texts:
I know some the basic kind of strains that can exist in molecules namely Torsional strain (Vanderwaals' strain), steric strain and angle strain.

Is it possible to associate a particular type of strain that causes the majority (and the strain that causes least) of the instability to the molecule eventhough all of the types of strains could possibly exist in that conformation of cyclohexane?

  For example: I was taught that in the twist boat conformation of cyclohexane, the torsional strain is approximately zero but angle strain is huge making this form unstable.

What would be corresponding most and least contributor of strain for chair, half-chair and boat conformations of cyclohexane?


texts: Relationship between ionization energy and orbitals

texts:
My chemistry book says that the ionization energy depends on the orbital an electron is taken from?

I'm not sure I understand what it means. Could someone please explain this?


texts:
While studying atomic orbitals and nodes, the only illustration of a radial node that I could find is in an s-orbital (like here). How do the radial nodes look like in p or d-orbitals?
(I don't know how to plot the distribution myself.)


texts: Among hydrogen, helium and carbon dioxide, which gas would behave most like ideal gas and why?

texts:
I was wondering which gas would behave most ideally out of $\ce{H2},$ $\ce{He},$ $\ce{CO2}.$ All gasses are in the same condition.

I know the answer is either $\ce{H2}$ or $\ce{He}$ because of London dispersion forces. I was wondering which one it was and why.


texts:
In this question the answer key given is A and C. But i think that D should also be wrong because equivalents = molecular mass / n factor = $\frac{90}{2} = 45 \neq 40 $

I believe I am correct but I may be wrong so can someone please help me clarify my question.


texts: Why does Carnot Engine have the curves as isothermal and adiabatic?

texts: Why exactly does the Carnot engine have two isothermal and two adiabatic curves? (My book says that “a process is quasi-static if the temperature difference between the system and the reservoir is infinitesimal. Hence it is isothermal. For the connecting two isotherms ;only reversible adiabatic is suitable. If(say) it were isochoric then we shall need a series of reservoirs in the temperature range defined by the two reservoir and the sink” .I don’t get it. Please help.


texts: When should we not draw a Lewis dot structure?

texts:
My friend once told me that technically , we should not draw Lewis dot structure of molecules containing no central atom(for example for benzene,
acetic acid).
Is there an explanation for this?


texts: Can the electrons be above the Fermi level(in a band gap)?

texts:
I've been searching this online for some time. It seems to be ignored most of the time but I found this on one website and I'm just trying to confirm it's true.

  Note that although the Fermi function has a finite value in the gap, there is no electron population at those energies (that's what you mean by a gap).

From the little I understood the Fermi function gives the probability to find an electron at a specific energy level. At temperature above 0 Kelvin f(E) is as shown above, meaning that there is a chance of finding an electron at an energy level in the gap. But then the website states that electrons can't occupy any state in the gap. If that is true the probability would be zero..


texts: IChO problem involving the condensation point of NF3, NHF2, NH2F

texts:
This is a problem from the 2016 International Chemistry Olympiad (IChO):

  Which of $\ce{NF3}$, $\ce{NHF2}$, and $\ce{NH2F}$ condenses at the lowest temperature?

The answer book says that it is $\ce{NF3}$. But I don't understand why. In $\ce{NF3}$, $\ce{N}$ should have the greatest positive charge of the three molecules; therefore, it should have the highest b.p., no?

Maybe the answer lies in somewhere in the geometry of ions. Can't figure out what. Any hint?


texts:
I'm trying to model  $\mathrm{p}$ orbitals using a 3D program. What confuses me is that there are 2 shapes of $\mathrm{p}$ orbitals. I'm not sure which one is the accurate model. And what is the reason to have 2 types of shape?

Shape 1

Shape 2


texts: Modeling the dissolution of an oil droplet with detergent

texts:
How to model the dissolution of an oil droplet on the surface of water when a detergent is (gradually) added to the water?

I believe this includes an interplay of coalescence keeping the droplet together and dissolution tearing it apart. Adding the detergent then changes the system so that the dissolution becomes stronger.

So far I tried a partial differential equation approach with the Cahn–Hilliard equation. However this model seems not to account for the coalescence, so that the droplet is always dissolved regardless of the parameters.


texts: What colour is clearish orange vitamin C solution supposed to change to when dark blue DCPIP solution is dropped into it?

texts:
I'm doing an experiment to study the effects of heat on vitamin C content.

I planned to titrate DCPIP (2,6-Dichlorophenolindophenol, Tillmans' reagent) solution into a fixed volume of vitamin C solution heated at different temperatures.

Basically I thought, the more DCPIP I used, the higher the vitamin C content.

I know DCPIP will turn pink  when acid like Vitamin c is dropped into it, then colourless once it's oxidized.

If my research is correct, the reverse should happen if I drop DCPIP into vitamin C; it's colourless or the colour of vitamin C, then once all the vitamin C has been oxidized the vitamin C turns blue because DCPIP is in excess.

However, when I tried it out, even in very small volumes of Vitamin C and large volumes of DCPIP, the solution doesn't change colour. Could anybody tell me the possible reason for this?

Perhaps I have made an error or my assumption is completely wrong. Please help.


texts:
A maybe (hopefully) simple question about the denotations of "anode" and "cathode". The below image is a schematic of a polymer solar cell (Source (WBM)). (The figure text is quoted as well for the sake of context).

My question is only about the naming of electrodes. Isn't it correct that

the cathode is the reducing electrode, which supplies electrons, while
the anode is the oxidizing electrode, which accepts electrons?

Why would electrons (black spheres) move towards the negatively charged cathode, while positive holes (white spheres) move towards the positively charged electron-absorbing anode? Wouldn't the opposite make sense?

Is it a mistake on the drawing or should I re-think my understanding of the terms "anode" and "cathode"?

  Figure 1. The working principle of the solar cell. Light enters the cell through the transparent anode, and is absorbed in the bulk heterojunction layer through generation of excitons (1). The excitons diffuse in the bulk heterojunction until they either recombine or reach a donor-acceptor interface, where they separate into electrons (black) and holes (white) (2). The electrons and holes will then move to the respective anode and cathode, through the donor and acceptor material phase (3).

Edit

If the figure is correct and I am the one being confused, then there are several other cases that seem to teach false. E.g. the following "PANIC"-remembering-rule to remember, which is cathode and which is anode (from this source, slide 8):

"*Negative is cathode", it says, and we are back to my question in the top: why do the electrons (black spheres) move towards the negative cathode in that schematic?

Many more diagrams agreeing with this latter one are found from a simple google search.


texts: Why do we take the compressibility factor equal to one when graph is plotted?

texts: I saw the graph of compressibility factor against pressure I was confused to see that all the gases are started by 1 unit of conpressibility factor when pressure is zero. So why do we take the compressibility factor equal to one when the graph is being plotted?


texts: E1 or E2 Elimination? Which Elimination occurs first?

texts: In this reaction scheme, two dehydrobrominations occur. A bulky base is used but both hydrogens are sterically hindered. How is it possible to determine, which one is removed first? Or is this an $E_1$ elimination and the tertiary bromine leaves first?


texts:
In transition metals, is the shell with the highest energy considered the valence shell? For example, in copper the electronic configuration is ${[Ar]\text{ } 3d^{10}\text{ } 4s^{1}}$. However, in accordance with the afbau principle the $3d$ subshell actually has higher energy than the $4s$ one. Does this mean the $3d$ subshell is considered the valence?

Second, why is gold not considered to be a reactive substance. It's electronic configuration is not stable: $[Xe]\text{ } {4f}^{14} {5d}^{10} 6s^1$, as it has an unfilled $6s$ orbital. So why is it not highly reactive like some other transition metals?


texts:
For electrochemical cells we know
$$
\Delta G = \Delta G^{\ominus} + RT\ln Q=- RT\ln Keq + RT\ln Q=-nFE
 $$
So for lithium ion batteries the reactions are
Cathode
$$ \ce{CoO2 + Li+ + e- <=> LiCoO2} $$
Anode
$$ \ce{LiC6 <=> C6 + Li+ + e^-}$$
Overall
$$\ce{ LiC6 + CoO2 <=> C6 + LiCoO2} $$
Is it safe to say the cobalt oxide is a solid as is the Lithium and can be ignored in the reaction quotient? As in a Zinc copper battery i do not think the mass of the zinc and copper affect the cell potential only the aqueous concentrations. For a lithium ion battery the cell potential is a function of the state of charge and temperature. but what are the concentrations in the reaction quotient for a lithium ion battery as most of the products and reactants are solids, is it not accurate to ignore them due to intercalation and are not exactly solids? What is nernst equation for lithium ion batteries


texts: How are diazonium salts prepared without self coupling

texts:
While preparing diazonium salts, what prevents the freshly formed diazonium salt from reacting with the still unreacted amines left in the solution and perform diazo coupling?
If this happened then there won't be an appreciable yield of the diazo salt.
So what's the reason?


texts:
How much is the effecting shielding of the 1s electrons from the 2s electrons? . Because the 2s subshell overlaps with the 1s subshell this will cause the 1s electrons to 'feel' less charge than the nucleus charge.

However due to the fact that the 2s subshell is much bigger than the 1s subshell the effect of shielding will be small correct?


texts: How does chromium help stainless steel prevent rusting?

texts:
Various sources (such as this one) say that stainless steel is stainless because a passivation layer of an oxide is formed, but I haven't found details on why chromium helps create this passivation layer. I can think of a couple possibilities:

Chromium changes the lattice constant of the iron to better match the spacing of the oxide layer.
Chromium migrates to the surface, and with enough Cr a Cr-rich layer forms on the surface which in turn creates the passivation layer.

Are either of these possibilities true, and if not, how does Cr help make the passivation layer?


texts: What is the chemical equation for the digestion/decomposition of cellulose?

texts:
I'm trying to find the chemical equation/pathway from cellulose $\ce{(C6H10O5)_n}$ to methane $\ce{CH4}$. What are the other reactants or products in the reaction?

$$\ce{C6H10O5 + ? -> CH4 + ?}$$

Everything I've found talks about bacteria and enzymes (cellulase, mostly) in terms of the process of enteric fermentation, but I've yet to find a single reaction or series of reactions for this conversion. At least one product would have to have oxygen in it, but that really hasn't narrowed down my search.

I'm mainly interested in how methane is created from the diets of herbivores, so it's very possible that I've been researching the wrong reactants from the beginning.


texts: Understanding the unit cell of Chalcopyrite vs its formula

texts:
According to the Wikipedia article for Chalcopyrite it has a formula of: $\ce{CuFeS2}$ and a unit cell of:

But from the unit cell it has 13 Copper, 10 Iron and 8 Sulphur.  This doesn't match with the formula.


texts:
The question Does H2SO or H2CO have a higher dipole moment? left me wondering whether $\ce{H2SO}$ has already been synthesized.

There are experimental evidences that both hydrogen thioperoxide $\ce{HSOH}$ (1) and  thiooxonium ylide $\ce{H2OS}$ (3) exist, whereas sulfoxide $\ce{H2SO}$, despite possessing global energy level lower than (3), is not [1]:

  The global minimum corresponds to hydrogen thioperoxide $\ce{HSOH}$ (1). The sulfoxide $\ce{H2SO}$ (2) is predicted to be $> \pu{25 kcal/mol}$ higher in energy (relative to 1) and the thiooxonium ylide 3 is the least stable
  isomer $(> \pu{34 kcal/mol}$ relative to 1).

