texts: Possible causes for flawed results of an EDTA titration for the Ca content of milk

texts:
Earlier today I was trying to find the calcium content of different milks as a part of a school assignment. I used this setup as the basis for my experiment:

I was using $\pu{0.1 M}$ EDTA solution as a titrant. The milk was diluted with destilled water and $\pu{8M}\ \ce{NaOH}$ solution to make sure magnesium won't interfere. The only diversion from the procedure above was that eriochrome black T was used as an indicator. After several attempts, starting with $\pu{10ml}$ and reducing the amount of milk with each trial, absurdly large quantities of EDTA were used without any change in color. Lastly, when a sample of $\pu{(0.1± 0.005) ml}$ milk was diluted in $\pu{0.4ml}$ water and $\pu{0.05ml}\ \ce{NaOH}$, the change in color occured after $\pu{68ml}$ of the titrant was added, which is equivalent to there being $\pu{240g}$ of calcium in the sample (fun fact: this would mean that the milk carton weighs 2.4 tons. I haven't weighed it, but I am pretty sure it does not).

Thus my question is: what could the possible mistakes that lead up to these terrible results be? Equipment was rinsed with distilled water before use, and everything else was done according to the procedure, except for the EDTA solution, which was made approximately an hour before the experiment (and it should be left alone for at least 4 hours after creation). Nevertheless, could this impact the experiment in such a severe way?

The teacher was uncertain of what caused it as well.

We chose our own topics, so no other students have done the same experiment.


texts: Ion/Counter ion layers in the colloid precipitate of silver chloride

texts:
You use a precipitation method to determine [Ag+] in an unknown sample using Cl- ions. Reaction is conducted in presence of HNO3 in excess (relative to Ag+) Which statement is correct concerning the colloid precipitate at the start of the rxn (rxn not yet complete).
A) The ion in Primary Absorption layer is Cl-
B) The Colloid Particle is (-) charge
C) Ag+ is the major ion in Counter-ion Layer
D) Most Cl- ions added are in the precipitate form.

So I think the correct answer is D through process of Elimination and not chemistry knowledge. I know B is incorrect, B/C the precipitate must be AgCl, or possibly AgNO3 since there's Nitric acid here. Both of these are neutrally charged.
I'm pretty sure that Primary absorption layer is the "opposite" of the counter ion layer. So whichever ion goes into the Primary, the opposite ion goes in the counter. Therefore I eliminated A and C, since one cannot be correct without the other being correct as well. (although my first instinct was to put Ag+ in the primary ion layer).
I still have doubts about D. Since the reaction is not complete, and we are adding Cl- to a solution of Ag+, its safe to assume that any Cl- added will react. But HNO3 is a strong acid which dissociates completely, that means there's an excess of NO3- ions floating around. I'm not given any precipitation constants. Can I safely assume Ag+ will bind with Cl- before making AgNO3?
Also could you please confirm or correct my assumptions about Primary/counter-ion layer? I can't find any info it besides vague definitions.


texts:
On which conditions does determining solvent depend on?
1. the higher boiling indicates the solvent

the material with the higher concentration is the solvent
the solvent is kept first in a pot. Then the solute is added.

Here, pls identify the solvent and solute. I hope that it will clear all my doubts about them.


texts: Can a Birch Reduction be done using gaseous anhydrous ammonia?

texts:
Instead of generating anhydrous ammonia as a liquid using either pressure or cryogenic freezing, I would like to avoid the hassle entirely by using anhydrous ammonia generated as a gas. Is there a way to use a gaseous form of ammonia for the birch reduction that doesn't generate sodium amide? I'm a hobbyist chemist so I don't have access to a ton of glassware or specialty equipment.

And before someone asks me if I'm making meth- No. I like my freedom and this is just a hobby of mine. Mostly why I'm trying the birch is because I have heard the color of the solvated electron is quite beautiful. Chemistry is a wonderful science and I wish simply showing an interest in it wasn't considered so unusual!


texts: Potentiometric titration using a pH meter

texts:
Why is the pH of a buffer solution measured before measuring the pH of an unknown solution?
I do not have any idea about it. I had read a chapter about ionic equilibrium and electrochemistry, but have not been able to find out an answer.


texts:
What is the number of possible enantiomers in monochlorination of 2-methybutane?

My approach

When $\ce{Cl2}$ is added to any alkane it prefers $3^\circ > 2^\circ > 1^\circ$.
When it is being added to 2-methybutane, final product (major) formed will be 2-chloro-2-methybutane, which will show 0 chiral centre, hence the maximum number of enantiomers will be

$$2^n = 2^0 = 1$$

My book gave me answer $2$, but no explanation is provided.


texts: Use of pipette during experiments for determination of oxygen by Winkler's method

texts:
We were performing estimation of $\ce{O2}$ by Winkler's method and we were told by the instructor that while adding $\ce{MnSO4}$ and $\ce{NaOH}$ / $\ce{KI}$ the pipette tip should be well below the surface of the solution.

When asked as to why this should be done, he said that if the reaction took place at the surface then there's a possibilty that the atmospheric $\ce{O2}$ may get dissolved.

Is it true?


texts: What is the surfactant's role in the non-coalescence of water droplets?

texts: I have recently seen many videos that talk about the noncoalescence of water droplets; however, I do not understand the purpose of adding surfactants into the water. From my knowledge (high school), objects will stay on top of the water due to water's cohesion, resulting in a high surface tension. This is why in an experiment of a paperclip floating on water, when you add soap, the paperclip sinks - due to the decrease in surface tension. What I am really confused is that the noncoalescence of water droplets works BETTER when surfactants are added. It would be great if anyone has an answer, I am really puzzled...


texts: Is Heisenberg uncertainty principle really a demerit of Bohr model?

texts:
My teacher taught that Heisenberg's uncertainty principle is a demerit of Bohr atomic model.
But as the below paragraph from the article What Is Heisenberg’s Uncertainty Principle? says and as per my thinking Heisenberg's uncertainty principle tells about the uncertainty, if we try to do some practical observation; while what Bohr told us by his formulas was almost fully theoretically derived. The paragraph basically tells that when photon strikes any subatomic particle then change in velocity occurs and uncertainty in position is incurred:

One way to think about the uncertainty principle is as an extension of how we see and measure things in the everyday world. You can read these words because particles of light, photons, have bounced off the screen or paper and reached your eyes. Each photon on that path carries with it some information about the surface it has bounced from, at the speed of light. Seeing a subatomic particle, such as an electron, is not so simple. You might similarly bounce a photon off it and then hope to detect that photon with an instrument. But chances are that the photon will impart some momentum to the electron as it hits it and change the path of the particle you are trying to measure. Or else, given that quantum particles often move so fast, the electron may no longer be in the place it was when the photon originally bounced off it. Either way, your observation of either position or momentum will be inaccurate and, more important, the act of observation affects the particle being observed.

Is Heisenberg's uncertainty principle really a demerit of Bohr model?
Reference

Jha, A. What Is Heisenberg’s Uncertainty Principle? The Guardian. November 10, 2013.


texts: How to name the tautomers of hexane-2,4-dione correctly according to IUPAC rules?

texts:
Today I was considering to answer the question "Which tautomer of hexane-2,4-dione is more stable?" I wanted to run a few calculations and while preparing a directory structure I wanted to make sure that I used correct and unique names for the compounds. I am citing the picture in the named question:

I was going to derive the names of the structures from the parent compound hexane-2,4-dione. Hence I would have named compound 1 (Z)-2-hydroxyhex-2-en-4-one and 2 (Z)-4-hydroxyhex-3en-2-one.

When I recreated the above picture in ChemBioDraw and used it to autogenerate the name, the result for 1 was different: (Z)-5-hydroxyhex-4-en-3-one. See below.

I am no expert on nomenclature and I do not have the blue book handy. Usually I rely on the names generated through software. Most of the times they are accurate enough to name a compound unambiguously and that is often what I am going for.
I understood from this answer, P-14.3.5 Lowest set of locants, that I should use the 4,2,2 set over the 5,3,2.

Is my thinking correct and the auto-generated names are wrong, or is the software correct and my thinking is wrong?


texts: Near melting thermoplastic material accumulates in the sharper corners. What is this phenomenon?

texts:
I have a part made of a thermoplastic material. When I heat it up and cool it down, the dimension of the part changes non-uniformly. Somehow the melted material tries to fill the sharper corners. So for example if there is a corner with a fillet of $r_1$ and wall thickness of $t_1$, after a high temperature experiment the part deforms to $r_2$ and $t_2$ where

$$\left(t_2-t_1\right)<\left(r_1-r_2\right)$$

I know it has to do with adhesion and capillary, but not knowing that much about chemistry jargon, I'm not able to find the right term for this phenomena. I would appreciate if you could help me know if this phenomena has a name and what parameters control this behaviour?


texts: What will be the major product when conjugated alkene (like 1,3-butadiene) is reacted with HBr in presence of R2O2?

texts:
What will be the major product when conjugated alkene (like 1,3-butadiene) is reacted with $\ce{HBr}$ in the presence of $\ce{R2O2}$?

As we know, two products are formed when no $\ce{R2O2}$ is used because of conjugation in double bond and carbocation. But when $\ce{R2O2}$ is used, free radical is formed.
So, will there be the same case in the following question as well? Also, if answer is yes, then what will be the major product?


texts: Understanding dissolution of CO₂ in Selexol and Rectisol

texts:
I'm trying to understand pre-combusiton carbon capture processes as described in this presentation.

I'm told that solvents such as chilled methanol ($\ce{CH3OH}$) and dimethyl ethers of polyethylene glycol ($\ce{C_{2n}H_{4n + 2}O_{n + 1}}$) can dissolve $\ce{CO2}$ from a gasified coal fuel (before combustion) under the action of increased pressure.  I'm struggling in understanding how the increased pressure induces the dissolution of $\ce{CO2}$ from the gasified coal.  I'm also a bit rusty with my chemistry, by saying $\ce{CO2}$ is dissolved by the solvents, what is really going on, chemically?


texts: What are some books, websites, etc. where I can find the detailed protocol for standardization of sodium thiosulfate with dichromate?

texts:
I am looking for a book or website such as "Vogel's Textbook of Quantitative Chemical Analysis" where I can find methods for analyzing/standardizing a particular species easily.

I am not looking for an exact sub area such as water analysis or drug analysis; rather I want a resource like Vogel's which indexes generic analytical methods, both classical and modern.

Edit:
Actually I am looking for the method of standardizing a sodium thiosulfate solution using a potassium dichromate solution. I can't find the method in "Vogel's Textbook of Quantitative Chemical Analysis 6th Edition".


texts: Are halogens a further classification of non-metals, or are they another group themselves?

texts:
I've searched many pages in the internet, and many just classify halogens
(Grp 7A) as non-metals. However, my teacher classified them as another group in the periodic table, and when asked which groups are classified under non-metals, she written the correct answer to be group 3A-6A. I'm very confused as I thought non-metals include halogens?

Thanks in advance!!:)


texts: How could I create a machine that as rapidly as possible creates greenhouse gases from air?

texts:
For a very large-scale project, I am trying to create a greenhouse gas demonstration device, which rapidly produces greenhouse gases from atmospheric air using only electricity, or any chemical reactions or chains of chemical reactions that can attain their input energy from electricity. At the intake would be a very powerful fan which rapidly forces air through the system, to speed up the process. How would it be done?

