texts: Rate equation for a reaction involving a polymer having absorbed small proteins according to langmuir's model

texts:
First, let me apologize for the awful question title..

I have a solution with polymers with $N$ binding sites and small proteins, which can attach to a binding site. The polymers will absorb the proteins till $N^*$ out of $N$ sites are occupied. From that moment the polymer can undergo a certain structural deformation and will drop some small proteins in the process.

My problem is this: I would like to write down the rate equations of the problem and I thought that langmuir's model would be a good way to describe the absorption of the proteins to a polymer. However, this theory gives the rate of the surface decomposition $\theta$, but I would like to be able to let the polymer undergo the deformation reaction (involving the concentration of polymers having absorbed $N^*$ proteins). How can I incorporate the langmuir model in the "ordinary" set of first order rate equations? How can I get to a numerically solvable system of equations that describe the kinetics of this problem having so many absorbing surfaces (i.e. polymers)?
In other words, is there a way to obtain the concentration of polymers having a certain $\theta$?


texts: When discussing the solvent uptake of a metal-organic framework would the correct term be "solvent molecules were enclathrated into the pores"? Despite searching for a definition online I have drawn a blank and its not a term I am familiar with. Having read many papers in polymer chemistry where this term is also used I wonder if I have misunderstood its usage.


texts: What does it mean that an electron pair "spends more time" nearer an atom?

texts:
In a book I am reading, it is said

  In the $\ce{HCl}$ molecule, the shared pair of electrons spend more time nearer the chlorine atom. In the $\ce{HF}$ molecule, the shared electrons spend more time nearer the fluorine atom.

What does "spend more time" mean here? Has this been experimentally validated? If yes, how?


texts: Molar conductivity of a strong electrolyte

texts:
In 1910, Kohlrausch showed that the dependence of the molar conductivity of strong electrolytes is well described by the following equation:
$$\Lambda_m = \Lambda_m^\circ-K\sqrt{c}$$
This equation, known as Kohlrausch's law, states that the molar conductivity of strong electrolytes decreases with the square root of the concentration, with slope given by the quantity K (Kohlrausch's parameter). It is also found that this slope of the stoichiometry of the electrolyte.
I need to find for a paper the slope value for magnesium chloride, MgCl2, and the molar conductivity for different concentrations. But, I can't find this experimental data anywhere. I hope you can help me.


texts: Using the right equipment for successful detection of Novichok

texts:
Apparently, Navalny’s biomaterials were flown to Moscow's Nii Sklif lab which didn't find any traces of the poison. But they used an American Agilent Technologies GC-MS [1], while Bundeswehr toxicology lab reportedly used an order of magnitude more sensitive, and more expensive, Bruker's apex-Qe FTMS (no official source for this as "Bundeswehr didn’t disclose the details of their work") which successfully detected novichok.
How did German scientists outplay their Russian counterparts in this case and could it be attributed to simply using a more sensitive equipment with perhaps a better MS method?


texts: alpha-hydrogen atom and keto-enol tautomerism

texts:
The following is an extract from my book-

  For an aldehyde or a ketone to exhibit keto-enol tautomerism, it is essential that it must have atleast one $\alpha$-hydrogen atom. Thus, acetophenone, butan-2-one and propionaldehyde all contain $\alpha$- hydrogen atoms and hence show keto-enol tautomerism. In contrast, benzaldehyde, benzophenone etc. do not contain $\alpha$-hydrogen atoms.

What is meant by $\alpha$-hydrogen atom? How does it affect keto-enol tautomerism?


texts: How to confirm the type of bonding taking place between two substances?

texts:
For example ink on paper: how can I confirm that the bonding is van der Waals and not covalent? Similarly, the same question can be asked about other interaction such as hydrogen bonding, ionic bonding, etc.

Are there analytical or spectroscopic methods for this purpose?


texts: DFT: Can the calculated enthalpy of two systems that aren't isoelectronic be compared?

texts:
As a simple example, say I wish to calculate the product of a reaction between methyl iodide and triethylamine, then compare it with the product of benzyl iodide and triethylamine. My goal is to compare the products' relative stabilities (in a larger system this could be useful to compare reactivity options on a common substrate). I couldn't just calculate triethylmethylammonium's enthalpy and compare it with benzyltriethylammonium, right? I would expect the system with more electrons/bonds to always have a lower enthalpy value.

Alternatively, I could calculate all the reactants as well as products, including the iodide as a non-coordinating anion, then subtract the reactants from the products. This difference I could then use to compare the relative stability of the two products, am I correct in this? My worry with this approach is whether DFT can model the non-coordinating anion accurately, as well whether its result would mean anything without solvent effects. It feels like the rabbit hole can always go deeper, and I guess I am curious at what point I obtain qualitatively useful results.


texts:
Which allotrope of phosphorus is kinetically the most stable?

I ruled out white and yellow as being quite reactive.

Red and black allotropes are both polymeric and comparitively less reactive.

Black looks the most stable one thermodynamically. But kinetically, I have no idea whether it should be red or black.
The answer provided to me is Red.

(Relevant chat discussion)


texts: Percentage purity of Ba(MnO4)2 sample that completely reacts with given H2O2?

texts:
$\pu{40 g}$ $\ce{Ba(MnO4)2}$ (mol. wt. = 375) sample containing some inert impurities in acidic medium is completely reacted with $\pu{125 mL}$ of $\pu{3 M}$ $\ce{H2O2}$. What is the percentage purity of the sample?

I actually found this question in a book, I found its solution but I cannot properly understand it. This is the first equation given:

Since milliequivalents of $\ce{Ba(MnO4)2}$ = milliequivalents of $\ce{H2O2}$
$$(w/375)\times10\times1000 = 3\times125\times2 $$

I understand the RHS as $3\times125$ gives number of millimoles which multiplied by n-factor gives milliequivalents. But where does the LHS come from? And what is $w$? In the next line it is given

$$ \text{percentage purity} = (w/40)\times100 $$

where the value of $w$ is taken from the first equation. Would someone please explain this to me?


texts: Hard-hard and soft-soft acid/base interactions

texts:
How does one conclude if a given compound or a complex is a hard or soft acid or base?

What are the factors that contribute to hard-hard, soft-soft, soft-hard, and hard-soft interactions?


texts: Steady-state approach - how to find rate equation for intermediate?

texts:
The reaction mechanism for the formation of $\ce{NO2}$ is:
\begin{align}
\ce{NO + NO &<=>[$k_1$][$k_1'$] N2O2} & &\text{ (slow)} \\[0.2cm]
\ce{N2O2 + O2 &->[$k_2$] NO2 +NO2} & &\text{ (fast)}
\end{align}

What is the equation for rate of change of the intermediate $\ce{N2O2}$?
My solution is as follows:
The rate of formation of intermediate $\ce{N2O2}$ is given by:

\begin{align}
\frac{\mathrm{d}[\ce{N2O2}]}{\mathrm{d}t} = \color{red}{2} k_1[\ce{NO}]^2 - \color{red}{2}k_1'[\ce{N2O2}] - k_2[\ce{N2O2}][\ce{O2}] \approx 0
\end{align}
But the answer in the text book says:
\begin{align}
\frac{\mathrm{d}[\ce{N2O2}]}{\mathrm{d}t} = \color{red}{2} k_1[\ce{NO}]^2 - k_1'[\ce{N2O2}] - k_2[\ce{N2O2}][\ce{O2}] \approx 0
\end{align}

Can not figure out why my answer is wrong.


texts: Selecting parent chain considering substituent (prefix) functional groups

texts:
I am attempting to derive the name of the above compound. Based on the IUPAC rules, I can tell that the carboxylic acid group should be taken as parent i.e suffixed and numbering should start from there. However, since the lengths of both possible choices are equal, there is some ambiguity in my mind as to the choice of parent chain.

Further, what would happen if the -OH were shifted to the carbon adjacent to its current position? Or the amine?


texts: Stability of organophosphorous vs organophosphates?

texts:
In environmental chemistry, most of the organophosphorous compounds we worry about are actually organophosphate compounds.

Is there something about the $\ce{C-P}$ bond that makes it less stable (and thus less persistent in the environment) than a $\ce{C-O-P}$ bond?


texts: Difference between freezing point and melting point

texts: I do not understand why for mixtures freezing point is lower than melting point. Are not the two representing the same equilibrium between solid and liquid which we are approaching from two different sides, so why should the temperature at which this happens be different for the two cases?


texts: Is There a Difference in the Definition of Complete and Stoichiometric Combustion?

texts:
My question has to do with some combustion related definitions. When the term complete combustion is used, is it assumed that the combustion is stoichiometric (reactants combine perfectly), but dissociation does not occur, such that only carbon dioxide and water is the product? If so, does the term stoichiometric combustion mean the same thing except dissociation effects do occur?

Edit: Minor species of combustion as a result of dissociation


texts: Why does tantalum and tungsten not form amalgam?

texts:
User @Poutnik has recently answered a question in which he/she quoted this statement from Wikipedia:

  Almost all metals can form amalgams with mercury, the notable
  exceptions being iron, platinum, tungsten, and tantalum.

I am not sure about the validity of this statement as I found contradicting results regarding iron and platinum amalgams. There has been discussion around iron amalgams on internet giving inconclusive theories about why iron cannot form amalgam (See this reddit post for context) and on further research, I came to know that iron indeed form amalgam albeit unstable (See here). This has also been discussed in an another previous question. User @DrMoishePippik has pointed out that iron can form mercury-based alloys(amalgams?) at specific conditions. So, there is a contradiction regarding formation of iron amalgam.

Some searching also proved that platinum can also form amalgams:

  Platinum Amalgam is obtained by trituration of platinum sponge with
  mercury in a warm mortar; it cannot be obtained by direct union of
  platinum foil and mercury.

  The amalgam has a silvery appearance, and with 12 per cent, of
  platinum is soft and greasy to the touch, but higher percentages of
  platinum increase its stiffness. When heated strongly the mercury is
  volatilised and platinum remains as a grey residue.[...]

I searched the same site for tantalum alloys and gave me following information:

  Sodium, potassium, mercury and silver do not alloy with tantalum even
  at high temperatures; attempts to prepare alloys with arsenic,
  antimony, lead, zinc and tellurium have also failed, but the formation
  of an alloy with silver, copper and tin for making a dental amalgam
  with mercury has recently been claimed.

No information about tungsten amalgam were given on that site. Other sources is giving me irrelevant information although the only other thing I found out is that since they doesn't form amalgams, they can be separated from a mixture of other metals using zinc amalgam.

So, the questions are:

Does tantalum and tungsten really not form amalgams?
If yes, what is the reason? Is it because of the same reason for iron not forming amalgam?
If no, is there any evidence/scientific papers to prove it?

I just saw a comment User @Mithoron has left in the question "Why does mercury not form amalgam with iron?"

  Pt, W and Ta also resist dissolution with Hg

Is this statement true? Can anyone explain the statement?


texts: How can I determine if there will be a reorganization in organic reaction?

texts:
How can I determine if there will be a reorganization of the substrate to stabilize the $\ce{C+}$ in a organic reaction?

