texts: Can anyone explain why in the electrolysis of aqueous solutions such as zinc nitrate, the oxidation  half equation shows hydroxide ions forming oxygen and water -   can this half equation be balanced producing oxygen and hydrogen ions - if not why not?


texts: Why exactly does molten NaCl explode, when it is poured into water?

texts:
Why does molten $\ce{NaCl}$ explode, when it is poured into water?
$\ce{NaCl}$ has a high melting point, $1074\ \mathrm{K}$ ($801~\mathrm{^\circ C}$). $\ce{NaCl}$ has a molar mass of $58.44\ \mathrm{g/mol}$, it has specific heat capacity of $36.79\ \mathrm{J/(K\cdot mol)} = 629.53\ \mathrm{J/(K \cdot kg)}$. therefore the $\ce{NaCl}$ at melting point temperature has $491,033\ \mathrm{kJ/kg}$ more thermal energy than $\ce{NaCl}$ in STP conditions ($1\ \mathrm{atm}, 20~\mathrm{^\circ C}$, temperature difference $= 780\ \mathrm{K}$)
According to one amateur video in youtube, the molten salt explodes when it is poured into water (c. 2:15)
What is the exact cause of the explosion?
The author of the video reasons that the phenomenon is purely physical and it is caused by that water heats up, vaporises and expands as a gas inside the glimp of very hot $\ce{NaCl}$ salt. But is it really everything that happens there?
Other possible processes present in such occasion are (this is just a list what comes into my mind):

rapid crystallisation of the $\ce{NaCl}$
chemical reaction between $\ce{Na}$ and water: $$\ce{2 Na (s) + 2 H2O (l) -> 2 NaOH (aq) + H2 (g)}$$ (this causes explosion if $\ce{Na}$ is inserted into $\ce{H2O}$)
reaction between $\ce{Cl}$ and water: $$\ce{Cl2 + H2O -> HOCl + HCl}$$
the rapid solubility of hot $\ce{NaCl}$ into water
thermal decomposition (thermolysis) of $\ce{H2O}$ into either monoatomic or diatomic hydrogen and oxygen, and reactions that follow this.

Also, the author fails to explain why no explosion occurs with sodium tetraborate nor sodium carbonate when each of them, in molten state, was poured into the water.


texts:
I have a problem solivng this chemical problem. Any help would be highly appreciative.

Sodium Thiosulfate can be made by the reaction

$\ce{Na_2CO_3 + 2Na_2S + 4SO_2 ->  3Na_2S_2O_3 + CO_2}$

Question: How many grams of $\ce{Na_2S}$ are required to react with 25.0 g of $\ce{Na_2CO_3}$ if $\ce{SO_2}$ is present in excess?

My attempt:

$25.0 \text{ g } \ce{Na_2CO_3}\frac{1 \text{ mol } \ce{Na_2CO_3}}{105.99}\frac{2}{1}\frac{78.05}{1}$

The answer from the book states: 25.9g$\ce{Na_2S}$


texts: How can cooling gases do not change their physical states?

texts:
It is stated in my book "All gases condense to form liquids or solids before -273.15 degree Celsius  is reached?

could you explain this statement generally and my question in the title specifically?


texts:
What would be the lewis structure for ammonium ion?
Is there a coordinate covalent bond as well in the structure?
My confusuion would be dealth with if i get the structure of ammonium cyanate as well.


texts:
I accidentally mixed bleach and acetone trying to remove hair dye stains from my shower wall. The mixture turned orange when the bleach and acetone touched. Could I have created phosgene gas unintentionally? I’m really concerned for my families safety. I opened the window in the bathroom and closed the door. I poured water on the surfaces where the bleach and acetone mixture was a few times and all around the tub to make it sure there was none left. Should I be concerned or no?

I see the post was closed. I appreciate the feedback I received. Unfortunately poison control did absolutely nothing for me so that’s why I had to resort to online help. Thanks.


texts:
Geminal diols are unstable, except for a few exceptions like chloral hydrate.

I wish to ask if a gem-diol alkene is also stable. Their structure:

suggests to me that the intramolecular hydrogen bond should stabilize the gem-diol.


texts: In my analytical chemistry book, I have seen that molecules' electrical conductance has been measured by putting sulfur-containing groups on them and using atomic force microscopy with a gold surface. They say that this works very well because of gold and sulfur's special affinity for one another. I know that thiols and disulfides will be very attracted to gold, forming very stable bonds. Why is this?


texts: Calculating the energy used during electrolysis of NaCl

texts:
Suppose we are getting the necessary $\ce{Na}$ for $\ce{HCl}$ out of $\ce{NaCl}$. We need to end up with $V = 100~\mathrm{m^3}$ of $\ce{HCl}$ at standard conditions. Assuming that $\ce{HCl}$ is an ideal gas, and using the ideal gas law, I found there are $$ n = 4272~\mathrm{mol}$$ of matter in those $100~\mathrm{m^3}$. The applied voltage to the cell is $$U = 3.6~\mathrm{V}$$ and the current utilization factor is $\mu=88\%$.
Then we also have Faraday's law of electrolysis:
$$\frac{m}{M}=\frac{q}{F}$$(the oxidation state of chlorine is $z=1$).
Since there is a constant voltage being applied to the cell, the energy used in this reaction is
$$E = \frac{UI \Delta t}{0.88} = \frac{Uq}{0.88} = 470~\mathrm{kWh}$$
However the correct answer is $$E=48.9~\mathrm{kWh}.$$ Where did I go wrong? Perhaps it's something blatantly obvious.


texts: How to calculate the vapor pressure of water?

texts:
$48~\mathrm{l}$ of dry $\ce{N2}$ passes through $36~\mathrm{g}$ $\ce{H2O}$ at $300~\mathrm{K}$, and this results in a water loss of $1.20~\mathrm{g}$. The vapor pressure of water is?

The solution says, that water loss is observed because of escape of water molecules with $\ce{N2}$ gas. Then it says that water vapours occupy the volume of $\ce{N2}$, i.e  $48~\mathrm{L}$, this part I am not able to understand. Why would water occupy the same volume as that of $\ce{N2}$, it isn't mentioned that these two are in some container of volume of $48~\mathrm{L}$. What is the logic behind this? Then the solution proceeds, by applying $pV=\frac{m\mathcal{R}T}{M}$.


texts: Are there any suitable catalysts for ferric oxide and aluminum reaction?

texts:
As an exercise, I am trying to figure out how to catalyze the reaction of ferric oxide and aluminum

Fe2O3 + 2Al -> 2Fe + Al2O3

I've been trying to find a substance A such that the reaction could be broken down into the steps:

Fe2O3 + A -> B + 2Fe

B + 2Al -> Al2O3 + A

And ΔGrxn for the first step is much less than that for the original reaction. I've had quite a bit of trouble finding online resources to assist me in my search. In general, are there any better methods for determining a suitable catalyst for such redox reactions? (education level high school junior, AP chem student).


texts: I know that certain elements like plutonium and certain isotopes of caesium are radioactive but what gives them this ability? If it's their electron/proton/neutron arrangement, what makes that arrangement give radioactive properties and how?


texts: Why does percent ionization of a weak acid decrease when the initial weak acid concentration increases?

texts: By the rules of the equibrilium, as the concentration of the acid increases, the reaction will want to dissolve more. So why does the percent ionization of a weak acid or base decrease when the initial weak acid concentration increases?


texts: Classes of Organometallic Compounds - Where do I put Grignard Reagents?

texts:
[Note- I've already seen this question Why do Magnesium and Lithium form *covalent* organometallic compounds? as user Mithoron was kind enough to point out, but the problem that I face is different though. MY problem here, is that if I'm asked whether Grignard reagents are a)Ionic compounds of electropositive metals or are they b) Sigma bonded Complexes what should my answer be?]

My school textbook defines Organometallics (A section under the chapter 'Coordination Chemistry') as "Compounds where the metal atom is directly linked to a carbon atom(s) " , and then it proceeded to give the following classes of Organometallics:

1) Ionic Compounds of Electropositive Metals

Includes compounds like Alkyl Sodium, Phenyl Lithium and Alkyl Magnesium Halides (Grignard Reagents)

2) Sigma Bonded Complexes

Includes the likes of Trimethyl Aluminium

3) Pi Bonded Complexes

Includes Zeise's salt and Ferrocene

4) Sigma and Pi Bonded Complexes

Includes transition metal carbonyls like Ni[(CO)_4]

Now the thing is, some other (relatively unheard of) reference material places Grignard reagents under Sigma bonded complexes. Now I'm not sure which one's right, or if both are right, or if both of them are wrong, since in my brain the R-Mg bond in the grignard reagents are polar covalent, i.e- smack in the middle, between covalent and ionic bonding.

So going by convention (if there even is a convention for something like this), I reiterate my question, which one's right?

[Additionally if there are more classes of Organometallic compounds that I haven't mentioned, I'd really appreciate it if someone would add on to it...]

Thanks!


texts:
I recently came across different names for the following compound:

Is the IUPAC name for this cyclohexol or cyclohexanol? Is the use of cyclohexol as seen in a google patent and in this Chinese thesis accurate?


texts: How to calculate the height of an hcp lattice?

texts:
A hexagonal closed packing (hcp) unit cell has an ABAB type of packing. For calculating the packing fraction we require the volume of the unit cell.

Volume of hcp lattice = (Base area) $\cdot$ (Height of unit cell)
Each hexagon has a side = $2\cdot r$
Base area = $6$ (Area of small equilateral triangles making up the hexagon)
$$=6 \cdot \frac{\sqrt{3}}{4}\times(2r)^2$$
$$=6 \cdot \sqrt{3} \cdot r^2$$

Hence, volume $= 6 \cdot \sqrt{3} \cdot r^2 $ (Height of unit cell)

This is the point where I am stuck. How do I find out the height of the unit cell?

I searched in textbooks and found out that height $= 4r \cdot \sqrt{\frac{2}{3}}$. Can you please explain why is this so?


texts:
In our textbook there are two topics that I can't make connection between:

hybrid orbitals which (as I understand) are used to demonstrate the spacial shape of molecules like CH4 with VSEPR while taking atomic orbitals in account.
molecular orbitals which are an accurate way to look at covalent bounds.

But the problem is: In molecular orbitals we start talking about "s, p, ..." orbitals again and not hybrid orbitals "sp, sp2, sp4, ...".

Why is it like that?


texts: Electron transfer in reaction between ammonia and hydrochloric acid

texts:
$$\ce{NH_3 + HCl -> NH_4Cl}$$

The electronic structure of ammonia is such so that the nitrogen atom has an outer shell with a lone pair of electrons.

When ammonia reacts with hydrochloric acid (above), the hydrogen from the $\ce{HCl}$ moves to the ammonia. However, it leaves its electrons behind because there is already a lone pair of 2 electrons on the $\ce{N}$ atom, allowing it to retain a $\mathrm{1s^2}$ shell.

