texts: Is solubility in Qsp affected by coefficient?

texts:
Related to my previous question: Is solubility coefficient affected if ion data is given in Ksp?

  $200\,\mathrm{mL}$ solution of $0.02\,\mathrm{M}\,\ce{AgNO3}$  is added to $200\,\mathrm{mL}$ $\ce{CrO4^{2-}}$ and $\ce{PO4^3-}$ ions. Find out both of $Q_{\mathrm{sp}}$.

Actually the question is asking "Will it precipitate", but I skip it.

Here is my half approach:

$$200\,\mathrm{mL}=2\times 10^{-1}\,\mathrm{L}$$
$$V_{\mathrm{total}}=400\,\mathrm{mL}=4\times  10^{-1}\,\mathrm{L}$$
$$[\ce{Ag+}]=[\ce{CrO4^2-}]=[\ce{PO4^3-}]=\frac{0.02\,\mathrm{M}\cdot 2\times 10^{-1}\,\mathrm{L}}{4\times 10^{-1}\,\mathrm{L}}=0.01\,\mathrm{M}$$
$$\ce{Ag2CrO4 -> 2Ag^{+} +CrO4^{2-}}$$
$$Q_{\mathrm{sp}}(\ce{Ag2CrO4})=[\ce{Ag+}]^{2} \cdot [\ce{CrO4^2-}]$$
$$Q_{\mathrm{sp}}(\ce{Ag2CrO4})=[2s]^{2}[0.01\,\mathrm{M}]$$

I know that to find $K_{\mathrm{sp}}$, the $s$ needs to be multiplied (and to the power) with the coefficient from the reaction, but how about $Q_{\mathrm{sp}}$? Does the $s$ also need to be multiplied?

I asked this because my teacher said that only to the power is affecting the $Q_{\mathrm{sp}}$.


texts: Dissolving ability of octane vs nonane on neoprene

texts: I have been working with straight chain octane and nonane. The neoprene seals in some parts of the apparatus are allegedly far more vulnerable to the deleterious effects of octane than nonane - why? [I assume it's a solvent thing]


texts: What atom is always paramagnetic and why?

texts:
Regardless of its electron configuration, it must always be paramagnetic when it's a single, neutrally charged atom:
  (A) Carbon (B)
  Nitrogen (C) Oxygen (D) Neon (E) Argon

At first, I eliminated D and E. Then, I tried to find the answer by checking the electron confiurations of the atoms; I saw the phrase "regardless of its electron configuration", but I didn't know what else I can do. Then, I found out that all three atoms (A, B, and C) have some unpaired electrons …

I checked charts with paramagnetic elements filled in; three first pictures on google said different things (check here), but after all the info I have found on the net I understood that C (oxygen) is the most likely answer. I don't understand why … I checked a few videos that said that if an atom has 1 or more unpaired electrons it is paramagnetic; then, A, B, and C are all paramagnetic. A few sites said we need to look not at the elements, but at the compounds (not oxygen, but $\ce{O2}$); the task said, anyway, we are looking at the single, neutrally charged atom.

Please tell if it is oxygen and if yes why it is paramagnetic but other elements are not.


texts: Why isn't organic chemistry taught in 3D?

texts:
As the title says. What's the point of learning everything in 2D and trying to visualize and interpret stereochemistry, newman structures, isomers etc, with hundreds of hours wasted, when a 3d visualization suite could be used to teach everything instead, without any ambiguities as to what the structure looks like? The 2D format seems completely irrelevant besides the communication of chemical structures on paper.

Surely a better system would teach everything in 3D first to gain a true visual and theoretical understanding of the subject, and ONLY THEN taught in 2D on how to simplify things for proper communication?


texts: Are there limits to waters energy absorbtion capacity

texts:
I have a system where I heat water in a flask.
The water vapor generated is condensed and returns to the original container (not a pressurized system, but condensation system is efficient enough that there is no loss of vapor).
My goal is to have maximum amount of vapor. (The real goal is the condensate droplets that filter through plant material to extract water soluble components - Kumagawa extraction)
Question:
Is there a limit or plateau to the amount of energy the water can absorb/turn into vapor?
or
I have a 10l flask and a 1500W heating mantle. If I run the heating mantle at full power is there a possibility that the energy generated couldn't be absorbed by the water in the flask and used in turning it into vapor and thus would heat the electrical control circuits and outer casing of the heating mantle instead.


texts: Is it okay to heat a test tube for several minutes for evaporation of solvent inside?

texts: I have a mixture of water and a small amount of undissolved solute in a test tube. I want to remove the water in it by evaporation method. Can the test tube carries the evaporation process with a Bunsen burner? I don't want to transfer into different glassware to avoid contamination and reduction of the solution when transferring.


texts: How do I calculate the molarity of the Na2CO3 solution?

texts:
My teacher isn't very good at helping me solve this problem. I keep getting the answer, but I don't know why I am getting it. Could you please help me understand this problem and why you should do this specific step?

  A $\pu{1.00 g}$ sample of $\ce{Na2CO3.10H2O}$ was dissolved in $\pu{20.0 mL}$ of distilled water. Additional water was added so as to give $\pu{250 mL}$ of solution. What is the molar concentration of $\ce{Na2CO3}$?

Here is what I did and got the answer and don't understand why I need to do it:

\begin{align}
  \frac{\pu{1 g}~\ce{Na2CO3.10H2O}}{\pu{286 g}~\ce{Na2CO3.10H2O}} &= \pu{0.003447 mol}\\
\frac{\pu{0.003447 mol}}{\pu{0.020 L}} &= \pu{0.174825 M}\\
(\pu{0.174825 M})(\pu{0.020 L}) &= (\pu{0.250 L})(x)\\
x &= \pu{0.013986 M}
\end{align}

$\pu{0.013986 M}$ is the correct answer, but I don't know why and don't understand the question.
If you were to do the problem, could you explain why you did what you did to get to the answer.


texts: Le Chatelier's Principle Having No Effect

texts:
Consider the following equilibrium system:

$$\ce{2 IBr(g) <=> I2(g) + Br2(g)}$$

Would a decrease in the volume of the system effect the equilibrium?

I think it would not affect the equilibrium of the system.

This is because a decrease in volume would increase the pressure of the system. Le Chatelier's principle states that a decrease in volume would favour the side with less moles. Since both sides have an equal amount of moles, there would be no shifting of equilibrium.

A decrease in volume would also increase the overall concentration of all substances within the system. Considering that it affects the overall concentration and not just one side, an increase in concentration would merely increase the rate of reaction. Not the equilibrium of the system.


texts: What is the difference between standard chemical potential (μ standard) and the "pure" chemical potential (μ*)?

texts:
I am studying solutions for my thermodynamics course and I am a little confused about the chemical potential of a solute. I found the following from Atkins:

  For a solute $\ce B$,obeying Henry's Law $p_\ce B=K_\ce B\,  x_\ce B$, where $x_\ce B$ is the molar fraction

$$\mu =\mu^*+RT\ln\left(\frac{p}{p^*}\right)=μ^*+RT\ln\left(\frac{K}{p^*}\right)+RT\ln(x)$$

It then states:

$$\mu(\textrm{standard})=\mu^*+RT\ln\left(\frac{K}{p^*}\right)$$

Therefore, the chemical potential of B in an ideal-dilute sol. is:

$$\mu=\mu(\textrm{standard})+RT\ln(x)$$

The text often states that anything with the * means it is in its pure form, so $\mu^*$ would be chemical potential of $\ce B$ not mixed in with a solvent...but how does this physically differ from $\mu(\textrm{standard})\,?$


texts: How can the hydrogen bonds in solid HF be best represented?

texts:
The hydrogen bonds in solid HF can be best represented as:

The correct answer is supposed to be (c), but I don't understand why this is so. Does the strength of hydrogen bonding depend on the $\ce{F-H\bond{...}F}$ or the $\ce{H-F\bond{...}H}$ bond angles?


texts: How does the room gets heated by leaving a fridge open?

texts:
Question:

  If the door of the refrigerator is kept open, the room in which the refrigerator is kept:

  gets cooled
  gets heated
  neither gets cooled nor gets heated
  gets cooled or heated depending on the initial temperature of the room.

The answer mentioned is option b) gets heated
It doesn't seem convincing that on opening refrigerator's door the room gets heated. Also the radiator emits out the heat in the surrounding. Thus the heat absorbed from the room is released in it and the must neither get cooled nor heated.

Just before posting this question I have tried to experimentally verify this and observed no change in temperature of the room.


texts: Please explain the following graph for a quantum mechanical harmonic oscillator

texts:
Graphs such as the above keep coming up when talking about harmonic oscillators in a quantum mechanical sense. However, I simply cannot make sense of them. What does each line represent why are they waves and what is the parabola? Also, I see sometimes graphs such as:

These seem to follow on from the initial graph. It's something to do with the recovery of classical behavior but I don't understand the first graph so stand no chance of getting the second ones at high n - perhaps you could explain the relation between the first and second graph please? Thanks


texts:
What are the products of the following hydrolysis reaction? How do you know?

$$\ce{NH4NO3 + H2O <=> ?}$$


texts: What comes after f-orbitals, and in what order are they filled?

texts: I know about s, p, d, and f-orbitals. However, my physical chemistry textbook does not mention what comes after f-orbitals. What are the next letters, and in what order are these higher orbitals filled?


texts:
I have tried to find this searching the internet and I am not sure if I understand it. I want to turn water from solid to gas without going into the liquid phase - Sublimation.

The altitude above sea level is 1500 meter about 5000 feet. I have small 1 stage vacuum pump and a cheap vacuum gauge. The pump is rated to 5Pa (at sea level). Atmospheric pressure is around 85kPa. The vacuum gauge reads 20 inHg but what is that in Pascal, if I convert it using Google or the calculator it give me a value of 67kPa.

Two questions:
1. Can sublimation occur at an altitude of 1500 meter above sea level and atmospheric pressure of around 85kPa

How does one convert vacuum inHg into pascal

I am not chemist nor a chemist student and just like experimenting with stuff


texts: Why is a alkyne anion more stable than a benzene anion?

texts: I would think the benzene anion (A) is more stable b/c the compound aromatic. Yes I understand that sp hybridized carbons are more stable than sp2 for negative charges, however I thought that aromaticity is a more important factor in determining stability.


texts: I would like to know the mechanism of this reaction. In my first attempt to the question, I had replaced the two $\ce{Br}$s by $\ce{CH3}$s by $\ce{S_N2}$ of the organometallic compound but the answer given was the above allene. I think my reaction isn't possible because of too much hindrance. So if that's the case, then what is the mechanism of the actual reaction?


texts: Why does more heat transfer take place in a reversible process than in a irreversible process?

texts:
We have defined $$\mathrm dS=\frac{\delta Q_\text{reversible}}{T}$$
and the second law of thermodynamics (Clausius inequality) says
$$\mathrm dS\geq\frac{\delta Q}{T}$$
(Here $\delta Q$ is just the differential of heat regardless of it being reversible or irreversible) and the equality holds for it being a reversible process (as defined).

Now,
$$\mathrm dS\geq\frac{\delta Q}{T}$$
If I put $\mathrm dS$ on the left as $\frac{\delta Q_\text{rev}}{T}$,
I will get $\frac{\delta Q_\text{rev}}{T}\geq\frac{\delta Q}{T}$,
or $\delta Q_\text{rev}\geq\delta Q$.