Consider an S$_N$1 or E1 organic reaction, when there is a formation of a $\ce{C+}$ during the process. Sometimes, the molecule will reorganize (like one hydrogen will "jump" to another carbon, or a $\ce{CH3}$ will do it) in order to stabilize the $\ce{C+}$. But, sometimes, this doesn't occur. Is there any way of predicting if it will happen or not? Thanks.


texts: Why is there no such substance as p-phthalic anhydride

texts: Its formula is C6H4(CO)2O.  It is an organic molecule that doesn’t have any branching or functional groups on carbon 4 or 1.


texts: How does a mostly non-polar molecule prevent a polar head from being pulled off by other polar molecules?

texts:
Linear-shaped molecules of a solute with a large non-polar section and a small polar head are not soluble in a polar solvent. Why is this? Why don't the attractive forces between a molecule of polar solvent and the small polar head of the solute molecule cause the polar head of the solute molecule to dissociate?

The typical explanation I find on google is that the non-polar section "outweighs" or "is greater than" the polar head, but I'm a little confused as to what that means.


texts: Tetrahedral complex and vibronic coupling or different rule for d-d transition?

texts:
I'm currently preparing a few slides for an upcoming talk in our group. I would like to mention some of the very basics regarding crystal field and ligand field theory as well, though this will not be the main topic of the talk.
I started from allowed transitions and how the (transition) dipole moment operator causes the transition between two states to be allowed or not (from just pointing out the area under an odd and even function and from group theory basics).
Then I'd like to continue to octahedral complexes. But here you've got two problems, one is the d-d transition that is forbidden and the other one is the Laporte forbidden transititon. When I need to compare this to the next slide with tetrahedral ligand fields I can always say that the Laporte rule doesn't work here since there is no inversion center.
So how is the Laporte rule still achieved for octahedral complexes? Due to something we call vibronic coupling. I always assumed this meant that a vibration, prior to the exitation deforms the octahedron to something that has less symmetry (which is probably happening, too) until I recently heard about transforming your set of p-orbital originating $T_\mathrm{1u}$ along the vibrational mode T1u that is also the dipole moment operator in this case, as x,y,z transforms as $T_\mathrm{1u}$ in this point group. Transforming $T_\mathrm{1u}$ along $T_\mathrm{1u}$ in an octahedral complex gives you, among others also a $T_\mathrm{2g}$, so the $T_\mathrm{2g}$ for the transition can also be described in terms of p-Orbital and thus you get p-orbital contribution. (Please correct me if I've understood anything wrong here).
Now this is a good explanation, what it doesn't explain however is how actual d-d transitions are allowed now? This means there is either another thing happening here or that there is also a vibronic coupling for the tetrahedral case.
Now, before I read into those group theory explanations I assumed that the d-d transitions happens because we are not talking about actual d-orbitals but we are talking about electrons in bonds. As the $T_\mathrm{2g}$ requires a π-type bonding and the $E_\mathrm{g}$ uses σ-bonding the actual transition is from a π-orbital into a σ-orbital, so p-s or if you take both sides pd-ps.
The other alternative would be that also the tetrahedral complex uses vibronic coupling. I can't find much on this though. There are calculations in combination with Jahn-Teller effects but no clear answer as with the octahedral case.
Hence my question: When talking about d-d forbidden transitions without taking the Laporte rule for odd even parity into account, is the often cited mixing of d-states with p- and s-states from something coming from the bonding situation or is the prohibition lifted due to the same vibronic coupling mechanism as used for partiy forbidden transitions?


texts: How to determine the proton concentration in the following solution in mol/L?

texts:
A $\pu{0.8L}$ solution contains $\pu{0.60 g }\ce{ NaOH}$ in water. Then the above question follows.

It's been a long time that I made some chemistry exercises. Now I'm stuck with a couple of hesitations.

I know one needs to calculate the number of protons of the molecule sodium hydroxide. But do you need to take water into account or not? I'm thinking not but then the question asks for the solution. So I probably should do that which gets me to $\pu{29 g mol-1}$. Otherwise it is $\pu{20 g mol-1}$.

So that I would divide by $\pu{0.60g}$ which gives me for the first one $\pu{48 mol}$ and the second one $\pu{33 mol}$. Then I'd divide it by $\pu{8.0L}$.

I probably should have a larger answer than what I've done so it is not correct but I don't know exactly how I should work this out.

I'd appreciate a hint.


texts: Noyori hydrogenation and the Curtin–Hammett principle

texts:
My question is relating to how the Curtin–Hammett principle applies to homogeneous hydrogenation using chiral ligands.

Figure 0: An example of a quadrant diagram used as a mnemonic to predict the facial selectivity of reduction (in this case of a 3-hydroxyketone)

We commonly draw mnemonics (i.e. quadrant diagrams) to 'predict' the most likely products, however this prediction surely works on the assumption that the energy of the intermediate complexes is responsible for the overall outcome of the reaction since in using these mnemonics we're assuming that steric clashes are what determines the 'lowest energy' binding mode (which is supposedly not the case in the example in figure 1).

Does the mnemonic take into account this kinetic preference, or are we only able to predict the product for hydrogenations not taking place via Curtin–Hammett kinetics? (and if so, can one generalise if the Curtin–Hammett principle is applicable for a given reduction? I seem to recall reading something along the lines of Ru(II) and Ru(I) systems operating by different kinetics, for example).

Ruthenium-BINAP complexes (and related complexes using modified ligand systems) are commonly employed for asymmetric homogeneous hydrogenation/reduction of a wide range of substrates (the general caveat is the need for 2 point binding in order to get suitable control).

An example is below in figure 1 using a diphosphine ligand to selectively reduce the enamine, which introduces a new stereocentre and essentially furnishes an amino acid derivative.

Figure 1: Example of a Ru-catalysed asymmetric hydrogenation (from Organotransition metal chemistry, from bonding to catalysis, Hartwig).

When thinking about these reactions, we often use 'quadrant diagrams' and other mnemonics in order to predict how the substrate will bind (based on minimising steric interactions), but essentially binding of the substrate to the complex yields two diastereomeric transition states which are able to interconvert (figure 2).

Figure 2: Proposed 'mechanism' of a Ru-catalysed asymmetric hydrogenation  (from Organotransition metal chemistry, from bonding to catalysis, Hartwig).

What is unusual in this reaction is that the energy (and hence population) of the diastereomeric intermediates does not have any influence on the ratio of products formed, with the higher energy/less populated intermediate being the one going on to form the product. This is an example of Curtin–Hammett kinetics, with the oxidative addition step, in this case, being the thing that determines which product forms.

Figure 3: Reaction profile (from Organotransition metal chemistry, from bonding to catalysis, Hartwig).


texts: How to calculate the probability of finding an electron in a box between 0.25L and 0.75L?

texts:
If the wavefunction of the electron in a box of length $L$ is $$\psi{(x)}=\sqrt{\frac{2}{L}}\cdot\sin{\frac{n\pi x}{L}}$$
What would be the probability of finding the electron between $0.25L$ and $0.75L$?.

From postulate 1 of quantum mechanics I know that $$1=\int_{0}^{L}{\psi(x) \psi^{*}(x)\,\mathrm{d}x}.$$

Trying out a similar reasoning leads me to think that the required probability is the integral $$ \int_{0.25L}^{0.75L}{\psi(x) \psi^{*}(x)\,\mathrm{d}x}$$ which gives the answer as $0.5$. But the book gives the answer as $0.82$.

What is the problem with my method and can anyone explain me why the answer is $0.82$?


texts:
How can I tell if a molecule is purely polar or amphipathic?
For example, fatty acids are amphipathic because they have a polar carboxyl group and a non polar chain of hydrocarbons. However, sometimes there are molecules that have hydrocarbon chains and side polar groups but are categorized as polar.
What is it that I should look for?
Thank you so much!


texts: What is this glassware for a distillation apparatus called?

texts:
I'm messing around with building a solar distillation apparatus, and one of the parts I think I need looks kind of like the following, except I have no idea what it is called (and thus can't look it up to see if that site even sells them).

So, can anyone tell me what this thing is commonly called?


texts: Does titration usually always involve neutralization?

texts: I've been doing titration exercises that involve figuring out the molarity of an unknown solution when you know the molarity of another (so like knowing the molarity of solution A but figuring out the molarity of solution B), and it usually always involves neutralization. Is it common that titration exercises involve neutralization?


texts: How to control current and voltage in electrolysis

texts: I am doing an experiment that aims to determine if the rate of electroplating changes with the temperature. I am using a copper rod, a solution of copper(II) ions and a neutral rod to be coated. I also want to keep every other variable the same, which means the voltage across the rods, the concentration of the solution and the current that goes through the circuit. But the times my professor tried to demonstrate electrolysis, either the current or the voltage was always dropping. How do I prevent this from happening? How can I ensure that the voltage and current remain unchanged for the entire duration of a trial?


texts: Why is a titration necessary? Why can't we just compare the moles of the acid and base?

texts:
For the following question:

$\mathrm{1g}$ of $\ce{Mg(OH)2}$  is completely dissolved in $\mathrm{25}$ mL of $\mathrm{0.5}$ M $\ce{HCl}$. This solution is then titrated with $\mathrm{0.1}$ M $\ce{NaOH}$, and it takes $\mathrm{40}$ mL of $\ce{NaOH}$ to reach the end point. What volume of $\mathrm{0.5}$ M $\ce{H2SO4}$ would neutralise 1g of $\ce{Mg(OH)2}$ ?

This is solved by the following steps:

moles=concentration*volume=$\mathrm{0.5}$ M * $\mathrm{25 mL}$ $\ce{HCl}$=$\mathrm{12.5}$ mmol $\ce{HCl}$ which is equivalent to $\mathrm{12.5}$ mmol  $\ce{H+}$.
moles=concentration*volume=$\mathrm{0.1}$ M * $\mathrm{40 mL}$ $\ce{NaOH}$=$\mathrm{4}$ mmol $\ce{HCl}$ which is equivalent to $\mathrm{4}$ mmol  $\ce{OH-}$.
Difference = $\mathrm{12.5-4=8.5 }$ mmol of $\ce{H+}$. That is, $\mathrm{8.5}$ mmol of $\ce{H+}$ was used in the reaction with the $\ce{Mg(OH)2}$.
Finding out how much $\mathrm{0.5}$ M $\ce{H2SO4}$ is required to give $\mathrm{8.5}$ mmol of $\ce{H+}$ :  $\mathrm{1}$ mole of $\ce{H2SO4}$ gives $\mathrm{2}$ mole of $\ce{H+}$, so we need $\mathrm{8.5/2=4.25}$ moles of $\ce{H2SO4}$. Concentration=moles/volume. Volume = moles/concentration=$\mathrm{4.25}$ mmol/$\mathrm{0.5}$ M=8.5 ml $\ce{H2SO4}$ required.

Why are all these steps necessary? Can't we directly compare the number of moles of $\ce{Mg(OH)2}$ and $\ce{H2SO4}$? I.e. as follows:

Molar mass of $\ce{Mg(OH)2}$=$\mathrm{24.3+16*2=56.3}$
moles=mass/molar mass=1g of $\ce{Mg(OH)2}$/$\mathrm{56.3}$=$\mathrm{0.018}$ moles of $\ce{Mg(OH)2}$, which is equivalent to $\mathrm{0.018*2=0.036}$ or $\mathrm{36}$ mmol of $\ce{OH-}$.
So we need $\mathrm{36}$ mmol of $\ce{H+}$ to neutralise $\mathrm{36}$ mmol of $\ce{OH-}$. $\mathrm{1}$ mol of $\ce{H2SO4}$ contains  $\mathrm{2}$ mol of $\ce{H+}$. So we need $\mathrm{36/2=18}$ mmol of $\ce{H2SO4}$.
Concentration = moles/volume = $\mathrm{0.5}$ M = $\mathrm{18}$ mmol/Volume. So Volume = $\mathrm{18/0.5=36}$ mL of  $\ce{H2SO4}$.

