texts:
Based on various other Stack exchange site (Mandarin Chinese, Russian and German), we adapt this project here for chemistry, since it's a great idea to have all kinds of resources in one place.

This is a specifically created Community Wiki which gathers resources for learning Chemistry. The lists are a community maintained project, hence everybody with more than 100 reputation points can contribute edits to the appropriate sections. If you feel something is missing, just fill it in. To avoid multiple answers for similar branches, we decided on a general outline, which is locked, i.e. no new answers can be added.
 If you have concerns or questions, you can discuss this list on its parent meta post. If they are of a more general concern, you can also post a new question on chemistry.meta.se. This procedure is used, so the comment section here does not become too overcrowded. If you do choose the second option, please leave the link to it in the comments to this post.

Organization

Answers have a type of resource each.
If possible, state whether the material is directed towards a beginner, intermediate or an advanced audience.
Do not include links that lead to illegal content or sites that host such content. If you see any, please flag for moderator attention and choose "other" so you can point us to the content. We'll delete it as soon as we see the flag. (You can of course also delete it yourself. If you do, please flag it anyway, so that we are aware of it. In this case it is crucial you fill in the edit summary with something like: Removed link to illegal content.)
Both free and commercial resources are allowed, but make sure to include a note if they are the latter. Remember the rules about self-promotion. Include also if registration is required.
Include links to the sites only, don't post images, they would take too much space.
Add the resources in alphabetical order so they're easier to find.
For the resources, a short summary is very much appreciated.

If you have questions about these guidelines, please head to meta to make yourself heard. The above points are not set in stone and might change in the future.

Alphabetical Index

(Text)Books: All books that teach you chemistry with theory and exercises. The subcategories are:

General Chemistry
Inorganic, Organic and Physical Chemistry
Analytical Chemistry, Biochemistry and Chemical Biology, Chemical Engineering, Computational and Quantum Chemistry, Theoretical Chemistry
You can add any subcategory to this post if it is missing.

Online courses and Websites: Free or paid services online that teach you chemistry through lessons as well as sites that give help for learning chemistry. They give material, tips, hints, and various help for self-learners or regular students.
Software: This can be any software ranging from plugins for the browser over mobile apps up to standalone applications for the computer. Pure 2D or 3D visualization programs as well as quantum chemistry programs might not fit in this category, as they are not primarily focused on teaching chemistry.
Video Resources & TV: Video resources which help learning chemistry.

Currently those are all categories. If you think, that a new one should be added, please submit an answer in the corresponding meta thread. (A comment is probably not sufficient, as it does "bump" the question on the active tab.


texts: Why is the work done by a gas during free expansion zero and not infinity?

texts:
Suppose there's a spaceship that has a hole in it. Gas is expanding through the hole from the spaceship to outer space (vacuum). According to pressure volume work ($P\Delta V$) the work done by the gas is infinity. According to my homework assignment, it's $0$. Can someone please explain why?

Edit:

According to Wikipedia:

  $P$ denotes the pressure inside the system and outside the system, against which the system expands; the two pressures are practically equal for
  a reversible process;

How can $P$ denote two different quantities? Can't this rule be applied for situations where the pressures inside and outside the system are different?


texts: The relationship between energy and air pressure?

texts: When boiling water at room temperature, what is the relationship energy has with the air pressure that is making the water boil cold instead of hot?


texts:
My chemistry teacher told us that graphite or diamond had an atomicity of infinity. However, the definition of molecule in my testbook is

  A molecule is the smallest part of an element or compound which can exist on its own under ordinary condition.

It doesn't make sense to me because if a molecule has an atomicity of infinity, it it is not a discrete compound anymore. It contradicts the definition of molecule.


texts: How do ionic, polar, hydrogen-bonding and non-polar compounds compare in TLC?

texts:
$R_\mathrm{f}$ decreases with increasing polarity. Does this mean a compound with an ionic bond would have the lowest $R_\mathrm{f}$? And nonpolar would have the highest $R_\mathrm{f}$?

Example: $\ce{RCOO- Na+}$ is ionic.  If the above is true it should have a lower $R_\mathrm{f}$ than cyclohexanol which has H-bonding?


texts: Comparison of stability of cyclic imines

texts:
I am looking for the reason for the lowest stability of cyclohexane-1,3,5-triimine (D).

I was not able to find any explanation using resonance or aromaticity.
All help is appreciated.


texts:
I am having trouble understanding how valence electrons are counted in Helium.

My references are:

Here where it appears that Helium has 0 valence electrons because the shells are finished
Here where it appears that Helium has two valence electrons (which is what I thought)

How many valence electrons does helium have?


texts:
I was going through a list of monodentate ligands, and I came across examples like $\ce{H2O}$ (which has 2 lone pairs), $\ce{Br-}$, $\ce{I-}$ (both of them have more than one lone pair). Similarly, thiourea has 4 lone pairs in all (2 from nitrogen and sulphur each).

When I searched about it, I realized that the oxygen in water can't simultaneously form bonds using both the lone pairs (due to some obvious geometrical reasons, it said).

However, I couldn't figure out any such (obvious) reasons in thiourea.

Can anyone please help?


texts: So hypothetically, if one was to buy krypton and wanted to make it glow, would a little tesla coil be enough to make it glow? If not, what would be enough? And would one be able to make it glow multiple times or just once, like will making it glow wear down the electrons in the noble gas or somethin’?


texts: Why does the conductivity of a LiOH solution decrease when boric acid is added?

texts: If I start with pure water and add $\ce{LiOH}$ the conductivity of solution increases. However, if I then dissolve boric acid in the same solution the conductivity falls. I would have thought adding more cations or anions to a system would always increase conductivity, but in this case it does not. Why is this?


texts: Does aniline breakdown in groundwater produce benzene

texts: Can the benzene ring attached to aniline be detached in an aqueous solution (specifically groundwater) under certain conditions? Would the two compounds be detected as separate entities in a laboratory analysis?


texts: Ultrasound Vegetable Glycerin homogenization

texts:
We are trying to homogenize VG (USP) with propylene-glycol using ultrasonic homogenizer with titanium probe, but we are experiencing very strange - bad odor from the emulsion after sonication.
We tried different amplitudes, different time settings, different power settings. We can control amplitude for 2 modes only, I believe they are 50% and 100%.
Also if I am sonicating pure vegetable oil for just 5-10 sec I can smell that strange odor, it is very similar to that, I am getting with VG.
I just want to know, what this smell can come from? From our probe? No it is clean, we can sonicate water well.


texts: surface energy versus surface tension and contact angles

texts:
I am hoping to measure the surface tension between two fluids (salt water and isopropyl alcohol), by measuring the appropriate contact angles, and applying Young's equation: https://en.wikipedia.org/wiki/Wetting#Simplification_to_planar_geometry.2C_Young.27s_relation
As far as I can tell, the surface energy and surface tension are interchangable, however I thought that I should ask people that know better than I do, just to make sure.


texts: Why does water cause a jet flame when poured over a bunch of tealights?

texts:
A neat party trick (typically for outdoors) is to build a pyramid of tealights, let them burn for a while and then pour a bit of water over it and see a large jet flame shoot out (see e.g. this youtube video).

I was always told that this is caused by the water spreading the liquid wax out allow more of it to burn at the same time, but I am not completely satisfied with that answer because, in my opinion, that cannot explain the large jet flame. Can someone explain why this jet flame occurs? Is it the wax vapour that catches fire, which can form at 370 $^o\ce{C}$, and is this the reason you need to build a close packed pyramid? But what is the role of the water then?


texts:
I learned that hydrogen bonding is formed from a 'sandwich' of hydrogen and either oxygen, nitrogen, or fluorine where nitrogen, fluorine, or oxygen is the bread.

Will oxygen gas and water form hydrogen bonds? The oxygen-hydrogen sandwich could be made, but oxygen gas has no hydrogen attached. Is it necessary for both molecules to contain hydrogen for hydrogen bonding to occur?

To make it clear, the question is: do both molecules have to contain hydrogen in order for hydrogen bonding to occur?


texts: Using the electrical potential created by the electron transport chain to power electrical systems

texts:
My friend and I were discussing the extremely low energy density of modern batteries and read that food has a much higher energy density. Thus, we were considering the possibility of using biological processes to extract energy from food and use that to create an electric potential or do work in some other way.

The electron transport chain creates an electrochemical gradient and thus and electric potential using protons. If some sort of system could be devised to mimic/perform glycolysis and the citric acid cycle and also mimic the ETC membrane and necessary proteins, is it feasible/is there already research on using glucose and cellular respiration (or a similar biological process) to power electrical systems? How would this relate to fossils fuels and what scale could this be useful at?


texts:
While reading some publications on solid superconductors, I encountered a term "chemical pressure" a few times, which is usually attributed to the changes of superconducting transition temperature $T_\mathrm{c}$ alongside with the hydrostatic, or physical, pressure. For the reference, consider this paper:
Chemical Pressure and Physical Pressure in $\ce{BaFe2(As_{1-x}P_{x})2}$ [1].
Whereas I can understand what the physical pressure is and how it's defined and estimated, I found no sources which would explicitly define either what chemical pressure is, or how it's measured (and what units are used) and/or analyzed.
All explanations are somewhat expansive and usually point to the effects of isomorphic substitution in the crystal lattice (ionic structure), or intermolecular repulsion between ligands (molecular structure). So, what chemical pressure is in the nutshell, how it's measured and expressed?
Reference

Klintberg, L. E.; Goh, S. K.; Kasahara, S.; Nakai, Y.; Ishida, K.; Sutherland, M.; Shibauchi, T.; Matsuda, Y.; Terashima, T. Journal of the Physical Society of Japan 2010, 79 (12), 123706 DOI: 10.1143/JPSJ.79.123706. (Open Access)


texts: Apparent paradox in the formation of ice at room temperature

texts:
The formation of ice out of liquid water can be written down like this:
$$\ce{H2O (l) <=> H2O(s)}$$
We can calculate the change in standard Gibbs free energy (per mol substance) in the following way:
$$\Delta G^\circ = \Delta H^\circ - T \Delta S^\circ$$
If we do this at room temperature $(\pu{298 K}),$ we get: $\Delta G^\circ = \pu{546 J mol^-1}.$
So we can see that this process is very non-spontaneous, which is what you'd expect, you never see ice forming at room temperature. However if we calculate the equilibrium constant $K_\mathrm{eq}$ for this reaction we get:
$$K_\mathrm{eq} = \exp\left(-\frac{\Delta G^\circ}{RT}\right) \approx \mathrm e^{-0.22} \approx 0.80$$
It's obvious that this is wrong, because at room temperature we never see liquid water in equilibrium with a decent amount of ice. I just don't know what I did wrong, I have checked my units and calculations but can't seem to find what I did wrong.


texts:
This question is a sort of follow-up to my earlier question.

I know about a method of solubilising potassium where the potassium atoms are "trapped" between layers of graphite, but I think that sodium naphthalenide exists only in solution (if a contradiction is found, please inform).

In the solution phase, say in THF, I would expect some THF molecules co-ordinated to the sodium, and an $\eta^4$ complex with naphthalene, involving one ring. An $\eta^{10}$ complex seems possible, involving both the rings, as the negative charge is distributed further, but I haven't read about any $\eta^{10}$ complex. An $\eta^1$ complex might be possible,  but the distribution of negative charge will be lesser.

