magnesium?

texts: If one sample of water has a certain concentration (g/L) of calcium ions, and another sample as that same concentration of magnesium ions, will one solution have a greater "hardness than the other"? In other words, does one ion have more influence over water hardness than the other?


texts: I am trying to find the current transferred to the anode and cathode of a Lithium Ion Battery at different voltages. I know the temperature (approximately) of the battery, the battery's starting voltage, the voltage at 30sec intervals of a constant power discharge (from which current can be deduced), the dimensions of the battery and the initial amount of charge in the battery. What could I do to find this current transfer?


texts: What kind of chemicals would exist at the heat death of the universe?

texts:
As the universe reaches the maximum entropy, presumably only the most stable chemicals would exist.

Assume that all the elements haven't turn into iron yet, what kind of chemicals would dominate at that point?


texts: Under what conditions does MnO2 acts as an oxidizing agent?

texts:
It's very strong in acidic medium. Does it have low or nil oxidizing ability in neutral and basic media?

Does heating solid $\ce{MnO2}$ give it better oxidizing properties?


texts: Which reactions occur during the oxidation and dissolution of bromide/bromine?

texts:
I'm trying to understand the fate of bromide anions during and after they undergo anodic oxidation. I have a solution of 94% DMF/6% water (by volume) with 0.1 M tetrabutylammonium  bromide (TBAB) as the supporting electrolyte. I've used this electrolyte to reduce a cathode at -2.5 V or less v. the Ag/AgCl reference electrode. During the reaction, the solution near the platinum counter electrode (the anode) turned yellow. I would assume this is due to the reaction:
$$\ce{2Br–(aq)-> Br2(l) + 2e– }$$

The next day, I noticed that the yellow liquid in the solution had completely disappeared. I'm assuming that the bromine had dissolved into the solution into $\ce{Br-}$ ions again. However, I'm not 100% sure of the chemical reaction associated with this. Also, would there be any side products associated with the dissolution? Or, do we end up with the species we initially started with in terms of bromine?

I ask because I would like to be able to reuse the electrolyte multiple times and so want to figure out exactly how the electrolyte changes after the reaction. At the cathode, there will be reactions such as the hydrogen evolution reaction which will make the solution more basic. However, I'm not sure what happens with the bromine.


texts: Do "weak-field" and "high spin" complexes refer to the same thing?

texts:
I will keep it brief; I know that there are weak field, "moderate" field, and strong field ligands and that these might contribute to a complex being high or low spin overall. My question is, does a complex having high spin indicate a weak field complex, regardless of ligand "strength" (or vice versa)?
For example, $\ce{[Fe(H2O)6]^3+}$ has a moderate strength ligand ($\ce{H2O}$) but is overall a high spin complex, so would $\ce{[Fe(H2O)6]^3+}$ be considered a weak field complex, despite the ligand strength not being weak? If not, is it only appropriate to call it a high spin complex? Thank you.


texts: How good is aromaticity at stabilization?

texts:
I've been taught that aromaticity is often a very good stabilization factor. Then I came across this question in which another compound was said to have more stability.

Upon deprotonation arrange in the order of stability.

Why is S more stable than P?
(the answer given is (a); from Himanshu Pandey Organic Chemistry chapter General Organic Chemistry)


texts: What is number of 1H NMR signals for toluene?

texts: I am searching the web for the number of 1H NMR signals of toluene and I find two different results. Some say there are two signals while others say there are four (According to me, it should be 4). For the two signals, it suggests that all five aromatic hydrogens are taken as equivalent. A similar problem arises for compounds like ethylbenzene, benzyl alcohol, and anisole. How can I reconcile these different results?


texts: How do sulphate esters compare to phosphate esters?

texts: In particular, the energy released from hydrolysis of the -S-O-S- bonds and how stable are they in aqueous solution compared to phosphate esters?


texts:
The following passage has been extracted from the book "Organic Chemistry-10th edition by Solomon and Frhyle":

  "The growth of living things from microbes to elephants rests on organic reactions, and organic reactions provide the energy that drives our muscles and our thought processes"

Is the above statement true that, organic reactions provide energy that drives our thought processes? Is there any other process by which we are given energy to drive our thought processes?

If you all agree with the statement, then when a person is called "dead" (or after a while being called dead), I hope the reactions will cease (because he can't perform "thought processes"), isn't it?

If these all points are agreed, is their a possibility of repairing a dead body by restarting the reactions immediately?

I agree that, it is not as easy as I said, there is a complexity, but I believe we all can do some research "together" and try to do a "little" contribution to save ourselves.

So, can we repair a dead body?


texts: Generally available fluid with good heat transport properties

texts:
I have designed a container which is heated up and has to heat up some tube-coils of water inside of it. This container is filled with a fluid that can help store and transfer the heat received from the container to the tube-coils.

My plan was to find some material that I can easily buy and which is not very expensive to fill the $636cm^3$ container.

It has to have a high coefficient of heat transfer, high heat capacity and an operating temperature of at least the range of 10-400 degrees Celsius. I will also need to calculate how much the volume changes when it goes from around -35 to 500 degrees Celsius.

I also think a high density and if the material is non-toxic might be a plus.

Does anybody know any fluid that could be used for this or somewhere where I could find such information?


texts: how to obtain potential curves from database?

texts:
I'm sorry if this is a really super basic question. I am looking at the potential curves of a diatomic molecule in a book , and to plot them. I google the molecule and got to the NIST website, there I get diatomic mass and constants for each state,  such as:

Te -     minimum electronic energy (cm-1)
ωe  - vibrational constant – first term (cm-1)
ωexe -     vibrational constant – second term (cm-1)
ωeye - vibrational constant – third term (cm-1)
Be -   rotational constant in equilibrium position (cm-1)
αe -   rotational constant – first term (cm-1)
γe -   rotation-vibration interaction constant (cm-1)
De -   centrifugal distortion constant (cm-1)
βe -   rotational constant – first term, centrifugal force (cm-1)
re -   internuclear distance (Å)
Trans. -   observed transition(s) corresponding to electronic state

Great, I should be able to use these to plot the potential energy curves for each electronic state somehow right? there is no formula i can see that here, is it just morse potential? what happens if the state is unbound?
Please help me understand how to plot the potential curves. Thanks!


texts: Why is pyridine used when making tosyl esters from alcohols?

texts: Tosyl chloride is used to make a hydroxyl group into a better leaving group. However, when the reaction of tosyl chloride and an alcohol occurs, a weak base such as pyridine should be used. Why?


texts: Looking for information about possible ingredients of a fertilizer

texts: I have found it in a local store, "20.20.0 - Kompoze" is written on the pack. In the pack, there are yellowish greenish irregular formed little balls. What is this, do you know ? Please help and excuse my poor english.


texts:
I came across this reading a journal article. Here I have the context:

  Here we report for the first time the synthesis of $\ce{TiO2}$ NPs
  on a layered $\ce{MoS2}$/graphene (MG) hybrid for use in
  photocatalytic H2 production. It is shown that the activity of
  the $\ce{TiO2}$ NPs is significantly enhanced by the presence of this
  layered MG cocatalyst. In this case, ethanol was used as a
  sacrificial agent, as it is a sustainable and renewable source and
  showed very good performance with this photocatalyst;
  however, other sacrificial agents (e.g., glycerol) can be used
  to make this strategy feasible.

Google results came up with similar instances.