My second attempt yields the wrong answer. So why can't the problem be solved by comparing the number of moles of hydrogen ions and hydroxide ions? Why is the titration with other molecules required to solve this problem?

Note: I have attempted to summarise the question here. But if you prefer to read it in its original form:


texts: What determines solubility (or miscibility) in organic solvents?

texts:
I'm actually quite surprised that this isn't really mentioned anywhere on the internet (or I'm just bad at searching)! Solubility in water is known to be directly related by multiple factors, and for organic molecules it's usually ability to form hydrogen bonds, polarity, bulk etc. I would imagine this trend would continue for most of the smaller alcohols (methanol, ethanol, isopropanol etc.) to some extent. However, I can't find even a brief mention on how solubility in common solvents is determined.
Let me share my (admittedly very elementary) logic:
For a solvent like cyclohexane, which is non-polar, I imagine other non-polar solutes would be able to dissolve. However, if the non-polar compound is solid, it will require heating to break the van der Waals forces first. I assume little to no enthalpy change occurs in this process. Other more polar solutes would prefer to continue associating with themselves, and therefore not dissolve.
For a solvent like diethyl ether, it gets a tad more complicated. The oxygen atom on the ether is a hydrogen bond acceptor, and the molecule is polar. So, I imagine that non-polar solutes are poorly soluble. The same should go for compounds like amines, alcohols and carboxylic acids because they rather hydrogen bond with themselves. However, for meekly polar compounds with functional groups like aldehydes, ketones and halogenoalkanes, I imagine it depends on its polarity? It's polarity should be near that of the solvent; if it's more polar it will rather be with itself, if it's less polar the solvent would rather be with itself. So for example, if I mix ethyl chloride with diethyl ether, will they be miscible?
If anyone can support or debunk my logic, it will be greatly appreciated.


texts: Calculating surface area from BET results

texts:
I have been trying to work out the workings of the BET method and I have come to a standstill.

The surface area of a sample is given by

$$
S_{\text{BET}} = \frac{\nu_{\text{m}}Ns}{V}
$$

where $\nu_{\text{m}}$ is the amount in the monolayer (given in $\mathrm{cm^3/g}$), $N$ is Avogadro's constant, $s$ is the adsorption cross-section of the adsorbate ($\pu {0.162 nm^3}$ for $\ce{N2}$) and $V$ is the molar volume of the gas ($\pu {22.4 L/mol}$).

If I run this sample through a commercial software that comes with the adsorption equipment, for a given mesoporous sample, it gives me $\nu_{\text{m}} = 209.6160~\mathrm{cm^3/g}$, and a final result of $S_{\text{BET}} = 912.5 ~\mathrm{m^2/g}$.

If I try to calculate this myself (converting everything into SI units), however, I get that same result, but divided by a factor of $1\times 10^9$.

I think I'm making some stupid unit conversion mistake, but I can't see it.


texts:
I would like to have an in-depth understanding of Li-ion batteries functionality, at atomic level. Can anyone help me to understand it? I have included some known background to support my questions.

For a fully charged battery:

The theory says that all (let's assume an ideal case) the Li-ions are in the anode, right? But are they really ions at this point or simply neutral atoms where the numbers of electrons is equal to the number of protons? In other words, are there ions or atoms in the anode? See figure below for a single Li-"ion":

Do we say that the electrical energy is stored in the electrons or is this a false statement, considering that batteries store chemical energy by definition? If we say that it is only chemical energy, how does one make the conversion between electrical energy and chemical energy? Is it stored in bonds?
Is the anode "more energetic" than the cathode in this case, considering that there are more electrons in the anode?

When discharging:

The theory says that the load "steals" the electrons which travel through the load and then "land" back into the cathode. Is the electrical energy from the electrons used by the load and then they go back to the cathode "empty"? (According to the definition of internal energy, the work is done by kinetic energy due to movement of electrons or molecules).

Fully discharged battery

Now we are in the situation where "all" the ions are back to the cathode. At this point, are there less electrons in the cathode or why is the battery discharged? Popularly, the battery is "out of fuel", but how do we actually translate this into energetic phenomena?

I appreciate any type of help, recommendation or mathematical explanation.

And please don't tell me that I need to go and read the basics of thermodynamics and stuff, because I did that, but none of the books/pages that I found describe these things at an atomic level. However, any recommendation of a book/page that does that will be highly appreciated!

Thank you very much in advance!

Paul


texts: What is the correct expression of pressure-volume work?

texts:
My book defines work in pressure-volume work as:
$$\mathrm{d}w = - P_\mathrm{ext} \mathrm{d}V$$
However before doing so it mentioned the piston to be massless.
In physics, work is defined as
$$\mathrm{d}w = P_\mathrm{in} \mathrm{d}V$$

What is the correct definition of pressure-volume work in chemistry?
Does the definition of work, $$-P_\mathrm{ext} dV$$ change if the piston was not massless in chemistry?

P.S. My question was mainly pointed towards the mathematical expression of work in Chemistry,that is, 'What is the most general work expression in Chemistry in relation with the First Law'.
Some of the users have been suggesting me to check out answers on sign convention of work. I do appreciate it but my question is different and is perhaps best interpreted in @Chet Miller answer.


texts: Why is a CO single bond stronger than a NO single bond?

texts:
Why is a CO sigma bond stronger than a NO sigma bond? I would think that since nitrogen and oxygen are of similar size and have similar atomic orbitals (because they are adjacent in the period), their MO "overlap" would be superior.
Does it have something to do with their similar electronegativities "fighting" over the electrons?


texts: How are bubbles formed when heating water?

texts:
My thinking is that bubbles are formed due to the dissolved gases in water. Consequently, upon heating, bubbles are formed and do not remain intact with water molecules, and thus the bubbles are formed. And since the bubbles are less dense than water, they goes up and pop due to air pressure. Water vapor is then formed in the above air. Is this all correct?

I have researched this topic and it's very difficult for me to understand. Please explain it as if you're explaining it to someone who knows very little about chemistry.


texts: The "hazardousness" of artificially made sweteeners

texts:
In school I learned of the "possible hazardity of artificial sweeteners." But that was some time ago, now. I think that science should have caught up by now.
My question is as follows.

Which chemical properties in artifical sweeteners could be potentially cancerogenous?

(This is to say, if there exists cancerogenous properties in artificially made sweeteners from the start).
Please enlighten me.
Examples of sweeteners:

Fig 1 Acesulfame Potassium

Fig 2 Aspartame


texts:
I'm trying to help a friend of mine with this chemistry question:

  What is the pH of a $1.0M$ solution of glycine?

They're given that the pKa of COOH is $2.4$ and the pKa of the amine group is 9.6. The solution they were given says the pH is just $\frac{2.4+9.6}{2} = 6.1$, but I don't see any reason why this should be true especially since this answer initially appears independent of the given concentration of glycine.

Now if I try to solve this the long way: If I initially just have a solution of glycine, I believe it would function like a weak acid, and hence the equation is:

$$Ka = \frac{[H^+][A-]}{[HA]}$$

or

$$10^{-9.6} = \frac{x^2}{1-x} \approx x^2$$

Thus pH = $4.8$

At the very least, I found this document: https://www.ch.ntu.edu.tw/~ccchan/course/genchem2003/Notes/final_ans.pdf

Which showed that the pH of a $0.05 M$ solution of glycine has a pH of $5.54$, so with a much higher concentration of glycine functioning like a weak acid, my pH should be less than $5.54$ (and hence definitely less than the $6.1$ the professor put as his solution). Am I missing something?


texts:
I can't recognize the Raman spectrum of this plastic.

It's not in the common plastics raman spectrum.

It is plastic adaptor for connecting sediment filters. Anyone got idea or recognize what kind of plastic is it made of? I'm studying the high temperature resistance of it. I bought a hot water sediment filter and using it as adaptor.


texts: Why do aromatic hydrogen atoms have a higher chemical shift value compared to aliphatic hydrogen atoms?

texts:
In Nuclear magnetic resonance (H-NMR) spectroscopy, the chemical shift of aliphatic hydrogen atoms are very much closer to the 1.0 ppm than that of aromatic hydrogen atoms.

Aromatic hydrogen atoms have a chemical shift value of about 7.0-9.0 ppm whereas the chemical shift value of aliphatic hydrogen atoms ranges between 2.0-3.5 ppm.

Why is this so?


texts:
To complete homework I am working on, I need help finding the density of a penny. I'm not given the mass or the volume. All I know about this penny is it's zinc coated in copper, and I am given the percentage of copper in the penny: 3.0% (by mass). We are to use these values for the density of copper and zinc:

Copper = 8.93, Zinc = 7.14

My friends did this:

$$\mathrm{8.98 \times 0.03 + 7.14 \times 0.97 = average~density~of~a~penny}$$

I told them "I think you're wrong, you can only calculate the average density of something if you use the volume", but I couldn't explain it any better.

Here's what I did:

Let $M$ be the mass of this penny in grams.

$$\frac{0.03M~\mathrm{g~mL^{-1}}}{8.98~\mathrm{g}} = \frac{0.03}{8.98}M~\mathrm{ml}$$

$$\frac{0.97M~\mathrm{g~mL^{-1}}}{7.14~\mathrm{g}} = \frac{0.973}{7.14}M~\mathrm{ml}$$

Adding them together we get $7.1952M$.

I'm not sure what this number represents but we can use it to find the ratios of volume.

$$\frac{\frac{0.03}{8.98 M}}{7.1952 M} = 0.0374$$ $$\frac{\frac{0.97}{7.14 M}}{7.1952 M} = 0.963$$

Using these numbers, we do what my friends did:

$$8.98 \times 0.0374 + 7.14 \times 0.963 = \mathrm{average~density~of~a~penny}$$

Am I correct?

If I am, is there a formula or any other simpler way to do this.

This is my first question on this site, so let me know if I did anything wrong.


texts: Titration curve of a diprotic acid with a strong base titrant

texts: I have wonders regarding the titration curve of the titration of sulphuric acid, or any diprotic acid, with a strong base. I am aware of the fact that a diprotic acid is protolysed in two steps but, how does this affect the titration curve?


texts: Does adding water to a reaction mixture shift equilibrium?

texts:
Just like decreasing volume in a gaseous reversible reaction shifts the position of equilibrium towards the side that produces more moles (increasing pressure), shouldn't adding water shift equilibrium to side that produces more moles in a liquid equilibrium mixture (increasing concentration)?

On research, I've seen an explanation that it does not because the concentration of both reactants and products decrease evenly, but I don't understand this. The side with more moles should have a greater decrease in concentration because the concentration is proportional to the number of moles. Also, by the same argument, decreasing volume in a gaseous reaction should not shift equilibrium.

My guess is that adding water does affect equilibrium for a reaction with different number of moles on each side. Because the equilibrium constant is affected. Is this right?


texts: NCl₃ + H₂O → NH₃ + HOCl , the resulting solution is acidic, basic or neutral?

texts:
When $\ce{NCl3}$ is dissolved in water, $\ce{NH3}$ and $\ce{HOCl}$ is formed.