There were numerous theoretical investigations (ab initio) suggesting that (2) is possible, but one of the most recent ones I found [2] still claims there is no experimental evidences to support its existence.
One of the problems with its structure the paper [2] refers to is that predicted $\ce{S-O}$ bond is abnormally short (1.4749 Å) and the valence state of sulfur is too high.

It would be nice if someone could point me towards a reputable source proofing/refuting existence of (2).
Additionally, what would be the complete preferred name of $\ce{H2SO}$?
MarvinSketch generates quite an amusing one: oxidanethione.

References

Iraqi, M.; Schwarz, H. Experimental Evidence for the Gas Phase Existence of $\ce{HSOH}$ (Hydrogen Thioperoxide) and $\ce{SOH2}$ (Thiooxonium Ylide). Chemical Physics Letters 1994, 221 (5), 359–362. https://doi.org/10/ct4m2m.
Denis, P. Theoretical Characterization of the $\ce{HSOH},$ $\ce{H2SO}$ and $\ce{H2OS}$ Isomers. Mol. Phys. 2008, 106 (21), 2557–2567. https://doi.org/10/dnrk2v.


texts: What are the factors that affect the corrosiveness of an acid?

texts: Acids are usually corrosive but what determines this? Is it the concentration of the acid or strength of the acid ($K_a$ value)?


texts: The distance that CO2 molecules travel in the air before they collide with each other

texts:
Well the title covers most.
But further at 410 ppm, 1 atm and 23 °C.

I believe they call it the mean free path of CO2-CO2 collisions. So not just the mean free path of CO2 in air colliding with every other molecule substances.

I have zero workexperience with gases so I'm having troubles with this one.
I'm Dutch (sadly) so excuse me in advance if my English isn't correct.


texts: Reaction of Br2/KOH with succinic anhydride

texts:
What products will be formed when $\ce{Br2/KOH}$ reacts with the following compound in water at room temperature?

Here is what I think is possible:

$\ce{OH-}$ will take up the acidic hydrogen.
$\ce{OH-}$ can attack the carbonyl group.
$\ce{OBr-}$ can attack the carbonyl group.
$\ce{Br+}$ can attack the lone pair of the doubly bonded oxygen and break the carbonyl bond.


texts: What should be the correct sequence of reagents to be used in this reaction?

texts:
The correct sequence of reagents for the following conversion will be

  (1) $\ce{CH3MgBr, H+/CH3OH, [Ag(NH3)2]+OH-}$

  (2) $\ce{CH3MgBr, [Ag(NH3)2]+OH-, H+/CH3OH}$

  (3) $\ce{[Ag(NH3)2]+OH-, CH3MgBr, H+/CH3OH}$

  (4) $\ce{[Ag(NH3)2]+OH-, H+/CH3OH, CH3MgBr}$

I think the correct option is (3), however, the key says it is (4).

The first step is definitely the oxidation of the $\ce{-CHO}$ group to $\ce{-COOH}$ using Tollen's reagent. But I think that the second step should be to use Grignard reagent to form tertiary alcohol and then acidify it. Because if we first acidify and then use Grignard reagent, the $\ce{CH3MgBr}$ will react with the leftover acid and the $\ce{CH3OH}$ due to its mildly acidic proton.

Also, I am rather doubtful that the $\ce{CH3MgBr}$ will even react with the acid formed in the first step since it will be in the form of $\ce{R-COO^-Ag+}$, which is not electrophilic.

So what is the correct answer? And how would the $\ce{CH3MgBr}$ react with the acid?
Thank you.


texts:
Among these bases,

  ammonia
  methylamine
  ethylamine
  dimethylamine
  trimethylamine
  quinuclidine

  1) Which is the strongest base relative to ammonia? Why?

  2) Which conjugate acid would be the strongest and which will be the weakest? Why?

I'm going to assume I need to look at the relative basicity (which is in kcal/mol)

ammonia: 0
methylamine: 10.1
ethylamine: 13.2
dimethylamine: 16.6
trimethylamine: 21.1
quinuclidine: 28.9

Looking at these values I would want to guess that means quinuclidine is the strongest base; and that ammonia is the strongest conjugate acid and quinuclidine is the weakest conjugate acid.

Is this correct?

The more I think about it I think I should be looking at proton affinity because the largest proton affinity is going to be the strongest base, which is still quinuclidine. but I'm still unsure about the conjugate acid.


texts:
in the reaction of addition of hydrogen halides to alkynes $\ce{Hg^2+}$ can be used as a catalyst. But what is its role? How does it increase the rate of reaction.

I think that the vacant orbitals in Hg would help in the process of ionisation of hydrogen halides. Is this concept correct? please help


texts: Can we determine the presence of carbon by simply heating or charring the substance?

texts:
Char is made of Carbon, but just because a substance char, does it immediately mean it contains carbon?

Also,
Why is charring not a good test for detecting carbon in organic compounds?
I searched that because the test can't differentiate an elemental carbon from an organic carbon. Can someone elaborate or give an example?


texts: What is the significance of the 2 and 4 positions in 2,4-DNP?

texts:
(2,4-Dinitrophenyl)hydrazine, a popular laboratory reagent is used to identify carbonyl compounds by forming 2,4-dinitrophenylhydrazones, which are often red or yellow colored precipitates.

Why is the specific 2 and 4 positions that cause precipitate formation with carbonyls, and make it a useful reagent? Can (2,6-dinitrophenyl)hydrazine work this way?


texts: Devitrification vs glass transition temperature

texts:
This graph comes from a so-called "differential thermal analysis". It is studying the effects of temperature on glass.

I don't understand what the difference between "glass transition" and "devitrification" is, and why one would be endothermic and the other would be exothermic.

I'm having trouble analysing these types of graphs. Does anyone know of a simple source online that I could check out?


texts: How to predict SN2 reaction when comparing nucleophilicty and leaving group ability

texts:
In a lab, a common experiment is to perform SN2 reactions involving a primary alkyl bromide and sodium iodide in acetone (polar aprotic solvent).

The result is that the iodide ion is a good nucleophile, so the iodide will displace the bromide from the primary alkyl bromide, and sodium bromide will precipitate from the solution.

However, without the presence of the sodium cations, would the reaction still take place?

I'm somewhat confused, because iodide is both a better leaving group and a better nucleophile than bromide, so what is the determining factor in the reaction?

Is the strength of the nucleophile more important or the ability of the leaving group be displaced?


texts: How long do the bonds in a molecule hold under nominally stable conditions?

texts:
Disclaimer: I am not a chemist

I was just drinking my Ice Age mineral water which is 'untouched since the Ice Age' and wondered if the bonds formed in each molecule have remained intact for all those years.

In a liquid that is just lying there underground I'm guessing that there is some, if not very energetic, movement of the molecules. What happens when they bump into each other? Might an atom become dislodged and bind with another molecule?

I have no idea but the thought interested me.


texts:
Is Henry's law a consequence of the equilibrium between a substance S in aqueous phase and the same substance S in gaseous phase? What I mean is, is it correct to treat Henry law as a manipulation of the equation for the equilibrium constant, where

$$ \ce{S(g) <=> S(aq)}, \ \ \ K=\frac{[S_{aq}]}{p_S}$$

$$\rightarrow K \times p_S = [S_{aq}]$$

which is Henry law ($p_S$: partial pressure of S in the gas phase; $[S_{aq}]$: concentration of S in aqueous solution).


texts: What library/program can draw molecules in 3D programmatically?

texts:
Molecular graphics software is usually interactive.

But I am looking for a library or program that would be able to render a given molecule based on the commands from another program. I would like to give it a molecule description, the vantage point, options, etc, and it should produce the picture without opening any windows.

The input is the same data as contained in an XYZ file (or the file itself), the expected output is a 3D molecule drawing.

What is the easiest way to do this?


texts:
Why is it that cyanide is an inhibitor of catalase but carbon monoxide isn't?
What makes cyanide bind well to $\ce{Fe^3+}$?


texts: If the same atoms (cells) that now compose my body get arranged in N years away, am I that person?

texts:
Probably a very stupid question, even may deserve to be downvoted, but I have always wondered: Hypothetically, let's say somehow tomorrow I die in an accident. Now lets say that after a long time (e.g. centillion of years) for one reason or another the cells that made up my body -right before I died- are part of a new body arranged exactly the same doing the exact same functions. My questions are:

1) It is possible? -Possible in the sense that atoms that are cremated tomorrow or ate by worms, can they go back to their previous chemical state?-

2) Am I the same person? Not philosophically, I mean are there in my brain the same synapses? or are other variables to take into account? (I guess this one is more about neurochemistry than chemistry)

Let's not discuss the likelihood of happening, at least not much, because time is infinite one can argue that it may be bound to happen. But time being infinite or not and related questions may be more of an cosmology issue.


texts: How do I find mass equivalence of a photon?

texts:
The problem has a flame emitting a wavelength of $589\ \mathrm{nm}$, and asks for the mass of one photon of that wavelength. It tells me that $1\ \mathrm J = 1\ \frac{\mathrm{kg\cdot m^2}}{\mathrm s^2}$.

I converted to $\mathrm J$ using $E=\frac{h\cdot c}{\lambda}$. I'm not quite sure what to do past that. I have $3.36\cdot 10^{-19}\mathrm J$. I know the answer is supposed to be $3.75\cdot 10^{-34}$.


texts: I don't understand how the 'cyclopropenium' ion is aromatic. According to my understanding, the carbons within the central 3 carbon ring must each be sp2 hybridised with a single electron in a p orbital - since each carbon is bonded to 3 other atoms and has 4 valence electrons. How does that lead to aromaticity, since this doesn't fullfil Huckel's rule?


texts: I am trying to start my own gym company that sells gym chalk however I have not been able to find a good process for making good magnesium carbonate. I have tried mixing equal amounts of magnesium sulfate and sodium bicarbonate into water and pouring it through filter paper but have not ended with a good batch.


texts: Mixture of water and acid 175 litre, in that 88 % acid, how many litres of water you should add to do 23% of water


texts: Cleaning an overhead water tank using Alum or other chemicals?

texts: Alum is generally used in water tanks to settle down solid impurities. Since it contains aluminium I suspect it to be toxic to humans. So are there any safe chemicals to clean large overhead tanks without removing the water or  doing much effort. I am asking about solid impurities and not disinfection .


texts: What result should I have obtained in these tests? Also, what went wrong?

texts:
As part of a Chemistry practical, I had to five different tests for things, and note down the result. Unfortunately, at least several results were incorrect, and despite hours of research, I cannot fully determine what I was supposed to observe and why.

Part 1 – A test for an alcohol.

To approximately 1 cm3 of ethanol in a dry test tube, add a small piece of metallic sodium.
Record your observations.
Make sure that you dispose safely of any excess sodium using the beaker of ethanol provided.

The liquid turned cloudy white. I can't find any discernible reason why this would be, unless sodium ethoxide is milky white, precipitate or dissolved. Should it just have released bubbles?

Part 2 – A test for an aldehyde using Fehling’s solution.

