instruction stringlengths 15 21.8k |
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> Argon $(\ce{Ar})$ and helium $(\ce{He})$ are initially in separate compartments of a container at $\pu{25 °C}.$ The $\ce{Ar}$ in compartment **A** which has a volume $V_\ce{A}$ of $\pu{9.00 L}$ and a pressure of $\pu{2.00 bar}.$ The $\ce{He}$ in compartment **B** of unknown volume $V_\ce{B}$ has a pressure of $\pu{6.... |
I am interested in making a Schlieren texture of liquid crystals to show kids at an outreach event (see image below). I have the polarizers and camera for a the imaging part, but I don't know of a place to find cheap and chemically inert liquid crystals (don't want to bring anything sensitive or hazardous). I would ima... |
Liquid crystals for academic outreach? |
Is there any publicly available software that can do deterministic CCSDTQP other than MRCC? |
I am interested in making a Schlieren texture of liquid crystals to show kids at an outreach event (see image below). I have the polarizers and camera for the imaging part, but I don't know of a place to find liquid crystals.
I would prefer something cheap and chemically inert because I don't want to bring anything ... |
In this case the anode for electroplating would be the Lithium and the cathode would be any conductive metal.
Unfortunately Lithium reacts violently with water, which is the basis of most electrolyte solutions that are used for electroplating.
So is there an anhydrous electrolyte solution or an alternative method... |
How does one electroplate Lithium onto a conductive metal? |
In this case the anode for electroplating would be the Lithium and the cathode would be any conductive metal.
Unfortunately Lithium reacts violently with water, which is the basis of most electrolyte solutions that are used for electroplating.
So is there an anhydrous electrolyte solution or an alternative method... |
According to https://chemistry.stackexchange.com/questions/26315/what-is-the-temperature-of-heat-generated-from-lpg-gas, the temperature of **(1) LPG gas is above 1700 degree Celsius**.
Many of us are familiar with pan-frying meat (steak, pan-frying the chicken breast etc).
Next, consider this: when you're **(2) ... |
If LPG gas burners can reach temperatures above 1700 °C, then how do HCA and PAH not develop in extreme amounts during cooking? |
The correlation energy of a system is defined as the difference between the exactly energy and the energy in the Hartree-Fock method: $E_{cor} = E - E_{HF}$. In the case of an atom or a molecule, is it possible say that $E_{cor} < 0$, since the interaction between the electrons is positive? |
The correlation eenrgy of a system is always negative? |
The correlation energy of a system is defined as the difference between the exactly energy and the energy in the Hartree-Fock method: $E_\mathrm{cor} = E - E_\mathrm{HF}$. In the case of an atom or a molecule, is it possible say that $E_\mathrm{cor} < 0$, since the interaction between the electrons is positive? |
Is the correlation energy of a system always negative? |
Can anybody help me out with this chain conversion? |
My first language is not English, so there might be some parts where it's hard to read. Sorry in advance.
----------
I have some questions regarding the derivation of the equilibrium constant and the rate-determining step.
For a hypothetical reaction
$$\ce{aA + bB <=> cC + dD}$$
the equilibrium constant ... |
The effects of $\ce {-CH3}$ and $\ce {-CCl3}$ substituents on the product distribution of an electrophilic aromatic substitution reaction are unambiguous. The $\ce {-CH3}$ group exhibits a clear electron-donating effect and directs electrophiles to the 2- and 4- positions. Similarly, the $\ce {-CCl3}$ group exhibits a ... |
I was reading up on manufacture of shellac based composites when I encountered the following statement (in ref. 1):
> Wood flour and fibres are interesting because of their low cost, good specific strength, low density per unit volume [...]
Is that a typo or other error or is "density per unit volume" a ... |
Is "density per unit volume" something? |
> The selective nitration of benzyl chloride and its application in the synthesis of 4-nitrobenzaldehyde were studied. Nitration of benzyl chloride with HNO3 in the presence of Nb2O5(6% weight percent) at 0～5℃ for 1.5 hours gave mononitro products in 94% yield with 77～80% para selectivty. Nb2O5 was recovered by filtrat... |
The following is the abstract of K.M. Zhang "Selective Nitration Of Benzyl Chloride And Its Application In The Synthesis Of Nitrobenzaldehyde"([link][1]). The full pdf is behind paywall.