Can you please explain me whether formed solution is acid or basic or neutral? thank you!


texts: How can I calculate the concentration of nanoparticles in water solution?

texts:
I have synthesized gold-silver bimetallic nanoparticles in water media by following this article.
How can I calculate the concentration of my nanoparticles solution?


texts: IUPAC: Would I prioritize low numbering to highest-priority group, OR try to assign lowest numbers overall?

texts:
I made up a pretty silly example of a molecule here, but I hope it illustrates my point. It is a dial, but which is the scientifically-preferred order of numbering: left to right, or vice versa?
As you can see in this example, going from left to right gives the -OH group — highest priority after the aldehydes — the lowest possible number (19 versus 21, if we started from the right). However, numbering from right to left gives us the lowest numbers cross the board, but we’re not prioritizing the lowest possible number to our -OH, and instead give it to our lowly methyl group.
I have a feeling it’s right to left, because 4- and 21- is so much more reasonable than 19- and 36-. Would you mind sharing any thoughts, please?


texts: Why does there need to be a planar intermediate in 2,2'-dibromobiphenyl when one of the phenyl groups rotates?

texts:
I was in class and my professor brought up the example of 2,2'-dibromobiphenyl:

In her example, one of the bromines was actually pointing into the page and the two phenyl groups were not actually on the same plane of the page. Let's call the phenyl with the bromine that points into the page group 1 and the one that is on the page group 2. She then said that in order for the group 1 phenyl to point out from the page (a conformer) there will be a planar intermediate where the bromines are very close to each other during the rotation (just like in the picture), and this will require a large amount of energy (20 kcal/mol) which will again drop off once the group 1 rotates till it's pointing out of the plane. My question is, why doesn't it just rotate the other way where the bromines will not come into close contact and there will not be a planar intermediate? Am I overthinking this?


texts: Regarding the mechanism for biological activity of tyramine, amphetamine and ephedrine

texts:
Graham Patrick explains the mechanism for the activity of tyramine, amphetamine and ephedrine in his book Introduction to Medicinal Chemistry as follows:

  Some amines such as tyramine , amphetamine , and ephedrine closely resemble noradrenaline in structure and are transported into the nerve cell by noradrenaline’s transport proteins.
  Once in the cell, they are taken up into the vesicles. Because these
  amines are competing with noradrenaline for transport proteins,
  noradrenaline is more slowly reabsorbed into the nerve cells.
  Moreover, as the foreign amines are transported into the nerve cell,
  noradrenaline is transported out by those same transport proteins.
  Both of these facts mean that more noradrenaline is available to
  interact with its receptors. Therefore, amphetamines and similar
  amines have an indirect agonist effect on the adrenergic system.

I have two question concerning this explanation:

When these foreign amines have been taken up into the vesicles how do they proceed? Do they re-enter the synaptic cleft by exocytosis, so that they can re-exercise their negative influence on noradrenaline re-uptake? How are they eventually cleared from the synaptic area?
Why do the noradrenaline re-uptake proteins transport noradrenaline out of the axonal terminal under the influence of these foreign amines?


texts: why are Ca(OH)₂ and Al(OH)₃ less soluble than Na(OH) in water

texts:
Even though it has more $\ce{OH}$ groups and still it is very weak in terms of dissolving?

please clarify to me in terms of polar and non polar solubility, how to determine whether a compound is soluble or not in water.


texts:
For this we weigh $\pu{1.015 g}$ of linseed oil which is dissolved in alcohol. 3 drops of phenolphthalein (pH indicator) are added and a solution of potassium hydroxide of concentration $C = \pu{9.5e-3 mol L-1}$ is poured. The indicator turns to $V = \pu{7.4 mL}$

I calculate like that:
$$n_\mathrm{acid} = n_\mathrm{OH} = C_\ce{OH}\cdot V_\ce{OH} = 9.5\cdot 10^{-3} \cdot 7.4\cdot 10^{-3} = \pu{1.444e-4 mol}$$

$$\pu{1.444e-4 mol} → \pu{1.015 g}$$
$$\pu{1.423e-4 mol} ← \pu{1 g}$$
$$\implies I_a = m_\ce{KOH} = 1.423\cdot 10^{-4} \cdot 56 = \pu{7.967 mg}$$

But the teacher responds with $I_a = 3.8$. How to solve?


texts: Product of the reaction between hexane‐2,5‐dione and ammonium carbonate

texts:
Which of the following statement is INCORRECT?
(A) The product X has a five membered ring.
(B) The product X is aromatic.
(C) The degree of unsaturation of the product X is 3.
(D) The product X has a six membered ring.

Ammonium carbonate will probably lose a proton and one of the carbonyls may be protonated. But from here onwards I can't find any leads. Does the lone pair of other oxygen atom plays a role?
Usually the heat provided may lead to a cyclic structure, but I am not sure.


texts: Unit of the equilibrium constant: contradiction of Bridgman's theorem?

texts:
The following equation is standard in thermodynamics:

$$
\Delta G^\circ=-RT\log(K)
$$

where $K$ is the equilibrium constant.  In dimensional analysis, Bridgman's theorem tells us that the argument of a transcendental function (like $\log$) must always be dimensionless.  But $K$ may have dimensions (depending on the particular equilibrium).  Why is this OK?

Note: working out dimensions explicitly gives:

\begin{align}
[R]&=EN^{-1}\Theta^{-1}\\
[T]&=\Theta\\
[\Delta G^\circ]&=EN^{-1}
\end{align}

where $\Theta$ is the dimensions of temperature, $N$ is the dimensions of number and $E$ = dimensions of energy = $MLT^{-2}$.  From these, we see that the quantity $\log(K)$ ought to be dimensionless, implying that $K$ should be dimensionless as well.  But it isn't always.

Furthermore, suppose $K$ has dimensions $NL^{-3}$ (for an equilibrium of the form $A+B\leftrightarrow AB$, say).  Suppose now that we scale the units for number by a factor $a$.  Then we get new values for $K,R,\Delta G^\circ$, given by:

\begin{align}
\hat K&=K/a\\
\hat R&=aR\\
\hat{\Delta G^\circ}&=a\Delta G^\circ
\end{align}

From our original equation:

\begin{align}
\Delta G^\circ&=-RT\log(K)\\
a\Delta G^\circ&=-aRT\log(K)\\
\hat{\Delta G^\circ}&=-\hat RT\log(a\hat K)\\
\hat{\Delta G^\circ}&=-\hat RT\log(\hat K)-\hat RT\log(a)
\end{align}

So the new quantities do not satisfy the old equation.  Rather, they satisfy the old equation, but with a constant factor of $-\hat RT\log(a)$ added on.  What is going on here?


texts:
I am trying to determine what the derived partial pressure would be for CO2 in the global atmosphere from historical inconstant temperatures and CO2 concentrations of the global atmosphere:

Is it possible to do this?  If so, how?


texts: Are there stronger oxidizing agents than fluorine gas?

texts:
Are there stronger oxidizing agents than fluorine gas, so it could oxidize fluoride to fluorine?

Also, in case of oxygen, fluorine gas can oxidize oxygen gas to the exotic dioxygenyl ion. Can anything oxidize fluorine gas to $\ce{F+}$ ion?


texts: At my school, my teacher tell us to extract sodium from normal salt ($\ce{NaCl}$) but without using electrolysis of molten sodium chloride. So is there a way to do that?


texts: Compound with pressure sensitive melting point at moderate temperature and pressure

texts:
I'm in need for a compound with ideally all of the following properties:

A melting point of 5 °C or less at 1 atmosphere (or slightly lower pressure)
A melting point of 12 °C or more at less than 20 atmospheres.
A significant enthalpy of fusion

(long term stability, a boiling point > 50 °C, and less than a 3 digit \$ cost per kg would also be nice).
Seeking such a compound, a melting point range this wide appears to be unusual at such small pressure differences. So far, the best I have is cyclohexane, but the melting point is a bit too high at 6.5 °C at normal pressure, and it needs over 100 atmospheres before the melting point gets above 12 °C, which is impractical.


texts: Good software/module in python to determine nuclear attraction integral in Slater type orbital basis sets

texts:
I am trying to solve a Hamiltonian of one electron and 10 stationary nuclear centers. here, the electron is treated quantum mechanically and nuclear centers are treated classically objects. The Hamilton is as follows,
$$H=-\frac{1}{2}\nabla^{2}-\sum_{i=1}^{10}\frac{1}{|\vec{r}-\vec{R_{i}}|}$$. Charge on each nuclear center is one. For the given set of locations of nuclear centers I tried to solve the Hamiltonian using MO theory by mixing  $1s$, $2px$,$2py$,$2pz$ of all the 10 centers making a total basis of 40 with arbitrary coefficients to be determined.

Now I have used STO -3G to compute the one electron attraction integral by using the existing algorithm and wrote my own code. My question is whether there any software package to compute all the integrals (one electron integral) using slater type orbital in python. Because STO-3G is not an accurate representation of slater type orbital. Do I need to go for FORTRAN for slater type orbital basis set calculations?

Also is there any reference books or papers where I can find the algorithm for slater type orbitals one-electron integrals?


texts: Why is the valency of the Calcium (Ca) Bohr model, set to 2 electrons, instead of 1 electron for stability?


texts:
So, I was wondering, when overlap of orbitals takes place, among s–s, s–p, p–p which type of overlapping is stronger?

Because in s–s more volume is being used in overlap, but the electron density is less; whereas in p–p electron density is more, but overlap is less; or s–p because it has partially both the effects?


texts: How can I find the stoichiometry of a reaction from the volumes of the reactants and products given?

texts:
I have volume $V$ of gas $\ce{A}$ and an equal volume $V$ of gas $\ce{B}$ at room temperature and pressure. I mix, ignite, and find I have a gas (mixture of $\ce{A}$ and product $\ce{C}$) at room pressure, $325~ \mathrm{^\circ C}$, and total volume $3V$. What was the stoichiometry of the reaction?
  \begin{align}
 \text{a)}&&\ce{2A + B &-> C}\\
 \text{b)}&&\ce{A + 2B &-> 2C}\\
 \text{c)}&&\ce{2A + B &-> 2C}\\
 \text{d)}&&\ce{A – 2B &-> C}\\
\end{align}

The answer is $\text{b)}$ but I can't seem to get the logic.
$V$ vol of $\ce{A}$ plus $V$ vol of $\ce{B}$ reacts to give $2V$ vol of $\ce{C}$. How did we find stoichiometry from this? What about some unreacted $\ce{A}$ ?


texts: Acid-Base Titration, why does for a weak acid indicator, [HA] = [A-]

texts:
I am reading about indicators and their behaviour as weak acids.

I know that the end-point is when exactly all of the H+ ions from an acid have neutralised the OH- ions of the base.

The book later says

  At the end point of a titration, the indicator contains equal concentrations of HA and A- and the colour will be inbetween the two extreme colours e.g. for methyl orange, the colour at its end point is orange.

