texts: Le Chatelier’s principle when pressure of gases increased with the same stoichiometric coefficient

texts:
$$\ce{C (s) + H2O (g) <=> CO2 (g) + H2 (g)}$$
What will happen to the equilibrium when the pressure of gases is increased? What will happen to the yield of $\ce{H2}$?

Since pressure increased means the volume is decreased, equilibrium will shift to the direction with the least number of moles. But since the stoichiometric coeffients are all the same, am I right to say that it will not shift?
But I doubt my answer as the question states - "pressure of gases increased". The reactants include solid carbon, meaning I do not count that in. Does this mean that equilibrium shifts to the right?


texts: Would decomposition take place in an atmosphere without oxygen?

texts:
Let's say you placed some sort of biological material (like raw chicken meat, an apple, etc.) in a very large glass container (large enough that moisture could evaporate at a similar rate to the normal atmosphere); filled it with a heavier-than-air, inert gas, like xenon; then, sealed the container and placed it outside.

Question: Would the biological material decompose?

My natural assumption is that it would decompose slightly, but mostly it would dry out and essentially become "mummified."


texts: Why is sulfur dioxide more stable to UV radiation than ozone?

texts:
Ozone readily decomposes when impacted by UV radiation.

Sulfur dioxide, having the same bond structure and valence electrons in each atom as ozone, is much more stable.

Would someone please help me understand what makes sulfur dioxide a more stable compound?


texts: When considering Van der Waals forces, why do dipoles form?

texts:
Imagine two atoms, and only consider the Van der Waals force. The electron cloud will jitter due to its quantum mechanical nature- some of these jitters forming dipoles, some not. However, on average they form dipoles. Why?
This question is equivalent to asking (although it is useful here to ask in another way): why is the potential energy of a dipole lower than a non-dipole?

What determines which electrons are going to move to the middle of the atoms to form a dipole, and which ones move to the outside of an atom (I assume that a dipole is formed like this $e^-..ion...........e^-..ion$ for the centre of positive charge shifted rightwards of the centre of negative charge): given that the jitters are instantaneous, and photons travel only at the speed of light, how are dipoles formed quickly enough before the next jitter?
Am I falling into a rut because I am not considering the wave nature of electrons?


texts: Electrophilic substitution in meta-nitrophenol

texts: Where will electrophilic substitution take place in meta-nitrophenol (3-nitrophenol) ? The two mesomeric effects seem to compete against each other.


texts:
What would be the effect if someone were to drink ultra-pure water with an electrical resistivity of $18 \, \mathrm{M} \Omega \! \cdot \! \text{cm}$?

Would they immediately die?  Would they just need to pee more?  Would $\ce{CO2}$ from the air (after the bottle is opened) and whatever's in saliva dissolve into the water making it much less pure before it gets into the important parts of their digestive tract?

What would be the threshold for bad things to happen — a teaspoon, a liter, 12 gallons in 10 minutes (at which point I assume regular water would kill you)?

I'm not sure what the science here would be.


texts: Calculation of silver nanoparticle size using Mie Theory

texts:
I have synthesized silver nano-particles and I wish to determine the approximate particle size using the wavelength that was most absorbed according to its absorption spectrum.

I find out that Mie theory provides a good approximation for this, (Eq 4 in this paper). However, I am clueless as to how to use the equation. In other words, how should I use the $\lambda_{max}$ obtained through the experiment in the provided equation?


texts: What is the state of the oxygen free radical in the following reaction?

texts:
$$\ce{O2(g) ->[h\nu][\nu\,<\,240~nm]2O^{.}(?)}$$

Oxygen is split by UV light below 240 nm to form oxygen radicals, which then go on to react with oxygen molecules to form ozone.

Firstly, is the oxygen a free radical?

Oxygen has six outer shell electrons, but my teacher mentioned that by the way orbitals work, they don't actually all pair off, rather you end up with two pairs of electrons and two unpaired electrons, hence making oxygen a free radical, though I'm not too sure. But because the free radical is so highly reactive, I'm not sure whether I'm even allowed to assign it a state, because straight after being formed it pretty much immediately reacts.

Going by process of elimination, it can't be aqueous, because it isn't dissolved in water, and I don't think it is solid, because solids are structurally rigid. I am therefore inclined to say that it is a gas, but my main problem is that each reaction only creates two oxygen free radicals, which immediately disappear, so it shouldn't actually show any properties of being a gas.

So what is the state I should assign the oxygen, or does it simply not need one?


texts: Ethyl Acetate and other Solvents in a mixture: miscibility and stability

texts: I was wondering about a heterogeneous solvent mixture containing multiple alcohols such as IPA, Ethanol, methanol etc.  Would EtOAc (Ethyl Acetate) play nice in these mixtures at low volumes such as 1 - 2 % of these mixture combos?  IPA +EtOAc, Eth+EtOAc, Meth+EtOac IPA+Eth+EtOAc, IPA+Eth+Meth+EtOAc. So EtAOc would be very low volume in each of these mixtures.  would it be miscible and fairly stable under normal conditions, ie, no acid, no heat, annhydrous etc.  Any problems that are seen with this?


texts: I am trying to make a highly scented jar candle. I'm having trouble wicking the candle when I put in larger amounts of fragrance oil. It seems to be either too small and drowns or is too large and smokes. Is there a way to add more scented oil to the wax blend. Or are there things I can add to my candle to help this.


texts: What happens to the methanol formed by the hydrolysis of methyl 2-hydroxybenzoate (oil of wintergreen) when synthesising salicylic acid?

texts:
Here are the reaction equations for reference (you may recognise this as a preliminary step for the synthesis of aspirin).

Steps for synthesis of salicylic acid:

1) methyl 2-hydroxybenzoate + sodium hydroxide -> sodium 2-hydroxybenzoate + methanol

2) sodium 2-hydroxybenzoate + hydrochloric acid -> salicylic acid + sodium chloride

Does the methanol play an underlying role in the reaction somewhere? Is the methanol filtered off? I do not know.

Thanks in advance.


texts: Effect of temperature change in an equilibrium reaction

texts:
Talking about an exothermic reaction in equilibrium it is said that heat is on the product side, so according to Le Chatelier principle, the reaction should move backward to counteract the increase in the number of products.
But it is also stated that in an exothermic reaction when the temperature increases, the value of equilibrium constant decreases, which means the product is less than reactant, then shouldn't the reaction move in the forward direction?
Please help me with wherever I'm going wrong.


texts: Is alkyne hydration possible without a catalyst?

texts: As the title says, is alkyne hydration possible without a catalyst at any temperature? i.e. will it ever occur within a reasonable amount of time? (excluding acetylene)


texts:
In my textbook it said that helium is used in oxygen tanks (diving apparatus) by deep sea divers.

When I searched the internet for the reason it said that :

  A mix of helium and oxygen is used in diving apparatus by deep sea divers, due to low solubility of helium in blood even at high pressure.

My doubts:

Why to mix helium when we can just fill the tanks with pure oxygen?
Why can't other inert gas be used in place of helium?


texts: What is the correct regular expression for InChI?

texts:
When I look for a regular expression for InChI, I succeed on EBI's MIRIAM Registery website:

^InChI\=1S?\/[A-Za-z0-9]+(\+[0-9]+)?(\/[cnpqbtmsih][A-Za-z0-9\-\+\(\)\,\/]+)*$

And indeed it works for some examples (using Python's re module):

import re

pattern = '^InChI\=1S?\/[A-Za-z0-9]+(\+[0-9]+)?(\/[cnpqbtmsih][A-Za-z0-9\-\+\(\)\,\/]+)*$'

s = 'InChI=1S/C2H6O/c1-2-3/h3H,2H2,1H3'

re.findall(pattern, s)

will print

[('', '/c1-2-3/h3H,2H2,1H3')]

However, if I take other examples, as e.g. this one

s2 = 'InChI=1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5+,6?/m1/s1'

it fails

re.findall(pattern, s2)

will return

[]

What is the correct and general regular expression for InChI?

EDIT

If I see this correctly, in the pattern from above, question marks are not taken into account which are used to mark both “unknown” and “undefined” chiral centres. If one adjusts the regex accordingly, it at least works for the example above; whether it then holds for all InChI is unclear, of course.

pattern = '^InChI\=1S?\/[A-Za-z0-9]+(\+[0-9]+)?(\/[cnpqbtmsih][A-Za-z0-9\-\+\(\)\,\/\?]+)*$'

s2 = 'InChI=1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5+,6?/m1/s1'

re.findall(pattern, s2)

will return

[('', '/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5+,6?/m1/s1')]


texts: Qualitative Comparisons of Dielectric Constants of Organic Solvents

texts:
This question is inspired by the discussion around this earlier question.
It is relatively simple to do a qualitative comparison of the polarities of different molecules (for example by analyzing the presence of polar bonds alongside the geometry of the molecule).
Now, ethanol and acetic acid have almost identical dipole moments ($\mu$=1.68 for acetic acid, $\mu$ = 1.69 for ethanol) but dramatically different dielectric constants ($\mathcal{E}$ = 6.15 for acetic acid, $\mathcal{E}$ = 24.5).
Is there a similar qualitative analysis that can be done for dielectric constant of a solvent?


texts: What chemical characteristics give types of steel their properties?

texts:
I am a mechanical engineer, and just like everyone else I had classes on the crystal structure of metals, phase diagrams, and the various heat treatments.

However, even after diving back into that recently and researching online, I can't make sense of how everything fits together. I know the high level, the low level, but can't link the two together.

For example:

How can the phase diagram of steel be linked to its physical properties? Say, given a certain carbon weight fraction, is it possible to tell from the phase diagram if the steel is going to be hard, resilient, ductile? E.g. cementite is hard and brittle, austenite is ductile and soft?
How do heat treatments work? The way I see it, the phase diagram is "steady state", and heat treatments are about spending a specific amount of time in a phase region to add "a little bit of that" etc. (or quickly cooling it to stop the reactions), but I can't link it back to the phase diagram (there is a 3rd dimension, time).

Apologies if this is not a very clear question, but this is exactly what I hope to find: clarification on a quite complex topic.


texts: Is ionic bond just formed by "electrostatic" interaction between two oppositely charged ions?

texts:
According to the definition of ionic bond:

  An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions.

If we consider the above figure showing formation of ionic bond, due to the transfer of electron from sodium atom to fluorine.It demonstrates clearly, how electrostatic interaction takes place.
In general, electrostatic interaction takes place between two stationary charges.Moreover, electrons would not be static as demonstrated by the above figure.Electrons will be moving at high speed, producing magnetic field around them, due to their motion; and even will also have electric field around them.Thus, we can expect electromagnetic interaction between oppositely charged ions along with electrostatic interaction due to stationary protons.So, does it mean that ionic bond is due to electromagnetic interaction and not just by electrostatic interaction?
[All the statements made are up to my view on the concept.Any correction advisory is welcome]

REFERENCES

http://en.wikipedia.org/wiki/Ionic_bond   (definition and diagram has been extracted from this link)
http://en.wikipedia.org/wiki/Electromagnetic_radiation (provides notion of charge motion effects)
http://en.wikipedia.org/wiki/Electrostatics (gives notion of electrostatic force)


texts: Does citric acid react with carbonated water?

texts:
I've noticed that when adding lemon juice to carbonated water, large 'soapy' bubbles appear on the surface. Since I'm adding another acid to a solution of carbonic acid, I would maybe expect a faster release of $\ce{CO2}$, but the bubbles I'm seeing do not resemble the usual fizzy drink bubbles.