UPDATE:

I was thinking nitrogen oxides would be best, considering the atmosphere is approximately 78% nitrogen and 21% oxygen. But what would be the fastest way to produce them, assuming price is not really an issue?


texts: Thermal decomposition products of polyurea?

texts:
Are the thermal decomposition products of polyurea polymers known, especially of the urea group, in the absence of water?

Looking at the formula

R-NH-C=O
     |
    HN-R

there appears to be no obvious candidate for a decomposition product - not enough oxygen for CO2, not enough hydrogen for Ammonia.

Any ideas or, even better, references?


texts:
Is an endothermic reaction always endothermic at all conditions of pressure, temperature etc.? Similarly for exothermic... I mean is sign of ∆H always the same as sign of ∆H°?

This might seem to be a vague doubt but I just feel that there can be a reaction with trends of energies of formation of reactants and products such that endothermic reaction changes to exothermic or vice versa subject to change in concentrations of substances or external factors like temperature, pressure etc.

This is just a random thought of mine and even an example in this direction would be helpful.

Thanks!


texts: When non-polar particles interact through dispersion forces, how fast does a temporary dipole induce a dipole in the neighboring molecule?

texts:
The current question is inspired by this existing question: At what frequency does a non-polar molecule acquire a dipole able to participate in London Dispersion forces?. In the comments and answers, it says that there is always a dipole (but the time-average of these dipoles is zero), so it does not make sense to ask how long the dipoles last, or how frequently they appear.

I am wondering how long it takes the neighboring molecule to adjust its electron density to the temporary dipole. Also, I wonder if this is the correct picture: that one molecule has the temporary dipole and the other responds with an induced dipole. Or is it more accurate to say that the neighboring atoms find some common groove of swaying their charge distribution.


texts: Why do isomeric bis-ethylenediamine cobalt complexes react differently?

texts:
A compound $\ce{Co(en)2(NO2)2Cl}$ has been prepared in a number of isomeric forms.One form undergoes no reaction with $\ce{AgNO3}$ or $\ce{(en)}$ and is optically inactive.

A second form reacts with $\ce{AgNO3}$ but not with $\ce{(en)}$ and is optically inactive.

A third from is optically active and reacts with both $\ce{AgNO3}$ and $\ce{en}$. Identify each of these isomeric forms. Name and sketch each of the structures.

My attempt:

I understood how to use the information of reaction with $\ce{AgNO3}$ and optical activity but  couldn't understand what does reaction with $\ce{en}$ represent (I know $\ce{en }$ means ethylene diamine).

In solution, it is given that, if the compound reacts with en it means monodentate ligands are cis to each other,if not it is trans to each other.
I couldn't understand why it is so. please help.


texts: How does physical adsorption of mixed gas occur on solid? (eg I mean how the gas molecules of compete each other for a slot on solid surface)

texts:
I am working on sorption phenomenon of gases (including inert gas) on coal seam surface.

For a mixture of 2 gases at a certain pressure, carbon dioxide and methane, for instance, $\ce{CO2}$ is definitely adsorbed quicker and more comparing to methane. How come? I try to explain by Langmuir Isotherm and IAS model but it doesn't help much. For Langmuir isotherm, the affinity of gases to solid is determined by "b=1/PL" which comes from experiment. Langmuir isotherm assumes that all gas have equal access to the solid surface; however, this is untrue in reality.

Can you help me explain it in the thermodynamics point of view or molecular forces please? ($\ce{CH4}$, $\ce{CO2}$ are both non-polar gases)


texts: Dissociation behaviour of polyelectrolytes

texts:
Assuming a solution of 100 polycationic molecules, each of them carrying 100 amino groups and an apparent pKa of 6.5. Would it mean that, at a pH of 6.5,

50 molecules will be fully protonated
50 amino groups of each molecule will be protonated  or
50% of the total amount of amino groups present in solution will be
protonated?

The third option would mean that each molecule can have any charge number, from 0 to 100, with 50% of the 10.000 amino groups being protonated.

In other words, is it safe to state that, at a pH below 6.5, all molecules will be mostly protonated?

Edit due to ambiguity:

In other words, is it safe to state that, at a pH below 6.5, all molecules will have more protonated amino groups than unprotonated?

Many thanks in advance!

Ben


texts:
I was wondering if someone could explain me what exactly is Gay-Lussacs law?

And my textbook says that Berzelius and Dalton concluded based on that law that all gases have same amount of particles. How?


texts:
I performed an experiment where I did this:

  Add one spatula of malachite to a test tube, add dilute hydrochloric acid to the malachite until the test tube is one third full. Note observations and identify gas produced.

The green solid turned to a blue solution and there was an effervescence of hydrogen. However, I now realise that copper doesn't react with acid and malachite is a copper carbonate hydroxide mineral...
I researched online and found that

  It dissolves in sulfuric acid to give Copper sulfate, Carbon dioxide
  and Water.
  http://wiki.answers.com/Q/What_happens_when_malachite_is_dissolved_in_sulphuric_acid?classic=true

So how did I get that malachite reacted with acid and did produce hydrogen with a squeaky pop test?

Thanks in advance


texts: How could I find the solubility of hydrocarbons such as iso- and n-Butane in liquid Methane?

texts:
I am trying to figure out the dissolution capacity of iso and normal butane in methane at very low temperatures (110K). This would allow me to make compositions that prevent freeze out of these hydrocarbons at these very low temperatures. For example I would like to prepare a 5% mix of iso-butane in methane and make some measurements at 110K. However, if the solubility of methane is only 3%, I will have a 2% bias in my final measurement.

Any ideas would be much appreciated.

Thanks.


texts:
Would be very grateful if someone had the answer or can point me in a direction. I've searched a lot but didn't find it yet. It could benefit others as well.

I do not have a high tech lab, but I can invest, would prefer methods that don't require above \$100 or \$300, but am open to it. I can build a furnace and weld.

Edit: As I don't have 50 rep points to reply, I will answer here to comments the first comment as to what use I need it for;
It is for water Nanofiltration of 1 micron or lower ,and secondly batteries making.
--- Second comment; thanx alot for the document, I will check it and tell you about it.


texts: Paint changes color when applied to Stucco. Chemical rxn assumed, but what?

texts:
PROBLEM:
When I apply paint to my home’s exterior stucco (currently white), the paint changes color. The grays change to purple. The whites change to yellow. Greenish-beige becomes orange. I have purchased many samples of paint, and a color change is apparent for all but the darkest colors. The change in color starts happening immediately when I apply the paint, and it becomes more intense over subsequent days. After a few days, there is a radical difference between the paint’s intended color and the new color.

Apparently a chemical reaction is occurring between the paint and a substance in/on the wall, but I don't know what it is, or how to remedy it.

SURFACE FACTORS:

The house is stucco, so perhaps the surface is very alkaline. The house was built in 1971, and several coats of paint have been applied by the previous owners since then, so I would think the alkalinity would no longer be a factor, but perhaps it is. (Would it even be possible for improperly cured stucco to remain highly alkaline for 44 years?)
The previous owner told me that, around fifteen years ago, he painted the house with "pool paint." (Unfortunately, I don’t know what type of “pool paint” was applied, or why it was applied.) My guess is that this was in response to the color-changing problem rather than the cause of the problem, but I don’t know for certain.  (It is interesting that the pool paint has remained white all this time, while I’m unable to get a true white.)

I have painted the wood next to the stucco, and the paint on the wood appears exactly as it should and it remains constant(aside from becoming just slightly lighter as it dries). In other words, the paint only changes color on the stucco. Since the wood was never painted with pool paint, and since the wood is obviously not stucco, I still don’t know which factor (pool paint, stucco, or something else) is causing the color change. However, this does show me the paint color is truly changing on the stucco.

I have some chemistry background, but I'm really stumped by this problem.

Any help in figuring out what’s going on would be very much appreciated.


texts: Is it possible to export a rotating .gif format picture from chemapps.stolaf.edu?

texts:
I mainly use chemapps.stolaf.edu to get the 3D structure of a molecule from the SMILES. It renders the molecules as:

I have the option to rotate the image by specifying the $x$, $y$, and $z$ spin rates:

However I can't seem to find a way to save a spinning image as such. I can only save .png files. I need spinning images to demonstrate 3D images. Can anyone help me get a spinning image?


texts: Are there amide versions of lactides and lactones?

texts:
In my book, I read that Lactides and lactones are cyclic esters which contain two and one ester group in them, respectively. They are formed when $\alpha$-hydroxy; and $\gamma$- or $\delta$- hydroxy carboxylic acids; respectively, are esterified.

Now, there exists a certain similarity between amides and esters (both being carboxylic acid-derivatives), such as the similarity between ester bonds in polyesters and amide bonds in polyamides.

In this context, I have a question: Do amides have compounds similar to lactides and lactones? What are they commonly known as?

Please let me know a good source that I could refer to in addition to any answers posted, or please cite any sources used.


texts: Finding electron configuration of lanthanide ions

texts:
When I have a gadolinium ion ($\ce{Gd^3+}$), how can I calculate its electron configuration?

$$\ce{Gd} : \mathrm{[Xe] (4f)^7 (5d)^1 (6s)^2}$$

Do I need to first subtract the 2 electrons in the $\mathrm{s}$-orbital and then the $\mathrm{d}$-/$\mathrm{f}$-orbital?


texts: Difference between coordination entity and coordination sphere

texts:
What’s difference between coordination entity and coordination sphere? Can they be same? Here in my book same example is given for both coordination entity and coordination sphere.

Please help.

Source:http://ncert.nic.in/ncerts/l/lech109.pdf

Section 9.2 Definitions of Some
Important Terms Pertaining to Coordination Compounds

Page no. 240-241


texts: When I learned about crystal field theory I had fallen on a paradox. When K4[Fe(CN)6] is formed then three d orbitals are occupied by electrons of Fe2+ pairly and the rest two d orbitals are occupied by electrons of lone pair electron of CN-. So when visible light falls on it, the d orbitals are splitted into two sets which are t2g and eg and the electrons of eg orbitals jump into t2g orbitals by absorbing a portion of this light. But my question is that how the electrons of eg orbitals jump into t2g orbitals when the d orbitas are already occupied by the electrons of Fe2+ and ligand during bonding.


texts: I picked up some stones from a hiking trip. What can I use to thoroughly clean the mud and other hard deposits on the surface of the stones? I have only washed them with plain water.


texts: Why doesn't LiHCO3 exist in solid state?

texts: I have read that $\ce{LiHCO3}$ does not exist in solid state. Is it because of the size of anion-cation concept or is it something else? So why is it only for lithium and not for sodium too?


texts: Why f is multiplied in solubility of salt constant

texts:
I understand till we get “f” And also why f is directly proportional to PH. But I don’t understand why f is multiplied in solubility product with solubility of salt of weak acid.