My guess is that it would be a chemical consumed in a reaction, but one that doesn't contribute to the structure of the product. Thoughts?


texts: How do I build a thermochromic thermometer?

texts:
My Chem 152 lab is requiring us to build a thermochromic thermometer utilizing methods from previous labs such as absorbance spec and temp.

We've been taught how to calculate Kc values successfully as well as delta H and delta S from these methods, but I'm unsure of how to combine everything into creating a thermochromic thermometer.

We're given $\ce{CoCl2(EtOH)2}$ and $\ce{CoCl2(iPrOH)2}$ to react with $\ce{MeOH}$. We had to complete a pre-lab assignment by calculating $K_c$ values at $275\ \mathrm{K}$ using $\Delta H$ and $\Delta S$ values from a reaction of $\ce{CoCl2(EtOH)2/MeOH}$ and a reaction of $\ce{CoCl2(iPrOH)2/MeOH}$. I was able to determine whether each reaction was reactant or product favored based on their $K_c$ values, but I'm completely stumped on how to use all of this information in creating a thermochromic thermometer.


texts: Fast way to isolate 4-nitrophenol from 4-aminophenol

texts: I'm working in the lab with a very old (like 30 years old) sample of 4-nitrophenol, wich of course has been reduced with the time to 4-aminophenol. I need to isolate both reagents and work only with the nitrophenol, is there any quick way to do that?


texts: Is there any possibility of tautomerisation to en-ol form?

texts:
In the picture, you can see the bridge whose end points are in para relation (for making the image clear).

Now, what my friend said is that there is no possibility of tautomerisation as there is no H to the right of =O and to the left of =O, on removing H, the bridge will be loaded(?!?).

But according to me, positive charge on the bridge end-points may be unstable as the bridge is out of the plane of the planar molecule and making it sp2 hybridized isn't a kind thing to do. But on removing H from the bridge end point (for tautomerisation), there will be negative charge on the bridge end point, which is perfectly normal.

So will it tautomerise or not?


texts: Reversible & irreversible adiabatic processes

texts:
Work done in reversible is more than that of irreversible

Suppose we are going from state $(P_1, V_1, T_1)$ to some other state say $(P_2, V_2, T_2)$ for reversible and $(P_2, V_2, T_2')$ for irreversible. Which should be greater, $T_2$ or $T_2'$?

My attempt

Let us say heat supplied is same i.e q for both reversible and irreversible. We already know that $U = q - W$

Reversible as work done is more so $U$ becomes less and in irreversible $W$ is less so $U'$ is more than $U$ i.e $U' > U$

As $U'$ is greater $T_2'$ should be greater. Is this correct explanation?


texts:
Which of the following pairs show common ion effect?

$\ce{BaCl2}$,$\ce{Ba(NO3)2}$
$\ce{NaCl}$, $\ce{HCl}$
$\ce{NH4OH}$,$\ce{NH4Cl}$
$\ce{NaOH}$, $\ce{NaCl}$

Its not (1) because they are both solids.
The remaining are solute solvent pairs. So all the other pairs will show common ion effect if the solute is soluble to some extent and exists in an equilibrium with the solvent. The answer given is (3). But why cant (2) and (4) show common ion effect?


texts: Why does salt dissolved in water taste like salt? If it's just Na+ and Cl- ions

texts: When $\ce{NaCl}$ is dissolved into water it breaks down into $\ce{Na+}$ and $\ce{Cl-}$. It stays in this form until the water evaporates and then the ions go back to normal $\ce{NaCl}$. So why does water with salt in it still taste like salt? I am asking because if the molecule $\ce{NaCl}$ is broken down into $\ce{Na+}$ and $\ce{Cl-}$ then how does it have the characteristics of $\ce{NaCl}$?


texts:
I have come across this Quora Answer where it was written that cold water is heavier than hot water.

Are there any proofs which support it?


texts: Is there a term that denotes 'molecules and molecular constituents'?

texts:
In my notes, I've used phrases such as 'atom, particle, or molecule' more often than I'd like. For example, Wikipedia defines atomic mass as

  the mass of an atomic particle, sub-atomic particle, or molecule.

I remember concise definitions more easily, so a single word for 'molecules and molecular constituents' would be useful.

Is there such a term?


texts: I've been trying to create 3D structures of unionized tyrosine (and other amino acids, it's just tyrosine is the one I'm up to atm) using the structure of Zwitterions found within PDB files and to do this I need to know what C-OXT (which is found within the carboxylate functional groups) stands for in PDB files as this will help me to decide which oxygen in the carboxylate groups should be represented with the double bond from the associated carbon and which should have the single bond. The other oxygen in the carboxylate group is just called C-O in the PDB file.


texts:
Why transition metal chloride complex have lower reduction potential than metal aqua ions? For example:
$$
\begin{align}
\ce{Au^3+(aq) + 3 e- &-> Au(s)} &\quad E^\circ &= \pu{+1.52 V}\tag{1}\\
\ce{[AuCl4]-(aq) + 3 e- &-> Au(s) + 4 Cl-} &\quad E^\circ &= \pu{+0.93 V}\tag{2}
\end{align}
$$
Is it because the chloride complex formation constant is very high (higher than aqua ions) so the reduction of $\ce{Au^3+}$ is less favored?


texts: Why gas solubility decreases with temperature?

texts:
I found this quote on a Chemistry LibreTexts website:

  If the heat given off in the dissolving process is greater than the heat required to break apart the solid, the net dissolving reaction is exothermic (energy given off). The addition of more heat (increases temperature) inhibits the dissolving reaction since excess heat is already being produced by the reaction. This situation is not very common where an increase in temperature produces a decrease in solubility.

I understand that when dissolving releases more energy than is being used in the dissolution, the net reaction is exothermic. Why exactly does the excess heat inhibit the dissolution? I cannot see the reason why. Could somebody explain this in more detail?


texts:
I have read that objects gain electrons to become negatively charged and also that they lose electrons to become positively charged. I have also read that same charges repel each other and non-same charges attract each other. My question is how can objects gain electrons when the electrons should repel each  other.

For example: an element has 17 electrons, so its electronic configuration will be:

K L M
2 8 7

So, it will gain 1 electron. But how can this happen? I mean, shouldn't the electrons repel each other? Moreover, if it gains an electron how will it become stable? I mean I agree that there will be 18 electrons but to become stable shouldn't there be 18 protons? So from where will the extra proton come from?


texts: Does CHT=CHT have a geometric isomerism because of tritium atoms?

texts: Is the radioisotope of hydrogen considered as a new atom? Can you detect it with an H NMR?


texts: I want to decrease the boiling point of a compound. So I need to create an azeotrope mixture from two or three compounds. Where can I find out how make it?


texts: Which out of the two has greater bond angle? Water or diethylether.Why?

texts:
My theory:

The ethyl groups in diethylether being larger in size when compared to hydrogens in water, should be repelled more by the lone pairs on the central atom oxygen. Hence, the ethyl groups should come closer, thereby decreasing the bond angle.

Moreover, the electronegativity difference between the central atom and the peripheral atoms is more in case of water i.e., $\ce{O-H}$ electronegativity difference is more than that in $\ce{C-O}$ as per Pauling’s scale. Hence, the oxygen atom should pull the bond pair closer, thereby allowing to open up the $\ce{H-O-H}$ bond increasing the bond angle.

Hence bond angle of water should be greater than that of diethylether. Am I right?