In a clean test tube mix together equal volumes of Fehling's solution A and Fehling's solution B. The resultant Fehling's test reagent should be a clear dark blue solution.
Add 5 drops of this test reagent to 1 cm3 of sodium carbonate solution in a test tube containing a few anti-bumping granules and then add 1 cm3 of ethanal (or propanal) to this same test tube.
Warm the test tube gently for approximately two minutes in a beaker half-filled with hot water and then gradually bring the beaker of water to boiling and maintain this temperature for a few minutes.
Using the test tube holder, carefully lift the test tube out of the boiling water and allow its contents to stand for several minutes.
Record your observations.

The liquid turned murky green. My understanding is that it's supposed to be red? I'd love to have a chemical equation for this as well.

Part 3 – A test for an alkene (a test for unsaturation)

To approximately 1 cm3 of cyclohexene in a test tube, add an equal volume of bromine water and shake the contents of the tube vigorously from side to side.
Record your observations.

The liquid went colourless. This one went as expected, I believe. My understanding is that it went colourless because all the bromine reacted?

Part 4 – A test for a carboxylic acid

Place one small spatula measure of solid sodium hydrogencarbonate in a test tube and add to it approximately 2 cm3 of dilute ethanoic acid.
Record your observations.

The liquid produced bubbles, went cloudy, then went colourless. No explanation here.

Part 5 – A test for a haloalkane.

Using a teat pipette, add approximately 5 drops of 1-bromobutane to 1 cm3 of sodium hydroxide solution in a test tube. Warm the contents of the test tube for a few minutes, by placing it into a beaker filled with hot water at approximately 60 C.
Acidify the contents of the test tube by adding 2 cm3 of dilute nitric acid and then add 1 cm3 of silver nitrate solution.
Record your observations.

Produced a blue precipitate after the bromobutane was added, and went colourless after we added the silver nitrate solution. No explanation here either.
Not enough time has elapsed as of now, but I will put reputation on this, and award it to a sufficient answer as soon as I am able.


texts:
Following up on a somewhat too broad question about amateur chemist safety, this will be the first to address some of the issues discussed there.

I often use the NOAA MSDS database (material safety data sheet) to investigate the chemicals I'm working with (they also have a nice reactivity predictor). As an example, let us examine the compound cyclohexylamine (I chose this as leading example for these followup question, because of the availability of extensive research in my country)

sometimes used as a plasticizer or catalyst. As an amateur I would carefully go through the MSDS and notice for example that it is flammable, caustic compound, scoring a 3 on flammability and health in the NFPA 704 hazard diamond.

As an amateur hobby chemist without all comfort of a basic lab (aside from safety goggles, gloves, lab coat, fire blanket), how would I judge if I can safely handle this compound with regard to its flammability, aside from conforming to the Protective Clothing section?

For example, I could imagine that flammable liquids with high vapor pressure (11 mm Hg for cyclohexylamine according to NOAA, I guess this is measured at a standard temperature as vapor pressure varies with temperature) or low auto ignition points (560 ° F) or low boiling points (274.1 °F) are unsafe for amateurs. Are there empirical (or theoretical) recommendation considering vapor pressure and ignition points, i.e., starting at what value will these factors become too dangerous for the compound to be handled in a relatively amateurish lab.

(I understand that the answers will be partly subjective, as for all answers regarding safety, but please try to give an objective as possible answer, preferably referring to external sources)


texts: Facing a problem in enthalpy calculation

texts:
If 1 mole of gaseous carbon atoms are converted into diamonds, calculate enthalpy change of process given that bond enthalpy of $\ce{C-C}$ bond is $\pu{400 kJ mol-1}.$

According to me, the answer should be that since C(diamond) has 4 bonds and C(gas) doesn't have any bonds, 4 bonds are being formed so enthalpy change should be

$$ΔH = 4\cdot (\pu{-400 kJ mol-1})$$

But in the correct solution it says each bond is counted twice, so answer will be

$$ΔH = \frac{4\cdot (\pu{-400 kJ mol-1})}{2}$$

I don't get why are we doing this. In other questions we don't consider the double counting of bonds. For example, another question I did had 1 mole phosphorus gas converting into $\ce{P4}$ molecule, and even though $\ce{P4}$ has 6 bonds, we did not consider what we did with diamond, so what is the reason for that?


texts: In class we did a lab of adding blue crystals of copper(II)chloride into distilled water, the water turned blueish green,were the changes chemical or physical?


texts: Does the mechanism of AChE inhibition by Isoparathion depend on chirality?

texts:
It is known that the inhibition of acetylcholinesterase by isomalathion can proceed either with diethyl succinate as the leaving group or thiomethyl, depending on the specific stereoisomer of isomalathion. Does the mechanism of inhibition of AChE by the Parathion isomer O,S-Diethyl O-4-Nitrophenyl thiophosphate (Or its dimethyl analog) likewise depend on the chirality of the molecule, or is 4-nitrophenyl the leaving group for both stereoisomers?
Reference:
Doorn, J. A., Thompson, C. M., Christner, R. B., & Richardson, R. J. (2003). Stereoselective Inactivation ofTorpedo californicaAcetylcholinesterase by Isomalathion:  Inhibitory Reactions with (1R)- and (1S)-Isomers Proceed by Different Mechanisms. Chemical Research in Toxicology, 16(8), 958–965. doi:10.1021/tx030026e


texts: What is non toxic to fish, has a low freezing point, and floats on water?

texts: I am looking for a liquid that floats on water that will prevent the water from freezing (or at least slow it down).  The application would be a small area (less than a square foot).  It has to be non-toxic as I do not want to harm any critters.  Thoughts???


texts:
A buffer with a pH of $\mathrm{4.79}$ contains $\mathrm{ 0.39\ M}$ of sodium benzoate and $\mathrm{0.10\ M}$ of benzoic acid. What is the concentration of $\mathrm{[\ce{H} ]}$ in the solution after the addition of $\mathrm{0.058\ mol}$ of $\ce{HCl}$ to a final volume of $\mathrm{1.6\ L}$?

My thought is that
$$\mathrm{pH=pK_a+Log_{10}(\frac{[base]}{[acid]})}$$

When we added $\mathrm{0.058\ mol}$ of $\ce{HCl}$, the concentration of both acid and base decreased by $\frac{.058}{1.6}$, so I take that ratio and apply it.  I found $\mathrm{pK_a}$ by just applying what's given.  Not sure where I am going wrong.


texts: Why do we titrate from a colourless solution and why should we remove unused sodium hydroxide from the burette as soon as possible?

texts:
In my lab we performed an acid base titration, where NaOH was used to titrate a standard solution, potassium hydrogen phthalate (KHP, or $\ce{K+C6H4(CO2H)(CO2^-)}$), using phenolphthalein indicator.

Why is it preferred to titrate from colourless to a pink solution rather than pink to colourless?

Also, why is it advisable to remove NaOH from the burette as soon as possible after we are done titrating?


texts: I live in an area with a company that claims they've made soft carbonated drink out of lactic acid and milk, how true is it?

texts:
I live in Iran, recently a massive cooperate company has produced a soda/carbonated soft drink,  under the brand name "luckydo" which they claim it's beneficial for your health and each 2 glasses equal the 1 glass of milk in terms of calcium, I've searched the whole internet there are no products similar to this at all.
I quote, this is how they claim they've made the product

"Luckydo is a soda (carbonated soft drink) based on milk!, Fresh milk enters our factory, proteins and fat are separated and all that remains is a liquid that contains calcium, nutrients and vitamins available in the milk's liquid are then combined with different flavors, lactic acid product of fermented milk and water are then added, and alas it's carbonated."

Here is the picture of the product.

My question is that, is this true?
if so why no other company on earth has tried or claimed to have such
product ?
is it really good for health ?

because I plan on buying lots of these, if what they say is not fake for commercial purposes and true.


texts: Does Langmuir model predict evaporation rates?

texts:
Slide #16 of this presentation on amalgams says that "Langmuir's equation" provides a specific "theoretical maximum evaporation rate" for liquid Hg as a function of temperature and surface area.

The only common equation bearing Langmuir's name is his adsorption model.  I can vaguely imagine that model being applied in reverse to characterize evaporation rates, but I can't see or find how in general, much less in the specific case asserted in the paper.  Can someone provide a reference or example of how that (or any other model) provides a "theoretical maximum evaporation rate" of a particular liquid?


texts:
I have tried to make sense of the article on fluorine on Wikipedia but I am still very perplexed.

I would like to know generally how reactive the fluorine compound β-(4-Fluorophenyl)-γ-aminobutyric acid; β-(4-Fluorophenyl)-GABA or "Fluorophenibut" would be as it passes through your body. Is fluorine a generally reactive element irrespective of what it is bound to or is it generally stable since it is bound to a carbon atom on an indole ring?


texts: Conversion of barbituric acid to veronal

texts:
This is just out of curiosity. I have no intention or authority to do conversions.

I am studying chemistry of tranquilizers, in that an important class is of barbiturates, which are also hypnotics. The structure of Barbituric acid and veronal, are similar, except veronal has two ethyl groups instead of hydrogen at lone $sp^3$ hybridised carbon. How can I convert Barbituric acid to veronal?

I thought that making carbocation or carbanion will help, but I don't think carbon will get negative or positive charge until nitrogen has hydrogen. Probably we'll have to protect nitrogens, am I thinking right?


texts: Replicating an illustration for the crystal structure of ferrihydrite

texts:
I came across this image of crystal structure in an article The Structure of Ferrihydrite, a Nanocrystalline Material [1]:

Does someone know the software in which it was produced? I have been looking for a way to visualize crystal structures of some minerals but I am stuck looking for a piece of software capable of doing it. I am aware of Jmol, but it does not show crystal structures too well.

References

Michel, F. M.; Ehm, L.; Antao, S. M.; Lee, P. L.; Chupas, P. J.; Liu, G.; Strongin, D. R.; Schoonen, M. A. A.; Phillips, B. L.; Parise, J. B. The Structure of Ferrihydrite, a Nanocrystalline Material. Science 2007, 316 (5832), 1726–1729. https://doi.org/10.1126/science.1142525.


texts: How is a ring formed when a carbon atom in an aliphatic chain attached to benzene ring has a positive charge?

texts:
This is my approach towards this problem. First off, a positive charge would appear in the C atom at the end of the chain, and then that carbocation would rearrange into a tertiary carbocation.

But I am not being able to figure out what will be the next step. Can the carbocation extract a hydrogen from the benzene ring to form another five-membered chain as the formation of a five-membered rings is very feasible?


texts:
I wanted to ask a question about NMR for Axial and Equatorial molecules.

I was asked to describe how to separate the following two product molecules from this reaction:

and the answer that my colleague mentioned was NMR.

He stated that for the product on the left, the $\ce{P}$ atoms were in the same environment (axial) so they would show only $1$ peak but on the right hand side product, the $\ce{P}$ atoms were in different environments (equatorial and axial) hence two different peaks would be shown.

I had a previous introductory course to NMR where coupling constants were discussed, and as the maximum bond coupling "length" was considered to be $3$, this made perfect sense.

My question is, how are axial and equatorial substituents (if they are the same substituent as in this case) in such different environments? Is it to do with the surrounding substituents deshielding by varying amounts? What is the case?