This implies that in a reversible process, more heat transfer takes place than in an irreversible one. Why is this so?


texts: Reversible and Irreversible adiabatic expansion

texts:
A $\mathrm{200.0\ m^3}$ balloon at $253.0\ \mathrm K$ ascends to a higher altitude. If the initial pressure inside the balloon is $325$ millibar, and it ascends to a latitude with a pressure of $7.45$ millibar, by what percent does the absolute temperature change:

Assuming the process is reversible and adiabatic
Assuming the process is irreversible and adiabatic

All of the formulae I have on this subject include moles. The question does not give a value of moles. Where do I start?


texts: How to calculate the charge on silicates?

texts:
An isolated $\ce{SiO4^4-}$ ion has $-4$ charge. These discrete tetrahedral units form the ortho-silicates. As these tetrahedral units combine, they form various types of silicates.
How do we calculate the total charge on various forms of silicates?
Examples: $\ce{Si4O11^6-}$ has $-6$ charge and so does $\ce{Si2O7^6-}.$ But I am not able to understand how to calculate this charge. Is there any general rule?


texts: Continuous chemical reaction network versus chemical reaction network - difference?

texts:
I'm reading a paper entitled Reachability Problems for Continuous Chemical Reaction Networks and as I was reading it I realized: I have no idea what the difference is between a continuous chemical reaction network (CCRN) and a chemical reaction network (CRN). The paper does distinguish between the two, so they aren't two terms for the same thing. The wikipedia article doesn't distinguish/give a definition for a CCRN. Most of the results when I search google are papers that are way over my head - the one I'm reading right now is to be quite honest over my head.

Any help would be appreciated. Thanks!


texts: Permeability of containers to poop smells

texts:
I do a lot of hiking trips that involve driving for an hour or two to the trailhead in the predawn hours. I'm a morning pooper, so I need to poop during the drive. Before COVID, I would usually plan a stop along the way at a Starbucks, get coffee, and use their bathroom. Then if necessary I'd also use a bathroom at the trailhead. Right now, during COVID, these bathrooms are all closed, so my new normal is that I pull over somewhere in the countryside, poop, collect my poop using one of my dog's poop bags, and bring it with me to a town or trailhead where I can dispose of it.
Sometimes this was stinking up my car, even though the bag was tied shut, so I tried putting the poop bag inside a large plastic (PETE) can that some nuts came in, and sealing it with the screw-on lid. Even then, there have been times when the smell seeped out within 30 minutes. Sometimes the smell has been like sour milk, sometimes like sulfur or eggs.
If I want to make this work better, what should I be focusing on? Is ~0.5 mm of PETE likely to be permeable to the smelly volatile compounds involved? Or is the issue more likely to be that there's a poor seal at the screw threads? Would I be better off trying something like the glass jars with clamping lids that people use for their coffee? A tupperware-style container with an o-ring seal? What kind of material should I be looking for in a gasket or o-ring?
(The other option I've tried successfully is to clamp the poop bag under a windshield wiper, so it's outside. But I'm worried this would, uh, catastrophically fail if I then drove at freeway speeds.)


texts: The Trend Between Boiling Point and Solubility in Organic Chemistry

texts:
Is it true in assuming that a higher boiling/melting point means that an organic compound will be more soluble in water?

I'm trying to distinguish between the solubility of aldehydes vs. ketones based on boiling point. I received a question in a test today about it, comparing propanal with propanone, based solely on boiling points given, and my structural understanding of the two. I thought propanone had lower solubility of the two, as the ketone group is surrounded by carbons, while the propanal is exposed. Scouring through the internet, I'm not so sure my answer was correct!


texts: Reaction mechanism (SN2 and SN1 reactions)

texts:
How to determine whether a reaction is an SN1 or SN2 reaction?
I am unable to determine whether a reaction would form a transition state or not,
I referred the NCERT textbook but didn't found anything that could clear my doubt.


texts:
The correct order of melting point of alkali metal halides is:

$\ce{MF}>\ce{MCl}>\ce{MBr}>\ce{MI}$
$\ce{MI}>\ce{MBr}>\ce{MCl}>\ce{MF}$
$\ce{MCl}>\ce{MF}>\ce{MBr}>\ce{MI}$
$\ce{MI}>\ce{MF}>\ce{MCl}>\ce{MBr}$

The correct answer to this is option (1), the reason I could think of is that as the size of anion in ionic compound increases the covalent character increases and hence the melting point decreases.


texts:
The ion product of water is defined as $$ K_w = [\ce{H+}][\ce{OH-}] $$ and in pure water $ [\ce{H+}] = [\ce{OH-}]= 1.0 \times 10^{-7}$ and $ K_w = 1.0 \times 10^{-14}$. It is said that if we dissolve some acidic substance in water then $[\ce{H+}]$ will increase and $[\ce{OH-}]$ will decrease and the value of $K_w$ remains constant. I understand that $[\ce{H+}]$ increases because acids donate $\ce{H+}$ (according to Brønsted definition of acids) but how $[\ce{OH-}]$ decreases. I mean a water molecule i.e. $\ce{H2O}$ will certainly break into $\ce{H+}$ and $\ce{OH-}$ and to this $\ce{H+}$ our acid has added it's part and hence it's concentration has increased but why the value of $[\ce{OH-}]$ gets lowered from $1.0 \times 10^{-14}$ , if water molecule were to ionize then whenever $\ce{H+}$ gets formed simultaneously we would get $\ce{OH-}$.

I can cite a common example problem

  The concentration of $\ce{OH-}$ ions in a certain household ammonia cleansing solution is $0.0025$. Calculate the concentration of $\ce{H+}$ ions.

We can solve this problem by using the equation $$ K_w = 1.0 \times 10^{-14}$$
$$ [\ce{H+}] [\ce{OH-}] = 1.0 \times 10^{-14}$$
and if put the value of $[\ce{OH-}]$ in the above equation and solve $[\ce{H+}]$, then we would get $ 4.0 \times 10^{-12}$. Here we observe that the value of $[\ce{H+}]$ has decreased from the it's original value in pure water, well this is understandable because ammonia being a base would consume $\ce{H+}$ but how the value of $\ce{OH-}$ has increased.

I want to know that how the chemical reaction can cause the increase or decrease of $\ce{OH-}$ when each molecule of $\ce{H2O}$ always going to yield one $\ce{H+}$ and one $\ce{OH-}$ always.

Thank you. Any help will be much appreciated.


texts: Why can alkoxides leave in the E1cb mechanism?

texts:
Why can alkoxides leave in the $\text{E}_{\text{1cb}}$ mechanism? I refer to the mechanism below. I would think that the anion formed from the first step would be more stable than the alkoxide ion, because the charge on the alkoxide ion is intensified by the electron-donating alkyl group, making it less stable. Correct me if I am wrong.

image source: https://en.wikipedia.org/wiki/E1cB-elimination_reaction


texts: Energies of atomic orbitals on molecular orbital diagrams

texts:
When we plot molecular orbital diagrams we use a linear combination of atomic orbitals.

Where can I find the energies of particular atomic orbitals?

In the picture below, the energies of 2s and 2p orbitals of Oxygen are lower than Carbon's 2s and 2p orbitals of Carbon, what is the logic behind this?


texts: Unusual color from leaking battery. What happened?

texts:
I was removing old batteries from a camera the other day. One of the batteries had leaked something very bright blue. I have seen batteries leak before and typically the colors look a bit like a corroded penny - pale green to white. This time it was a beautiful bright blue; what was it? I initially thought this could have been the metal making the connection was corroding as opposed to the color of the contents of the battery. However, I am not so sure about that.

Note: I believe they were double or triple A batteries and not LiION.


texts: Is there a way to force C-protonation of an enolate?

texts:
In another question, I mentioned that O-protonation of an enolate followed by tautomerization may lead to increased amounts of the thermodynamic product over the kinetic product (when those are different species).

The idea that the oxygen is likely protonated first has been discussed previously.

The way, I think, to get the most kinetic product is to use a bulky acid that would do C-protonation rather than O-protonation (assuming sterics explain the difference in kinetic/thermo product). The proton would have to be a softer electrophile, i.e. less positively charged than a proton from a stronger acid.

To continue with the example I gave in the previous question, I think it's likely that C-protonation would look like this, where the major product would be the kinetic product:

So my question is: are there acids that are known to specifically protonate the carbon of an enolate rather than the oxygen? I was thinking maybe BHT would work. Or maybe the thiol analogue of BHT - yes, it would be more acidic than BHT, but it would also be a softer nucleofuge than the BHT anion. This reasoning works with alkyl halides, i.e. softer leaving group = more C-attack, but I'm not sure if the same goes here.


texts: Producing hydrogen sulfide at home - how dangerous is it?

texts:
When I was a kid, I used to go to the pharmacy to buy sulfur and iron powder, then mix it together and heat it until it starts to react into iron sulfide. Put a chunk of iron sulfide into some vinegar, and you get a room smelling badly of rotten eggs. This experiment was also described in some "chemistry for kids" boxes from the 80's.

Now I'd like to do this experiment with my son, but in the meantime I learned that hydrogen sulfide is a very potent poison, even more poisonous than hydrocyanic acid. For this reason, I'd like to set up some precautions.

Of course I won't do it in a closed room, and I won't let my son breathe in much of the gas.

The gas can be smelled long before it starts to get dangerous, so I think it should be pretty easy to use an amount of sulfur and iron that will cause the characteristic smell, but at the same time is guaranteed to not cause any danger. So, I'm looking for some quantitative estimation:

How much iron sulfide would be enough to create a dangerous amount of hydrogen sulfide? To make the calculation easier, let's assume we grind the iron sulfide and use a stronger acid than vinegar, so that all of the gas will be created almost instantly.

If possible, it would be great to have two estimations: one of the beginning of the "danger zone", and one of the beginning of the "lethal zone". According to Wikipedia, the gas starts to smell at $\pu{0.00047ppm}$, the danger zone starts at about $\pu{10 ppm}$, and at about $\pu{320 ppm}$ it can be lethal.


texts: What does delta letter mean in some ceramics chemical material formula?

texts:
Here is a given chemical formula for ceramic material:
La0.6Sr0.4Fe0.8Ni0.2O3-δ

There is a letter δ. What does it stand for? I guess it is something about oxygen vacancies in crystal lattice.


texts: Paramagnetic molecules are molecules that have single electrons. When I draw the lewis structure of $\ce{O2}$, it appears to be a diamagnetic structure. What makes it paramagnetic?


texts: Dehydration of primary alcohol with a cyclobutadiene substituent

texts:
Note: Primary alcohol will follow E2 mechanism, therefore, removal of protonated water and proton (RDS) shall proceed in a single step in the above mechanism.
My questions are:
1- According to wikipedia "Although the parent compound has not been isolated, some substituted derivatives are robust and a single molecule of cyclobutadiene is quite stable."
As cyclobutadiene is not a stable compound, Is the primary alcohol (reactant) a stable compound?
2- Is the ring expansion step and the final product (benzene) correct?


texts: Mechanism of oxidative dearomatisation with hypervalent iodine

texts: The following step was taken from the synthesis of Kinamycin C on SynArchive. It employs the use of a peculiar reagent, that is, bis(acetoxy)iodobenzene (BAIB), also known as phenyliodine(III) diacetate (PIDA). Being a high-valent iodine species, it is used as an oxidising agent in organic chemistry. So clearly, there is some sort of oxidation taken place in this step, along with nucleophilic aromatic substitution involving an $\ce {MeOH}$ molecule. However, I am quite uncertain as to what is the mechanism by which this step takes place.


texts: Can a substance be extracted from solution by adding another substance with a higher solubility?

texts:
Suppose that I have a substance X dissolved in water. I then add a substance Y to the solution. Substance Y has a higher solubility in water than substance X, and more than enough of substance Y is added to saturate the water. Will substance X come out of solution? Why or why not?
For example, let's have X be sodium chloride and Y be sucrose.


texts:
I know that $\Delta x = x_2 - x_1$. This is well known
Therefore, it follows that $\frac{\Delta a}{\Delta b}$ = $\frac{a_2 - a_1}{b_2 - b_1}$ (Unless I missed an elementary math class!)