Why doesn't the hydrogen take its electron over and nitrogen doesn't then "donate" an electron to the chlorine?


texts: Difference between acetocarmine and feulgen stain

texts: We did an experiment on observing mitosis in onion root tip cells, and I have observed that there are two ways of staining it, using acetocarmine and feulgen stain. What are the advantages of using each of them and the disadvantages, if there is one? What would be the difference, after all? Thank you in advance for your kind response.


texts: 19F NMR of hexafluorobromine(VII) cation

texts:
$\ce{[BrF6]+}$ is an octahedral species, and should have only one fluorine environment due to the symmetry. $\ce{Br}$ has nuclear spin $I=3/2$ and therefore is unlikely to cause splitting due to rapid interconversion between its spin up and spin down states averaging to a zero magnetic effect. Therefore I would expect one singlet in the $\ce{^19F}$ NMR spectrum.

However... the $\ce{^19F}$ NMR is actually two $1:1:1:1$ quartets (at low temperatures). Can someone help me find the flaws in my reasoning?


texts: Unique calling code for a chemical reaction

texts:
I'm writing a script and would like to use a "Gödel numbering" to search for specific reactions.

Is there any used procedure to assign an symbol (integer, possibly) to a chemical reaction? E.g.
$$CH_4+4O_2=CO_2+2H_2O\ \ \ \Longrightarrow \ \ \  121231412$$


texts: Which quantities change when choosing a different standard state?

texts:
Chemistry and biochemistry use a different standard state. For example, the standard hydrogen ion concentration is the one at pH = 0 in one case, and the one at neutral pH in the other case.

Which quantities change when choosing a different standard state, and which quantities have special values at standard state?


texts: Why is the pressure value altered in this gas law numerical?

texts:
When I work through the following problem it is unclear to me why 0.00120 mmHg is converted to 0.00332 mmHg.

  What is the temperature of 0.00332 g of mercury in the gas phase with pressure of 0.00120 mmHg and a volume of 435 L?

I converted the grams of mercury to moles and then used the ideal gas law constant of 62.36 to solve for T. Is there any reason that the pressure of 0.00120 mmHg should be converted to 0.00332 mmHg?


texts: Do carboxyl groups behave like bases and amino groups behave like acids when peptide bonds are created?

texts:
Peptide bonds are synthesized when the carboxyl group of one amino acid molecule reacts with the amino group of the other amino acid molecule, causing the release of a molecule of water.

Water molecules consist of a hydroxyl from a carboxyl group and a hydrogen from an amino group.

And that seems a bit strange to me, since carboxyl is an acid and should give a hydrogen (instead of hydroxyl) and amino groups are bases and should get proton (and not give a hydrogen).

So for me it looks like in creating this bond, the carboxyl group behaves like a base and amino group behaves like an acid. Is that correct?


texts: Realistic conditions for fuel container explosion

texts:
First off, I'm not actually trying to blow anything up. Also, my apologies if this isn't the right SE to ask. If so, I'd appreciate it if you could point me to the right SE.
I'm writing something where at a point I need a big explosion to happen. I've done some digging and I found out that the old bullet-fired-at-gas-tank trope is essentially just a trope, and that it alone is unlikely to cause an explosion.
The explosion needs to happen near a big mansion on an otherwise uninhabited island. The mansion is powered by an outdoor generator that runs on some kind of fuel, for example propane, though it can be anything else that makes sense and can more easily get me the explosion I need. There are fuel containers
to refill the generator sitting somewhere outside the mansion, and they need to be accidentally blown up during an action sequence.
The ideal explosion would be strong enough to blow up the closest wall of the mansion, so that the fire can spread inside the mansion, and this leads to my first issue: I have no idea if it's realistic to expect such a dramatic effect or not—for all I know, it might take far more fuel than it makes sense to keep in stock.
Secondly, as said just shooting one of the containers won't trigger an explosion. I understand that you need the right mixture of oxygen and fuel, and the containers would have to be exposed to sufficient heat for some time before they actually blow up. I thought that, maybe, if some containers are shot and start leaking, and then the leaked fuel somehow catches fire during the sequence, this might trigger an explosion, because air would start leaking into the containers that got a hole punched in them.
To sum up, my questions are:

Can a fuel explosion realistically blow up a nearby wall and spread a cloud of fire into the mansion so that at least the nearest room is almost completely on fire very quickly, without unrealistically huge amounts of fuel involved?

Can the explosion be caused by a bunch of fuel cans that were hit by bullets, started leaking, and were heated up by the flames that followed when the leaked fuel somehow caught fire? Would this take too long to happen (eg, ten minutes), or could it happen within a minute or two?


texts: How are octet-rule models supported by thermodynamics and quantum theory?

texts:
I understand that the four quantum numbers dictate how many electrons can "fit in a shell," but I don't understand how gaining a full octet is particularly energetically favorable.

The example of the ionization of sodium seems to make sense: the atom loses a single 3s electron, and the energy of the system is lowered significantly down to the 2p energy level.

However, the ionization of chlorine isn't as obvious to me: it is indeed granted its "full octet," but filling the last available space in the 3p suborbital would not lower the energy of the system. Rather, it would raise it slightly, as the newly added electron would experience some electron/electron repulsion.

Is the main drive for this ionization "reaction" the drop in energy in the formation of the cation? Do I have to consider molecular orbital theory to answer this question for covalent interactions?

I'm mainly wondering why there's a drive to form a full octet, particularly for the halogens, chalcogens, and pnictogens.


texts: What is the solublity of water in liquid carbon dioxide at low temperature?

texts:
The solubility of water in liquid carbon dioxide has been investigated by Hosmer W. Stone in 1943 from
-29 to about 22 °C.

Is there any research done on the solubility of water in liquid $\ce{CO2}$ at still lower temperatures ?


texts: Possible nonclassical ion from a bicyclic system

texts:
In this question a bicycling alcohol is reacted with acid to make what appears to be a tertiary carbocation, and the OP asked whether it could become aromatic.  The given answer suggests it could be, but only if a nonclassical ion is formed.  So, does that happen?

The substrate is 8a-methyl-1,3,4,8a-tetrahydronaphthalen-4a(2H)-ol.


texts: Explanation for behavior of acetic acid in aquaponic/hydroponic systems?

texts:
Because aquaponics is hydroponics with fish & bacteria, options for adjusting pH are limited.

Primarily people use phosphoric acid, hydrochloric acid, and nitric acid (heavily diluted).  A less popular but easy to acquire material is vinegar.

I've tried using it in a very alkaline solution (100 ppm calcium carbonates, 8.4 pH) and noticed that the pH would drop by a small amount before returning to it's original state.  Anecdotally, other aquaponic hobbyists have noticed a similar effect that is not replicated by the other acids. What is happening that the pH would lower temporarily and then rise back up over several hours?


texts: Determining absorption spectrum, magnitude of Δo and spin for Iron Oxalate

texts:
Iron Oxalate ions form an emerald green solution when dissolved. If the ions in solution appears emerald green to our eyes, what color of visible light is it mostly absorbing? What does that tell you about the magnitude of Δo (recall that E = hc/ƛ)? Determine if the complex is likely to be high spin or low spin based on this observation.

I know that the crystal field splitting affects the color of the compound, and that compounds with different magnitudes of Δo will appear different colors, corresponding to the wavelength of light that enters our eyes. Since Iron Oxalate ions appear green (490-560nm), I would guess that it is absorbing red light (650-750nm), which has the lowest energy wavelength on the visible light spectrum, which leads me to suspect that the complex is low spin. Is this correct? How might one go about finding the magnitude of Δo?


texts: Is d3-acetic acid more acidic than acetic acid?

texts:
The following table is from Solomons, Fryhle and Snyder Organic Chemistry, chapter 3, An Introduction to Organic Reactions and Their Mechanisms: Acids and Bases:

  Table 3.8 Isotopic substituents and inductive effect
  $$ \small
\begin{array}{ccc}
\hline
\text{Acid} & \ce{pK_a} & \text{Inductive effect of the substituent} \\
\hline
\ce{CH3-COOH} & 4.75 & \text{+I} \\
\ce{CD3-COOH} & 4.60 & \text{+I} \\
\hline
\end{array}
$$
  +I effect of deuterium is stronger than that of hydrogen. +I ($\ce{-CD3>-CH3}$)

Why is $\ce{CD3-COOH}$ more acidic than $\ce{CH3-COOH}$ despite being less electronegative? The book also said that $\ce{CD3} > \ce{CH3}$ in terms of + Inductive effect.


texts: Can dissolution reactions be endothermic?

texts:
Is it possible for a dissolution reaction of the form

$$\ce{X(s) ->[solvent] X (solv)}$$

or

$$\ce{M_mX_x (s) ->[solvent] m M^x+ (solv) + x X^m- (solv)}$$

to be endothermic, i.e. $\Delta_\mathrm r H > 0$?


texts: Why is the excitation energy different from the energy difference between the orbitals involved in transition?

texts: Why is the excitation energy different from the energy difference between the orbital from which a electron is excited to the orbital in which the electron is excited to? Consider that the transition mainly consists of the above specified 2 orbitals only. Do comment if I need to add additional information to the question.


texts: What is the significance of heating value?

texts:
Say I burned for example methane and propane to boil some water.
Methane has the heat of combustion of $\pu{890kJ/mol}$ and propane has the heat of combustion of $\pu{2200kJ/mol}$
What does the difference in heat of combustion tell us? In other words, propane's heat of combustion is bigger. Does that mean that methane emits less energy and therefore is less "environmentally harmful"? Is a higher heat of combustion better or a lower heat of combustion?


texts: How do water models fit into force field methods?

texts:
What I Understand:

In molecular mechanics, it is recognised that molecules tend to be composed of units that are structurally similar in a vast array of environments so atom types are defined from which molecular models can be built.

A force field is defined that describes the energy required to distort the molecule from equilibrium.[1]

$$E_\mathrm{FF} = E_\mathrm{str} + E_\mathrm{bend} + E_\mathrm{tors} + E_\mathrm{vdw} + E_\mathrm{el} + E_\mathrm{cross}$$

Once a functional form has been decided on, the field is parameterised based on empirical results.

What I Don't:

A large array of force fields have been developed, each different in their functional form or parameterisation. Numerous "water models" exist, and these appear to be force fields in their own right, often with far fewer energy terms.

The SPC model, for example, appears to contain only Coloumbic and Lennard-Jones terms, as described in Berendsen.[2]

  We developed a three—point charge model (on hydrogen and oxygen
  positions) with a Lennard— Jones 6—12 potential on the oxygen
  positions only.

What is the purpose of these water models?

Question:

Why are standalone water models required, and how are they incorporated into more general forcefields like MM2?

References

F. Jensen, Introduction to Computational Chemistry, John Wiley &  Sons, Chichester, 2007.
Berendsen, H. J. C., Postma, J. P. M., van Gunsteren, W. F.,
and Hermans, J., Interaction Models for Water in Relation to Protein Hydration, in: Intermolecular Forces: Proceedings of the Fourteenth Jerusalem Symposium on Quantum Chemistry and Biochemistry Held in Jerusalem, Israel, April 13--16, 1981. DOI: 10.1007/978-94-015-7658-1_21; pdf mirror


texts: Which of mono-, di-, triphenylmethane is the most acidic?

texts:
Question

  How would you compare the acidity of the most acidic proton in each of the following molecules?

  diphenylmethane
  toluene
  triphenylmethane

The answer says 3 is the most acidic, followed by 1, and finally 2 is the least acidic. Can someone please tell me how to determine this? I know the benzene group is electron donating group, but am not quite sure how to correlate this knowledge with determining the relative acidities.


texts:
My son has autism and we noticed that blueberries make him feel much better. The problem is blueberries contain sugars which interfere with diet he has (low carbohydrate).