(Sorry for poor english) (couldn’t find link of pdf of this book online)


texts: Concentration of organic acids in lichens/rock substrates/soil (particularly oxalic and citric acid)

texts:
I am trying to design an experiment testing the efficacy of lichen acids to solubilize and mobilize nutrients from minerals in a lunar regolith simulant. My research so far indicates that oxalic acid and citric acid are especially important lichen excretions in this process, but I am struggling to find resources detailing the concentration of these and other organic acids in various lichen species. The closest I've come is finding very general indicators of concentrations (i.e. between 0 and 15mM for "lichens").
Does anyone know of any resources or databases that detail organic acid concentrations in different lichen species? Am I pursuing this from the wrong angle? Any input is appreciated!


texts:
I was reading MECHANISM OF α-HALOGENATION OF ALDEHYDES AND KETONES:

As you can see in the third step. Bromide ion is picking up a base from protonated acetone. Doesn't that step mean that protonated acetone is stronger acid than Hydrobromic acid? Is that even possible?


texts: How to dissolve grass/leaves without affecting enclosure?

texts:
I've got two questions:

What sort of compound can dissolve grass/leaves fastest without leaving "much" trace?
What sort of enclosure is required for this to be doen safely and without damaging the enclosure?

I am doing a small experiment and would like to try dissolving few leaves within a glass or something of the sort.


texts: What's the electronic configuration of Nickel and Oxygen in RNiO3 (R=Rare-Earth)?

texts:
Nickel's electronic ground state is $\mathrm{3d^8 4s^2}$ (there's a dispute on this, but let's not worry about it for now). Oxygen's is $\mathrm{2s^2 2p^4}$. In a Rare-Earth based Nickelate with chemical formula $\mathrm{RNiO_3}$, if we assume simple ionic bonds, then what should the electronic state be?

Literature indicate that the "classical" case is $\mathrm{Ni^{3+} O^{2-}}$ corresponding to $\mathrm{3d^7, 2p^6}$. But this means that Oxygen has gained 2*3=6 electrons. But how can this be possible if Nickel has donated only 3 electrons?


texts: Pseudocapacitive behavior in EC electrode materials

texts:
As we know in electrochemical capacitors or supercapacitors, the basic electrochemical signature is CV (cyclic voltammogram) curve. Some materials like $\ce{RuO2}$ and $\ce{MnO2}$ have a capacitive-like CV curves similar to that of EDLC (electro double layer capacitors), so we call such a material pseudocapacitive materials.

On the other hand, materials like cobalt oxides and $\ce{Ni(OH)2}$, which is battery-type electrodes that exhibit faradaic behavior (even those that are electrochemically irreversible), have been presented in the literature as pseudocapacitive materials, which leads to a confusion for the readers.

So, when could we say that a material has a pesudocapacitive behavior?


texts: How do you Benzylate (add a benzene group to) cyclic compounds?

texts:
How do you add a benzene group to cyclic compounds like piperidine, piperazine and phenyl derivatives?
Piperidine

Piperazine


texts:
The liquid we use to dilute is the diluent, what is the substance that is being diluted called? I considered "dilutant" but it seems ambiguous. I can't seem to find a common term in literature either.

A possible analogy is solute and solvent. You'd think there'd be a counterpart for diluent too.


texts: Is it possible to fractionally distill a compound made up of substances with very similar boiling points?

texts:
Let's say I have a solution that is made up of substances that have very similar boiling points, say less than 5 degrees apart. Is it even possible to fractionally distill those substances, say, using a vacuum still?

Which method is more precise, heating the solution and swapping out condensation vessels as the temperature increases, or having a column with the ability to fractionate in stages?


texts:
Why can't an enolate anion successfully displace a halogen from a benzene? I am told that the geometry is incorrect; that such SN2 substitutions take place on $\mathrm{sp^3}$ hybridized (i.e. tetrahedral) substrates.

This reasoning is circular. So what's a better reason?

I can think of one reason but it is not satisfactory; it's still a bit circular. SN2 = backside attack; how would one attack a planar bromobenzene? From within the ring? Seems like there would be a lot of possibly unfavorable interactions with the p-orbitals for something to get within the ring. Also this doesn't explain why substitution reactions with enolate anions don't take place at other $\mathrm{sp^2}$ carbon atoms - i.e. bromoethene.


texts:
I am trying to come up with a synthesis of 7-hydroxyspiro[4.5]decan-1-one;

I think I could use these starting reagents below;

Could I potentially generate the enolate of the cyclic ketone starting material and it would attack the double bond of the alcohol? If this is correct, how would the ring close to create the spirocycle? Thanks.


texts: Why is this a Lewis structure of ethyl acetate?

texts:
I read somewhere that the structure in the following picture is a Lewis structure of ethyl acetate.

However, I don't understand why:

The $\ce{C}$ has a positive charge, but only three bonds
The $\ce{C}$ does not satisfy the octet rule.


texts: Which carbon electrode gets plated with Zinc on a beaker with zinc sulphate solution?

texts: In a beaker containing zinc sulpate and two carbon electrodes connected to a battery, which electrode gets electro plated with Zinc? Why?


texts: Molar Absorptivity of Copper(II) Sulfate

texts:
What is the molar absorptivity of copper sulfate? I am trying to find the molarity of copper sulfate solution by absorption in a spectrophotometer with a cuvette.

However, I can't find $\varepsilon$, the molar absorptivity coefficient of $\ce{CuSO4}$. I searched it up online, and I found experimental data saying that is $\pu{2.81 L mol-1 cm-1}$, but another source says that it is $0.91$.

I have searched on various databases including NIST's, but I couldn't find anything. Is there a definite molar absorptivity for everything, or is it all experimental?


texts:
I'm reading a couple of methods of extracting nicotine from tobacco. I have read that many people trying to commit suicide with nicotine. The method is simple:

Boil some tobacco with water
Leave it for a few hours
filter the solution
boil it till you get a thick black syrup thing

That's pure nicotine and they claim that 2-3 drops of that can kill you. Is that true? What do you think?

I am not thinking to commit suicide. I just asking because it is really  weird that so little a dose can be fatal.


texts: Electrons split in Stern-Gerlach experiment but not in Thompson's experiment?

texts: So when electrons are fired through a magnetic field in Stern-Gerlach experiment they split into two beams depending on their spin but where was this phenomena when Thompson was calculating charge to mass ratio of electron? Shouldn't his cathode ray beam have split up too?


texts:
Assume the x-axis to be the internuclear axis. Hence, both $1s-1s$ and $2p_x-2p_x$ will form $\sigma$ bonds.

Also consider the fact that $p$ orbitals have more directional characteristics.

Given the above facts, shouldn't the $2p_x-2p_x$ overlapping be more effective than $1s-1s$ overlapping? Why is $1s-1s$ orbital overlapping stronger than $2p_x-2p_x$ orbital overlapping?


texts: How does the calorimeter affect heat released by the system (q)?

texts:
Here are the 2 questions I am pondering about

How would the calculated quantity of heat (q) released by a system differ if the calorimeter's heat capacity was taken into account?

My thought process is that the calculated quantity of heat (q) released by a system would increase if the calorimeter's heat capacity was taken into account, b/c the calorimeter would aid in absorbing the heat along with the surroundings, so change in temperature would increase ($q=m c \Delta T$)

How would quantity of heat (q) released by a system differ if the calorimeter was not a good insulator?

Here, I am not sure how to word the answer, but if the calorimeter wasnt a good insulator, heat released by a system would be lost to the environment, and thus less heat released would be calculated via $q=m c \Delta T$ due to a smaller change in $\Delta T$.


texts: How small a peak could one identify by GCMS

texts:
I'm trying to characterize the impurity profile of an organic liquid sample that is already described as 99.7% pure (Boiling Point 230 C).

Would a GC-MS be a viable way to identify the smaller peaks? e.g. How small a peak could one expect to get a decent mass spec. pattern for? Say, a peak with 0.01%  of total peak area, would it be viable to identify it on a GC-MS?

I'm assuming the smaller peaks can be resolved satisfactorily. I don't need quantification of the peaks just identification. I can match against the NIST library of spectra but also have a clue based on the manufacturing process about what the likely impurities may be.


texts: Angular Momentum Of S-subshell of an atom?

texts:
The angular momentum of every S-subshell of an atom is 0 by Azimuthal Quantum No. Relation. But if angular momentum of S-subshell is zero. Then by,
Angular Momentum =Mass×Velocity×Radius;
Radius of S-subshell shoul be 0 which is not the the case. Then why do we consider Angular Momentum of S-subshell zero.


texts: Determining global minimum structures for ion-water clusters

texts:
What is the best way to find the global minimum structure(or get close to it) for an ion and N waters? (i.e. ion cluster in vacuum)

For example, consider Flouride ion cluster with N=5 waters.
I want to determine the global minimum structure (using Gaussian09 for a given level of theory and basis set).
This helped me get started (Geometry optimization: dependence on initial geometry), but initial geometry sampling is easier for molecules compared to clusters.

What is an intelligent way to generate reasonable initial configurations for this cluster (say for N=4,5,6)?
Constraint: My computational resources allows me to optimize about 10 structures at a given time for a reasonable level of DFT theory. I might be able to do a maximum of 100-200 optimizations.


texts:
I am looking at some data regarding a study around a channel-blocking agent called suxamethonium.

The histograms of the open times of the channels at varying concentrations of suxamethonium are given. However, I am having a difficult time figuring out the dosage. Here are examples of dose listing formats:

200 μM-Sux
500 μM-Sux

etc.

I understand that μ in this context is to mean micro and I believe the suffix "Sux" is supposed to stand for suxamethonium. But what is the capital "M"? I looked it up in a scientific notation table and it stands for mega. Am I supposed to infer that this is a liquid (i.e. ML)?


texts: Timescale of Protonation and Deprotonation across micelle layers

texts: I am curious about the timescales of protonation and deprotonation of solvent systems. As a followup, how is this affected when the proton source is separated by an organic phase? For instance, it is known that the pH inside a liposome can be maintained from the outside. What are the timescales of protonation when the protons need to be transported across various micelles thickness.


texts: How to calculate the mass of magnesium necessary to produce a certain volume of hydrogen gas?

texts:
How many grams of magnesium metal are required to produce 44.8 liters of hydrogen gas at STP according to the chemical equation shown below? (Answer: $\pu{48.6 g}$)
$$\ce{Mg(s) + 2 HCl(aq) -> MgCl2(aq) + H2(g)}$$

What I have done:
Amount of hydrogen to be produced= 44.8/22.4 = 2 moles of $\ce{H}$ = 2.02 grams of $\ce{H}$.
Amount of magnesium metal needed $$=\frac{\pu{2.02 g} (\text{of}~\ce{H})\cdot \pu{1 mol} (\text{of}~\ce{H2})\cdot \pu{1 mol} (\text{of}~\ce{Mg})\cdot \pu{24.31 g} (\text{of}~\ce{Mg})}{\pu{2.02 g} (\text{of}~\ce{H2})\cdot \pu{1 mol} (\text{of}~\ce{H2})}$$
I'm not getting the correct answer, can someone please explain how to do this using dimensional analysis? Please just tell me only how to do this, do not show it.


texts: Why is dichloromethane immiscible in water?

texts: We know that like dissolves like. And dichloromethane is a polar solvent and water is also a polar solvent. Also there ought to be a strong hydrogen bonding between the chlorine and hydrogen atoms. So why is it immiscible?


texts: Is there a chemical compound can transform heat into light at 70 °C?

texts:
Is there is compound that can transform heat into light as phosphorescence / thermally generated photons at around 70 °C, in a reversible reaction?

For example, is there a phosphor which can be visible at 70'C and not at 20 degrees?

I'd very much appreciate some information. Thanks!


texts: Does a mixture of gases contain equal volume to that of the container they're in? Why?

texts:
In my textbook, the derivation of Dalton's Law of Partial Pressure is done by keeping the volume of a mixture of gas in a container constant which is equal to the volume of container itself.

