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I used a soft silicone hose to carry ammonia at ~70C. I was surprised to later find the hose had hardened.
A quick materials compatibility search for silicone had given me a lot of info but an "I" (standing for "Insufficient Information") for ammonia. I wrongly assumed it would be ok.
What happened? What was pr... |
I used a soft silicone hose to carry ammonia at ~70 °C. I was surprised to later find the hose had hardened.
A quick materials compatibility search for silicone had given me a lot of info but an "I" (standing for "Insufficient Information") for ammonia. I wrongly assumed it would be OK.
What happened? What was pr... |
[![in this picture][1]][1], the question is to find which one is more acidic (and the answer is the III is more acidic than II ). My theory as to why it must be true is, lets consider II compound, we have an oxygen attached to the carbon forming a sigma and an _pi_ bond, and that oxygen has 2 filled **p** orbitals.
N... |
can we form pi bond like overlap when the atoms are not directly attached to each other? |
>[![in this picture][1]][1]
>Identify the more acidic compound (and the answer is the III is more acidic than II ).
My theory as to why it must be true is, let's consider II compound, we have oxygen attached to the carbon forming a sigma and a _pi_ bond, and that oxygen has 2 filled **p** orbitals.
Now the oxyg... |
Can we form pi bond like overlap when substituents in a compound are not directly connected? |
Are pi bond like like interactions possible when substituents in a compound are not directly connected? |
**I am currently working on noble gas configurations in chemistry and I am having a hard time understanding why I got two questions wrong on a practice.**
**The instructions for the practice are here:**
Write out the noble gas configuration for the element. Enter your answer with all values without any spaces, h... |
Can someone help me figure out what the noble gas configurations for zirconium and holmium are? |
**I am currently working on noble gas configurations in chemistry and I am having a hard time understanding why I got two questions wrong on a practice.**
**The instructions for the practice are here:**
Write out the noble gas configuration for the element. Enter your answer with all values without any spaces, h... |
**I am currently working on noble gas configurations in chemistry and I am having a hard time understanding why I got two questions wrong on a practice.**
**The instructions for the practice are here:**
Write out the noble gas configuration for the element. Enter your answer with all values without any spaces, h... |
[![enter image description here][1]][1]
I have trouble understanding as to what the last part of the increase in liquid level means. I believe this is the foam formed after the fermentation? I am calculating for the pressure but I have trouble as to what volume should I use to find the moles since I don't understand... |
Equivalents are part and parcel of Indian chemical education. I don't think college chemistry is going to be updated soon anytime there. I recently heard a complaint by a company to the chemistry chair in an American University. They said that your students do not understand normality! Please teach these concepts to yo... |
To complete your literature survey, include this publication cited at least 11 times so far: «Dichlorotrifluorophosphorane (PCl2F3): molecular structure by gas-phase electron diffraction and quadratic force field» by French _et al._ in _Inorg. Chem._ 1985, **24**, 2774–2777, [doi 10.1021/ic00212a014][1]. Despite the p... |
Recently, there has been a lot of discussion of Bent's rule (see for example "[What is Bent's rule?][1]") here in SE Chem. Simply stated, the rule suggests that $\mathrm{p}$-character tends to concentrate in orbitals directed at electronegative elements.
>Why does $\ce{F}$ replace an axial bond in $\ce{PCl5}$?
In... |
I am currently learning about Jahn–Teller effect. For elongation I wondered why the d orbitals with $z$ component are stabilised when the metal–ligand bonds are getting longer? I thought a longer bond would mean a less efficient overlap of the d orbital on the transition metal with the orbital on the ligand.
And if ... |
> $\pu{1 g}$ of $\ce{NaHCO3}$ and $\pu{2 g}$ of $\ce{Na2CO3}$ were dissolved in $\pu{50 mL}$ of water known as solution **A**. Solution **A** was mixed with $\pu{450 mL}$ of $\pu{0.154 M}$ of $\ce{NaCl (aq)}$ known as solution **C**. What is the resulting concentration of $\ce{Cl-}$ ions and $\ce{Na+}$ ions in solution... |
As a part of a chemistry experiment I would like to see the effect on the enthalpy of combustion of a mixture of vegetable oil and gasoline/diesel fuel when its percentage composition is changed (i.e 90% vegetable oil , 10 % fuel , and then 80% vegetable oil, 20% fuel etc.) . I am a bit confused on whether to use gasol... |
As a part of a chemistry experiment I would like to see the effect on the enthalpy of combustion of a mixture of vegetable oil and gasoline/diesel fuel when its percentage composition is changed (i.e 90% vegetable oil , 10 % fuel , and then 80% vegetable oil, 20% fuel etc.) .