What's going on?


texts: Why does hot oil fry things, but hot water does not?

texts: When a slice of potato is dropped into hot oil, it gets fried but the same in hot water, gets ‘cooked’. What is it about oil that gives the slice of potato the crispy feature while water only makes it soft?


texts: Freeze distillation: Does efficiency depend on solubility?

texts:
I was surprised to learn that freeze distillation has the same inefficiencies as vapor distillation: Namely, that it is impossible to get two miscible fluids to fully separate in one "pass" of subjecting the mix to a temperature between the melting point of its constituents.

I can understand why this is the case in vapor distillation, because vaporization of a liquid still occurs below its boiling point.

But AFAIK the same is not generally true of freezing: assuming it has a nucleus, a single liquid will either crystallize completely at a given temperature or it won't at all.

My guess is that the inefficiency of freeze distilling has something to do with the chemistry of miscible fluids: I.e., whatever phenomenon allows them to mix also drags molecules of the lower-melting chemical out of the mix above its melting point when the higher-melting chemical crystallizes.  If so then the efficiency of freeze distilling should have some relationship to a measurable quantity (like a miscibility coefficient?).  What theories and models of miscible fluids are applicable to the question of efficiency of freeze distillation?

(If there is no attraction between the two fluid chemicals then presumably "single-pass freeze distillation" could be perfect.  It would probably require agitation to help the more volatile of the two stay out of the crystals forming from the first chemical to freeze.  For example, agitation during freezing is how ice is formed without visible bubbles from dissolved gasses.  But if "there is no attraction" then presumably the fluid chemicals are not miscible, right?)


texts:
I'm currently in high school doing a project in chemistry. So I had to make a project where concepts from physical chemistry will be used alongside organic chemistry.
After going through my book I decided to create a test for carboxylic acids using electrochemistry. The basis of the test is:

Aldehydes, ketones and alcohols are non ionic in aqueous solution
while carboxylic acids are ionic. Therefore  carboxylic acid can be
used as an electrolyte.

So I finalized the following:
Lead, copper (my school doesn't have much chemicals and reagents and mostly available one was lead and copper so I stuck with it). The thing is, boiling the given organic compound with elemental lead, hydrogen peroxide and taking the precipitate obtained and measure the weight and dissolve it in test tube with water this acts as an electrolyte for lead half cell and make a copper half cell and connect the copper electrode and lead electrode with wires and put a suitable salt bridge. If there is reading in ammeter connected to the wires then the given organic compound contains carboxylic acid.
Is my method okay?
Edit:

1)since someone pointed out a lot of flaws ,  can I do like this:
Taking the aqueos solution of the organic compound as electrolyte and putting Zn,Cu electrodes in it and connecting the electrodes using a wire and connecting the wires to an ammeter ,(will this work like a lemon battery?)


texts: Reverse rate coefficient for thermolecular and thermal dissociation reactions

texts:
I am an astrophysicist working in exoplanetary atmosphere chemistry right now, in particular modelling the chemical kinetics taking place within the atmosphere. Based on this IOP article, we have that given a certain chemical reaction,

$\ce{\alpha A + \beta B <=> \gamma C + \eta D}$

In which its forward rate coefficient is $k_{\mathrm{f}}$ and the reverse counterpart is noted as $k_{\mathrm{r}}$ the equilibrium constant let us to compute the reverse reaction rate coefficient as

$$\frac{k_{\text{f}}}{k_{\mathrm{r}}} = K_{\text{eq}}\left(\frac{k_{\mathrm{b}}T}{P_{0}}\right)^{\Delta \mu}$$

$$K_\text{eq} = \exp\left(-\frac{\Delta H^{0}-T\Delta s^{0}}{RT}\right)$$

The previously cited paper is pretty clear at this statement and it is relatively easy to find this information to me in other sources. Nevertheless I came up with a certain kind of reactions, so called "Combination
and Dissociation Reactions" in which a third body is involved, in my case representing the atmospheric bulk, for example molecular hydrogen for a Jupiter-like planet and it is represented by a letter "M". For example we could have

$\ce{A + M ->  C +  D + M}$

For these kind of reactions the rate coefficient is parametrized based upon on to limiting to zero and infinite pressure, $k_{0}$, $k_{\inf}$ and an "F" coefficient leading to the equivalente rate coefficient

$$k = \frac{k_{0}M}{1+\frac{k_{0}M}{k_{\inf}}}F$$

My question is, is this kind of reactions reversible?. Can we reverse the reaction using the previous formalism just exchanging $k_\mathrm{f}$ by $k$?


texts: Is sodium percarbonate the safest and by weight the most efficient oxygen generator?

texts:
I have been reading about $\ce{Mn}$-catalyzed reaction of sodium percarbonate and water to produce gaseous oxygen in medical emergency situations.

This seems safe due to its reagents and products, however I am wondering if there are other reagents that would be suitable and safe enough to fulfill above use.

I did read about lithium perchlorate being used in so-called oxygen candles and capable of a high ratio of oxygen per weight output, however they hardly seem as safe as the above reaction.


texts: What is the difference between "bromine" and "bromine water" in their reaction with an alkene?

texts:
In question 16 of the A-Level Chemistry 2013 exam, there is this reaction scheme:

  $$\ce{CH3CH=CH2 ->[?] CH3-CHBr-CH2Br}$$

The question asks for both the name of the reagent and the product. I know that the product is 1,2-dibromopropane, but am confused about the reagent. I was told that the correct answer was "bromine", whereas "bromine water" was a wrong answer. Why is this so?


texts: Why caffeine is easily oxidized to uric acid?

texts:
I want to understand how caffeine (1,3,7-trimethylxanthine) can be easily oxidized to uric acid.

Is it safe to conclude that caffeine may increase the uric acid level in blood?


texts: Do catalysts increase the rate of exothermic reaction more in a reversible reaction?

texts:
I'm just learning chemistry for school and I've learnt that adding a catalyst reduces the activation energy for the forward and backward reaction by equal amounts, therefore the rate of forward and backward reaction increase by the same amounts so equilibrium stays the same but is reached more quickly.

I'm having some trouble understanding this. I know that the activation energy of the exothermic reaction is always smaller than that of the endothermic reaction. So thinking about the Maxwell Boltzmann distribution, a change in $E_a$ near to $0$ will have a greater effect on the rate of exothermic reaction than the endothermic reaction. Therefore, a catalyst should cause equilibrium to shift to the exothermic side?


texts: For molecules to be enantiomers, do the groups have to be non-superimposable mirror images even when rotated around C-C single bonds?

texts:
For example, if I rotate the Carbon-Carbon bond in B around 120 degree anti-clockwise, I would get the molecule shown in image C. C looks to me like a non-superimposable mirror image of A, hence A and C are enantiomers.

However, as drawn, A and B do NOT seem to be mirror images.

Are A and B enantiomers considering what happens after a bond rotation?

Note: ChemDoodle shows those red triangles saying "questionable stereochemistry". I'm not sure what is wrong but the molecules I drew may have some issues, but I think the question still holds.


texts: What happens if I make a hole in a container with superheated water?

texts:
Superheated water is achieved by heating water above 100 degree Celsius under high pressure.

Now, suppose the temperature at which the water is getting heated is around 250 Celsius and sufficient pressure is provided. If, I now make a small-hole in the container, the pressure will decrease obviously, but what will happen to the superheated water?

Will it come out in the form of vapor with lot of energy or some explosion might take place or just about something else?


texts: Mechanism for reaction between hydrochloric acid and magnesium

texts:
Balanced equation:

$$\ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)}$$

However, Cl- is a spectator ion so the actual reaction equation is:

$$\ce{Mg + 2H+ -> Mg^2+ + H2}$$

Here is my proposed reaction mechanism:

A magnesium atom reacts with a $\ce{H+}$ ion: $\ce{Mg + H+ -> Mg+ + H}$
The $\ce{Mg+}$ intermediate produced reacts with another $\ce{H+}$ ion: $\ce{Mg+ + H+ -> Mg^2+ + H}$
The two hydrogen atoms (from step 1 & 2) react together: $\ce{H + H -> H2}$

However, my problem arises when I compare this to my rate law that I found experimentally ($\ce{Mg}$ is not in the rate law as it is a solid and has no concentration):

$$\mathrm{rate} = k[\ce{H+}]^2$$

None of these mechanism steps above conform to my observed rate law (or do they?), could any of you enlighten me to any other mechanisms?

There are only two mechanisms I can think of: a one-step mechanism where it is literally $\ce{Mg + 2H+ -> Mg^2+ + H2}$ (though I've read that a one-step reaction is unlikely) and the other way is via an intermediate (as described above).


texts: How have I to understand in what those quantum numbers refer for ortho and para water?

texts:
I need to make an English presentation at my School (Graduate school) about something people may don't know. I chose to speak about the separation of ortho and para water. I first chat here with @Orthocresol about questions I have but this is really tricky and I'm not understanding that so much. So I chose to ask the question here, it might be helpful for other people and I hope at least for me.

At first my question is to understand what the notations $\lvert0_{00}0 \rangle$ and $\lvert1_{01}M \rangle$ in the article mention before about different states of water refers too?

What are those four numbers if the ket notation, from where they come from and what does they mean? I know it makes a lot of questions but maybe are they linked?

I read this article on wikipedia and this one too, and I also found that but I don't understood a lot of things. Maybe that $J$ is a quantum number which quantify the rotation energy of a molecule. But I have a lot of troubles with the projection and I don't know what $M$ is.