How can this be so? Let's say we have 100 moles (fairly large) of Nitrogen and 1 mole of hydrogen gas taken in a container of a certain volume. Then is the volume still considered equal to that of the container in this case? Because this is what is done when deriving Dalton's law of partial pressure?

Also, if we have 100 moles of a  gas and another just a single molecule then what happens?


texts: Determining the Average Bond Enthalpy for the C-F bond

texts:
Given the following data, how would you work out the average bond enthalpy for $\ce{C-F}$ bond. I've tried setting up the chemical equations and applying Hess's Law, but that's not getting me anywhere.

$\Delta H_\mathrm f^\circ(\ce{CF4(g)})=-680~\mathrm{kJ~mol^{-1}}$

Bond enthalpy, $\ce{F2(g)}=+158~\mathrm{kJ~mol^{-1}}$

$$\ce{C(s) -> C(g)}\quad \Delta H=+715~\mathrm{kJ~mol^{-1}}$$

EDIT: These are the equations I used:

$$\begin{align}
\ce{C(s) + 2F2(g) &-> CF4(g)}\\[6pt]
\ce{F2(g) &-> 2F-(g)}\\[6pt]
\ce{C(s) &-> C(g)}
\end{align}$$


texts: Reducing Strength of Phosphorus Oxoacids

texts:
My chemistry textbook suggests that "acids which contain a P-H bond have strong reducing properties". Both hypophosphorous acid (H3PO2) and pyrophosphorous acid (H4P2O5) contain two P-H bonds; a P-O-P bond is present additionally in pyrophosphorous acid (as in the figures below).
Which of these two turns out to be a stronger reducing agent, and why? Or do they have equal reducing properties?


texts: Magnesium oxide dissolving in distilled water

texts: Magnesium oxide is a salt, and salts dissolve in distilled water, due to water being polarized. Therefore I would expect that you would find free ions, which is confirmed by the water conducting electricity. But most sources I find states that magnesium hydroxide is created through a reaction with the water. I would appreciate if someone could tell me what is correct and why the other one is false.


texts:
Question
  Which species can't appear in the rate expression for this reaction scheme?
  Here is the reaction scheme in steps:
  \begin{align}
\ce{A + B~(slow) &\rightarrow C} \\
\ce{C~(fast) &\rightarrow D + B}\\
\ce{D + E~(fast) &\rightarrow F}\\
\ce{F~(fast) &\rightarrow G}\\
\end{align}

The answers are apparently F and G, but I don't see why D and E couldn't also be valid (considering the first step is the slowest). A and B will inevitably be in the rate equation since they are reactants in the rate determining step. C produces B (alongside D) and so will also be in the rate equation as a result. However, why can't we rule out D and E of being in the rate equation, considering they don't seem to have any effect on the concentrations of A and  B.


texts: Quotable Literature for the Enthalpy of a Proton

texts:
A proton obviously has no electronic energy, no vibrational and no rotational degrees of freedom. Therefore I think it is fair to assume, that $$H(\ce{H+})=\frac32\cdot \mathcal{R}\cdot T$$ holds for the translational degrees of freedom. I am looking for some quotable literature where they state that, or if that has not been stated anywhere, how to derive this.

I am doing quantum chemical calculations, i.e. gas phase. I define the proton affinities via
$$\text{PA}(\ce{M})=-\left(H(\ce{H+M})-\bigr[H(\ce{M})+H(\ce{H+})\bigr]\right)$$
for the reaction
 $$\ce{H+ + M -> H+M}.$$
This is respecting the (quite common) sign convention to show the energy released upon binding a proton.
I need a reliable source or at least a best-practice example(s) for $H(\ce{H+})$.


texts: Does HI-6 form a covalent adduct with acetylcholinesterase?

texts:
According to sources provided below, the oxime HI-6, or Asoxime Dichloride, as it is also called, besides being a reactivator of acetylcholinesterase that has been inhibited by organophosphorus compounds, can act as an AChE inhibitor itself.In the process of inhibiting AChE, does HI-6 form a covalent adduct with the enzyme (Similarly to how TMTFA forms an adduct) or is the inhibition due to HI-6 simply occupying the active site without covalently binding with the enzyme?
References:

Soukup O, Pohanka M, Tobin G, et al. The effect of HI-6 on
cholinesterases and on the cholinergic system of the rat bladder.
Neuro Endocrinol Lett. 2008;29(5):759-762.
Pohanka, M. (2012). Alpha7 Nicotinic Acetylcholine Receptor Is a
Target in Pharmacology and Toxicology. International Journal of
Molecular Sciences, 13(2), 2219–2238. doi:10.3390/ijms13022219
Pohanka, M. (2013). HI-6 modulates immunization efficacy in a BALB/c
mouse model. Environmental Toxicology and Pharmacology, 36(3),
801–806. doi:10.1016/j.etap.2013.07.012


texts: Why do electrolytic concentrations affect voltage in electrochemical cells?

texts:
I know that the voltage of a cell is calculated via the Nernst Equation as $$E_\text{cell}=E^\circ-\frac{RT}{nF}\ln Q_\mathrm r$$ where $Q_\mathrm r$ represents $\frac{\text{concentration at the anode}}{\text{concentration at the cathode}}$.

However I don't understand how these concentrations actually affect the potential difference. Could anybody explain the physical processes that mean changing the concentrations affect the voltage of the cell?


texts: Conductivity variation on Caustic (NaOH) Dilution System

texts:
I am reading the drawing for an automatic caustic dilution system where 50% NaOH is diluted down to 20%.

I was expecting to see a density sensor on the outlet to provide feedback to the dilution pumps for ratio-ing. i.e. To keep the density at 20% and prevent it from moving to say 19% or 21% by adjusting the amount of water.

However, the vendor seems to have used a conductity sensor on the outlet instead. I am skeptical whether the conductivity of NaOH will vary a lot between 19% to 21%. Isn't it already fully ionized?

Thoughts? Will this work?


texts: How do I make a solution of spinach to titrate with pottasium permanganate?

texts: My teacher said something about straining it but I didnt quite get it


texts: Dependence of reaction rate on concentrations and stoichiometric coefficients of reactants and products

texts:
Consider a general equation of a reaction:

$$
\ce{aA + bB -> \text{Products}}
$$

We can say, in chemical kinetics, that the rate of the reaction is:

$$
\text{Rate} = k([\ce{A}]^a [\ce{B}]^b)
$$

where $\ce{[A]}$, $\ce{[B]}$ are the concentrations or active masses of the reactants.

My question is, why is the rate of reaction proportional to the concentrations of the reactants raised to the power of their stoichiometric coefficients ?

(Not really the point of the question, but why to the power and not just a product of the coefficients?)


texts: How to reduce Fe(III) impurity in Iron(II) sulfate?

texts: I have bought 50 kg $\ce{FeSO4}$, but it was stored on air, and it has turned to brown. Is there a cheap method to recover some $\ce{FeSO4}$?


texts: How many basis functions used in STO-3G and 6-31+G** for the water molecule?

texts:
I am a little confused about how to decide how many basis functions that are used in a particular basis set for a given molecule.

STO-3G is a so-called "minimal basis set", meaning that only one basis function is used for each atomic orbital in the atoms of which the molecule is made from.

The water molecule has two H atoms and one O atom, with 1s1 and 1s2 2s2 2p6 electron configurations, respectively. When STO-3G is used, would that then mean that three 1s type basis functions, one 2s type basis function, and 3 p-type basis functions are used, totalling at 7 basis functions that are used, each being made up from a linear combination (LC) of three simple Gaussian functions?

The 6-31+G** is a split-valence basis set, which includes both diffuse and polarisation functions. The two asterisks tell that polarization functions are used for both the H atom and the O atom, p and d polarization functions respectively. I am not sure "how many" polarization functions are used per atom - just 1, or one for each of the p-orbitals? (Some basis sets are of the form 6-31G(3pd); does that mean that 3 p and 1 d polarization functions are used, or 9 p functions?) The single "+" sign means that just one diffuse function is used for the O atom.
So, I think that the 6-31+G** for the water molecule equates to a total of 16 basis functions:

1s in oxygen: one LC of 6 GTOs
2s in oxygen: one LC of 3 GTOs + 1 GTO
2p in oxygen: one LC of 3 GTOs + 1 GTO (for each of px, py, and pz)
1s in hydrogen 1: one LC of 3 GTOs + 1 GTO
1s in hydrogen 2: one LC of 3 GTOs + 1 GTO
Diffuse: one diffuse basis function for the oxygen atom
Polarization: one polarised basis function for the oxygen atom
Polarization: one polarised basis function for the hydrogen atom
Total: 16

Is this correct? I do not feel confident carrying out this analysis, especially the point concerning how many polarization functions for the p/d-orbitals that should be used.


texts: What kind of metal drums are used to store Hydrochloric Acid?

texts:
I would expect Hydrochloric Acid to be stored exclusively in glass or plastic containers, but I was surprised to find Honeywell offers it for sale in 30Kg metal drums (Link).

I think Hydrochloric Acid would dissolve Nickel, Chromium and Iron in stainless steel, which leaves me wondering what kind of metal that could be, and whether this form of storage wouldn't (at least slightly) contaminate the acid?


texts:
I have some tantalum jewelry that I would like to clean. I've tried just soap and water to no success, so I wanted to try one of the standard at-home cleaning methods, like this one that uses foil, hot water, baking soda, and salt.

I know that tantalum is very non-reactive, so I would expect this to be safe to the metal, but I want to confirm before I accidentally do any damage. Unfortunately because tantalum is such a non-standard metal for jewelry, I haven't been able to get a straight answer from the internet or even the jeweler for whether this will be okay.

Is using the foil and baking soda method safe for cleaning tantalum jewelry? Are there any common cleaning methods that would be safe for most metal jewelry but not for tantalum?


texts:
What is a quadrupole moment of a molecule and how does it arise? How is it measured for a particular molecule?

I've read the Wikipedia article on quadrupoles and understand that it has to do with the distribution of charge, but I'd like a more chemistry-oriented explanation.


texts: Cerium electronic configuration change from 0 to +2 oxidation state

texts:
Cerium in $0$ oxidation state has electronic configuration

$$[\ce{Xe}]\mathrm{(4f)^1(5d)^1(6s)^2}$$

But when it gets oxidised to $+2$ state, it becomes

$$[\ce{Xe}]\mathrm{(4f)^2(5d)^0(6s)^0}$$

This is a change as in other elements in the lanthanides series get their $\mathrm{6s}$ electrons abstracted and the other shells remain at liberty.
Could you please explain this phenomenon to me? And also correct me if anything unsaid above was incorrect.


texts: How does heat and/or boiling remove vitamin C?

texts:
The www is full of crackpot claims about how various food treatments alter their nutrition content and it makes finding actual science very difficult.

I am specifically interested in the vitamin C content of orange juice.
From an answer I received in Biology SE (referencing Hodgins et al. 2002), pasteurisation of orange juice is unlikely to reduce the vitamin C content by more than 20%. This tallies with what I have been able to find on the reduction of vitamin C in milk by pasteurisation.

My question is twofold:

(i) What are the processes at work which remove some vitamin C during pasteurisation? Is it just the heat? What is the mechanism?