How do I filter out the sugars (fructose?) without interfering with other compounds present in the juice? We can't add yeast and wait. Perfect option would be to add something that interacts only with the sugars and produces something neutral to the human body or is easily removed.


texts: How is the "quasi-steady-state" assumption of Michaelis-Menten kinetics different from the steady state assumption of ordinary kinetics?

texts:
In Wikipedia's article for Michaelis-Menten kinetics, it titles the "[ES] = constant" section the "Quasi-steady-state approximation". Lehninger's Principles of Biochemistry, 4th Ed. pp. 203ff call this "steady state kinetics".

I know that steady state is an assumption which is used for various kinetic models that have an intermediate, and I believe the term "steady state" is used in other settings as well. Is Wikipedia's use of "quasi" in the title for the enzyme kinetics reflective of $V_0$ only being the measurement of the initial rate, and thus the further assumption that [S] is constant also adds more uncertainty to the steady state assumption? If this isn't the reason (and I'm not certain that it is), why add a further descriptor that denotes uncertainty or inaccuracy when we already know that steady state is an assumption?


texts: How does ferrous iron coordinate nitrogen in a porphyrin ring?

texts:
In first semester biochemistry, my professor said that iron forms a coordination complex with nitrogens in the heme group.

I'm failing to understand what this even means since the charge on nitrogen does not change as a result of this bond. My organic chemistry textbook and biochemistry textbook do not even have a basic explanation of what is meant by this, and I can't find anything on the web.

How does iron form a bond with two of the nitrogens in the porphyrin ring, the histidine, and the oxygen?


texts: Why does one of Dalton's compound elements with oxygen and phosphor consists of four atoms instead of two?

texts:
I stumbled across a peculiar detail while reading the chapter about the  Chemical Revolution in Bowler and Morus' book Making Modern Science.
According to this book, Dalton argued that compound elements are created in the simplest possible way. For instance a compound consisting of equal number of X- and Y-atoms would then consist of one X-atom and one Y-atom. Still, in this illustration from Dalton's New System of Chemical Philosophy, oxygen with phosphor (compound 51) consists of two oxygen and two phosphor atoms. What is the reason for this?


texts: Is iron the most stable element in the periodic table?

texts:
According to the binding energy per nucleon vs mass number graph, it is observed that iron-56 has the maximum value of binding energy per nucleon ($\pu{8.75 MeV}$). It means that iron-56  is the most efficiently bound nucleus meaning that it has the least average mass per nucleon. This is the approximate basic reason why iron and nickel are very common metals in planetary cores since they are produced profusely as end products in supernovae and in the final stages of silicon burning in the stars. So, in one word, iron is quite stable.

But, what about helium and other noble gases? They are considered the most stable elements in the whole periodic table. But their binding energy per nucleon value is less than iron-56. So, they are not stable as iron-56. Is that true? Is iron the most stable element in the periodic table both structurally and chemically?


texts: Empirical and Molecular formula: Homework

texts:
I'm working on a high school chemistry book and want to double check one of the homework assignments. The question is for students to write the empirical and molecular formula for 1,2-dichloroethane.
I can't find this online. The molecular formula is given as C2H4Cl2, but could this also be the empirical formula? I don't find any sites as listing the empirical formula as CH2Cl.


texts: Making oxygen from iron oxide (aka rust) with sodium chloride?

texts:
I like videogames, and I've been playing a lot of "Oxygen Not Included" recently. It's not a perfect physics simulation, but it does appear to be realistic-ish (both Specific Heat and Thermal Conductivity make up non-trivial parts of the gameplay; attempting to respect the tyranny of the rocket equation; etc.)

The latest update added in a new reaction though, that has me scratching my head a bit:

  Rust (Iron Oxide) + Salt (NaCl) -> O2 + Cl

Other reactions implemented in the game make sense based on my (limited) understanding of chemistry, e.g.  Iron + Carbon + Lime = Steel, or H2O+ Electrolysis = H2 and O2, so I'm wondering if there's a rational basis for the Rust -> O2 reaction as well, or if this is the devs handwaving some chemistry for gameplay purposes. (Such as, for instance, the apparent annihilation of the Sodium into heat, above)


texts: Calculating pH of diprotic and amphoteric solutions

texts:
I am trying to understand this problem and its corresponding solution (complete solution not shown)

First off, from the above one can see that the equilibrium constants when $\ce{H2ASO4-}$ donates and receives a proton are as follows:
\begin{aligned}
\ce{H2AsO4 &<=> HAsO4^{2-} + H+} & K_2 &= 1.1 \cdot 10^{−7}\\
\ce{H2AsO4- + H+ &<=> H3AsO4}    & K_{-1} &= 1.6 \cdot 10^{2}\\
\end{aligned}

However, if this is an amphoteric substance as the solution claims, shouldn't both $K_a$ values be comparable? It seems logical that if it is able to act as both an acid and a base, the equilibrium constants should at least be similar to each other. Instead, one is several order of magnitudes larger than the other? Why can this be true and $\ce{H2ASO4-}$ still be an amphoteric substance?

Next, how did they arrive at the statement

  We approximately have the equality relation: $$\ce{[H3AsO4]} = \ce{[HAsO4^{2−}]}$$

What is the evidence that shows this to be true? Isn't the $K_a$ value of the basic reaction ($1.6 \times 10^2$) much larger than that of the acidic reaction? Why should the concentrations be equal?

Finally, let's say you are calculating the pH for the diprotic substance $\ce{H2S}$, which undergoes the following diassociations:

$$\ce{H2S <=> H+ + HS-}$$
$$\ce{HS- <=> H+ + S^{2-}}$$

To find the pH you would assume that the first reaction is dominant, and that the effects of the second reaction consuming $\ce{HS-}$ are minimal, and then calculate the pH from there — right?

However, why can't you treat $\ce{HS-}$ as an amphoteric substance (because it can both gain and lose a proton) and then calculate the pH as you would for an amphoteric substance (as seen in the image at the beginning)?


texts: Why doesn't a neutral solution at any temperature have pH 7?

texts:
I am given 4 statements to choose from and find which is correct about a neutral solution:

$K_\mathrm{w} = \pu{1.00\times10^-14 mol^2 dm^{-6}}$
The solution contains only $\ce{H2O}$
$\ce{[H+] = [OH-]}$
$\ce{pH =7}$

I can see that the first statement is wrong as that is only the case at $\pu{25 ^\circ C}$.

The second statement is also incorrect - it can be when $\ce{H+}$ ions and $\ce{OH-}$ are equal in concentration.
So I can see that option 3 is correct.

However, I am confused why option 4 is wrong.
Why is option 4 wrong?


texts: Why is the melting point of magnesium anomalous?

texts:
The melting and boiling points for the Group II elements are as follows:
$$\begin{array}{ccc}
\text{Element} & \text{Melting point / }\mathrm{^\circ C} \\
\hline
\ce{Be} & 1289 \\
\ce{Mg} & 650 \\
\ce{Ca} & 842 \\
\ce{Sr} & 769 \\
\ce{Ba} & 729
\end{array}$$
(source: Greenwood & Earnshaw, Chemistry of the Elements 2nd ed., p 112)

As you can see, the overall trend is decreasing, but magnesium is an exception. Just like the alkali metals, melting point should decrease for the heavier elements of the group because of the weaker bonding. Why is magnesium different?

The other trends for this group, such as density, atomic radius, and first ionization energy follow the expected pattern with no exceptions.


texts: How can an ionic bond have partial covalent in character?

texts:
I was going through the topic of 'ionic bond' and read this:

  No bond is 100% ionic in character. It has some percentage of covalent character.

I didn't understand how an ionic bond can be partially covalent in character. Please explain along with an example.


texts: Why does the Birch reaction not yield fully saturated products?

texts:
Why isn't benzene reduced all the way down to cyclohexane when performing a Birch reaction? (Why is it not reduced further?)

Similarly for the reaction with sodium dissolved in liquid ammonia, why isn't an alkyne reduced fully to an alkane?


texts: What is the use to know that a compound optically active or not? Is it important to know that?


texts:
When choosing the ideal indicator during a titration, there are two considerations to keep in mind:

The pH = pKa of the equivalence point
The indicator has a small range (<±1) over which it can change color

Which factor is more important when deciding over two indicators to see which is best?


texts: In the aquation of cis-platin, why are the chloride ligands, and not ammonia, replaced with water, despite chloride's larger trans effect?

texts:
https://doi.org/10.1021/ic000847w
In this paper, the aquation of cisplatin is examined. When used to treat cancer, the chlorides are substituted with water molecules, which seems to go against the trans rule discussed in my inorganic textbook. Supposedly ligands trans to chloride are more easily replaced than those trans to ammonia.


texts: How to name an unsaturated spiro compound with many substituents?

texts: I've been trying to name this compound, but I just can't, I've gotten a brilliant answer already, it's(8E,11Z,15Z)-4-amino-11-carbamoyl-3-chloro-2-(chlorocarbonyl)-9-cyano-5-formyl-4-hydroxy-13-methoxy-12-(methoxycarbonyl)-10-oxospiro[6.9]hexadeca-2,8,11,15-tetraene-8,14-dicarboxylic acid. I just want to know if there's any contrary opinion from the answer.


texts: As I know, in electroplating method, the type of voltage used is DC voltage. My question is, does replacing DC current supply by AC one affect the functioning of the cell? And why?


texts: Which single organic molecule has strong absorbance throughout the visible range?

texts: Is there a single organic molecule that has strong absorbance throughout the visible range? For example a black dye that is based on a single molecule?


texts: Reaction stoichiometry for calculation of Kp

texts:
NH$_2$CO$_2$NH$_4$(s)⇌$2$ NH$_3$(g)+ CO$_2$(g)

I want to calculate K$_p$ for the reaction above, given that the total pressure is $0.63$ bar.
My calculations:
$0.63$ = p(CO$_2$) + p(NH$_3$)
,   where p(NH$_3$) = $1/2$ p(CO$_2$) (For every NH$_3$ half a CO$_2$ is needed)
$0.63$ = p(CO$_2$) + ($1/2$ p(CO$_2$) = $3/2$p(CO$_2$) -> p(CO$_2$) = $0.42$ bar , p(NH$_3$) = $0.21$ bar
So, K$_p$ = ($0.21$)$^2$ * ($0.42$) = $0.0185$ bar$^3$
However, the answer key's way of calculating this is:
$0.63$ = p(CO$_2$) + p(NH$_3$)
,   where p(NH$_3$) = $2$ p(CO$_2$)
$0.63$ = $3$p(CO$_2$) , so that  p(CO$_2$) = $0.21$ bar and p(NH$_3$) = $0.42$ bar
How can p(NH$_3$) = $2$ p(CO$_2$)? Isn't that wrong? Or am I thinking wrong? I have contacted my professor but haven't received an answer yet and our exam is tomorrow so hopefully someone here can help me understand. Thank you!


texts: Mechanism of formation of peak of mass spectrum of isobutane at m/z = 27

texts:
Here is the mass spectrum of isobutane:

(source: nist.gov)
Clearly the peak at $\mathrm{m/z} = 27$ corresponds to the species $\ce{C2H3+}$, the "protonated acetylene".
I am interested in possible formations for its formation from the molecular ion $\ce{t-BuH+}$.


texts: Doubt in a nomenclature for equilibrium constant

texts: Why is there $H,N$ and $CO$ attached to the suffix of equilibrium constants? Particularly how to use these as suffixes? Nothing can be extracted from the reaction. There are many $H,N$ and so on like $C$ and $O$ so how do I know which one to use as suffix here for getting the equilibrium constant.  If it is $K_{N}$ and $K_{H}$ then why is it $K_{CO}$?It should be $K_C$ isn't it? Please explain me the analogy for the nomenclature. What does the equilibrium constant depict at all?


texts: How to interpret TLC data regarding the purity of one’s sample

texts:
The picture provided is a sketch of my TLC data from the lab along with the $R_f$ values for $i$ (initial, un-recrystallized aspirin) $= 0.429$, $a$ (acetylsalicylic acid) $= 0.429$, and $s$ (salicylic acid) $= 0.571$.