I failed to find a definitive answer on Google or StackExchange, but only statistical interpretations were given, no actual explanations.


texts: What are the products formed in acidic hydrolysis of a tetrahydropyranyl ester?

texts:
Find the major product of the following reaction:

My  approach
From my knowledge of reagents, I figured out that that the acid will protonate the oxygen(s) in the reactant and after that $\ce{C-O \sigma}$ bond should break, but I am not able to decide which $\ce{C-O}$ bonds to break in the reaction after protonation by the aqueous acid.
Am I thinking in the right direction or are there some other concepts involved?


texts: Why And How are Unbranched chains of hydrocarbons easily biodegraded?

texts:
My chemistry textbook says

  If detergents are highly branched then they can't be easily degraded by bacteria.So,nowadays the branching of hydrocarbon chain is controlled and kept to a minimum.

Upon searching this I got the answer that "side chains stop bacteria from attacking and breaking the chains".
I really don't understand how does this work.Why would having side chains prevent bacteria from attacking ? Won't they provide more sites for attack of bacteria ?


texts: Why does K have a greater electron affinity than Ca?

texts: Why will $\ce{K}$ have a greater electron affinity than $\ce{Ca}$? I know that $\ce{Ca}$ has a greater first ionization energy, and I also know that $\ce{K}$ has a greater second ionization energy, but I am confused on how to explain this.


texts: Does bleach turn a substance white or colorless?

texts:
From what I understand, bleach works to weaken the ability of a substance to absorb light. Thus this seems to be "whitening" i.e. reflecting all light. In contrast, colorlessness (according to Wikipedia) implies that light can pass through the object without scattering.

So is 'colorless' a misnomer when used to describe bleach?

(Also, to double check when you bleach something, is it still there? Only that it is now white?)


texts:
The first step in this synthesis is a Kolbe Schmitt process, but why is two equivalents of base needed? Also, what is the purpose of the two equivalents of methyl iodide? I assumed that there will be the protection of the phenol (to create a methyl ether), which would justify the two equivalents of base while converting the carboxylate into a methyl ester. However, the base is shown in separate steps, which makes me doubt if base would be available in the second step. Also, another problem is that if you follow the sequence (2 Grignard reagents used to convert the ester to a tertiary alcohol, followed by dehydration, followed by hydrogenation of the double bond just formed, followed by a Friedel Crafts acylation), you get to compound R, which only has 13 carbons, when if you had methylated the phenol, you would have 14. Does this mean that the hydrogenation somehow deprotected the methyl ether? Even more confusing, there is methylation occurring from R to S, which tells me that the phenol was protected at some point. How is this possible?

EDIT: Here is the structure of the final product. The problem was about derivatives of natural products from Salvia plants, but I could not find a total synthesis of this compound anywhere. Also, there is no easy name for it so I couldn't search it well. If you can find the source, please let us know. Note that there are other steps in the synthesis that I didn't include in this question.


texts:
I was curious if there is a specific reason why when writing mass balance reactions we always leave a $\ce{H+}$ on the left side of the equation as the professor did not explain so, or is it just convention?

For example, write the mass balance equation of $\ce{H3PO4}$:

$$\ce{H2O <=> H+ +OH-}$$
$$\ce{H3PO4 <=> H+ +H_2PO4^{-}(aq)}$$
$$\ce{H2PO4- <=>H+ + HPO4^{2-}(aq)}$$
$$\ce{HPO4^2- <=> H+ + PO4^{3-}(aq)}$$


texts: Lead(II)chloride solubility in hot water

texts:
I just went through my notes from last semester and remembered something my professor told me but only explained it very briefly. I tried to find anything about the topic on the net but couldn't find much. And I want to make sure that this information is nothing he just came up with but based on some actual literature.

So he was talking about the increased solublity in Lead(II)chloride when you heat the water. How he explained it was with the crystal structure of Lead(II)chloride where he said the lone pairs on the lead would take part in the coordination as well and whatever coordination polyhedron might form in that case (he had a selfdrawn picture of that) will have one edge which isn't very strong and likes to break at warmer temperatures which increases solublity.

Now that was all a little fast and I'd like to have some confirmation on that topic. Has anyone ever heard about this before?


texts: How can mass spectrometry be used to determine concentration?

texts: Which forms of mass spec will determine accurate concentrations of metal ions in a sample? Preferable not using GC/MS but can MALDI ToF or quadrupole do this somehow. Also, not relative concentration but actual concentration.


texts: Calculating the concentration of copper(II) from a non-standard cell potential

texts:
A galvanic cell consists of a standard hydrogen electrode and a copper electrode.
  \begin{align}
  \ce{2 H+ (aq) + 2e- &-> H2 (g)}&
  E^\circ &= 0.00\ \mathrm{V}\\
  \ce{Cu^2+ (aq) + 2 e- &-> Cu (s)}&
  E^\circ &= 0.34\ \mathrm{V}
\end{align}
  Suppose the copper electrode is placed in a solution of unknown copper (II) concentration. The cell potential is measured to be $\pu{0.195 V}$. Determine the concentration of $\ce{Cu^2+}$.

Since there's no indication that the $\ce{Cu^2+}$ is in the standard state, I started off by using the formula for non-standard cell potential:
$$E=E^\circ-\frac{RT}{nF}\ln Q$$

However, I can’t seem to get the right answer. I was wondering if I set up the problem incorrectly or how I go about getting the concentration of copper.


texts: How to predict which gas shows maximum ideal behavior at STP ? (given its critical temperature)

texts:
Suppose we know the Van Der Waals coefficients $a$ and $b$ for a set of gases in the real gas equation, then which is the correct method to predict which gas shows most ideal behavior at STP ?
Our professor said that we must check the critical temperature using the formula $$T_c=\frac{8a}{27Rb}$$ Then he said: "The gas for which $$|T_c-273|$$ is minimum will show the most ideal behaviour".
I sort of don't agree with this logic. Let us have a look at Andrew's curves:

We notice that greater is the temperature compared to critical temperature more is the ideal behaviour. So the correct method should be checking $(273-T_c)$. The gas which has maximum value of $(273-T_c)$ should show maximum ideal behaviour at $273 K$. Is my logic correct or not ? Why?


texts: Why are the hydrogen-carbon bonds bent in a graphical depiction of an alkene, but are straight horizontally and vertically in an alkane?

texts:
In propane, for example, the $\ce{C-H}$ bonds are depicted by straight vertical and horizontal lines. But in propene, the same bonds are bent.
Is it a rule that $\ce{C-H}$ bonds are always bent if the carbon atoms are double-bonded? The image below illustrates what I am asking.


texts: Which is more reactive in E1, benzyl or allyl

texts:
I'm don't know the english terminology for chemistry so sorry for probably butchering some terms.
My question is, which of these is more reactive in an E1 reaction:

The bottom two are the intermediates.
To determine the most reactive molecule, we look at the most stable intermediate.
When trying to stabilize the positive charge, the benzyl has 3 resonances and the allyl has only 1.
But in the resonance forms of the benzyl, it loses its aromaticity.
Which effect is more important, not losing aromaticity during resonance forms, or having more resonance forms?
Thanks for your help!
Note:
A similar question was asked here: Is benzyl chloride or allyl chloride more reactive?, but my question is only specific to this E1 reaction, while the other question is a general reactivity question (and has no answer...).


texts: Can Na2CO3 remove temporary hardness of water?

texts: This was asked in my test and I remembered that all compounds that can remove permanent hardness of water can remove temporary hardness of water also. But my teacher marked it wrong and I cannot find the answer anywhere.


texts: Can any atom donate more than 1 lone pair as a coordinate bond to the same metal?

texts: This would mean the formation of a σ and one or two π bonds, all coordinate. I haven't heard of this happening, like a fluorine anion or water with two lone pairs on oxygen will donate only one lone pair, but I wanted to know why it's not possible.


texts:
For the following reaction, what volume of $\ce{SO3}$ can be produced from $4.2\ \mathrm{L}$ of $\ce{O2}$ (measured at the same temperature and pressure), assuming an excess of $\ce{SO2}$?
  $$\ce{2SO2(g) + O2(g) -> 2SO3 (g)}$$

I demonstrate what I tried here but I have no idea what to try here, anyone have any suggestions on what to do?


texts:
I would assume options A and B are possible products due to the $\ce{I+}$ electrophile attacking the alkene, and hence are ruled out.

However, I am torn between options C and D. Both products are formed via the thermodynamically unfavored generation of $\ce{Br+}$, followed by an attack of either iodide or $\ce{H2O}$. While iodide might be a better nucleophile than water by virtue of the former being a charged ion, the concentration of water is likely to exceed that of the iodide ion manyfold. I am of the opinion that both C and D are possible products, and if one cannot be formed, I am unable to decide which one.


texts: Will "soft nucleophiles" undergo 1,4-conjugate addition even if the β-carbon is sterically hindered?

texts:
In general soft nucleophiles do 1,4 conjugate addition to a carbonyl carbon under thermodynamic control. Will soft nucleophiles like organocuprates still preferentially undergo 1,4 addition if the β-carbon is more sterically hindered than the carbonyl carbon?
For example, if I consider the following case

should I just accept it as a rule of thumb that these "soft nucleophiles" undergo 1,4-nucleophilic addition to the carbonyl group, or does it vary depending on the structure and the situation?
In addition to the example above, what happens if there is a methyl group at C-2 of the ring?


texts: Why is the product of the reaction "Bi + O2" Bi2O3 instead of Bi2O5?

texts:
I am stuck on a homework question that states:

  A piece of solid bismuth is heated strongly in oxygen.

The answer key states the answer as $\ce{Bi + O2 → Bi2O3}$. However, it is to my understanding that the metal Bismuth has a charge of +5 because of its location on the periodic table. Therefore, $\ce{(+5)[charge of Bi]*2 + (-2)[charge of oxygen]*5 = 0}$ giving me $\ce{Bi2O5}$. Please advise.


texts: Where can I find ranges of isotope abundances?

texts: I'd like to know how much stable isotopes like $\ce{^{13}C}$, $\ce{^2H}$, $\ce{^{17}O}$ and $\ce{^{18}O}$ deviate from their natural abundances in the earth's crust among all possible compounds we may come across, especially organic molecules. I'd like to know a rough minimum and maximum percentage of such isotopes that a given compound is likely to contain, and if possible how likely it is to contain such a percentage. It might be really good to have a histogram showing how common compounds with different percentages of such isotopes are. Does anyone know where I could find such data?


texts:
Suppose I have a mixture of 2 pure binary compounds, a white powder. What is the best method to separate the 2 compounds?

What I have thought of so far is to dissolve powder in DI water and carry out filtration if one compound is soluble and the other is not. However, I have not been able to think of any other methods to separate the 2 compounds if both are either water-soluble or water-insoluble. I considered fractional distillation but the compounds may become anhydrous. Furthermore, the boiling points of the compounds are not given and they could end up being too close for fractional distillation to work.

Is there any efficient, and preferably simple, method to achieve the above-mentioned desired result?