Now, I found an equation in chemistry, while reading, that turns this principle on its head. It proposes that when considering the second in a set of values:
$\frac{\Delta^2 a}{\Delta b^2} = (a_3 - a_2) \times \frac{1}{\Delta b}$

My issue with this is that $a_3$ hasn't been measured yet, we have only $a_1$ and $a_2$ so how can this be?

Secondly, they propose this:
$\frac{\Delta \left(\frac{\Delta a}{\Delta b}\right)}{\Delta b} = \frac{\Delta^2 a}{\Delta b^2}$

Can anyone please help with the logic behind the first equation and algebra behind the second one?


texts: pH implications of redox balancing half reaction method

texts:
I have seen similar questions, but I’m asking a new question as far as I know. Why is water instead of hydroxide ions used to balance oxygen atoms in redox half equations? asks about using hydroxide instead of water and that is closest.

I have seen example problems where $\ce{H+}$ is produced or consumed, $\ce{OH-}$ is produced or consumed, and water is used to balance. My thought is that each of these changes affects the $\mathrm{pH}$ or $\mathrm{pOH}$ of each solution.

If the solution is already an acid, there is an abundance of $\ce{H+}$ and it makes sense to me that a reaction may use excess $\ce{H+}$ to make the solution more neutral. One could make the same argument about using up excess $\ce{OH-}$ in a basic solution. What doesn’t make sense to me is adding to the basic or acidic nature. See example below which was specified to be in a basic solution. It appears to be making the solution more basic by producing more $\ce{OH-}$ instead of using it up. Shouldn’t that be less likely to occur? Why not? What am I missing?

$$\ce{6I- (aq) + 4H2O + 2MnO4- (aq) —> 3I2 + 2MnO2 (aq) + 8OH- (aq) }$$


texts: Determining order of a reaction without isolation

texts:
I'm writing a computer program to calculate the order of a chemical reaction with respect to each reactant. When I do this by hand, it's easy to isolate which reactant concentration stays relatively the same while the others change. However, when you don't have an isolation method available, is there a non-guess and check way to determine rate orders?

For example, with the sample data of a 1st order reaction with respect to A and B, and second order overall

+--------+-----+-----+------+
| Trial# | [A] | [B] | Rate |
+--------+-----+-----+------+
|      1 |   1 |   1 |   10 |
|      2 |   2 |   3 |   60 |
|      3 |   3 |   2 |   60 |
+--------+-----+-----+------+

There isn't a trial with two constant values, so I'm not sure how you would programmatically determine the orders with respect to each of the reactants without manually trying every possibility until one fit (I realize that this wouldn't take too much computing time to do, but it won't scale well for multiple trials, and I also would prefer a non-brute force solution if possible). If there is no way to determine the rate with respect to each reactant, is there a way to determine the overall rate? This would greatly reduce the number of possibilities of orders when faced with larger rates


texts: How are hydrogen atoms formed in hydrogen discharge tube?

texts: I (partially) understand how a breakdown voltage is applied, then the gas is ionized to cations and electrons. Then the electrons will accelerate to the cathode and knock off more electrons from other H2, creating a current ( which is the flow of electrons ). The electrons might excite the gas and the gas emit light as it goes back to normal state. If that the case the shouldn’t in hydrogen discharge tube, the spectral lines observed are those of hydrogen molecules (the gas)? And how does it atomize to give the hydrogen spectral lines?


texts: Is it possible to use Vmax as Kcat in a Michaelis-Menten reaction?

texts:
I am studying a biological system using ODEs. As part of my work I need to use the '$k_\text{cat}$' version of the Michaelis-Menten reaction, which is:

$$\frac{V_\text{max}\cdot [\ce{S}]}{(K_\mathrm m+[\ce{S}])} = \frac{k_\text{cat} \cdot [\ce{E}_\text{free}] \cdot [\ce{S}]}{(K_\mathrm m+[\ce{S}])}$$

I have found in a publication a value of a $V_\text{max}$ for one of my reactions:

$$V_\text{max}=\mathrm{\frac{11.4\;pmol}{min^{-1}{\;pmol^{-1}\;enzyme}} = \frac{0.19\;nmol}{s^{-1}\;nmol^{-1}\;enzyme}}$$

My question is, since this $V_\text{max}$ value is quoted in terms of 1 unit of enzyme (i.e. 0.19 nmol is the maximum one nmol of enzyme can catalyze in a second), can I use this $V_\text{max}$ value as a $k_\text{cat}$?

here is the abstract I found the information from :

  Retinoic acid (RA) is a critical signaling molecule that performs
  multiple functions required to maintain cellular viability. It is also
  used in the treatment of some cancers. Enzymes in the CYP26 family are
  thought to be responsible for the elimination of RA, and CYP26A1
  appears to serve themost critical functions in this family. In spite
  of its importance, CYP26A1 has neither been heterologously expressed
  nor characterized kinetically. We expressed the rCYP26A1 in
  baculovirus-infected insect cells and purified the hexahistidine
  tagged protein to homogeneity. Heme incorporation was determined by
  carbon monoxide difference spectrum and a type 1 spectrum was observed
  with RA binding to CYP26A1.We found that RA is a tight binding ligand
  of CYP26A1 with low nM binding affinity. CYP26A1 oxidized RA
  efficiently (depletion Km
  9.4  3.3 nM and Vmax 11.3  4.3 pmoles min1 pmole P4501 ) when supplemented with P450 oxidoreductase and NADPH but was independent of
  cytochrome b5. 4-Hydroxy-RA (4-OH-RA) was the major metabolite
  produced by rCYP26A1 but two other primary products were also formed.
  4-OH-RA was further metabolized by CYP26A1 to more polar metabolites
  and this sequential metabolism of RA occurred in part without 4-OH-RA
  leaving the active site of CYP26A1. The high efficiency of CYP26A1 in
  eliminating both RA and its potentially active metabolites supports
  the major role of this enzyme in regulating RA clearance in vivo.
  These results provide a biochemical framework for CYP26A1 function and
  offer insight into the role of CYP26A1 as a drug target as well as in
  fetal development and cell cycle regulation.


texts: Guidelines for Solubility in Water of Organic Compounds in Relation to Carbon Chain Length

texts:
Is there a way to generalize the solubility of any organic compound based on their functional groups and the length of their carbon chains? I know that beyond 3 carbons, alcohols are insoluble, and beyond 4 carbons, carboxylic acids are insoluble. But what if the alcohol had 2 hydroxyl groups? What if the carboxylic acid had 2 carboxyl groups? How many carbons would they each need for the compound to become insoluble in water again? Are there any quantitative guidelines for determining this?
And what about the solubility of esters and haloalkanes? How many carbons does an ester and haloalkane need to have for them to be insoluble? Again, what if there are multiple ester or halide groups?
Lastly, how do you determine solubility when you’ve got a mixture of functional groups? Take aspirin for example, whose structure contains a benzene ring of 6 carbons, a carboxyl group attached to one corner, an ester group attached to another corner, and one methyl group attached to the ester. How would you systematically determine if this compound was soluble in water or not?

(Image credit: http://www.rxlist.com/images/rxlist/aggrenox2.gif)


texts: How to determine which gas would have the lowest pressure?

texts: If the volume of each sample of gas was reduced to one-tenth of its original size and the temperature remained the same, which gas would have the lower pressure. I'm getting confused because my options are $\ce{C6H4}$, $\ce{C3H4}$, $\ce{N2}$, $\ce{O2}$, and $\ce{Cl2}$. Our teacher told us to pick the polar compound but the problem is all of them are non polar. Would the answer be $\ce{C3H4}$? I have a feeling I might be drawing the lewis structure wrong because I'm positive the other four are non polar.


texts: Just wondering why the name of this compound is 3-phenylpropene? I understand the concept of phenyl groups but I'm confused where the 3 came from, because if it is referring to the double bond in propene, then shouldn't it be numbered 2?


texts: Nucleophilicity in polar aprotic solvent (DMSO)

texts: The strength of a nucleophile in polar aprotic solvent is proportional to its basicity. Lone pair on O- in the molecules will donate an e- pair to an atom. I'm not sure why the alkene ring in 2 makes it a worse nucleophile compared to 1. Benzene ring is more stable than cyclohexane but the double bond is not the nucleophile in the molecule. Is it due to steric hindrance?


texts: exchanging H2O in buffer for D2O - pH vs pD?

texts:
I have TBS pH 7.4 buffer that I am exchanging all the water out for $\ce{D2O}$. How do I find out what the pD is after all the water is gone? I understand that pH meters don't work for deuterium, and it seems like deuterium also changes the spectral properties of the chromophores in pH paper (or in this case pD paper)

Also, if I want to best mimic the alkaline conditions in $\ce{D2O}$ as $\ce{H2O}$, should pD final = pH initial?


texts: What is the origin of the maximum in rotational heat capacity?

texts: The graph of rotational heat capacity above shows a small maximum before approaching the equipartition value. What is the origin/physical explanation of this maximum?


texts: Why doesn't a catalyst shift the position of equlibrium, when temperature does?

texts:
Maybe this is a silly question, but it's not one I've been able to answer to my own satisfaction. Increasing the temperature of a reaction favours the endothermic direction, because it makes it relatively more likely for particles to collide with enough energy to make the activation energy. Yes?

But doesn't lowering the activation energy have almost the same effect on the relative likelihood of particles colliding at least that energetically? Someone on a related question about whether catalysts shift the position of equilibrium said:

  The energy difference between the reactants and products is unchanged
  by catalysis

But isn't that equally true for increasing the temperature?


texts:
Is there any equation that can calculate the triple point of a substance? Because a method for calculating the critical temperature and the Boyle temperature of a substance that I posted in another question I recently found that it also seems to be able to predict the triple point for some substances.

I searched the Internet and couldn't find any other such equation, in fact I came across a site that said there was none. Is this true?  My equation predicts it from the Lennard-Jones parameters. Source:

Here is an excerpt from a document that I'm putting together. It also predicts the reduced triple point temperature to be 0.5


texts: Can a molecule contain a linear series of conjugated pi bonds twisted through 180 degrees?

texts:
Imagine a long chain of carbon atoms connected by single and double bonds in conjugated fashion. All of the p orbital pi bonds would normally be aligned to either side of the carbon atoms forcing the molecule to adopt a flat structure.
Would it be possible to take this structure and twist it slightly so as to form a long helical shape?

The bond overlap would not be as good but if the chain were long enough I would have thought the bond weakening would not be excessive.
Obviously both ends would need to be firmly bonded to some other inflexible linking components such as a large protein molecule or a long chain of aromatic rings.

Has anything like this ever been synthesised? Is it even possible?