One of the questions in my post lab was:

  Based on the TLC data, discuss the purity of the impure aspirin sample, explain your reasoning.

So far, I have said that based on the data, the aspirin sample would be considered pure because there were no multiple spots in any lane. I don't know how else to elaborate on this. What can I say about the $R_f$ values?


texts: Mechanism of Possible Acid Catalysed Ring Opening

texts:
Here's a problem I'm stuck with -

The first step looks like the usual addition of hydroxylamine to the ketone, resulting in two diastereomeric oximes (this is probably what (A) is). Further, in the second step, the acid can protonate the hydroxyl group of the oxime, or catalyse ring opening.  I don't see how to decide which one occurs.

Moreover, the final product doesn't contain three and four membered rings at all - and has a cyanide group! I wonder how that happened. Please help me figure out the mechanism for the conversion, thank you!


texts: Favourability of leaving groups in nucleophilic aromatic substitution

texts:
It is known that the order of leaving group favourability of the halide ions changes when we go from nucleophilic substitution, in the form of $
\ce {S_N1}$ and $\ce {S_N2}$ reactions, to nucleophilic aromatic substitution reactions ($\ce {S_NAr}$). In the former, the primary consideration is the strength of the $\ce {C-X}$ bond since the rate-determining step would always involve $\ce {C-X}$ bond cleavage. Thus, the order starts with $\ce {I^-}$  as the most favourable and $\ce {F^-}$ as the least. However, in the latter, the primary consideration is the ability of the halogen atom to withdraw electron density from the carbon atom it is attached to. This is because the rate-determining step is the initial addition to form the meisenheimer intermediate, which does not involve $\ce {C-X}$ bond cleavage. Thus, the order starts with $\ce {F-}$ as the most favourable and $\ce {I^-}$ as the least.

Apart from analysing the favourability of the halides as leaving groups in $\ce {S_NAR}$ reactions, I hardly see this concept being used to analyse the favourability of other leaving groups in $\ce {S_NAr}$ reactions. How would conventionally "bad" nucleophiles, such as $\ce {CH3O^-}$ or $\ce {OH^-}$, fare in such reactions? Would they be as superior as leaving groups like $\ce {F^-}$ or $\ce {Cl^-}$ in $\ce {S_NAr}$ reactions?

Some information is provided in Carey & Sundberg (2007) on this:

  Groups other than halogen can serve as leaving groups. Alkoxy groups are very poor leaving groups in $\ce {S_N2}$ reactions but can act as leaving groups in aromatic substitution. The reason is the same as for the inverted order of reactivity for the halogens. The rate-determining step is the addition, and the alkoxide can be eliminated in the energetically favorable rearomatization.

Reference

Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry Part A. Structure and Mechanisms (5th ed.). Springer, 2007.


texts: Good resource for stereochemistry of more than 4 substituents?

texts:
I have several classes of problems I'm facing in which I'd like to be able to discuss stereochemistry of non-tetrahedral centers. Specifically, I'd like to be able to check that the absolute configuration around a (for instance) trigonal bipyramidal transition state matches the absolute configuration that I've calculated.

For instance, these (chemically meaningless) trigonal bipyramidal structures are not superimposable:

What's a good resource discussing "higher order" stereochemistry? I'm particularly interested in classification of stereochemistries and in exchange rules for different orderings (analogous to the parity rules for tetrahedral centers). I'm coming from a computational/algorithmic slant.

The best (only) resource I've found so far is the opensmiles specification: http://opensmiles.org/opensmiles.html#_trigonal_bipyramidal_centers. I'm happy to purchase a book, or academic paper, or read program source code.


texts:
I have only come across polysaccharides from monosaccharides that has undergone intramolecular cyclization reaction.  I was wondering if it is possible for polysaccharides to form from linear sugars? I think that the answer lies in how the other glycosidic bond is formed, however my knowledge of chemistry is limited so I don't know if bond formation is possible with a linear sugar.

I know a carboxylic acid group can react with a hydroxyl group, and aldehyde can be oxidised to carboxylic acid. So my guess is that it is possible to create a long ester chain from aldoses but not ketoses (as ketone group cannot react and is fully oxidised). Although then I think it would no longer classify as a polysaccharide but a poly(ester)? I'm sure these exist — I have heard of polyester of course! — although I have not come across any others specifically.


texts: How can we justify setting the affinity $\sum_i \mu_i \nu_i$ equal to zero at chemical equilibrium?

texts:
Let $\sum_A \nu_A A \rightarrow \sum_B \nu_B B$ be a general reaction whose progress during time interval $dt$ is measured by $d\zeta$, so the amount of reactants consumed and products generated in mole would be $d N_i=\nu_i d\zeta$, wherein, $\nu_i$ would take negative values for the reactants being consumed.

From on the other hand we already know from the second law of thermodynamics that the reaction will occur in the direction in which $\sum_i \mu_i dN_i \le 0$, wherein, $\mu_i=\frac{\partial G}{\partial N_i}\bigr|_{p,T,N_j\;(j\ne i)}$ are the chemical potentials, so that we would have:
$$\left(\sum_i \mu_i \nu_i\right)\; d\zeta \le 0$$
The equality implies reversibility and should denote the equilibrium (am I right?). At the equilibrium it is clear that the progression of the reaction should vanish and we should have $d\zeta=0$, so that the term $\left(\sum_i \mu_i \nu_i\right)$ should be free to gain any positive, zero or negative finite value. However, this is not what Guggenheim has written in his Thermodynamics book. He has first assumed in a given direction the reaction progresses, so that in that direction $d\zeta>0$, then has canceled out this positive quantity from the inequality and achieved: $\left(\sum_i \mu_i \nu_i\right) \le 0$, and eventually concluded that at the equilibrium the equality holds and we should have $\left(\sum_i \mu_i \nu_i\right) = 0$.

But how is it justified to be true when we already know at the equilibrium $d\zeta>0$ doesn\t hold and we should instead write: $d\zeta=0$?

Thanks for bearing with me, I'm new to chemistry.


texts: Which has greater N-O bond length: NO or NOCl?

texts:
I came across this question. According to me, $\ce{NO}$ should have a shorter bond length as it has a triple bond, while $\ce{NOCl}$ has a double bond.
But the answer is given that $\ce{NO}$ has greater bond length than $\ce{NOCl}$. Why?
Is the answer wrong


texts: We know that there are countless organic compounds of carbon chain because of carbon's catenation. Silicon also is in the same group of carbon. Does it also have the catenation property? If not, why?


texts:
In nitrogen inversion, the lone pair changes its direction continuously.

Does this in any way delocalize the charge density on the nitrogen making it less nucleophilic and less basic than another nitrogen attached to, say, a bridgehead carbon?

Consider the specific case of
Quinuclidine and tri-methyl amine. Which will be more nucleophilic among them and why?


texts: Why does BCF (boron carbofluoride) not exist?

texts:
$\ce{BCF}$ (boron carbofluoride, or carbon borofluoride, not to be confused with another so-called BCF molecule that has nothing to do with it) should exist as a vapor molecule with the bonds $\ce{B≡C-F}$, it's simple; but it doesn't seem to exist, or I can't find any information (I just found a heavy thesis where $\ce{H2··FCB}$ —a theoretical molecule with Van Der Waals forces— is computationally studied, but it turns to be quite unstable even with the help of $\ce{H2}$).
Instead, other molecules like $\ce{C2O}$, $\ce{FBO}$, $\ce{NCF}$, vapor $\ce{BN}$, etc, do exist.

Why not $\ce{BCF}$ or $\ce{BCCl}$?


texts: Solve this mole fraction calculation with incomplete information

texts:
I am currently trying to solve a problem that seems quite simple at the beginning but the complexity reveals itself soon thereafter. The problem is the following:

  You mix a known mass of water with a known mass of ethanol. Then you fill up the flask to the 50 mL mark with water, but cannot weigh the contents when you're done. What is the molar fraction of ethanol in this mixture?

My attempt at solving this problem is to basically calculate the initial molar fraction, and then stepwise add small virtual amounts of water. Then the new molar fraction is calculated, and somehow the excess volume (which is negative for the water-ethanol mixture) would also be included somewhere here. This is repeated until the final volume is reached.

An other attempt would be to simply neglect the excess volume. While this might be fine at the edges of the molar fractions, it would introduce a grave error towards the middle. Or is the error still negligible?

Are these reasonable attempts or am I completely missing something here?


texts: Having problems running DFTB using dftb.org parameter files on Gauss 09 (G09)?

texts: I ran into an issue trying to run dftb.org parameter files on G09 and found questions asked on this but not answers.  I thought I would post the solution here to help anyone else who may run into this problem.


texts: Is ethanol an acid or a base or amphoteric?

texts: Is ethanol considered to be an acid or a base? Or does it act as an amphoteric species? Is acidity and basicity a relative concept? Also, can someone please explain this on the basis of the Brønsted–Lowry acids/bases theory which is based on the protonic concept; will it donate or accept $\ce{H+}$ ions? I'm unsure which acid base theory should I follow in this case, any help will be appreciated.


texts: Does quantum mechanics play a role in protein folding?

texts: Protein folding takes a very long time (relatively speaking) when thinking of quantum mechanical effect. However, for the initial micro-steps of folding, when an atom, or a configuration of atoms, can go (freely speaking) right or left (that is, to other possible configurations), in processes that take less than a picosecond, isn't QM relevant? that is, the atom has a probability to go to either places, in a QM sense, that it goes to both places, and due to interaction with the world, it's wave-function collapses or localizes and that is how the folding progresses?


texts: Why can't antiaromatic compounds just escape planarity and become non-aromatic to avoid destabilization?

texts:
Why can't just all anti-aromatic systems lose planarity (and hence conjugation) and be non-aromatic like cyclooctatetraene ?

Would they not be more stable that way? Because anti-aromatic systems tend to be highly destabilized.

What can be a good working rule to predict whether an anti-aromatic system will remain anti-aromatic or whether it will somehow manage to lose planarity and become non-aromatic?


texts: Usually, strong acid anions and strong base cations don't get hydrolysed. But I've noticed through some questions that $\ce{Ag^+}$ doesn't seem to get hydrolysed, why is that? Is there any concept that I'm not aware of that predicts which ions get hydrolysed and which don't, or is it just the ions from strong acids/bases don't get hydrolysed?


texts: Potassium Manganate and Acidified Potassium Dichromate colour changes

texts:
I would be obliged if somebody could explain the colour changes for the reduction of potassium manganate and acidified potassium dichromate. I understand that for potassium manganate, it is being reduced differently and this gives us a colour change. But I can’t understand the acid, base, neutral reactions.