Edit: Is there any general method of approach for separating such 2 compounds as there is for separating water-soluble and water-insoluble compounds?[Filtration]  Or does it have to be achieved purely by trial and error of various methods?


texts: Which formula for kinetic energy of 1 mol of a gas is universally applicable?

texts: I have read 2 formulas for kinetic energy of 1 mol of gas - 3/2 RT and 1/2fRT . But if I equate them then f comes out to be 3 . But f is different of mono, di, polyatomic gases . Where am I wrong in my deduction that 3/2RT = 1/2 fRT ? Do these 2 formulas produce same result for a particular gas?


texts: Reason for prescence of oil bubbles while frying

texts: When frying with oil, it's generally assumed that heavy bubbling indicates frying, and little to no bubbling indicates a lack thereof. What's the connection between bubbles and frying? If you create bubbles in some other way, baking soda and vinegar in oil perhaps, will you increase frying?


texts: Clausius-Clapeyron - Slope of the best-fit-line

texts: I'm using the equation $\frac{y_2-y_1}{x_2-x_1}$ to find the slope of the best fit line for this problem but I can't get the figure shown in the book (-3773x K).  I've been at this a while and I really need to know so I can move on.  What am I doing wrong?  I've looked at half a dozen general chemistry texts and none of them make this step explicit.


texts: Significance of phase of atomic orbitals

texts:
I am learning about orbitals and bonding and antibonding MOs. So far, I know that when you combine s orbitals, you form both bonding and antibonding MOs- bonding when the wavefunctions are added in phase and antibonding when added out of phase. I have had several questions along the way:

What is the significance, if any, of the phase of the wavefunction for electrons in atoms when the atom is not interacting? Suppose you had a free hydrogen atom in space. Would it make a difference if you switched the phase of its 1s orbital? What about if you had a multi-electron atom? Would there be a consequence of switching the phase of the 1s orbital but not of the other orbitals? My guess is that, if this is at all possible, then yes this would make a difference due to the penetration of higher orbitals- i.e. the 2s orbital has some penetration into the 1s orbital. Thinking about it in this way, I think atoms are most stable when all the s orbitals are in the same phase and the p orbital phases are aligned. Otherwise you would get cancellation of the wavefucntion in regions closer to the nucleus so the electrons would be found further out, and therefore would have a higher potential energy. There would also be more localisation of electrons further from the nucleus so they would have a higher kinetic energy too. I think it therefore would be significant when we change the phase of orbitals relative to other orbitals (whether in the same atom or in interacting atoms), but if you changed the phase of all wavefunctions in the universe right now then it wouldn't matter.

My second question:

How do we form the bonding and antibonding MOs? Is it becaue each orbital is actually in a superposition of being 'phase 0' and 'phase pi' which is why you get both bonding and antibonding MOs? I'm just not sure if superposition of states is at all important here, or if I have misunderstood this.

Finally, when I was considering p orbitals, I noticed that th phase of the two lobes in a single p orbital is opposite.

So here we have two opposite phases existing together. Is there a significance of this? Or is it perhaps again only important in the interaction of p orbitals?


texts: Octahedral Crystal Field Splitting Orbital Energy Levels

texts:
(image source)

In the above diagram, where do the 3/5 and 2/5 come from? Also, how are the $\ce{e_g}$ orbitals degenerate with each other?


texts: How does the pKa of a neutral molecule inform the protonation state of its positively charged molecule?

texts:
Let's say we have some neutral molecule A and its protonated form, A+. The pKa of molecule A is known, but we do not know the pKa of molecule A+. Can the pKa of molecule A+ be determined only knowing the pka of molecule A? For example, is there an expression that relates the pKa values of arginine together? (For reference, arginine's pKa values are are 2, 9, 12.5.)

The context of this question lies in trying to understand how the protonation state of molecule A+ will change in an inhomogeneous environment (for example, a lipid bilayer). The pKa of molecule A+ is estimated to change +2 pK units in the bilayer relative to in aqueous solution. The pKa of molecule A is known to be 7.09, but the pKa of molecule A+ is not known. How can any change in protonation state of molecule A+ be predicted given only this information?

Note that this question is NOT asking the protonation state of a molecule if we know THAT molecule's pKa and if we know how ITS pKa changes (for example, as was asked previously).


texts:
I intend to bring solid Alumina Oxide into a liquid state, for the purpose of pouring the substance into a mold.  Subsequently, I will allow it to cool with an ambient air temperature of 70f, slowly allowing it to return it to a solid state.  Melting will be performed with a gas mixture.

My question is, will the Alumina Oxide return to the original molecular structure as is was prior to melting it from a solid state?

Thank you for your time and consideration.

Rob


texts: Why is it easier to break a C-H bond of methane after another C-H bond has already been broken?

texts:
Bond energy explanations say the number given is often an average.

For instance, in methane, the $\ce{C-H}$ bond dissociation energy is the total energy required to remove all four hydrogens, divided by four. $(\pu{415.5 kJ/mol})$

But, removing the first hydrogen atom is harder than the second or third ($\pu{439 kJ/mol}$ for the first). Why?


texts:
I expected ethene ($\ce{C2H4}$) to undergo electrophilic substitution due to $\ce{HCN}$ but it doesn't happen, as I am told by my textbook.

I couldn't figure out the reason, as I found out that $\ce{HCN}$ does react with $\ce{CH3CH2Br}$ by nucleophilic substitution.  Upon ionisation, the proton of $\ce{HCN}$ is an electrophile,while the cyanide group is a nucleophile.  Correct?


texts:
does anyone know where I could purchase zinc ink? Sigma Aldrich only sell Zinc Oxide, and I'm struggling to find a method in which I could remove the oxide after I print onto a polymer substrate.

Would be grateful if anyone could point me in the right direction. Thanks.


texts: I've been asked to install some kind of technology to a building with 40 rooms to soften the water. Browsing through the product catalog I found this so called "Magnetic Water Softener", however theres no description of how it works, how does it make water soft?


texts: Confirming the presence of 4-bromoacetanilide during bromination of acetanilide

texts:
In my lab, acetanilide was added to bromine in aqueous acetic acid, and discolouration of the reaction mixture was obtained, indicating that bromine was consumed.

After some discussion, it was concluded that an electrophilic aromatic substitution might be taking place. This was backed up by a procedure we found online. What was left to do was to confirm the presence of the product, 4-bromoacetanilide.

The challenge is that the reaction mixture contains unreacted acetanilide as well as 4-bromoacetanilide, acetic acid, and possibly some polyhalogenated byproducts. Any conditions that could result in amide hydrolysis, e.g. heating with base, should also be avoided.
No residue was observed in the reaction mixture.

So, what chemical property can be used to determine the presence of 4-bromoacetanilide in the reaction mixture?


texts: Acidic nature of benzene and other alkenes

texts: Is benzene acidic? It has $sp^2$ hybridization so doen it mean that it is acidic in nature? Are alkenes acidic?


texts:
I am trying to understand the meaning of chemical energy.
I saw in my book that chemical energy is stored in the bonds of chemical compounds and when the bonds are untied the chemical energy increases.

I don't understand, shouldn't the chemical energy decreases? I think this because the chemical energy is not stored anymore (because there are no bonds)

This page describes the chemical energy level.


texts: Equilibrium concentration, where does the 5.00 for iron thiocyanate complex come from?

texts:
Trial #1:

$$\ce{Fe^3+(aq) + SCN^- (aq)  ->   FeSCN^2+(aq)}$$

\begin{array}{|r|c|c|c|}\hline
\mathrm{Initial~}(M)&\phantom{-}6.00 &\phantom{-}10.00&\phantom{-}0.00\\\hline
\mathrm{Change}~(M) & –4.00 & –4.00 &+4.00  \\\hline
\mathrm{Equilibrium}~(M)&\phantom{-}2.00&\phantom{-}6.00&\phantom{-}4.00\\\hline
\end{array}
$$ K = 0.333$$

Consider the reaction represented by the equation:
$$\ce{Fe^3+(aq) + SCN- (aq) \longrightarrow  [Fe(SCN)]^2+(aq)}$$

Trial #2:

Initial: $10.0 ~M\ce{~Fe^3+(aq)}$ and $8.00~M\ce{ ~SCN- (aq)}$ (same temperature as Trial #1)

Equilibrium: $x~M\ce{~FeSCN^2+(aq)}$

I have tried putting $10.0$ and $8.00$ in an ice table, then when I have finished I start solving to get my equation as $$0=\frac{0.33x}{(10.0-x)(8.00-x)}$$ when I'm done I come out with $$0.33=\frac{x}{(x^2-18x+80)}$$ then I plug in for quadratic equation,
$$x=\frac{-6.94\pm\sqrt{6.94^2-4\times0.33\times26.4}}{2\times0.33}$$
my answers came out to be $-5$ and $-16.03$.  What am I doing wrong?


texts: Do SALC-AOs really belong to their symmetry species?

texts:
I'm working through a molecular symmetry textbook and something keeps nagging at me. If I derive the SALC-AOs for NH3 (using the projection operator method), I'll get

A1:  $  \frac{1}{\sqrt{3}}(\phi_1+\phi_2+\phi_3)$

Doubly-degenerate E:

$  \frac{1}{\sqrt{6}}(2\phi_1-\phi_2-\phi_3)$

$  \frac{1}{\sqrt{2}}(\phi_2-\phi_3)$

where the $\phi$s are the H 1s orbitals, ie.:

(This was the best image I could find, but in the second E orbital the black s-orbital should be enlarged)

I'm having trouble seeing how these SALC-AOs would be a member of their symmetry species. The A1 SALC-AO is identical under each operation, so it makes sense that it would belong to A1. But if I want to confirm that the two E SALC-AOs belong to E, how would I do that?

My intuition is that I should be able to apply each C3v operation to the SALC-AO and get back the E row of the character table (Below). But if you apply a C3 rotation to the e2 orbital, you get the black orbital taking the place of the white orbital, the white taking the place of the node, and the node taking the place of the black orbital. This doesn't seem like it could be expressed as a number in a character table, since the SALC-AO isn't being taken to itself or -itself.

Am I thinking about this all wrong? How should I understand the SALC-AO as a whole? Any guidance is appreciated, the textbook seems evasive on this.


texts:
I have a question about Rietveld refinement

The author of this paper claimed that the free refined CN ligand is 1.081.
However, they does not show how they got that number. They stated it was based from this table however I am not sure how you can get 1.081 from this table. What is the calculation?

Thank you.

Source:

Reference

Wang, W.; Gang, Y.; Hu, Z.; Yan, Z.; Li, W.; Li, Y.; Gu, Q.-F.; Wang, Z.; Chou, S.-L.; Liu, H.-K.; Dou, S.-X. Reversible Structural Evolution of Sodium-Rich Rhombohedral Prussian Blue for Sodium-Ion Batteries. Nature Communications 2020, 11 (1), 980. DOI: 10.1038/s41467-020-14444-4


texts: Confusion in hybridisation of coordination compound

texts:
I want to know the configuration and hybridisation of the compound, hexaaquavanadium (III) ion that is $\ce{[V(H2O)6]^{+3}}$.

In this Vanadium is in $+3$ oxidation state its electronic configuration is $\mathrm{[Ar]4s^0 3d^2}$.

So there are $3$ more empty $\mathrm{d}$ orbitals.

Hence the hybridisation should be $\mathrm{d^3sp^2}$.

But it is $\mathrm{d^2sp^3}$ and paramagnetic .

I could not understand how .

Can you explain me?


texts: What are the main differences of CTAB and DTAB surfactants? And what are practical applications of them?

texts: Just doing a little bit of research of both surfactants but I can't seem to find too much online about them. Hopefully you guys can help out!


texts:
I recently came across a suggestion in an old (first published 1893) book that a solution of ~1% cresol soap in water could be used as a way to store a particular kind of root without allowing it to dry out or rot.

I've tried searching, but have been unable to determine what cresol soap might be. The closest I can find are several shady poorly-translated websites selling Lysol as cresol soap, or possibly a mixture of the two.