(ii) If I were to boil orange juice for 10 minutes or so, would that remove much more vitamin C and if so, why?


texts: Calculating molar solubility of calcium hydroxide from solubility product

texts:
On the Wikipedia page for calcium hydroxide, the stated solubility product for $\ce{Ca(OH)2}$ is $K_\text{sp} = \pu{5.5 * 10^{-6} M^3}$. It doesn't stipulate the temperature, but I have a chemistry book that says the exact same value for $\pu{25 ^\circ C}$.

However, when I calculate the solubility of $\ce{Ca(OH)2}$ in water using this value ($\pu{5.5 * 10^-6 M^3}$), I get a result of $\ce{0.082 g/100ml}$.

However, according to solubility tables on Wikipedia, calcium hydroxide is only this soluble at around $\pu{85 ^\circ C}$. How can this apparent contradiction be explained?


texts: Relation in the sign (+/-) for gyromagnetic ratio and magnetic susceptibility

texts: Is there a relation (or formula) between the sign of the magnetic susceptibility and the gyromagnetic ratio of a nucleus in NMR?


texts: Verify heat produced by flame using enthalpy of fomation

texts:
I'm simulating using a CFD solver a pure oxygen/methane flame. However, I doubt that the combustion model does not produce enough heat. The heat from reaction is defined by $S_h=-\sum_{j} \frac{h_j^0}{M_j}R_j $ with $h_f^0[J/kgmol]$ the enthalpy of formation, M$_j$ the molar mass and $R_j$ the reaction rate of species $j$. The integral of the heat is my simulation is around $50kW$.
I tried to calculate analytically the heat prodruced using the equilibrium equation $CH_4+2O_2\rightarrow 2H_2O+CO_2$. With the non-stochiometric molar flux $\dot{n_{CH4}}=0.9625mol/s$ and $\dot{n_{O2}}=1.059mol/s$ I know I should be able to calculate:
$\dot{n_{CH4}}h^0_{f,CH4}+\dot{n_{O_2}}h^0_{f,O_2}=\dot{n_{O_2}}h^0_{f,H_2O}+\frac{1}{2}\dot{n_{O_2}}h^0_{f,CO_2}+(\dot{n_{CH4}}-\frac{1}{2}\dot{n_{O_2}})h^0_{f,CH4}+\Delta H$.
There I'm getting $\Delta H\approx472kW$, which is a factor 10. Either my simulation is really wrong or my ethalpy calculation are nonsense...
Is this way of chemical calculation correct?


texts: Are the units of rate constants affected if we have more than one substance in the rate law

texts:
$$A+B \rightarrow C$$ $$rate = k[A] [B]$$
[A]= x mol of A/L
[B]= y mol of B/L
So why the unit of the rate constant is merely $$L/M$$ not having mol of A or mol of B?


texts: Non-carbon based life forms on hot planets

texts:
I am writing a story with people made of elements other than carbon. A couple of planets in this series are really hot, so I need compounds with high melting points.

For example, there is a lone girl who lives on Venus, which is hot enough to melt lead. I decided to use tungsten carbide for her house.

But on another planet, there are humanoids made of silicon who survive at higher temperatures than humans on earth.

Is this scientifically possible?

If you're interested in my book and don't mind a bit of self-promotion, watch for the next few years and keep an eye out for:

  The New Worlds Series #1: Into the Flames
The New Worlds Series #2: Call of the Cybans
Milky Fight #1: The Authority Gains Strength.


texts: How does the temperature of water affect the reactivity of alkali metals acting on it?

texts: There are a few experiments comparing the reactivity of alkali metals with cold water. Is there any purpose to use cold water? Does the temperature of water affect the reactivity of alkali metals?


texts: Does the activation energy depend upon the stoichiometric coefficient?

texts:
For the decomposition of $\ce{N2O5(g)}$ it is given that

  $$
\begin{align}
\ce{2 N2O5(g) &→ 4 NO2(g) + O2(g)} &\quad\text{activation energy} &= E_\mathrm{a}\\
\ce{N2O5(g) &→ 2 NO2(g) + 1/2 O2(g)} &\quad\text{activation energy} &= E'_\mathrm{a}
\end{align}
$$

  then

  (1) $E_\mathrm{a} = 2E'_\mathrm{a}$
  (2) $E_\mathrm{a} > E'_\mathrm{a}$
  (3) $E_\mathrm{a} < E'_\mathrm{a}$
  (4) $E_\mathrm{a} = E'_\mathrm{a}$

In the definition of activation energy, it doesn't say if that is the minimum energy required for 1 mole of reactant or otherwise. Can anyone help me understand this?


texts: If polar non-polar intermolecular forces are stronger, why do polar compounds elute first in GC?

texts:
I remembering reading that the interaction between a polar molecule and non-polar molecule is stronger than the interaction between two non-polar molecules.

However, in analytical chemistry classes, we are told that polar molecules elute first in a Gas Chromatograph that has a non-polar column. According to http://www.chem.ucla.edu/~bacher/General/30BL/gc/theory.html

  If the polarity of the stationary phase and compound are similar, the retention time increases because the compound interacts stronger with the stationary phase. As a result, polar compounds have long retention times on polar stationary phases and shorter retention times on non-polar columns using the same temperature.

These two concepts seem to conflict. Is there something else that is going on? Shouldn't polar compounds elute last even if the stationary phase is non-polar.

(Also sidenote: most mobile phases in Gas Chromatography are non-polar: helium, argon, or nitrogen)


texts: Schrödinger equation for multi-electron atoms

texts:
Does the Schrödinger equation alter its form when we apply it for an atom having a configuration other than hydrogen-like? I think it should happen because of difference in nuclear attraction and shielding effects.

If there is a change, how significant is that?


texts:
Why does methylene blue (which is initially blue) reduce to form a colorless solution?

I was told by my teacher that it has to do with the presence of an additional double bond on methylene blue, but I can't figure out or find any source on the internet that claims so.


texts: Stern-Volmer plot and calculation of rate constant for quenching

texts:
I did an experiment irradiating benzophenone in UV light and worked out the rate constant for the reaction. Then I repeated the experiment using various concentrations of a quencher and worked out their respective rate constants. Now I need to calculate the rate constant for quenching $k_\mathrm{q}$ using a Stern-Volmer plot. How would I do this?

The equation I have used before for the Stern-Volmer relationship is:

$$\frac{1}{I_\mathrm{f}} = \frac{1}{I_\mathrm{abs}}\left(1 + \frac{k_\mathrm{q}[\ce{Q}]}{k_\mathrm{lum}}\right)$$

where the x-axis is $[\ce{Q}]$, the concentration of the quencher, and the y-axis is $1/I_\mathrm{f}$, and to work out $k_\mathrm{q}$ you calculate the gradient/y-intercept = $k_\mathrm{q}/k_\mathrm{lum}$.

I think I would plot a graph of concentration of quencher $[\ce{Q}]$ on the $x$-axis against 1/rate constant on the y axis. But how would I work out $k_\mathrm{q}$?


texts: Why does the ionization energy decrease anytime the atom size increases?

texts:
I would like to have a better understanding of the relationship that exists between the Ionization Energy commonly known as IE and the size of an atom.

I think that the Ionization Energy can be defined as the smallest energy that is required to remove an electron from a gas phase atom.

Why does the Ionization Energy decreases when the atom size increases?


texts: Density of water increases from 273 to 277 K due to increase in entropy?

texts:
In a set of questions that I was solving, the answer to one of the questions asking why the density of liquid water increases from 0 to 4 degrees C had the above answer: due to an increase in entropy.

This website does explain this a bit with two thermodynamic equations, but I am unable to make sense of how entropy comes into the picture here. Please explain how the increase in density of water is due to an increase in entropy.


texts: What are the effects of frenkel and schottky defects on electrical conductivity of a solid?

texts:
How do these two defects impact dielectric constant of solid? Please explain these two questions in detail.
In case of frenkel defect the the smaller ions are just dislocated from their initial positions. In that case the electrical conductivity must remain unaltered. But I have found out from few sources that electrical conductivity decreases due to increase in resistance so I am a bit confused.


texts: What is the charge of the amino acid lysine at pH 2?

texts:
What is the charge of the amino acid lysine at $\mathrm{pH}=2$? $\mathrm{p}K_\mathrm{a}$'s are carboxylic: 2.18; amino: 8.95; side chain: 10.79.

The side chain of lysine is an amine group, so I assume that when fully protonated it has positive charge ($\ce{NH3+}$).

At $\mathrm{pH} = 2$, everything will be protonated because their $\mathrm{p}K_\mathrm{a} > \mathrm{pH}$.

This gives a net 0 (carboxy) + 1 (amino) + 1 (side chain) = +2 charge. Why do sites such as this say that at $\mathrm{pH} = 2$, lysine's charge is only +1, not +2?

There's probably something really simple I don't know. If anyone can help point it out, that would be great.


texts:
Would the Lewis Structure for OF+ be drawn so that the more electronegative atom has the more negative formal charge, or would it be drawn to satisfy the octet rule?

Here are my thoughts thus far:

For one, we could make the formal charge on the oxygen +1 and the formal charge on the fluorine 0, and give them a single bond, which would break the octet rule, but make sure that the more electronegative atom (fluorine) had a less positive formal charge. Oxygen would have 4 free electrons, and fluorine would have 6 free electrons.

However, we could also make the formal charge on the oxygen 0, and the formal charge on fluorine +1, and give them a double bond, which would be wrong in terms of electronegativity, but would mean full octets. Oxygen would have 4 free electrons, and fluorine would also have 4 free electrons

How do I decide?


texts: How do you handle manganese nitrate hexahydrate?

texts: So I wanna do an experiment using manganese nitrate and I bought manganese (II) nitrate hexahydrate $\ce{Mn(NO3)2.6H2O}$. But when I received it, it was kinda watery already (most part is still crystallized but there was also liquid in the bottle). After inspecting the bottle, it says that I need to refrigerate at 5 degree Celsius. But after I refrigerate it becomes icy hard, I cannot take anything out. So I am now wondering how to handle this compound. I am afraid if I use the liquid part it will have various concentration, and it is barely impossible to use the solid part because it's so hard. Thank you.


texts: What's the mechanism behind mineral oil loosening cyanoacrylate bonds?

texts:
Per industry literature I found that mineral oil is used to loosen out "super glue" and aid in removal from skin. I am exploring the chemistry of this loosening and I am intrigued. Please help me find which option applies here:

Does the mineral oil disturb the cohesive forces of the cured cyanoacrylate?
Does the mineral oil interact with the oil on the skin to loosen the cured adhesive and thus break the bond between skin and cyanoacrylate?
Does the mineral oil break the bond between the skin and cyanoacrylate by another mechanism?

Based on this answer, I am trying to find out if mineral oil will loosen the cured cyanoacrylate on a different substrate as well, namely PVC plastic. Please help!


texts: Why is gum so sticky and what chemicals make for easy removal of gum?

texts:
To give this question context, I work in a restaurant and sometimes I'm in charge of getting all of the gum off of the tables at work. Don't mind the work, but I'd be interested in hearing what makes gum so sticky and if there is any chemical I can use to make the cleaning a bit easier and why that chemical works.

I guess another backwards question is: Is there any chemical I can apply to the underside of tables that will prevent the gum from sticking? Would be awesome if I could fix the problem at the source and would be super interested in the chemistry behind it.


texts: What is the thermal state of a reaction at equilibrium?

texts:
I was asked this question at class,

  What is the thermal state of a reaction at equilibrium, the forward reaction of which, is exothermic?