PS: I know that in reality dimethylether has greater bond angle than water.


texts: Why is ruthenium dioxide a conductor while titanium dioxide is an insulator?

texts:
Ruthenium dioxide has the same crystal structure as rutile (titanium dioxide), and the metal atoms are in the same oxidation state.  Yet ruthenium dioxide is a metal-like conductor (its resistivity is given by Miao et al. [1] as $\pu{40 \mu\Omega{} cm}$ for thin films), while titanium dioxide is an insulator with a resistivity of at least $\pu{E13 \Omega{} cm}$ and a band gap of over $\pu{3 eV}.$
Why are the electrical properties of these two ceramics so different?
Reference

Miao, G. X.; Gupta, A.; Xiao, G.; Anguelouch, A. Epitaxial Growth of Ruthenium Dioxide Films by Chemical Vapor Deposition and Its Comparison with Similarly Grown Chromium Dioxide Films. Thin Solid Films 2005, 478 (1), 159–163. DOI: 10.1016/j.tsf.2004.10.032.


texts: Does this 'Belousov-Zhabotinsky Reaction' kit contain the correct reagents?

texts:
I want to run the Belousov–Zhabotinsky reaction as a demonstration. As far as I'm aware, you need sodium bromate, sodium bromide, water to $\pu{100 ml}$, malonic acid, phenanthroline and ferrous complex.  This is the recipe that I know, but I can't get hold of the right ingredients.

I found this kit entitled 'Belousov-Zhabotinsky Reaction' for £15.00. I am not sure it has the right ingredients:

  Kit contents: Iodine sodium, malonic acid, Sulfamic Acid, sodium thiosulfate
  Manganese sulfate, starch solution, cups 5 pieces, chemicals, racks etc.

Does this kit have the right ingredients for the Belousov–Zhabotinsky reaction?


texts: Understanding how mass spectroscopy works

texts:
I’m trying to get a deeper understanding of how mass spectroscopy works. Most tutorials and textbooks I’ve encountered omit certain details about the process and I’m hoping someone out there who understands the process can fill in the gaps. I’ll start by explaining the way I currently understand the process and then list where I start to get confused.

1 First a particular molecule is bombarded with a beam of electrons (ionization step). This step works to free an electron from the molecule under analysis which generates a cation.

Note: It’s important to remember that the only reason why this molecule was ionized is to make use of a magnetic field to bend its direction. Only ions will be affected by this magnetic field which allows us to pinpoint the molecule in question.

2 Next, these ions are accelerated by an electric field toward a magnetic field that bends the moving ions by a certain amount.

  Question 1: What’s the difference between an electric field and a magnetic field? And why does the magnetic field bend the ions while the electron field does not. Is this just a consequence of the shape of the apparatus? Could you use a magnetic field to accelerate a particle and a electric field to do the bending? I’m just really confused as to the difference between electric fields and magnetic fields.

3 The ions that bend will travel around a tube by a certain degree and hit a detector. The amount of bending will tell us about the mass of a particular molecule. Heavier molecules will bend less and lighter molecules will bend more.

  Question 2: I’ve come across a tutorial that said that what this detector is actually measuring is the mass to charge ratio. How is this calibrated and how does this step allow us to measure the mass of a single molecule. Won’t there be multiple particles hitting the detector at the same time, will this not affect the mass reading of a particular molecule? I'm just confused about this final step and how we can get an accurate mass reading for a particular molecule.

Any help understanding this concept would be appreciated.


texts: What is the use of both mol and mass representing the same thing i.e. amount of something?

texts: A mol is a unit but also has a magnitude. How can a unit have a magnitude? And if mole is used to measure an amount of substance than what does mass measure?


texts:
I want to make resin jewelry, but I'm having problems!

I want to create that effect, but I do not know what materials to use

The result is a mix of resin and other such things


texts: Relationship between the 2nd theorem of Hohenberg and Kohn and the Variational Principle

texts:
In Density Functional Theory, the 2nd theorem of Hohenberg and Kohn states:

  The electron density of the system that minimises the ground-state energy is the exact electron density of the system.

Similarly, there is also the widely-known Variational Principle in quantum chemistry which states:

  The wavefunction that minimises the ground-state energy of the system is the exact ground-state wavefunction.

They seem very similar to me and I would just like to ask if there are any similarities between the two, perhaps in terms of the proofs of these two fundamental theorems.


texts: Tables/database/literature of specific or optical rotation

texts:
I'm looking for a comprehensive reference of experimental specific rotation or optical rotation data. It can be a published literature review, a free web database with API access or one that permits scraping, or even a table on a web page with references.

ChemSpider pages link to outside sources (I think only chemical suppliers) for optical rotation, but this is problematic:

it's unclear what molecules contain this information (not all stereoisomers do),
not all the product specification pages on the suppliers' websites actually contain the data,
the values aren't available through the ChemSpider API, and
it's forbidden to screen scrape ChemSpider pages.

The story seems to be similar for PubChem, though they allow scraping within reason.

For example, here is a review collecting experimental electron affinities for a large number of small molecules and elemental clusters. It's fine that this isn't web-based, because all the values are together and in bulk; writing a PDF scraper is worthwhile because there are so many entries.

Also acceptable would be a book, such as the comprehensive reference from Huber and Herzberg that contains rotational constants, bond lengths, and other constants for diatomic molecules.


texts: Why do sealed plastic bottles of pop collapse as the contents get old?

texts:
A number of bottles of pop (two varieties) in unopened plastic bottles have sat for a few years in a room-temperature environment. All of the bottles have now collapsed a certain amount (all to about the same degree).

They all started out under pressure from the carbonation, but now, not only is that gone, but the internal pressure has dropped below ambient. They all still have an "air" space above the liquid contents; not sure if it is or is not more than when originally purchased. If one of these bottles is opened, it draws in air and regains its original shape.

I have the following questions:

What happened to the carbonation? Did it leak out, or did it undergo some sort of chemical reaction, or perhaps both?
How could the pressure inside the bottle drop below ambient? What chemical or physical process is causing it, and what is driving the process? Why would it not simply reach equilibrium with ambient?
What would be the ultimate result if these bottles were left even longer?


texts: Difference between radial, planar, angular and spherical nodes

texts:
What is the difference between them?

I think radial nodes and spherical nodes are the same, and angular and planar nodes are the same.

Reference

Finally, how many spherical nodes are there in a $2p$ orbital?


texts: I want to print a structure of alumina, and the 3D printer that I am using is an extrusion-based printer. So I need your help in knowing that what composition (binders and deflocculant) of alumina will be suitable to print the 3D structure in such a manner that it holds its structure (as it is printed)? And to what extent should rheological properties be maintained so that structure doesn't fail?


texts: What is the structure of a lipid and why is this example non-polar?

texts:
Lipids usually consist of 3 fatty acids and 1 glycerol. I looked up what they look like

So how is it not a polar molecule?  The $\ce{-OH}$ side has negative charge, and the hydrocarbon side chain has a positive charge.


texts: How is the 'rate law' and 'order' for the ozone decomposition reaction can be defined?

texts:
How is the 'rate law' and 'order' for the following reaction can be defined?

$$\ce{2O3 -> 3O2}$$

"The expression that correlates the rate of reaction with concentration of reactants is known as rate law for that reaction."
So the rate law only include the concentration of reactants, not products.
But the rate law for this reaction is:

$$r = k[\ce{O3}]^2[\ce{O2}]^{-1}$$

where $k$ is rate constant.

"Order of a reaction is the number of reactant molecules whose concentration determines the rate expression."