It continues to say

  For an indicator HA ⇌ $H^+$ + $A^-$
  At the end-point, [HA] = [$A^-$] and $$K_a = \frac{[H^+][A^-]}{[HA]} = [H^+]$$

I am confused why this is true. why is the expression [HA] = [$A^-$] valid?


texts: Possibility of R-Si-OCH3 reacting with alkanol group in polysaccharides

texts:
For example, the aminosilanizing agent 3-aminopropyltriethoxysilane (APTES)

It has been frequently used for silanization of silica or glasses for various purposes. The surface funcation group of silica contain Si-OH which will react with APTES under certain conditions:

Both Si and C are group 4 elements
R-C-OH where the C-OH is less polar than Si-OH bond
Take glucose as the example, it contains 5 external C-OH bonds. So is it possible for APTES to react with glucose? If yes, what condition should it be?


texts: What assumptions underlie Hess' law and and its analogues?

texts:
Let me first briefly describe the laws as I understand them.

Hess' law states that the enthalpy of reaction can be obtained by taking the sum of the enthalpies of formation for the compounds involved in the reaction, weighted by their stoichiometric coefficient. This is often shortened to $\Delta_\mathrm{r} H = \sum \Delta_\mathrm{fm} H_\mathrm{products} - \sum \Delta_\mathrm{fm} H_\mathrm{reactants}$. A similar law exists for entropy. To get the enthalpy of a compound, one usually looks up the tabulated standard state enthalpy, and then integrates the compound's heat capacity $C_p$ to get the enthalpy at the temperature of interest. A similar procedure is used for computing the entropy. Although I have not seen it done, I guess there is nothing in the way of using such laws in a partial reaction (i.e. equilibrium): by summing the enthalpies of the various compounds at equilibrium and subtracting the enthalpies of the compounds you started with, you should get the "enthalpy of equilibrium".

What assumptions underlie these laws? For Hess' law, I would think "enthalpy of mixing is zero" is one of them, but I've yet to see it stated.

An admittedly wage bonus question: I am here talking about $H$ and $S$, but what about similar laws (if they exist) for other potentials (Gibbs energy $G$, Helmholtz energy $A$ and internal energy $U$)?


texts: Predicting product of a Hofmann elimination with a cyclic amine

texts:
What is the final product of this reaction?

Here's what I have:

Does this look correct? I'm concerned because I'm used to seeing the nitrogen removed from the product (in the cases of primary amines).


texts:
Specifically, I'm curious if there are any programs which come close to Gaussian in breadth but also take advantage of things such as GPU processing.

There's a page on wikipedia that goes through several options but I'd like to get feedback from actual users.


texts: Disproportionation of 2 KO₂ + 2 H₂O → 2 KOH + H₂O₂ + O₂

texts:
How is the following reaction a disproportionation reaction?

$$\ce{2 K\overset{-1/2}{O}_2 + 2 H2\overset{-2}{O} ->2 KOH + H2\overset{-1}{O}_2 + \overset{0}{O}_2}$$

In this, the OS are $-1/2$, $-2$, $-1$, $0$, respectively, but in disproportionation  the element$ O $both oxidizes and reduces. How do we know that this happens here? $\ce{KOH}$ may get oxidized, and $\ce{H2O}$ get reduced. How do we know the same compound has undergone both?


texts: Why does RCN attack the benzene ring in Hoesch Reaction?

texts:
In the Hoesch reaction, an alkyl cyanide reacts with a polyhydric benzene ring, and forms an imine salt by attacking the activated benzene ring. Most acid derivatives (and even alkyl cyanide itself with phenol) results in attack at the alcohol's oxygen, which is more nucleophilic than the benzene ring. In this case however, the major product doesn't form by attack on the alcohol.

Where lies the difference? If it were in the fact that benzene is more activated because of the many alcohol groups in the polyhydric compound, wouldn't it mean that even another acid derivative, like acid chloride, would react at the benzene instead and not at the O (thus carrying out a Friedel-Crafts acylation)?


texts: Book Recommendations for Inorganic Chemistry Mechanisms

texts:
I am looking for a book which has details or basics to reaction mechanisms for inorganic chemistry for highschool level(preferably) or maybe undergrad level.
Basically I am looking for a book which can help teach me inorganic chemistry in such a way which decreases the amount of rote learning and memorising , but gives concepts/explanation for things. Like in organic chemistry we have mechanisms , and different things, something like that.
Is there any such book out there ?? Please help !!
I was reading this link which has basic resources, but none meet such criteria , please help
Edit: Regarding the question being duplicate: The posts there talk about in general getting started with chemistry. What i am looking for is something more specific which is not covered there in any detail. The book on arrow pushing mostly goes over the reactions of organic chemistry which involve inorganic reagants.
I am looking for something that will teach me inorganic ,not just memorise it.
Eg ,Reasons for the different trends shown by the elements, Reaction Mechanisms , etc ..
PS:For any of my Indian Friends, I am looking for a book helpful for JEE Advanced


texts:
On the festival of Diwali, Indians exchange sweets and share their love. I did just that this very morning, but things don't always go the right way. I dropped a box of sweets and the sugary syrup spread all over the floor. Now while cleaning up the floor, a question popped up in my mind: Why is sugar syrup is so sticky? Is there any chemical phenomenon responsible for its stickiness?

Since I'm a high school student and not a chemist, I can't seem to think of any possible explanation. I shall be thankful if someone could direct me the right way here.


texts: Trends in the covalency of bonding across the transition metals

texts:
I am under the impression that the covalent character in the bonding of transition metal compounds increases across a group; in fact I think this is why they're called transition metals (a transition from purely ionic compound shown by the pre transition metals to covalent bonding in the non-metals). I think d orbital splitting and ligand field effects become more significant across the series (please confirm or deny) which would support this assertion. Is the reason for this that the d orbitals decrease in energy across the series, as a result of increasing effective nuclear charge, which results in a better energy match with ligand orbitals?

However, could one not argue that the covalency should decrease across the series as the d orbitals become more contracted and orbital overlap with ligands is less efficient. One trend that would seem to support this view is that the metal carbon bonds in organometallic complexes with alkyl and aryl ligands tend to decrease in strength across the series.


texts: How concentrated does sulfuric acid need to be for nitric acid synthesis (H2SO4 + nitrate salt distillation)?

texts:
So I have a home lab setup and recently found myself in need of some nitric acid. I could just buy some, but I thought it would be a useful exercise to make my own. I have plenty of nitrate salts around, as well as plenty of unused ~30% sulfuric acid (battery acid refills, fresh out of the box so there's no lead etc in it).
I know distillation of a mixture of a nitrate salt (ex. NaNO3) in sulfuric acid should yield nitric acid, but all the protocols I've found call for concentrated H2SO4. Would ~30% work? I know "concentrated" sulfuric acid usually means >90% if not fuming, but as long as I use stoichiometric ratios of the nitrate and the sulfuric acid, the reaction should still proceed fine, correct? Obviously the nitric acid will be more dilute, but I don't need very concentrated nitric acid anyway.
I realize I can distill the sulfuric aid to concentrate it, but I haven't done that before and would like to minimize the number of "dangerous" distillations I do. My vacuum pump is pretty shoddy and distillation of H2SO4 at ambient pressure requires so much heat,  it just seems like an unnecessary risk if 30% would work.


texts: What is the IUPAC name of the given compound?

texts:
IUPAC name of the given compound is

(1) 3-Hydroxycyclohex-4-en-1-one
(2) 5-Hydroxycyclohex-3-enone
(3) 5-Ketocyclohex-2-enol
(4) 3-Ketocyclohex-5-enol

By what I understand by assigning the priority the parent is the ketone.
If I number carbonyl carbon as 1, then I should move towards the alcohol group because it has higher priority than the alkene and both are at number 3, so the alcohol should be assigned the number 3 and alkene as 4?
So, according to me, the answer should be (1), but in the key it is given as (2).


texts: Will octahedral splitting occur in tribromidotricyanidocobaltate(III)?

texts: Octahedral splitting occurs strong field ligands are coordinated with the central atom. What if we have both types of ligands attached to the central atom as in $\ce{[Co(CN)3(Br)3]^{3-}}$, knowing that $\ce{CN^-}$ is a strong field ligand while $\ce{Br^-}$ is a weak field ligand.


texts: Why does ethylamine have two infra-red spectra? Are both correct?

texts:
The one I have in my textbook is this:

Shouldn't the first trough at $3500$ to around $3000$ mean that it's an $\ce{O—H}$ group with a $\ce{C—H}$? And then the other trough at $1700$ be a $\ce{C=O}$? Why is this ethylamine $\ce{CH3CH2NH2}$?

The other one I found on Google:

Shouldn't the $\ce{NH2}$ group have double troughs? The only trough there is the $\ce{C—H}$ at $3000$. How is this ethylamine?

Can anyone explain those spectra for me? Are both correct? I'm very confused.


texts: Why does silicon tetrafluoride have a higher melting point than sulfur tetrafluoride?

texts:
So looking at the Wikipedia pages of sulfur tetrafluoride and silicon tetrafluoride, the melting points are −121 °C and −90 °C respectively, and so $\ce{SiF4}$ has the higher melting point. However, their boiling points are −38 °C and −86 °C, respectively, giving $\ce{SF4}$ the higher boiling point.

I can justify that $\ce{SF4}$ has the higher boiling point because it is more polar since its Lewis structure has a lone pair on the sulfur atom, and so it experiences greater dipole-dipole forces. However, why does $\ce{SF4}$ have a lower melting point?


texts: Will strong concentrated acid destroy litmus paper and pH paper if they are dipped in acid?

texts: I am curious to know what will happen if I have litmus paper and pH paper, and I dip them into strong concentrated acid like conc. $\ce{H2SO4}$ to test its acidity or basicity. Will acid destroy papers? if YES, then how will I determine the acidity? do I need something else to carry my experiment?


texts: Electroless Plating of Zinc onto Copper in NaOH Solution

texts:
I’m researching how the classic “alchemy” demonstration works in which zinc is plated onto a copper penny in a solution of sodium hydroxide. Most online resources refer to the electroplating of copper with zinc, which is not what I’m interested in. The best article I’ve been able to find on the electroless plating of zinc onto copper is from the Royal Chemistry Society. However, I have several questions. The three reactions this article describes are:

$\ce{Zn(s) + 2NaOH(aq) + 2H2O(l) -> Na2Zn(OH)4(aq) + H2(g)}$, which is the “formation of sodium zincate”

$\ce{Zn(s) -> Zn^2+(aq) + 2e- }$, which is the “electrode reaction” at the “zinc electrode” and is “followed by the complexing of the zinc ions as $\ce{Zn(OH)4^2- (aq)}$”

$\ce{Zn(OH)4^2- (aq) + 2e- -> Zn(s) + 4OH- (aq)}$, which is the “electrode reaction” at the “copper electrode”

I really don’t understand how these three reactions come together to describe the plating of the zinc onto the copper. Specifically, I don’t understand:

1) What is the role of zincate, $\ce{Zn(OH)4^2- (aq)}$, in the reaction?

2) On the molecular level, how are the zinc and copper actually attached together?

3) How is this an electrochemical cell (i.e. how is electricity involved)? Where can I learn more about electrochemical cells?


texts:
I just read an experiment in which mercury has to be heated and in the same experiment there was a note warning not to inhale mercury vapors as they are very harmful.

I just can't get the point that why are mercury vapors harmful.


texts:
Luminescence in general, is the term of emission of light from specific substances/objects. Chemiluminescence is the emission of light due to chemical reactions. Bioluminescence on the other hand is the emission light from living/biological organisms such as insects ( this is of course the way I understood them ), but I'm a little bit confused because what is the cause that makes insects emmit light? Doesn't that also have to do with chemical reactions but inside living organisms ?