I conjectured that since the forward (exothermic) reaction and the backward (endothermic) reaction occur at equal rates, the reaction at equilibrium would be athermic since there doesn't seem to be any net heat evolution. However, my teacher said this was not true.

Could someone tell me where I'm going wrong with my reasoning?


texts: Is it safe to store muriatic acid, hydrogen peroxide and acetone?

texts:
I am recently getting into PCB etching. So I use 10 M HCL solution, 3% hydrogen peroxide mixed in 1:1 ratio for my etchent. Currently, I am storing my HCL and hydrogen peroxide in my shed which can vary in temperature from -10 degrees Celsius to 25 degrees Celsius. The shed is outside my house. I also store my etchent next to HCL and hydrogen peroxide in the shed as well. Will it be safe to store all of these three chemicals inside a shed?

I do have metal tools in there but I don't care if it rusts. I am just afraid of hydrogen gas that might form because of HCL fumes. Also, I store my acetone indoor inside a plastic container because I heard that its flash point is -20 degrees Celsius. I don't want it to spontaneously catch on fire if I did store it in the shed. So are these storing method adequate or do I need more precautions.


texts: How do I calculate how much sodium hydroxide I need to add to get a new pH?

texts:
A 100 ml $\ce{HCl}$ solution has a pH of $3.7$. You want the solution to be of pH 4.5. You have a solution of $10\ \mathrm M$ $\ce{NaOH}$. How much $\ce{NaOH}$ do you need to add to to the $100\ \mathrm{ml}$ solution of $\ce{HCl}$ to get a pH of 4.5?

I firstly calculated the concentration $\ce{HCl}$ in $100\ \mathrm{ml}$ solution = $10^{-3.7}$ = $2.0\times10^{-5}\ \mathrm{mol}$ $\ce{HCl}$ per $100\ \mathrm{ml}$. After this I calculated the $\left[\ce{HCl}\right]$ of the new solution: $10^{-4.5}=3.16\times10^{-6}\ \mathrm{mol}$ $\ce{HCl}$ per $100\ \mathrm{ml}$ of new solution. Now I'm stuck.


texts:
Choose the molecule with the strongest bond: $\ce{F2, Cl2, Br2, I2,}$ or all are equal.

All of them are nonpolar-covalently bonded, so I had thought that the answer would be "all are equal". However, apparently, $\ce{Cl2}$ has the strongest bond, and I couldn't figure out why. Could someone help me understand this? Any help would really be appreciated.


texts: Why do square pyramidal molecules have only two vertical mirror planes?

texts: I would have expected molecules like IF5 to have 4, with two planes along the bond axes, and two planes bisecting the bonds. This is similar to how square planar molecules have four vertical mirror planes. However, apparently there are only two planes. Why is this? What am I misunderstanding?


texts:
From Tro's Chemistry: Structure and Properties [1, p. 93]:

2.5 Quantum Mechanics and the Atom
As we have seen, the position and velocity of the electron are complementary properties—if we know one accurately, the other becomes indeterminate. Since velocity is directly related to energy (recall that kinetic energy equals $\frac 1 2 mv^2),$ position and energy are also complementary properties—the more we
know about one, the less we know about the other. Many of the properties of an element, however, depend on the energies of its electrons. In the following paragraphs, we describe the probability distribution maps for electron states in which the electron has well-defined energy, but not well-defined position. In other words, for each of these states, we can specify the energy of the electron precisely, but not its location at a given instant. Instead, the electron’s position is described in terms of an orbital, a probability distribution map showing where the electron is likely to be found. Since chemical bonding often involves the sharing of electrons between atoms (see Section 4.2), the spatial distribution of atomic electrons is important to bonding.

The textbook says that electrons can exist in two states simultaneously. As I went further, I saw that an electron could exist as both a particle and a wave. So I thought that this must be the states that I was introduced to earlier, until I was learning about quantum mechanics.
In the text above, the writer was talking about electron states with well defined energy. From what I know the electron state that has well defined energy would be one with well defined velocity. And the velocity of an electron is associated with it's wave nature.
So, aren't we supposed to be dealing with electron as waves only? Or what exactly does the writer mean by the electron states?
Reference

Tro, N. J. Chemistry: Structure and Properties, 2nd ed.; Pearson: Hoboken, NJ, 2018. ISBN 978-0-13-429393-6.


texts: Can you find [SO₃²⁻] with just the two acid dissociation constants Kₐ₁ and Kₐ₂?

texts:
Sulfurous acid, $\ce{H2SO3}$, is a diprotic acid.
\begin{align}
K_{a1} &= 1.6 \cdot 10^{-2}\\
K_{a2} &= 6.4 \cdot 10^{-8}\\
\end{align}

Is it possible to find the concentration of $\ce{SO3^2-}$ from this?

I would think you would need to know the concentration of at least one thing. It is like trying to solve for 3 unknowns with 2 equations!


texts: Chemical Structures as Graph Labels in R

texts:
I asked the following question here https://stackoverflow.com/questions/56236135/chemical-structures-as-graph-labels-in-r but I ask it here for a different perspective.

I want to make a plot that labels a point with the chemical structure represented by the value at that point.

In the example below I have a plot of melting points which are labelled by the smiles strings of the molecules.

chem_data <- c(40.5, -6.3, -44)

names(chem_data) <- c("c1ccc(cc1)O", "Nc1ccccc1", "Fc1ccccc1" )

plot(chem_data, main="Example Plot\n Labelled with Smiles String", ylim=c(-50,50), xlim=c(0,4),
     ylab="mp /°C")

text(chem_data, labels=names(chem_data), cex= 0.7, pos=1)

How do I label the points with the chemical structures rather than the smiles strings?

Can R generate the image of the chemical structure from the smiles string?


texts:
1 mol of acetic acid and 1 mol of ethanol was mixed to react at a constant pressure to reach the equilibrium, and 0.75 mol of water was found in the product.
A. Calculate the equilibrium constant of this reaction at the above temperature
B. At the same temperature, 1 mol acetic acid, 1 mol ethanol, and 4 mol of water were initially mixed to react. Calculate the amount of ethylacetate product after the mixture has reached equilibrium.

A. The equilibrium constant = 9
B. I thought that 4 mol of water reacted with previous product of acetic acid and ethanol so there are 2 mol of acetic acid and 2 mol of ethanol now. I get ethylacetate is 1.5 mol.  The answer is 0.5 mol
How is the reaction actually react?


texts: A compound that only absorbs UV-A radiation

texts:
As a similar idea to the question A compound that absorbs all visible light, I am curious if there is a compound (or compounds) that absorb UV-A radiation (shown below)?

However, preferable the compound would have relatively good transmission in the UV-B and Visible wavelengths.

Image source


texts:
I've heard that, even though according to Molecular Orbital Theory there is no chance of having nobel gases bonded to each other, it is not totally impossible. For example, under extreme conditions, Ar2 can be synthesised.

So I am wondering whether a carbon can make 5 bonds if the required conditions are provided.


texts: Increasing temperature in system of dynamic equilibrium

texts:
According to the article Summary of Le Chatelier's Principle on dynamicscience.com.au, for the process

  $$\ce{N2(g) + 3 H2(g) <=> 2 NH3(g)}\quad ΔH = \pu{-92 kJ/mol}$$

the forward reaction is exothermic, while the reverse reaction is endothermic.

If the forward reaction is exothermic, increasing temperature decreases $K,$ because it drives the equilibrium backwards, in order to absorb the heat energy.

However, in the graph, there is an abrupt change in the reaction rate of forward and reverse reactions. Why does the forward (exothermic) reaction rate rise up so abruptly, while the reverse (endothermic) reaction does not go up so high?

Shouldn't it clearly be the opposite, as increasing temperature favors the reverse reaction?


texts:
So I have a few dumb questions. I'm still in high school and am doing something on magnetic properties of transition metals. I'm facing a few roadblocks.

1) What're compounds like $\ce{CoBr2, CoCl2, AgI, AgBr, AgCl, AgF, MnBr, Co(CN)2}$, supposed to be? Are they the same as the coordinate complexes in something like $\ce{[Fe(H2O)6]}$?

2) If they're not, how do they bond with halogens like $\ce{Cl}$ or ligands like $\ce{OH/CN}$? Is it similar to ligand interaction and d-orbital splitting?

3) If they're neither complex ions nor have split d-orbitals, what determines their magnetic properties?

I'm having a bit of trouble finding the answers. I'm very new to this whole transition metal thing. On some websites compounds like ferrous bromide is considered a and on another it's b. I'd appreciate any help!


texts: How to measure ratio of Na to K in table salt?

texts:
Some people state, that the salt which we buy at the supermarket contains too much potassium chloride. For me it seems to be a hoax, but I want to have a proof.

Is there any way to measure the percentage of sodium chloride and potassium chloride in salt at home without special equipment?

If it is not possible, what kind of equipment is needed?


texts: Should I expect any surprise when trying to shoot green fireballs like this?

texts: I wanted to use flash cotton (nitrocellulose) to ignite fireballs with an electric trigger. In order to make green fireballs, my attempt will be to put some drops of boric acid solution on each (nitrocellulose) projectile. Should I expect any... "surprise" there? (e.g. the compound exploding by itself in that moment).


texts:
Is astatine a non-metal or a metalloid?

A metalloid is an element which exhibits some of the properties of a metal as well as those of a non metal.


texts:
The concentration of $\ce{SO2}$ in the atmosphere over a city on a certain day is $\pu{10 ppm}$. Given that solubility of $\ce{SO2}$ in water is $\pu{1.3653 mol L-1}$ and $\mathrm{p}K_\mathrm{a}$ of $\ce{H2SO3}$ is $1.92,$ estimate $\mathrm{pH}$ of rain on that day.

$\pu{10 ppm}$ means there is $\pu{10^-2 g}$ of $\ce{SO2}$ in $\pu{1 L}$ of air. This accounts to $\pu{1.25E-4 mol}$ of $\ce{SO2}$ in $\pu{1 L}$ air, which is less than its solubility, which means that all this amount will be dissolved in rain water to make $\ce{H2SO3}.$

Now, using the expression $\frac{4c^2α^3}{(1-α)}$ for $K_\mathrm{a}$ expression of $\ce{H2SO3},$ and substituting $c$ as $\pu{1.25E-4},$ I get $α$ to be approx. $0.99.$

Then $[\ce{H+}]$ is $2cα,$ which comes out to be $\pu{2.475E-4}.$ So $\mathrm{pH}$ is $3.606.$ But the answer given is $4.865.$ Why I am wrong?


texts: What is the definition of of 'compound', 'mixture', 'element' and 'molecule'?

texts:
I am looking for the precise definitions, as I am very confused as to what they are exactly because although I mostly understand what they mean, I have encountered some conflicting definitions that confused me.

As it stands, this is what I understand them to mean:

  Compound: two or more different atoms bonded together.
  Mixture: two or more different atoms together but not joined.
  Molecule: two particles (same or different) bonded together.
  Element: only 1 type of atom; this definition is applied to things both bonded and not to itself.

I don't know whether these terms apply microscopically, macroscopically, or both. For example, I think 1 $\ce{H2O}$ molecule is a compound but is a bathtub of them called a mixture (as it contains more than 1 atom type), a compound, or both? That is, to be a compound, do all the atoms in the compound have to be bonded physically together? Generally, to what extent can these four terms overlap?