Order for this reaction w.r.t. ozone is 2 and that w.r.t. oxygen is -1. But why we are considering oxygen, being a product of this irreversible reaction. This also means that the rate of this reaction will decrease with the increase in concentration of oxygen.

Now it seems that, this is a reversible reaction. But chemical kinetics is studied for only irreversible reaction?


texts: Do you need concentrated sulfuric acid to make Dische diphenylamine reagent and test for DNA?

texts: I'd like to do a DNA quantification experiment for a college project. I don't want to use 16 M sulfuric acid. Is it possible to use more dilute acid and get a reasonably good result?


texts: Determining Rate Law and Reaction Mechanism from Method of Initial Rates

texts:
The data collected from using the method of initial rates is tabulated above.
Suggest a rate law and a mechanism consistent with the data. State any assumptions.

My Attempt
Obviously B and D has no impact on the rate of the reaction. From the first table it appears that the reaction is first order in A, however this doesn't make sense when you examine the last two rows of the second table. Since the rate law is first order in A and is independent of B, decreasing the concentration of A by 4 and increasing the concentration of B by 4 should result in a fourfold decrease in the rate. However the rate of the reaction decrease by 2.5 times. So then my logic is somehow wrong.
Furthermore I am even more confused about the order of C. I know that concentration of C is inversely proportional to the rate of the reaction. However the reaction still occurs without the presence of C (evident by the first table). Doesn't this imply that the rate law is independent of the concentration of C?
From the comments below, I have realized that the rate order of B is in fact not $0$. However now I am even more confused. How can it be that the rate is not dependent on B when there is no C, but it is dependent on B when there is C present? What would its rate law be like?


texts: Adding an essential oil to WHO Handrub Formulation

texts:
I'm not a chemist, so I prefer to ask this question to some people, who definitely have knowledge in that area.

WHO Handrub Formulation is available here.
Ingridients: Ethanol 96%, Hydrogen peroxide 3%, Glycerol 98%, Sterile distilled or boiled cold water.

I would like to use it to produce 4l of handrub (I have 92% alcohol, and I re-calculated needed amounts).
Can I also add some essential oil to the formula? Only few drops or more ~10 ml?

For example:

Orange, ingridients: citrus aurantium dulcis peel oil expressed, linalool, citral
Spruce, ingridients: limonane, linalool, geraniol. INCI: oleum picea excelsa
Pine, ingridients/INCI: oleum phus silvestris
Lavender, ingridients/INCI: lavandula angustifolia oil, linalool, limonene

I just want to make sure that the final substance wouldn't be irritating to the hands nor cause any allergies etc. I also found this paper, where they added Piper nigrum Essential Oils to the formula.

Thank you for suggestions.


texts: What's special about the purine scaffold?

texts:
Purine is a remarkable substance, given Nature has chosen it as the scaffold for two nucleobases from DNA/RNA: adenine (A) and guanine (G). Its structure also appears in several other substances of biological interest, by substitution on the fused ring system, like these examples shown in Wikipedia:

The base ring system has 4 nitrogen atoms and 5 carbon atoms. Then I wonder, it's not hard to imagine isomers or at least similar compounds just by changing the positions of the nitrogen atoms around the rings, with a few constraints. The five-membered ring needs at least one N to maintain aromaticity in the pyrrole ring. It's better to have this N at the position where a glycosidic bond is expected, if we want to incorporate it in some kind of nucleic acid. Along the edge connecting the two fused cycles, it's better to have C, to avoid N atoms with four bonds. So we are left with the following template:

We can distribute the remaining 3 N and 3 C atoms among the 6 free positions in $6!/((6-3)! \cdot 3!)  = 20$ different ways.
So my question is, what's special in purine, that caused its scaffold to be picked among all the other possibilities?


texts: What does it mean for a reaction to favor the reactants/products?

texts:
(This example is purely hypothetical.)

You have the reaction $$\ce{H2(g) + O2(g) <=> H2O2(g)}$$

at $T = 500\ \mathrm{K}$. The reaction reaches equilibrium at the following concentrations:

$$\ce{[H2]} = \ce{[O2]} = 5 \times 10^{-3}\ \mathrm{mol\ dm^{-3}}$$
$$\ce{[H2O2]} = 4\times10^{-5}\ \mathrm{mol\ dm^{-3}}$$

This gives $$K_c = \left(\frac{\ce{[H2O2]}}{\ce{[H2][O2]}}\right) = 1.6$$

However, the total concentration of the reactants is $250$ times higher than the concentration of the product.

Still, as $K_c > 1$, per definition, the products are favored.

This seems counterintuitive to me, and my Chemistry teacher couldn't really explain it to me, so I was hoping someone here could explain why, even when the reactants are so much more plentiful, the products are considered to be favored.


texts: Bromination with NBS on cyclic structures

texts:
I found this question and the answer as shown in my book. I didn't understand why the bromine particularly entered the position shown in the answer.

First of all, if a free radical was generated there it would be 2°, and also will have resonance. Is any other product possible or this is the only major product?

Also, is this allylic bromination? Every allylic position is also a vinylic position — I am not getting it.


texts: Calculating the charges of anions and cations

texts:
I am new to chemistry. Could someone explain me how to calculate the charges on anions and cations. I've heard about some crossing method (the left subscript becomes the right superscript and the right subscript becomes the left super script.)

Example: $\ce{Rb2S -> 2Rb+ + S^2-}$

But what about:
$\ce{K2MnO4}$ and $\ce{Zn(ClO)2}$

This trick doesn't seem to apply here, so how can I find out the charges?


texts:
I am using this Mocha Coffe.

When I try to dissolve it in a cupful of cold water, it forms a globule of powder and does not dissolve.

But if I add a small amount of water to the powder and mix it, it makes a paste which will dissolve in more water. What is happening here ?


texts:
In my organic chemistry lab, we recently had an experiment where we were given a mixture of 50:50 ethanol & ethylene glycol. We were supposed to perform a simple distillation to calculate the percent recovery. Based on my readings, I found that the ethanol has a lower boiling point than ethylene glycol and concluded that ethanol would be the compound that would vaporize and transfer over to the cooled flask where it could condense back. At the end of the lab, we just weighed the distillate and the holdup.

My question was, how do you know if the simple distillation process was successful? I assumed that it was successful based on the fact that it produced a distillate, but I realized that can't be the only reason. The difference in boiling point was large enough to be performed as a simple distillation, but how can I conclude that it was overall successful?

Also, based on this, can I figure out if there is an azeotrope for the boiling points of the two compounds? I read that azeotropes "prefer" to be boiled into the gas phase together, but doesn't that imply that both compounds could have condensed, making the simple distillation process unsuccessful?


texts:
I have $20~\mathrm{cm^3}$ of a $0.1\ \mathrm{M}$ ethanoic acid solution and have to find out the $\mathrm{p}K_\mathrm{a}$.

In experiment this solution had a $\mathrm{pH}$ of $2.91$.

Do I use the formula $\mathrm{p}K_\mathrm{a}= 2 \mathrm{pH} + \log(c (\mathrm{acid}))$ ?

What I do not understand is that my $\mathrm{p}K_\mathrm{a}$ value varies. I measured many solutions with 18:2, 15:5, 10:10 sodium ethanoate/ethanoic acid composition. Which I calculated with the formula $\mathrm{p}K_\mathrm{a} = \mathrm{pH} - \log \frac{c(\mathrm{salt})}{c(\mathrm{acid})}$

I get close values but not the equal.  So the one above would be $\mathrm{p}K_\mathrm{a}=4.82$   and another value I obtained is $4.62$ (for the 15:5 solution with $\mathrm{pH}\ 5.11$).