Just a clear explanation of the difference  between these two terms  would be helpful.


texts: Why can solid lubricants operate only at lower temperature in oxidizing environment but higher temperature in reducing environment?

texts:
The two main dry lubricants are graphite and molybdenum disulfide. They offer lubrication at temperatures higher than liquid and oil-based lubricants operate. Dry lubricants are often used in applications such as locks or dry lubricated bearings. Such materials can operate up to 350 °C (662 °F) in oxidizing environments and even higher in reducing / non-oxidizing environments (molybdenum disulfide up to 1100 °C, 2012 °F).

Source: Wikipedia contributors, "Dry lubricant," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Dry_lubricant&oldid=870516892 (accessed July 24, 2019).

Why can solid lubricants operate only at lower temperature in oxidizing environment than in reducing environment?


texts: Curious about the chemistry of Carbon-14 after it's produced in the atmosphere

texts:
It's often explained how $\ce{^14C}$ is formed in the upper atmosphere, a neutron hits a nitrogen atom and ejects a proton.  Source.  Since this is likely to happen to an $\ce{N2}$, I'm curious what the chemistry that follows is.

Does the energy of impact split the molecule, leaving a lone $\ce{^14C}$ and a lone $\ce{^14N}$ (and a lone hydrogen), (each highly eager to bond with something) or does it leave a $\ce{C-N}$ which might also readily bond with $\ce{O2}$ or maybe something else.    I'm mostly curious what the immediate chemical reactions are after the $\ce{^14C}$ forms cause it seems to me that it should be initially pretty reactive.

Edit & maybe a partial answer:

It occurs to me after giving it some thought that if an $\ce{N2}$ is split into a free $\ce{C}$ and a free $\ce{N}$, each would be most likely to bond to an $\ce{O2}$, or a single $\ce{O}$ from $\ce{O3}$ if the split happens near the ozone layer (which is possible given the listed height where most $\ce{^14C}$ forms, "altitudes of 9 to 15 km" - same link as above).
Initially I was thinking it might be more exotic than that, but having given this some thought I think that's what happens.   The $\ce{C}$ and the $\ce{N}$ split and mostly each binds with $\ce{O2}$, 2nd most common they bind with $\ce{O}$.  $\ce{CN}$ is probably pretty uncommon, now that I think about it.


texts: How would I neutralize a PEP (Phosphoenolpyruvic) acid?

texts:
PEP (Phosphoenolpyruvic acid) is acidic but I need to make it neutral. I need a solution (pH 6-8) of PEP in a final 1 mL volume with a concentration of 100 mM.

How would I make this?


texts: Most activated position on para-terphenyl for EAS

texts:
Para-terphenyl: it doesn't look pretty with all those math-y numbers, but those are going to come helpful in answering my question!

A question asked me to tell the expected product when this reacts with $\ce{Br2/FeBr3}$. Now, I have done such questions with all types of fancy organic molecules ranging from benzene to picric acid to parantiroanisole etc. I know that I am supposed to find the most activated position1 for EAS. But I have never done more than one phenyl ring at once.

So, in this question, I have drawn the eight resonating structures (without charge separation) of paraterphenyl manually. Here they are:

But, as you can see, every position seems to be activated identically. Each position has their own share of electrons through a pi bond, but it ends up being completely symmetric.

So, how do I find the most activated position in this compound?

1:Clarification: By "most activated position" I mean the position with maximum electron density. For example, in aniline, those are the ortho and para positions.


texts: What is the chemical equation for wine fermentation?

texts:
I am researching about the impact of sugar on wine fermentation, so I am looking for the equation of that reaction. However, there are a few different versions from different sources, so I was wondering which one is the right one to use and what does each equation represent?

\begin{multline}
\ce{Glucose + 2 NAD+ + 2 Pi + 2 ADP ->}\\
 \ce{2 pyruvate + 2 NADH + 2 ATP + 2 H+ + 2 H2O + heat}\tag{1}
\end{multline}
\begin{gather}
\ce{C6H12O6 -> 2CH3CH2OH + 2CO2 + ATP}\tag2\\
\ce{C6H12O6 -> 2C2H5OH + 2CO2}\tag3
\end{gather}


texts: (Literature) Diffusion Coefficient Of Potassium Permanganate

texts:
I'm doing a practical report on an experiment I had this week where I studied the diffusion coefficient of KMnO4 in water by the free boundary method. I have calculated the diffusion coefficient of potassium permanganate using this method, but now I need to compare this calculated value against the literature diffusion coefficient value of KMnO4. I've looked in my textbook and looked through a bunch of websites, but I just can't seem to find this value. If anyone can help me find this value or could tell me what it is, it would be very much appreciated.

Edit: No need to answer this question anymore since I spoke to my Scientific Officer and she said I should leave out the comparison of this literature value with the measured one. I'll leave this question open for answering though since someone might run into the same problem as I have in the future.


texts: Enols and enolates in biosynthetic pathways

texts:
I'm having a little trouble unterstanding the way organisms carry out aldol and claisen type reactions. I'm familiar with the laboratory procedures to which I understand there is a correlation.

Inside a cell there are no strong bases, since their existence would lead to the destruction of proteins. However, the reactions mentioned above, need a decent base in order to occur. From what I've read, the presence of enzymes is what obviates the need for a strong base, leading to enolates existing for a minimal ammount of time. On the other hand though, I've read in some notes that these procedures are carried out by the enol form, not the enolate. So my question is what kind of nucleophile is formed in the beggining of these reactions?


texts: Is there any way to use syringe pumpe in pumping flow

texts: I want to use syringe pump to pump water at 0.82 ml/min for 30 min ? Is that possible ( I read some paper use that but don't know how ?)


texts: What resonance structure is the most abundant in sulfur trioxide: the one with one double and two single, the one with two double and one single or the one with all three double bonds? Is it actually correct to write an expanded octet when it is not necessary?


texts: problem with loops over basis sets in psi4 using python

texts:
I've recently started using the psi4 quantum chemistry software. I wanted to compare a couple of different basis sets (mainly pople style) on an amino acid. So I've written a python code inside the input file to iterate over the different sets.But only the first loop runs and the second fails miserably giving an error code:

PSIO_ERROR: Attempt to write into next entry: 35, SO-basis Overlap Ints
PSIO_ERROR: unit = 35, errval = 18
PSIO_ERROR: 18 (Incorrect block end address)
Traceback (most recent call last):
File "<string>", line 42, in <module>
File "/usr/share/psi/python/driver.py", line 617, in energy
procedures['energy'][lowername](lowername, **kwargs)
File "/usr/share/psi/python/proc.py", line 1231, in run_scf
scf_helper(name, **kwargs)
File "/usr/share/psi/python/proc.py", line 1457, in scf_helper
e_scf = psi4.scf(precallback, postcallback)
RuntimeError: PSIO Error

here is my code:

basis_sets = ["6-31G", "6-31G*", "6-31G**"]
for basis_set in basis_sets:
    set basis =  $basis_set
    energy('scf')

I've tried to run it without the code and there was no problem.
I copied the code from the psi4 tutorial page for python scripting
Thanks for the help.


texts:
I know that some acids for sure and for certain are polyprotic. For example sulfuric acid $\ce{H2SO4}$ is diprotic giving you disulfate $\ce{HSO4-}$ and sulfate $\ce{SO4^2-}$

However not all acids with multiple hydrogens are polyprotic, even if 2 or more hydrogens are attached to very electronegative atoms. So if I am given an acid and it's chemical structure how would I know if it is polyprotic or not? Acid base reaction with something like sodium hydroxide $\ce{NaOH}$  and then distillation to separate the product/products from the water that is produced? Or is there a better way to prove whether or not an acid is polyprotic?


texts: What happens to Aluminium in Autoclaved Aerated Concrete

texts:
Aluminium is used in Autoclaved Aerated Concrete in order to produce the holes.

On Wikipedia I'm reading about the ingredients: sand, calcined gypsum, lime (mineral), cement, water and Aluminum powder.

Also it says "Aluminum powder reacts with calcium hydroxide and water to form hydrogen".

I'm wondering what Aluminium ends up as if anyone can help with detailed reactions.


texts: Why oxygen leaks from tires faster than nitrogen?

texts:
In critical applications tires are inflated using pure nitrogen (link).

  Nitrogen molecules have a more difficult time escaping through the
  microscopic spaces that exist between a tire's rubber molecules. [...]
  Nitrogen reduces the loss of tire pressure due to permeation through
  rubber over time by about 1/3. (source)

According to WebElements, nitrogen bond length (109.76 pm) is smaller than oxygen bond length (120.74 pm), so why nitrogen permeation through rubber is said to be lower than oxygen?


texts:
It is known that, with regard to the elimination reaction, the Zaitsev product is the thermodynamically more stable product, which is also often the more substituted alkene while the Hofmann product is the thermodynamically less stable product and is usually the less substituted alkene. I have always thought that the substituents refer to alkyl groups. This is because the basis of the thermodynamic stability lies in hyperconjugation with $\ce {C-H}$ and $\ce {C-C}$ bonds.

However, I recently encountered a test question in which we were supposed to identify the Zaitsev product, from the two given product alkenes, based on the groups attached to the alkene $\ce {C=C}$ bond. The alkene double bonds both had two alkyl groups attached to them. The difference between them is that one had an additional $\ce {-OH}$ substituent while for the other double bond, the two other substituents were just hydrogen atoms. On this basis, the teacher said that the alkene with the $\ce {-OH}$ substituent was more substituted and hence, it was the Zaitsev product while the other alkene was the Hofmann product. I would like to ask if this identification was made correctly. Can the $\ce {-OH}$ group be considered to have increased the degree of substitution of an alkene and hence, allow it to be identified as the "Zaitsev product"?

Of course, it is known that tautomerisation would occur for such an alkene product as it is an enol. However, let us ignore this fact in this case.


texts: If liquid hydrogen fluoride autoionises, how can it be an insulator?

texts:
According to Wikipedia, one of the last major hurdles in the isolation of elemental fluorine was the need to mix hydrogen fluoride with another substance in order for its electrolysis to be possible (Henri Moissan eventually hit upon potassium bifluoride, which is still used for this purpose today).

From "Fluorine Isolation":

  Edmond Frémy postulated that electrolysis of pure hydrogen fluoride to generate fluorine was feasible and devised a method to produce anhydrous samples from acidified potassium bifluoride; instead, he discovered that the resulting (dry) hydrogen fluoride did not conduct electricity.

And from "Henri Moissan Preparation of elemental fluorine":

  Moissan eventually succeeded in preparing fluorine in 1886 by the electrolysis of a solution of potassium hydrogen difluoride ($\ce{KHF2}$) in liquid hydrogen fluoride ($\ce{HF}$). The mixture was needed because hydrogen fluoride is a nonconductor.

However, hydrogen fluoride is a protic solvent, and undergoes autoionisation via the following reaction:

$$\ce{3 HF <=> H2F^+ + HF2^-}$$

Pure liquid $\ce{HF}$ should, therefore, conduct electricity at least weakly, like liquid water does.