I would be glad if the answer was in a part like popularisation because I guess I'll have some troubles to understand it. But I have good skills in algebra, I had a twenty hours introduction in quantum chemistry, the hardest thing I did was a presentation of the spin-orbital coupling if it can help you to jugde my level on the subject. Thank you in advance for your answer.


texts: What would the pH change be if I drop one gram of sodium hydroxide into a pH 8.1 solution

texts: I have an experiment where I drop 1 gram of lab-concentration Sodium Hydroxide into a litre sea water (pH 8.1). What should be the expected change in pH? Would this change be constant? i.e if I was to drop 2 grams of NaOH into the sea water, would the change double?


texts: Electroplating with iron and copper acetate

texts:
Im trying to do cheep electroplating using iron and copper acetate as in introduction to electroplating and working with acids. Each solution was prepared using heated vinegar and hydrogen peroxide. I notice two things. First, my iron plating happens much slower than the copper plating. Is this because for my copper plating solution i used a vinegar with a 20% acid concentration and for the iron i used a 10%? Voltage is the same at 12V
My next question about about the gas coming off the cathode. Is it hydrogen gas? I was under the impression that my solution would never be depleted. As copper is plated onto an object it is removed from the copper anode and everything just keeps going. But if gas is bubbling up that means something is being consumed and will have be replaced. Is it that on the anode, oxygen is produced which then reacts with the copper and thats why I dont see any oxygen bubbling off?


texts: Why does it yield iron(II) chloride instead of iron when copper meets iron(III) chloride?

texts:
Complete the equation:
$$\ce{Cu + FeCl3 -> ? + ?}$$

I wrote $\ce{CuCl2}$ and $\ce{Fe}$, but it turned out to be $\ce{Cu}$ and $\ce{FeCl2}$. I really wonder why.


texts: Why do E2 reactions (dehydrohalogenation) only occur when the hydrogen and leaving group are in the same plane?

texts:
E2 reactions (dehydrohalogenation) only occur when the hydrogen and leaving group are in the same plane.

I can't think of a reason that they would need to be in the same plane, so what is the reason for this strange phenomenon?


texts: What does 'a' stand for in 'a-C' according to research paper lingo?

texts: I came across this paper but I cannot figure out what is a-C as it is not defined. The C here is obviously Carbon. Regarding 'a' prefix My best guess is that it stands for amorphous. Is this correct?


texts: Is it possible to estimate the abundance of conformers from J values?

texts:
I have a system of two disubstituted cyclohexanes and I want to estimate the abundance/ratio of the two based on the J values and if possible, roughly estimate the difference in free energy.

To get the extreme values of the J constants I have been provided with the data from the system on the image below.

This is all the information I have been provided with.
Is it possible to approximate the ratio and free energy difference and if so, how?


texts: How do I get the molarity of solution 1 given volume 1, molarity 2, and volume 2?

texts:
For example:

  What is the molarity of a $\ce{NaOH}$ solution if $25\rm~mL$ of the solution is exactly neutralized by $44\rm~mL$ of $0.32\rm~M~HCl$?

I know that the abstract function is

$$\text{Given Volume of Known Molarity} \times \text{Molarity Factor} \times \text{Mole Ratio} \times \text{Per Volume Factor} \times \text{Conversion Factor Per Liter}$$


texts: Nomenclature of Halogen substituted Alcohol and longest chain

texts: For the following compound, the correct IUPAC Name is "4-Chloro-3-ethyl-2-(1-methylethyl)-butan-1-ol" but according to what I know, Chlorine is a substitutent and alcohol is a functional group. So including alcohol is necessary but not $\ce{Cl}$. And if we see the longest chain including alcohol then it would be a pentanol rather than a butanol. Why are we not naming it like that? Is it because the substitute $\ce{Cl}$ is necessary to include? Or what?


texts: What reaction occurs when soaking a piece of meat in apple cider vinegar?

texts:
I would like to know what reaction occurs when  soaking a piece of meat in apple cider vinegar. Additionally, how does it happen?
I read a topic which was about the bad reputation of apple cider vinegar, which can actually "cook" your skin texture.


texts: What do you call the number of atoms in a molecule?

texts:
I just bought a molecular modeling kit for my toddler ("Snatoms").

To use the kit to play with her, I want to start out by memorizing a list of all molecules (isomers) fitting these criteria:

only contains C, H, and/or O
contains a maximum of 6 atoms

I started out by noodling around with Lewis diagrams and wikipedia... but then I ran into the various isomers of C2H2O2:

I wanted to do this search on a chemical database (like chemspider.com) but I couldn't find a criterion that would filter the search by number of atoms in the molecule (isomer).

Is there a name for this "number"?


texts: How does initial rate of reaction imply rate of reaction at any time?

texts:
My textbook begins the Chemical Kinetics section by describing the "Initial Rates Method" of determining the rate of reaction. I understood it as the following (for a first order reaction):
$$\ce{A -> B+C}$$
$$\text{rate}_\mathrm{i}=k[\ce{A}]_\mathrm{i}$$

The subscript $\text{i}$ shows that it is the initial rate. This I agree with, as it is suggested by experimental data. However, on the next page, the textbook makes a leap and (implicitly) states that this relationship holds at any time:
$$\text{rate}=-\frac{\mathrm{d}[\ce{A}]}{\mathrm{d}t}=k[\ce{A}]$$
This becomes a differential equation, the justification for which the textbook did not provide. How do we know that the change of concentration with respect to time depends on the concentration itself? I don't see how this can be assumed from the initial rates method.


texts: Equations for the oxidation reactions of tea teaflavins and EGCG with potassium permanganate

texts:
For my chemistry investigation, I used Stamm's potassium permanganate method to investigate tea tannins with potassium permanganate to find the tannin content of teas. The method assumes complete oxidation of tea polyphenols to carbon dioxide.

Assuming that the tea polyphenols consist of only theaflavins, $\ce{C29H24O12},$ and Epigallocatechin gallate (EGCG), $\ce{C22H18O11},$ could someone help me with finding the equation of the reaction between the listed polyphenols and potassium permanganate respectively, i.e. theaflavin reaction with potassium permamganate and EGCG reaction with potassium permanganate (preferably 2 equations for each redox, but 1 overall equation should be fine too)?

I tried looking for these everywhere, but no source seems to give me the equations I need.


texts: Viability of reduction of oil paint binder and solvent flammability upon disposal via addition of water

texts: As an artist, when disposing of a paper towel or cotton rag containing oil paint, turpentine, odorless turpentine substitute or mineral spirits at the end of a painting session, I generally pour water over the paper towel or cotton rag to reduce its flammability. Sometimes I rinse out the paper towel or rag in the sink before disposal to reduce concentration of the solvent. Does mixing water with the oil paint binder and solvent actually reduce its flammability? I understand mixtures can be categorized as suspension, colloidal or solution, and I would be curious to know whether or how this categorization pertains.


texts:
What is the chemical $\ce{CuCl.CO.2H2O},$ formed via the reaction of copper chloride and carbon monoxide?

Does this compound have any use or appear in any noteworthy reaction?


texts: Relationship between Enthalpy and Gibbs energy

texts:
I am a little stuck understanding the difference between Gibbs free energy and enthalpy. Both are measured in Joules and hence some sort of energy.
In a chemical reaction where C --> A + B
If A and B are more stable, this means energy will be released. This ΔPE is enthalpy(ΔH), correct? Enthalpy can be calculated from bond strengths after all.
In that case what does a reaction coordinate with Gibbs free energy tell us? ΔG is the change in free energy, but what is "free energy"?. Clearly that has to be different than the potential energy of the bonds since that is enthalpy (ΔH).
I appreciate any help!


texts: Effect of stirring and shaking on chemical kinetics

texts: Why don't we take the effects of stirring and shaking on the rates of chemical reactions? While studying chemical kinetics, I've seen that the rates depend on the concentrations of various species, temperature, pressure, etc. But I've never seen an equation taking into account the mechanical stirring, shaking and geometry of the beaker, presumably because these things are hard to experimentally measure and form a physical model which incorporates these things. For example, if the iodine clock reaction changes its rates due to stirring, every time I do the reaction, I shall get different times for colour changes. Then why do chemical kinetics equations make sense at all?


texts: Color of methoxy substituted phenyl rings when heated in the presence of acid

texts:
Anyone who's familiar with organic synthesis will probably have came across the DMB and PMB protecting groups.

When TLC-ing compounds containing these protecting groups using common stains like vanillin or cerium ammonium molybdate (CAM, the Hanessian stain), its not uncommon for the compounds to appear bright pink/purple. This is a useful phenomenon, but one which I have no explanation for.

I'd assumed that this was related to the stain itself, however even when the TLC plate is simply heated in methanolic hydrochloric acid, the pink color still appears (quite vividly in fact).

I realise that all of the stains mentioned are made up with some acid, however, heating PMB/DMB containing compounds under acidic conditions without the TLC plate (in a flask, for example), doesn't afford this colour.

Any insight into what's forming the color? Specifically when PMB/DMB compounds show it, but simple benzyl ethers etc do not.


texts: Is there a particular reason for the way these structures are represented?

texts: I know the question might seem a bit elementary but i was was curious whether there is a particular reason behind the way hydrogens are represented in a hydrocarbon chain. Is there a difference between representing them with straight lines or with slant lines as in the two images? Is one preferred over the other? If so under which conditions?


texts:
The modified Arrhenius equation is used to express the rate constant in a chemical mechanism model I'm working with. The equations is as follows:
$$k_\mathrm{f} = A\times T^b\times\exp\left(-\frac{E_\mathrm{a}}{RT}\right)$$
The paper states that "Units are Moles, cm3, Seconds, K, and Calories/Mole" so what would be the final units of the rate constant? I'm a bit confused due to the presence of the exponential function. When I simply plug the values in as given in the paper the rate becomes huge when multiplied by the molar concentration, is this because it gives molecules per second? To give you and idea for the following reaction:
$$\ce{C2H5OH + OH <=>C2H4OH + H2O}$$
The Arrhenius constants are as follows:
$$A = 1.74E+11$$
$$b = 0.27$$
$$E_a = 600.0$$
I am yet to calculate the reverse reaction using Gibbs Free Energy, is it just equally as large and thus it all cancels out or are the final units really not in $\mathrm{mol\ s^{-1}}$?


texts: Basification of acid solution. pH calculation. How?

texts:
This is my first post.

In order to understand basification I've created a pretty simple example as I currently understand it mainly because.. I really don't understand all of it.

Example:

Chemicals = Lye & Vinegar

Reaction  = NaOH + C2H4O2 = H2O + NaC2H3O2

Since the molar ratio of the equation is 1:1...

                Molar Mass          It takes...
Lye     NaOH    39.99710928  = 40   Grams of Lye to NEUTRALIZE,
Acetic  C2H402  60.05196     = 60   Grams of Acetic Acid.
                               *....a Weight Ratio of 2:3

Now to the part I don't understand...

1 liter = 1000 grams

At 5% standard acidity, a liter of vinegar has exactly

1000 Grams x 0.05 = 50   Grams of acetic acid in it.

Thus, at the above calculated Weight Ratio of 2:3...

50 Grams of acetic acid x 2/3 = 33.33   Grams of Lye to NEUTRALIZE,
                                50      Grams of Acetic Acid.
                                *....proportional Weight Ratio of 2:3

So far...

We have neutralized the 50 grams of acetic acid in the solution to pH7.

Question:

What would be the pH of the remainder 950ml of water in the bottle of vinegar? Is it the obvious? pH7?