I expect sometehing similar to the tetrahedral form of butyllithium.

What is the structure of sodium naphthalenide?


texts: Storage of methane in mineral oil or other liquid hydrocarbons

texts:
Is it practical (or even possible) to store gaseous alkanes such as methane or ethane in liquid non-polar solvents, such as mineral oil or vegetable oil, and how much more (or less) methane can be stored for a given pressure with solvent vs. no solvent?

After some research, I found that butane is sometimes dissolved in gasoline to make it evaporate more easily in cold weather. So it's definitely possible. However, I cannot find solubility figures (hence this not being an answer).


texts: Why isn't 'chemically-strengthened glass' made with potassium carbonate to begin with?

texts: Instead of making potassium-strengthened glass by creating ordinary soda-lime glass first, then replacing the sodium atoms/ions with potassium by putting the glass in a bath/solution of potassium nitrate, why not replace the 'soda' (sodium carbonate) in the initial process(es) with potassium carbonate?


texts: How is heat physically released in an exothermic process?

texts: Many non-covalent interactions (e.g. electrostatic interactions) result in decreased entropy and are driven by negative enthalpy. If the heat released in the reaction has its physical basis in an increase in the average kinetic energy of the degrees of freedom contributing to the heat capacity of the solution (i.e. surrounding water molecules move faster), how exactly does binding exert a force on these degrees of freedom? How does binding cause increased thermal motion of solution molecules? Is it simply that the two attractive moieties (e.g. a lysine and a glutamate residue) are accelerated towards each other as they convert potential energy into kinetic, and then release heat via collisions with solution molecules? Is all exothermic heat release the result of potential energy being converted into kinetic energy in reaction products and the subsequent collisions with solution?


texts: Does the water in hydrates affect final concentration?

texts:
Say I have a hydrate, and I am going to dissolve it in water. Does the water in the hydrate affect the final concentration?

Here's an example: If I have $\pu{249.69 g}$ of $\ce{CuSO4·5H2O}$, and dissolve it in $\pu{200 mL}$ of water, will the concentration be $\pu{5 M}$?


texts: Why can't we find the density and molarity given the masses of solute/solvent and molar masses?

texts:
From 2013 ACS Local Exam:

We have a $\ce{KNO3}$ solution prepared in water, and we know the masses of solute and solvent as well as the molar masses. I know that we can easily find molality, but how come density and molarity cannot be determined?

Since the solvent is water, can't the mass be converted to volume to find both values?


texts:
Question is simple.. If we take an atom of any element and then supply heat energy to it then what will happen?

What I thought is that in the beginning, energy (quanta; due to excitement of electron and then moving back to ground state) should be  evolved and then electron should be emitted... Am I right?


texts: I have around 1000 SMILES entries in Excel and I have to generate .sdf file for all. Is there any way to automate this whole process, preferably with an offline tool?


texts: What chemicals would need to be added to human urea to make it a nutritional substance?

texts:
I've been thinking about food supplies, waste management and sustainable living, particularly in highly isolated areas like a Mars colony or a space station, or also in a non-technically advanced situation like urban survival during a major emergency.

One of the major things preventing human urine from being drinkable is the prescence of urea.

An adult supposedly excretes 25 grams of urea per day.

What chemicals (and in what quantities) would be needed to turn this amount of human urea into:

a non-toxic, but non-nutritional ingestible substance?
a nutritional substance?

I am thinking specifically about how to simply add a tablet/capsule to urine and having a nutritionally viable drink within 60 seconds or so.


texts: How to compare SN2 rate of cyclopropane with bridged cyclic compound?

texts:
How to compare the SN2 rate of iodocyclopropane and 1-iodobicyclo[2.2.1]heptane?

Backside attack is must, but as the cyclopropane ring is planar it's quite impossible for back side attack. Then the bridge compound is non planar, we know in bridge compound both SN1 and SN2 substitution are bad, so I just confused in these two.


texts: A reaction in nature is, as we know, generally an interaction between the electron clouds of different atoms and nuclei. Why does this takes time?


texts: How to create liquid carbon, and what kinds of properties does it have?

texts: Carbon sublimes at about 3915K. In a high pressure environment, shouldn't it be possible to create liquid carbon at high temperatures? Has this ever been done? What does it look like and what properties does it have?


texts: Determining standard Gibbs free energy for water?

texts:
I am dealing with the dissociation of water into its components hydrogen and oxygen and I am trying to determine the standard Gibbs free energies of each component. My professor said if the substance is an ideal gas in the standard state then

$$g_{i}^{0}=g_{i}^{\text{pure IG}}(T, P_\text{ref})$$

Now this means I can determine it for hydrogen and oxygen because they can be treated as ideal gases, but how would I consider the standard Gibbs free energy for water?


texts: Zigzag line in the structural formula of budesonide

texts: Excuse me if this question is already answered, but while reading about budesonide, if came across a strange notation I have never seen. I am talking about zigzag line on the right sine. Can somebody, please, tell me what it is? Thank you very much.


texts: Is chemical equilibrium possible at any temperature and pressure?

texts:
Consider the chemical reaction ${\rm Na+Cl\to NaCl}$ by mixing ${\rm Na}$ with ${\rm Cl}$ (or by mixing ${\rm NaOH}$ with some acid). This process is exothermic while the reverse ${\rm NaCl\to Na+Cl}$ must be endothermic. Can these two processes exist in chemical equilibrium (by which I understand equal rates for forward and reverse reaction) at any temperature and pressure?

I'm from the physics background. Please bear with my naive question.


texts: Nomenclature of Dihydroxyacetone Phosphate

texts: Why the dihydroxyacetone phosphate is called that way when it has only one OH ?


texts: Large difference in boiling points of tetrafluoromethane and tetrachloromethane

texts: Why is carbon tetrachloride $\ce{CCl4}$ is seen to posses liquid state (b.p. $\pu{76.72 °C}),$ whereas carbon tetrafluoride $\ce{CF4}$ is in gaseous state at room temperature (b.p. $\pu{−127.8 °C})?$


texts: Why is the radius of the caesium cation smaller than that of the chloride anion?

texts:
I am currently studying the structures of ionic compounds and how we can use radius ratios to predict the possible arrangement of ions in the lattice. My book mentions that the cation to anion radius ratio in caesium chloride is about 0.93, and since this number lies between 0.732 and 1, it suggests a cubic arrangement with a coordination number of 8.

But caesium is in the 6th period of the periodic table whereas chlorine is in the 3rd. A caesium cation would be similar to xenon, which is in the 5th period. And a chloride anion would be similar to argon, a period 3 element.This means that there is a difference of two shells between the two atoms. How is the ionic radius of chloride still larger? In general, how many "shells of difference"  are required for a cation to be larger than an anion?


texts: What is the difference between transaldolase and transketolase in the pentose phosphate pathway? From what I understand, they both catalyze the transfer of carbon chains from 1 aldose into 1 ketose to produce 1 aldose and a ketose, though transketolase transfers 2 carbons while transaldolase transfers 3 carbons. Is that the only difference? If so, then why they were named "aldolase" and "ketolase"?


texts: How to distinguish between Na2CO3 and NaHCO3 by a chemical test?

texts:
$\ce{Na2CO3}$ and $\ce{NaHCO3}$ have similar reactions. For example, they can react with acid to produce $\ce{CO2}$.
So my question is:

  Can we use a chemical test to distinguish between $\ce{Na2CO3}$ and $\ce{NaHCO3}$?

I know that $\ce{NaHCO3}$ can be thermal decomposed into $\ce{Na2CO3}$ via this reaction: $2\ce{NaHCO3->} \ce{Na2CO3} + \ce{CO2} + \ce{H2O}$
However, I am not sure if thermal decomposition is a chemical test.


texts: Molecular dynamics simulation of a protein in acidic medium

texts:
I want to perform an MD simulation of a protein under acidic solvent conditions. A quick literature search seems to indicate that people are more interested in the protonation of protein side chains (which is important, of course), but seem to ignore the abundance of $\ce{H+}$ ions (i.e. $\ce{H3O+})$ in water surrounding the protein.
Is there a standard practice for performing MD simulations of proteins in acidic environments? Should I account for $\ce{H+}$ at low pH?


texts: In my class, my professor said that since hydrogen is in group one, it has a charge of 1+. Does this refer to its ionic charge or to its oxidation state?


texts: Is there a cheap, safe liquid that evaporates EXOthermically around room temperature?

texts:
The heating and AC system in the building where I occasionally work, works like this (basically a thermostat):

The administrators set some temperature that is maintained automatically. Say, in the winter, the outside temperature is 0 °C. The admins will set the desired inside temperature to 20 °C. There is some thermometer behind a little steel panel. It measures it to be cold in the room; therefore the heat comes on. I can trick the heat into coming on even more, by rubbing some alcohol or acetone on the steel panel. The acetone evaporates endothermically, making the steel panel REALLY cold; then the heater thinks that it's REALLY cold in the room and pumps the heat in.

The same system is in place in the summer, but in reverse. However, I can't trick the panel in the same way. If I put acetone on the panel, it'll cool off, and then the A/C unit thinks the room is just fine, because the panel is cool. I'm wondering if there is some liquid that will evaporate exothermically, and heat up the panel, in order to make the system think I need more A/C?

I don't believe that exothermic evaporate exists; here is a list of heat of vaporization for various substances; all positive (endothermic). http://www.engineeringtoolbox.com/fluids-evaporation-latent-heat-d_147.html
But maybe I'll be surprised and it does exist!

I have been holding my laptop's hot backside up to the panel instead, but that's a bit too manual for my taste.

Edit: To be a bit clearer, let me specify that this is just a thought experiment. I'm not actually expecting to find something which doesn't make sense like an exothermically evaporating liquid.


texts: What is the mechanism for the oxidation of Cu(I) by ammonium nitrate?

texts:
I can't seem to find any resource online that describes the arrow pushing mechanism behind the oxidation of Cu(I) by ammonium nitrate in acid.

Does a radical oxygen form? Or does it require both copper atoms simultaneously? I've drawn out a few possible mechanisms, but all seem plausible...

Here is the mechanistic formula:

$$\ce{2Cu(I) + 2H+ + NH4NO3 -> 2Cu(II) + H2O + NH4NO2 -> 2Cu(II) + N2 + 3H2O}$$


texts: What are the fundamental principles that are found throughout chemistry?

texts:
In the same way that biology has the fundamental idea that all organisms want to reproduce and pass on their genetic information, and that evolution accounts for the diversity of life, what are some of the ideas that tie chemistry together? Apart from all the specifics, what is chemistry really about at its heart?

Apologies if this sounds like a really strange question.


texts: Molecular orbital energies prediction with ML algorithms

texts:
In the recent years, computational chemistry community has focused on Machine Learning algorithms to predict molecular properties. Unfortunately, many of the authors of such papers are not chemists, and hence, there are little explanation on chemical aspects of this type of works.