I am a bit confused on whether to use g... |
**I am currently working on noble gas configurations in chemistry and I am having a hard time understanding why I got two questions wrong on a practice.**
**The instructions for the practice are here:**
Write out the noble gas configuration for the element. Enter your answer with all values without any spaces, h... |
Which textbook is this image on protein tertiary structure from? |
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/GlKKQ.png
The answer given is (3)but I am not quite sure about it. I feel it's (2)
Can anyone please explain this ? Thank you in advance kind human. |
# Straightforward question #
What would be the outcome of having an SN1 reaction carried out in a polar aprotic solvent? I have found this question approached scarcely and with unsatisfactory answers.
# What I know so far #
I know the SN1 reaction is carried out in a polar protic solvent since it helps stabilize the... |
I get how they would be dependent on temperature, but I don't see why they would be dependent on R. Am I overthinking it, is it just a useful constant? |
Why is the heat capacity of molecules in a system dependent on the universal gas constant, R? |
**Straightforward question**
What would be the outcome of having an SN1 reaction carried out in a polar aprotic solvent? I have found this question approached scarcely and with unsatisfactory answers.
**What I know so far**
I know the SN1 reaction is carried out in a polar protic solvent since it helps stabi... |
**Straightforward question**
What would be the outcome of having an SN1 reaction carried out in a polar aprotic solvent? I have found this question approached scarcely and with unsatisfactory answers.
**What I know so far**
I know the S<sub>N</sub>1 reaction is carried out in a polar protic solvent since it ... |
$\ce{C4O5}$ can be found in the patent art: see the Chinese patent CN108976392 - "Conjugated polymer photoelectric material containing quinoxaline imide condensed ring and application thereof" $\ce{C4O5}$ is called Oxolane-2,3,4,5-tetrone in PubChem [ https://pubchem.ncbi.nlm.nih.gov/compound/Oxolane-2_3_4_5-tetrone#... |
I'm writing a paper on chemistry and I would like to know which allotropes of sulfur exist naturally. Does anyone know the answer? Thanks! |
Which allotropes of sulfur exist naturally? |
https://books.google.com/books?id=aaELAAAAYAAJ&printsec=frontcover#v=onepage&q&f=false Notice the list of elements on pages 62–63. It includes a short description of each element's "Nature under Ordinary Conditions." I am curious to know what the author might have written for elements 43, 61, 72, 75, 84, 85, 87, 89, an... |
How would someone in 1917 describe elements 43, 61, 72, 75, 84, 85, 87, 89, and 91? |
Could there ever be a way to safely handle visible amounts of elements like astatine, francium, or protactinium? |
*As it is known that Para-Hydrogen has opposite spin and Ortho-Hydrogen has same spin.*
*Therefore, the energy of Para-Hydrogen is lower than that of Ortho-Hydrogen.*
*Therefore, the stability order should be $$Para-Hydrogen>Ortho-Hydrogen$$Is this true or is the stability order $$Ortho-Hydrogen>Para-Hydrogen$$If so,... |
Which is more stable Ortho or Para Hydrogen? |
In the proof that Helmholtz free energy is minimized at equilibrium, we use the fact that $dS_{total}=dS_{system}+dS_{bath}\geq 0$.
\
But we also use the fact that
$dS_{bath}=\frac{dU_{bath}}{T}=-\frac{dU_{system}}{T}$.
\
Why does this not imply that $dS_{system}=\frac{dU_{system}}{T}$ and therefore $dS_{total}=... |
Since the overlap increases with directional properties of orbital,
$$\ce{p - p > s - s > s - p}$$
<pre>
<img src="https://i.stack.imgur.com/3Jrak.png" title="CENTERED!">
</pre>
However it is also observed that the bond strength of
$$\ce{H-F > H-H > F-F}$$
$$\ce{\{s - p > s -... |
Since the overlap increases with directional properties of orbital,
$$\ce{p - p > s - s > s - p}$$
<pre>
<img src="https://i.stack.imgur.com/3Jrak.png" title="CENTERED!">
</pre>
However it is also observed that the bond strength of
$$\ce{H-F > H-H > F-F}$$
$$\ce{\{s - p > s -... |
In the proof that Helmholtz free energy is minimized at equilibrium, we use the fact that $dS_{total}=dS_{system}+dS_{bath}\geq 0$.
\
But we also use the fact that
$dS_{bath}=\frac{dU_{bath}}{T}=-\frac{dU_{system}}{T}$.
\
Why does this not imply that $dS_{system}=\frac{dU_{system}}{T}$ and therefore $dS_{total}=... |
In the proof that Helmholtz free energy is minimized at equilibrium, we use the fact that $dS_{total}=dS_{system}+dS_{bath}\geq 0$.