Is my goal only to neutralize the acetic acid in the solution because the remainder is obviously just water and naturally at a of pH7?


texts:
First, $\ce{N2H4}$ is a base when it reacts with water, it accepts a proton.

$$\ce{N2H4 + H2O -> N2H5+ + OH-}$$

Can I follow up the reaction with this?

$$\ce{N2H5+ + H2O -> N2H6^{2+} + OH-}$$


texts: Why is the reason for color different in these two cases?

texts:
I have read in a book (NCERT India) about flame color for salts of alkali metal and color of transition metal complexes.

In the first case, it says that during excitation of electrons to higher energy it absorbs energy and then when it falls back it is emitted again giving color to the flame.

In the second case, it says that during d-d transition it absorbs a wavelength of photon and complementary color is shown. So, why can't there be emission in the second case like the first case.


texts: What white powdery compound turn black immediately after heating?

texts: What are some white compounds that look like powder (like flour) and immediately black after being heated? It turns immediately black and creates a odorous gas.


texts: How to you show a 3-center 2-electron bond in a Lewis structure?

texts:
How would you write $\ce{PCl5}$ or other hyper-conjugate molecules as a Lewis structure that indicates 3-center 2-electron bonds?

I have seen depictions [1] for transition metal complexes but not for main group non-metals such as sulfur or phosphorous.


texts:
I have the following system of reactions:
\begin{align}
M & \xrightarrow{\lambda(M,W)}M+M \\ W & \xrightarrow{\lambda(M,W)}W+W \\ M & \xrightarrow{\mu} \emptyset \\ W & \xrightarrow{\mu} \emptyset
\end{align}
Where $\emptyset$ encodes no species and $\lambda(W,M) = \mu+c(N-(W+\delta M))$ where $\mu , c , N > 0$ and $0 < \delta < 1$.
Both $\lambda(W,M)$ and $\mu$ are the rates per individual.

I come from a mathematical background and I am trying to apply the Law of Mass action to the above system. I am confused since in the right hand side the $M$ and $W$ appears twice. What are the rates of of $M$ and $W$ of the above system?


texts: How far-reaching is the effect of conjugation?

texts: Due to conjugation, it is possible for 1,4-addition, or conjugate addition, to occur. I was thinking, since conjugation and resonance effects do no diminish with distance, unlike inductive effects, does that mean that we can indefinitely conjugate and even have 1,6-addition? And even 1,8-addition and so on? My chemistry teacher mentions that 1,6-additions are possible but is there really no limit as to the effects of conjugations? Perhaps, there is increasing "resistance" as the carbon chain lengthens, like how a longer wire would have a larger resistance? I wonder if that would be an appropriate analogy.


texts:
A given mass of gas expands from state A to state B by three paths 1, 2, 3 as shown in the figure below.

If $W_1,$ $W_2$ and $W_3$ are respectively, be the work done by the gas along three paths, then
(A) $W_1 > W_2 > W_3$
(B) $W_1 < W_2 < W_3$
(C) $W_1 = W_2 = W_3$
(D) $W_1 < W_2 : W_1 < W_3$

The work done is $W = -P \,\mathrm dV$ that is the negative of the area under the graph; since Area 3 > Area 2 > Area 1, thus, $W_1 > W_2 > W_3.$
But the answer given is option (B). Why is this so?


texts:
If I heat up cracked glassware (wherein a crack has gone through part of the glass without any glass splitting away) will it cleanly refuse together before the whole piece loses its shape?
If so, would I just have to re-anneal it afterwards and that's it?


texts:
This question is inspired from a previous question(marked unclear). I don't know about the context of that question but I was intrigued by a statement in that question:

  Superphosphate is used instead of just phosphate because
  superphosphate is a compound whereas phosphate is an ion.

Now, the question is how the name "superphosphate" describe a compound? Since, it contains the suffix -ate, shouldn't it be considered an ion just like a phosphate?

Just to add some more context, I googled "superphosphate" and it gave results about it being a fertilizer, its various types and its suppliers. How come a fertilizer be named superphosphate? Is it because it is enrich in phosphorus? Or is it just a trademark name? What is the significance of the word "super"?

Searching for more, I came to know that calcium dihydrogenphosphate is also known as calcium superphosphate. Is it the same superphosphate that we are talking about? Is it the same as superoxide? Does IUPAC recommends its usage? To broaden the clarification, what is "super" even supposed to mean? Can we say in general that an acidic anion can be called super-anion?

If there are superoxide and superphosphate, are there any other ion containing the name "super" like supersulfate or supernitrate? The names seem to be too absurd/obsolete to even pronounce. Searching for "supernitrate" gave 2 results: alibaba and super calcium nitrate which is suppose to be nitrogenous ferilizers. Searching for "supersulfate" gave me results of a type of cement(One example here). So, I think that the name "super" isn't bound to ferilizers only.

To clarify my questions:

What is the significance of the name "super" in superphosphate? Is it a real chemical name or a trademark name?
Is the same as superoxide?
Are there any other ions containing the name "super"?


texts: Reaction of 2-ethyl-5-methyl-3-phenylfuran under acidic conditions

texts:
I was asked:

  Does protonation occur to the electronegative oxygen?
  What is the function of the heat?

I think that there will be protonation at C-3 which will break the aromaticity and the ring will open to form a diketone product.


texts: Experimental measurment of thiosulphuric acid decomposition kinetics

texts:
Problem

I am trying to do a kinetics analysis on the following reaction:

$$\ce{Na2S2O3 {(aq)} + 2 HCl {(aq)} -> S {(s)} + 2 NaCl {(aq)} + SO2 {(g)} + H2O {(l)}}$$

Suggested Method

However, most practicals online suggest I use an 'X' Mark and let the sulphur precipitate cloud the mark (Here's an Example) . To measure the rate of the reaction, I would begin timing as soon as I mixed the two solutions and end as soon as the 'X' was completely obscured.

Alternatives

However this form of time measurement is somewhat qualitative.

I considered looking at:

pH or temperature:       Those readings would not provide substantial data.
Change in volume or mass:   For the gas released, but $\ce{SO2_{(g)}}$ is dissolvable in water.
Conductance:         Although this is viable, I was told there is an alternative.
Colour (Spectrometry):    This probably won't work because the spectra observed and                  measured will suddenly reach its maximum as solids are                becoming present that have complete absorption.

I was told that the last option (colour or spectrometry) was "on the right direction".

Question

So, with all this in mind...

Are there any quantitative means of measuring the rate of the above reaction?


texts: Color of precipitate formed on reaction of acetylene with Tollen's Reagent

texts:
I am asked to find the color of the precipitate formed by the passage of acetylene gas into an aqueous solution of ammoniacal silver nitrate.

I thought ammoniacal silver nitrate was Tollen's reagent, but acetylene is neither a ketone nor an aldehyde so I don't know how to figure out the color of the precipitate.


texts: How to define custom force in quantum chemistry packages?

texts:
I don't know if this is really applicable but I want to add a custom force (say, $F(x,y,z)$) to some atoms in my geometry optimization. Is there any way to add such forces to the DFT or molecular mechanics calculations? (preferably GAMESS or Gaussian for QC or Avogadro for MM).

It can be also done as Molecular Mechanics (MM) as I just need an approximate geometry after applying the force.

Let me give an example. Say I have molecule A and molecule B and a force that changes in space as $F(x,y,z)$ but is only applied to molecule B. Now I want to calculate the new geometry of A and B.

I can think this is like adding a $V_F$ to the external energy in the Schrödinger equation, but I don't know how to do that in QC packages:

$$\left[-\frac{1}{2}∇^2 + V(r) +\color{red}{V_F(r)}\right]ψ(r) = Eψ(r)$$

Update:  The idea of making a unit cell and making shrinkage on it looks great (suggested by Geoff Hutchinson here), but the problem is I couldn't figure out how to install CP2K on MacOS and also I am looking for something with a simple interface like Avogadro. I even tried Maestro by Schrödinger software, but couldn't make unit cell shrinkage for that.


texts:
In an attempt to wrap my head around the basics of electrochemistry I'm working my way through Wesley R. Browne's 'Electrochemistry' primer.

With regards to the equilibrium potential of an electrochemical cell he states: "The equilibrium potential is defined as the potential at which the forward and reverse electron transfer rates are equal and the net current flow is zero. ... When the electrode potential is more positive or more negative than the equilibrium electrode potential, the forward and reverse rates are no longer equal and a net current will flow."

My understanding is that the only equilibrium potential possible for a two-electrode electrochemical cell is 0V, as anything above or below 0V will result in the electrons 'wanting' to go to one electrode or the other = a net current.

However, in a three-electrode setup (working electrode, reference electrode and counter electrode) the potential of the working electrode is stated relative to the reference electrode (eg, 'vs Ag/AgCl'). In this setup, would the equilibrium potential of the working electrode be 0V relative to the counter electrode (as it's the counter electrode with which the vast majority of electrons are exchanged) but therefore not 0V relative to the reference electrode and thus you would be correct in stating that the equilibrium potential for working electrode X is (for example) +0.21V vs an Ag/AgCl reference electrode?

Any and all help appreciated!


texts: What happens when you mix alum with soap?

texts: I was handling alum one day and accidentally I touched toilet soap after that. They reacted with each other and formed a rubberlike sticky substance (like dried glue on palm). I am curious what was the chemical reaction and the substance which was formed. I re-tried the same thing with detergent and got similar results.


texts: Why does a lowered dielectric constant cause RNA/DNA precipitation in ethanol precipitation?

texts:
For ethanol precipitations, as mentioned in https://en.wikipedia.org/wiki/Ethanol_precipitation, given that the attraction of water molecules to charged ions like phosphates is based on Coulombic attraction, shouldn't the water-phosphate attraction be increased in magnitude by the same ratio as that by which the phosphate-cation in increased in magnitude? I.e., should there not be a lack of increased "preference" for phosphate-salt cation ionic bonds (and thus precipitation) over water-phosphate hydrogen bonds (and thus polynucleic acid solvation) as a result of the increased permittivity to charge-charge interactions that ethanol brings over water?
An argument based on the relative higher amounts of cations and ethanol, and lower in water, would make sense in increasing the likelihood of a cation-phosphate bond over a water-phosphate hydrogen bond, but then any mention of the dielectric constant in explaining ethanol precipitation seems entirely superfluous.


texts: Reactions of Grignard Reagents with amides

texts:
Can Grignard reagents add to amides? It appears from the synthetic pathway shown below that there has been some form of nucleophilic substitution at the carbonyl group.

Source: 49th IChO Preparatory Problems, Task 29


texts: Handling EPR spin-probes, specifically how to dissolve 5-DSA?

texts:
I want to do some EPR tests with 5-DSA (or related spin probe) dissolved into different crude oils.

It had not sunk into me that $100 of 5-DSA was a tiny amount of a very sticky solid. It's proving hard to deploy in each test. Better would be if I could dissolve my 5-DSA into, say, known volume of toluene and then pipette a few mL of that toluene mixture into the oil sample.