One well known problem is to predict different properties of QM9 dataset given their atom features. The properties include HOMO/LUMO orbital energies, atomization energies, etc. The inputs include type of heavy atoms in the molecule, type of their bonds, type of atom hybridization, etc. You can see a complete list in the following tables

The question is how the inputs are related to the outputs. For example, I understand that HOMO\LUMO energies are solutions of the electronic Schrödinger equation. But which one of the inputs features affects these? I appreciate it if someone can expand on which ones affect frontier molecular energies. Thanks!


texts: When is the product a compound and when is it 2 ions in these reactions?

texts:
When finding the half equation and overall redox equation for the following:

a) $\ce{Fe^2+(aq) + Cl2(g) <=>}$
b) $\ce{N2(g) + H2(g)  <=>}$

The solution from the textbook is given below. I do not understand why the products (in the overall reaction) for a) are 2 individual ions (and not $\ce{FeCl3}$ whilst the product for b) is a compound (and not $\ce{2N3- + 6H+}$).

One difference I noted was, when the electrons are balanced for a) it gives $\ce{2Fe3+}$ and $\ce{2Cl-}$ , which cannot go together unless its $\ce{2Fe3+}$ and $\ce{6Cl-}$, whilst for b), when the electrons are balanced we have $\ce{6H+}$ and $\ce{N2}$ which combine as is to form $\ce{2NH3}$. Is this the reason?

The solution given is:

a)
Oxidation: $\ce{2Fe^2+(s) -> 2Fe^3+ + 2e- }$
Reduction: $\ce{Cl2(g) + 2e- -> 2Cl- }$
Overall: $\ce{2Fe^2+ (aq) + Cl2(g) <=> 2Fe^3+ + 2Cl- }$

b)
Oxidation: $\ce{3H2 -> 6H+ + 6e-}$
Reduction: $\ce{N2 + 6e-  -> 2N^3-}$
Overall: $\ce{N2(g) + 3H2(g)  <=> 2NH3}$


texts: Stripping zinc electroplating with phosphoric acid - hydrogen danger?

texts:
I'll start by saying that I'm not a chemist, more of an artist. I'm stripping zinc electroplating from some regular hex bolts, nuts, and washers. I'm using a product called Ospho. It's basically phosphoric acid with a surfactant and a couple other additions, from what I understand.

I've read that zinc and phosphoric acid react to produce zinc phosphate and hydrogen gas.

My unknown is whether this hydrogen gas is emitted in great enough quantities to be dangerous / explosive when this reaction is carried out indoors. I don't know how much zinc is being reacted, but electroplating leaves an extremely thin coating and I'm talking about small quantities of fasteners.


texts: Is activation energy temperature-independent?

texts:
I know that activation energy for a reaction is the extra energy given to the reactants to reach the threshold energy so that they can collide and react. But then, why is it said that the activation energy does not depend on the temperature?

If the temperature is higher, the reactant molecules have a higher kinetic energy, and thus the energy difference between the threshold energy and the energy of the molecules will decrease, that is, the activation energy will decrease.


texts: How can I prepare a PBS (Phosphate Buffer Solution)? pH=7.4

texts: Phosphate-buffered saline (abbreviated PBS) is a buffer solution commonly used in biological research. It is a water-based salt solution containing disodium hydrogen phosphate, sodium chloride and, in some formulations, potassium chloride and potassium dihydrogen phosphate.


texts: In what solvents does ionic association occur?

texts:
When a ionic compound like $\ce{NaCl}$ dissolves, it doesn't always full dissociate due to ionic pairing. This is measured by the van 't Hoff factor. Now, this is what I'm looking at for my chem experiment - how does ionic pairing affect freezing point depression. With changing radius the ionic pairing should change, and hence the van 't Hoff factor and freezing point depression should vary. Is this a valid hypothesis?
If so, my main issue lies with what solvents does ionic pairing occur in? Does it occur in all 3 of polar protic, polar aprotic and non polar solvents? I'm having trouble deciding which type of solvent to use. I was initially modelling water, but now I don't know how solvent type affects ionic association. Any help is appreciated. I'm not sure if ionic pairing occurs at all in all 3 types of solvents.


texts: Heating of mixture of gases with one gas barely above its boiling point

texts:
What happens when mixture of two gases is heated in a closed container?

If one gas expands faster than the other and increases pressure of the container enough so that the boiling point of the other gas is decreased below the gas temperature, will second gas start turning into liquid?

This phase change must also give out heat, causing the overall temperature and pressure to further increase.

Is this valid? or mixture of two gases work lot different than two of them separately?


texts:
Gas expands through an adiabatic turbine.  The inlet stream flows at 100 bar and 600 K, while the outlet stream is at 20 bar and 445 K. The constant-pressure molar heat capacity of the gas is $30.0 + 0.02T$, where the molar heat capacity is in J/(mol K) and the temperature is in K.  The process is at steady state.

Assume the gas is non-ideal and follows the following equation:

$$p=\frac{RT}{V_\mathrm m-b}+\frac{ap^2}{T\left(V_\mathrm m-b\right)}\tag{1}$$

with $\displaystyle a=0.001\ \frac{\mathrm{m^3\ K}}{\mathrm{bar\ mol}}$

and $\displaystyle b=0.00008\ \frac{\mathrm{m^3}}{\mathrm{mol}}$

For this gas the differential molar enthalpy change is:

$$\mathrm dH_\mathrm m=C_{\mathrm m,p}\mathrm dT+\left[V_\mathrm m-T\left(\frac{\partial V_\mathrm m}{\partial T}\right)_p\right]\mathrm dp\tag{2}$$

Assume that the ideal expression for the molar heat capacity given is still valid, but that it is only true as $p$ goes to 0.

And the question is; what is the shaft work of the turbine?

This question is from a thermodynamics course and to solve it students were sort of guided through a solution.
First substitute equation (1) into equation (2) and find a general expression for the differential molar enthalpy change of the non-ideal gas.
Then draw a $pT$ diagram of an appropriate path to evaluate the enthalpy change of the process, and just integrate along the path to find the answer.

I still can't figure out how this was supposed to be done.

Thanks to anyone who bothered to read/think about this problem as it is kind of long.


texts: How do quaternary ammonium salts catalyse SN2 reactions?

texts:
I am asked to identify the "best catalyst" for the reaction:

$$\ce{CH3(CH2)8CH2Br->[\ce{KCN}][\text{benzene}]CH3(CH2)8CH2CN}$$

The options are (A) benzyl chloride (B) aniline (C) N,N,N-trimethylbenzylamine chloride, and (D) N-phenylethanamide.

Now, at first, I immediately thought that the catalyst chosen may have to prevent a possible ring formation, given there are already ten carbon atoms. However, I am not sure how any of those catalysts help prevent that (I doubt if a ring would even form though, because there isn't any nucleophile, but those ten carbons look suspicious!)

Anyway, I realized that this catalyst may have to be polar aprotic for the given SN2 to occur. But, all of the given catalysts are pretty protic (resonance delocalisation of the benzyl carbanion with the ring) I would rank them on proticity as (D) > (C) > (B) > (A).

Hence, although all are protic, I may make a vague guess that (A) is the least protic and hence the answer. However, the answer given is (C) and the solution instead states that:

  Solvation of nucleophile is very less in presence of quaternary ammonium salt.

So, how? Where did the part about acidity go? And why worry about solvation? There doesn't appear to be any factor related to it at all (I read from here). Even so, how exactly would quaternary ammonium salts be poorer "solvators" than the others, say option (A)? Can I even predict this theoretically?

Source: MS Chouhan; Advanced Problems In Organic Chemistry; 11th ed; Q11 in Amines


texts: What does "reaction coordinate" mean? What does it mean when a reaction has TWO reaction coordinates?

texts:
I'm familiar with the concept of a reaction coordinate from high school chemistry as some generic conformational parameter that all of the intermediate states of a chemical reaction lie upon. Recently, though, I've seen some presentations where chemists presented plots of the free energy with respect to two reaction coordinates, and my understanding is that the plot was of a measurement (I could be wrong, though).

What exactly does the reaction coordinate mean? What does it mean to have more than one reaction coordinate for the same reaction? Is the free energy as a function of the reaction coordinate a measurable quantity?


texts: Why is aluminium(III) considered a hard acid if it forms covalently bonded compounds like aluminium oxide?

texts: If something is a hard acid, it tends to form ionic bonds as it is polarizing. So why is the aluminium ion a hard acid when it forms bonds with covalent character. A similar argument follows for why carbon dioxide is considered a hard acid?


texts: Is it okay for a sulfite ion to have 10 electrons around the sulfur?

texts:
Possible Duplicate:
  Can an atom have more than 8 valence electrons? If not, why is 8 the limit?

I was watching this youtube clip ( http://www.youtube.com/watch?v=XY1XLgHUAIQ ) in which a lewis diagram was drawn for a sulfite ion.

Sulfur ends up with four bonds as well as a lone pair of electrons. This gives sulfur 10 electrons. Isn't this too many?


texts: Reactivity of anhydride vs aldehyde with nucleophile

texts:
It is known that order of reactivity of carbonyl derivatives towards nucleophiles follow the order as:

  Acyl halide> acid anhydride>ester> amide> amide derivatives

(Source: "A Guidebook to Mechanism in Organic Chemistry" by Peter Sykes M.Sc., PhD., F.R.S.C., C.Chm. Fellow and Vice-Master, Christ’s College, Cambridge.)
(Here amide derivatives are NRR' only)

It is difficult to find out the order in books and online as well, if we also include aldehyde and ketones.

Well there is one such debated question on Chemistry Stackexchange, but the fact that anhydride is greater in reactivity than an aldehyde confused me as  why is the acid anhydride's direct conjugation (even though if it's cross conjugation) less effective in stabilising the positive charge on carbonyl than the aldehydes hyperconjugation?


texts: Why is the radius of hydrated Na+ greater than that of hydrated K+?

texts:
Although $\ce{Na+}$ has ionic radius of 95 pm and an atomic weight of 23, and $\ce{K+}$ has ionic radius of 133 pm and an atomic weight of 39, hydrated $\ce{Na+}$ is larger than hydrated $\ce{K+}$: This is evident from observing that $\ce{Na+}$ moves through a cell membrane with greater difficulty than $\ce{K+}.$

Why is hydrated $\ce{Na+}$ larger in size than hydrated $\ce{K+}?$


texts: Is delta S the same in reversible and irreversible processes?

texts: I've read that change in entropy of a system is the same for a system in reversible and irreversible processes since it is a state function and does not depend on the pathway. Does this only apply to the system since I understand change in entropy of the universe is always positive for irreversible processes?


texts:
Why is it that when you chop peanuts, a highly viscous paste is created?

Im assuming that the reason that chopped peanuts dont become just dust is because we cannot chop finely enough, but what causes the chopped particles to adhere to each other?


texts: Can acetic or citric acid be too highly concentrated when used for cleaning copper?

texts:
I intend to clean a copper surface with acetic or alternatively citric acid. There are many different concentrations recommended by different sources on the internet. For example vinegar with 10% acid content diluted once more at a ratio of 1:9 with water.
I'm under the impression that neither acetic or citric acid actually reacts with pure copper, only reacting with the oxidisation products on the surface (creating verdigris and so on).
Does the dilution then serve a purpose other than saving on vinegar? What could happen if I were to use undiluted 25%-acid (or even higher) vinegar concentrate, i.e. a 25% aqueous acetic acid solution directly? Basically, what could go wrong if the acid is too highly concentrated?


texts: Physical chemical property that determines redox potential?

texts:
Can someone explain (on an advanced level) what phys-chem property of compounds/elements determines what their half-cell redox potential will be? For example, Zn and Cu are structurally very similar and their ionization energies, electronegativities, etc. won't be all that different. So, why is the 2-electron redox potential for each so different? ie Zn is -0.76 V (SHE) and Cu is +0.34 V (SHE), which is a significant 1.1 V different.