Is this deviation purely due to experimental inaccuracy or does the composition matter.   Would it make more sense to use the literature $\mathrm{p}K_\mathrm{a}$ value for further calculation rather than those experimental ones?


texts: Why is the energy levels in hydrogen independent of the quantum numbers l and ml?

texts: I've been looking for an answer for this for quite a bit but I'm still quite confused. On the independence from ml, I think that it originates from the symmetry of the molecule. However, the independence from l, is what confuses me. Others have mentioned that it is due to the fact that the potential energy is purely Coulombic and related to the 1/r aspect. However, my textbook shows that the effective potential energy (related to the radial wavefunction) actually depends on two things: the Coulomb potential energy and the centrifugal force from angular momentum. The latter has the l quantum number, so when l = 0, the effective potential energy is purely coulombic. However, when l is not 0, the effective potential isn't purely Coulombic, which contradicts my earlier statement. So I'm a bit confused on whether the potential energy is purely coulombic/not, or if we are referring to different potential energies?


texts: Understanding the partial derivative of temperature with respect to thermodynamic beta (coldness)

texts:
I am trying to prove that the specific heat is related to the fluctuations in the energy:

$$c_V = \frac{\langle E^2 \rangle - \langle E \rangle^2}{k_\mathrm BT^2}$$

Where:

$$\beta = \frac{1}{k_\mathrm BT}$$

$$\langle E \rangle = -\frac{ \partial \log(Z)}{\partial \beta}$$

I did:

$$\frac{\partial^2}{\partial \beta^2}\ln Z = \frac{\partial}{\partial \beta}\frac{1}{Z}\frac{\partial Z}{\partial \beta} = -\frac{\partial \langle E \rangle}{\partial \beta} = -\frac{\partial \langle E \rangle}{\partial T} \frac{\partial T}{\partial \beta}$$

My issue is that I do not understand why:

$$-\frac{\partial T}{\partial \beta} = k_\mathrm BT^2$$


texts: What the difference in data if calibrate pH-meter with 2 and 3 solutions?

texts:
pH-meter (12 bucks one) can be calibrated with 2 different solutions (let's say 4.0 and 6.86), but as an option 3 can be used (4.0, 6.86 and 9.18). If I use 2 instead of 3, what error I'm going to get.
For instance I need to determine if liquid higher or lower than 5.5.


texts: Can the rate of reaction of a Voltaic/Galvanic cell be determined theoretically?

texts:
I am conducting a chemistry practical in which I measure the voltage of a Zn-Cu Voltaic cell over time.

Assuming that the surface area of the electrodes are known, concentration of reactants are known, wire resistance is known (Could assume negligible for simplicity).
Is it possible to determine the rate of the reaction for this setup?
Could I then determine respective concentration of reactants? This would enable the use of the nernst equation to determine theoretical voltage.

Many thanks,


texts:
Period 1 of the periodic table contains 2 elements ($1s^1$ and $1s^2$).

Period 2 contains 8 elements ($2s^1$, $2s^2$, $2p^1$, $2p^3$, ..., $2p^6$).

By the same argument, period 3 might contain 18 elements ($3s^1$, $3s^2$, $3p^1$, $3p^3$, ..., $3p^6$, $3d^1$, $3d^2$, $3d^{10}$). Why does period 3 of the periodic table contain 8 elements instead of 18?

I think that it could be explained by means of atomic stability, but I need help to understand what happens.

Thank you in advance.


texts:
I am trying to calculate the energy levels of biphenyl (see picture below) using Hückel method. Since this is my first time using Hückel I am a little confused.

Biphenyl has 12 carbon atoms, therefore I should get a 12x12 matrix like the one below.

\begin{array}{cccccccccccc}
\alpha-E & \beta & 0 & 0 & 0 & \beta & \beta & 0 & 0 & 0 & 0 & 0 \\
\beta & \alpha-E & \beta & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & \beta & \alpha-E & \beta & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & \beta & \alpha-E & \beta & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & 0 & \beta & \alpha-E & \beta & 0 & 0 & 0 & 0 & 0 & 0 \\
\beta & 0 & 0 & 0 & \beta & \alpha-E & \beta & 0 & 0 & 0 & 0 & 0 \\
\beta & 0 & 0 & 0 & 0 & \beta & \alpha-E & \beta & 0 & 0 & 0 & \beta \\
0 & 0 & 0 & 0 & 0 & 0 & \beta & \alpha-E & \beta & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & \beta & \alpha-E & \beta & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & \beta & \alpha-E & \beta & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & \beta & \alpha-E & \beta \\
0 & 0 & 0 & 0 & 0 & 0 & \beta & 0 & 0 & 0 & \beta & \alpha-E
\end{array}

Is this matrix correct for biphenyl, if I neglect dihedral angles etc.?

If I take det(Matrix)=0 and solve this for the Energy term I should get several solutions. How can I assign these solutions to each energy level correctly?


texts: What is the product when Lithium solid is dropped in water?

texts: I am working on reaction predictions for the AP Chemistry and I need some help with this problem. On a practice quiz I tried to use the rule of "Metal + Water = Metal Oxide" so I answered with $\ce{2Li + O^{2-} -> Li2OH}$. I got zero points for this answer meaning both reactants and products were wrong. What is the correct answer and how would you get to the correct answer?


texts: Energy of the Orbital versus Energy of the Electron

texts:
When introducing the hydrogenic atomic orbitals, it is said that the 2s and 2p orbitals are degenerate. I have also read that for atoms with more than one electron, like He, the 2s and 2p are NOT degenerate.

How does the addition of a second electron in the 1s orbital change the energy of the 2s and 2p orbitals?


texts: How different concentration of HCl on magnesium affect the enthalpy change

texts: I had conducted an experiment where I reacted a $0.3\ \mathrm{g}$ strip of magnesium with $100\ \mathrm{mL}$ of varying concentrations of $\ce{HCl}$: $1\ \mathrm{mol/L}$, $2\ \mathrm{mol/L}$ and $3\ \mathrm{mol/L}$. From the data I collected, I noticed that the reaction with $1\ \mathrm{mol/L}$ $\ce{HCl}$ produced the most energy and the reaction with $3\ \mathrm{mol/L}$ $\ce{HCl}$ the least. I just wanted to know if my data is correct or not because I hypothesized that the $3\ \mathrm{mol/L}$ reaction would produce the most heat energy.


texts: Byproducts of the neutralisation of hydrochloric acid with sodium hydroxide

texts:
Given a 1 M concentration of $\ce{HCl}$ and $\ce{NaOH}$ here are the pHs:

pH of $\ce{HCl}$: 1

pH of $\ce{NaOH}$: 13–14

and of course water has a pH of 7.

Here is a reaction that is most likely to occur:

$\ce{HCl + NaOH + H2O <=> H2O + NaCl(aq)}$

However I think that other reactions are theoretically possible.

Like for example theoretically sodium oxides could form from the $\ce{OH-}$ taking a proton from another hydroxide anion thus giving you $\ce{O^2-}$ which could react with the sodium to give you $\ce{Na2O}$ which is a sodium oxide.