Here is an example either end of this structure would be connected to a larger molecular segment that would hold it in place and prevent it from untwisting. I want to give this normaly flat structure a 180 degree twist.


texts: Why is phloroglucinol (1,3,5-benzenetriol) not very soluble in water?

texts:
Wikipedia says that phloroglucinol (1,3,5-benzenetriol) has a solubility of 1 g/100 ml in water.  This is in comparison to:

phenol (hydroxybenzene) 8.3 g/100 mL
catchecol (1,2-dihydroxybenzene) 43 g/100 ml
resourcinol (1,3-dihydroxybenzene) 11 g/100 ml
hydroquinone (1,4-dihydroxybenzene) 5.9 g/100 mL

Why does it have such a low solubility?  I would have thought the OH group would make it more soluble.


texts:
I've noticed a phenomenon in the EI-MS spectra of aliphatic aldehydes. Many of them show a significant peak (sometime it's even the base peak) at $M-28$.

To my best understanding, the only thing that can explain this – and is common to all aldehydes – is removal of the carbonyl $\ce{C=O}$ group.
However, I fail to understand the chemistry behind this. How can the $\ce{C=O}$ disconnect, while the aldehyde hydrogen stays – somehow replacing the entire group (forming a new $\ce{C-H}$ bond)? Or am I missing something and this is not actually removal of the $\ce{CO}$?

For example, here is the EI-MS spectrum of (2Z)-3-methylpent-2-en-4-ynal:

Molecule drawing from www.chemspider.com:


texts: What is electron configuration used for?

texts: What is the purpose of writing electron configuration vs just using the number of electrons off of the periodic table. I know it can be used to determine the number of electrons in each energy level, and therefore, the number of valence electrons. Is there anything else? The number of valence electrons can be found from the periodic table, so why go through that process?


texts: At what temperature do complex hydrocarbons become ashes?

texts:
When heating a metal tube with polypropelene in it, i found that i still had brittle black foam and flakes in it even though it had been in a blue flame at around 500'C

What happens to complex hydrocarbons/plastics when they turn into black foam at high temperatures?
At what temperature do tars and heavy hydrocarbons completely lose all their Carbon and only ashes are left?


texts: Is methyl phenyl sulfoxide optically active?

texts: I am concerned about the stereogenic centres. But in this compound there is no chiral centres present. Sulphur is $\mathrm{sp^2}$-hybridized, so it cannot be chiral anyway. But I can see there is no symmetry present in this compound. Will this be a sufficient reason to tell the compound optically active?


texts: What is the formula for heat of vaporization under reduced pressure?

texts:
I haven't taken a chemistry class in several years, and I have honestly been searching the web for the past hour and can't find anything. I know this is something basic we learned back in high school chemistry but maybe I am not searching for the right term...

Is there a formula? I know how to calculate distillation speed based on wattage, and the vaporization constant of the molecule, but cannot find any particular formula that can calculate how that number changes under reduced pressure.


texts: Why does alcoholic KOH prefer elimination whereas aqueous KOH prefers substitution?

texts: What is the basic difference between aqueous and alcoholic $\ce{KOH}$? Why does alcoholic $\ce{KOH}$ prefer elimination whereas aqueous $\ce{KOH}$ prefers substitution?


texts: In both cases ring expansion is happening. What is Carbon tri chloride purpose?


texts: Finding the amount of nitrous oxide produced in the reaction between lead sulfide and nitric acid

texts:
Lead(II) sulfide dissolves in excess nitric acid according to the equation below. Calculate the volume of $\ce{NO{(g)}}$ at $\pu{27 ^\circ C}$ and $\pu{1.10 atm}$ produced from $\pu{4.7 g}$ of $\ce{PbS(s)}$.
$$\ce{3PbS{(s)} + 2NO3–{(aq)} + 8H+{(aq)} -> 3Pb^2+{(aq)} + 3S{(s)} + 2NO{(g)} + 4H2O{(l)}}$$
a) $\pu{0.29 L}$
b) $\pu{0.44 L}$
c) $\pu{0.66 L}$
d) $\pu{30 L}$
e) $\pu{45 L}$

I used the ideal gas formula and converted the mass of $\ce{PbS}$ into number of moles of $\ce{PbS}$ however got the answer b) $\pu{0.44 L}$ which is incorrect. The correct answer is a) however I am unsure about. Why this is?


texts: What is the best way to detect the presence of tear gas?

texts:
I realise that tear gas can be several different things (Pepper spray / CS Gas / CR gas, PAVA, etc)

Is there a good way to detect some or any of these in the air?
Ideally using an electronic sensor that can be reused?


texts: How do we assign alpha/beta status in polysaccharides?

texts:
In polysachharides like sucrose or any other disachhaharides, how is it that we assign whether the glycosidic bond is alpha/beta ?

For example the images here: http://forums.studentdoctor.net/showthread.php?t=898328 (kindly refer to the images of the original question, both of them)

How does one decide which glycosidic bonding is alpha and which is beta ? What if one of the monosachharides is alpha and one is beta constituting the disachharides ? How do you know that in the final acetal formation which sachharide acted as nucleophile and which acted as electrophile after seeing the disaccharide , take for example sucrose , glucose/sucrose (?) which acted as nucleophile any why ?


texts: What is the simplest way to create a precipitation reaction at home?

texts:
What is the easiest way to create a precipitation reaction at home, preferably with easily retrievable chemicals?
I need this because I'm making a video for my film education.


texts:
I've heard both of the following:

An orbital is a region where there's a 90% probability of finding an electron
An orbital is a region where an electron spends 90% of its time

Are these essentially the same things? Or which one is correct and why?
Edit- I've heard both from veritable sources and only need a confirmation not a precise definition.


texts: Why doesn't 1,3-dichloro-2,4-dimethylcyclobutane have a plane of symmetry?

texts:
In (1R,2R,3S,4S)-1,3-dichloro-2,4-dimethylcyclobutane, are the blue lines not planes of symmetry?

My book says it has a centre of symmetry, but not a plane of symmetry.  But if I took a cut through any of the blue lines wouldn't both sides be symmetrical?


texts: I live in the tropics, and have a water tank that sits in the sun, forming algae. Every year, I need to scrub the thing out. The plumber I’ve hired for the job wants to flush my water pipes with HCl to kill any residual algae. The pipes are mostly PVC, with braided metal hose and metal fittings here and there. Should I let him? If not, why not?


texts: Why is the entropy of deuterium greater than that of hydrogen gas

texts:
Why is the entropy of deuterium more than that of hydrogen gas?

I thought about it but couldn't figure out a reason for why that would happen. Why would the number of neutrons in the nucleus affect the entropy of the gas?


texts: Reaction of carbonyl cyclic diene with Grignard reagent

texts:
Predict the major product of this reaction:

The two compounds on the right are the possibilities that I thought of (weren't given in the question). According to me:

attack on carbonyl carbon by $\ce{MeMgBr}$ and then hydrolysis with $\ce{aq. HCl}$
first tautomerise to form phenol. $\ce{MeMgBr}$ will remove acidic proton of phenol. The $\ce{aq. HCl}$ workup will then add the hydrogen back to phenol.

I an confused as to which product would be the major product. I thought phenol would be the major product. But to my surprise, the answer given is 1-methylcyclohex-2-enol. I am not able to understand how it is formed, and need help here.

Source: Joint Entrance Exam (JEE) 1997 India


texts: Why does the "gap" between atomic radii get smaller down the periodic table?

texts: The question asks: why is the difference in atomic radii between $\ce{K}$ and $\ce{Na}$ larger than the difference in atomic radii between $\ce{Cs}$ and $\ce{Rb}$? I do have some kind of notion that the gaps between shells decrease as you go down the periodic table, but why would this be the case?


texts: I found transition states (TS), but calculations aren't supported by experiment. Do I look for more TSs or somewhere else?

texts:
I'm using Gaussian to investigate a catalyst system.

Experimental evidence showed that one of three analogues (R = phenyl, Ph), yielded a benzosultam

when treated with 2,4,6-triisopropylbenzenesulfonyl azide (N_3Trisyl).

Running the reaction at 70 °C over 65 hours, an 84% yield was observed.

There was no benzosultam yield when either of the other two analogues (R = neopentyl, NeoP, and R = trimethylsilyl, SiMe_3) were reacted with N_3Trisyl under the same conditions. I hypothesized that differences in activation energies for the C-N bond forming reaction were the root of the observed reactivity differences.

I'm using the BP86 functional, with 6-31G(d,p) basis sets, GD3BJ dispersion corrections, and the CRENBL ECP applied to chromium. Benchmarking for thermodynamic properties was done against  reaction enthalpies and activation energies from a set of 3 chromyl chloride hydrogen atom abstraction reactions done by James Mayer. A second set of coupled cluster calculated X-H and X-X bond dissociation enthalpies was also used. The BP86//6-31G(d,p) method with CRENBL ECP applied to chromium and GD3BJ dispersion correction gave mean absolute errors in the range of 4kJ/mol for Mayer's activation energy data, 14 kJ/mol for Mayer's reaction enthalpy data, and 10 kJ/mol for enthalpies in the coupled cluster set.

I used Gaussian to optimize structures of the transition states, reactants and products for each of the three analogues. From my results, I calculated activation energies for the C-N bond forming reaction for each analogue, as well as standard reaction enthalpies, entropies, and free energies. I calculated activation energies in the range of ~6-22 kJ/mol, with R = Ph being the lowest, as well as negative free energies of reaction, and favorable entropies and enthalpies of reaction for every analogue. These results suggested that some benzosultam should have been observed for the R = NeoP and SiMe_3 analogues.

So now I'm stuck. The reaction should be spontaneous at every temperature, according to my calculations. But it isn't.

Now I think I'm looking in the wrong place.

Maybe I want to look for intermediates and a second transition state?

I'd assumed the energy diagram for the reaction looked like this

, a single hump with reactant and product on either side), when it might actually look like

. Meaning I could have calculated TS2 (in the second diagram) for each analogue, and ignored TS1, I'd have been looking at the wrong reaction step.

There's also a possibility my method is inadequate.

Or maybe I'm calculating energies using reactant and product structures which are at local, but not absolute, minima.

Where do I go from here? What's the best use of my time? Is there a way to search the energy surface around the products and reactants to find lower energy conformers? Is there a way to search for intermediates and additional transition states? I feel a bit lost here.

TL;DR: Thermodynamic properties that I have calculated for a catalytic bond forming reaction are not supported by experimental results. So, now I have the choice of revising my hypothesis and searching for another set of transition states and some intermediates, or searching the energy surface around my reactants and products for lower energy conformations. Do these choices sound reasonable given the data and evidence I've collected? Am I overlooking something? What to do?


texts: Triphenylphosphine (PPh3) vs. 1,2-bis(diphenylphosphino)ethane (dppe) ligand?

texts:
What about $\ce{NiCl2(dppe)}$ makes it a more efficient catalyst for Suzuki cross-coupling as opposed to $\ce{NiCl2(PPh3)2}$ or $\ce{NiCl2(PCy3)2}$? How does the dppe ligand increase the reactivity of the catalyst?