I also keep on seeing this equation:

$$\ce{MnO4- + 8H+ + 5e- -> Mn^2+ + 4H2O}$$

Unfortunately  I cannot understand it, possibly because it’s an net equations and not the entire reaction.


texts:
I understand why photos based on organic dyes would fade (discussed previously). But photos based on metallic silver fade as well such as like the one shown below. As a metal (a fairly stable one at that) I would think silver should be resilient to fading but still old black and white photos do fade.

What causes old black and white photographs to fade?

Source: www.photo-restoration.co.uk


texts: Inductive effect on stability of free radical

texts:
How does inductive effect affect the stability of free radical?
I can't seem to understand whether the carbon with the odd electron is deficient or not. That is, whether a +I group, like alkyl, will stabilize it or not?
I know that an adjacent alkyl group like - CH3 will anyway stabilize it by hyperconjugation.


texts: Explanation of steric hindrance and existence of PI5

texts:
I have come across a following line in my textbook:

  $\ce{PI5}$ does not exist due to steric hindrance.

I searched for the explanation of steric hindrance in Wikipedia but couldn't understand it. Can anyone explain steric hindrance in simpler language?

Wikipedia says:

  The existence of $\ce{PI5}$ has been claimed intermittently since the
  early 1900s. The claim is disputed: "The pentaiodide does not exist
  (except perhaps as $\ce{PI3\cdot I2}$, but certainly not as
  $\ce{PI4+I-}$)".

What does this mean?


texts: NMR - coupling of chemically equivalent protons

texts:
In Klein's Organic Chemistry 3rd Edition page 671, it states

  This observation, called the n + 1 rule, only applies when all of the neighboring protons are chemically equivalent to each other.

However, in the following page, it states

  Equivalent protons do not split each other

The first statement infers that for the n + 1 rule to be valid, the protons must be chemically equivalent - inferring that equivalent protons can couple, while the second statement directly contradicts this.

Could my misunderstanding be clarified?


texts: What is the hidden meaning of electrochemical stability window?

texts: I don't really get the real meaning of the electrochemical stability window. I googled a lot, and the only thing I understand about the electrochemical stability window is that it's the voltage range that the substance is not oxidized and reduced. However, what does this term imply? I mean, I wonder that how we use this concept in practice.


texts: Why are there no hydrogen atoms in the crystal structure of a biomolecule?

texts: I am taking a physics and chemistry at the nanoscale class at my university and for a project I must learn how to use Visual Molecular Dynamics (VMD). One of the models involved in this project is apo-core-streptavidin in complex with biotin at pH 4.5 (1SWE.pdb).  The crystal structure can be found protein data bank. There are no hydrogen atoms in this file/model and I was wondering why that is.  I can't find the answer to this anywhere online.


texts:
I have a valuable soccer ball. It is not real leather, but a synthetic leather.

I used this cleaning agent to remove a few marks:

https://www.amazon.co.uk/Motsenbockers-Lift-Off-Graffiti-Remover-Trigger/dp/B00N3B25LU

However, I stupidly forgot to wait for the ball to dry and then placed it within an orange plastic carrier bag. Now the cleaning agent has reacted with the dye and there's a yellow-tint stain.

I have tried using acetone and these:

https://www.amazon.co.uk/Dr-Beckmann-Stain-Devils-Survival/dp/B07TKJPH7D/ref=sr_1_14?keywords=dr+beckmann&qid=1575488301&sr=8-14

but I cannot remove the stain.

Does anyone with chemistry knowledge know what else I could try?

UPDATE:

Got it out in the end. I used Dr Beckmann Stain Devils tea & wine, cut some cloth in to the shape of the area I wanted to clean, poured water, then the powder, then water on top and left for hours. Took multiple attempts.


texts: Why is ascorbic acid (vitamin c) readily oxidised in the presence of oxygen?

texts: I know that vitamin c is notoriously unstable in aerobic conditions, but I'm not sure how to explain why it is - is it due to redox potential, acid strength etc?


texts: Is cis- or trans-cycloundecene more stable?

texts:
While reading about cis/trans isomerism in cycloalkenes, I came across the following statement:

When the number of carbon atoms in a cycloalkane is less than 11, the cis form is more stable than the trans form. When it is greater than 11, the trans form is more stable than the cis form.

An obvious question came to my mind: What if the number of carbon atoms in the ring is "equal" to 11? Which form will be more stable - cis or trans? I think both will be of the same stability, but would like to have some clarification in this regard.

I searched my books and didn't find any specifications on the stability of cis or trans forms, for a ring containing exactly 11 carbon atoms. I read the answers to the question Stability of cis vs trans isomers? but they discuss only the cases "less than 11" and "greater than 11" but not "equal to 11".


texts: Obtaining atomic form factor from electron density?

texts:
I know that atomic form factors for x-ray scattering are obtained by Fourier transform of the electronic charge density.

I am looking for a citable elementary source (book, review, article) which covers the systematic and explicit derivation of the relationship between electronic charge density and the atomic form factor, to which people unfamiliar with the connection can be referred to for better context.


texts: Geometric isomers of substituted methylidenecyclohexane?

texts:
My thoughts on the problem:
I am sort compound of sure  C and D will not show geometric isomerism because of the same groups (H and H) attached.
In compound A and B, suppose I swap the positions of H and Cl, I notice that it is not possible to obtain the new compound by rotation of the original one.

My doubt: Does that mean A and B show geometric isomerism.  Also is my method, of interchanging the positions of H and Cl and checking if the same compound can be obtained by rotation, correct?


texts: What is there in this 3D representation of organic molecules I fail to grasp?

texts:
I think there's a basic idea I'm missing about 3 Dimensional representation of molecules. I think it may be about converting to Fischer representation. Consider the following two products of bromination of an alkene, the first one being for cis-form and the 2nd one for trans-form.

I know the question may sound stupid, but it's crucial to get the basics. Why is the product II) the meso form and the products I) are the optically active forms. By what I know, the solid wedge goes towards the observer, so in product II), shouldn't the Bromine substituent(or maybe the $CH_3$ substituent) and $H$ atom be on the 'same side', making it the one optically active?


texts: Evaporation of concentrated formic acid and semi-concentrated sulfuric acid at room temperature

texts:
I recently looked at a reaction where CO is synthesized using formic acid and sulfuric acid, which seems to be one of the easier to control reactions for this, and obviously ventilation etc is necessary.

However I was wondering, is ventilation only necessary because of the dangerous nature of CO, or also because of the vapors or formic and sulfuric acid? I was quite into chemistry in school and after, but I do not remember that much, so I feel like I should know this but I cannot recall anymore.
So at room temperature, if you would take a small amount of each of these acids and keep them either separately or mixed together, how fast/how much would evaporate and create dangerous acid vapor?


texts: Carbon 11 radiolabeled inhaled Beta-2 agonist or corticosteroids, is it possible?

texts:
Background
Positron emission tomography (PET) is a highly sensitive imaging modality that can provide in vivo quantitative information of biological processes at a biochemical level. PET relies upon the administration of a chemical probe, often called a radiopharmaceutical, that is labeled with a short-lived positron-emitting radionuclide, examples of which are $\ce{^{11}C} \ (t_{1/2} = \pu{20.4 min})$ and $\ce{^{18}F} \ (t_{1/2} = \pu{109.7 min})$. Carbon-11 is one of the most useful radionuclides for PET chemistry, since its introduction into a biologically active molecule has minimal effects on the (bio)chemical properties of the compound (Ref.: Dahl, et al., Clin. Transl. Imaging 2017, 5, 275–289)
Biologicals of interest
Beta-2-Agonists are effective bronchodilators due primarily to their ability to relax airway smooth muscle (ASM). They exert their effects via their binding to the active site of b2-ARs, which are densely located on ASM. The presumed cellular mechanism of action involves the canonical signaling pathway via activation of Adenylyl cyclase (AC) and generation of intracellular cAMP,
which in turn can activate the effector molecules cAMP-dependent protein kinase A (PKA) and Epac, a Rap1 guanine nucleotide exchange factor. However, there is still little known regarding these pathways in airway cells (Ref.: Am J Respir. Crit. Care Med. 2013, 187(7), 690–696).
Question
Currently radiolabeled lung studies use labeled drugs that are produced for inhalation are "association” products, that is, the label is associated with the drug but not firmly bound to the drug. Without a firm bond between the active pharmaceutical ingredient (API) and the radiotracer, images must be acquired immediately post-inhalation before the dissociation of the label from the drug leads to a circulating level of absorbed radioactivity that could introduce an unacceptable error in the measurement of radioactivity in the lung.
Carbon-11 radiolabeled ICS or Beta-2 agonists would enhance our understanding of the cellular mechanism of action. Anyone aware of work in this area?

References:

Kenneth Dahl, Christer Halldin, Magnus Schou, "New methodologies for the preparation of carbon-11 labeled radiopharmaceuticals," Clinical and Translational Imaging 2017, 5, 275–289 (DOI: https://doi.org/10.1007/s40336-017-0223-1).
Mario Cazzola, Clive P. Page, Paola Rogliani, M. Gabriella Matera, "$\beta_2$-Agonist Therapy in Lung Disease," Am. J. Respir. Crit. Care Med. 2013, 187(7), 690–696 (DOI: https://doi.org/10.1164/rccm.201209-1739PP).


texts: What happens to the pressure of gas when only one molecule of it is placed in a very large container?

texts:
We say that pressure due to gas is constant throughout the container. Pressure is created by molecules present in it. When there are many molecules I agree that they can apply the same pressure all over.

But when there are very few or just one molecule in the container, how can that single molecule create a uniform pressure in the container. I mean pressure will be created (say in a manometer) when  a molecule applies force on it (Hg). If we take a very large container and place just one molecule and also keep two manometers at the two extremes. Then how can that single molecule create the same pressure or apply the same force on both the manometers at the same time (container is very large)?


texts:
I just got asked this question on an interview:
I transported Polyol F0350 in 3 tanks. Upon arrival one tank was determined to have an unacceptable water content. It may have been contaminated with seawater, industrial water or distilled water. What tests do I perform to determine the water source and what type of mitigation do I recommend to be most cost productive - off blending the product or offering it for sale at a reduced price?


texts: What prevents everyday objects from reacting?

texts:
This may be a stupid question but I would like to know what prevents chemical reactions from happening among common objects in everyday life? The opposite would be, what requirements must be met for chemical reactions?

For example, as I am typing this what prevents no reaction between my fingers and the keyboard, or everyday objects such as chairs, tables, etc. In other words, why do we not constantly see chemical processes happening all around us constantly? Why don't my feet chemically react with the ground, my pencil reacts with the air, my fridge with the floor, etc...

There must be electron transfer such as conductivity, and charging but why no chemical reactions? Even as I am in AP Chemistry and understand Thermodynamics, Hess' Law, and so on, I am too embarrassed to ask my teacher with such a silly question.


texts:
When I go through oxides of period 3 elements in periodic table I came across a term "highest oxides" and when I searched I didn't found any appreciative answer for my question.

What are highest oxides and why they are called so?


texts: Is it possible to get energy from frozen methane without oxygen?

texts:
In one of the solar system documentaries it was mentioned there are moons in the solar system with lakes of frozen methane.