Isn't electric potential the amount of "stored" energy? So, wouldn't removing or adding 2 electrons to Zn or Cu be very similar since they are next to each other on the periodic table?

Edit: I've added some sources and clarity to the discussion in the answer below.


texts: The effect of the voltage at the Downs cell

texts:
I referred the Wikipedia and Advance Chemistry by Philip Matthews, for having a much comprehension on the down cell, but there was a opposition while reading the both references.

Wikipedia states that,

  Although theory predicts that a potential of a little over 4 volts
  should be sufficient to cause the reaction to go forward, in practice
  potentials of up to 8 volts are used. This is done in order to achieve
  useful current densities in the electrolyte despite its inherent
  electrical resistance. The overvoltage and consequent resistive
  heating contributes to the heat required to keep the electrolyte in a
  liquid state.

But the Advance Chemistry book by Philip Matthews (page 521) states that,

  A large current is passed through the cell, but at a low voltage.
  This has the effect of both discharging the sodium effectively and
  heating the mixture so that it does not crystallize

The both references have a opposition at the fact of amount of voltage to heat generating.

Which one is correct? Also I hope an answer with the reasons of how does the voltage affect on downs cell, with the heat generating.  Thanks


texts: Deprotection of Boc using TAF to obtained free amine group

texts:
I know Boc can easily be deprotected using strong acid like TFA and HCl, but final product is salt of TFA or HCl, my question is that, how we can avoid formation of slat and obtained free amine group.

The proposed mechanism is


texts: Do electrons in covalent bonds always obey the octet rule?

texts: Do electrons in covalent bonds always necessarily obey the octet rule? Always?


texts: How does the ambient temperature affect the rate of redox reactions in a salt lake?

texts:
Many years ago, I used to work as a gold exploration geologist.  One of the main locations was a salt lake in Western Australia detailed in the document WMC Resources Exploration Successes inN Lake Terrains - Applications of Element Dispersion, Kambalda W.A (Carey and Dusci, 1993).

In the article, and in my research at the time, it is stated that

  gold disperses laterally along iron redox fronts that tend to occur higher in the regolith profile

Now the area is arid (up to 50C or 122F in summer), but was not always like this, fossil records suggest far milder conditions occurred in the past.

My question is, how does the ambient temperature affect the rate of redox reaction in a salt lake, such as in the example provided?


texts: Implementing the projected atomic orbital (PAO) localization in Gaussian

texts:
I am currently attempting to learn how to setup the active space for performing CASSCF calculations.

The textbook I am using as a reference is:

Roos, Björn O. "Multiconfigurational quantum chemistry." Theory and Applications of Computational Chemistry. 2005. 725-764.

My specific problem is discussed in Section 13.1.1. I am working with Gaussian 2016.

I would like to generate a checkpoint file with orbitals localized as atomic orbitals in order to use them as a starting point when selecting my active space.
What I mean is the following...

I am working with BODIPY, with 11 active orbitals (the PI framework).

From a normal SCF I obtain the typical MOs, these would be three of my active orbitals:

If I include the option Pop=SaveNBOs, I obtain localized Natural Bonding Orbitals. These would be three of my NBO active orbitals:

I have found that I can use IOp 4/9 to control the localization method to some extent (for example, "IOp(4/9=20212)" implements the Pipek-Mezey localization). However, after searching for a while, I still don't see how to generate the localized atomic orbitals. Could any of you suggest how to achieve this? I would then be working with the 11 pz orbitals as my active space.

Thanks!


texts: Preparation of sulfonyl chlorydes and mechanism of preparation of tosyl chloride

texts:
After searching about the preparation of sulfonyl chlorides, I couldn't find much. I found that for preparation of tosyl chloride, chlorosulfonic acid can be used, as in:

Can chlorosulfonic acid be used to prepare sulfonyl chlorides in general? What are some other ways to prepare sulfonyl chlorides? If there is any.

The other part of the question, I'd like to know how the mechanism of this reaction would work. Having the equilibrium of the reaction:

$$\ce{3 ClSO2(OH) <=> SO2Cl+ + 2 SO3Cl- + H3O+}$$

How exactly is the $\ce{SO2Cl}$ formed? I didn't quite understand how the $\ce{Cl}$ became a cation. Apparently the benzene attacks that cation in order to form the desired product.


texts: How to write the formula of a mixed metal salt?

texts:
I suppose the formula of the Sulphate salt of Sodium & Potassium is $\ce{KNaSO4}$ as the Pubchem site says so.
So, is there any rule that in the formulae such mixed metal salts we need to write the metals in the order of electropositivity?


texts: Is the 'central Tin atom' in crystalline tin oxide really offset like this?

texts:
Is the position of the central Tin atom as shown in the first figure ($\ce{SnO2}$) drawn offset towards the oxygen to the right for a reason? The oxygen also seems to reciprocate and move towards the tin. Usually the rutile structure is shown as symmetric with the metal the center. I'm showing a GIF alternating images of $\ce{SnO2}$ and $\ce{RuO2}$, with complete image source information following.

note: I'm interested to know about the locations of the atoms within a unit cell as determined by crystallographic information - not one's impression of the drawing. I'd like to know if the offset shown in the drawing is there to represent an actual asymmetry, or if it's just an error.

Figure 1. Tin Dioxide (Tin IV oxide), also found as Cassiterite, image from Rutile unit cell 3D balls.

Figure 2. Ruthenium(IV) oxide, image from Ruthenium(IV) oxide unit cell 3D vdW.

Figure 3. Rutile structure, image from Rutile structure

 Fig. 1

 Fig. 2

 Fig. 3


texts: Reducing agent in preparation of CpRuCl(PPh3)2

texts:
Synthesis of cyclopentadienyl-bis-triphenylphosphine-ruthenium chloride $\ce{RuCl(PPh3)2(\eta^5-C5H5)})$:

Dissolved $\ce{PPh3}$, $\ce{RuCl3.3H2O}$ and cyclopentadiene in ethanol and heated under reflux to prepare it.

What is the reducing agent and what is the product formed on oxidation of this reducing agent?

The ruthenium is being reduced but i don't know what is being oxidised.


texts: Why are hydrogen-bonded compounds (such as NH3) excellent solvents for most lab reagents?

texts: Hydrogen bonds are said to be one of the strongest molecular interactions in nature. Then why can most substances that interact through hydrogen bondig such as water and $\ce{NH3}$ able to dissolve a large variety of both ionic and covalent laboratory reagents? Does it have something to do with the structure of $\ce{NH3}$ or something else?


texts:
In this link

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch14/phase.php

It says (in the latter part ) that for all combinations of Pressure and Temperature along line BC

the rate of boiling of liquid to form a gas= the rate of condensation of gas to form a liquid.

And C is the Critical Point.  Similar thing has been said  for other lines also

Now 100℃ (or boiling point of the liquid) will lie somewhere on BC

So according to the link rate of boiling of water to form gas is the same as the rate of condensation of gas to form water.

But I have read that at boiling point all the liquid changes to gas or there is no equilibrium at that point.

So why then it says- the rate of boiling of liquid to form a gas= the rate of condensation of gas to form a liquid.

I am not good at chemistry so this might not be a good question. But I was trying to understand phase Diagrams for the first time !


texts: Where can I obtain tables of P-V-T/compression factor data?

texts:
Some recent research I'm dealing with has required me to look for tables of experimental pressure/volume/temperature values (equivalently, a table of compressibility/compression factors in terms of any two of pressure, volume, or temperature) for various substances. Thus far, I've managed to obtain compression factor tables for a short list of substances from Perry's Chemical Engineers' Handbook.

I am wondering, however, as to where I should be looking for more extensive tables (e.g. tables with finer sampling), as well as tables for substances that were not included in that handbook. What books/websites/journal articles should I be looking at?

My attempts at searching on the Internet have not been very fruitful; I would appreciate knowing what keywords should I be using with the usual search engines to get better results.


texts:
Can monosaccharides and disaccharides dissolve in liquid ammonia due to hydrogen bond formation?
My rationale is that these sugars may be able to form hydrogen bond with ammonia ($\ce{NH3}$).


texts: Why is para-aminobenzoic acid more acidic than ortho-aminobenzoic acid?

texts:
Compare the acidic strength of o-, m-, p-aminobenzoic acids.

I got that meta will be the most acidic as it won't be able to show R+ effect of $\ce{NH2}.$
But among the other two, i.e. ortho and para, shouldn't ortho be more acidic as it will cause ortho effect?
But according to my book and the data I found online:
$$
\begin{array}{lc}
\hline
\text{Compound} & \mathrm{p}K_\mathrm{a}\text{(amino)} \\
\hline
\textit{o}\text{-Aminobenzoic acid} & 4.89 \\
\textit{m}\text{-Aminobenzoic acid} & 4.79 \\
\textit{p}\text{-Aminobenzoic acid} & 4.77 \\
\hline
\end{array}
$$


texts: Why does phenol react on oxygen in the Gattermann–Koch reaction?

texts:
When discussing the Gattermann–Koch reaction on phenol substrates, it has been said that O-acylation is a problematic competing reaction as

  in a phenol, there's high electron density on the O atom [...]

However, there are also numerous other reactions where phenol reacts with electrophiles on the benzene ring. Some examples are:

the Houben–Hoesch synthesis (a kind of FC acylation);
the Riemer–Tiemann reaction;
the reaction of phenol with nitrous acid to form 4-nitrosophenol;
the Kolbe–Schmitt reaction; and
the Vilsmeier reaction, amongst others.

Why is the Gatterman–Koch reaction an exception?


texts:
I was just in my AP Chemistry class earlier today learning about hydrates and their properties. It occurred to me that a compound with so much water could aid in moisturizing the skin. Is this a valid thought? And if so, could hydrates be irritating to the skin?

Through research, I personally thought Natron may be an option in a solution added to a cream or lotion.


texts: Is enthalpy the same thing as potential energy?

texts:
From what I know in a closed system the potential energy + the kinetic energy is constant since no external work is done on the system. In my textbook it says that enthalpy is equal to the sum of the KE + PE meaning total energy. My question is how can the energy be lost to the environment after the collision of two particles. Since as the particle approach each other KE is turned into PE until activated complex is reached. Once it is reached they break up into smaller particles, repel each other and convert the PE back to KE. In conclusion all energy in the system is constant and no energy is lost. I don't quite understand why we have Enthalpy vs Time graphs. Since the energy in the system was never changed it simply converted between forms. For my homework when I pretended that enthalpy was simply PE and that endothermic = increase in PE and exothermic = decrease in PE I usually got it corrected(Such as question below). Is it not true that if you decrease PE by a amount KE would increase by that amount hence no change?

For instance a question from my homework "After a reaction, the product have less KE than original reactant molecules. Is the reaction endothermic or exothermic?"