Does anyone have a clue what this book could be referring to?


texts: How different are molecule with same connectivity

texts:
Let us represent molecules by graphs (atoms are vertices and bonds are edges).
Let $A$ be the adjacency matrix of the molecular graph. $A_{ij} = b$ where $b$ is either binary: 0 when atom i and j are not bonded else 1 (Repr. 1). Or, further we may take b from the set $\{0,1,2,3\}$ depending on whether the no bond (0) or single(1) double(2) or triple (3) bond is present (Rper. 2). Here were are not distinguishing the atoms - for our purose they represent a node in a graph.

Let us consider only non-isomers and molecules with at least 10 atoms. How different will be two molecules with same graphs (with respect to Repr. 1 or Repr. 2) in terms of their properties or particularly about drug-like properties. My interest is to know how faithfully the topological indices characterizes the molecular activity. Specific or general examples of pairs of  non-isomer molecules with same graph but very different property could be useful. It would be helpful if I can find enough examples to convince myself about the usefulness or otherwise of topological indices which are calculated from the grpahical representation outlined above. Topological indices are popular in drug discovery research, but I am not very much convinced about their utility since most the results published are not statistically significant (use of very small data size - from 15 to some hundreds molecules, among other weakness) nor rigorously validated.

Thank you.


texts: Are there magnetic rocks, and not hematite?

texts:
I dug up some sand and small rocks in a stream bed near me and moved a powerful magnet through the wash picking up numerous small rocks and black sand.

Now, the black sand is definitely small crystalls of magnetite, but what about the small rocks which tend to be gray in color, some being brownish?

I thought pretty much anything you would be likely to encounter commonly (like in a stream bed) that is magnetic is magnetite. In other words, my understanding is that the only COMMON mineral that is magnetic is magnetite. But these small rocks do not appear to be magnetite crystals, and the brown ones definitely are not.

Does this mean there are magnetite crystals INSIDE the rocks? Like if I break them up will I find little tiny magnetite crystals within?


texts: Chemistry that takes place in a ball tumbler is distinctly different from aqueous chemistry. Is there a good introduction to this method?


texts: How to optimize the molecular geometry under PyMol?

texts:
I already now about the Optimize.py plugin, which seems to be working well, but I don't see an option to prevent it from changing double bonds to single ones. If Optimize isn't capable of such, how can I achieve a minimized molecule from a hand-built one?

As far as I know Optimize uses Open Babel. I could imagine that the problem is, that it doesn't export the state of bonds at all.


texts: How to redefine internal pressure in terms of κ and α?

texts:
The formula for internal pressure of a system is:
$$\pi_T=T\left(\frac{\partial p}{\partial T}\right)_{\!V}-p$$

My professor said we can redefine this equation in terms of either the

thermal compressibility, $\kappa$
expansion coefficient, $\alpha$

How do we do this?

I was able to derive for a van der Waals gas:

$\Large\kappa = \frac{V-nb}{pV-\frac{an^2}{v}+\frac{2abn^3}{v^2}}$
$\Large \alpha= \frac{nR}{PV-\frac{an^2}{v}+\frac{2abn^3}{v^2}}$


texts: Relationship between microplastics and wildfire smoke

texts:
My understanding is that:

microplastics are short fragments of previously long polymer chains;
wildfire smoke largely consists of incompletely burned organic materials such as wood. Wood burns by heat first breaking long polymer chains into small fragments, which then ignite (or not).

So ... it sounds like there is quite some similarity between (some parts of) wildfire smoke and microplastics.
What are the key differences? Does it boil down to nature's ability to recycle one but not the other because their composition is different because they came from different types of polymers?
This is a noob question. But I'm still curious :-)


texts:
I'm in need of hydrochloric acid for cleaning parts before electroplating, but I'd rather not deal with the HCl fumes given off by it, as I'd rather keep my workshop contents from rusting.
Given that HCl basically from what I've understood escapes any container it's put in, I had the idea of putting the container inside a bigger bucket and putting something in the bottom of the bucket to react with the fumes give off by the hydrochloric acid.
My first idea was either sodium bicarbonate or lye in solid form, would these react with it or do I need to have the base in liquid form? I'd rather not have my hydrochloric acid container covered in a lye solution.


texts: I am confused about the stability of carbanion III and IV in the image, I think III is more unstable because of electron donating effect (+R) of  $\ce{-OCH3}$ group but my book says III is more stable than IV. In compound III, $\ce{-OCH3}$ would donate its lone pair and would make the carbanion unstable but no such effect happens in compound IV. $\ce{-OCH3}$ in compound III would also have -I effect to stabilize the carbanion but I have read that for $\ce{-OR}$ group, +R effect is more than its -I effect i.e., its electron donating nature is more than its electron withdrawing nature through inductive effect, +R means electron donating by resonance (In $\ce{-OR}$, $\ce{R}$ is any alkyl group)


texts:
What compounds or nanostructures contain the most hydrogen atoms per unit of volume in realistic conditions (under 1 GPa). Particularly boron-free compounds because it's to be used in sci-fi nuclear designs.

What I've investigated so far:

Zirconium Tetrahydride (0.229 mol/ml, unstable?)
Thorium tetrahydride?
Ammonium Borohydride (~0.176 mol/ml, unstable?)
Aluminum Borohydride (~0.175 mol/ml)
Borazane (0.152 mol/ml)
Aluminum Hydride (0.148 mol/ml)
Tetramethylammonium Borohydride (0.146 mol/ml)
Solid Ammonia (0.144 mol/ml)
Solid Hydrazine (0.143 mol/ml)
Uranium Hydride (0.136 mol/ml)
Paraffin Wax (0.131 mol/ml)
Liquid Cyclopropane (0.128 mol/ml)
Tetramethylammonium Chloride (0.128 mol/ml)
Beryllium Borohydride (0.125 mol/ml)
Lithium Borohydride (0.122 mol/ml)
Liquid Ammonia (0.120 mol/ml)
Beryllium hydride (0.118 mol/ml)
Sodium Borohydride (0.113 mol/ml)
Magnesium hydride (0.112 mol/ml)
Water (0.111 mol/ml)
Cyclohexane (0.111 mol/ml)
Neopentyl alcohol (0.111 mol/ml)
liquid ethane (0.109 mol/ml)
ammonium fluoride (0.109 mol/ml)
Hexane (0.106 mol/ml)
Neopentane (0.104 mol/ml)
liquid methane (0.105 mol/ml)
ethanol (0.103 mol/ml)
liquid cubane (0.099 mol/ml)
lithium hydride (0.098 mol/ml)
lithium aluminum hydride (0.097 mol/ml)
liquid propane (0.091 mol/ml)
Solid hydrogen (0.087 mol/ml)
Liquid hydrogen (0.070 mol/ml)


texts: What makes dimethylmercury ((CH3)2Hg) so penetrative through latex and human skin?

texts:
I've read the story of Karen Wetterhahn and how she was poisoned and died from two drops of dimethylmercury that accidentally fell on her latex glove, and I was wondering what is the chemical explanation for such easy penetration of the compound through latex and skin.
I do not have a vast knowledge of heavy metal chemistry, but here are the points that gave rise to this question:

There are many dimethyl compounds with a similar structure to dimethylmercury. Some are very common, such as dimethyl ether (CH3-O-CH3), propane (CH3-CH2-CH3). Oxygen is a lot smaller than mercury, and methylene is larger but is (presumably, I might be wrong here) more similar to the methyl groups than mercury in hydrophobicity etc., so why are they not as penetrative?
According to this answer by AMM:

  Actually metallic mercury is very hard to absorb by ingestion or through the skin so if ingested one will most likely survive (according to studies on animals). However, if one ingests the same amount in a soluble salt form (or any other absorbable form, eg HgMe2) he is in serious trouble (see here: Karen Wetterhahn).

Is it because the most common form of mercury is the cation $Hg^{2+}$, whereas the methyl groups make the compound uncharged and thus soluble in hydrophobic matter, such as skin and latex?


texts: Why do we use concentrated sulphuric acid to dry hydrogen chloride gas instead of anhydrous calcium chloride? Both of them are drying agents, what's the difference between them?


texts: Would an (NH3)2+ molecule be trigonal planar like BH3 rather than trigonal pyramidal?

texts:
I've been learning about using MO theory to explain why $\ce{BH3}$ and $\ce{NH3}$ have different geometries and by following the line of reasoning used to rationalise the differences in geometry I came to wonder whether ionisation or the addition of electrons to a molecule can change its geometry.

Eg: $\ce{NH3}$ is trigonal pyramidal but an $\ce{NH3^2+}$ ion would have the same electron configuration as $\ce{BH3}$, which is trigonal planar; does this mean $\ce{NH3^2+}$ would be trigonal planar?

Edit: My bad when I first posted this I wrote $\ce{NH3^2-}$ but meant $\ce{NH3^2+}$, this was just an example, my main objective was to find out whether changing the geometry through ionisation was possible.


texts: The delocalized electrons in a metal move about because of the electrostatic attractions between them and many different positive ion cores. But why does the same not occur with the ion cores themselves? Why are electrons, which bear the same magnitude of charge as nuclei, mobile, while the nuclei themselves are not?


texts: Why is Cu2HgI4 filtered while it is hot?

texts: Why is it required that the solution of copper (I) tetraiodomercurate (II), which has a thermochromic property, be filtered while it is hot?


texts: How would I measure the Carbon Dioxide content in Coca Cola over a period of time?

texts: I'm sorry if this is a broad question, but I am trying to plan a simple experiment. I am wondering is there a somewhat simple way of continuously measuring $\ce{CO2}$. I already know the initial carbon dioxide content is around $\pu{2.2g}$ from research, but I don't know how this result is reached.


texts:
Please consider the following figure of a concentration over time (msec) diagram with variables for an enzyme, a substrate bound enzyme and a product.

Recall that $\ce{E + S \leftrightharpoons ES \rightharpoonup E + P}$ and also recall that the velocity constant of the respective reactions are noted $k_1 , k_2, k_3$.

What I would like to know is:

On the plot provided, is the slope of $[ES]$ equal to $k_2$ and is the slope of $[E]$ equal to $k_1 + k_3$ thereby giving some insight/explanation for $k_m$ which is used to determine the affinity of an enzyme?

Any more details on Michaelis Menten is greatly appreciated but please note that my level of understanding is limited on the topic.


texts: What is meant by complete outer shell? Why do the noble gases have zero valency?

texts:
Does having 8 or 2 electron in the outmost shell mean its outmost shell is full and its valency is zero?

I know that the 3rd and 4th shell can contain 18 and 32 electrons.
Then how can Argon's (2,8,8) outmost shell be full, though it does not contain the highest number of electron (18) in it's 3rd shell?

It is the same in the cases of other noble gases too? Why?


texts: Computational tool for identification of activity cliff

texts: Are there computational tools for identification of activity cliff between two analog compounds? This paper  list chemotypes that with a high propensity to induce activity cliff.


texts:
If doing a problem where you use the integrated rate law for a second order reaction

($\frac{1}{[\mathrm{A}]}-\frac{1}{[\mathrm{A_0}]}=kt$) to first find $k$, then use that to find the half-life. Does it matter seconds are used, or minutes, or whatever?


texts: Trying to understand phrase in paper: preventing nonspecific binding of AuNP antibody conjugates using a blocking solution

texts:
I am working through a paper, Lateral flow immunochromatographic assay on a single piece of paper. I'm having trouble understanding one of the points!
Under the Device fabrication question, it says:

The sample and conjugate release regions were treated with a blocking solution to prevent nonspecific binding of AuNP-antibody conjugates.