> The selective nitration of benzyl chloride and its application in the synthesis of 4-nitrobenzaldehyde were studied. Nitration o... |
Since glass is a mix of silicates of Na and Ca produced by heating or fusing together Na2O which act as Lewis bases with Sand or SiO2 (Lewis Acid) Since Na2O/NaOH(aq.) is strong base and is used to create water glass(es){Na2SiO3, NaxSiOy etc.}. Is there some procedure in place to create glass by mixing (a base rich) wa... |
Cold process to make glass? |
Protic solvents can form a tight shell around a nucleophile. But what's stopping any polar solvent from doing so? Shouldn't a polar solvent surround negatively charged $\ce{F-}$ with its partially positive side? |
I was reading articles on the preparation of shellac-based composites when I encountered the following statement (in ref. 1):
> Wood flour and fibres are interesting because of their low cost, good specific strength, low density per unit volume [...]
Is that a typo or other error or is "density per unit ... |
Is $\ce{SiO2}$ is a polar molecule or not?
The difference in electronegativity between the two atoms is 1.7.
I read that $\ce{SiO2}$ doesn't exist as a single molecule in which the silicon atom is connected to four oxygen atoms. Can I consider it polar? |
Is silicon dioxide a polar molecule or not? |
Is the following equation true?
$$\ce{∆_fH} = \ce{∆_{BE_{reactants}}H} - \ce{∆_{BE_{products}}H}$$
where $BE$ stands for Bond energy and $f$ stands for formation.
I read that,
$$\ce{∆_fH} = \ce{∆_{reactants}H} - \ce{∆_{products}H} = \ce{-∆_{BE}H}$$
But how is the first equation true?
> Is it because of this $... |
$H_2SO_4$ is a strong acid, which follows the reaction
$$H_2SO_4 \to HSO_4^-+H^+$$
Not
$$H_2SO_4 \to SO_4^{2-}+2H^+$$
However,
$$Ba(OH)_2 \to Ba^{2+}+2(OH)^-$$
Is there a reason why these "polyprotic analogs" in bases completely dissociate but polyprotic acids do not?
Note: This is in context to titratio... |
Why do strong polyprotic acids not dissociate completely, whereas strong bases with multiple (OH)- groups do? |
I was reading articles on the preparation of shellac-based composites when I encountered the following statement (in ref. 1):
> Wood flour and fibres are interesting because of their low cost, good specific strength, low density per unit volume, along with their renewable and degradable features. The dr... |
How can any separation/fractionation of isotopes be mass-independent, if the only difference between two isotopes is mass?
The only clue(s) on Wikipedia mention molecular symmetry, 'forbidden' spin-flip transitions/reactions and photochemical dissociation....
But how is any of that affected by an extra neutron? |
What is mass-independent isotope separation/fractionation? |
Here, "density per unit volume" implicitly indicates that the densities of the substances being compared have been normalized.
It is redundant but safe - it rules out the possibility of having compared the density of one pound of something with that of a kilogram of another, for example.
The authors probably sh... |
Are chlorinated solvents incompatible with reducing reagents? Is reductive dechlorination the reason?
There also seems to be exemptions, in *J. Org. Chem.* **1996**, 61, 3849-3862, 1,2-dichloroethane was used as a solvent for a reductive amination reaction. NaBH(OAc)<sub>3</sub> was used as the reducing agent in thi... |
Are chlorinated solvents generally avoided in reducing reactions? |
In most of the examples in my book I have come across, the electrolyte for an electrochemical half cell has always been the aqueous version of the metal used. For example, a silver electrode is immersed in a silver solution and so on, but is why is this necessary? Surely any positive metal ion will do? |
Here, "density per unit volume" implicitly indicates that the densities of the substances being compared have been normalized.