Literature claims:

The experiment I am following is from J. Chem. Educ. 2017, 94(6), 786-789 (https://doi.org/10.1021/acs.jchemed.6b00273). The supporting information contains class data which says that the turnover number using a dppe ligand is roughly 4 times that of $\ce{PCy3}$ or $\ce{PPh3}$. The paper suggests that increasing electron ability increases catalytic activity, so what about electron donating ability changes catalytic activity and what makes dppe more electron donating?


texts: Are (1R,2S)‐1,2‐dibromocyclopentane and (1R,3S)‐1,3‐dibromocyclopentane positional isomers?

texts: Are these positional isomers or not? According to me they are, since Br substituent is located at different positions in both the pictures, but the answer key in one of my mock test websites says they're not. Can someone please guide me?


texts: Acidic strength of para substituted benzoic acids

texts:
Comparing the acidic strength, the nitro-substituted group is definitely more acidic. This can be reasoned by fact that a higher delta positive charge which develops on the H due to the strong -M nature of the nitro group.
Another way to check the acidity is to check the stability of the conjugate base.

The conjugate base would be the carboxylate ion which being a -M group creates a lesser electron density at the ortho and para positions. This positive charge is however stabilised by the methoxy group, which is a +M group, and destabilised by the nitro group. So from this viewpoint, the methoxy derivative should have been more acidic.

Why is this not so? What is the fault in my reasoning?


texts: Finding molarities of individual reagents given the chemical equation and total concentration in a container

texts:
I am given a table that gives me the different total pressures at certain times. The decomposition of phosphine is the reaction:

$$\ce{4 PH3(g) <=> P4(g) + 6 H2(g)}$$

The time/pressure values are:

\begin{array}{rr}
\mathrm{time\ [min]} & \mathrm{pressure\ [Torr]} \\
\hline
0 & 100 \\
40 & 150\\
80 & 167\\
100 & 172\\
\end{array}

This reaction takes place at 950K. I can then find the molarity of the total gas mixture at each time using $$\frac{n}{V}=\frac{P}{RT}$$

I need to know how to get the pressure of the $\ce{P4}$ for each individual time. How would one go about doing this?


texts:
I'm looking for a software which can solve chemical equations. For example something like this (given with result):

\begin{align}
    \ce{CH4 + 2O2 & → CO2 + 2H2O} \\
    \ce{C3H6 + HCl & → C3H7Cl}
\end{align}

Is there are such software? I'm studying chemistry as a hobby and want to check if I'm doing the reactions correct.


texts: Why is tetrathiocyanatocobaltate(II) blue?

texts:
Why is $\ce{Co(SCN)_{4}^{2-}}$ blue?

I simply can't predict the colors of such inorganic salts. I have learned that $\ce {Co^{2+}}$ salts are pink in color. Also, if the ligand is a strong field ligand ($\ce {SCN-}$ in this case), then the splitting is more and the color should shift to the red side...

Is my concept wrong?


texts:
Water molecules are described as an oxygen atom covalently (ignoring for the monent protonization/deprotonization) bonded to two hydrogen atoms with an angle of ~104° between the hydrogen atoms (like Mickey Mouse). I can understand this with multiple water molecules (the stacking would - for want of better descriptive powers - surround the oxygen's relative negative charge.)

Would a single water molecule retain this configuration? It would seem that in space, it should look like CO2?


texts: Variation of cone angle with concentration of fuel-air mixture

texts: A stoichiometric fuel-air mixture flowing in a Bunsen burner forms a well-defined conical flame. The mixture is then made leaner. For the same flow velocity in the tube, how does the cone angle change?


texts: What proof is there that the "Island of Stability" exists?

texts: Often I see people talking about an "Island of Stability" existing for super-heavy elements on the periodic table, but I don't see any reason to thinks this exists? Surely the heavier you go the more unstable nuclei get? What, if any, proof or theory is there behind expecting an "Island of Stability" to exist?


texts: What types of energies can be determined by molecular dynamics in gas phase or explicit solvents?

texts:
For molecular dynamics in the gas phase I've seen that electronic energy can be determined and also decomposed in kinetic and potential energy. I've also seen that we can include ZPE. But can we determine (changes in) $\Delta H $, $\Delta S $ and $\Delta G$?

And how about explicit solvent systems? In particular I'm interested if it's possible to determine the free energy of activation and the entropy of activation for reactions in explicit solvent systems. Is it possible to determine such energies for the whole system or even for only the reacting molecules (if that makes sense to do)?

To add: I'm talking about using QM (DFT) for the molecular dynamics. Not molecular mechanics.


texts: Can anybody tell me what this glassware with a stem, bulb and long tube is?


texts: Determining the coupling on a substituted benzene ring

texts:
I can't seem to find any clear explanation of how benzene ring protons couple with each other when mono and disubstituted with the same constituent.

My professor claims that if a benzene ring is para disubstituted with X, the remaining 4 protons exhibit a doublet interference pattern. This seems strange to me because they are equivalent, and my last two organic chemistry professors said the information isn't useful diagnostically, but never explained why.

Also, he claims that if a benzene ring is monosubstituted the proton in the para position will display a triplet interference pattern. Is this right? Symmetry seems to say that the proton would be a doublet.

Do benzene rings have their own rules for coupling?


texts:
When filling an orbital diagram of an atom, usually the up-spin is filled first and then the down-spin.

For example, for Nitrogen, we have :

But in a model in which up-spin electron is preferred over electron down-spin, there would be many problems.
One such problem would be that bond formation due to orbital overlapping requires the electrons in a shared pair to be of opposite spins, so if all unpaired electrons are up-spin in an Nitrogen atom, then Dinitrogen shouldn't exist.

So as per the title, Is one electron spin preferred over the other in filling of orbitals?


texts:
I was thinking about what exactly happens at the triple point of water, and what could be the effect of adding solutes/solvents. I feel we can represent the triple point using the following equilibrium reaction:
$$\ce{H2O (s) <=> H2O (l) <=> H2O (g)}$$

Is this correct? How would this change if I add solutes?

Note: I know that adding solutes would increase the concentration of the solution, but how exactly will it shift the equilibrium?


texts:
Why $\ce{I2}$ is formed when $\ce{HI}$ and $\ce{HNO3}$ are reacted?

I know that $\ce{HI}$ is more acidic than $\ce{HNO3}$ so nitric acid will accept protons from $\ce{HI}$, so $\ce{I-}$ (iodide ion ) should be formed and nitric acid on accepting proton would form $\ce{H2NO3+}$ but that is not formed why?


texts: The quartic electronic state of octahedral Fe(III): How make crystal field splitting diagram?

texts: Using simple arguments from crystal field theory, how do I rationalize the quartic state of octahedral Fe(III)? I am not able to in a logical way distribute the 5 d electrons in such a a way as to end up with three unpaired electrons in the normal splitting diagram for octahedral complexes.


texts: Why is it that protons and electrons undergo the same amount of deflection in an electric field if they have the same energy?

texts:
The question I have is with respect to this diagram. Which depicts a stream of protons and electrons entering a proton field with equal energy.

Why is it that in the case where the energy of protons and electrons are equal, their angle of deflection is exactly the same? However when speed is kept the same, the deflection of electrons is greater. Why is this so?


texts: Drying solvents while taking care of purity

texts:
I need to dry some solvents like $\text{MeOH, EtOH, and  DMSO} $ and I have to take care of purity of the solvents. These solvents are HPLC grade.

I am interested in freezing point and boiling point of these solvents  with maximum error of $ \pm  0.5  C$, hence, I do not prefer to add silica gel (or other dehydrating agent) in the flask containing solvent.

What are other ways to dry solvents without putting something in them.


texts: What is the "mechanism" of the decomposition of hydrogen peroxide?

texts:
In my classwork on the decomposition reaction of hydrogen peroxide by catalase, I wrote the following equation:
$$\ce{2H2O2 -> 2H2O + O2}$$
However, my teacher said that I should go further in depth and write down the (quote unquote) "mechanism" of this reaction. I'm not sure what he is talking about, can anyone help me?

EDIT: I am an IB student studying chemistry in Standard Level so the answer to the above problem should remain within the scope of the IB syllabus. Here's more information from my teacher:

“Although we show reactions in one neat equation, the majority of reactions occur in a series of steps. (…) There’s three step to that (the one above) reaction and catalase will act on one of those steps to reduce the activation energy and therefore make the reaction faster”.


texts: Is activation energy related to reactivity?

texts:
I understand that activation energy is a property of a reaction.

If a substance is highly reactive, will it have low activation energy and vice versa ?
How is the activation energy calculated and what are the factors that affect it?


texts: What is the electrical conductivity of pool water? I tried to find some information, unfortunately without success. I need to know it to make an underwater electronic project.


texts: Food Concentrate For Baking Using Hard Alcohol ex. Jack Daniels

texts:
I am trying to find a way to use hard alcohol such as Fireball, Jack Daniels, Sailor Jerrys and so on and turn them into a baking concentrate. This means the flavor of the alcohol cannot burn off at a high heat. Will xanthan gum or gum Arabic used to make baking concentrates with fruit juice provide the same effect? Or is there a way to take the flavor of the alcohols and turn them into a food concentrate? I just need the flavor not the alcohol itself so if burning off the alcohol which is the actual part that seems to be burning off since it boils at a much lower temperature than water I can do that. Thank you in advance for your time and help.

Cheers,
Savannah


texts: What dangers/risks are there in the production of carbon subnitride?

texts: I was reading that carbon subnitride or Dicyanoacetylene has one of the hottest flames when used as a fuel, but it also is unstable and can explode easily into carbon powder (no specifics on cause).  The only thing I know about its production is that it requires extremely hot graphite to have nitrogen blown on it.  What specific risks are there in producing it or storing it, and how does it get produced and stored safely?  For example is it safe to store at room temperature? Can it be produced safely in a normal atmospheric environment?


texts: How does a copper piece added in nitric acid change after nitrogen dioxide starts appearing?

texts:
There's an experiment I have no way of performing but want to know its results. The instructions (in short) are:

Dip a piece of copper in a glass of concentrated nitric acid, $\ce{HNO3}$, using a pincette. When a brown gas starts forming, take out the piece of copper and rinse it with water. Right after that dip it into $\ce{HgNO3}$ solution. Leave it in there for some time and then take it out of the solution. Rinse it with water and wipe it with a napkin.
How does the piece of copper look?

What I've worked out is that the first part can be written as:
$$\ce{Cu (s) + 4HNO3 (aq) -> Cu(NO3)2 (aq) + 2NO2 (g) + 2H2O(l)}$$
and that $\ce{NO2}$ is the brown gas.
What I'm  not sure about is why exactly I'm dipping the copper piece into a solution of $\ce{HgNO3}$ following the above reaction. And why am I rinsing it with water before dipping it into the $\ce{HgNO3}$ solution?


texts: Is there a type of detergent/surfactant that evaporates at STP?

texts:
Are there any type of detergent/surfactant chemicals that would be good for removing dirt and grease from fabric that also would evaporate from the clothes within, say, 24 hours leaving no residue?