I didn't understand this phrase, so I did a bit more research and found a question by the author on ResearchGate asking how to prevent nonspecific binding.
However I still don't quite understand. What exactly is nonspecific binding of AuNP-antibody conjugates, and how does a blocking solution prevent this?
Any overview/pointers about where to research further would be very much appreciated.


texts: Do gases behave ideally near the critical temperature?

texts: In class, my TA said the closer the temperature of a gas is to the critical temperature, the more ideal it is. I'm struggling to understand this, as I thought more ideal behavior occurs at high temperature and low pressure. I am probably missing something really obvious :(


texts: Are the bonds in the monomers at the end of a polymer filled or unfilled?

texts:
In polymers the bonds between monomers are changed, usually from double to single1, to form a long-chain polymer with the now single bond joining another monomer. But in the monomers at the very ends of a polymer chain, there is an unfilled bond, a carbon atom with only three bonds filled. During the polymerization process are those unfilled bonds left unfilled, or is there some process that fills those bonds with, say, another hydrogen atom?

I say this because I don't know if there are any polymers made where the bond inside the original monomer is a triple bond. In all the commonly used plastics (those that have recycling symbols) the original monomers have double bonds between the carbon atoms.


texts: Why is the boiling point of trichlorofluoromethane lower than that of chloroform?

texts:
If $\ce{CFCl3}$ has a higher molar mass, how come $\ce{CHCl3}$ has a higher boiling point?
$$
\begin{align}
\mathrm{bp}(\ce{CFCl3}) &= \pu{23.77 °C} \\
\mathrm{bp}(\ce{CHCl3}) &= \pu{61.15 °C}
\end{align}
$$


texts: Why does 2,4 DNP give orange colour crystals?

texts:
Why does 2,4 DNP give orange crystals on reacting with solution of aldehydic or ketonic group? Why does this test give orange crystals? Is this related to the electron emissions?

This is just a question from a curious student after 2 hours of lab work.


texts: Is there a relation between transition density and density differences?

texts: When I have an excited state, is there a relation between the transition density associated with this electronic transition and the density difference between the excited state density and the ground state density? Can the transition density be equal to the difference density?


texts:
It is my understanding that if you put table salt (as an example of polar compound) in water, the Na+ and Cl- ions will freely move through the solution. They will make the solution conductive and will independently travel through it to carry electric current.

Now the thing is, if you dry the solution, how come every Na+ finds it's Cl- to recombine into NaCl? How come there are no lonely Na+ and Cl- pairs who couldn't find their mate in time, before the solution dried completely? Can someone give me a better understanding of how do polar solutions work?


texts:
Is there a physical meaning to the SCF energy of a molecule obtained using pseudopotentials to represent the core electrons of heavy atoms (for example gold)?
I've been running calculations in Gaussian on a system with a number of gold atoms and I became curious whether my use of pseudopotentials for the gold core electrons was skewing the results I obtained. So, I attempted to run a smaller test comparing two identical systems where one used pseudopotentials (specifically the LANL2DZ basis set) for the gold atoms and the other was all-electron with the DZP basis set. When I performed thess calculations, I got very similar orbital energies for the frontier orbitals, but the total energies were completely different, with the total energy of the all-electron calculation approximately 50 times more stable than the pseudopotential calculation (e.g. -100000 vs -2000 au).
Perhaps I've missed some obvious shortfall of pseudopotentials, but I just don't see how the energies obtained could be so different. I would expect an error in the calculation if the orbitals hadn't made sense or there was any unusual messages in the log file, but I didn't notice any such problem. The geometries and route sections used in each case are the same (besides the one having pseudo=read) and the only difference was the basis sets, where LANL2DZ is built in and I found DZP through the basis set exchange.


texts:
This problem(from ionic equiibrium) states:

We are given $\pu{40 mL}$ of $\pu{0.1 M}$ $\ce{HCl}$ and $\pu{10 mL}$ of $\pu{0.45 M}$ $\ce{NaOH}$ in two separate beakers. These two solutions are mixed. Find the $\mathrm {pH}$ of the resultant solution formed.
Consider the concentration of the ions formed by self dissociation of water to be negligible.

My method
Number of moles of $\ce{H+}$ ion in the first solution is $\pu{0.004 mol}$ and the number of moles of $\ce{OH-}$ in the second solution is $\pu{0.0045 mol}$.
Now, after mixing the two solutions, the resulting concentration of $\ce{H+}$ ion becomes $\pu{0.08 M}$ and that of the $\ce{OH-}$ will become $\pu{0.09 M}$. Now these $\ce{H+}$ and $\ce{OH-}$ ions will react with each other such that the equilibrium constant of their reaction becomes $10^{-14}$.
So I formed the equation
$$(0.08-x)(0.09-x) = 10^{-14}$$
From here we can calculate $x$ and subsequently we can get the concentration of $\ce{H+}$ ion in the final solution.
I want to know is this the correct way to solve the problem?
The answer to this problem is given as $12$, which I doubt can be obtained from my way of doing the problem.


texts: "Don't pour oil into lye, pour lye into oil"

texts:
I was making soap last weekend and I got distracted, and thence I put too much lye into my oils blend. Basically, the whole soap paste is unusable to make soap because the cure will never be enough to neutralize all the lye contained in the soap paste.

I wanted to recalculate the lye quantity and add the quantity of oil needed to salvage my soap paste but I remembered a piece of advice I read on the recipe: never pour oil into lye, always pour lye into the oils.

Why is that?

At first I thought it was because of similar reasons to why one shouldn't pour water into acid (as these two substances react strongly when put together and the hydration reaction may provoke projections). It has been a while since my high school chemistry lessons but I think that a similar thing happens with water and basis. However, oil has pretty much nothing in common with water when it comes to chemistry. Another reason may be that what a user from a soap making community calls the "splash potential":

  You are more likely to splash whatever is being poured into than what is being poured. You do not want lye water splashing out onto you and your surroundings.

This sounds more plausible but it isn't a scientific explanation. So, is there a scientific reason behind the restriction: "do not pour oil into lye"?


texts: Why does monoammonium phosphate (MAP) have 52% of phosphorus (P₂O₅)?

texts: The formula of monoammonium phosphate (MAP) is $\ce{NH4H2PO4}$. Manufacturers say that MAP has 10% of nitrogen (N) and 52% of phosphorus (P). However, its molecular mass is 115 u and the atomic mass of P is 31 u $(31/115 × 100\% = 27\%)$. How is there 52% of P?


texts: Working with wave number equations, use trial-and-error?

texts:
I have a wave number question which I have partially solved:

  What transition in $\ce{He+}$ ion shall have the same wavenumber as the first line in Balmer series of $\ce{H}$ atom?
  (a) $7\to5$ (b) $5\to3$ (c) $6\to4$ (d) $4\to2$

Here's how I solved it:

Note: symbol $Z$ is the atomic number
and $1/\lambda$ is wave number (I have written frequency by mistake)

At this point my teacher told me to continue using a trial and error method, is there any other way to solve this, perhaps using some other equation.


texts:
I know from the literature that the following compounds have decreasing polarity: Rosmarinic Acid -> TMF -> Sinensetin and I guess comparing compounds of similar structure it is manageable to compare bond types, groups etc etc by which to order their polarity, but what about compounds with very different structures, groups and bonds, especially when you want to rapidly order 10's-100's of compounds.
My questions:

Is there such a thing as an absolute measure of "polarity" for a compound by which other compounds can be compared/ordered?

Depending on 2) is there a resource whereby you can lookup your compound to obtain its polarity?

I am asking this question from a Chromatography perspective. I would like to know the order of separation for a group of compounds and how to know what "polarity" of mobile phase to start my experimentations with.


texts: Why does melting point depend on external pressure?

texts:
The melting point of a substance is the temperature at which the solid form's vapor pressure equals the liquid form's vapor pressure. I read that the vapor pressure of something depends ONLY on the temperature. So as the external pressure changes, the substance's vapor pressure should stay the same if temperature is constant. In that case, the melting point should not be affected by external pressure.

I understand that intuitively, melting point increasing with pressure makes sense, as more energy is needed to overcome larger external pressure in order to liquefy. But how can this be explained with the vapor pressure definition?


texts: Why is pyrrole more reactive than pyridine and benzene for an electrophilic substitution reaction?

texts: According to me, pyridine should be the most reactive as it has got an extra pair of electrons on the nitrogen atom which is further localised and readily available for electrophile.


texts: Is it okay to conclude that in 2-nitrophenol where intra hydogen bonding is experienced, two similar molecules are only held by the weak van der waal's forces and is the reason for it to have a relatively lower boiling point than other nitro phenols


texts: Lattice Energy and Stability in s block compounds

texts:
Lattice energy decreases down the group but stability of the compound still increases why?
For the purpose of this post I'll take alkali earth metal carbonate as an example.
As we go down the group size of cation increases and hence the lattice energy decreases, however my book stated that

The thermal stability (of carbonates) increases with increasing cationic size

I've heard that big cations are able to form better stable compounds with big anions. However we say that lattice energy has decreased. Then what is the factor that is providing this stability in an ionic compound ?


texts: Relative basicity of fluorine and oxygen in silyl ether deprotection

texts:
Why does the $\ce{O}$ take the $\ce{H+}$ instead of the $\ce{F}$?

What I took into consideration:

$\ce{O}$ pulls more $e^-$ from atoms near it: $\ce{O}$ is more basic
$\ce{F}$ has one more $e^-$ pair than $\ce{O}$: $\ce{F}$ is more basic
$\ce{F}$ is more electronegative than $\ce{O}$   : $\ce{O}$ is more basic(?)
$\ce{O}$ has more substituent group making it sterically hindered: doesn't matter(?)

Is it okay to think this way? What's the most important factor?


texts: How to explain the concept of mol and reactions involving mol quantities

texts:
From time to time I do little pro bono lessons for second grade in math, physics, and chemistry. Recently I came across this question.

  In a container is $2~\mathrm{mol}$ of $\ce{SO3}$ (sulfur trioxide). This compound under certain conditions breaks down into $\ce{SO2}$ (sulfur dioxide) and $\ce{O2}$ (oxygen). At the same those two resulting compounds react together back to form $\ce{SO3}$. In equilibrium we have $1.52~\mathrm{mol}$ of $\ce{SO3}$.
  How much of remaining resulting compounds do we get?

The answer: It is obvious that $0.48~\mathrm{mol}$ of $\ce{SO3}$ broke down into $0.48~\mathrm{mol}$  of  $\ce{SO2}$ and $0.24~\mathrm{mol}$ of $\ce{O2}$.

The problem: A few of students cannot grasp how could we start with $2~\mathrm{mol}$ of some substance and end up with $2.24~\mathrm{mol}$ of other substances. I have tried to explain to them that $\mathrm{mol}$ is not a quantity as they are used to as in weight or volume, but that a $\mathrm{mol}$ is a number of molecules. I have tried to simplify an example using just 2 molecules of $\ce{SO3}$ and showed that the break down to 2 molecules $\ce{SO2}$ and 1 molecule of $\ce{O2}$. That was understandable. But as soon as we got back to moles: "How can we get more than we started with?"