\
But we also use the fact that
$dS_{bath}=\frac{dU_{bath}}{T}=-\frac{dU_{system}}{T}$.
\
Why does this not imply that $dS_{system}=\frac{dU_{system}}{T}$ and therefore $dS_{total}=... |
$\ce{C4O5}$ can be found in a Chinese patent art(Ref. 1). It is called Oxolane-2,3,4,5-tetrone both in the patent and [PubChem][1]. In the patent, $\ce{C4O5}$ is shown as compound **2** and appears to be a compound which undergoes further reaction with itself eventually giving a desired product.
A google translat... |
>When $\ce{N_2O_5}$ is heated at a certain temperature, it disassociates as $$\ce{N_2O_5 (g)<=>N_2O_3 (g) + O_2 (g); K_c = 2.5}$$ At the same time $\ce{N_2O_3}$ also decomposes as $$\ce{N_2O_3 (g)<=> N_2O (g) + O_2 (g)}$$If initially 4 moles of $\ce{N_2O_5}$ were taken in a $\pu{1 L}$ flask and allowed to disassociate,... |
Will equilibrium ever establish if one of the products starts to disassociate? |
It is known that Para-Hydrogen has opposite spin and Ortho-Hydrogen has same spin.
Therefore, the energy of Para-Hydrogen is lower than that of Ortho-Hydrogen.
Therefore, the stability order should be: **Para-Hydrogen > Ortho-Hydrogen.**
Is this true or is the stability order the opposite of what I predicted?. Wha... |
Which is more stable: Ortho or Para Hydrogen? |
I'm writing a paper on chemistry and I would like to know which allotropes of sulfur exist naturally. I've searched on the Internet but I haven't found anything about natural sulfur allotropes. Does anyone know the answer? Thanks! |
I'm writing a paper on chemistry and I would like to know which allotropes of sulfur exist naturally. I've searched on the Internet but I haven't found anything about natural sulfur allotropes except this book(Ref. 1). Does anyone know the answer?
**Reference**
1. Steudel R., Eckert B. () Solid Sulfur Allotropes... |
Who says that $dS_{bath}=\frac{dU_{bath}}{T}=-\frac{dU_{system}}{T}$? The equation should correctly read $\Delta S_{bath}=\frac{\Delta U_{bath}}{T_{bath}}=\frac{Q_{bath}}{T_{bath}}=-\frac{Q_{syst}}{T_{bath}}$, where the Q's are for the irreversible path. The Q of the system for the reversible path is different from t... |
So I'm a high school student, and I'm learning about acid dissociation equilibrium. Basically I wanted to make the idea of Le Chatelier's principle rigorous in math, so I decided to take to it with some calculus. It was all fine with just the acid equilibrium:
\begin{align} K_a = \frac{\ce{[H3O+][A-]}}{\ce{[HA]}}. \en... |
In the proof that Helmholtz free energy is minimized at equilibrium, we use the fact that $$\mathrm dS_\text{total}=\mathrm dS_\text{system}+\mathrm dS_\text{bath}\geq 0$$
But we also use the fact that
$$\mathrm dS_\text{bath}=\frac{\mathrm dU_\text{bath}}T=-\frac{\mathrm dU_\text{system}}T$$
Why does this not im... |
First of all I am confused how something can be pi neutral? something either does or doesn't have filled p orbitals for example.
given something I have never seen acting as a ligand before like trimethylphosphate how can I work out whether this is pi accepting, donating or neutral? I am thinking the donor atom would b... |
Is there an 'easy' way to determine if a ligand is a pi acceptor, donor or neutral? |
Why is work and heat energy always viewed from the perspective of the system? |
As a part of a chemistry experiment I would like to see the effect on the enthalpy of combustion of a mixture of vegetable oil and gasoline/diesel fuel when its percentage composition is changed (i.e 90% vegetable oil, 10 % fuel, and then 80% vegetable oil, 20% fuel etc.).
I am a bit confused about whether to use g... |
I'm a high school student, and I'm learning about acid dissociation equilibrium.
I wanted to make the idea of Le Chatelier's principle rigorous in math, so I decided to take to it with some calculus. It was all fine with just the acid equilibrium:
$$\begin{align} K_a = \frac{\ce{[H3O+][A-]}}{\ce{[HA]}} \end{align... |
I have trouble understanding as to what the last part of the increase in liquid level means. I believe this is the foam formed after the fermentation? I am calculating for the pressure but I have trouble as to what volume should I use to find the moles since I don't understand the last part. It would greatly help m... |
Coupled cluster is a non-variational method, meaning that it can give energies that are below the true FCI energy (the "variational limit" for variational methods).
Often coupled cluster still gives energies far above the true FCI energy, and sometimes it gives energies that dip below the variational limit.