I would very much like a systematic way of thinking about these terms.


texts:
Are there any chemistry spreadsheet-like software that:

Generates 2D structure for the entered compounds (based on name or SMILES)
Easy to search and create customized reports (such as similarity search)

that preferably runs on linux and is not too expensive?

I'm aware of ICM Chemist and JChem for Office (Windows), and I'm wondering if there are any other alternatives available.


texts: Reference states for molecular orbital energies in DFT calculations

texts: When doing a population analysis using density functional theory (specifically as implemented in Gaussian), what are the orbital energies (i.e. alpha and beta eigenvalues) with respect to? If I have two different but closely related compounds, can I directly compare their HOMO (or LUMO) energies? It should be noted that I am not referring to comparing their HOMO-LUMO gaps, but rather the energy of a single molecular orbital.


texts: How does Dichlorofluoromethane get into the stratosphere?

texts:
I was wondering why FCKWs can destroy the ozone layer.
It seems like these gases have a high molecular weight in comparison to $\ce{N2}$ or $\ce{O2}$.
How can these gasses come up to the outer layer of our atmosphere? In particular, how long (on average) would it take to get to such an altitude (through the diffusion of such a particle)?
I mean, they are basically several times heavier than all the other components of our atmosphere combined. Hence, it shouldn't be very energetically stable for them to float on the outer layers of space on top of other lighter particles.


texts:
Can anyone tell me where I am doing it wrong for the following reaction?

In the first step, Br should be attached to the alpha carbon.

In second step, the bromide is replaced by cyanide.

I am able to get the third product that is final compound.


texts: Do Palladium(II) Chloride and Palladium (III) Chloride follow 18-Electron rule or octet rule? How to determine this?

texts:
Does $\ce{PdCl2}$ follow 18-Electron rule or octet rule?
How should we determine this?

http://pubchem.ncbi.nlm.nih.gov/compound/24290#section=Top

http://pubchem.ncbi.nlm.nih.gov/compounds/3494742#section=Top


texts: Do there exist metals that are composed of molecules?

texts:
Most metals are composed of pure elements or are alloys (mixtures of pure elements.)

Are there metals that are composed of one type of molecule that is metallically bonded together?

The difference between a metal that is composed of one type of compound and an alloy is that in an alloy different elements are attached by metallic bonding but in a metal composed of one compound covalent or ionic bonding attaches multiple atoms together into compounds and then these compounds form metallic bonds with each other.

I have read that Gallium in its pure elemental state forms pairs which are then metallically bonded together which sort of is what I'm wondering about except that I'm wondering if metals can form out of more complicated compounds.

I would also expect there to be a lot of compounds which on their own do not form metals but do not degrade the metallicity of alloys they are put in very much.

I think a more specific and low level question might be: are there covalent compounds that can make metallic bonds with other things?


texts: Position of nodal planes in molecular orbitals

texts:
From the attached picture (MO diagram of cyclopentadienyl anion) I can figure out where the nodal planes are, but why are they exactly at these positions?

Why is this nodal plane invalid?


texts: A thermodynamics problem with an interesting equilibrium condition

texts:
Usually, when we analyze reactions, we assume that the reaction takes place at constant pressure or at constant volume. But there is no reason to assume this is generally the case, and so my friend posed the following question that has a different condition:

$n=0.1$ mols of $\ce{SO3}$ are put into a container of volume $V_0 = 3\pu{L}$ at temperature $T=1100\pu{K},$ and reaches an equilibrium mixture with $\ce{SO2}$ and $\ce{O2}.$ The temperature is held constant at $T$ and the quantity $V - c\cdot P$ where $c = 20 \frac{\pu{L}}{\pu{bar}}$ is always constant during the reaction. Assume everything is ideal. Use any reference data as appropriate. What are the equilibrium concentrations of all compounds?

First, for the thermodynamic constants, it is not hard to find their values at 1100 K from the reference ones at 298 K simply by using   their relation with temperature and heat capacity. I get that $\Delta H = 95.6\pu{kJ}$ and $\Delta S = 99.3\pu{J/K}$ when one mol of $\ce{SO3}$ decomposes.
Ordinarily, in constant volume or constant pressure scenarios, we can find the equilibrium concentration simply from the equation $\Delta G = - RT \ln K$ or $\Delta A = - RT \ln K$ and then use known values of Gibbs/Helmholtz formation enthalpy to calculate the concentrations. But here, neither of these equations apply since neither volume nor pressure is constant.
From the condition of ideality it is not hard to derive a formula for the volume and pressure with respect to the extent of reaction $\xi:$
$$P_0 = n\cdot R\cdot\frac{T}{V_{0}}$$
$$V_1 = \frac{V_{0}-cP_{0}+\sqrt{\left(V_{0}-cP_{0}\right)^{2}+4RTcn\cdot\left(1+\frac{1}{2}\xi\right)}}{2}$$
$$P_1 = n\left(1+\frac{1}{2}\xi\right)\cdot R\cdot\frac{T}{V_{1}}$$
but I'm not sure how to proceed in this problem afterwards. One thought I had was to maximize total entropy, but this seems quite hard to set up.


texts:
The periodic table I understand is arranged by order of increasing atomic number after Henry Moseley's X-ray experiment.

But I also learned that the periodic table also has its shape due to the types of subshells present in certain sections called blocks of the table.

However, I still do not understand who shaped the modern periodic table so it mimics the filling of lattermost subshells of atoms of each element (in order of increasing number of electrons- from left to right as well as top to bottom for the elements.)

My Question is : was the periodic table Mendeleev and Moseley devised not in a shape that can be used to predict the filling order of each elements, and that the periodic table was later adapted to fit this concept of orbitals in?


texts: What is the mechanism of the uncatalysed epoxide opening with alcohols?

texts:
The Wikipedia page says this:

  Ethoxylation is an industrial process in which ethylene oxide is added to alcohols and phenols to turn it into a surfactant.

How does the reaction proceed?

The answer to the question "Do epoxide rings react with bases?" regarding epoxide rings reacting with bases does not include alcohols, and does not answer my question.


texts: Pyranose v/s Furanose form of Glucose and Fructose

texts:
According to my textbook (Class 12 NCERT Chemistry):

Fructose also exists in two cyclic forms which are obtained
by the addition of —OH at C5 to the C = O group. The ring, thus formed
is a five membered ring and is named as furanose with analogy to the
compound furan.

I understood why the pyranose structure for glucose is more stable than the furanose structure ( The pyranose form has the perfect 60° dihedral angle between two non-ring atoms which minimises this type of strain Source: Stability of furanose vs. pyranose form of glucose?). But I do not understand why the same cannot be applied to the fructose structure.
So, to summarize : Why is fructose present in furanose form and not in pyranose form?


texts: What does the Clausius Inequality mean in thermodynamics? (entropy)

texts:
$$\delta S\ge\frac{\delta q}T$$

I don't understand how a quantity (the change in entropy in this case) can be greater than the very thing that defines it ($\mathrm{\frac{\delta q}{T}}$).

Also what is the significance of this inequality?


texts: Relative importance of electronegativity and bond length for dipole moment magnitude

texts:
In this answer to the question "Why is the dipole moment of chloromethane larger than the dipole moment of fluoromethane?", the order of the dipole moments was given as $\ce{CH3Cl > CH3F > CH3Br > CH3I}$, with an explanation that bond length is also a contributing factor; specifically, electronegativity dominates for $\ce{Br/I}$ and bond length/order dominates for $\ce{F/Cl}$.

Can more detail be given as to why there is this division between $\ce{F/Cl}$ and $\ce{Br/I}$?
In general, is there a method to determine which effect (electronegativity or bond length/order) is more important for comparing the magnitude of dipole moments?


texts: Creating ethane through electrolysis of vinegar

texts:
Some
 sources that I studied say that it is possible to produce ethane
through the electrolysis of ethanoic acid. Would this work with vinegar
(5-10% acid)? Also, other sources say that ethanoate salts should be used.
 I can easily obtain such salts (sodium hydrogen carbonate (baking soda)
 + ethanoic acid (vinegar)), and vinegar as well, so which one is better
for creating ethane? I don't care about the amount of carbon dioxide,
oxygen, hydrogen or any other gas produced.


texts: Difference between Tishchenko reaction and Meerwein-Ponndorf-Verley reduction

texts:
For the Tishchenko reaction, Al(OEt)3 is used as reagent where an aldehyde is oxidized as well as reduced, so it's a redox reaction.
Whereas in Meerwein-Ponndorf-Verley reduction, an aldehyde is converted to secondary alcohol and acetone with the same reagent and this reaction is reversible with the Oppenauer oxidation.
So, my question is what is the difference between these two reactions i.e what is the difference in mechanism of this reaction that lead to different products or there are some different conditions other than the reagents which changed their products?


texts: What are all products of an ozonolysis of alkenes using zinc and water?

texts:
I'm studying ozonolysis reactions in alkenes, and saw that in one of them there is the formation of $\ce{H2O2}$ (Can anyone explain from where?) that I presumed that reacts with $\ce{Zn}$, one of the reagents, as the following:
\begin{align}
\ce{2H2O2 &-> 2H2O + O2}  \\
\ce{2H2O + Zn &-> Zn(OH)2 + H2} \\
\hline
\ce{H2O2 + Zn &-> Zn(OH)2}
\end{align}

The general reaction is
\begin{align}
\ce{Unsaturated~compound (-C=C-) + O3 &-> Ozonide\\\\
Ozonide + Zn &-> R^1-(C=O)-R^2 + R^3-(C=O)-R^4 + X}
\end{align}

But one of my books shows that this $\ce{X}$ is $\ce{Zn(OH)2}$ only and other $\ce{ZnO}$ only. What about this? What am I doing wrong?


texts: What is the meaning of the "-osic" suffix on a metal (e.g., cobaltosic oxide)?

texts:
I just came across the term cobaltosic for the first time in the abstract of Ind Eng Chem Res 52(18): 6076, 2013 (emphasis added):

  A nanocomposite of cobaltosic oxide and nitrogen-doped graphene ($\ce{Co3O4}$/N-G) was prepared by the facile hydrothermal method.

I assume this is a historical name; Wikipedia's article on the cobalt spinel mentions cobaltosic oxide as an "other name", but provides no other historical information.  Google searches on manganosic oxide and ferrosic oxide turn up the sort of results I would expect, though not all consistent:

Manganese

Analogous to cobalt, manganosic oxide appears to be the $\ce{Mn3O4}$ spinel; e.g., see the abstract here (PDF at link).

Iron

The term ferrosic appears to refer (at least) to a mixed-oxidation state hydroxide, $\ce{Fe3(OH)8}$; e.g., here.
However, it is also used to refer to the iron $\ce{Fe3O4}$ spinel (magnetite); e.g., here.

What is the meaning of this "-osic" suffix?


texts: Is the titration of sodium carbonate with hydrochloric acid temperature dependent?

texts:
I am a chemistry teacher in a Cambridge school.
In one of the titrations of sodium carbonate with HCl, there was one question asked:

  On heating the sodium carbonate solution before doing the titration, is there any change in the observation/reading?

My opinion is that the rate of reaction will increase due to more collisions among particles due to the temperature change. So the time to completion of the titration should be shortened.