Im thinking to myself that if KE has decreased PE must increase hence no change in energy so neither endothermic or exothermic. But the answer is endothermic.

In conclusion my main question is can I ignore the definition the textbook gave me and define enthalpy as total PE and delta enthalpy = change in PE rather than total energy.


texts: I'm creating a program, which predicts reactions of compound. So, I need a database of chemical reactions. And I need both inorganic and organic reactions. But I can't use Scifinder or Reaxys because they are not free. Is there any free analogs?


texts: Bond angle in water vs in oxygen difluoride

texts:
My teacher taught that bond angle $\ce{H-O-H}$ is larger than $\ce{F-O-F}$ due to less repulsion in the latter's bond pairs.
I know that bond angle $\ce{H-O-H}$ is $104.5^\circ$, but I'm confused with that of $\ce{F-O-F}$ because variable angles are given in articles on websites and in books. Some are $109.47^\circ$, $101.55^\circ$, $103.1^\circ$.

I want to know which bond angle is greater and why?


texts: Synthesis of Diazepam with (2-amino-5-chlorophenyl)(phenyl)methanone

texts:
I tried to draw the mechanism of the diazepam synthesis.
Question: Do I really get the tertiary amine or does dimethyl sulfate methylate the amine twice?


texts: What results from combining monopotassium phosphate, magnesium sulfate and calcium nitrate?

texts:
If I mix monopotassium phosphate, magnesium sulfate, and calcium nitrate together in aqueous solution, what chemicals will result?

Are these safe to combine (i.e. any toxic gases, etc.)?

I thought this answer about just magnesium sulfate and calcium nitrate was insightful.


texts: Can we process waste just by decomposing it to homogenous mass and extracting the elements from it?

texts:
I. e., what if we just burn trash completely or dissolve it in acid, get the resulting paste and extract pure chemical elements out of it by applying some physics and/or chemistry to it until no more can be extracted? Just curious.

EDIT

To be perfectly clear: my main concern is whether there are any means to extract any useful element from this bulk of burned/dissolved/blender-ed trash. For example, we burn with Thermite the whole contents of some waste disposal site, until it's only multicolored ash there. Or pour the HSbF6 over it. From there, can we get the pure carbon out of the resulting mass? Pure aluminium? Pure iron? Gases, maybe, like oxygen?


texts: Is it possible to calculate electronegativity of surface atoms?

texts:
As the title asks, is it possible to calculate the electronegativity (EN) of specific atoms on extended surfaces (slabs), more specifically using computational methods? There are a few issues here I am running into:

To find the Mulliken EN $\chi$, we can use the relation

$$\chi = \frac{E_\mathrm{i} + E_\mathrm{ea}}{2}$$

where $E_\mathrm{i} = E(\ce{M+}) - E(\ce{M})$ and $E_\mathrm{ea} = E(\ce{M})-E(\ce{M-})$. However, these energies are for the entire system, usually a molecule, and not the individual atoms. I hope I am not misunderstanding the concept here.

Alternatively certain definitions use $\chi = -\mu$, or the work function. Again, this is usually calculated on a surface basis, not per atom of site.

Is there no accurate determination method which is specific to the atom? Or is it conceptually impossible?


texts: Why are metal oxides generally more stable than their corresponding elemental forms?

texts:
Why is the oxidation of certain metals such as iron favorable from a thermodynamic standpoint? What is it about these metal oxides that makes them inherently more thermodynamically stable than their starting, elemental forms? The only reason I can imagine is that iron, being a d-block element, has a low electronegativity and cannot stabilize valence electron density as well as oxygen, the second most electronegative element on the table.

Also, is oxidation always thermodynamically favorable?


texts: How does strong acids conduct electricity in water?

texts:
How do strong acids conduct electricity in water?
I have just studied ionization of water and I'm confused about some points.
First: I know that water ionizes  in a very small amount ($10^{-14}$) so it doesn't conduct electricity and if we add strong acid (or base) to it , it becomes a good conductor of electricity. My question here is how it conduct electricity although if a strong acid is in water its $\ce{H+}$ ions concentration  in water would range from $10^{-1}$ to $10^{-6}$ (which is avery small amount) to keep $K_w$ constant.
I'm confused so if you understood me please explain and tell me if I have something wrong


texts:
First the backstory:
We've begun growing mushrooms (currently Enoki, Lion's Mane and Blue Oysters if anyone is curious) for the sake of eating and maybe potentially selling someday soon. My partner and I have a combined diplomas and degrees in Biotechnology, so we know about all the rigors of keeping things clean and contamination free, figured it was time to try our hand at what we've learned and see how well we can do it.
Anyways I got to thinking, what if I grew them in a more oxygen rich environment? I've made the assumption that, like the dinosaurs, an oxygen-rich environment would allow the fungi to grow larger than they would without extra oxygen.
Here's the idea:
At a job I used to work at, we would sequester CO2 in about 0.5M NaOH in order to measure methane gas composition percentages in digesters. The gas was composed of mostly CO2 and CH4. By sequestering one, we can roughly calculate the other. For volumes we'd use about half of the volume of gas in 0.5M NaOH to sequester (not sure if that volume/concentration is the most effective). Shake the solution in the gas and equalize the gas to find out your CH4 percentage.
I'm wondering if I could build, in the most basic sense, a vacuum with an internal NaOH atomizer that pulls outside air through, sequesters the CO2 in liquid, and allows higher concentrations of oxygen to pass into the grow room. As for actually capturing and storing the CO2, I'm thinking I could pass the NaOH through activated biochar and reuse the NaOH or maybe there's a way to precipitate the CO2?
I understand the materials required all need to be compatible with NaOH, especially the atomizer, so it's a bit of a pipe dream. But have I just thought up an effective way to sequester CO2? My minds racing that this may actually be a good idea!
Open to all suggestions and recommendations. I'm not flying forward with this idea at all, so don't worry about me dunking an atomizer in a  bath of NaOH (which no one should !EVER! do unless in an incredibly well-ventilated area, and the equipment is compatible).
First time using this site, hopefully this wasn't too long winded, apologies if I've taken up your lunch break.


texts: Recovery and Disposal of Unknown Copper Compound

texts:
About a month ago, I ran a small electrolysis experiment in an old fish bowl with a $\ce{MgSO4}$ electrolyte and copper electrodes. It ran for about 3-4 hours.

Now, a month later, I am left with about 40% of the initial volume of water and a blue copper compound on the bottom of the bowl. I believe this is $\ce{Cu(OH)2}$. I've provided a picture.

This has been sitting outside for the entire month under a little greenhouse type thing (but air can still get at it). As winter is coming, I was hoping to collect what I've formed and dispose of it properly. So

1) Could it be $\ce{Cu(OH)2}$?

2) Is there a way I can get the solids out? Or should I just pour everything into a plastic container for disposal?


texts: Stereochemistry of C as non-chiral centre

texts:
When a C of a molecule is not a chiral centre, the spatial orientation of its substituent group doesn't affect its stereochemical specification, does it?

Ex:


texts:
In the benzoate ion, does the carboxylate group show a $-I$ or a $+I$ effect?

I learnt that the carboxylate group is a $-I$ group, but according to a website the carboxylate group in benzoate shows a $+I$ effect.

So, which one is correct? Does the carboxylate group show a positive or a negative inductive effect?

Please neglect mesomeric effect when answering.


texts: Impossible pH For Aqueous Weak Acid Solution

texts:
An aqueous solution of $\ce{HCl}$ has a $\mathrm{pH}$ of $0.00$ if $[\ce{H+}] = 1.00 \; \mathrm{M}$. I tried to see if an aqueous solution of acetic acid could have a $\mathrm{pH}$ of $0.00$, given that its $K_a$ value is $1.8 \times 10^{-5}$. I tried finding the concentration $[\ce{H+}]$ of such a solution using

$$K_\mathrm{a} = \frac{[\ce{H+}][\ce{C2H3O2^-}]}{[\ce{HC2H3O2}]}$$

and then using molar mass and density conversions to determine whether such an aqueous solution exists.

Does it make sense to say that such a solution does not exist if the amount of substance of acetic acid in 1 liter of solution actually take up more than 1 liter of volume?


texts:
Molecular orbital diagrams are well known by chemists.
According to Wikipedia (emphasis mine),

  A molecular orbital diagram, or MO diagram, is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the linear combination of atomic orbitals (LCAO) molecular orbital method in particular.

An example is given below.

(Image by CCoil (talk) - own work, CC BY-SA 3.0, Link)

By the use of computational chemistry methodologies we can (1.) produce a molecular wavefunction of a diatomic molecule as a linear combination of basis functions (assume they are centred on each nuclei).
This would already satisfy the definition above and generate a suitable MO diagram.

On the other hand, there are special methodologies for obtaining the starting orbitals centred on atoms:

We could express molecular orbitals as a linear combination of optimised atomic orbitals of each atom, which would imply an extra calculation for each element in a molecule.
A change of basis for the MOs, from the basis set to the atomic orbitals, does the rest.
The natural bonding orbitals (NBOs) method allows one to produce natural atomic orbitals as well, which could also be used as initial orbitals centred on the atoms.

So my question is:

Are the three approaches above really arbitrary?
What makes one option better than the other?


texts: Why do research papers mention experimental details in such detail?

texts:
The paper Analysis of cyclic pyrolysis products formed from amino acid monomer has the following to say in it's experimental section:

Glycine, phenylalanine, tyrosine, tryptophan, serine, and valine were purchased from Daejung Chemicals & Metals Co. (Korea). Arginine, aspartic acid, glutamic acid, and proline were purchased from Samchun Pure Chemical Co. (Korea). Alanine, asparagine, glu- tamine, histidine, leucine, and threonine were purchased from Junsei Chemical Co. (Japan). Isoleucine and lysine were purchased from Acros Organics (USA), and cysteine was purchased from Merck Co. (Germany). Methionine was purchased from Yakuri Pure Chemicals Co. (Japan). Fumed silica was purchased from Merck Co. (Germany).
...
Pyrolysis–GC/MS was conducted with a CDS Pyroprobe 1500 heated filament pyrolyzer (Chemical Data System, Oxford, USA) coupled to an Agilent 6890 gas chromatograph equipped with a 5973 mass spectrometer of Agilent Technology Inc. (USA)

Why is there so much emphasis on the sources and country of origin of chemicals/instruments in these sections? This behaviour is not restricted to this paper; several other papers go into similar levels of detail regarding their procedures.


texts: What is the mechanism for the oxidation of benzene to maleic anhydride using vanadium pentoxide?

texts: What is the mechanism for the oxidation of benzene to maleic anhydride using vanadium pentoxide, $\ce{V2O5}$?


texts: Finding reaction rate from pressure change

texts:
I conducted a lab in which different concentrations of $\ce{HCl}$ were used and $\ce{Na2CO3}$ was added. The pressure change was measured for a reaction with the different concentrations.

Now I am going to find the reaction rate for the reactions. I am thinking that using the pressure data, I can find the reaction rate by doing the following.

Consider:

${PV = nRT}$ ($R$ and $T$ are constant so they can be taken out of the equation)

${PV = n}$

$P = {\frac nV}$ (Knowing that $\text{c}={\frac nV}$)

${P} = \text{c}$

Seeing as pressure is directly related to concentration, then couldn't I just use the pressure data to find the rate and then relate that to the concentration change over time?