Googling "volatile surfactant" turned up fluorocarbons and something called Surfynol 61, which is really 3,5-Dimethylhex-1-in-3-ol as possible candidates. I don't know if these would be safe for laundry.


texts: Do Na or Li need heat in order to react with Cl₂?

texts: I've read how putting a burning piece of sodium in chlorine would produce white $\ce{NaCl}$ fumes. However, I can't find out whether Na or Li can react with $\ce{Cl2}$ without heating or burning.


texts:
Theoretical chemistry is nowadays almost synonymous with computational (and usually quantum) chemistry.
Are there any examples of recent (let's say post 2000) research in chemistry that is theoretical (i.e. non-experimental) but does not use extensive computations (i.e. HPC), does not aim to produce better computational methods, or does not investigate mathematical foundations of computational chemistry methods?
Something I imagine can exist are models or model Hamiltonians in quantum chemistry that are analytically solvable (or with minimal help from computers), or abstract mathematics like topology applied to chemistry.


texts: What's the density of a frozen ethanol or ethanol solutions?

texts: How can we know what's the density of ice (water), but there's no data on how much is the density of frozen ethanol? (as far as I know)


texts: Can copper sulfate react with terpenes (such as limonene and terpinenes) at room temperature?

texts: I am just wondering, can I make a metalorganic or organometallic complex of copper and limonene/terpinene/phellandrene in the form of lime oil? If so, what is the formula of the complex formed? I tried the reaction with lime oil in iPrOH, and a copper sulfate solution. The result was a blue crystalline solid. What are the crystals? I'd like to know.


texts: Why is DNA negatively charged and what makes it so?

texts:
What part in the strand contributes to the overall non neutral charge?
DNA is not isolated in the body, so what keeps it stable while being charged?
Why is it important for DNA to be charged?


texts: What is going on when pen stops working on a section of paper?

texts:
Ever had a ballpoint pen that would all of a sudden hit a 'dead spot' on a sheet of paper and refuse to write? It's clearly not the pen, because when moved off to the corner it would draw perfect circles instantly. Move it back to the spot, and it stops working again. Usually I can get something blotchy if I write out the word a dozen or so times while pressing hard.  What's going on with the paper and ink here?

Some pages of my notebook are like this and it's very annoying. My best guess is that it got splashed and something about the paper changed, but my guess probably isn't a very good one since it doesn't have the signature crinkly waviness of wetted paper.


texts: Comparing Basic strengths of different species

texts:
I was doing questions on organic chemistry. I came across tonnes of questions  where I was required to compare basic and acidic strengths.

Comparing acidic strengths is fine — I remove an $\ce{H+}$ and compare the stability of the anion because my teacher told me a strong acid has a stable anion and explained the reason to me from an equilibrium point of view.

When it comes to comparing basic strengths what do we do?

Can I add an $\ce{H+}$ to the species and compare the resulting stability by resonance, hyperconjugation and inductive effect and then can conclude the more basic one will have a stabler cation?

Really baffled.
Please do correct me if I am mistaken in my fundamentals.


texts: Mechanism of a gold catalyzed addition to triple bond

texts:
I needed to draw the reaction mechanism for this reaction:

So, after consulting some literature I drew this mechanism:

But, I am not sure about the last step. Does the $\ce{H+}$ just substitute the $\ce{Au+}$ ion? If so, is my last step correct?
Or, something else happens in the last step?


texts:
This is a question from Atkin's Physical Chemistry Book.

Question

Suppose that 3mmol $\mathrm{N_2\,(g)}$ occupies $\mathrm{36~cm^3}$ at $\mathrm{300~K}$ and expands to $\mathrm{60~cm^3}$. Calculate $\Delta G$ for the process.

My Attempt

I decided to split this process up into two separate process (I am not sure if this allowed. Please correct me if this wrong). The first process is an reversible isothermal expansion of the gas to $\mathrm{60~cm^3}$. Then the second step is an adiabatic cooling of the gas. I was planning to calculate $\Delta G$ for each step then add them up to get the answer. For the first step, $\Delta U = 0$, therefore:
$$q = -w = n~R~T~\ln\frac{60}{36}$$
$$\Delta S = \frac{q}{T} = n~R~\ln\frac{60}{36}$$

Since pressure is constant, $$\Delta H = q = n~R~T~\ln\frac{60}{36}$$
Therefore: $$\Delta G = \Delta H - T\Delta S = 0$$
I stopped her because I am sure that this is incorrect as Gibbs Free Energy shouldn't be equal to $0$.

Can someone please clarify if the above procedure is correct and perhaps a better way to attempt this question?


texts: Meaning of the term "vertex" in the topic of skeletal formulae

texts:
From the Wikipedia article on skeletal formula:

  Hydrogen atoms attached to carbon are implied. An unlabeled vertex is understood to represent a carbon attached to the number of hydrogens required to satisfy the octet rule, while a vertex labeled with a formal charge and/or nonbonding electron(s) is understood to have the number of hydrogen atoms required to give the carbon atom these indicated properties. Optionally, acetylenic and formyl hydrogens can be shown explicitly for the sake of clarity.

This is the first use of the word "vertex" in the article. Is a vertex

only the intersection of two line segments, or
the end of each line segment?

I assume the latter is true, but on many places I saw cyclopentyl being represented like this:

which should be methylcyclopentane instead, a completely different thing.

So, it looks like (mostly when describing aryls or cycloalkyls) some people assume that "vertex" means only the intersection of two line segments, otherwise they would have added the $\ce{CH3}$ to the end of the line to indicate methylcyclopentane (in this case). It's certainly inconsistent, but is this justified in any system of structural formulae?


texts: I'm working with a zinc sheet in water + Nacl solution, I have adjusted the pH to 10 to develop a ZnO layer and prevent all the faradaic reactions (passivation state). I've removed the oxygen with a pump (I've added nitrogen too). In this system, what are the reactions that could appear? How can I prevent them?


texts: terminology for breakdown of liquid dielectric under the application of high voltage

texts:
I saw a diagram a while ago of increasing voltage (x-axis) and what seemed to be the chemical decompositions of ethylene glycol as it occurred at various applied voltages. (I am not a chemist- sorry about poor terminology) I want to find that diagram or something like it again, and I am failing.

I hoped to see intermediary products, final products, and intermediary reactions that occur when glycol was used as a dielectric in pulse power applications (we call the product of that breakdown "streamers," which is super general).

Any suggestions on how to word my search for something like that?

thanks for your help.


texts: Is there a difference between oxidation state and valency?

texts:
I just looked up peroxide on Google, and I saw that the oxidation state of oxygen in $\ce{R-O-O-R}$ is $–1$, and not $–2$ (like $\ce{H2O}$), when I could clearly see that each O atom forms two bonds. Did I get either of the concepts wrong?
I think that's probably the case but, can someone explain where I went wrong? To me, Valency dictates the no of bonds that an element can have. In the structure, I can clearly see that each oxygen forms $2$ bonds so, if I remove the other atoms, won't the imaginary charge left still be $-2$? Then how, does $-1$ come into play?


texts: Azeotropic Distillation - Am I interpreting this VLE diagram correctly?

texts:
I've been looking at ways to re-concentrate a formic acid-water binary mixture with the VLE diagram below.

Am I correct in saying that to concentrate a solution of say , 40% formic acid by weight I could (excluding all recycle streams for simplicity) implement a distillation column at 1 bar to produce a distillate at the azeotrope (78%) and then pass this distillate into a second column operating at 0.1 bar to distill further to 95%?

Aditionally, would operating the 1bar column for a distillate of say only 70% (past the 0.1 bar azeotrope) then performing the remaining concentration in the low pressure column result in any significant energy savings due to less steam required at the lower pressure?

Lastly, if I was to START with a solution of 85% formic acid, already beyond both azeotropes, I could just perform simple distillation in a single column at either pressure point to obtain the 95% product?


texts:
When do covalent bonds of a molecule $M$ extend or compress while no bonds in $M$ are broken? I can conceive of some possibilities but I don't know how common they are:

Temperature changes
Inter-molecular forces around $M$ which may stretch or compress $M$ in various directions
The transition from $M$ into a different conformation isomer (perhaps some stretching and twisting is required to overcome the energy barrier for a large change in conformation?)
Perhaps bonds can store energy like springs?

How likely are the above to happen, and are there other situations which induce bond deformation? Could I also have some references or topics to search on related topics? As far as I know, covalent bonds are relatively rigid and don't deform much.

Edit: one answer. Upon some literature review, it seems that rotation about $\sigma$-bonds and molecular inversion involve temporary bond deformations because the intermediate states (eclipsed conformations for the former, and the planar/linear form for the latter) involve a change in potential energy. After the transformation, the bond lengths revert to the original.


texts:
While attempting to make Schweizer's reagent in household conditions, using $\ce{CuSO4 + NaOH + 25\%  NH4OH}$ route (all at least 95% pure, either technical or lab grade purity), I've stumbled upon a problem. While trying to precipitate $\ce{Cu(OH)2}$, the temperature of the solutions rose to about 50 Celsius, and instead of expected blue precipitate, I got an almost black (with a hint of violet) one instead, which I assumed is $\ce{CuO}$. However, I was able to dissolve some of the precipitate in $\ce{NH4OH}$ slightly (a suspension was made from about 10 g of precipitate in 200 ml ammonia), resulting in dark blue solution with only traces of suspended black particles ($\ce{CuO}$?), appearing very like the expected Schweizer's reagent itself.

The resulting substance was able to dissolve regular cotton & cellulose samples overnight, however the dissolution was quite slow and unimpressive, with some of the sample material remaining almost intact; a chalk-coated paper was quite resistant to it (although it also dissolved somewhat eventually).

I don't have prior experience with Schweizer's reagent, so I don't know if the rate of dissolution I got here was the proper, expected behaviour here or a sign of dud.

Since, from what I know, $\ce{CuO}$ doesn't react nor dissolve in aq ammonia, does this experiment suggest a trace amounts of $\ce{Cu(OH)2}$ present in the (assumed) $\ce{CuO}$ precipitate, later forming a low-quality Schweizer's reagent, or am I missing something here?

As side questions:

was the precipitate really $\ce{CuO}$ (if so, how to avoid creating it, i.e. what are the necessary conditions for $\ce{Cu(OH)2}$ creation here), and what is the easiest way to check for $\ce{CuO}$ presence in general?
how efficient should be a properly done homemade Schweizer's reagent (using the aforementioned $\ce{CuSO4 + NaOH + 25\%  NH4OH}$ route) in dissolving various celluloses in practice?


texts: Producing methane, reactants and products

texts:
How do I balance this reaction when producing methane using the reactants:

$$\ce{CH3COONa(s) + NaOH(s) + Ca(OH)2 -> ?}$$

The products are partly

$\ce{CH4(g) + Na2CO3(s)}$

What else is missing in the products? Furthermore, how do I balance this?

Thanks in advance.


texts: Ionic Character, on which factors do it depend

texts:
I was watching a lecture of chemistry teacher. He gave the following question:

Q Arrange in terms of increasing ionic character: LiF,NaF,KF,RbF,CsF?

My try: I tried two approaches:
Approach 1: As F is common to all compounds, therefore its metal that affects the ionic character. As we move down the group as in this case, the shielding effect increases and hence it becomes more easier to abstract an electron from the outermost shell or in other words, Ionization energy decreases as we move down the group, therefore CsF>RbF>KF>NaF>LiF should be the order.

Approach 2: Li, Na, K, Rb, Cs have same electrovalency. As Cs has more larger size, the positive charge intensity on the atom decreases and thus by formula of electrostatic force F=-kq1q2/r^2, the electrostatic force of attraction decreases and thus lattice energy decreases and therefore order is:
LiF>NaF>KF>RbF>CsF.