I also think that theoretically $\ce{Cl-}$ could steal electrons from the $\ce{OH-}$ since $\ce{Cl}$ can exceed an octet of electrons. This would give you neutral $\ce{OH}$ which could then react with another chloride anion to give you $\ce{OHCl-}$(not sure if formula is written right or if it would be negatively charged) or in other words chlorine hydroxide. The proton could then be taken by another hydroxide anion giving you $\ce{OCl}$ also known as chlorine monoxide which could react with another chlorine to give you $\ce{OCl2}$ which is dichlorine monoxide.

Do these theoretical reactions that lead to oxyanions($\ce{O^2-}$ to be specific), chlorine oxides, chlorine hydroxides, and sodium oxides actually happen to some extent when you have $\ce{HCl}$ and $\ce{NaOH}$ in aqueous solution


texts: How the crystal structure varying for the same compound?

texts: i have synthesized the crystal Cyclohexylammonium acetate. Structure of this compound was already solved and it s under centro symmetric space group I2/a. But when i took single crystal analysis it comes under monoclinic C2/c space group. What is the reason for getting this kind of results?


texts: Which proton is more acidic in this compound?

texts: I'm having trouble determining which of these protons is more acidic. I was thinking the solution had something to do with the double bond in the aromatic ring, but I'm still not sure.


texts: Why does bond breaking in ATP release energy?

texts:
We always come across that formation of bonds releases energy, and bond breaking requires energy, but in the case where ATP converts into ADP or AMP (bond breaking), energy is released. Why?

Further, how bond formation releases energy?


texts: Spiralling of electrons into the nucleus

texts:
A drawback (and a major one) of Rutherford's model was that the electrons, being accelerated charged particles, would gradually spiral into the nucleus and collapse into it. My question is how did Bohr rectify this drawback in his own model.

In Bohr's model too, electrons move in a circular path, which means they are accelerated. Thus, going by Electromagnetic theory of Maxwell, those accelerated electrons should radiate out their energy, and collapse into the nucleus, just like they did in Rutherford's model. However every book mentions that this does not happen in Bohr's model. Why not?

Please tell me where I am wrong, because this problem has been disturbing me for quite long now.


texts: How does one prove Avogadro's law from Gay-Lussac's?

texts:
To understand Gay-Lussac's law, Amedeo Avogadro said

In equal volumes of air under constant temperature and pressure, there are equal number of atoms (or molecules).

Let's take a hydrogen and an oxygen molecule. As the latter is larger in size, when stored in two separate equally-volumed containers, doesn't oxygen increase the pressure inside that container, if the same number of molecules occupied each container? (Does this make Avogadro's statement of constant pressure go wrong?) Again,
$$2mvN\cos\theta = F,$$
where $F$ is the force acting on the walls of the container, $N$ is the number of collisions of the molecules with the walls, $2mv$ is the change of momentum of the molecules, and $\theta$ is the angle of collision of the molecules on the walls.
Therefore, if Avogadro was correct, could anyone give me any reason why $N_\ce{H2} > N_\ce{O2}$ or $v_\ce{H2} > v_\ce{O2}?$
If Avogadro was correct, the above conditions must hold, as $m_\ce{H2} < m_\ce{O2},$ right?
Could you please prove the above phenomena happen when Avogadro's statement above holds?


texts: What is the difference between an ion-induced dipole attraction and just an ion-dipole attraction?

texts:
By what I've read, an ion-induced dipole attraction is a weak attraction that results when the approach of an ion creates a dipole in a non-polar atom or in a non-polar molecule by disturbing the arrangement of electrons in the non-polar species. So this is a dispersion/van-der-Waal force, I believe?

On the other hand, an ion-dipole attraction is a weak attraction that results when the approach of an ion interacts with the dipole in a polar atom or in a polar molecule. And so this wouldn't be a van-der-Waal force would it?

If what I said above happens to be true, does the same apply with dipole-induced dipole forces and just dipole-dipole forces?

In this scenario, a dipole-induced dipole attraction would be a weak attraction that results when the approach of an dipole (polar covalent bond) creates a dipole in a non-polar atom or in a non-polar molecule by disturbing the arrangement of electrons in the non-polar species. So this is a dispersion/van-der-Waal force too, right?

And a dipole-dipole attraction would be a weak attraction that results when the approach of an dipole that already exists  in a polar bond attracts with another dipole in another polar atom or in polar molecule.


texts: What is the difference between the Joule and Joule–Thomson coefficients?

texts: Is there a difference between the Joule coefficient and the Joule–Thomson coefficient? Also, I am having a hard time understanding what they mean.


texts: What is the reason behind electron transition in the flame test

texts:
I am a beginner in this topic but I am aware that when flame test (for alkali and alkaline earth metals) is done there is a s-s transition of electrons from the ground to their excited state.

But I don't understand why the electron needs to transit back to their ground state if I consider that the temperature of the oxidising or non luminous flame (that is the energy supplied to the electron) remains constant.

So my question is

Why does the electron release the absorbed energy and transit back to the ground state even though a constant external energy is supplied to it?

In other words, what is the need for the electron to absorb the energy , then reach the excited state and release the energy to transit back to the ground state. Instead why does it not remain in the excited state after absorbing the required amount.


texts: What's the difference between pipettes calibrated "TD", "TC", "Blow-out" and related terms?

texts:
I've never blown-out the last drop of any glass pipette I've ever used during my undergraduate studies. Recently I re-read some notes I had lying around in order to prepare a class I had to give to a group of first year undergraduates and found out that there is a class of glass pipettes which need to be "blown-out" in order to deliver the nominal volume correctly.

I researched a little bit and found what seems to me to be completely inconsistent terminology and conventions to refer to this class of pipettes.

In https://en.wikipedia.org/wiki/Graduated_pipette it is clearly stated that there are "two kinds" of graduated pipettes. "serologic/blow-out" and "Mohr/drain-out". It is also stated that serologic pipettes have calibration marks all the way to the tip, whereas Mohr pipettes do not. The same page states that pipettes are either calibrated "to deliver" (TD) or "to contain" (TC). It states that "TD" is a far more common calibration than "TC" and explains that pipettes calibrated TC need to be blown-out in order to deliver the expected volume correctly, one would assume from this that TD is a synonym fro "blow-out". Judging from this there would seem to be two kinds of pipettes, "serologic/blow-out/TD" and "Mohr/drain-out/TC". This really contradicts my experience, I've been using pipettes with marks going all the way to the tip and never been told to blow out the last drop, however, there is always the chance I've been doing it wrong this whole time.

Digging a little bit deeper I found that this document http://www.brand.de/fileadmin/user/pdf/Information_Vol/Brochuere_Volumenmessung_EN.pdf (link downloads pdf) that wikipedia lists as a source doesn't mention "blow-out" pipettes at all, but does mention pipettes calibrated "TC". In page 13 there are some pictures and descriptions of pipettes resembling what one would think are "Mohr" and "Serologic" types, and both are said to be calibrated "to deliver" actually, reading this text one would think that ALL graduated and volumetric pipettes are calibrated to deliver (however, this document is from a lab equipment manufacturer, perhaps they only manufacture TD pipettes...?).

Digging yet deeper http://faculty.clinton.edu/faculty/Mike.Lawliss/My_webpage/Sci110/Other%20documents/Pipetting%20A%20Practical%20Guide_Guzman2001.pdf is another article cited as a source by wikipedia. Here the author pretty much identifies serologic pipettes with blow-out ones, but also states that blow-out pipettes "usually" have double rings (non-colored) near the top. There is, however, a drawing of a "serologic" pipette WITHOUT rings near the end of the article, close to an "Ostwald-Folin" pipette WITH rings which the author specifically identifies as blow-out. The definition of the term "serologic" pipette is, according to the author, "a type of measuring pipette used to measure variable volumes" which in my view would make ALL graduated pipettes serologic.