However, the CIE mark scheme suggests that there is no effect, as the concentration remains same.


texts:
Question:
Assign the R/S configurations to the carbons which are attached to different rings of this molecule (carbons 1 and 3 according to IUPAC numbering):

My Solution
I first started out by numbering the carbons. The one at the top would be 1 and the bottom chiral carbon would be 3. Next, According to CIP rules, I have included the phantom atoms by replacing the double bonds while deciding the priority order. Moving on, at carbon 1, My priorities would be:

$\ce{-OH}$
Cyclopentene ring (on the left)
Cyclopropene ring (on the right)
Carbon 2

This gives me a counter-clockwise turn and since the least priority group is on the vertical line (away from us) the configuration I assign would be S.
Following a similar procedure for carbon 3, The priorities would be :

Bottom 5-member ring (contaning $\ce{O-O}$ bond)
3 member ring on the right
5 member ring on the left
Carbon 2

Again, this gives me a counter-clockwise turn and since the least priority group is away, I would assign the configuration: S.
The answer key, however, says that the answer is 1R, 3S.

Where am I going wrong?


texts: What's the relationship between chemical polarity and vapor pressure？

texts:
A question which confuses me now.
Chemical polarity is one of microscopic properties for certain molecules.
Vapor pressure is a macro thermodynamic properties for certain materials.

But I often read about some violate organics are polar material. So, it has a  relatively small vapor pressure and  hard to evaporate.

How to connect these two concepts together? If I can access the volatile ability based on the polarity, it will help me to recognize some kind of VOCs which are eager to condense into particle phase.


texts:
What's the mechanism of cross-linkage for a typical household 2-party epoxy mix? I was working with some epoxy the other day and I was instructed to mix equal parts of epoxy and epoxy hardener. Stoichiometry at its finest.

The hardener contained "polymercaptans amines" according to the label. Google told me that a mercaptan is a broad name for a class of thiols. Makes sense; the $\ce{-SH}$ group is likely strongly nucleophilic (to better pop open the epoxide rings). Amines contain the also nucleophilic $\ce{-NH2}$ group.

However, what are polymercaptan amines? Do these contain both thiol and amine functional groups? And again, how does cross-linkage work? I presume that this involves opening the epoxide ring. But then does the resulting oxide anion attack another epoxide ring? Wouldn't we then need a 2:1 ratio of epoxide to hardener?


texts: Mass percentage of potassium chlorate in decomposition reaction

texts:
When heated, a $3.40\ \mathrm g$ sample mixture of $\ce{KClO3}$ decomposes and produces $685\ \mathrm{cm^3}$ $\ce{O2}$ gas at $30\ \mathrm{^\circ C}$ and $101\ \mathrm{kPa}$. What is the mass percentage of $\ce{KClO3}$ in the mixture?

What I've done so far is write out a balanced equation which is:

$$\ce{2KClO3 -> 3O2 + 2KCl}$$

Where do I go from here?


texts: Volume change in positive deviation from Raoult's Law

texts: Let us take a mixture of ethanol and acetone as an example. When ethanol is mixed with acetone, the hydrogen bonding between ethanol molecules gets disturbed as actone molecules get in between the ethanol molecules. This results in $\Delta_\text{mix} H\gt0 $ as heat must be supplied to make the solution from its constituents (as attraction is less) but I am not sure about $\Delta_\text{mix} V$. This page says it is greater than zero because volume expands on mixing. But I think it should be less than zero because the observed vapour pressure is more than that predicted on the basis of theoretical calculations, so a greater amount of solution will be present in the form of vapour, hence volume of solution will be less (than the sum of the volumes of its constituents). Where am I wrong?


texts: Energy of emitted photon in Bohr's model

texts: In Bohr's model for hydrogen atom, the energy of photon emitted by an electron is equal to the difference in potential energy of electron in the two orbits. I do not understand this part. Shouldn't we take the difference of total energy of electrons for the two orbits? Since the total energy of electron in any orbital is half the potential energy, shouldn't the energy of the emitted photon be half the change in potential energy?


texts:
I'm a crafter who likes to make her own body oils and butters but I have no background in chemistry. Now, I just read something about propanediol (which I'm considering for modifying the feel of my anhydrous product) and on one site it says that in appearance it is a clear colourless  oil but then it also mentions it's solubility is in water.

Confused.

So, I want to know how it can be an oil and be soluble in water, but more importantly, I want to know if this means it's not soluble in oil and hence I can't use if for my anhydrous product?


texts: Is there an electrolyte that will halt the production of Hydrogen in water electrolysis?

texts:
Care must be taken in choosing an electrolyte, since an anion from the electrolyte is in competition with the hydroxide ions to give up an electron. An electrolyte anion with less standard electrode potential than hydroxide will be oxidized instead of the hydroxide, and no oxygen gas will be produced. A cation with a greater standard electrode potential than a hydrogen ion will be reduced in its stead, and no hydrogen gas will be produced.

From what I understand, that bit states that certain electrolytes will stop the production of hydrogen gas and only oxygen gas and whatever gas from the electrolyte will be produced.

So I have two questions:

What are some electrolytes that will stop the production of hydrogen gas in water electrolysis?
What kind of water will be left behind if distilled water and an aforementioned electrolyte runs through electrolysis until all of the oxygen has been exhausted from the solution?

Please correct me if I'm misunderstanding anything.


texts:
In a recipient there is an unknown monoatomic gas that occupies a volume of $\pu{230 cm3}$, at $\pu{300 K}$ and $\pu{1 atm}$. It is known that the atoms occupy a volume of $2\times10^{-4}$. Find the radius of the atoms.

I used the ideal gas law to calculate the number of moles, then I calculated the number of atoms, then divided the volume occupied by the atoms by the number of atoms to find the individual volume of each atom, then applied the formula for the volume of a sphere to find the radius, the problem is that I found 92x10^-10 and the correct answer is 1,25x10^-10, can anybody spot the mistake? Thank you.

Here are the maths I did:


texts: Zinc evaporation/toxicity at room temperature

texts:
I have a (slightly embarrassing) question regarding zinc powder.

I have recently broken an old mercury thermometer, and read that I can handle the mercury with powdered zinc - so I've sprinkled some on my floor. Too much probably. It turned out that unfortunately the powder is then quite hard to get out of the particular material of my floor (wood). I got out as much as possible, but I think there's still some left. So now I'm wondering if there is some danger if having all that zinc laying around.

Thanks anybody for the answer :)


texts: Programs for chemical structure visualisation and drawing 2d and 3d

texts:
I want to create list of simple and useful software to draw molecules 2d and 3d with small description. Not necessary only freeware software. Also web-based services are interesting.

Your help in improving this list is greatly appreciated. I will continue this list and add more information with some pictures.
If you know some usefull and easy software, please, write about it!

Web-based freeware site chemicalize.org
Free. Cross-platform.
It does not require installation of java or flash, as output/input can be drawn by hand, SMILES srting, IUPAC name, some molecular geometry file formats.

Web based freeware site chemspider.com
Free. Cross-platform.
It searches by IUPAC name, SMILES, can be drawn by hand, but there is HUGE limitation - it searches only existing molecules, but shows some useful information about compound.

http://molview.org/ web-based
VMD - freeware open-source program from University of Illinois
Free. Cross-platform.
This program mostly for visualization, but has some building features. Can be run under any OS. Opens a lot of different formats. GUI is not very friendly for the beginners. Used mostly for visualization large molecules (proteins, membranes), molecular dynamics simulations (especially from NAMD).

Mercury - Crystal Structure Visualisation, from The Cambridge Crystallographic Data Centre (CCDC)
Free. Cross-platform.
New freeware version has some limitations - not possible to calculate distance to the plane (now it is feature for paid version). It can open/save a lot of chemical structure format files, all OS are supported.
Chemcraft
Free trial. +Academic discount. Windows/Linux (works fine under wine).
Basically is non-free version (there is quite long trial period and there is old free versions through internet without any restrictions). Is one of the simplest and easiest 3d drawing programs. There are versions for Windows/Linux and under Linux/Mac OS it is possible to run under wine.
BIOVIA Draw (old name Accelrys Draw - successor of ISIS draw)
Free  for Academic and Non-commercial Use. Windows.
Only windows (can't say yet about working under wine). Mostly 2d drawing software, can wok with a lot of different formats, also supports 3d visualization.
Avogadro
Free. Cross-platform.
Molecular builder/editor. Drawing is not the best, but has built-in optimisation tool. Opens/saves a lot of formats, useful for preparing inputs for quantum-chemical calculations. Fast and simple.
Openbabel
Free. Cross-platform.
Read, write and convert over 110 chemical file formats. Free cross-platform format converter.
Marvin Suitefrom ChemAxon
Free. Cross-platform.
Very good 2d/3d drawing software supports a lot of formats. Easy and useful.
ISIS/Draw
Free. Windows.
Very old drawing software. Support most common formats. Incompatible with some new drawing formats. Possible to download in the internet.
ChemDoodle
Non-free. Cross-platform.
Has a lot of features bult-in. 2/3d drawing. Has applets for phones.

I am asking about software you are using - I haven't tried all possible software.


texts: Reaction of barium peroxide forming barium carbonate

texts:
I stumbled across this reaction:

$$\ce{BaO2 + H2CO3 -> BaCO3 + H2O2}$$

This reaction seems quite similar to the variant with sulfuric acid

$$\ce{BaO2 + H2SO4 -> BaSO4 + H2O2}$$

which is well known and works.

But as carbonic acid is a lot weaker than sulfuric acid, I started to question this reaction. Why does it even proceed in the first place? I thought that the sulfate/carbonate is really insoluble in water which is why no equilibrium forms (or does it?), however barium peroxide is itself pretty insoluble.

So, a) does the first reaction even happen and b) why?


texts: Does the temperature during ice melting change?

texts:
I did an online test for physics and one of the questions was: Salt was added to ice. Because of it the ice melted. What was happening with temperature DURING the process of melting?   The right answer was that temperature was lowering.
Can please someone explain why? I always thought that during melting the temperature is constant and after all ice is melted then the temperature changes.
Thank you very very much


texts: Why is there a difference in available energy in saturated vs. unsaturated fatty acids?

texts:
On Wikipedia it states:

  In cellular metabolism, unsaturated fat molecules contain somewhat less energy (i.e., fewer calories) than an equivalent amount of saturated fat.

Can someone explain why that is true in simple words? (that is, if possible, in a way understandable by someone who is not conversant with biology nor chemistry)


texts: Why hydrogen peroxide sizzles in the bathroom sink?

texts: Extremely short question. I pour a bit of hydrogen peroxide in my bathroom sink and it starts to sizzle, almost the same way it does on the open wound. Why? What elements in there it reacts with?


texts: What should be the order of specific conductance (κ) of floride, chloride and bromide ions?

texts:
The equivalent conductance order is $\ce{Br-} > \ce{Cl-} > \ce{F-}$.

$$Λ = \frac{κ}{c},$$

so $Λ$ is proportional to specific conductance?

But in ion chromatography we get peak area where $\ce{F-} > \ce{Cl-} > \ce{Br-}$ (specific conductance, μS/cm) for the same concentration, let us say 1 ppm.

Why?


texts: Why cooling an exothermic solution it increases it's solubility?

texts: In my chemistry book writes that cooling an exothermic solution(e.g. $\ce{NaOH + H2O}$) increases it's solubility, and I can't understand why since the cooling should decrease it.