But is toluene the right answer? I don't want to destroy the free radical. How do other researchers handle their spin-probes?


texts: Will isopropyl alcohol dissolve the coating/paint of a notebook?

texts:
The notebook is a Dell Inspiron 6400 and the coating/paint is the silver on the palmrest and back cover.

It says 99,4% on the container of the isopropyl alcohol.


texts: What does (heated) mean in a chemical equation?

texts:
I'm supposed to balance the following equation:
$$\text{Potassium chlorate (heated)} \rightarrow \text{Potassium chloride + Oxygen}$$
But I don't understand what is meant by the label "heated" in front of the first element. Do I ignore it, or am I supposed to add another element to the reactants of the equation?


texts: Is it possible for monobasic and dibasic potassium phosphate to complete break down into phosphates?

texts:
Here is the picture of monobasic potassium phosphate:

And here is the picture of dibasic potassium phosphate:

Is it possible for the phosphorous-containing anions to further break down into actual phosphates and floating protons?


texts: What would the following NGP reaction yield?

texts:
Question

Attempt
I believe that in first reaction there would be simple Sn2. In the second reaction there Should be NGP. Hence i think the products should be diastereomers. But answer is (A)they are enatiomers. How?. Please help.


texts: Why hot water is more effective than cold water in cleaning

texts:
Today while washing curtains, my mother dipped them in hot water(containing detergent) for an hour and then washed them.When i asked her that why she done that,her answer was simple(it will make the cleaning easier and effective). It seems to me that there is a scientific phenomena is lying behind it,but i don't know what it is.

The question i m asking is why hot water is more effective than cold water in cleaning (cloths,curtains,bedsheets etc).

I shall be thankful to have your answers.


texts: What is meant by excess energy in exothermic reaction?

texts:
I was reading this article on exothermic reactions online: Exothermic reactions

It states that "In exothermic reactions, the products have less enthalpy than the reactants, and as a result, an exothermic reaction is said to have a negative enthalpy of reaction. This means that the energy required to break the bonds in the reactants is less than the energy released when new bonds form in the products. Excess energy from the reaction is released as heat and light."

I'm just curious, is the excess energy from the bonds being formed, or is it because of the fact that products have more potential energy than the reactants, and because of law of convervation of energy, is released as heat energy?


texts:
If we took a bunch of DNA molecules and put them together what properties would it have?

I learned that long molecules tend to make a solid substance because they get tangled. A single DNA molecule is very very long so I guess it has to be solid as a substance. I also guess it would be resistant to pulling it apart. Is it true? Has anyone actually tried doing that?


texts: Why do you drop the charge in the crossover method?

texts: When I do the crossover method of crossing ions, my teacher always tells us to drop the charge, but won't tell us why. I was wondering if we add it back in later, and if not, why does it disappear?


texts: Why there is a huge difference between the basicity of urea and guanidine?

texts: The two molecules have very similar structures, but urea has a $\mathrm{p}K_\mathrm{b}$ of $13.9,$ while guanidine have a $\mathrm{p}K_\mathrm{b}$ of $0.4.$ If guanidine cation can be stabilized by resonance, then why can't urea cation do so?


texts: Best way of studying protonation in non-polar solutions with ~100ppm of water present using computational methods?

texts:
I am currently looking at the mechanism of the formation of storage deposits in jet fuel. Interestingly, the concentration of acids in the fuel correlates strongly with the total insolubles formed over testing periods. As such, several papers propose acid catalysed deposition processes occurring. However, since jet fuel is a non-polar solvent, with very little water present, this would be an extremely slow process. Alternative, acids could be taking part in an alternate mechanism leading to deposits.
Currently I am employing DFT methods in my work to explore the deposition process from a mechanistic perspective. I represent the bulk jet fuel solvent with an n-dodecane PCM solvent model. N-dodecane was chosen as it is the average chain length of jet fuel bulk alkanes. To explore the protonation in these solvents with small amounts of dissolved water, I have been explicitly adding water molecules around the conjugate bases/acids and looking at how successive water molecules affect the ΔfG (Gibbs energy of reaction). However, I am unsatisfied with this method. At current I have been placing the water molecules at what seems like the most stable configurations. In fact there could be several stable configurations, and putting on calculations one-by-one in various configurations seems cumbersome and unsystematic.
Is there a more statistical approach to this problem? Or, would stepping outside of computational chemistry and performing a study in the lab be the only way to tackle this?
Thanks.


texts: Why do non-polar covalent compounds dissolve in non-polar covalent compounds only?

texts:
My textbook says that electrovalent and polar covalent compounds dissolve in electrovalent compounds and polar covalent compounds but not in non-polar covalent compounds. I understand the reason for this. It is because the oppositely charged moeities of the two compounds attract each other and the compounds thus dissociate and ionize into ions thus resulting in dissolution.

Now, it also says that non-polar covalent compounds dissolve in non-polar covalent compounds but not in electrovalent and polar covalent compounds. I do not quite understand the reason behind this.

I would like to know what dissolution is at the molecular level and why non-polar covalent compounds dissolve in non-polar covalent compounds only?


texts: Does the term 'silver nitrate' express all of its constituent chemical elements?

texts:
My professor gave my class a set of practice questions for the mid-term. One of those questions asks for the molar mass of a number of chemicals, such as lithium bromide and silver nitrate. We haven't studied those chemicals, so there's little reason for the professor to expect us to have memorized the elements that constitute those chemicals. In the case of lithium bromide, the term informs us of its constitution. Whereas,'silver nitrate' informs us that the chemical $ \mathrm{AgNO_3}$, includes silver and nitrogen, but I don't see anything in the term that would inform the reader that the chemical includes $ \mathrm{O_3}$.

Is there anything in the term 'silver nitrate' that would inform a reader that the chemical includes $ \mathrm{O_3}$?

More generally, is there a set of rules that relates the chemical constituents of chemical substances to the linguistic constituents of the terms that designate them?


texts:
Question

On a periodic table it shows that Zn and Cd and Hg all have 0 electron affinity. Why is that?

What I've noticed

I've noticed that these three elements are the end of the D orbital and they are completely full, i think that it has to do something with that But i am not entirely sure

Part two of question

Why is electron affinity expressed in negative numbers?
Ex: Cs=-45.5kj/mol


texts: If a gas absorbs heat, then how can its temperature remain constant?

texts:
My book has this line:

  In an isothermal expansion, the gas absorbs heat and does work

But, if a gas absorbs heat, then how can its temperature remain constant? (as the process is isothermal)


texts: What is the difference between radioactive equilibrium and transient equilibrium?

texts:
Consider the following radioactive decay:
$\ce{A\rightarrow B\rightarrow C}$
In my textbook, it is written that radioactive equilibrium is when rate of formation of $\ce{B}$ is equal to rate of disappearence of $\ce{B}$.  In my textbook, it is also written that when the net formation of $\ce{B}$ is zero, we say that the system is in transient equilibrium i.e. $\frac{dB_{N}}{dt}=0$ where $B_{N}$ is the number of atoms of $\ce{B}$ at time $t$. Now, $\frac{dB_{N}}{dt}=0$ means that the rate of formation of $\ce{B}$ is equal to the rate of disappearance of
$\ce{B}$ which is exactly what radioactive equilibrium is. Then, what is the difference between radioactive equilibrium and transient equilibrium? Is there even any difference between them? Pleas explain. I am confused.


texts: When hydrochloric acid is added to a sample of copper why does it look pink at first then form a pale blue solution ?


texts: Is endpoint pH concentration dependent? Choosing an acid/base indicator

texts:
We use titrations to determine analyte concentrations with a standardized titrant and an acid/base indicator, BUT how do we choose the indicator? It is my understanding that indicators are supposed to be matched to the endpoint pH of your titration, but unless you already know the concentration of the analyte in solution, how do we determine the endpoint pH to match the indicator to? And if we already know the concentration of our analyte, doesn't that defeat the purpose of the titration in the first place?

I must be missing something...


texts:
I am looking into the subject of water repelling and have been led to the hydrophobic subject area. I have two questions regarding this subject.

Is there a hydrophobic gas ?
If a hydrophobic liquid is heated to a gas does it loose its water repellent qualities.

Thanks for the help guys


texts: How is the distance between m/z axis values in mass spectrums called?

texts: The output data of mass spectrometers is relative intensity (y axis) over m/z (x axis). How is the distance between m/z values on the x-axis called (in case of centroided data and profile/raw data respectively)?


texts: How can DI water inhibit peroxidase activity?

texts: I'm troubleshooting an IHC staining issue, and according to Thermo-Fischer's website, "Deionized water can sometimes contain peroxidase inhibitors that can significantly impair enzyme activity." What exactly could deionized water contain that would inhibit peroxidase?


texts: Does the Maxwell-Boltzmann distribution apply to gases only?

texts:
The Maxwell-Boltzmann distribution can be used to determine the fraction of particles with sufficient energy to react. I know that the curve applies to gaseous reactants and would like to know whether solids and/or liquids are also described by a similar distribution.

In other words, can I use a Maxwell-Boltzmann distribution to interpret reaction rates at the molecular level in liquids and/or solids?


texts:
Having looked at the various definitions of acids and bases and having refined my understanding of it after learning about the inadequacies of pKa and the novel use of the Hammett acidity function, I would like to ask if the bare proton is the strongest acid?

I would like to define "acid strength" not as the extent of dissociation but more simply as the ability to protonate other chemical species.

I have come to this conclusion after reading through a post on the explanation behind the strength of fluorantimonic acid, being that the bare proton is liberated and that the conjugate base is so well coordinated, allowing the charge to be spread out over a large structure, stabilising it to a great extent.

There is no doubt about the proton being the strongest acid in the Brønsted-Lowry sense. Similarly, in the Lewis sense, this should also be logical as what could possibly more electrophilic than a bare proton?


texts: vapour pressure above 2 separate beakers containing liquids which form ideal solution

texts: Suppose we have A moles of liquid 1 in one beaker and B moles of liquid 2 in the other. Beakers are placed together in a biger closed container. Both have different vapour pressure when isloated. Now both components can't have their individual vapour pressures as it would disrupt the equilibrium of the other. It turns out the compensated vapour pressure would be the same as both liquids paced in one beaker. Why so? Is liquid from one beaker moving to the other and making the concentration equal in both?


texts: Which pathway is better for robinson cycloaddition? 2-phenylacetaldehyde + 3-buten-2-one or 2-phenyl-2-propenal + acetone?

texts: So this was a question on my orgII exam yesterday. The target molecule is 4-phenyl-2-cyclohexenone. By retrosynthetic analysis there is only one possible aldol condensation reaction, but two possible michael addition reactions afterwards. My "guess" was that the best one is 2-phenyl-2-propenal + acetone because in the other case the negative charge is delocalized throughout the benzene ring reducing the nucleophilic character of the a-carbon and also activating the ring in which case EAS could take place with the ring acting as the "Michael Donor".


texts: Can powdered beta-tin be made from raising the temperature of alpha-tin?

texts:
When white tin ($\beta$-tin) is cooled to a temperature below $13.2\ \mathrm{^\circ C}$, it creates the allotrope of gray ($\alpha$-tin), a gray, amorphous powder.