It is redundant but safe - it rules out the possibility of having compared the density of one pound of something with that of a kilogram of another, for example.
The authors probably sh... |
Here, "density per unit volume" implicitly indicates that the densities of the substances being compared have been normalized.
It is redundant but safe - it rules out the possibility of having compared the density of one pound of something with that of a kilogram of another, for example.
The authors probably sh... |
> For example, a silver electrode is immersed in a silver solution and so on, but is why is this necessary? Surely any positive metal ion will do?
There is a fundamental reason, which is the Nernst equation. It *requires* that the metal be in contact with its own ions. What is the functional meaning of the electrod... |
$\ce{H2SO4}$ is a strong acid, which follows the reaction
$$\ce{H2SO4 -> HSO4- + H+}$$
Not
$$\ce{H2SO4 -> SO4^2- + 2 H+}$$
However,
$$\ce{Ba(OH)2 -> Ba^2+ + 2OH-}$$
Is there a reason why these "polyprotic analogs" in bases completely dissociate but polyprotic acids do not?
Note: This is in context to tit... |
My first language is not English, so there might be some parts where it's hard to read. Sorry in advance.
----------
I have some questions regarding the derivation of the equilibrium constant and the rate-determining step.
For a hypothetical reaction
$$\ce{aA + bB <=> cC + dD}$$
the equilibrium constant ... |
I roast coffee, and currently package it in plastic bags with one way 'degassing' valves.
As soon as coffee is roasted, it starts giving off CO2, a process which continues for days, and sometimes weeks. The degassing valve allows the CO2 to escape the bag, while it prevents oxygen, which is the staling enemy of ... |
It is [said](https://en.wikipedia.org/wiki/Cyclobutadieneiron_tricarbonyl) that $\ce{(\eta^4-C4H4)Fe(CO)3}$ can undergo electrophilic substitution reactions. Therefore, it displays aromaticity.
For the iron atom, it has $8$ electrons in its outer shell initially and it receives $6$ electrons from three carbonyls. It... |
Why does cyclobutadieneiron tricarbonyl behave aromatically? |
I was trying to explain it in terms of reaction rates and such; more than just 'Le Chatelier's principle states ...', but I can't figure out the underlying reason as to why. I can explain why for increasing the pressure, temperature changes and such, but not for this specific one. If there is more space for the particl... |
Why does reducing the pressure in an equilibrium reaction favour the side with more moles of gas? |
I'm having a hard time making a distinction between simple and complex enzymes. the definitions I've found so far all say this:
> Simple enzymes are enzymes that are only made out of protein, and complex enzymes are ones that, in addition to the protein portion, have a non-protein portion as well, which is called a ... |
What is the definition of a "Simple enzyme" exactly? Is it an enzyme that does not require a co-factor? |
**So** I was doing a Gizmo for my Science class and I came across this question: "Why do phase changes occur?" I could not find anything about it in my resources. Does anybody here know the answer?
|
Why do phase changes occur? |
> Using reaction mechanism, why radical bromination of cyclohexene is faster than cyclohexane? Draw the stereochemistry of most stable product(s) of both cyclohexene and cyclohexane.
Here are what I get so far
1. I'm not sure about the kinetics of the reaction but I worry the kinetics vs thermodynamics factor (an... |
In general, is it true that if I connect an aqueous oxidant to an aqueous reductant via a wire, will a current flow along the wire? In particular, does current flow in the following scenario?
Imagine putting one end of a wire in hydrogen peroxide (a common oxidizer) and the other end inside water containing formic a... |
> is it true that if I connect an aqueous oxidant to an aqueous
> reductant via a wire, will a current flow along the wire? In
> particular, does current flow in the following scenario?
No true. Nothing will happen as the circuit is incomplete. The oxidant or the reductant species have to see each other "face to f... |
> For ethanol precipitations [...] shouldn't the water-phosphate attraction be increased in magnitude by the same ratio as that by which the phosphate-cation in increased in magnitude?