According to me lattice energy should determine ionic character as lattice energy determines ionic bond strength I think and therefore approach 2 should be more legitimate but when I checked the answer, the answer by Approach 1 was correct. Why is it so? Which of the approach is right and which is wrong and why? Is there any other approach?


texts: Cheletropic carbene addition to ethene under Woodward-Hoffmann rules

texts:
Woodward and Hoffmann state in their seminal paper [1], that a ground-state pericyclic reaction is thermally allowed when $p+q=\textrm{odd}$, with $p=(4n)_{antara}$ and $q = (4m+2)_{supra}$. When I look at a cheletropic carbene addition to an ethene (see Figure, from [2]), this rule gets a bit shady for me.

Essentially, there are two ways to look at it:
1) The HOMO is the two-electron sp2 orbital on the carbene and the LUMO the the $\pi^*$ LUMO on the olefin.
2) The HOMO is the $\pi$ orbital on the olefin and the LUMO the pz orbital on the carbene.

Case 1) results in a $p=1$ from the sp2 and $q=1$ from the $\pi^*$, so $p+q=\textrm{even}$. The same can be verified for case 2). How can this be, since these kinds of insertion are usually thermally allowed? Even when I would add together both situations, I'd get an even number. Does the Woodward-Hoffmann system work here or am I missing something?

[1] http://onlinelibrary.wiley.com/doi/10.1002/anie.196907811/abstract
[2] http://chemistry.caltech.edu/courses/ch242/H1.pdf


texts: Parallel between polarisability of donor atom and CFS strength

texts:
Observing the strength of crystal field splitting by different ligands, can the following be considered?:

Most of the members in the series are ligands where the donor atom is nitrogen, oxygen or carbon.
If we consider only those can a parallel bases on the HSAB principle be drawn i.e. carbon which is softer and more polarisable than nitrogen generally is the donor atom in strong field ligands like CO or CN-. Similarly, it is followed by ligands having nitrogen, which is comparatively softer than oxygen but harder than carbon.
It may be argued that the halogens like iodine and bromine which are very soft are at the end but then they are down the group and also in different periods.
Although the series is dominated by C, N and O donor atoms, they are in the same period. Similarly, PPh3 where phosphorus is the donor atom is a stronger field ligand than the comparatively harder sulpur atom (in ligands like SCN- or S2-) in the same period.

Can such a parallel be drawn?


texts: Determining the orbitals that overlap to form a sigma bond

texts: In the chapter on molecular orbitals, my chemistry book mentions three types of sigma bonds: those formed by s-s ($\ce{H2}$), s-p ($\ce{HCl}$), p-p ($\ce{Cl2}$) hybrid-s ($\ce{CH4}$) and hybrid-hybrid ($\ce{C2H6}$) overlap. How is it possible to predict the type of atomic orbital overlap by which a specific σ bond is formed?


texts: What would happen if the volume changes in first order reactions?

texts:
I am searching for any piece of hints but couldn't find out anything

What would happen if the volume changes in first order reaction?
For example, suppose there is a first order reaction of ideal gases as below
\begin{align}\ce{A (g) &-> B (g) + C (g)}& v &=k[\ce{A}]\end{align}
Then we all know that
$$\frac{\mathrm{d}[\ce{A}]}{\mathrm{d}t} = k[\ce{A}]$$ and $t_{1/2}$ is constant if the volume is the same.

What if the reaction is happening in a cylinder which is not fixed?
I suggest that since this is a first order reaction, the proportion of molecules which proceeds in reaction is the same every time, and the extra volume change is independent of the happening reaction, so the concentration change would get more complex, but the change of the total number of molecules would be the same as the concentration change when volume is fixed.

I am not a professional in this field so I might be wrong. If wrong, in what point?


texts: Experimental Difference b/w Graphite Oxide & Graphene Oxide

texts:
I'm looking forward to making a graphene supercapacitor using LightScribe method for 12th Grade project. I need Graphite Oxide, to start working although all I can find on the web is Graphene Oxide.

I've read What is the difference between graphite oxide and graphene oxide?, but I don't seem to understand whether I can use it in my application or not.

The paper I'm referring to regarding the project is: Making Graphene-Based Supercapacitors by LightScribe, Theint-Aung, Cornell College, Department of Physics, Mount Vernon, IA

Questions

Q1. Can I use graphene oxide instead of graphite oxide to accomplish the end goal of producing graphene supercapacitors (production method could be different)?

Q2. Can I convert graphene oxide into graphite oxide, using some reaction?

Note: I have access to an "alright" quality chemistry lab at school (not US), so processes involving ultrasonic baths are out of question, I have access to only cheap equipment.

P.S.: If possible, could you also provide a link where I could learn a bit about the chemistry behind the reactions you are talking about in your answer?


texts: What is the most exothermic reaction with water?

texts: What substance reacting with water at room temperature and atmospheric pressure produces the most heat (per mole)? Does anything beat fluoroantimonic acid?


texts: Arsenic bound proteins confirmatory test

texts:
I want to confirm the presence of arsenic in some protein samples, apart from the marsh test can I use the following method?--

Arsenic is present as arsenic (III) ion in the samples. Hydrogen sulfide gas when passed in the sample of arsenic (III) ion gives precipitates which are yellow in color.

The yellow precipitates dissolve on adding concentrated nitric acid. This solution on reaction with ammonium molybdate in presence of concentrated nitric acid again gives yellow precipitate.

This confirms the presence of arsenic (III) ions in the sample.

If not, please suggest another method

P.S I have some info about arsenic bound proteins from-
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3797521/


texts: Any possible additives to a drain cleaner I use as a source of NaOH?

texts:
It is in pellets. And the box says main ingredient $\ce{NaOH}$ at least $30\%$ (I hope it's more). The box also says "aluminium catalyst". My goal was to take these pellets and dissolve them in water so that I would make a $1\textrm{M}$ solution of $\ce{NaOH}$.

I set everything up and most of it refused to dissolve in the solution. And the solubility for $\ce{NaOH}$ is pretty high. So I added some heat.This made almost everything slowly dissolve. Another thing was these small aluminium bits seemingly reacting and going up and down in the solution. I'm not sure if there was any gas released, but the solution definitely was not still.

I filtered it to remove the small aluminium balls. Any ideas If I have a relatively pure solution of $\ce{NaOH}$, or is it full of some other drain cleaner components. It is transparent-whiteish-little-yellowish. Filter kinda yellowish too.

What could these other components be?

Thanks


texts: What is the difference between an Adiabatic System and an Isolated System?

texts:
In my school text book there is a passage that says:

The presence of reactants in thermos flask or any other closed insulated vessel is an example of an isolated system.

Then a few passages of text later it says:

we take a system containing some quantity of water in a thermos flask or in an insulated beaker. This would not allow exchange of heat between the system and surrounding through its boundary and we call this type of system as adiabatic.

Does that mean all adiabatic systems can be called isolated systems and vice versa?
This got me confused. Please provide some clarity on this.


texts: Water becomes cold on mixing energy drink

texts:
I noticed that the temperature of water decreases noticeably when I mix an energy drink (Glucon-D) in it. The ingredients mentioned on the pack are majorly glucose (52%) and sucrose (45%). I believe that this is due to the inversion of sucrose being an endothermic reaction
$$\ce{C12H22O11 + H2O + \Delta -> \underset{glucose}{C6H12O6} + \underset{fructose}{C6H12O6}}$$
However, I could not find any sources on the internet to validate this. Please confirm/disprove this hypothesis and also explain the correct reason for this.

EDIT: After everyone's recommendations of sticking a thermometer in my drink, I did so and came up with the following observations:
\begin{array}{|c|c|c c|c|}
\hline
m_\text{drink} & V_\ce{H2O} & T_i & T_f & \Delta T\\
\hline
\pu{14.85 g} & \pu{200 ml} & \pu{20.3°C} & \pu{19.5 °C} & \pu{0.7 °C}\\
\hline
\end{array}

Some elementary thermochemistry gives me the result that $\Delta H_\text{solution}$ for the energy drink is $\approx \pu{39.6 J g-1}$.


texts: Molecular Hamiltonian of Helium hydride ion

texts:
Currently, I am going through Quantum Simulation of Helium Hydride Cation in a Solid-State Spin Register. I am not a chemist but rather a computer scientist hence having trouble following the paper.

I am using this easy to access note on Hartree-Fock  approximation.

So, I am not sure how the authors created the molecular Hamiltonian in Eq. 2 of the supplementary material.

$$
H = \begin{pmatrix}
-2.85404 & 0.130671 & 0.0 \\
0.130671 & -0.760916 & -0.323568\\
0.0 & -0.323568 & -1.91238
\end{pmatrix}
$$

From the note, I understand that the Born-Oppenheimer approximation (Eq. 3) is the starting point.

$$
H = -\sum^{N}_{i = 1} \frac{1}{2} \nabla^2_i - \sum^{N}_{i = 1} \sum^{M}_{A = 1} \frac{Z_A}{r_i A} + \sum^{N}_{i = 1} \sum^{N}_{j > 1} \frac{1}{r_{ij}}
$$

What should be my following steps to reach at the molecular Hamiltonian.

I am extremely sorry if I am asking for a really long answer.

UPDATE 1:
The molecular Hamiltonian is:

\begin{align}
\hat{H} &= \underbrace{-\frac{\hbar^2}{2 M_{He}} \nabla^2_{He} - \frac{\hbar^2}{2 M_H}}_{\text{Nuclear kinetic energy}} \underbrace{- \frac{\hbar^2}{2 m_e} \nabla_1^2 - \frac{\hbar^2}{2 m_e} \nabla^2_2}_{e^-\text{'s kinetic energy}}
\nonumber\\
& \underbrace{-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_1} - \overrightarrow{R_{He}}|}
-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_1} - \overrightarrow{R_{H}}|}}_{\text{Attractive potential energy between } 1\text{\textsuperscript{st} } e^- \text{ and nuclei}}
\nonumber\\
& \underbrace{-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_2} - \overrightarrow{R_{He}}|}
-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_2} - \overrightarrow{R_{H}}|}}_{\text{Attractive potential energy between } 2\text{\textsuperscript{nd} } e^- \text{ and nuclei}}
\nonumber\\
& \underbrace{+\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_1} - \overrightarrow{r_2}|}
 }_{e^-\text{ - }  e^- \text{ repulsion}}
 \underbrace{+\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{R_{He}} - \overrightarrow{R_H}|}
 }_{\text{Nuclear - Nuclear repulsion}}
\end{align}

After Born–Oppenheimer approximation:

\begin{align}
\hat{H} &=  \underbrace{- \frac{\hbar^2}{2 m_e} \nabla_1^2 - \frac{\hbar^2}{2 m_e} \nabla^2_2}_{e^-\text{'s kinetic energy}}
\nonumber\\
& \underbrace{-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_1} - \overrightarrow{R_{He}}|}
-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_1} - \overrightarrow{R_{H}}|}}_{\text{Attractive potential energy between } 1\text{\textsuperscript{st} } e^- \text{ and nuclei}}
\nonumber\\
& \underbrace{-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_2} - \overrightarrow{R_{He}}|}
-\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_2} - \overrightarrow{R_{H}}|}}_{\text{Attractive potential energy between } 2\text{\textsuperscript{nd} } e^- \text{ and nuclei}}
\nonumber\\
& \underbrace{+\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{r_1} - \overrightarrow{r_2}|}
 }_{e^-\text{ - }  e^- \text{ repulsion}}
 \underbrace{+\frac{1}{4 \pi \epsilon_0} \frac{2 e^2}{|\overrightarrow{R_{He}} - \overrightarrow{R_H}|}
 }_{\text{Now a constant since nuclei positions are fixed}}
\end{align}


texts: On the mechanism of the nitrogen-removal step of the Wharton olefin synthesis

texts:
In today’s reaction seminar, the Wharton transposition made an appearance. In our practice case it started from the epoxide as in scheme 1 below as on Wikipedia; Kürti/Czakó (page 482) begin from the enone which is oxidised by hydrogen peroxide to give the same epoxide.