Assuming humans or robots or whatever could make it there, would there be a way to extract energy from frozen methane without using oxygen? Otherwise, it would seem that the oxygen would have to be carried there as well.

Is it possible to recycle the oxygen efficiently enough to burn methane again and again?


texts: Difference between backbonding and hyperconjugation and conjugation

texts:
What is the difference between backbonding and hyperconjugation and conjugation?
I mean the basic differences as all are concerned with donation of electrons. What is the most striking effect of each that differentiate them from others.


texts: Why must the total increase in oxidation numbers equal the total decrease of them in redox reactions?

texts:
In my book, under the topic of redox reactions, it is given,

  In all redox reactions, the total increase in oxidation number must be equal to the total decrease in oxidation number.

Is this a consequence of "Charges can never be created. The total charge of a system remains constant", or something else?

For the reaction,
$$\ce{
10 \color{red}{FeSO4} + 2 \color{red}{KMnO4} + 8 H2SO4 -> 5\color{red}{Fe2(SO4)3} + 2\color{red}{MnSO4} + K2SO4 + 8 H2O
}$$

(Reactants and products in red undergo oxidation or reduction)

For the above reaction, I tried whether the property stated above works or not.

The oxidation state of Fe and Mn in the reactants side are +2 and +7 respectively. The oxidation states of these elements in the product side are +3 and +2 respectively. The increase in OS is 1 and the decrease is 5.

Finally, the increase and decrease in oxidation states are not equal.

Kindly give an explanation for this fact.


texts: Is it possible for a substance to absorb visible light but still appear white?

texts: This is a UV-vis spectrum for zinc oxide


texts: How is the position of a peak on an IR spectrum determined?

texts:
In an IR spectrum, all sources describe the position of a peak as a range. The ranges seem to be defined arbitrarily.  Take, for example, the IR spectrum of ethanol (which I can't upload for some reason); why is the $\ce{O-H}$ stretch defined as having a range of $3200$ to $3750~\mathrm{cm}^{-1}$. If it was up to me, I would say that the trough goes from $3100$ to $3650~\mathrm{cm}^{-1}$. And if the $\ce{C-H}$ stretch wasn't present, I would say that the $\ce{O-H}$ trough extends to below $3100~\mathrm{cm}^{-1}$.

Moreover, sometimes there are very specific values given. These also seem to be arbitrarily defined. How do I determine the exact specific value that corresponds to a peak?

And finally, what is the correct way to identify the position of a trough on an IR spectrum? Is it a range? Or do I have to give a specific value?

P.S. I know I asked three questions, but they all serve the overall purpose to help me define how a trough is defined within an IR spectrum.


texts: Is there a readily available liquid that's more dense than water and insoluble?

texts: I am looking for any liquid that does not dissolve in water with higher density and does not react with water, one that is readily available.


texts: Is there any way to determine the spin of $\ce{[Fe(OH)6]^{4-}}$ without looking at the spectrochemical series?


texts: Can I make a container of (kind of) perpetually boiling water?

texts:
It's a common school experiment to make water boil at room temperature by putting it in a container and reducing pressure.

I am wondering if it is possible to make a sealed sphere containing water where the pressure is carefully set to room temperature so that it boils "forever".

Obviously it can't boil forever, because it would eventually all turn to vapor. What I am thinking though is that minor fluctuations in room temperature will cause it to cycle between boiling and condensation without the need for any power.

Is this line of thinking correct? Has anyone attempted to make something like this? I think it would be a really cool desk ornament, like a little box of cycling boil-condense water.


texts: How to re-suspend silver from the dried out silver paste?

texts: Kindly suggest any method or solvent to re suspend silver from old dried out silver paint/paste. It's a 25 years old "Dotite©" D-550 bottle. Strangely there is no expiry date mentioned on the bottle.


texts: Oxidation of alkenes by selenium dioxide to diketones

texts:
I know that $\ce{SeO2}$ readily affects the allylic position. The reaction mechanism of this reaction goes like this:

(Source: Wikipedia; License: Public Domain)

But, in my book, there's another reaction given as an exception:

Here, an $\alpha$-diketone is formed.

Why and how is this alternative product formed? What is the mechanism for this product?


texts: Coffee and orange juice concentrations with a twist

texts:
This question dates back to a time where I used to watch something called The Curiosity Show... Kinda like Bill Nye the Science Guy's show. I just can't recall the answer to this so I'm hoping that someone could shed some light.

I have two glasses of equal size and volume, with equivalent volumes of orange juice and coffee, one beverage in each glass.

Given that I have a hypothetical non-stick, hydrophobic teaspoon on me, if I was to get my teaspoon and take a level teaspoon of coffee out of the coffee glass and put it in the glass of orange juice, give it a stir, and then get a level teaspoon of this orange juice plus coffee mix and put this teaspoon of liquid in the coffee glass and give it a stir... Do I now:

have more orange juice in the coffee glass than coffee in the orange juice glass;
have more coffee in the orange juice glass than orange juice in the coffee glass; or
have equal amounts of coffee in the orange juice glass and orange juice in the coffee glass?


texts: nucleophilic attack in Acid chloride formation

texts:
First mechanism is the one taught in lecture, and I wondered why the electrons from carbonyl Oxygen wouldn't react with thionyl chloride.
So I tried to draw a second mechanism as much as I could but it won't produce the same product.

So my question is:

Is nucleophilic attack from carbonyl Oxygen less likely. If so, why?
If not, where did I go wrong?


texts: How to find the angle of emission of an X-ray during impact of accelerated cathode rays?

texts:
X rays are produced when accelerated cathode rays strike a metal target or a metal anode.
How can we find the angle at which the X-ray is emitted from the metal anode or the target when the cathode ray strikes the metal perpendicular to the surface?
Does anyone know how?


texts: Only one unique adiabatic path between two states

texts:
My Textbook says:

Two states A and B can never lie both on a reversible as will as irreversible adiabatic path. There lies only one unique adiabatic path linkage between two states A and B.

I don't understand what the book means. Why cannot there be both reversible and irreversible adiabatic paths between two states? And if only one path is possible, then how do we know which one?
What I understood is: In adiabatic process: ΔU=W. Now since ΔU is state function, it will mean that Wirreversible=Wreversible, which is not possible. But mathematical proof aside, is there any example/physical explanation to this?


texts: Making carbon monoxide gas from formic acid and sulfuric acid?

texts: Can I create carbon monoxide gas by just mixing formic acid and sulphuric acid together? Or do they have to be heated?


texts: Why do some ions form tetrahedral complexes more readily than others?

texts: Why does Co$^{2+}$ readily form tetrahedral complexes such as [CoCl$_4$]$^{2-}$, whereas Fe$^{2+}$ usually forms octahedral complexes?


texts: Magnetically separating H2 and O2 in a volume of gas

texts:
I'm using a method of electrolysis where the anode and cathode are in close proximity (~0.7mm) and therefore the separate collection of H2 from the cathode is very difficult. Since O2 is paramagnetic and H2 is diamagnetic I was thinking I could use permanent magnets to separate the gases in a specially constructed bubbler.

Is it possible to calculate the required magnetic field strength necessary to perform this separation? If so, can you provide a formula or point me in the right direction where I can read about how to calculate this?


texts: Write a Net Ionic Equation to Represent the Reaction of Aqueous Ammonia with Propionic acid

texts:
I would like to know how do I begin to solve a problem like this?

That is finding the formula equation?

I would assume that it would be
$$ \ce{NH3 + CH3CH2COOH -> NH3 + CH3CH2COOH + H2O} $$

I am really confused as to how I can balance this equation. Do I give the ammonia a hydrogen? Do I break up the acid into smaller units?

From there I would like to know the best way for me to switch the equation into an ionic equation and then finally a net ionic equation.

By the way the net ionic equation is
$$ \ce{CaCO3 (s) + 2HC2H3O2+ (aq) -> CO2 (g) + H2O (l) + Ca^2+ (aq) + 2C2H3O2^- (aq) } $$

I am just clueless as to how they got there.


texts: DNA pairs (adenine-thymine, guanine-cytosine)

texts:
Well I was wondering why adenine pairs with thymine and cytosine pairs with guanine.

From those pictures:

Thymine has the lowest acidity and adenine has the biggest acidity.

So it is logical that the intermolecular bond will be strong.

Adenine and Cytosine have pretty much the same acidity so why is it energetically favorable for guanine to make an intermolecular bond with cytosine?

Is it due to the three combinations this (adenine-thymine, cytosine, guanine) has the lowest energy?


texts: Increase in bond length of BF₄⁻ compared to BF₃

texts: Why does $\ce{BF4^-}$ have a larger bond length than $\ce{BF3}?$ Usually in molecules the bond angle increases to reduce repulsion but, here the bond length increases. Why is it so? Does the bond length increase with the bond angle in other cases of such kinds of molecules?


texts: Determine the rate law for the given reaction

texts:
I was studying for a PhD entrance exam and this question made me wonder about some topics in kinetics:
Consider the multi-step reaction below:
$\ce{A_2 → 2 A}$
$\ce{2A + X → Y + B}$
$\ce{B → A2 + Z}$
Which one can't be determined from the given equations:
a) The general balanced equation
False, just by adding the reactions, we have $\ce{X -> Y + Z}$
b) The identity of the catalyst
False, A2 is the catalyst: consumed in the first step and reformed in the last
c) If an intermediate is formed
False, B is an intermediate
d) The rate law for this reaction
e) None of the above
It is not stated which step is the rate-determining step.
However, since $\ce{A_2}$ is a catalyst, its decomposition can't be the slow step (it doesn't make sense to have a catalyst that slows the reaction).
The second step is termolecular and forms an intermediate, which makes it a strong candidate for rate-determining step.
B is the decomposition of an intermediate, which should be fast considering that intermediates in reactions are usually unstable species that are quickly consumed.
My main question is: can we determine the rate law for the reaction with the given information?
Secondary questions, which could be added as separate questions, would be:

Can the decomposition of a catalyst be the slow step?
Is the formation of an intermediate always slower than its consumption? In other words, are there examples that don't follow the Steady State Approximation (considering simple chemical reactions only, not enzyme-catalyzed)?


texts:
Background:
I can see a difference in stereoselective and stereospecific reactions in organic chemistry. However, both terms are used interchangeably as synonyms in a biochemistry class.

Question:
What differs selectivity from specificity in enzymatic reactions. What is meant when we talk about enzyme specificity and enzyme selectivity?


texts: What causes the difference in heat energy released by combustion for the butanol isomers?

texts:
I am currently working on an investigation where I am burning isomers of butanol to test for the heat of combustion values to see which fuel is most efficient. The fuels I am testing are 1-butanol, 2-butanol, 2-methylpropan-1-ol (isobutanol) and 2-methylpopan-2-ol (tert-butyl alcohol).

I have researched that the heat of combustion values for these fuels are as follows:

1-butanol: −2671 kJ/mol
2-butanol: −2661.1 kJ/mol
Isobutanol: −2662.6 kJ/mol
Tert-butyl alcohol: −2644.8 kJ/mol

So evidently, my experimental results should also show similarity in the ordering of greatest to lowest heat of combustion values.