The alternative would be to use ${PV=nRT}$ for each second of the reaction and find the concentration change that way. However, I want to consider the possibility of doing it this way.

One problem I forecast would be the units: kPa/s vs. mols/L


texts: The carbon-13 NMR for 1,1,1-trichloroethane

texts:
I was working the following spectroscopy problem from Clayden 2e that asks us to identify the structure of a compound from information about its carbon-13 NMR peaks.

  Problem 3.5: The solvent formerly used in some correcting fluids is a single compound $\ce{C2H3Cl3}$, having 13C NMR peaks at 45.1 and 95.0 ppm. What is its structure? How would you confirm it spectroscopically?

I initially thought that the structure would be 1,1,1-trichloroethane (shown below) since there will be two different carbon chemical shifts: one bonded to three $\ce{H}$ atoms and one $\ce{C}$ atom in the 0-50ppm region (corresponding to the 45.1 ppm peak) and another peak for a carbon bonded to three $\ce{Cl}$ atoms in the 50-100ppm region (corresponding to the 95.0ppm peak).

Although it considers 1,1,1-trichloroethane, the solutions manual to the book concludes that the correct structure is 1,1,2-trichloroethane (shown below), the other possible structure with formula $\ce{C2H3Cl3}$.

However, this compound would have both peaks close to eachother in the 50-100ppm range.

Wouldn't the correct molecule be 1,1,1-trichloroethane, and wouldn't the solutions manual be incorrect? The NMR specs below that I found online corroborate my thinking.

References

Clayden, J., Greeves, N., Warren, S. Organic chemistry, 2nd ed.; Oxford University Press: New York, 2012.

https://www.chemicalbook.com/SpectrumEN_71-55-6_13CNMR.htm

https://spectrabase.com/spectrum/5WUteTf4M4u


texts: What does the "D" group represent on a chiral center?

texts: I am trying to figure out the configuration for this chiral carbon to answer a homework question, however they arbitrarily include a "D" group as shown in the image. My guess is that it is some higher priority group than the carbon, and lower priority than the halide, making the configuration (S). Is this correct? What does the D group represent?


texts: What eco-friendly substance can I use to write and erase on a wall for UV glowing without detection in daylight?

texts:
I rent an office and want an alternative to a whiteboard and continual dry-erase marker purchases.

I can shut out the light and use the surface under UV lamps only, that's fine.

Commonly listed organic glowing elements are blood, urine and semen. None of which, I think would be untraceable by eyes (or nose) during the day!

The surface I would like to use contains typical white interior paint, applied last year.


texts:
From Chemguide:

That means that the only elements to form positive ions with noble gas structures (apart from odd ones like scandium) are those in groups 1 and 2 of the Periodic Table and aluminium in group 3 (boron in group 3 doesn't form ions).
Negative ions are tidier! Those elements in Groups 5, 6 and 7 which form simple negative ions all have noble gas structures.

Does it mean that generally negative ions are luckier in achieving the noble gas form? Is there any trend behind this, or is it just a coincidence?
Why did he chose those particular three groups as an example? There are negative ions formed by elements in other groups too.


texts:
I don't think that cyclohexenone should have any resonance forms. Moving the double bond around would necessitate moving hydrogens around as well. For example, I know that benzene exhibits resonance (duh) and the second picture attached shows the pi bonding electrons shifting but doesn't show any hydrogens shifting positions.

That being said, is there a easier way to determine if a resonance form of a cyclic compound is valid? Drawing out each individual atom and bond is time-consuming! Should I use Huckel's rule? Do all cyclic compounds which exhibit resonance follow Huckel's rule?


texts: What is the pH of a solution that results of a mixture of two others with known pH?

texts:
Solution A has a pH of 1, soultion B has a pH of 6. If I mix the same volume V of each solution into one, what will be the pH of the resulting solution?

I'm guessing here as no more information has been provided: It is a mixture of a strong acid with a weaker acid. So I'm assuming that the final concentration of protons will be related with the equilibrium displacement of the weaker acid's dissociation. The full dissociation of the stronger acid forces the equilibrium of the dissociation of the weaker to be displaced to the left, as in there will be no proton contribution from the weak acid. So the pH of the resulting solution will be computed from the concentration of protons from solution A being diluted in the new volume, 2V.

Am I in the right direction? I feel that calculating the raw amount of protons contributed by each solution and then computing the new concentration will be too obvious for a method.

Anything that would guide me into this pondering will be very much appreciated.


texts:
Imagine you fill a tank with undecayed neutrons and water .Now neutrons will decay into proton and electrons. Assume that the wall of the container is so thick that it doesn't allow the protons to pass while allow beta rays to pass. The water will now have h + ions and they will make h3o + ions in water that is water will become acidic. Will now
1. A metal having normal reactivity will give H2 gas
2. NAOH react with solution to give water


texts: Is there any publicly available software that can do deterministic CCSDTQP other than MRCC?

texts: MRCC can do arbitrary order coupled cluster but much of the code is computer-generated (not hand-coded by a human) so it can be slow. There are some stochastic codes for high-order coupled cluster, but as my question states, I am looking for a deterministic code that can be an alternative to MRCC.


texts: Br- and I- ions give layer test, but Cl- ion doesn't. Why?

texts: One of the questions I found in an NCERT book. Interestingly I could not find the answer anywhere on the internet. Hence, stack exchange.


texts: Are nucleophilic substitutions reversible?

texts:
When $\ce{OH-}$ interacts with a halogenoalkane, for instance $\ce{CH3CH2Cl}$, it acts as a nucleophile and undergoes $\mathrm{S_N2}$ mechanism, which results in the following reaction:

$$\ce{CH3CH2Cl + OH- -> CH3CH2OH + Cl-}$$

Since $\ce{Cl-}$ has a free pair of electrons, can it act as a nucleophile that will reverse the previous reaction?

$$\ce{CH3CH2OH + Cl- -> CH3CH2Cl + OH-}$$

Since an $\ce{OH}$ group is more electronegative than $\ce{Cl}$ group, the carbon atom to which it attaches would have a greater partial positive charge ($\delta+$), does this mean it's more prone to nucleophilic substitution?


texts: What happens to the attraction of glycerol to a positively charged acetate rod if water is added

texts:
I know that glycerol is more polar than water because it has stronger intermolecular forces and its also more viscous. If I were to add water to a glycerol solution, would the solution get less polar with weaker intermolecular forces? Also if I were to add water, would the solution be more attracted to a positively ...

I mean if I place a positively charged acetate rod next to the mixed solution of water and glycerol, would the solution get more attracted to the rod or less attracted or would there be no change?


texts:
Why are ionic reactions extremely fast,  as compared to other gaseous
  reactions?

The ionic reactions (precipitations, neutralizations etc.) are extremely fast (somewhere about $10^{12}$ times faster) than gas-phase reactions and other ordinary reactions in solutions (inversion, substitution etc). Why is this so?

My thoughts
One possible reason might be the relative freedom of steric orientation in case of simple ionic reactions as compared to organic reactions and complicated gas reactions, but this isn't the case with simple gas reactions or formation and dissociation of ionic complexes, which do require specific steric orientations. The activation energy could be very low for ionic reactions, if this is so, then what is the reason behind it?


texts: Is there any difference between de-Broglie wavelength and the wavelength of normal waves?

texts:
Is de-Broglie wavelength different from wavelength of waves such as electromagnetic waves?

If yes, they differ in what respect?

And can we use the formula of wavelength of light ($c=v\lambda$) to calculate the de-Broglie wavelength?


texts: Does the Battery Bounce Test actually work?

texts: I heard that a good way to test if a battery is dead or alive is to see if it bounces. Supposedly, dead batteries bounce higher than living ones. Can someone tell me if this is a legitimate claim, and if it is, an explanation would be nice.


texts: I understand that Hydrogen Peroxide decomposes into oxygen and water over time. But why exactly does it do this? Could someone give me an explanation down to the molecular level as to why and how this happens. And also, why does MnO2 catalyse this.


texts: How do I determine the temperature at which a dissolved substance evaporates?

texts: I would like to understand the temperature at which a substance will vaporize when dissolved in a liquid. I have researched this online for hours, but haven't found a conclusive answer. Is it the boiling point of the dissolved substance? I'm attempting to find the temperature at which caffeine vaporizes when dissolved in water or other vegetable glycerin. Many thanks for your help.


texts: Why is the melting point of hydrogen iodide larger than that of hydrogen fluoride?

texts:
Compare the melting points of hydrogen fluoride (HF) and hydrogen iodide (HI).

I know the following things:

$\ce{HF}$ melts at $189.6~\mathrm{K}$ and $\ce{HI}$ at $222.35~\mathrm{K}$.
There are a lot of factors that have to be considered while comparing melting point, i.e., lattice enthalpy, packing fraction, intermolecular forces.
Generally, compounds that show hydrogen bonding show it in the solid and liquid phases because in the gaseous phase the molecules have enough energy to break the electrostatic interactions of hydrogen bonding.
So, HF shows hydrogen bonding in solid state. In fact, it even shows hydrogen bonding in gaseous state, though its not relevant here.
As molecular mass increases, van der Waals interactions between molecules also increase. If we only consider this factor, then melting point of HI must be definitely higher.
The strength of hydrogen bonding of HF is so much that the boiling point of $\ce{HF}>\ce{HI}$ although boiling point of $\ce{SbH3}>\ce{NH3}$, i.e. the hydrogen bonding dominates the van der Waals interactions in HI molecules because of their high molecular mass.
It's the combined effect of all the factors that determine the melting point of a substance.
Lattice energy is inversely related to the internuclear distance, it is also inversely proportional to the size of the ions. So, I expect HF to have more lattice energy.

Every factor that I can think of is in favour of HF except molecular mass. But if molecular mass of iodine is the reason that melting point of HI is higher, than boiling point of HI must have also been higher. Then why is the melting point of HI higher than that of HF?

Why is this contradiction?

Do let me know if I am wrong in the above mentioned facts or if I have any gaps in my understanding of the above points.


texts: Confusion about the SN1 and SN2 Mechanism

texts:
My book says, and I understand, that the $\mathrm{S_N1}$ mechanism is much faster for tertiary alkyl halides than primary. And the opposite for $\mathrm{S_N2}.$ This all makes sense. What I don't get is the conclusion it comes to next: hence, we predict that the primary alkyl halides will react primarily via $\mathrm{S_N2},$ and the tertiary via $\mathrm{S_N1}.$

The reason I get confused here is that nothing was said about the comparative rates for a primary alkyl halide via the $\mathrm{S_N1}$ or $\mathrm{S_N2}$ (they just compared primary and tertiary for $\mathrm{S_N1}$ and $\mathrm{S_N2}$). In my mind, which mechanism dominates for primary or tertiary should be dependent on the relative rates for that compound; not rates compared between primary and tertiary.