My question is that once you have the powdered gray tin, doe just raising the temperature above the point of stability turn it back to white tin, but in a powdered form?

Is there a change in appearance of the gray powder when that happens, or is it mostly unnoticeable?

Does the conversion to gray tin change the melting point?


texts: The minima of minimum boiling azeotropes

texts:
This is a very basic doubt, so I'll be really brief about it. The discussion I raise is particularly about minimum boiling azeotropes but it's understood that whatever I ask is about the general corresponding points.
In a minimum boiling binary azeotrope phase diagram, particularly one with mole fraction on the x-axis and vapour pressure on the y axis, I understand that the composition of the azeotrope is found by taking the point of intersection of the graph representing vapour pressure as a function of the liquid composition, and the graph representing vapour pressure as a function of the vapour composition. My doubt if it is absolutely necessary within theoretical scope that that particular composition yields the minimum possible boiling point, (and hence maximum pressure) possible from either side of the phase diagram. (By which I mean vapour composition and liquid composition graphs.)


texts: Is there a physical explanation behind the derivation of spectroscopic term symbols?

texts:
In deriving the spectroscopic term symbols, one method seems common among several sources, the clearest presentation for me being located here, a derivation of the term symbols for a $d^2$ ion.

So, the execution of this method seems pretty straightforward. My confusion is in why it works. It currently seems rather arbitrary (a $L=4$ G term symbol subtracts a microstate from eg. $L=0$). Stumbling blocks for me are:

1. Some singlet microstates seem redundant

http://sli.mg/j4t7mg.png

If I look at, for example, the wiki diagram for LS coupling by vector addition, I would assume S = 0 and L is equal to 1 in both of the above microstates.

2. Some higher multiplicity states also seem redundant

From the same vector addition diagram above, these top row microstates should be equivalent to the bottom row microstate cross-diagonal from it. As far as I have understood, the spectral term takes the absolute value of L and does not distinguish between -L and +L (eg. L=1 and L=-1 both yield P term symbols), so $|-L-S|=|L+S|$.

Alternatively, I have also considered that maybe the absolute value is only taken on L and not S. In this case, $|-L|+S=|L|+S$. Then the microstates would not be equivalent cross-diagonally but instead horizontally (top row microstates equivalent to each other and bottom row microstates equivalent to each other).

3. Not all term symbols for the potential microstates are a solution.

 $\Rightarrow$ $^3D_3$, $^3D_2$, $^3D_1$ microstates vanish in the derivation

After the method was so thorough in including all the potential microstates, some of these microstates turn out to be nonexistent or physically not relevant.

I am interested to know roughly why this method for the derivation of term symbols is physically logical (why it works), more specifically why the above states are not redundant, and most especially why certain spectroscopic terms / electron microstates are not relevant. I'm afraid the question may be too open ended, so if I can clarify any further, or there's a concise reference, please let me know.

Thank you for your time!


texts: Regular decrease in the atomic radius of 3d series

texts:
While comparing atomic radius, two factors are important:

A. Decrease in size due to increase in effective nuclear charge

B. Increase in size due to increase in shielding effect

I was surprised to find a regular decrease in the atomic radius of 3d series elements on this site because that would mean that effective nuclear charge is dominating in case of each element more than shielding factor.

http://crystalmaker.com/support/tutorials/crystalmaker/atomic-radii/index.html

I have also attached the screenshot of the values of atomic radii of 3d series elements(given in Angstrom).

On some previous stackexchange posts like this one

Variation in atomic sizes in the transition elements

I have found that from Ni to Zn there is a regular increase in size.

Are the values shown on this site wrong?
If yes, can you please provide the correct values.
 If not, can you please explain why shielding wouldn't be as effective as increase in nuclear charge?


texts: Comparison of acidity between angelic and tiglic acid

texts:
Which among angelic acid and tiglic acid (cis and trans isomers of 2-methylbut-2-enoic acid respectively) more acidic and why?

It is given in a book(A guidebook to mechanism in organic chemistry for the JEE by Peter Sykes and B. H. Kishan 6ed. p.3.29 Q.1)that the cis(Z-) form is more acidic but I think the trans(E-) form will be more acidic due to interaction of oxygen in conjugate base with hydrogen on C3


texts:
The reaction is:$$NH_3+CH_3OCH_3 \rightarrow CH_3NH_2+CH_3OH$$
The mechanism here would be $S_N2$ and since $NH_3$ is a stronger base so it should be a better nucleophile. Why then is this reaction not feasible?

Any help would be appreciated.


texts:
Explosives like picric acid and trinitrotoluene are unstable due to the close packing of so many $\ce{-NO2}$ groups onto a benzene ring. These highly strained bonds require only a relatively small amount of energy to cause the molecule to rip itself apart, forming a lot of more stable gas molecules, and releasing a lot of heat in the process.

My question is: is it thermodynamically feasible to have a reaction that rapidly evolves a lot of gas without being extremely exothermic? Would this still be considered an explosion?

It doesn't seem to me that this could be possible, but I never cease to be amazed at how little I know about chemistry. If it is feasible, and the gas molecules are more stable, then where does the energy go? If the gas molecules aren't more stable, then what's the driving force?


texts: Which one is the stronger Lewis base: diethyl ether or tetrahydrofuran?

texts:
I am trying to understand Lewis bases (bear with me, I am a physicist). I was asking myself how diethyl ether and tetrahydrofuran compare with respect to their properties as solvents in electrophilic additions. Or if there is any difference at all.

So, for example, is it better to use a (boron trifluoride + diethyl ether) complex or a (boron trifluoride + tetrahydrofuran) complex? As to my understanding this is mainly a question about how strong the solvent acts as a Lewis base. If the solvent (ether or THF) is a stronger base, it might inhibit the catalysis of the actual electrophilic addtion reaction we are targeting, right? So under this assumption it is probably better to use the weaker base.

My guess is that diethyl ether is the stronger Lewis base. It has two hydrogen atoms more, so it is also contributing two more electrons, and moreover due to the slightly lower electronegativity of hydrogen, these electrons tend to be dragged towards the oxygen. On the other hand, THF misses the two protons and electrons, and moreover it must be electroneutral in the symmetry plane where the opposite C-C bond is, so it contributes a little less electron stuff to the nucleophilic oxygen.

Is this argumentation correct?

And what about this: the THF molecule is a little more compact than the diethyl ether and moreover has a tensed 5-ring. So shouldn't this push the electrons a little more to the periphery of the molecule, especially to the oxygen, and thereby increase its strength as a Lewis base again? Is this effect relevant at all?

PS: After writing this question I found a table at Wikipedia (https://en.wikipedia.org/wiki/Lewis_acids_and_bases) which states that the enthalpy of formation of the BF3 adducts is

Et2O: 78.8 kJ/mol
THF: 90.4 kJ/mol

This is about the opposite of what I would have expected and seems to indicate that the effect of the two additional protons/electrons of Et2O is not as big as it might seem at first.

But is it really support for the "compactness of THF in the 5-ring" theory? Or are there other effects responsible for THF being the stronger Lewis base?


texts: What should the Rehm-Weller equation look like?

texts:
The Rehm-Weller equation, which defines the energy change for photoinduced electron transfer according to Lakowicz "Principles of Fluorescence Spectroscopy" [1, p. 337] should look like:
$$\Delta G=E^\mathrm{red}(D^+/D)-E^\mathrm{red}(A/A^-)-\Delta G_{00} - \frac{e^2}{\epsilon d} \tag{1}$$
So you can see the first two components are reduction potentials of donor $D^+$ and acceptor $A$. But sometimes you can find another definition:
$$\Delta G=E^\mathrm{ox}(D/D^+)-E^\mathrm{red}(A/A^-)-\Delta G_{00} - \dfrac{e^2}{\epsilon d} \tag{2}$$
Which one is correct? I'm totally confused.
References

Lakowicz, J. R. Principles of Fluorescence Spectroscopy, 3rd ed.; Springer: New York, 2006. ISBN 978-0-387-31278-1.


texts:
My textbook (NCERT Chemistry. Part I. Textbook for Class XI [1, p. 106]) states that

  Resonance stabilizes the molecule as the energy of the resonance hybrid is less than the energy of any single canonical structure

by giving two examples: $\ce{O3}$ and $\ce{CO2}.$

While I can see that clearly in case of $\ce{O3}$ molecule, I can't see that how resonance lead to lowering of energy as in case of $\ce{CO2}$ as two of its canonical structures have formal charge separation, while the one without formal charge separation seems to be more stable than the other two and hence the overall resonance hybrid.

It looks to me that the structure of $\ce{CO2}$ without formal charge separation is the correct one but spectroscopic data suggests that it has to be a resonance hybrid.

What am I missing?

References

Ashok Srivastava; Kalyan Banerjee; Gautam Ganguly; Naresh Yadav; Mathew John; Rajender Chauhan. Chemistry. Part I. Textbook for Class XI; NCERT: New Delhi, 2006. ISBN 81-7450-494-X.


texts: Why do some reactions need to be maintained at a particular temperature for prolonged periods of time?

texts: Some reactions require that temperatures of 70–100 °C to be maintained for periods of time as long as 24 hours. Why is this so?


texts: how is there no centre of symmetry in this case?

texts:
the question was whether the following compounds have the center of symmetry or not .the question was :

And the answer is that there is no center of symmetry .how? according to me, there should be the centre of symmetry. I have made it like this:

on asking my teacher how there is no center of symmetry he told me that since it is a Fischer projection, therefore, the horizontal lines are above the planes. therefore there will be no center of symmetry. I understand that if the horizontal lines are out of the plane then there will be no COS. but what I don't understand how come the horizontal lines are above the plane/out of the plane. please explain.


texts: What meaning do multiple real solutions of a truncated virial equation have, if any?

texts:
Let's say I truncate the virial equation after the third term for use as my equation of state:

$${P\over\rho RT}=1+B\rho+C\rho^2$$

I have tabulated values for $B(T)$ and $C(T)$.  I know $P$ and $T$ and want to solve for $\rho$.  The equation is cubic in $\rho$ meaning I could potentially have three real solutions.  I suspect that since the virial equation is intended to calculate the densities of vapors or supercritical gasses at relatively low pressures, that the lowest real root is the "real world" value.  Is this correct?  Do the other real values, if they exist, have any meaning?  Can this be generalized to higher order virial expansions?


texts: In my corrosion testing, I am to use the galvanic corrosion testing by ASTM G71. But due to limited knowledge about this field, I can't understand fully the procedures needed to conduct the test in a laboratory scale. What is the simplest explanation of the ASTM G71 procedures that can be done in a laboratory?


texts: what is cyclopropane's reaction with lithium aluminium hydride? I think it must lead to ring-opening but I didn't find any article favoring this in my texts.