However, I am wondering why isomers of butanol have different heat of combustions. I know it has to do with the shape of the molecules and whatnot, but how does this affect the energy released? What about bond angles?


texts: Can the enthalpy change of a reaction be changed, and if so, will this affect the value of the equilibrium constant?

texts:
In the case of an arbitrary equilibrium reaction, is it possible to change the absolute enthalpy of the final products, thus the reaction enthalpy change? For example, say pH affects the charge distribution of the product molecule, changing the attractive force between it and the solvent (feel free to come up with a better example).

Given that this does in fact affect $\Delta H$, would the Gibbs free energy change of the reaction $\Delta G=\Delta H-T\Delta S$ be altered as well, or does the entropy change somehow adjust automatically?

If $\Delta G$, changes, I would assume $K$ changes as well through $\Delta G = - RT$ $\mathrm{ln} K$


texts:
I am studying some electrical components and particularly Raspberry Pi 2 official cases. Their manufacturer says that they consists of ABS (Acrylonitrile butadiene styrene) when I ask if their components are inflammable.
This answer proposes me that their components are inflammable.

Wikipedia about ABS

  Generally ABS would have useful characteristics within a temperature range from −20 to 80 °C

I think I can say little about the inflammability without extra pieces of information about their ABS.

How can you estimate how inflammable some ABS is?


texts: Is the Hartree-Fock procedure the same thing as the self-consistent-field (SCF) theory?

texts: Is it right to think that the Hartree procedure is called the SCF theory, as the notion of self-consistent field comes from approximating multi-electron wavefunction as multiple one-electron wavefunctions. Since we don't know the final charge density, we must iterate until it is self-consistent?


texts: What is the geometry of a tri-substituted methyl free radical?

texts:
My teacher explained that free radicals could have a geometry that is planar or pyramidal(tending to tetrahedral) based on whether or not it is substituted by lone-pair containing atoms.
For example,
$\ce{(CH3)_3C}$ would exhibit sp2 hybrid geometry of planar.
But when tri-substituted with Flourine/Chlorine, it will exhibit a geometry that is tending towards tetrahedral(pyramidal) because the free radical electron in the P-orbital repels the lone-pairs on the Halogen.
It does not seem convincing because, the P-orbital is above and below the plane, then why does the electron in P-orbital repel the groups into a geometry tending towards tetrahedral?
That's like as if the electron was present only on the top and was repelling the groups down.
Here is a picture that might help visualise the p-orbital above and below the plane: https://www.google.com/imgres?imgurl=https://chemistryonline.guru/wp-content/uploads/2016/09/carbonium-1280x720.jpg&imgrefurl=https://chemistryonline.guru/carbonium-ion/&tbnid=1bNjv-81SP8QxM&vet=1&docid=MPke176Wg2AS2M&w=1280&h=720&source=sh/x/im


texts: Why don't trigonal S and P compounds undergo inversion at room temperature?

texts:
Most molecules containing nitrogen atoms in trigonal pyramid configuration undergo a relatively fast process of inversion at room temperature. On the other hand, the free energy barrier for phosphines, sulfoniums and sulfoxides are high enough that they are optically stable: the rate of racemization is slow at room temperature.

I wonder what effect is responsible for this difference in behaviour (the larger energy barrier). I expect that it has to do with the size of the central atom (N being one row higher than P and S), but is that all there is to it? And how does size impact the free energy barrier for the inversion: energetically or entropically (or both, of course)?


texts:
Let me ask a question about the differentiation of Non-Adiabatic Couplings (NACs), specifically the terms $D_{IJ}$ and $d_{ij}$.

According to the Pyxaid paper, the set of $D_{IJ}$ computed via Slater Determinant (SD) basis are equal to the set of $d_{ij}$ from a one-electron orbital basis; so $D_{IJ}$ is computed numerically by differentiating $d_{ij}$. According to Libra-X, however, $D_{IJ}$ is directly differentiated. $D_{IJ}$ in the latter case seems less precise than that in the former because $D_{IJ}$ = $d_{ij}$ * (non-unity couplings of one electron orbital basis).

How important is the difference?


texts: Trying to duplicate a trumpet cleaning solution that isn’t available on the market

texts: There is a product called “Herco Spitballs” which are small foam cylinders soaked in solution which are used to clean brass wind instruments like trumpets.  The “Spitball” is inserted into one end of the horn and then blown through the entire instrument.  The solution runs out long before the spitballs do, but the solution is not available.  I’ve written to the manufacturer and haven’t gotten a response.  The solution is .5% Amine Polyglycol Condensate, .5% Isopropyl Alcohol, and 99% inert ingredients (probably water).  I need to know what Amine Polyglycol Condensate is and where to get it.  I don’t need much.  8 ounces would last for years.  Can you help me to find some?


texts: Why does the energy required to break a bond decrease as the number of bonds increase?

texts:
I noticed that the energy to break a single C bond is $348\ \mathrm{kJ}$, to break a double C bond would be $612\ \mathrm{kJ}$, and to break a triple C bond would be $837\ \mathrm{kJ}$. How come the energy required per bond breakage decreases as the number of bonds decrease?
It seems that for double bonds, the energy required to break a bond is $(612/2) = 306\ \mathrm{kJ}$. Why is this so?

Thank you.


texts: Reaction of phosphonates with conjugated carbonyl compounds

texts: I was wondering whether the phosphonate ion would do a Michael addition on to the double bond rather than attacking the $\ce{C=O}$ bond to form the alkene product as it usually does (e.g. in a Horner–Wadsworth–Emmons reaction).


texts: How to calculate concentration of unknown saturated stock solution from diluted solution whose concentration is known?

texts:
I want to measure the solubility of a compound. I prepared a saturated stock solution of my compound in 100ml of water by dissolving it in excess and filtering out the undissolved sample.

Then I took 1ml of saturated solution, diluted it to 10ml and measured the absorbance on a UV spectrophotometer. After that I calculated the concentration of diluted solution by plotting a calibration curve of various solutions of known concentrations.

Now how can I calculate the concentration of my saturated stock solution from diluted one?

The concentration of diluted solution is 17ppm/10ml.


texts: What zeolite types are typically used to absorb CO and CO2 gases at maximum zeolite absorption temperature?

texts: Me and my friends are doing a project involving carbon monoxide and carbon dioxide as products to be filtered, we are using zeolites and would like to know the zeolite type typically used to filter $\ce{CO}$ and $\ce{CO2}.$


texts:
"diamond structure. Every carbon atom is bonded
to four other carbon atoms forming a three-dimensional lattice of chair conformations."

SENTENCE FROM A BOOK

What does this mean?
Where I am struck is that I knew carbons occupy zinc blende like lattice so, how can this line be true.


texts: Base/acid reaction -> alcohol amphoteric? why no pkb value?

texts:
I have a question concerning acid/base reactions. Is it true that an alcohol is a better base than water?
My Professor listed the basicity (because we talked about E1/E2 and Sn1/Sn2 reactions) of the following compounds the following way: RO- > OH- > ROH > H2O (with stronger base being the RO- and the weakest here H2O). I would like to understand that with respect to pka/pkb values...
Now I came across the following problem:
Bronstedt Bases/Acids are determined by their equilibrium constant in WATER (pka/pkb). Alcohols (like ethanol have a pka about 16-19), water has a pks of 14, which makes alcohol a base by definition.

if that happens -> ROH + H2O -> ROH2(+) + OH(-), wouldn't you calculate the pkb for ROH and the pks for ROH2+? The alcohol is the base here? Unfortunately I haven't found any pkb value for ROH on the internet... (I don't mean the conjugated base of ROH!) - alcohols are even considered amphoteric? how is that possible? why do I only find pka (and no pkb) values then, like for ammonia?
Ammonia is considered amphoteric and has a pka and a pkb value. But if these equilibrium constants are determined in water, how can it have a pka value, if it only acts as a base there? Shouldn't be water the only molecule that can be considered amphoteric in water?
If we would say molecules like H2O and NH3 can "generally" donate a proton or take up a proton and because of that are considered amphoteric, aren't there many more molecules than can take up and donate a proton when a strong acid/base is present? wouldn't there be many more amphoteric molecules?

So I'm really trying to understand why if alcohols can act as base AND as acid, why there are not two values for that (like for water (pka and pkb=14) and ammonia (pka=23 and pkb= 4,75), even though that would require two different reactions in alcohols too:
ROH -> ROH2(+)
ROH -> RO(-)
I hope I haven't confused you too much and explained my problem at least somewhat clearly. :)


texts: What characterises the smell of alkane hydrocarbons?

texts: I have heard that aromatic hydrocarbons smell fruity and like petrol. However, I understand that there is a class of hydrocarbons called alkane, as for example propane or butane. I wondered if I might identify them by smell or sight in the same way as aromatic hydrocarbons. If so, what would characterise them?


texts: what's the mass of the original sample (g)?

texts:
here is a question that i don't know how it is solved :

A sample that is 75 % chloride by mass is dissolved in water and treated with an excess of AgNO3. If the mass of the AgCl precipitate that forms is 2.013 g, what was the mass of the original sample?

I hope you give me the the proper way of solving it


texts:
When wine is exposed to oxygen, acetic acid forms because of an oxidation reaction.

The wine then loses acetic acid. Why? Is it because it is oxidised itself to form carbon dioxide?


texts: Why do double bonds cause kinks in fatty acid chains?

texts:
Fatty acids can either be saturated or unsaturated. If they are saturated, they stack easily and form solids at room temperature. If they are unsaturated, however, double bonds are introduced, and these double bonds introduce kinks into the structure of the fatty acid molecule. In a different question on this site, it was suggested that the reason why double bonds cause kinks to form is that they interrupt the zig zag shape of the molecule.

However, what was left unexplained is how double bonds interrupt the zig zag shape. If we were dealing with a cis fatty acid, and both hydrogens were located on top, why would this lead to a kink?


texts: How to determine the total pressure of a gaseous mixture of xenon tetrafluoride and hydrogen?

texts:
Gaseous xenon tetrafluoride at partial pressure of $\pu{2 kPa}$ and hydrogen at partial pressure of $\pu{10 kPa}$, are exploded in an enclosed container producing xenon and hydrogen fluoride:
  $$\ce{XeF4 (g) + 2 H2 (g) -> Xe (g) + 4 HF (g)}$$
  Find out the total pressure of mixture of gases in the enclosed container.

Assuming $T$ and $V$ are constant, we can assume that the pressure is directly related to the amount of substance, hence $\pu{1 kPa}$ of $\ce{XeF4}$ reacts with $\pu{2 kPa}$ of $\ce{H2}$.

This means that only $\pu{4 kPa}$ of $\ce{H2}$ is needed to react with $\pu{2 kPa}$ of $\ce{XeF4}$.

Now, to find total pressure of mixture of gases I did

$$p = \pu{2 kPa}~\text{(from Xe)} + \pu{8 kPa}~\text{(from HF)} = \pu{10 kPa}$$

Why is this wrong? Why must I add $\pu{10 kPa}$ by $\pu{6 kPa}$ which is the unreacted hydrogen?


texts: Why is cell constant value measured through indirect methods (like using a solution whose conductivity is already known)? Isn't it easier to  measure the length and area of cross section of a conductivity cell directly?


texts: Is a low specific heat capacity for the material of the calorimeter good or bad?

texts: I wish to ask if a low specific heat capacity of the material of the calorimeter means that the calorimeter would be more exact as it takes less heat for the material to reach equilibrium. I thought it would make more sense if it was the opposite and that you would want a substance with a higher specific heat capacity.


texts: What is the benefit of using a pH indicator reagent over pH strips or a meter?

texts:
I've recently started getting into chemistry a bit as a hobby. Nothing serious, just amateur level stuff mostly, primarily just to educate myself.