Is my argument sound? And if so, is there some literature you know of that explains this in such a manner?


texts: Among HClO4 and HClO2 which is the stronger acid if we do not know Ka values?

texts: I have two acids: $\ce{HClO4}$ and $\ce{HClO2}$ how do I determine which is the strongest acid without knowing $K_a$? The two hydrogens are bound both to an oxygen so there isn't anything to differentiate them, how can I  proceed?


texts: What happens with the boiling point of a liquid in a vacuum

texts:
This may be a silly question, but when I was reading my chemistry textbook, there was this following statement:

  "A liquid boils when its vapor pressure equals the external pressure acting on the liquid
  surface. At this point, bubbles of vapor form within the liquid. The temperature at
  which a given liquid boils increases with increasing external pressure."

But what would happen if that liquid was sealed in a vacuum, or at least submitted to very low pressure? Would the boiling point be a lot lower?


texts: What's the relation between the octet rule and quantum exclusion and how is it related to oxidation state?

texts: What in the quantum nature of electrons gives rise to the octet rule? How is it related to the fact that an element cannot have an oxidation state higher/lower than the complementary to 8?


texts:
My textbook, Solid-State Physics, Fluidics, and Analytical Techniques in Micro- and Nanotechnology, by Madou, says the following:

  X-ray analysis reveals the symmetries of crystals (lattice type), distances between atomic planes (lattice parameter), the positions of atoms in crystals, the types of atoms from the intensities of diffracted x-rays, and the degree of crystallinity (ordering).

I found this quite fascinating. Do we really have technology with the resolution to distinguish between layers of single atoms of materials? In other words, we can tell when one layer of single atoms ends and the next layer of single atoms begins, and analyse them as such?


texts: How do I solve oxidation numbers for unknown elements?

texts:
I am doing very well with oxidation numbers but I have a few problems. I know all the rules but when I get an element where I can't use any of the constant oxidation numbers what do I do?
For example: $\ce{HCNS,Ag2S,Bi2S3,KSCN}$ etc. ?


texts: What is the best way to strip ammonia from water at a mining site?

texts: Working at a mine and have excess ammonia in the water. Was going to run the water through an ammonia wood chip bio filter, was wondering if this is the best technique or should I approach it from a different way?


texts: How does polydimethylsiloxane stick to glass?

texts:
Polydimethylsiloxane (PDMS) is the main ingredient in Rain-X, a treatment that adheres to windshields.

How does PDMS adhere to class? It can't form covalent Si-O bonds with glass, according to one source. Makes sense, as the Si is already coordinated with four groups in PDMS and none of them seem to be easily removable.

A similar windshield treatment chemical, FAS17, was noted by the same source as being able to form covalent bonds with glass in the presence of an acid to cleave the ether linkages.

The source, however, didn't detail how exactly PDMS would adhere to glass. So what major forces would be involved in the adhesion of PDMS to glass?

Source:

http://hydrophobicsam.blogspot.com/2012/04/science-of-self-assembling-monolayers.html


texts:
A long time ago, when I used to make plastic models with glue, I never wore white gloves when gluing together the pieces, so I often got a lot of superglue on my hands. The superglue, which was very viscous and liquid, dried on my hands and later created small flakes in the process of coming off my skin.

At the time the back of the superglue container were listed instructions that read “in case of contact with skin, rinse with warm water until the glue is completely removed” or something similar.

My questions are

Is it okay to have ever had glue on my skin? Will it not create a lasting problem?
Is it okay that the flakes could have been spread on the bathroom towel when I wiped my hands, on the bedsheets, my clothes, the surface of the desk, the floor, and in other areas in the home?

I'm worried that the dust could have remained or been absorbed through the mouth, eyes or even nose (inhaled)?

*by glue I mean the type of glue that can be found on this link:

https://www.amazon.com/Tamiya-87038-Extra-Cement-Plastic/dp/B01F1S4N8U


texts: How to find the band gap for a compound?

texts: I have processed a si/polymer hybrid using a silane coupling agent which I need to determine the energy gap / band gap.  Would you please let me know the procedure to go about determining the band gap?


texts: Why does K2ZnO2 + H2SO4 yield K2SO4 + ZnSO4?

texts:
$\ce{K2ZnO2 + 2H2SO4->ZnSO4 + K2SO4 + 2H2O}$

How does the ZnO2 ion disassemble here? Does it perform as a basic oxide, since we know that a basic oxide + an acid --> a salt + H2O?

I'm not sure, because a basic oxide does not carry a charge, and usually sports only a single oxygen atom.

When trying to write down this reaction on my own, I wrote it as

$\ce{K2ZnO2 + 2H2SO4->H2ZnO2 + K2SO4}$

It was a surprise for me when I looked up the answer.


texts: How can I determine the chemical composition of local rocks and minerals?

texts:
Specifically I live in the U.S. so I'm asking about an ordinary rock that you might find in your backyard or near a playground. Humans have discovered gun powder, petroleum, silica, iron, and many more types of useful materials by observing and experimenting with materials which lead to said discoveries.

Sometimes I'm walking outside and think to myself how people largely just ignore stuff outside like the rocks, dirt, grass and things like that, but I think if you knew how to separate the chemicals in these materials, then it could possibly lead to discoveries that might have otherwise been overlooked.

Especially rocks, because they can be cracked open and looked at with a microscope. Can't these rocks be used as raw materials to engineer something? If so, shouldn't they have inherent value? If not, why? If so, how?

What are the typical chemical elements that you will find in these types of materials, and how can you observe the chemical compositions by either isolating them or via some other physical process?


texts: Hydrolysis of 4-chloro-3,3-dimethylbut-1-ene forms which products much faster than primary alkyl halides?

texts:
Question

My Attempt

First a primary carbocation is formed and then methyl shift occurs to form a more stable secondary carbocation hence making (C) the major product, consequently I also arrived at answer (D) via hydride shift, and also option (A) would anyway be a possible product.

But the answer given is (B). Where am I going wrong?


texts: Correct representation of Lewis structure for sulphate ion

texts: sulphate ion has tetrahedral geometry as predicted by VSEPR theory; the four S-O bonds are indistinguishable and have the same bond order, so the Lewis structure is better represented avoiding S=O double bonds; if instead of double bonds there are covalent dative bonds, what about the hybridization of S and O ? My idea is the following: Sulphur has hybridization sp3, each oxigen atom involved in dative bond has to provide an unfilled p orbital


texts: When one say that the electron goes from 1 orbit , say 2S, to another (higher) orbital, say 5P, it mean that the electron is excited to that orbit by some mean. In doing so it also it will also cross the nodes of 2P etc. But doing so does the electron actually cross the node or what? Cause doing so the, there is probability, although very less, of finding electron in node for a very short time.


texts: Why is difluoride a stronger oxidizing agent than dichloride?

texts: I am preparing for a chemistry olympiad and I am stuck with the question that why $\ce{F_{2}}$ is stronger oxidizing agent than $\ce{Cl_{2}}$.


texts: What tools can be used to estimate binding energies?

texts: I want to estimate the binding energies of various molecules. What are the analytical and numerical tools I can use for this purpose? In particular I'm interested in bonding energies of dyes to substrates (example).


texts: Density of saturated n-octane in air at 300 K?

texts: I am trying to calculate (if possible) the gas density of air saturated with n-octane at 300 K. Any suggestion of how to do this, or better, where I can look up the data?


texts: Are there gases that are not transparent at room temperature (i.e. at temperature below the point where the substance starts to radiate visible light due to heating)?


texts:
Do you pronounce the software's name, GAMESS, as ga-mess, gaim-z (as in plural of game) or something else.

I know it's sort of not the kind of question to ask here, but I couldn't think of anywhere else better.


texts: Experiment to show that air contains about 20% oxygen

texts:
I remember that in my primary classed I had an experiment in science to show air contains 20% oxygen. The experiment involved taking a trough of water, lighting a candle in the middle of the trough and inverting a glass jar over the candle so that air supply for the candle is cut of. When candle extinguishes, water level in the glass jar rises. I have seen this happen.

My question is why should the water raise in the jar, since burning of candle should produce an equivalent amount of carbon dioxide, so the molar amount of gas in jar is constant? Also the heat from the candle should expand the gasses in the jar, water level should go down I think.


texts: Why do statistical effects impact stepwise stability constants?

texts:
I have a question regarding the stepwise stability constants of metal complex formation/substitution.

My lecture notes say that if we have a metal complex, say $\ce{[MX_{6}]}$, and a substitution reaction $\ce{[MX_{6}] + L -> [MX_{5}L]+X}$ with equilibrium constant $K_{1}$, and 5 other equilibrium constants $K_{2}$, $K_{3}$, ..., $K_{6}$ defined similarly for the successive substitutions of $\ce{L}$, then we have
$$K_{1} < K_{2} < K_{3} < \dots < K_{6} $$

One of the reasons given for this is that there are fewer positions available for complexation of the $L$ ligand after some substitutions have been made, and thus it is less likely for the successive collisions to occur. This is described as a "statistical effect". As far as I understand it though, the proability of a successful colision for a given reaction affects its rate, but not its thermodynamic properties, like the equilibrium constant. Am I wrong in this?

If not, why does this "statistical effect" affect the values of $K_{i}$?


texts:
Why is the pi star orbital of the C=C bond higher in energy than the antibonding pi orbital of the C=O bond?

I thought it was the other way around; it's relatively easy to add something to a C=C alkene bond (i.e. halogenation) but halogenation with diatomic halogens doesn't occur with C=O bonds.


texts: Are 3-center-2 electron bonds and and banana bonds same?

texts:
While reading about diborane, I came to know that the two bridging hydrogen atoms in diborane form 3 center 2 electron bonds. On account of repulsion between the two hydrogen nuclei, the delocalised orbitals of bridges are drifted away from each other giving the shape of a banana. Such bonds are called banana bonds. In diborane 3 center 2 electron bonds and banana bonds are same.

What if a compound has only one bridging atom which forms 3 center 2 electron bond. As there is only one bridging atom, it would not face repulsion so it won't form a banana bond.


texts: Unknown white stuff from eggshell reaction with acids and bases

texts:
I have just finished some experiment at home using tea eggs.

First I peel off the shell of the tea egg and place it in a bowl of white vinegar (of course, I consumed the rest of the egg). Not surprisingly, bubbles were seen as the carbonate in the eggshell reacted with the vinegar.
After a day, part of the mixture was decanted into a small glass jar. Sodium carbonate (baking soda) chunks was then added which give off a lot of bubbles of $\ce{CO2}$ plus thick foam of undissolved eggshell mixture. This is repeated until no more reaction occurred (meaning the acid is completely neutralised with the baking soda in excess). After it is settled, a simple filter is made using tissue paper (Coles White Facial Tissue) as the mixture is then poured on top of the tissue into a clean glass cup. This is then left for 7 days, sealed by the tissue paper.
More white vinegar is added to the same liquid level. This is then left to evaporate a bit (and part of the liquid is decanted into another glass jar. Step 3 is then repeated until all eggshell has dissolved (leaving behind brown film like residue which is the membrane of the egg and also the tea leaf related residues
After that,the clear solution is transferred by capillary action using a rolled tissue paper (same brand) to a new glass jar. A few hours later, some white powder is formed on the rolled tissue paper. This white solid is then scrapped off to be stored in another glass jar.
A few days later after realising the colorless solution in the glass jar still does not evaporate significantly, it is poured onto a spread out tissue placed on a clean flat surface. After the solution evaporated, similar white powder was deposited near the edge of the tissue. This is then scrapped off to the same glass jar that contain the white powder.