texts:
Why are there different values for enthalpy of combustion, depending on the calculation method?
Take for example the combustion of ethanol:
$$\ce{C2H5OH(l) + 3O2(g) -> 2CO2(g) + 3H2O (l)}$$

If I calculate this using enthalpy of formation:

\begin{array}{c|c}
\text{Substance} & \Delta H^\circ /\pu{(kJ/mol)}  \\
\hline
\ce{H2O(l)}    & -285.8 \\
\ce{CO2(g)}    & -393.5 \\
\ce{C2H5OH(l)} & -277.0
\end{array}

\begin{align}
  \Delta H &=
    \left[2\cdot(\pu{-393.5 kJ/mol}) + 3\cdot(\pu{-285.8 kJ/mol})\right]
    -\left[\pu{-277.0 kJ/mol} +  3\cdot(\pu{0 kJ/mol})\right]\\
  &= \pu{-1367.4 kJ/mol}
\end{align}

If I calculate this using bond energy:

\begin{array}{c|c}
\text{Bonds} & \Delta H^\circ /\pu{(kJ/mol)}  \\
\hline
\ce{C-C}      &  347 \\
\ce{C-H}      &  414 \\
\ce{O-H}      &  464 \\
\ce{C-O}      &  351 \\
\ce{C=O(CO2)} &  803 \\
\ce{O=O}      &  498
\end{array}

\begin{align}
  \Delta H &=
    \pu{347 kJ/mol} + \pu{351kJ/mol} + \pu{464 kJ/mol}
    + 5\cdot(\pu{414 kJ/mol}) \\
  &\quad
    + 3\cdot(\pu{498 kJ/mol})
    + 4\cdot(\pu{-803 kJ/mol}) + 6\cdot(\pu{-464 kJ/mol})\\
  &= \pu{-1270 kJ/mol}
\end{align}

Why is there such a big difference between them?


texts: What makes heat resistant proteins heat resistant?

texts:
We were doing the chapter Biomolecules in class the other day, and a doubt popped up once we reached the section on proteins.

We were taught that the stuff that keeps proteins together are: Ionic bonds (not always), Covalent bonds (peptide bonds and di-sulfide bridges), van der Waals' forces and hydrophobic interactions.

Now I've heard that certain bacteria are known to survive extremely hot conditions (Inside thermal vents, volcanoes, the like), like Thermus aquaticus, the source of taq polymerase. I'm told they're able to survive in those conditions because their proteins (enzymes and other cell components) show a very high level of thermal tolerance.

I tried reading up more on that, but Wikipedia adopts a very vague, generalized approach to the topic and doesn't specifically mention what imparts this high degree of stability to these proteins. https://en.wikipedia.org/wiki/Thermus_aquaticus

Frankly, if the earlier stated interactions are the only interactions seen in proteins, I don't see how some proteins can possess such high resilience to heat, especially since most of those interactions are fairly weak (and ionic interactions aren't very common).

Sure, maybe an incredibly extensive network of those interactions (say, hydrogen-bonding) would impart a good deal of stability, but I suppose such a protein would be incredibly compact, and twisted in all sorts of wacky shapes to generate the required stability.

I even tried comparing the structures of taq polymerase (First image; which denatures at about $100\ \mathrm{^\circ C}$) and salivary amylase (Second image; which denatures at a little under $40\ \mathrm{^\circ C}$), but to my (untrained) eye, there doesn't seem to be some absolutely fantastic and unique character to taq polymerase going by the structure that is:

So what exactly is it that imparts such high thermal stability to some proteins? Is it just a vastly intricate network of the earlier mentioned interactions, or is it because of something else?


texts: What's the actual difference between Formality and Molarity?

texts:
Today, I came across a question: "State the differences, in not less than 5 points, between Formality and Molarity".

Using my knowledge, I wrote down 2 points, and stretched it to 3 somehow, but that's all I could do... Also, in the process, I got confused between the two, because in pH calculations, even when Ionic solids and acids are dissolved in water, their concentration is expressed in terms of molarity, and not formality.

Please note that I am not asking this for the sake of my homework, but am asking for a better scientific knowledge of Formality, and how it differs from Molarity.

Here are the 3 points I wrote:

Molarity is the concentration of a molecular substance, expressed in terms of the ratio of moles of substance present to the volume of the solution it forms. Formality, on the other hand, is the concentration of an Ionic substance, that exists in the form of an Ionic Crystal Lattice, in terms of the ratio the gram formal masses present to the volume of the solution it forms.
Molarity is defined for molecular substances, whereas Formality is defined for Ionic substances.
The unit of molarity is $\pu{mol m-3}$, while that of formality is $\mathrm{form}~\pu{m-3}$ (where $\mathrm{form}$ is the number of gram formula mass units).

Can someone please explain the actual differences, and help with expanding the answer for more accuracy?


texts: Quantitative expression for steric hindrance

texts: Steric hinderance is a major component in determining the feasibility and the rate of a chemical reaction. Wouldn't it be useful to measure it quantitatively then? This would make it easier to compare the property of two molecules. Are there currently ways to measure steric hindrance, or is it not possible for some reason?


texts: Do two Miller planes need to have similar arrangement of atoms?

texts:
For two Miller planes, do I need to have the same arrangement of atoms in both of them?

Does it need to look like the same plane translated a little?

I have this question because if this is not the case, then how do you do the calculations for interference, etc, using Bragg's law, where we assume the atom of the bottom plane is directly below the atom of the top plane?


texts:
In my textbook it says, that a composed substance is a substance made of more than 1 type of atom. And It also says, in another chapter it says that a mixture is the grouping of more than one substance without any chemical reaction.

What is the difference between a mixture and a composed substance?


texts: Quantitative relationship between corrosiveness of acid and other properties

texts:
Is the corrosive nature of acid relative to some substance quantifiable like acid dissociation constant ($K_\mathrm{a}$)? If yes, what can be used to describe the corrosive nature of an acid?

For example, it is known that citric acid is far less corrosive than, say, sulfuric acid. But, can it be quantified? Also, if corrosiveness can be quantified, then can the caustic nature of bases be quantified too?


texts: Platinum vs Silver as Electrode for carbonic acid electrolyte

texts: Is silver a better cathode electrode with carbonic acid in a galvanic cell or is a platinum electrode better with carbonic acid ? The anode electrode is copper with copper sulfate electrolyte, and the salt bridge is sodium chloride.


texts: Sodalime method for multiple functional groups

texts:
what exactly happens? I get a little confused when it comes to multi functional groups. can some one explain soda lime as simple as they can.
I apologize if its a really simple question but I'm a high school student.
some good weblinks would be very helpful.


texts: Nomenclature confusion regarding carboxylate and ester

texts: I suddenly thought about these 2 compounds that seem to have the same name. Aren't both of them methyl propanoate? How do we differentiate them apart name wise?


texts:
Electron affinity of chlorine = -349 kJ per mole. And, first ionization energy of sodium = 496 kJ per mole while energy required for combining= 147 kJ per mole.

Isn't it a contradiction against genereal physics and G.N. Lewis' "electronic theory of valency"?


texts: what is the issue in evaluating two electron integral?

texts: What sort of issue is there in two electron integral in quantum chemistry ? Is it a problem of convergence when we do numerically? Can someone suggest any review article or reference articles which has the numerical algorithm to evaluate and to understand it fully ?


texts:
Is nickel tetracarbonyl a square planar complex or a tetrahedral complex?

According to the crystal field theory, $\ce{CO}$ is a strong field ligand and should hence cause the $t_{2g}$ electrons of nickel to pair up, hence leaving 1 $d$ orbital free, which must pair up with empty $s$ and $2p$ orbitals forming 4 $dsp_2$ orbitals yielding a square planar complex. But my textbook says its tetrahedral, with the electrons not pairing up and the outer d orbitals being used.


texts: What effect does an increase in concentration of copper sulphate solution have on the rate at which copper is deposited at the cathode?

texts: I have been studying electrolysis in school and was wondering whether a higher amount of copper sulfate solution would produce a greater mass of copper in an electrolytic cell with two copper electrodes in a given amount of time or not.


texts: Confusion on the Finkelstein reaction(AKA halogen exhange reaction)

texts:
So in the Finkelstein reaction, the iodide ion is supposed to replace another halogen(say chlorine) through SN2 mechanism.
But here, Acetone is used, which is a polar aprotic solvent. And in acetone, iodide ion is the weakest nucleophile. So how can it replace the chlorine?
Aren't we better off if we use water or ethanol(which are polar protic solvents) since (I-)
acts as the strongest nucleophile?


texts: Why doesn't the N-Br bond dissociate quickly in NBS?

texts: NBS is used to provide a constant, small amount of $\ce{Br2}$ which then dissociates to give $\ce{Br^.}$ free radical. Why doesn't the $\ce{N-Br}$ bond simply dissociate to give $\ce{Br}$? This dissociation should be just as fast or faster because the free radical formed would be stabilized by delocalization over the two oxygen atoms.


texts: Product of intramolecular aldol condensation of 3-methyloctane-2,7-dione

texts:
What is the major product formed when 3-methyloctane-2,7-dione is treated with sodium hydroxide?

My main issue is where the base deprotonates. Two enolates are possible (I neglected the other two because upon cyclisation, they form seven-membered rings which are less stable than the five-membered rings otherwise formed). Enolate 2 should be more stable than enolate 1 due to the greater degree of substitution:

However, these two enolates lead to different products. So, which product should be formed? I know that if a strong base like LDA was used, a proton will be abstracted from one of the less hindered terminal carbons. But hydroxide ion is small and should be able to abstract more hindered protons.


texts: Finding equilibrium concentrations in solution from initial reagent concentrations and equilibrium constant

texts:
We have the following reaction:
$$\ce{A + B<=>2C +D}$$
The initial concentration of $\ce{A}$ and $\ce{B}$ are $\pu{1M}$ each. $K_c$ is $\pu{1.0E8}$. Find the equilibrium concentration of $\ce{A}$.

This is what I have tried:
The initial concentration of A,B,C,D are 1,1,0,0 respectively
The final concentrations of A,B,C,D have to be ($1-\alpha$), ($1-\alpha$), $2\alpha$, $\alpha$ respectively. Therefore
$$K_c=\frac{[C]^c[D]^d}{[A]^a[B]^b}$$
$$10^8=\frac{(2\alpha)^2\alpha}{(1-\alpha)^2}$$
$$10^8(1-\alpha)^2=4\alpha^3$$
But even on solving this cubic equation on a calculator, the values are incorrect.


texts: Identification of lithium and strontium salts

texts:
I'm having trouble interpreting the results I got for my experiment.

As you should be well aware of, lithium and strontium both burn with crimson red when they are placed in a flame. Now, I can't decide which one it is.

Then I was told to do an experiment with the same salt where I had to add dilute hydrochloric acid and barium chloride. I had no visible change.