Whenever I need to determine the pH level of a solution, I typically use either a pH meter I have, or sometimes the pH test strips. And while I do have a "universal indicator" solution, I've never used it before. Mainly because it seems to me that adding an additional chemical to the solution you're working with just to determine the pH seems a bit counter intuitive to me.

A couple of reasons I can think of off the top of my head:

Even if the indicator seems somewhat benign, you've now added some extra volume that isn't essential to the reaction or solution.
Some pH indicators use chemicals that are somewhat hazardous or carcinogenic.

Any time I've seen someone use a pH indicator reagent, it's always been in some type of demonstration of a reaction, where the yield or result of the reaction is just discarded in the end. This gives me the impression that pH indicator reagents are useful for neat chemistry tricks (like here, where the chemist uses bromophenol blue to demo dichromatism), but not so much for instances where one plans on utilizing the resulting solution for any reason.

Thanks in advance for any input!


texts:
How do I synthesize 3-phenyloxirane-2-carbaldehyde from chloroacetonitrile?

My proposed route involves:

hydrolysis of the nitrile to form a carboxylic acid, and subsequent esterification
then, a Darzens reaction with benzaldehyde
reduction of the ester function with DIBALH and oxidation to an aldehyde with $\ce{H2CrO4}$.

Is there a better method?


texts:
Carbon monoxide ($\ce{CO}$) is considered to be a neutral oxide, not acidic or basic. But why? It reacts with hot concentrated sodium hydroxide solution to give a solution of sodium methanoate:

$$\ce{NaOH + CO -> HCOONa}$$

Doesn't the reaction of carbon monoxide with the basic hydroxide ion show that it must be acidic?


texts: Acidities of (dimethylamino)acetophenone and (diphenylamino)acetophenone

texts:
How would you compare the acidities of these two compounds?

The deprotonation is obviously alpha to the carbonyl/amine. I think that the diphenyl substituent will be more electron withdrawing than the di methyl, just because the lone pair of nitrogen will have conjugation with the benzene rings, vs methyl groups electron donating onto N.


texts: Why Heating turns Amorphous to Crystalline and How?

texts:
I found this answer here but iam still confused:
"Polymer chains are entangled and frozen in an amorphous state. The role of heating is to liberate these entangled chains, so some parts of chains are arranged in regular order, these regions are called crystalline regions. In between these ordered regions chains are randomly oriented."

But these regularly ordered portions are already found in amorphous solids in scattered form in between of which the arrangement is disordered. That's why they are defined as having SHORT RANGE ORDER..

Now what special happen when we heat them that they turn into Crystalline solid....


texts: What is the pKa of 2-methyl-2,4-pentanediol? Is there a reference that contains a list of pKa values for various molecules that I can consult or is there a way to determine/estimate the pKa of this molecule if such a reference does not exist?


texts: How to know when electrons will be added onto Lewis Structure from surrounding atoms to become ion?

texts: How do I know when I should add an electron to a single electron? Do I just always do this? I've came across this in the textbook in the form of the amide ion $\ce{NH2}$, among others. It was shown to have 8 electrons, despite nitrogen only having 5 valence electrons, and each hydrogen only having 1. The last came from some surrounding atom to complete the outer shell and thus become more stable. So, do I always do that when there is a single electron not part of a pair?


texts:
I want to create a thin film of elemental sulfur. Based on significant searching, I can find that elemental sulfur deposition is a significant problem in oil and gas. However, I cannot find any specifications for depositing elemental sulfur via CVD, ALD, or other methods.

Can anyone suggest a method for creating a thin film of elemental sulfur? Thanks!


texts:
If they give bromine water test, what do they form?

I think that aldehydes will get oxidised and so decolourise bromine water but I don't know if that happens in normal conditions.


texts:
What is the $\text{p}K_\text{a}$ of water? A simple google search yields the value $15.74$, but this site and this paper say it's $14.0$.

According to my understanding, the correct answer should be $14.0$:

$$\text{p}K_{\text{a}}= -\log([\ce{H+}][\ce{OH-}])$$

For $25~\text{°C}$:
$$[\ce{H+}][\ce{OH-}] = 10^{-14} = K_{\text{w}}$$

Thus follows $\text{p}K_{\text{a}}=14$.

Can you tell me which value is correct and why?


texts: Does "silica colloidal anhydrous" contain aluminium?

texts: Some silicas such as sodium aluminosilicate contain aluminium. Is silica colloidal anhydrous one of these substances?


texts:
So I've read that during the formation of the Grignard reagent, The R-X bond cleaves homolytically forming free radicals.
My question is how is this happeneing? Due to the high electronegativity difference between Carbon and Halide group shouldn't it result in R+ and X- ?
To be clear, I have no problem following through how the electrons move around. My only doubt is how exactly the Alkyl-Halide bond resulted in a free radical instead of an ion.


texts: I want to qualitatively test for the presence of oxygen within argon gas. I would like the test to be positive if approx $1\%$ or more is oxygen, but definitely negative if less than $0.1\%$. Anywhere in between is fine—A quantitative test is a bonus. I was thinking of heating iron filings in the gas to deduce it. I'm not sure what apparatus and setup  I would need since heating gas expands, I would like to use ultra low tech equipment. I'm thinking of using water or cooking oil displacement to hold the extra gas, but I don't know if argon would dissolve, or how much oxygen would dissolve. Preferably a nonflammable, certainly nontoxic liquids (or tests).


texts: Can a molecular sieve be used increase the saturation of a fructose solution?

texts:
The Problem: Let's say we have an experiment where we are attempting to grow rock candy crystals by letting a solution of sugar crystalize on a wooden dowel. However, an error may have been made in that there was too little sugar added for the volume of water to reach saturation and thereby grow the crystals. The solution is to remove some of the water so that the solution becomes saturated.

But that's a problem.

The experimental setup is in an environment were letting it evaporate away is not allowed. It cannot be moved outside or really leave the lab it's in at all. Our access to the setup is very limited and getting resources to it is a logistical and financial nightmare. The test setup may as well be in space. The test apparatus is also not very conducive to modification in that we can't modify it at all and the only access to the solution is through a 3 mm inner dia tube. Repeating the experiment is out of the question because of a whole host of constraints, again assume it's in space.

So my question is, can we send up a molecular sieve to be inserted into the container to absorb some of the water and cause the sugar to reach saturation and thereby start to crystalize? If not, is there something else that can be done to the solution?

Other suggestions must be as harmless as possible. They should also not cause a pressure increase in the container, nor interfere with the growth of the sugar crystals. Any form of density separation will not work.


texts: Difference between neutral and basic activated alumina

texts:
Sigma Aldrich sells two different types of activated alumina for column chromatography: neutral and basic.

Apparently basic alumina is more active and better at adsorbing anions.

Why is this the case?


texts: Why heat of reaction under neither constant pressure or constant volume is considered (in my textbook, or probably somewhere else)?

texts:
So my textbook gives me this random equation:
 $\Delta U = q + w$. Then consider two conditions, under constant pressure and under constant volume. Because $w = -P\Delta V$, constant volume will make $\Delta U = q$. And constant pressure equation is basically the same.

But why is isn't heat under neither condition considered? Because it is of significance?


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What are the steps in calculating the photosynthetic rate ($\pu{\mu mole}~ \ce{O2} \pu{m2/ min}$) for a leaf that has an area of $\pu{0.0025 m2}$ and a $\ce{O2}$ evolution
rate of $0.096~\ce{O2}/\pu{min}$?

To do so , the first step is to convert it to $\mu L$ i.e. $\pu{960 \mu L} ~\ce{O2}/\pu{min}$.
The second step should be to convert it to $\pu{\mu moles}$. So, how do we do that ?
EDIT : In my textbook, the following calculation has been done but I am not able to understand it...

$\pu{960 \mu L}~\ce{O2}~\pu{/L} / [(273+23)/273) \times 22.423]$

I know that $22.423$ is the volume of a mole of gas and $\pu{273K}$ is $\pu{0^\circ C}$ but I am not able to understand how that fits here.


texts: Food-grade antifungal preservatives for alcohol-containing aqueous non-food product that won't UV-yellow when dried?

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I need a broad-spectrum antifungal (yeast and mold) agent for an aqueous non-food product (pH $\simeq$ 6) that contains 20% v/v alcohol (ethanol or isopropanol).  A key requirement is that it not UV-yellow if it comes into contact with textiles (e.g., clothing) after drying.
I would prefer it to be a food-grade preservative—or, barring that, something not on the California Prop. 65 list.    What preservative (or combination of preservatives) would work, and at what concentration should I use them?
Sodium benzoate and potassium sorbate can be effective anti-fungal agents when used in combination.  However, these would not work here, since they don't have significant antimicrobial activity at pH $\simeq$ 6.  In addition, potassium sorbate is known to yellow (at least in solution) when exposed to UV; and since sodium benzoate is aromatic, it might UV-yellow as well.
I've contacted both Sigma and Lonza (which has a specialist preservative division).  Sigma said they can't make a recommendation at that level of detail, and Lonza said they would need to send me to their business office to set up a research contract for that.


texts: Prensense of Hydroxide Ions in Chemical Reaction in a Basic Medium

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I was studying NCERT book of chemistry about chemical properties of hydrogen peroxide. First there is a chemical equation under a subtopic named 'Oxidising action in acidic medium' which is...

$$\ce{2Fe^{2+} + 2H^+ + H_2O_2 \rightarrow 2Fe^{3+} + 2H_2O}$$

Note here that there are hydrogen ions in the reactant side because it is in acidic medium.

Then another subtopic named 'Oxidising action in basic medium' has reaction

$$\ce{2Fe^{2+} + H_2O_2 \rightarrow 2Fe^{3+} + 2OH^-}$$

Now in this equation there is no hydroxide ions as it should be because it is basic medium.

I am not asking about its oxidizing and reducing properties or how it works. I know that oxygen atom of $\ce{H_2O_2}$ has $-1$ oxidation state. I am just asking why isn't there any hydroxide ion in the reactants.

Sorry if it is foolish doubt. Thanks in advance.


texts: For example, mercury (I) is $\ce{Hg2^2+}$ and not $\ce{Hg+}$. What causes  the stability in covalently bonded $\ce{Hg}$ ions?


texts: IUPAC nomenclature of molecules containing alkoxide and carboxylate groups

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I am studying for my A levels and recently came across the above-mentioned reaction.

I tried to think up a name like disodium 4-oxidebutanoate, but this is not based on any IUPAC rule. Internet searches have revealed no name for this, at least to me.

This compound is both an alkoxide ion and an alkanoate ion. How are such compounds named?


texts: Products formed on cleavage of epoxides using HI

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There seems to be multiple forms of $\ce{HI}$ used to cleave epoxides:
conc. $\ce{HI}$, anhydrous $\ce{HI}$, cold $\ce{HI}$, hot $\ce{HI}$, cold conc. $\ce{HI}$, hot conc. $\ce{HI}$, etc.
So, does concentration of $\ce{HI}$ and temperature have any significance in determining the product?