The interaction between negatively charged nucleic acid and positively charged counter ions is an ion:ion interaction. The interacti... |
I was trying to explain it in terms of reaction rates and such; more than just 'Le Chatelier's principle states ...', but I can't figure out the underlying reason as to why. I can explain why for increasing the pressure, temperature changes and such, but not for this specific one. If there is more space for the particl... |
> is it true that if I connect an aqueous oxidant to an aqueous
> reductant via a wire, will a current flow along the wire? In
> particular, does current flow in the following scenario?
No true. Nothing will happen as the circuit is incomplete. The oxidant or the reductant species have to see each other "face to f... |
I roast coffee, and currently package it in plastic bags with one way 'degassing' valves.
As soon as coffee is roasted, it starts giving off $\ce{CO2},$ a process which continues for days, and sometimes weeks. The degassing valve allows the $\ce{CO2}$ to escape the bag, while it prevents oxygen, which is the staling... |
In general, is it true that if I connect an aqueous oxidant to an aqueous reductant via a wire then a current flows along the wire? In particular, does current flow in the following scenario?
Imagine putting one end of a wire in hydrogen peroxide (a common oxidizer) and the other end inside water containing formic a... |
I don't know about other plastics, nor do I know about the scarcity of shellac records, but I do know shellac is a thermoplastic. Could you take an old record, melt it, and use a die to make your own record from that? This way, you could avoid having to deal with the recipe.
By the way, the following was found on Wi... |
I don't know about other plastics, nor do I know about the scarcity of shellac records, but I do know shellac is a thermoplastic. Could you take an old record, melt it, and use a die to make your own record from that? This way, you could avoid having to deal with the recipe.
By the way, the following was found on Wi... |
Consider a reversible reaction A converts to B and B converts to A with forward and backward rate constants Kf=Kb= 1sec raised to the power minus 1. Suppose we start with a 1 molar solution of A. How long will the concentration of A take to reach 0.75 molar? Here's what I have done: -
![enter image description here]... |
> Consider a reversible reaction $\ce{A}$ converts to $\ce{B}$ and $\ce{B}$ converts to $\ce{A}$ with forward and backward rate constants $k_\mathrm{fwd} = k_\mathrm{rev }= \pu{1 s-1}.$ Suppose we start with a 1 molar solution of $\ce{A}$. How long will the concentration of $\ce{A}$ take to reach 0.75 molar?
Here's ... |
In my home lab, I've reacted $\ce{Cu(OH)2}$ with aqueous ammonia to produce Schweizer's reagent. However, I'm surprised by the amount of ammonia required to react with this amount of $\ce{Cu(OH)2}$. Have I mistaken some calculation or formula?
**Background/procedures:**
8.89 g of copper (II) hydroxide was prepar... |
In the book "Concise Inorganic Chemistry" by Prof. JD Lee, it says here:
> These contributing structures do not actually exist. The Coj- does not
consist of a mixture of these structures, nor is there an equilibrium between
them. The true structure is somewhere in between and is called a
resonance hybrid. Resonan... |
I understand that when pH=kPa, the buffer solution will be at its maximum capacity, and there will be equal concentrations of the acid/conjugate acid and the base/conjugate base.
However, when pH>kPa, why is it that [A^-] > [HA], shouldn't it be the other what around since the Henderson-Hasselbalch equation is:
p... |
In this hydrocarbon there can be two main chain one with 2 double bond and one with a double and a triple bond
Both the main chain contains 6 carbon atoms.
Which will be considered correct and why?
|
In this hydrocarbon there can be two main chain one with 2 double bond and one with a double and a triple bond
Both the main chain contains 7 carbon atoms.
Which will be considered correct and why?
 |
In the book "Concise Inorganic Chemistry" by Prof. JD Lee, it says here:
> These contributing structures do not actually exist. The $\ce{CO3^2-}$ does not consist of a mixture of these structures, nor is there an equilibrium between them. The true structure is somewhere in between and is called a resonance hybrid. R... |
How does resonance fail in approximating chemical structures? |
I understand that when $\mathrm{pH}= \mathrm{p}k_\mathrm{a}$, the buffer solution will be at its maximum capacity, and there will be equal concentrations of the acid/conjugate acid and the base/conjugate base.