Does this last test help me with identifying between strontium and lithium? What element is it?


texts: Why only F, O and N form Hydrogen Bonds?

texts: Why only fluorine, oxygen and nitrogen can form hydrogen-bonds with the hydrogen of another molecule?


texts: Converting an Alcohol to Alkyl Chloride (Ibuprofen)

texts:
In the synthesis of Ibuprofen you can shake 1-(4-Isobutylphenyl)ethanol to produce 1-Chloro-1-(4-isobutylphenyl)ethane

$\hspace{7 mm}$

In a separatory funnel at room temperature.

Usually its only tertiary alcohols that can proceed this way so fast, under mild but in this reaction its a secondary alcohol. Is it to do with the alkyl group with the hydroxyl activating the aromatic ring or maybe the para isopropyl group?

Any advice on this would be greatly appreciated :)


texts: How do molecules with muons and electrons bond?

texts:
Is bonding specifically for and between electrons? Why cant two atoms share muons, which are different particles of same charge, spin and different mass?

Why there aren't muon-electron bonds?

Why is the octet (or eighteen valence electron) rule only for electrons, and not for all particles with similar charge and spin compared to the electron?


texts: What are the effects of Lithium Dioxide on the body?

texts:
My question is about how much science-fiction and how much chemistry is involved in the the 'Randy's Donuts' scene of Iron Man 2:

  Agent Romanoff injects Lithium Dioxide into Tony Stark's neck to remove the symptoms of Palladium poisoning.

My Question is: Is it safe to inject Lithium Dioxide into our body?
Does it have any side effects?


texts: Reaction of 2,4,6-triaminobenzoic acid in a protic medium and heat

texts:
The given answer is (A). At first I thought that it was a simple decarboxylation (due to high heat).
But that does not seem feasible at all as the ring has no electron withdrawing groups which stabilise the carbanion; infact it has electron donating groups which rules out decarboxylation. What else could be a possible mechanism here?
Edit:In the answer posted below could anyone explain how the hydrolysis of triamminobenzene occurs?


texts:
Consider the Lewis dot structures of the molecules fluoroform, $\ce{CHF3}$, and tetrafluoromethane, $\ce{CF4}$:

My first line of thought is that both of these molecules are symmetrical (the vectors from each individual atom naturally cancel each other out) with no lone pairs of electrons. Now I knew that just because they were symmetrical didn't automatically meant that they were non-polar. If they're symmetrical, they're usually non-polar but not always. This is one of those cases.

My next line of thought was that they both had to be polar and had dipole-dipole interactions. Then I later find out that the $\ce{CHF3}$ is actually the polar molecule with dipole-dipole interaction and $\ce{CF4}$ is the non-polar molecule with London-dispersion forces.
This bothered me a little bit because both of these molecules have a very electronegative atom (fluorine) that is more electronegative than any other element in the compound. This is why I thought they were both polar.

Why is tetrafluoromethane non-polar and fluoroform polar?


texts: Mixture of water, methanol and dichloromethane

texts: If I have a mixture of 25 vol% methanol in water and I mix it with an equal volume of dichloromethane (which is miscible with methanol but not water) can I roughly say that both phases (i.e. water and dichloromethane) will have the same methanol concentration upon reaching equilibrium? Or will it vary significantly based on the activity of each mixture?


texts: The chlorofluorocarbon reaction in the lab?

texts:
The putative reason for banning Freon and its class of chemical (chlorofluorocarbons) is that they will rise to the top of the atmosphere, to the ozone layer and "catalyze" the reduction of ozone to ordinary $\ce{O2}$.

The objection that the amount of chlorofluorocarbons would be tiny in comparison to the amount of ozone, is answered by the idea that the chlorofluorocarbons, do not do a simple reaction, but catalyze at high rate the conversion of $\ce{O3}$ into $\ce{O2}$. In other words, the idea is that a single molecule of chorofluorocarbons could convert millions of ozone molecules into $\ce{O2}$ every minute or something like that.

Unfortunately, this supposed reaction (which would seem to be unlikely on the face of it) seems to have never been duplicated in a laboratory, which I would expect would be easy to do.

Would it be possible to easily set up and measure this reaction in a laboratory? The goal would be to determine the rate of reaction. For example, given a certain molar concentration of chlorofluorocarbon in the reaction vessel, how fast is a given molar concentration of $\ce{O3}$ converted to $\ce{O2}$.


texts: How does water freeze and crystallize on a cold superhydrophobic surface?

texts:
Superhydrophobic surfaces are nano-structured to "repel" liquid water and there has been a lot of work done to understand the microscopics of wetting of these nanostructures.

What I currently am interested in understanding is wetting and freezing of water on a cold, below-freezing superhydrophobic surface.

I would expect that the ice would still have mechanical adhesion to the surface, but I don't know to what extent.

So my question is the following: How does water freeze and crystallize on a superhydrophobic surface?

I know this is a general question that would depend on the nature of how superhydrophobicity is achieved, so feel free to specifically treat a certain branch of superhydrophobic surfaces.


texts: How does a molecule search work by drawing in visual editor?

texts:
There are a lot of chemical search engines (such as ChemSpider's
Structure search) that allow users to draw and search for a molecule. How does it work? Is the comparison of images used? Could you give me an algorithm or pseudo code?


texts: Are sulfonyl-carboxylates stable in water?

texts:
This time I am interested in a specific type of acid anhydride, sulfonyl-carboxylates, i.e. compounds with the following molecular structure:

where $\ce{R2}$ can be an organic substituents or hydrogen atoms. $\ce{R1}$ can be an organic substituent only.


texts: Which is the central atom in Lewis Dot Structures?

texts:
What is the correct Lewis structure for hypochlorous acid, a compound containing chlorine, hydrogen and oxygen?

As shown in the following video, the central atom in Lewis Dot Structures is always the least electronegative atom of all the elements that make up the atom.
https://www.khanacademy.org/science/chemistry/chemical-bonds/copy-of-dot-structures/v/drawing-dot-structures

This way, you would expect chlorine to be the central atom. However, it is shown that oxygen is the central atom.

The ambiguity exists for molecules like $\ce{OCl_2}$ as well. What's the issue? Is this not a very consistent rule of thumb?


texts:
I want to run a reaction that needs diethyl ether as anti solvent in the last step (comes from articles).
But I can't use it due to its harmful effects on the body.
Is there any other solvent?

My reaction is about substitution of $\ce{-OH}$ of lignin with BiBB in THF and in other one in $\ce{EtOAc}$ as solvent.


texts: The equation representing the dissolution of cycasin


texts: I have recently seen a video of ruthenium on youtube. It says that ruthenium is invulnerable to many acids, especially aqua regia, but it gets destroyed by a simple household chemical, bleach. The video did not give a proper explanation about why this happens, it only gave the reaction mechanism. What is the reason for this Achilles' heel of ruthenium?


texts: How does bromine in bromine water become polarized enough for electrophilic substitution with phenol?

texts:
There's a question in my obscure school textbook that I couldn't find an answer to online.

How does Bromine in Bromine water become polarized enough for electrophilic substitution with Phenol?

This is asked just after explaining phenol's reaction with bromine water.
After searching online the closest concept I found was from chemguide:

In fact, bromine is a very polarisable molecule - in other words, the electrons in the bond are very easily pushed to one end or the other. As the bromine molecule approaches the ethene, the electrons in the pi bond tend to repel the electrons in the bromine-bromine bond, leaving the nearer bromine slightly positive and the further one slightly negative.

Does the same thing happen with the benzene ring's pi electrons in phenol, or is it different?


texts: Reaction/complexation of aluminium chloride and acetic acid

texts:
Thinking about Friedel-Crafts acylation using carboxylic acid anhydride got me wondering about how exactly aluminium chloride ends up in that reaction.
Generally, despite the fact that Friedel-Crafts alkylation can be carried out using catalytic amounts of aluminium chloride - when chloride of a carboxylic acid is used as an acylating agent in Friedel-Crafts acylation at least 1 equivalent of aluminium chloride has to be used. This is due to the fact that aluminium chloride is complexed by resulting ketone (please see figure below).

Formation of such complex takes aluminium chloride out of action: 1 mole of aluminium chloride gets deactivated for every 1 mole of ketone produced, so it can not activate another molecule of acid chloride. And this is the reason why Friedel-Crafts acylation needs stochiometric amounts of aluminium chloride. (This is often omitted when Friedel-Crafts acylation is being introduced in organic chemistry textbooks, but it is sometimes mentioned later on - especially when it comes to actual lab work and real life conducting Friedel-Crafts acylation.) In the end formation of a ketone-aluminium chloride complex is not a big problem because when chemist who was running the reaction decides to isolate the product, the ketone can be liberated by hydrolysis of that complex using aqueous acid (note that water is unwanted in Friedel-Crafts reaction).

In instance of using carboxylic acid anhydride at least 2 equivalents of aluminium chloride are needed. One surely ends up bounded to the ketone - similarly as described above, but I am not sure what exactly happens with the second equivalent. My guess is that it reacts somehow with carboxylic acid that was produced from anhydride while the other part of anhydride got bounded to aromatic unit.
Hence my questions:
(1) What happens with that second equivalent of aluminium chloride?
(2) How does aluminium chloride react with acetic acid in nonaqueous medium? (My guess would be that this is something like in the figure below. However, I don't know if reaction goes all the way to chelate or not.)


texts: How do we know the taste of dangerous compounds?

texts: For example,   this site tells that the taste of Copper sulfate, (which is very dangerous for consumption) is of "metallic, nauseating taste" and as many dangerous chemical compounds often have taste descriptions, does this mean people eat them to taste test?


texts: When water boils and you suddenly shut the heat off, a lot of steam arises from it just after you shut the heat off. Why this happens, I thought that maybe water condenzes very fast in small droplets so they get flown up?


texts: I am curious if there is any chemicals that react with alcohol to either produce a visible colour change or an odour someone could smell.


texts: Laboratory and commercial preparations of aniline other than reduction of nitroarenes

texts:
Till now I could only find one laboratory preparation of aniline, i.e. reducing nitrobenzene with $\ce{Sn}$ and concentrated $\ce{HCl}$. I'm confused if Hofmann degradation is only commercial.
I'd like to know if there are other processes to prepare aniline in laboratory.


texts: Why ammonium hydroxide precipitates metal salts?

texts:
When I was going through the chapter on pnicotgens, I got to know that ammonia acts as a Lewis base and it dissociates in water giving out hydroxide ion and the further hydroxide of ammonia, which we refer to as ammonium hydroxide, precipitates metal salts in a form of metal hydroxides.

I want to know the reason why this thing happens. According to me, ammonium hydroxide should form a complex with the metal being a base after donating a pair of electrons. Correct me if I am wrong. A reaction is given below as an example of a reaction between ammonium hydroxide and zinc sulfate:

$$\ce{ZnSO4 + 2 (NH3 * H2O) → Zn(OH)2 + (NH4)2SO4}$$