To add to all this confusion Sigma-Aldrich seems to manufacture "TD, blow-out, serologic pippetes" http://www.sigmaaldrich.com/catalog/product/sigma/z325422?lang=es&region=AR and also "TD/TC volumetric pippetes", which makes me lose all hope of making sense of any of the terms listed in the question at all.

In short, is there a STANDARD way in which these terms (TD, TC, IN, EX, Blow-out, Serologic, etc) are used? Is there a standard definition regulated by some sort of organization, or at least generally agreed upon? If you think that there is, could you please provide trustworthy sources? Thanks a lot.

This probably seems like a silly question (it is =D) but it kind of bugs me not to know something so basic as "what are the different kinds of graduated pipettes?"... It seemed like something that would be quite easy to settle when I started looking into it... guess I was wrong.


texts: Since the formation of diamond from Graphite is endothermic and the entropy decreases for this process, how is it possible to make diamond?

texts: Surely G would always be positive and thus would make it impossible to make diamond. Clearly this is not the case. But how? Would an increase or decrease in temperature aid it's formation? I think a decrease in temperature would favor diamond but wouldn't this contradict le chatilier's principle?


texts: If there are two longest chains possible in an organic compound and both have the same number of substituents, how do we decide the parent chain?

texts: Is the parent chain in the above case determined by atomic mass, alphabetical preference or any other rule?


texts: Would adding acetic acid from household vinegar to washing machine make it too dilute to be effective?

texts:
Many people advise adding a cup of acetic acid (vinegar) to one's laundry during the clean cycle. From my calculations, considering one cup of acetic acid and a top gallon machine (at 40 gallons), it would seem this would completely dilute the concentration next to nothing.

Is this correct or am I missing something? Someone had mentioned something about acetic acid being a weak acid, but I'm not sure what that means in this context.


texts: Intermolecular forces in Carbon Nanotubes?

texts: What are the intermolecular forces that can be found in Carbon Nanotubes?


texts:
The problem is:

A quantity of $\pu{35.2 g}$ if a certain hydrocarbon gas, occupies $\pu{13.2 L}$, measured at $\pu{1 atm}$ and at $\pu{323 K}$. Knowing that 85.5% of is C, find the molecular formula for the hydrocarbon.

Attempt. So I tried with the first step doing $0.85\cdot \pu{35.2 g} = \pu{29.92 g}$ of C and I'm pretty sure that's the wrong step but I'm not fully sure, so anyways, I continue. After finding the mass of C on the hydrocarbure, I subtracted $35.2 - 29.92 = \pu{5.28 g}$ of $\ce{H}$ to get the mass of $\ce{C}$ on the hydrocarbon. Now basically:
$$\pu{29.92 g} \text{ of C}\cdot \frac{\pu{1 mol}~\ce{C}}{\pu{12 g}~\ce{C}} = 2.5$$
$$\pu{5.28 g} \text{ of H}\cdot \frac{\pu{1 mol}~\ce{H}}{\pu{1 g}~\ce{H}} = 5.28$$
and this is why I think I'm wrong, I can't get a relationship of natural numbers for the empirical formula. May anyone give some input on this?
Continuation. So bravely approximating to the empirical formula by diving by the smaller one, i get $\ce{(C1H2)_n}$ so the empirical molar mass call it, $M_\text{empirical} = 12 + 2 = \pu{14g/mol}$. Getting the $n$:
$$n = \frac{M_\text{real}}{M_\text{empirical}} = \frac{M_\text{real}}{\pu{14g/mol}}$$
and to get the $M_\text{real}$, we go to
$$PV = nRT \implies PV= \frac{m}{M_\text{real}}RT \implies M_\text{real} = \frac{mRT}{PV}$$
hence
$$n=\frac{\frac{mRT}{PV}}{\pu{14g/mol}} = \frac{\frac{\pu{35.2 g}\cdot \pu{0.082 L atm//K mol}\cdot \pu{323 K}}{\pu{1 atm}\cdot \pu{13.2 L}}}{\pu{14g/mol}} = 5$$
then I get $\ce{(C1H2)_5}$ hence $F_\text{molecular}=\ce{C5H10}$. Yes, right?


texts: Could I settile for galvanized steel over stainless for salt corrosion resistance?

texts:
Bear with me, I'll get to the chemistry soon.

I have a float tank that I want to attach a skimmer to.  Unfortunately, the enclosure is weakened by cutting a hole out of the ABS plastic.  The weight of the salt water (1.25SG) to somehow causes a bend in the plastic just enough that getting a good seal isn't possible without additional support.

The float tank consists primary of (pardon the units) 800lbs of $\ce{MgSO4}$ Heptahydrate raised to about 96 degrees Fahrenheit.  The pH is roughly 7.2.

My concern with supporting the ABS plastic is that the Epsom salt water may corrode the metal, if it somehow isn't protected by a liner.  Would I absolutely need to have stainless steel, or could I get by with galvanized (which is much cheaper).

In case it matters, I estimate the volume of water directly pressing on the skimmer opening to be about 9+ gallons (again at 1.25sg).

Thank you for answering non-chemist,
Ben


texts: How does hyperconjugation explain the stability of alkenes?

texts: The more the number of alpha hydrogens, the higher is the stability of alkenes, because the more the number of hyperconjugative structures. Why is this so? Has it got something to do with the electrons being easily delocalised?


texts: Citric acid rust removal and neutralization

texts:
I'm currently removing rust from steel with citric acid dissolved in water. I generally use a wire brush as the final treatment to remove any surface rust that the acid loosened up. The pieces under treatment end up shiny before being painted over for renewed protection.

I haven't found any authoritative answer on this, but online search results seem to recommend soaking the parts in a solution of baking soda as the final treatment after the citric acid. The idea being to neutralize the acid.

What is the purpose of the neutralization step in this scenario? Does it effectively reduce how prone the acid-treated steel is to rusting again?

And assuming the acid actuates on the surface of the steel, would the wire brush treatment be a substitute for the baking soda, if  it effectively removes some of the acid-treated metal from the outer layer?

Background: Electrical Engineering. But my Chemistry is indeed very rusty (no pun intended).


texts: What is the pKa of the hydronium, or oxonium, ion (H3O+)?

texts:
Although the wikipedia page on Hydronium indicates a $\mathrm{p}K_\text{a}$ of −1.74, I noticed in the discussion of this page that the subject seems debated (cf. http://en.wikipedia.org/wiki/Talk:Hydronium#pKa.3F) since alternative (apparently more rigorous) reasoning leads to $\mathrm{p}K_\text{a} = 0$ for $\ce{H3O+}$.

Also, many demonstrations lead to $\mathrm{p}K_\text{a}$ and $\mathrm{p}K_\text{b}$ of 15.74 for $\ce{H2O}$ and thus, using $K_\text{w}=[\ce{H+}][\ce{OH-}]=10^{-14}$, give $\mathrm{p}K_\text{a}$ and $\mathrm{p}K_\text{b}$ of −1.74 for $\ce{H+}$ and $\ce{OH-}$ respectively. But those demonstrations seem to make use of the concentration $[\ce{H2O}]=55.56~\text{mol/L}$ instead of the activity $a_{\ce{H2O}}=1$ (for a solvent) in the equilibrium constant of the reactions.