However, when pH>kPa, why is it that $\ce{[A^-] > [HA]}$, shouldn't it be the other what around since the H... |
I understand that when $\mathrm{pH}= \mathrm{p}K_\mathrm{a}$, the buffer solution will be at its maximum capacity, and there will be equal concentrations of the acid/conjugate acid and the base/conjugate base.
However, when $\mathrm{pH} > \mathrm{p}K_\mathrm{a}$, why is it that $\ce{[A^-] > [HA]}$? Shouldn't it be t... |
Where is my logic wrong?
An electron can only assume constant energies in an atom.
If an electron is localized in space in a hydrogen atom, its radius is known. If its radius is known, its electrostatic potential energy is known. Then, if the electron assumes quantized energies, its kinetic energies are quantized by ... |
Why the heisenberg uncertainty principle works in an atom? |
Where is my logic wrong?
An electron can only assume quantized energies in an atom.
If an electron is localized in space in a hydrogen atom, its radius is known. If its radius is known, its electrostatic potential energy is known. Then, if the electron assumes quantized energies, its kinetic energies are quantized by... |
Is the following equation true?
$$\ce{∆_fH} = \ce{∆_{BE_{reactants}}H} - \ce{∆_{BE_{products}}H}$$
where $BE$ stands for Bond energy and $f$ stands for formation.
I read that,
$$\ce{∆_fH} = \ce{∆_{products}H} - \ce{∆_{reactants}H} = \ce{-∆_{BE}H}$$
But how is the first equation true?
> Is it because of this $... |
In the given compound, there are (apparently) two possibilities of choosing the parent (main) chain for its nomenclature in accordance with IUPAC rules. (A) being the one containing 4 carbon atoms and the triple bond in the parent chain; (B) being the one containing 6 carbon atoms and the hydroxyl group as a substituen... |
[![enter image description here][1]][1]
In the given compound, there are (apparently) two possibilities of choosing the parent (main) chain for its nomenclature in accordance with IUPAC rules:
(A) being the one containing 4 carbon atoms and the triple bond in the parent chain;
(B) being the one containing 6 ca... |
Where is my logic wrong?
An electron can only assume quantized energies in an atom.
If an electron is localized in space in a hydrogen atom, its radius is known. If its radius is known, its electrostatic potential energy is known. Then, if the electron assumes quantized energies, its kinetic energies are quantize... |
Why does the Heisenberg uncertainty principle work in an atom? |
I've used the henderson hasselbalch equation to the solve this, considering imadazole group to be the acid HA. However the correct answer appears to be 10:1 uncharged to charged ratio. If I use HA^+ to be the acid the answer turns out correct. C... |
The pKa of the side chain imidazole group of histidine is 6.0. What is the ratio of uncharged to charged side chains at pH 7? |
> The $\mathrm{p}K_\mathrm{a}$ of the side chain imidazole group of histidine is $6.0.$ What is the ratio of uncharged to charged side chains at $\mathrm{pH}~7?$
Here's my attempt to the solution:
$$7 = 6 + \log\frac{[\ce{A-}]}{[\ce{HA}]}$$
$$1 = \log\frac{[\ce{A-}]}{[\ce{HA}]}$$
$$10[\ce{HA}] = [\ce{A-}]$$... |
> The $\mathrm{p}K_\mathrm{a}$ of the side chain imidazole group of histidine is $6.0.$ What is the ratio of uncharged to charged side chains at $\mathrm{pH}~7?$
Here's my attempt to the solution:
$$7 = 6 + \log\frac{[\ce{A-}]}{[\ce{HA}]}$$
$$1 = \log\frac{[\ce{A-}]}{[\ce{HA}]}$$
$$10[\ce{HA}] = [\ce{A-}]$$... |
[![enter image description here][1]][1]
In the given compound, there are (apparently) two possibilities of choosing the parent (main) chain for its nomenclature in accordance with IUPAC rules:
(A) being the one containing 4 carbon atoms and the triple bond in the parent chain;
(B) being the one containing 6 ca... |
[![enter image description here][1]][1]
In this hydrocarbon there can be two main chains: one with two double bonds and one with a double and a triple bond
Both main chains contain seven carbon atoms.