Now when I prepared to wash everything, I noticed some strange slimy looking sediment (which look like tangled threads and web like in solution) formed that was not there 7 days ago.

I have a couple of suspicions:

Dissolved egg proteins that precipitated
Some unknown reaction between sodium carbonate and eggshell solution
A biofilm of some unknown microbes

  Any idea what that white stuff could possibly be?


texts: I deduced the name as cyclodeca-1,6-dien-3-yne. Is it correct?


texts: How to calculate the pH of solutions of amphoteric salts?

texts:
I've been trying to understand how to calculate the pH of solutions of amphoteric salts, but I just can't figure it out. So, I've seen that it is commonly explained like this (example for a solution of NaH2PO4):
The salt completely dissociates like so
$\ce{NaH2PO4}$-->$\ce{Na+}$ + $\ce{H2PO4-}$
Then the H2PO4- ion reacts with water to form HPO4 2- and H3O+.  (reaction 1)
$\ce{H2PO4-}$ + $\ce{H2O}$ <=> $\ce{HPO4  2-}$ + $\ce{H3O+}$ _______   $\ce{Ka2=6.2 x 10^{-8}}$
And then it reacts with H3O+ to form H3PO4 and H2O.  (reaction 2)
$\ce{H2PO4-}$ + $\ce{H3O+}$ <=> $\ce{H3PO4}$ + $\ce{H2O}$   ________   $\ce{K=Ka1^{-1}, Ka1=7.52*10^{-3}}$
The autoionization of water is negligible.
Now, I imagine this process like this:
The concentration of the $\ce{H2PO4-}$ ion in the first reaction is equal to the concentration of the salt in the solution because the salt dissociates completely. As it reacts with $\ce{H2O}$ to form $\ce{HPO4 2-}$ and $\ce{H3O+}$ (reaction 1), its concentration decreases for a certain value of x. The equilibrium concentration of $\ce{H3O+}$ and $\ce{HPO4 2-}$ in this reaction are the same and equal x. The equilibrium concentration of $\ce{H2PO4-}$ is equal to the concentration of the salt minus x.
$\ce{[H2PO4-]1=c(salt)-x}$
$\ce{[H3O+]1=x}$
$\ce{[HPO4 2-]=x}$
$\ce{Ka2=\frac{[H3O+]1*[HPO4 2-] }{[H2PO4-]1}}$
Then, what is left of the $\ce{H2PO4-}$, that is the equilibrium concentration of $\ce{H2PO4-}$ from the first reaction reacts with the equilibrium concentration of  $\ce{H3O+}$ from the first reaction to form $\ce{H3PO4}$ and $\ce{H2O}$. The concentrations of $\ce{H2PO4-}$ and $\ce{H3O+}$ decrease for a certain value of y. So, in the equilibrium of this reaction, reaction 2, the equilibirum concentration of $\ce{H3PO4}$ will equal to y.
$\ce{[H2PO4-]2=[H2PO4-]1-y=c(salt)-x-y}$
$\ce{[H3O+]2=[H3O+]1-y=x-y}$
$\ce{[H3PO4]=y}$
$\ce{Ka1^{-1}=\frac{[H3PO4] }{[H2PO4-]2*[H3O+]2}}$
So the final concentration of $\ce{H3O+}$ is equal to the concentration of $\ce{H3O+}$ in the equilibrium of the second reaction.
$\ce{[H3O+]final=[H3O+]2}$
We can see that the final concentration of $\ce{H3O+}$ is equal to x-y. Because $\ce{[HPO4 2-]=x}$ and $\ce{[H3PO4]=y}$, we write:
$\ce{[H3O+]final=[HPO4 2-]-[H3PO4]}$
We can express $\ce{[HPO4 2-]}$ and $\ce{[H3PO4]}$ using the equilibrium constants, concentrations of $\ce{H3O+}$ and $\ce{H2PO4-}$.
$\ce{[H3O+]final=\frac{Ka2*[H2PO4-]1 }{[H3O+]1}-\frac{[H2PO4-]2*[H3O+]final }{Ka1}}$
If we assume that the initial concentration of $\ce{H2PO4-}$ is so large that the change of x and y are negligible, we can write that:
$\ce{[H2PO4-]2=[H2PO4-]1=c(salt)}$
If we assume that the concentration of $\ce{H3O+}$ is large enough so that the change of y is negligible, we can write:
$\ce{[H3O+]final=[H3O+]1}$
With those assumptions we can get this commonly used expression for explaining this problem
$\ce{[H3O+]final=\frac{Ka2*c(salt)}{[H3O+]final}-\frac{c(salt)*[H3O+]final }{Ka1}}$
and with a little bit of rearranging, we get this expression:
$\ce{[H3O+]final=\sqrt{\frac{Ka2 * c(salt)}{1+\frac{c(salt)}{Ka1}}}}$
What I don't understand is the fact that we were able to get the last equation because we assumed that the final concentration of $\ce{H3O+}$ ions is equal to their concentration in the equilibrium of the first reaction. But at the beginning, when we established the first equation for the final concentration of $\ce{H3O+}$, we assumed that the concentrations of $\ce{H3O+}$ ions in the equilibrium of the first and second(final) reaction aren't equal. If in the end we assumed they are equal, why can't we calculate the pH just using the first reaction? That way the $\ce{H2PO4-}$ wouldn't be treated as an amphoteric, which obviously isn't correct, so I'm wondering what is wrong in my approach?


texts: The ionization energy of H₂⁺ molecule ion

texts:
I am trying to compute the ionization energy of $\ce{H2+}$ molecule ion from the electronic energy spectrum. The question is whether one should use the purely electronic Hamiltonian or the Hamiltonian with the internuclear repulsion term to do that? I illustrated two ways to compute the ionization energy below. Which one is correct?

Notice that, nuclei are not at the equilibrium distance since in my problem I can manage this distance by external forces.


texts: Finding specific activity of an enzyme from Km values for a reversible enzyme reaction

texts:
I have an enzymatic equation in the form:

$$E + S\xleftrightarrow[k_{-1} = 2.6\text{ x }10^{-2} \text{s}^{-1}]{k_1 = 3 \text{ x }10^8 \text{M}^{-1}\text{s}^{-1}} EX \xleftrightarrow[k_{-2} = 3.8\text{ x }10^{-8} \text{M}^{-1}\text{s}^{-1}]{k_2 = 1.45 \text{ x }10^3 \text{s}^{-1}} E + P$$

For the forward reaction, I have calcluated the $K_m$ value to be:

$${K_m}_f = \frac{k_{-1}+k_2}{k_1} = 4.83\text{ x }10^{-6}\text{M}$$

And for the reverse, I calculated $K_m$ to be:

$${K_m}_r = \frac{k_{-1}+k_2}{k_{-2}} = 3.82\text{ x }10^{-6}\text{M}$$

From this info, I need to somehow calculate the specific activity of the enzyme in both the forward and reverse reactions.

The weight of one enzyme unit is 50,000 kDa.

Specific activity is defined as the number of 'Units' per mg of protein.

One enzyme unit is defined as the amount of enzyme that catalyzes the formation of 1 μmol of product per min under optimal assay conditions, which are assumed for this question (saturation of substrate in forward reaction / saturation of product in reverse reaction).

Can anyone point me in the right direction? I have a feeling that this is related to the $V_{max}$ term in the Michaelis-Menten equation:

$$v = \frac{V_{max}\text{[S]}}{K_m + \text{[S]}}$$

In that $K_m = \text{[S] at}\frac{1}{2}V_{max}$.

So, $$[S]_{f} \text{ at } V_{max} = 2(4.83\text{ x }10^{-6}\text{M}) = 9.66\text{ x }10^{-6}\text{M}$$

So, $$[S]_{r} \text{ at } V_{max} = 2(3.82\text{ x }10^{-6}\text{M}) = 7.64\text{ x }10^{-6}\text{M}$$

but I dont know how to relate it to specific activity.


texts: Are AcO- and PhO- better described as soft or hard nucleophiles?

texts: I would presume soft nucleophiles as resonance increases the energy of the HOMO and therefore they favour SN2 over E2?


texts:
I have a shaver that runs off a rechargeable battery that is dying. Would it be feasible to make a silver zinc battery and use it to replace the existing battery? Cost is not an object, anything less than $2500 I would consider doable. I have a machine shop and a small chemistry laboratory with the standard equipment and glassware, including high vacuum capability, a centrifuge and simple glass blowing capability.

I found a book on silver-oxide zinc chemistry and battery design, but it is $500 and I don't want to spend that if the information can be obtained just as easily elsewhere.

I have tried to find commercial options, but had no luck. Most silver zinc batteries seem to be just for large (multi-million dollar) military or satellite applications. Sony makes a line of silver oxide primary cells for hearing aids, but these are not rechargeable. There is a company called Ultralife that makes medical and military batteries and might have something viable, but before I call them I wanted to check out the opinion of the experts here.


texts: Why is the solubility of sodium acetate trihydrate so much lower than anhydrous sodium acetate?

texts:
According to Wikipedia:

Solubility of anhydrous sodium acetate in water at 0 $^{\circ}$C is 119 g/100 mL (AKA 1.495 mol/100mL)

Solubility of trihydrate sodium acetate in water at 0 $^{\circ}$C is 36.2 g/100 mL.

This makes no sense to me because it should take MORE of the trihydrate sodium acetate (about 1.495 * 136.08 g) to dissolve the same amount of sodium acetate.

So this begs two questions:

1.) Is my understanding of hydrates incorrect? Are their bonds somehow harder to solvate than the anhydrous version? I think this can't be correct because the melting point of sodium acetate trihydrate is 58 $^{\circ}$C compared to the anhydrous melting point of 324 $^{\circ}$C.

2.) Is my understanding of solubility incorrect? I thought solubility is a measure of the quantity of solute that could be dissolved in a solvent. In other words, it seems that MORE sodium cations and acetate anions can be dissolved in 100 mL of water if they came from an anhydrous crystal rather than a trihydrate crystal...
How can that be true?


texts: Nomenclature of ester with cyclic substituents

texts:
I have to tell the name of the following compound

The name is cyclopropylmethyl cyclobutanecarboxylate. All of it makes sense but I don't understand why the suffix carboxylate comes? Why are we writing the single carbon left unaccounted for by using carboxyl ? Kindly clarify.


texts: Solubility determination of Ca(OH)₂ in water

texts: In one problem it's asking me to find the solubility of $\ce{Ca(OH)2}$ in water. In that problem it assumes the starting concentration $\ce{OH}$ to be zero. But for other problems like $\ce{BaSO4}$ in $0.1~M~~ \ce{Na2SO4}$, we account for the $\ce{SO4}$ in the $\ce{NaSO4}$. So in the first problem, why don't we worry about the $\ce{OH}$ from the self ionization of water? Is it just that extremely low of an amount?


texts: How to synthesize 3‐cyclopentylpropanal from (chloromethyl)cyclopentane?

texts:
I am not sure on how to start, but I think of these two possible ways:

Reacting the starting material with Grignard reagent and then oxidise the product with PCC to produce the aldehyde;
Hydrolysis the starting material to produce alcohol and then react the alcohol with PCC to form aldehyde.

But these two ways didn't give the desired product.