So it seems to me that the $\mathrm{p}K_\text{a}$ of $\ce{H3O+}$ must be equal to $0$.

Is this question still debated?

PS1:
To add details about the question, the debate in the references mentioned in the discussion on the wikipedia page as well as in the link provided by Nicolau Saker Neto bellow seems to boil down to the coexistence of two different definitions for the equilibrium constant:
- one based on the activities of the compounds
- the other derived from the 'mass action law' and which thereby uses the molar fractions of the compounds
Reading through the Callen (Thermodynamics and an Introduction to Thermostatistics) gives me the impression that the derivation from the mass action law of an equilibrium constant involving molar fractions is based on the assumption of an ideal fluid. However, it is precisely the departure from ideality that seems to justify the use of activities instead of molar fractions. Is that correct?

PS2:
Another point, which I have not looked in details yet, seems to be a debate about the possibility to apply the definition for $K_\text{a}$ to the water molecules $\ce{H2O}$ considering that they are not a highly diluted solute since they constitute the solvent. Is this a valid issue and should then the acidity of $\ce{H3O+}/\ce{H2O}$ be determined in another solvent than $\ce{H2O}$ to be compared with the other acids?


texts: What dictates cathode vs anode nomenclature use?

texts:
what was the justification for the use the cathode and anode terminology in IEF?

There is no redox taking place in IEF, just proteins interacting with an electric field


texts:
Micellisation is found to be spontaneous i.e. $\Delta G < 0.$ It's found that $\Delta S > 0,$ which was intuitive since, solvated molecules are released. And, it may be most loosely started that $\Delta H > 0$ i.e endothermic at low temperature and exothermic ($\Delta H<0$) at higher temperatures. Guess why?
Hint, derive that $\Delta H^\circ=-RT^2 \dfrac{\mathrm d(\ln{\text{CMC}})}{\mathrm dT}$. And CMC may be defined as CMC as the point corresponding to the maximum change in gradient in an ideal property–concentration $(\phi$ against $S_\mathrm{tot})$ relationship $\dfrac{\mathrm d^3\phi}{\mathrm dS^3_\mathrm{tot}} = 0.$

(emphasis mine)
Why was most loosely stated term used in the text? Isn't it true? Excluding non-dressed micelle model, $\Delta G$ can be shown to be approximately $(1 + \beta)\ln{\text{CMC}}$.
Writing $\Delta H^\circ = \Delta G^\circ + T\Delta S^\circ$ and plugging in the values I couldn't get the desired term. Is my process correct?
Also, what's the meaning of “ideal property–concentration”?


texts: Why doesn't nitrogen react with oxygen at room temperature?

texts:
I already know that nitrogen's triple bond requires a lot of energy to be broken, so the activation energy is very high, but the book also lists the endothermic energy change as a reason.

Does the positive enthalpy change have something to do with the reaction not being spontaneous i.e. due to positive free energy?
Is there a link between $E_a$ and free energy when deciding whether a reaction will occur?


texts: Why doesn't 4 hydrogen and 1 carbon form a ionic bond? What is the limit of electrons that can be given away?

texts:
I understand that it's a covalent bond, but to my uneducated mind isn't it possible to have the carbon give 1 electron to each of the hydrogens and form an ionic bond instead? I read this response

Why can't carbon form an ionic bond?

which kind of makes sense, which leads me to my main question. Is there a limit to how many electrons(in this case) a carbon can drop/give before it's not possible? Does it depend on how badly the other(s) elements want to take/give electrons in said reaction?

As in, it has to give up 4 electrons, would it be fine it if had to give up 2? etc, hopefully my question makes sense.


texts:
I'm so confused... $\ce{HClO}$ is a weak acid. then why is its conjugate base, $\ce{ClO-}$, a weak base in water? shouldn't they be inversely proportional? shouldn't $\ce{ClO-}$,  be a strong base?

If $\ce{HClO}$ is a weak acid, that means it does not readily give up a proton and has a strong pull on them. So when it becomes a conjugate base, $\ce{ClO-}$, shouldn't it readily take protons and therefore be a strong base in water?

ALSO,
when an acid is dissolved in water, and some of that acid dissociates into $\ce{H3O+}$, is the Kw of water negligible and you only consider the Ka when finding pH? But that confuses me because I thought you use 14, the exponent of Kw when finding pH.


texts: Copper substituting silver in Tollen's reagent

texts:
I am an artist attempting to use Tollen's Reagent in a number of my projects.

Is there any reason I could not substitute Copper Nitrate for the Silver Nitrate in the reaction? Would the copper adhere to the glass?


texts: How it was observed, that elements in columns 6 and 11 assume abnormal electron configuration?

texts: Reading this question about why do elements in columns 6 and 11 assume abnormal electron configurations I wondering, how this was observed.


texts: Potassium tert-butoxide reaction with chloroform and picric acid

texts:
If potassium tert-butoxide is used in a solution of chloroform and and a strong protic acid like picric acid will the tert-butoxide ion react with picric acid or will it form a dichlorocarbene.

Mechanism for reactions will be much appreciated.

(This is most definitely NOT a homework question!
I need to know this to solve my homework problems)


texts: Regioselectivity of epoxide hydrogenation using Pt versus Ni catalyst

texts:
What conditions are applicable for the transformations X and Y, respectively?
  (a) $\ce{LiAlH4}$, and $\ce{NaBH4}$
  (b) $\ce{NaBH4}$, and $\ce{BCl3}$ followed by $\ce{NaBH4}$
  (c) $\ce{LiAlH4}$, and $\ce{AlCl3}$ followed by $\ce{LiAlH4}$
  (d) $\ce{H2/Pt}$, and $\ce{H2/Ni}$

This question is about the hydrogenation of an epoxide (2,2,3-trimethyloxirane) to two different alcohols (2-methylbutan-2-ol and 3-methylbutan-2-ol). I put (c) as my answer, but apparently (d) is also a correct answer as well.

I have never seen the difference in reduction by change of catalyst, so had no idea about option (d). Is there any difference?


texts:
While reading applications of coordination compounds, I read that Hardness of water can be checked using Na2EDTA in hard water containing Ca+2 and Mg+2 which form complexes with EDTA.

Also, Lead (Pb), a  p block element is removed by using EDTA in case of lead poisoning.

Can elements other than those of d block form complex compounds? Like Ca(II) or Mg(II).
How are such complexes stable?
Can we desrcibe crystal splitting in them?


texts:
Reaction of $\ce{(Cp)Co(Me)2(CO)}$ in the presence of excess $\ce{CO}$ yields two different organic products, $\ce{A}$ and $\ce{B}.$ The only metal-containing product is $\ce{(Cp)Co(CO)2}.$ The IR spectrum of $\ce{A}$ contains a peak at $\pu{1731 cm-1}$ whereas that of $\ce{B}$ has no peak in the carbonyl region. Write down mechanisms that explain the formation of $\ce{A}$ and $\ce{B}$.

From the IR, I think it is likely that an aldehyde is being produced, and looking at the reaction I assume it is the alkyl insertion of the methyl into the $\ce{CO}$ forming ethanal $(\ce{A}).$

$\ce{B}$ is confusing me however as the only other reactants are $\ce{Me}$ and $\ce{CO}$ (as the $\ce{Cp}$ remains in the metal product). Is some other reaction occurring (is $\ce{B}$ simply the enolised form of $\ce{A}$ formed from a β-hydride shift)?