What gives?


texts: Why iron(II) spectrometry is not measured in distilled water and it requires a complexing agent like o-Phen?

texts: We know that iron(II) ions in water have a green colour. Why we cannot draw the spectrum of iron(II) directly in distilled water to measure the absorbance then determine the concentration of iron(II)? We generally use ortho-phenanthroline as a complex agent to form a red-orange coloured complex with iron(II), then measuring the absorbance and the concentration. Why we Cannot use just distilled water as complex agent knowing that it gives green colour with iron(II)?


texts: Relative energies of singlet and triplet states in Jablonski diagrams

texts: In a Jablonski diagram, we have singlet and triplet excited states where spin is conserved or changed, respectively. My book says any singlet excited state is found to have higher energy than the corresponding triplet state from the same electron configuration. Why is that?


texts: Changes in pressure for an equilibrium reaction containing a solid/liquid on one side only

texts:
For a reaction where there is only one solid/liquid present, but gases present as both reactants and products (are there any examples of this type of reaction?):

$$\ce{A(s) + B(g) <=> C(g)},$$

if pressure is increased, it will favour the formation of the side not containing the solid/liquid (e.g. the forward reaction favoured), so as to decrease pressure of system – since one mole of a gas molecules has a considerably lower volume than a mole of any solid or liquid (far more spread out).

And the opposite if pressure decreased.

E.g. all that is considered is which side the solid/liquid is on, not the moles of gas present on either side. Is this true?


texts:
Is it safe to drink out of a bottle that use to contain Dichloromethane?  What should I use to clean a bottle of Dichloromethane?  Is there any chemicals that I could use to dissolve the Dichloromethane and make it safe to drink out of?

More info:

So if I had a glass bottle containing >= 99.5% Dichloromethane with amylene as a stabilizer and left out overnight is that safe? The bottle was used in a chemistry department so it is high quality, I would assume. Made from the company Sigma-Aldrich and in a Glass bottle.


texts: Do both electrons in a dative bond come from the same atom?

texts:
The textbook definition of a dative bond is that it is a bond "in which the two electrons derive from the same atom" (credits).

However, I found that the two electrons of a dative bond may come from different atoms, and the two electrons of a "normal" bond may come from the same atom.

For example, consider the following reaction:

$$\ce{CH3CHBrCH3 + NaOH -> CH3CHOHCH3 + NaBr}$$

The $\ce{C-O}$ bond in $\ce{CH3CHOHCH3}$ would be an example where both electrons actually come from the $\ce{O}$ atom.

Actually, one of the electron may not have come from $\ce{O}$, but the $\ce{Na}$ atom!

What further complicates things is that all electrons are equal, so how can we tell their origins?


texts: Are all monomers in a polymer covalently bonded?

texts:
I'm approaching chemistry and I read on Wikipedia that

  The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger"

But then the article goes on and it says:

  Historically, products arising from the linkage of repeating units by covalent chemical bonds have been the primary focus of polymer science; emerging important areas of the science now focus on non-covalent links.

So now I'm wondering, are there polymers whose monomers are bonded in other ways?


texts: In my lab courses, we were taught to use textbooks off the shelf as elevating props to adjust the heights of heating mantles to the right height during distillations, but I was wondering if there was a safer and better way to do so? I recently used a different type of heating mantle that was like a nest and charred the cover of a textbook as well as a heat glove that I put on the second time to prevent further damage to the book.


texts: How to calculate the concentration of lead(II) liberated from lead(IV) oxide under acidic conditions?

texts:
What is the concentration of $\ce{Pb^2+}$ in a lake that has a pH of $6.0$ and is in equilibrium with $\ce{PbO2(s)}$ and atmospheric oxygen?

\begin{align}
\ce{PbO2(s) + 4H+ + 2e- &-> Pb^2+ + 2H2O} &
\log K &= 49.2
\end{align}

I spent so much time to solve this, but I could not, my final answer does not appear to make sense:
\begin{align}
  \mathrm{pH} &= 6 &
  \implies&& [\ce{H+}] &=10^{-6}\\
  \log K      &= 49.2 &
  \implies&& K &= 10^{49.2}\\
  K &= \frac{[\ce{Pb^2+}]}{[\ce{H+}]^4} &
  \implies&& 10^{49.2} &=\frac{[\ce{Pb^2+}]}{(10^{-6})^4} \\
  &&\implies&& [\ce{Pb^2+}] & =10^{25.2}
\end{align}

What is my mistake?


texts: Could you please help me or give me any source to understand the calculation of pH in acid and bases both strong and weak ? And pH in salt solutions ?


texts: pH indicator that will fluoresce under UV light

texts:
I'm interested in a pH indicator that will strongly fluoresce under a typical black light that anyone could buy.  I want to use an acid base reaction to get an idea of how fast two liquids mix in a new type of mixing device.  Therefore the pH indicator has to have a very rapid reaction rate with either acid or base so that mixing is the rate limiting step.

I remember someone using coumaric acid decades ago for something similar. He showed me some beautiful photographs of how the fluorescence went from bright green to colorless when the pH went from basic to acidic. However, I don't remember the particular isotope and can no longer contact this person.  In my planned tests, I was thinking of using a 20% excess of either acid or base (depending upon the chosen indicator) so that after the liquids mixed and reacted, the resulting solution would be either strongly basic or strongly acidic.  Of course this depends on the indicator.  But something like the coumaric acid idea would work well in my case where I want to take photographs.  Ideally, I would like the chosen indicator to be environmentally safe.

Thanks.


texts: How to determine omitted units in a publication

texts:
I have found a 1954 paper in J. Am. Chem. Soc. which gives various temperatures in degrees but does not specify units.

A snippet of the introduction is:

  Titanium reacts appreciably with fluorine above 150°…

If I were feeling charitable, I might excuse the "units are for wimps" attitude as reflecting a commonly understood standard for that publication at that time. Perhaps my searching was poor, but I couldn't find an ACS standard or style guide for the 1950s era.

Given the location and time, I would guess that the temperatures are in degrees Fahrenheit, but I can't be sure they're not Celsius. Is there any reasonable way to determine which units the authors were actually using?

I don't have access to the full paper, just the first page at the link below.

Haendler et al., J. Am. Chem. Soc., 1954, 76 (8), pp 2177–2178
DOI 10.1021/ja01637a038


texts: When the intermolecular forces in a liquid increase, does the equilibrium vapor pressure of the liquid at a given temperature increase or decrease?

texts: I assumed it would increase, but I think I am wrong. I know that when the forces are strong, the vapor pressure would decrease. Does this same principle apply to the IM forces increasing?


texts: Why is ionization energy of indium less than gallium?

texts:
In group 13 we observe an irregular trend in ionization energy: B > Tl > Ga > Al > In.

Gallium has a filled 3d subshell, but indium has a filled 4d and 3d subshell. Thus it should have more poor shielding along with more ionization energy, but that is not the case why?


texts: Why acetaldehyde and acetone have almost equal water solubility?

texts: Given that boiling point of acetaldehyde and acetone are different due to H-bonding, why doesn't H-bond affect the solubility of these compounds in water?


texts:
This is freely translated, I hope it's not too bad.

The reaction to dehydrate methylcyclohexane to toluene in the gaseous phase:

Formulate the reaction equilibrium's constant.

Now, that's not a problem - the problem is that I don't know the aggregate state. I know that $\ce{H2}$ is a gas and that other thing left of it seems to be toluene, which is also a gas according to the text above. So how should I now know what aggregate state the methylcyclohexane is in? I also assume everythings at standard conditions.
The solution is apparently (but it might be wrong, since it's not an official solution)

$$K_1 = a_\ce{C7H14}^{-1}\cdot a_\ce{C7H8}^1\cdot a_\ce{H2}^3 = \left(\frac{c_\ce{C7H14}}{c^\circ}\right)^{-1}\left(\frac{c_\ce{C7H8}}{c^\circ}\right)^{1}\left(\frac{p_\ce{H2}}{p^\circ}\right)^{3}$$
$$K_2=a_\ce{C7H14}^{1}\cdot a_\ce{C7H8}^{-1}\cdot a_\ce{H2}^{-3} = \left(\frac{c_\ce{C7H14}}{c_\ce{C7H8}}\right)^1\left(\frac{p_\ce{H2}}{p^\circ}\right)^3$$

whereas $K_1$ is right and $K_2$ is left.
I mean that's clear and everything but how do I know the aggregate state of $\ce{C7H14}$?


texts: Why is nitric acid such a strong oxidizing agent?

texts: In my teaching-lab experiments I've seen that nitric acid solutions are able to facilitate the dissolution of metals such as silver, even though they are more active than hydrogen. Does anyone know why nitric acid is so special? Why is it such a strong oxidizing agent?


texts: If sulphuric acid barely evaporates, why we can smell it?

texts: If sulfuric acid barely evaporates, why we can smell it? Or does it give off sulfur dioxide gas?


texts: I would like to know how adsorption works particularly between a gas and a solid. I know that there is an attraction of intermolecular forces between the gas molecules and the solid surface molecules. But how can this attraction suck all the gas molecules onto the solid surface? I thought the intermolecular forces cannot act at such long distances. Any idea?


texts: Which of the following have the same molecular formula as the molecule shown in the model?

texts:
This model has 3 hydrogens connected the the first and last carbon and 2 hydrogens connected to the other carbons

Finding the same molecular formula as the alkane model I have to check all that apply

I know the last two options are not correct, because they don't have the same amount of carbons, but when it comes to the first two I'm confused because there is only two carbons attached to 3 hydrogens yet in these options there are 3 different carbons attached to 3 hydrogens.

Would they both be correct or does it matter if it's connected to the second bond instead of the third?

Im assuming since they are isomers that they are equal to eachother.


texts: Indirectly Measuring Diffusion of NO2 into Water

texts:
I am working on a data science project with the central hypothesis is that air-born pollutants can become water-born through diffusion. The example I am using as a proof of concept is $\ce{NO2}$. The problem I am having is that I do not understand the chemistry of how it interacts with $\ce{H2O}$ outside a laboratory setting that well.

$\ce{NO2}$ reacts with $\ce{H2O}$ to form $\ce{HNO3}$, $\ce{HNO2}$, $\ce{H+}$, and $\ce{NO3-}$. In addition, $\ce{HNO2}$ also reacts with water to form $\ce{NO}$, $\ce{H+}$, and $\ce{NO3-}$.

Do these reaction happen so fast that measuring dissolved $\ce{NO2}$ or $\ce{HNO2}$ in a sample an unreliable measurement?

If so, what is the best measurement I can use? $\ce{H+}$ and $\ce{NO3-}$ are both part of a lot of other very complicated biological pathways and have even more possible sources, so there is no way they can be relied upon. That leaves $\ce{HNO3}$, $\ce{HNO2}$, or $\ce{NO}$ as possibilities. Which of those would be the best to use as an indirect measurement?

Thanks for any help you can offer in advance. I am decent enough at chemistry in a lab, but application to real world systems is way beyond my abilities.


texts: R, S Configuration and Branching - Which Path?

texts:
Which path do I take when we have a branched chiral center? None of the textbooks I've consulted adequately covers this or even provides an example problem in which there was branching.

Consider the above:

1) Chiral carbon with the following attachments H, an carboxylic acid group, a methyl group, and then the ring.

2) H gets the lowest priority.

3) The methyl group gets the second lowest priority since it has just one carbon and then hydrogens; the other paths have either more carbons or oxygens!

4) Between the carboxylic acid group and the path along the ring, we have an oxygen and a hydrogen going for the carboxylic acid group. But which path do I take? After comparing the carbon in the carboxylic acid group to the carbon on the ring, do I compare the double-bonded oxygen to the next carbon on the ring or the single-bonded oxygen? How does one choose in cases of branching such as these?


texts:
Question:

  Which one is larger: an atomic mass unit based on the current standard or one based on the mass of a Be-9 atom?