Which will be considered correct and why?
[1]: https://i.stack.imgur.com/jwswu.png |
I found a web article, "[The Origin & Many Uses of Shellac][1]" by R.J. Wakeman, to be particularly illuminating and well-written source of information on the composition and manufacture of shellac records, for instance it explains:
>Emile Berliner’s first disc records were pressed in celluloid (1894) followed by th... |
Last week there was a huge fire in french chemical factory Lubrizol, we now know the main products that burnt, to simplify the discussion I extracted a few compounds :
- [butyl polysulfide](https://patents.google.com/patent/US4839069) 500 tons,
- [dithiophosphoric acid and zinc salt](https://en.wikipedia.org/wi... |
Last week there was a huge fire in french chemical factory Lubrizol, we now know the main products that burnt, to simplify the discussion I extracted a few compounds :
- [butyl polysulfide](https://patents.google.com/patent/US4839069) 500 tons,
- [dithiophosphoric acid and zinc salt](https://en.wikipedia.org/wi... |
Last week there was a huge fire in french chemical factory Lubrizol, we now know the main products that burnt, to simplify the discussion I extracted a few compounds :
- [butyl polysulfide](https://patents.google.com/patent/US4839069) 500 tons,
- [dithiophosphoric acid and zinc salt](https://en.wikipedia.org/wi... |
Last week there was a huge fire in french chemical factory Lubrizol, we now know the main products that burnt, to simplify the discussion I extracted a few compounds :
- [butyl polysulfide](https://patents.google.com/patent/US4839069) 500 tons,
- [dithiophosphoric acid and zinc salt](https://en.wikipedia.org/wi... |
Methane is one of most cleaner of vehicle fuels when compared with other hydrocarbons. It can be easily and continuously produced in form of biogas in biodigestors working on farm and animal wastes. What are the reasons and/or roadblocks that are keeping us from un tapping and harnessing such fuel instead of going for ... |
More use of pentane(+hexane+..) when compared with methane? |
Like what the title says, my question is if a beta particle is just an electron, what causes it to be dangerous?
I understand that a beta particle is not only an electron but it is also one with a lot of energy.
I wish to understand what happens when this electron hits a living cell, the effects, and why it is ... |
If a beta particle is just an electron, what causes it to be radioactive/dangerous? |
Last week there was a huge fire in french chemical factory Lubrizol, we now know the main products that burnt, to simplify the discussion I extracted a few compounds :
- [isobutyl and isobutene polysulfide](https://patents.google.com/patent/US4839069) 500 tons,
- [dithiophosphoric acid and corresponding zinc sa... |
Last week there was a huge fire in french chemical factory Lubrizol, we now know the main products that burnt, to simplify the discussion I extracted a few compounds :
- [isobutyl and isobutene polysulfide](https://patents.google.com/patent/US4839069) 500 tons,
- [dithiophosphoric acid and corresponding zinc sa... |
I was just introduced to the concept of orbital hybridization. I believe I understand the idea behind it, but there is some accompanying terminology that prevents me from achieving a greater understanding.
In the following image:
[![enter image description here][1]][1]
I see that one of the electrons in the $... |
I was just introduced to the concept of orbital hybridization. I believe I understand the idea behind it, but there is some accompanying terminology that prevents me from achieving a greater understanding.
In the following image:
[![enter image description here][1]][1]
I see that one of the electrons in the $... |
I am going to prepare tert-butyl protected threonine. I was going for the classic esterification methodology which is acid catalyzed (sulfuric acid) esterification under reflux of tert butyl alcohol + threonine. My worry is that the -OH r group of threonine will also be esterified. My lab has very few reagents. We don'... |
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