What is the best way to explain this? Any experience? To me, it seems so obvious.


texts:
So many atoms can be surrounded by oxygen atoms to make anions - chromate, phosphate, etc.   In particular there's Tellurate $\ce{TeO4^{-2}}$, Selenate $\ce{SeO4^{-2}}$ and Sulfate $\ce{SO4^{-2}}$ - why not go one step more and have "Oxygate" $\ce{OO4^{-2}}$?

I would guess that such a thing, if it could be created at all, would break up into an molecular oxygen and ozone $\ce{O2 + O3}$ with the electrons doing whatever they please.  But sulfate and the heavier VI central atoms don't break up.  I've never encountered a good clear explanation about this.


texts: Which bonds need to be broken to form a liquid?

texts: I'm confused whether it's the intermolecular forces, or the bonds that are being broken when a substance changes state? Does this differ among different types of compounds (eg. covalent, ionic, covalent network solid? What is actually happening when they change state?


texts: Is it safe to mix calcium carbonate and sodium chloride?

texts: I know zero about chemistry, and Google has not offered up a plain answer, so I beeseech thee; Is it safe to mix calcium carbonate and sodium chloride to make a simple mouthwash?  Calcium carbonate for the acid neutralizing, and sodium chloride for disinfectant.


texts: Why can't the N- end of the nitrile anion attack the alkyl halide in an SN2 fashion during an alkylation reaction when OH- can?

texts:
I'm reading my Clayden textbook and something keeps nagging me. It says that when we're carrying out alkylation reactions with an enol attacking an alkyl halide with strong base catalysis (with hydroxide), we should keep the base separate from the alkyl halide electrophile to prevent it from performing the SN2 attack instead of the nitrile anion formed from deprotonating the nitrile at the alpha position.
But, if OH- can attack the alkyl halide as a "competing reaction", why can't the N- end as well instead of the nitrle anion carbon-carbon double bond? They both (OH- and N-) seem like equally good nucleophiles. Is it because when we have the option to choose from the "soft" end (the double bond in the nitrile anion) and the "hard" end (the N-) nucleophile to attack the soft alkyl halide electrophile, we'd much rather have a soft nucleophile to soft electrophile attack?


texts:
Problem:
On my boat I have a marine toilet. It is operated with salt water.
The problem is, on the interior of the outflow tubing it accumulates some sort of hard grime. I am looking for a good way to dissolve this grime as it is impossible to replace the tubing.
From experience it is known that citric acid work - but not very well. Also it leaves a "sandy" residue that is difficult to flush.
Does anybody have an idea of what this "grime" consists of - and thus how best to dissolve it?
Materials:
On hand I have:

citric acid
56% phosphoric acid
23% HCl

Materials:

tubing: PVC
toilet itself: porcelain
pump: ABS or polypropylene with selected parts in acetal resin, with 316 passivated stainless steel fastenings, brass weights and neoprene seals and gaskets
valve: grey, harder plastic

I know this quite vague but am hoping somebody can help anyway.


texts: How many hydride ions are available in NaBH4?

texts:
Different sources have different answers. In the reduction of an aldehyde or ketone to an alcohol by Sodium Borohydride, how many moles of aldehyde are reduced by one mole of Sodium Borohydride?

While my teacher claims it is 1, Solomons-Fryhle claims it to be 4.


texts: Why do gnocchi float when they are cooked?

texts:
Gnocchi is a kind of pasta made with flour, potatoes and eggs. They are cooked in boiling water and when they are ready to be eaten they float.

Why do they float when they are cooked?

I found two quite different answers on the web:

1) "The buoyancy is responsible for the water vapor generated from boiling water as it creates bubbles that stick to the gnocchi surface bringing them to the waterline." (first answer)

2) "when you cook or boil it, the water inside of the gnocchi will evaporate. As the water evaporate, the water will turn into air and the air will be trapped inside of the gnocchi. It is indicated by the size expansion of the gnocchi.  Those trapped air will make the gnocchi relative lighter to the water which resulting it to float above the water."(second answer)


texts: Does timing matter when adding coconut oil to rice to reduce calories?

texts:
I ran in to a rice recipe that can reduce carbs and calories when adding coconut oil. The exact direction is that you 1. boil water 2. add coconut oil 3. cook rice as you normally would.

My question is, does it change the end result (end with less calories) if I add water, coconut oil, and rice at the same time?


texts: Confusion about the electrolyte in an electrochemical cell

texts: So the cathode is magnesium and the anode copper. The question asks why silver nitrate would not be a good electrolyte. I am confused. Also is the anode always inert in these cells?


texts:
What is the pOH of a 0.0100 F solution of dipotassium phtalate? pKa1 = 2.950 and pKa2 = 5.408 for phtalic acid.

I did it for phthalic acid by calculating pH and then just doing pOH = 14.00 - pH, which gave me pOH = 11.60. Not sure if I did it correctly, I'm only just (re)learning this. I just need a clear and basic explanation, if possible. The two pKa's are what confuse me... which one do I use? I've been searching on google and through my textbook for 2 days now but I'm just confusing myself even more at this point. I know it's probably really easy stuff, but I haven't done chem in 4 years... trying to refresh my knowledge.


texts: Converting 26.62 NOx µg/L into mM (millimolars)?

texts:
I have to convert  a whole lot of nutrient data : $\ce{NH_4}$, $\ce{PO_4}$ and $\ce{NO_x}$ data that is in µg/L into mM (millimolars).

Could someone give me an example for 26.62 $\ce{NO_x}$ µg/L? or 7.73 $\ce{PO_4}$ µg/L? or 14.39 $\ce{NH_4}$ µg/L?

I have a large data set in Excel to convert and send to someone and want to get it right. Any help would be really appreciated.


texts: Taiwan propylene explosions one week ago

texts:
Is it wrong way to use WATER to relieve the big disaster(propylene leak).

What is a better way to relieve propylene leak in a street about large area?

Any possible choice to prevent explosion?


texts: Effect of incorrect volume reading on calculated density value

texts:
When measuring the density using the displacement method, a student read the initial volume of the water too high, but the final volume reading was correct.
  This error would cause the calculated density to be too high or too low?  Explain why.

Wouldn't it be too low because the initial volume is too high?


texts: How can an aromatic ketone be reduced in the presence of a nitro group?

texts:
Is it possible to reduce an acyl group to an alkane, but still keep a nitro group intact without its reduction to an amino group? A Clemmensen reduction would reduce the nitro group, and it seems like other reducing agents will also reduce the nitro group to an amino group. Would some other mechanism be better suited for this reaction?

For instance, how can I selectively reduce 1-(3-nitrophenyl)propan-1-one to 1-nitro-3-propylbenzene?


texts: 3' terminal phosphate (p at the end of RNA sequence)

texts:
I am reading the paper:
Petersheim, M. and Turner, D.H. (1983) Base-stacking and base-pairing contributions to helix stability: thermodynamics of double-helix formation with CCGG, CCGGp, CCGGAp, ACCGGp, CCGGUp, and ACCGGUp. Biochemistry, 22, 256-263.
The p at the end of the sequence apparently stands for 3'-terminal phosphate.
What is the difference between RNA sequences with a 3' terminal phosphate and a "normal" RNA sequence? Why would they consider RNA with a 3' terminal phosphate?


texts: The $\mathrm{p}K_\text{a}$ is the $-\log_{10}$ of the $K_\text{a}$ value for the disassociation of an acid. So how do you get a $\mathrm{p}K_\text{a}$ value for a base? The base produces no hydrogen ions so can’t you only have a $\mathrm{p}K_\text{b}$?


texts:
I am slightly confused about one certain task.

  There are 4 different solutions ($\ce{NH3}$, $\ce{HCl}$, $\ce{NaOH}$, $\ce{CH3COOH}$), their concentration is the same $(c = \pu{1 mol L-1}).$ Which solution has pH that is higher than 7, but lower than 14?

It is obvious that $\ce{HCl}$ and organic acid cannot have such concentration of hydrogen ions. Both ammonia and natrium hydroxide have base properties. $\ce{NH3}$ is a weaker base though. I am not sure how to find the concentration of hydroxide in $\ce{NH3}$ and $\ce{NaOH}$  properly.

Thank you for the explanation.


texts:
Can we have multiple hydride or methanide shifts? Specially in the case where after first shift it becomes less stable and after the second shift it becomes more stable.
For example, the first step of acid catalysed dehydration of 3-methylbutan-1-ol. The step in which H+ is added to the hydroxy group and it departs leaving a carbocation.


texts: Does MOPAC allows calculation of Standard Enthalpy of reaction in this way?

texts:
I am using MOPAC2016 to calculate $\Delta H^\circ_\mathrm{r}$ (and then $\Delta G^\circ_\mathrm{r}$) for a reaction in aqueous phase, at $\pu{298 K}$. I will explain how, and then the question. Finally I give an example. Suppose this simple reaction:

\begin{align}
\ce{A(aq)<=>B(aq)}
\end{align}
Then, $\Delta H^\circ_\mathrm{r}$ can be obtained as:

$$\Delta H^\circ_\mathrm{r} = \Delta H_\mathrm{f}^\circ(\ce{B}) - \Delta H_\mathrm{f}^\circ(\ce{A})$$ where each of those values is what we get on a thermodynamic calculation (also in an optimization) with the name of H.O.F. (heat of formation, HOF).

Formally the question should be: Is that correct to calculate $\Delta H^\circ_\mathrm{r}$ (and then $\Delta G^\circ_\mathrm{r}$) by using the value of HOF for each reactant?

Example

Here is an example of MOPAC output for a thermodynamic calculation, suppose it is the one for molecule $\ce{B}$:

                    CALCULATED THERMODYNAMIC PROPERTIES
                                          *
   TEMP. (K)   PARTITION FUNCTION   H.O.F.    ENTHALPY  HEAT CAPACITY ENTROPY
                                   KCAL/MOL   CAL/MOLE    CAL/K/MOL  CAL/K/MOL

 298.00  VIB.     0.2155D+06                  8205.6617    53.3353    51.9400
         ROT.     0.3572D+07                   888.2813     2.9808    32.9651
         INT.     0.7697D+12                  9093.9430    56.3161    84.9051
         TRA.     0.4009D+28                  1480.4688     4.9680    42.5424
         TOT.                     -670.232   10574.4119    61.2841   127.4474

   *: NOTE: HEATS OF FORMATION ARE RELATIVE TO THE
            ELEMENTS IN THEIR STANDARD STATE AT 298K
              (=  Standard Enthalpy of Formation).

            Hvib:  Zero-point energy is not included.
                   frequencies of less than zero cm-1 are not included.
            Hrot = (3/2)RT
            Htra = (3/2)RT + pV = (5/2)RT

            Heat capacity is Cp, not Cv

          For more information, see: HTTP://OpenMOPAC.net/Manual/thermochemistry.html

With that data table $\Delta G^\circ_\mathrm{f}$ of the molecule $\ce{B}$ should be:
$$\Delta G^\circ_\mathrm{f}= \mathtt{H.O.F.} - TS^\circ= -670.232\times1000 - 298\times(127.4474- S_{atoms})$$
$S_{atoms}$ will be canceled when calculating $\Delta G^\circ_r$.
On this mopac site, $\Delta H_\mathrm{f}^\circ$ appears to be obtained in a similar way, for the $\ce{NH4+}$ molecule.

Am I correct?