My attempt:

Current standard is $1/12$th the mass of a C-12 atom. New standard is $1/9$th the mass of a Be-9 atom.

Now I understand that the only the basic unit of measurement of masses is changing. The absolute masses of the different atoms in the universe remains the same. That means the absolute mass of an He-atom in the old system and in the new system must be the same.

Now, absolute mass (of an atom in any system) = no. of "amu"s of that atom * mass of 1 amu (in that system)

We are supposed to determine the relation between the mass of 1 amu in the old and in the new system. Obviously, the one having more "amu"s would have a smaller mass of 1 amu.

And now I am stuck. I can't proceed further than this much explanation. I've looked on Wikipedia and some other questions but can't find similarities. Hints are appreciated!

UPDATE: although not explicitly mentioned, the book does NOT expect readers to look up data tables to find the answer. It expects a possible reason as to why is the Be-9/C-12 scale larger.


texts:
Rank the following compounds in decreasing order of acidity:

2-Fluorobenzoic acid
2-Chlorobenzoic acid
2-Bromobenzoic acid
2-Iodobenzoic acid

My approach
Since the ortho effect is proportional to the size of the substituent, it will be the greatest in the case of iodine and smallest in the case of fluorine. So, the molecule will be more non-planar in 2-iodobenzoic acid.
So resonance will be inhibited in all the above compounds. But what will happen to the acidity?


texts:
I have some water-soluble crystalbond that is attached to silicon and, because of some overheating (to about 150 Celcius) during a final processing step, the crystalbond seems to have charred (white/grayish colour, see photo at the bottom) and is no longer dissolvable in water. Since this silicon is important and cannot be replaced, I really need to find a way to chemically remove this overheated crystalbond residue without using abrasives that could scratch of the thin SiO$_2$ coating on silicon.
Looking at the MSDS (see here), crystalbond is composed of the following

97% Nonylphenol Polyethylene Glycol Ether(127087-87-0) EC-No.
500-315-8
3% Polyethylene Glycol(25322-68-3)EC-No. 500-038-2

My question is: does anyone have any ideas for what crystalbond decomposes into around 150 C and how one could remove this overheated crystalbond residue?
Things I have tried (unsuccessfully)

Hot DI water (in a cup, and in a ultrasonic bath)
Acetone
2-propanol/ethanol
"Piranha" etch (asked a lab friend to do this, too scary for me!!)
Photoresist remover (lab friend also tried this)
Hexane
Dunking in LN2
Putting on a hot plate at 225C for about 24 hours
Burning under a 1100C torch for about 30 seconds

Any bright ideas, especially from organic chemists? All I can say is: damn this stuff doesn't want to come off.
Some examples of the residue below.
Lots of crystalbond residue on this Silicon wafer

Another silicon wafer with crystalbond residue. Less than the one above, but still significant.


texts: Isn't the reaction of chloral with sodium hydroxide a disproportionation reaction?

texts: Chloral undergoes a haloform reaction with sodium hydroxide. Now the carbon atoms in chloral are in the $\mathrm{+III}$ and $\mathrm{+I}$ oxidation state. Chloroform’s carbon is in the $\mathrm{+II}$ oxidation state, as is sodium formiate’s. Now, carbon has both been reduced and oxidised. Then why is it not a disproportionation reaction ?


texts:
While studying the basics of chemical bonding, I've often come across the following statements:
1. The bond energy increases with the increase in the s-character in a hybrid orbital, i.e sp3 sp2-sp2, and so on.

I can't seem to correlate the two. If a hybrid has a higher bond energy, shouldn't it also form stronger bonds?


texts: Soluble compounds to absorb radio-frequency electromagnetic radiation

texts: Are there any soluble compounds capable of absorbing radio-frequency or long microwave  radio-frequency electromagnetic radiation? I have noted that metals are often used to absorb these signals, but I cannot find any absorption spectra for radio/long microwave wavelengths.


texts: Find the number of water molecules "embedded" in sucrose

texts:
Recently I got a question as follows:

  How many molecules of water are joined with 12 atoms of carbon in a molecule of sucrose ?

  (A) 12

  (B) 11

  (C) 6

  (D) 10

I am unable to understand the question.
What actually is the question ?


texts: Why does the stability of ascorbic acid decrease (increased rate of oxidation to dehydroascorbic acid) when pH increases?

texts: I am doing a Chemistry IA on the stability of ascorbic acid in different pH, and found that the stability decreased (there was a lower final concentration of ascorbic acid) as pH increases. Why is this so?


texts: Cram's rule for nucleophilic addition to carbonyl groups

texts: I recently heard about Cram's rule for predicting the stereoselectivity in nucleophilic additions to carbonyl groups. Can anybody explain what this is and whether it is an accurate rule?


texts: Making a 10L HCl solution with 8.77% HCl in a 100 mL solution from a 16 M stock solution

texts:
How would you make 10L of HCl solution with 8.77% HCl in 100 mL from a 16M stock solution.

Here's what I have tried so far:

I put my percent HCl and got that down to match with the moles of HCl I had. Then I took 1.754% of 20 ml and converted that into liters. Then I found the molarity of the HCl I need to turn the 16 M solution into. Finally I did a dilution calculation to find the volume of water needed to make the 16 M stock solution into the starting percentage of HCl.

I am fairly certain that I am diluting with water, I don't know what else it would be with.

Is this the right way to go about this, or do I need to restart. Any help is much appreciated, and thanked for in advance!


texts: According to Markovnikov rule and stability of carbocation which is most likely to form if HI "excess" is not given?

texts:
Problem

Answer                          >
I thought "I" can stabilizes carbocation formed intially by resonance so there can be a shift of (+) to the carbon close to "I" and hence forming the product 1,1-diiodopropane but given is 1,2 product , whats wrong in this ? Or is that H+ and +I combined effect of CH3 is slightly greater than compared to resonance of "I"?


texts: Why is mass proportional to the strength of a dipole-dipole attraction? meaning more mass more strength

texts: I don't understand why the mass of a molecule make it attract more to other polar molecules.


texts: SI Units for Isothermal Incompressibility and Specific heat capacity at constant volume

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I am looking for the SI units of isothermal incompressibility and specific heat capacity at constant volume.

What I found was that isothermal compression was measured in " $\mathrm{m^2}\ \mathrm{N^{-1}}$" so I'm guessing isothermal incompressibility would be the same?

I also found that specific heat capacity was " $\mathrm{J}\ \mathrm{K^{-1}}$"so is this the same units for constant volume also?


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In general, is it true that if I connect an aqueous oxidant to an aqueous reductant via a wire then a current flows along the wire? In particular, does current flow in the following scenario?

Imagine putting one end of a wire in hydrogen peroxide (a common oxidizer) and the other end inside water containing formic acid or pure carbon (reductants).

I understand that standard Energizer alkaline batteries are composed of separated $\ce{Zn}$ and $\ce{MnO2}$. Connecting the terminals allows electrons to flow from the $\ce{Zn}$ to the $\ce{MnO2}$, oxidizing/reducing them to $\ce{ZnO}$ and $\ce{MnOOH}$.


texts: I know that the two should not be mixed, but i want to know that if the two become mixed in a contained unit, does it build pressure? Or can you seal the container safely untill it can be disposed of properly?


texts: Why Ammonium bifluoride is used in the iodometric estimation of copper in brass?

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When brass solution (mixed with nitric acid and urea) is to be estimated for amount of copper present, ammonia is added to neutralize the solution. This gives a turbidity which can be dissolve by adding ammonium bifluoride (NH4HF2).
What exactly causes the turbidity? Which compound formation is responsible for the turbid appearance?


texts: How does one compute the number of unique 2-electron integrals for a given basis set?

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I have run into trouble with an exercise in Szabo and Ostlund's Modern Quantum Chemistry.

  Exercise 3.14: Assume the basis functions are real and use the symmetry of the two-electron integrals [$(\mu\nu|\lambda\sigma)=(\nu\mu|\lambda\sigma)=(\nu\mu|\sigma\lambda)$, etc.] to show that for a basis set of size $K=100$ there are $12,753,775=O(K^4/8)$ unique two-electron integrals.

I have seen answers to this on the Physics SE here and here, but the case-by-case analysis used in the answers seems confusing to me and not easily generalized to other values of $K$. The symmetry of the integrals when all the basis functions are real suggests that there should be a simpler way of determining this. How can one find the number of unique two-electron integrals in this case and, ideally, in general?


texts: What happens to the complex part of the wave function when doing LCAO?

texts: I understand that in general the wave function can take complex numbers, however when talking about combining atomic orbitals to form molecular orbitals we talk about the phase of the orbital being positive or negative to create constructive or destructive interference. It seems as if we have lost the aspect of the wave function taking on complex phase, what happened to it?


texts: Masamune's rule of diastereoselectivity multiplicity explained

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In a reaction between a chiral substrate and chiral reagent, their asymmetric inductions could cooperate (matched pairs) or compete (mismatched pair). According to Masamune, in a matched pair the degree of asymmetric induction is approximately the product of the selectivities of the substrate and the reagent. In contrast, the asymmetric induction in a mismatched pair is equal to the quotient of the selectivities of the substrate and the reagent.

The following reaction perfectly proves Masamune's rule (syn enolate is produced during enolization):

Why is this rule valid and why is it so accurate? What's the mechanistic explanation behind the multiplicity trend?


texts: What is the proper term for lines of constant volume and constant enthalpy on a thermodynamic diagram?

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I know an isotherm is a line of constant temperature.
Isobar is a constant pressure line.
Isentrope is a line of constant entropy.

But what do you call a line of constant volume? An Isochore?
And what do you call a line of constant enthalpy? An "isenthalp"?


texts: Reaction of benzenediazonium chloride with potassium ferricyanide

texts: I have gone through all my notes but could not find any reaction of benzenediazonium chloride with potassium ferricyanide. What are possible products?


texts: What is so special about positive hydrogen ions that they are used in pH calculation?

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I just learned about pH. If I understand it correctly, all it really tells is the concentration of positive hydrogen ions (protons) there are in a given liquid.

Why is this pH scale entirely dedicated to positive hydrogen ions? What is so special about protons/hydrogen ions? I would expect the scale to would count all positive ions, even if they are of atoms different from hydrogen. I don't understand why is the proton ion a "superstar", being so special that people made a scale dedicated just to it.


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I would like to ask a question about europium's stability in the $+2$ and $+3$ oxidation state.

The electronic configuration of europium in its neutral state is $\ce{[Xe] (4f)^7 (6s)^2}$.

Now, when in the $+2$ oxidation state, the electronic configuration is $\ce{[Xe] (4f)^7}$ and in the $+3$ oxidation state, it is $\ce{[Xe] (4f)^6}$.

Now, I thought the $+2$ oxidation state is more stable because it's a half-filled $\ce{f}$ sub-shell so there is less mutual repulsion between electrons in the same sub-shell.

However, an article from nature.com reads the following:

  Europium metal is now known to be highly reactive; the element's most stable oxidation state is +3, but the +2 state also occurs in solid-state compounds and water.

Now, I would like to ask, how is it possible for europium to be most stable in its $+3$ oxidation state, knowing what I have mentioned above?