Scheme 1: General mechanism of the Wharton olefin synthesis starting from an α,β-epoxy ketone to give the allylic alcohol.
The first steps are clear to me, I am interested in the mechanism of the final one. Our problem set’s solution key (taken from a Japanese book that I cannot reference for lack of understanding) draws a concerted [1,3] migration as depicted in scheme 2a. Kürti/Czakó depict a sequential release with an intermediate vinyl anion. Wikipedia makes no note on that step and does not discuss mechanistic proposals.

Scheme 2: Mechanisms given for the final step. (a) concerted pathway given by our problem set. (b) stepwise pathway given by Kürti/Czakó.
Kürti/Czakó also point out that:

Alternatively, the formation of a vinyl radical has been proposed.6
6: G. Stork, P. G. Willard, J. Am. Chem. Soc. 1977, 99, 7067–7068.

The concerted mechanism seems slightly unreasonable due to the strained four-membered ring that would be required in the transition state. Likewise, the stepwise mechanism requires the formation of a vinyl anion which — while possible — is generally not very stable. In its defence, the step would be rendered irreversible by the liberation of nitrogen gas and the subsequent anion immediately captured by any acidic proton around.
Which mechanism does the reaction most probably follow?

Reference:
L. Kürti and B. Czakó: Strategic Applications of Named Reactions in Organic Synthesis. Background and Detailed Mechanisms, Elsevier Academic Press, Burlington, MA, USA, 2005, page 482.


texts: How do pharmaceutical manufacturers ensure 100% purity in their medications?

texts: What purification measures are taken to ensure no side products are present in the medication? Because hardly any organic reaction is perfectly efficient, I'm guessing that multiple recrystallizations are performed. Also how would recrystallizations even be performed on an industrial scale? How much product is then lost and can it be recovered or is not economically advantageous to do so?


texts: Mechanism of acid-catalyzed addition of water across an alkene

texts:
My book tells me that when 1-propene reacts with water and sulfuric acid, I get 2-propanol. The proposed mechanism is that one of the electron pairs from the double bond of 1-propene travels to sulfuric acid, de-protonating it. At the next step, water comes in as a nucleophile and attacks the carbocation intermediate - the terminal carbon gets hydrogen added on it because its the carbon with the most hydrogens. We get CH3CH(H2O)CH3. Now water comes in as a nucleophile again and de-protonate a hydrogen to form 2-propanol.

Now when I asked someone on my ship who used to study organic chemistry at a university, she said that she remembered that it was one of the electron pairs from the double bond of 1-propene that travels to H3O+ instead.

Is either proposed mechanism acceptable?


texts: Calculating reaction enthalpy given other reactions

texts:
$$\begin{alignat}{2}\ce{X(s) + 1/2O2(g) &-> XO}&&\qquad\Delta H=-895.5\ \mathrm{kJ} \\
\ce{XCO3(s) &-> XO(s) + CO2(g)}&&\qquad\Delta H= +484.3\ \mathrm{kJ}\\
\ce{X(s) + 1/2O2(g) + CO2 &-> XCO3(s)}&&\qquad\Delta H = \;?\ \mathrm{kJ}
\end{alignat}$$

I wish to know how to do it. I have seen some questions where there's 3+ equations and at the end a final equation that I would need to determine the $\Delta H$ for the final equation. I have looked online on how to solve this but the tutorials are very confusing and I can't understand them. Can someone explain how to do this and other similar problems like this?

One of the tutorials talks about making sure they cancel out and flipping the equations? Can someone please explain this?


texts: Isotopes and their percentage existence in atmosphere

texts: When we talk about percentages of isotopes of an element in the atmosphere, is it percent by mass or volume or weight or something else?


texts: How to select for 1-4 carbon sugar bond in Chemical Glycosylation?

texts:
I am interested in Chemical Glycosylation, specifically the production of cellulose by synthetic means. However, it is difficult to ensure that the glycosidic bond is formed between the 1 and 4 carbons.

Are there any techniques that can select for this reaction?

I am looking for good references on this subject.


texts: This is the raman spectra of Toluene I obtained while working at my lab using a raman spectrometer with laser of 532 nm wavelength. Well, I am a physics student, but I want to know how information about vibrational modes and functional groups are inferred from the raman spectra, let's say from this spectra of Toluene. It would be of great help, since I am very curious about this spectroscopy method. I know physics part of raman spectroscopy, but really struggling with its application part.


texts: Why is hydrogen evolved at the copper side of a lemon battery?

texts:
I have 2 quick questions about the principle of a lemon battery.
What I understand is that:

Zinc is oxidized, freeing up electrons that travel through an external wire to the copper electrode (to which they are pulled)
Once the electrons reach the copper electrode, they react with $\ce{H+}$ ions in the lemon, resulting in $\ce{H2}$ (gas).

Since the zinc electrode that generates electrons is already immersed in the lemon (containing $\ce{H+}$), why wouldn't the electrons just react at the zinc electrode with $\ce{H+}$ ions in the lemon? Why would they have to travel to the copper electrode before doing so?

Once the electrons reach the copper electrode, why wouldn't they react with the $\ce{Cu^2+}$ ions that have been eventually formed at the copper electrode (even though I understand there wouldn't be a lot of them since Copper is not very reactive)?


texts: Are there any general rules for choosing solvents for recrystallization?

texts:
Re-crystallization is a nice way of purifying a product, but choosing a suitable solvent, if you can't rely on the literature, seems like a lot of trial-and-error.

Are there any general rules on which kind of solvents could be used for re-crystallization?
Which criteria should one use when trying to recrystallize a compound for which no literature on usable conditions are available?


texts: Does limonene react with calcium hydroxide or acetic acid?

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I can't find the results of too many experiments with Limonene. Which has many uses (e.g. making soap).

I'm curious of the results of combining Limonene and Calcium Hydroxide (Lime) in one experiment and another experiment combining Limonene and White Vinegar.

What is the result of these equations? Are the products potentially dangerous?

Could they result in combustion?

C10H16 + CH3COOH → ?

C10H16 + CaH2O2 → ?


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Rate of reaction is more when Carbon is more electrophile(less electron density)

So according to me the order should be D>B>C>A

As NO2 has -M -I effect , Cl has +M -I effect , while OCH3 has +M -I effect.

But the answer given as A>B>C>D


texts: What are the possible magnetic quantum numbers of silver?

texts: What are all the possible quantum numbers ml and ms of the electrons in the outermost s orbital of silver? I'm new to this concept. Can anyone walk me through this?


texts: I know soap molecules form micelles. Do they also form liposomes in water? I need the reasons too.


texts: The Acidity of the Hydrated Iron (III) Ion

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Why is $\ce{Fe(OH_2)_6^{3+}}$ fairly acidic? This iron has six water molecules coordinated to it.

In other words, water itself is a very weak acid. But when water is coordinated to iron, it becomes more acidic. I can think of a few reasons; can you think of more? Also are my reasons valid?

1) Induction. The negative charge generated through loss of the hydrogen proton is stabilized by the coordinated water molecules. Plus the center of the square planar molecule is greatly positively charged (and therefore can handle the negative charge, despite the fact that iron itself is actually electropositive rather than electronegative - at least in iron's ground state).

2) Size of the ferric ion. The ferric ion is rather big (it is, after all, able to coordinate six water molecules, as opposed to only four for some other metal ions). So whatever positive charge it has after being ionized once is spread out over a large surface area and that makes entire compound relatively stable.

3) Oxidation state of the central ferric ion - positive 3. This indicates a high degree of ionic character in the coordination bonds. Withdrawal of electron density from the water molecules makes the hydrogens even more positively charged and thus even more electrophilic.

4) Positive charge density of the central ferric atom. Coulomb's law is in (significant) effect here. Positive and positive. Like charges repel. Kicking off a hydrogen proton - no problem.


texts: How can the formation of an alkene be explained during the hydrolysis of an ester when the alkoxy moiety is tertiary?

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$$ \ce{RCOOR' + H2O -> RCOOH + R'OH} $$
But when $\ce{R'}=3^\circ$ it may result in the formation of alkene. But by the normal mechanism given in books and in various sites I am not able to explain its formation. I think that somewhere $\ce{R'^{+}}$ must be formed for alkene to be the product.


texts: Effect of concentration on voltage from the perspective of energy

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As I understand it, the voltage in an electrochemical cell is due to the electrons transferred having a decrease in electrical energy as they go from one species to another.
I assume that this change in potential is due to the electrostatic attractions and repulsions of the protons and other electrons of the species reacting with each other. However, I fail to see how the concentration of species would change the potential difference.
For example, I feel like the change in electric potential for an electron moving from $\ce{Zn}$ to $\ce{Cu^2+}$ in the reaction given below should not depend on the amounts of $\ce{Zn^2+}$ and $\ce{Cu^2+}$ present, just on the atomic level.
$$\ce{Zn(s) + Cu^2+(aq) -> Zn^2+(aq) + Cu(s)}$$
Could someone please explain why the voltage is not constant, from a conceptual standpoint? I considered that it may be that $\ce{Zn^2+}$ attracts electrons as well, but the solution remains electrically neutral due to the salt bridge, so I am not sure if that is the reason.


texts: What is the oxidation state of nitrogen in ammonium nitrate?

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The equation :
$\ce{NH4Cl + AgNO3 -> NH4NO3 + AgCl}$

I know that oxidation number of $\ce{N}$ in $\ce{NH4Cl}$ is -3 and in $\ce{AgNO3}$ is +5.
But what I am confused about, is the oxidation number of $\ce{N}$ in the product $\ce{NH4NO3}$. Should I consider $\ce{N}$ as $\ce{N2}$ in this compound or should I get its oxidation number in $\ce{NH4+}$ and in $\ce{NO3-}$ and then get the sum of them?


texts: Net ionic equation for a synthesis reaction?

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In the following reaction

$$\ce{S (s) + O2 (g) -> SO2 (g)}$$

there are no spectator ions because both $\ce{S}$ and $\ce{O2}$ take part in the reaction. Does that mean the net ionic equation is the same as the molecular equation?

I think there should not be a net ionic equation at all, because there are no ions in the reactants.


texts: Dimethylene Cyclohexane to Octalin-1,4-Dione | Hydroboration vs. Ozonolysis Pros Cons

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With regards to the following synthesis, what are some pros and cons of using hydroboration oxidation followed by oxidation of the alcohols compared to ozonolysis.

More specifically, how do the two compare as to yields of the final product, cost / amount of reagents, speed of reactions, unwanted side reactions?

Here is the synthesis, along with the two ways to prepare the cyclohexadione:


texts: what is a difference between outer electrons and unpaired electrons

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I know outer electrons include (n-1)d...+ all n'ss.. But i don't understand, never been told what unpaired electron is supposed to be? is it the same thing.

so in the following electron configuration:

$4s^2\: 3d^{10}\: 4p^3$:

OuterElectrons: $15$

ValenceElectrons: $5$

from what I remember someone told me unpaired electrons are $15$ too for this...which is the same as  outer electrons so I guess it's the same thing. But I am not sure so please help.