Are t... |
I’m an artist and I started working with recycled plastic bottles as a material recently. I want to paint the plastic and retain its transparency, but acrylic paint won’t stick without priming and generally looks bad. Permanent markers are good, but they leave streaks over large swathes of color and are expensive.
... |
Permanent ink from urethane, 99% IPA, and pigment? |
I know that potassium permanganate is used as a disinfectant for bacteria. Permanganate acts as a strong oxidizing agent that can rip the electrons off of bacterial cell membranes, resulting in a disruption that can lead to death. I've also read that potassium permanganate can be used as an oxidizing agent to kill moll... |
Why is potassium permanganate used to kill mollusks? |
I'm having trouble with the following problem:
> A gas fuel of Methane ($\ce{CH4}$) and Ethane ($\ce{C2H6}$) is burned
> with atmospheric air, and the volumetric analysis of the products of
> combustion yields the following: 5.32% $\ce{CO2}$, 1.60% $\ce{CO}$,
> 7.32% $\ce{O2}$, 12.24% $\ce{H2O}$ and the rest $\ce... |
i was asked to synthesis this compound from this amino acid, i first alkylated the alpha carbon using enolate alkylating method then i esterficated the amino acid but i'm doubtful that my steps are right, do i need to protect the amino group in the esterification step? or even before ?
[![enter image description here]... |
The problem is in the word "always". The statement "Work and heat energy are always viewed from the perspective of the system?" is wrong. Please inform your teacher that is true in the chemist's world only- and chemists did not invent thermodynamics.
Physicists have a different convention and chemists have a differe... |
Let's make this an abstract problem with species A, B, C, and F:
$$\ce{A <=> B + F}\tag{1}$$
$$\ce{B <=> C + F}\tag{2}$$
We can also write down the sum of the two reactions, which will also be at equilibrium:
$$\ce{A <=> C + 2 F}\tag{3 = 1+2}$$
And let's use a for the concentration of A and so on.
###... |
We know the basic Thermodynamic equations are:
$$ dU=-PdV+ TdS + \mu dN$$
$$ dH=dU+d(PV)= TdS+ \mu dN + VdP$$
we typically assume constant Pressure for a reaction carried out in air and neglect the dP term
$$dG=dH-d(TS)= \mu dN + SdT+ VdP$$
once again we neglect the dT and dP terms
but for heat of reaction we us... |
The problem is in the word "always". The statement "Work and heat energy are always viewed from the perspective of the system?" is wrong. Please inform your teacher that is true in the chemist's world only- and chemists did not invent thermodynamics.
Chemists have adopted a different convention than physicists. All ... |
I am a bit confused about why the monomer for a particular polymer is drawn in a particular way.
Shown below is the polymer:
[![enter image description here][1]][1]
Shown below is the monomer for the polymer which the answer scheme gives:
[![enter image description here][2]][2]
I am a bit confused ab... |
Why is the monomer for this polymer drawn in this way? |
[![enter image description here][1]][1]Is it possible for a molecule to absorb and emit at the same wavelength? What is the reason behind it?
I’m working on charged Tin porphyrins and got the excitation and emission (fluorescence) wavelength around 400nm.
For clarification, I have attached the exciation and emi... |
Why do neutron scattering lengths vary seemingly randomly with atomic number? |
I am not from a chemistry background. I am trying to see how the symmetry operations affect the stiffness tensor which led me in the path of understanding character tables. I am looking at the character table for C6v group and I cannot understand what the factor 2 for C6(z) means. Is it representative of the fact that ... |
What does the order of a class mean in a character table? |
[According to PubChem][1], diethylmethylamine has a remarkably low melting point of $-196.0^\circ$ C. This is substantially lower than the melting points of [dimethylethylamine][2] ($-140.0^\circ$ C), [trimethylamine][3] ($-117.1^\circ$ C), [triethylamine][4] ($-114.7^\circ$ C), and [3-methylpentane][5] (given as both... |
Why does diethylmethylamine have such a low melting point? |
Even if we use a strong oxidising agent like 'permanganate ion in acidic medium' it doesn't help oxidise iodide to iodate, but a relatively weaker oxidising agent 'permanganate ion in alkaline medium' helps to form iodate from iodide.
I have found one discussion similar to this but it's not convincing.[1]
[1]: ht... |
Why can't iodide be oxidised to iodate in acidic medium? |
Even if we use a strong oxidising agent like 'permanganate ion in acidic medium' it doesn't help oxidise iodide to iodate, but a relatively weaker oxidising agent 'permanganate ion in alkaline medium' helps to form iodate from iodide.
[I have found one discussion similar to this but it's not convincing.][1]
E... |
I am looking at a set of results showing a directly proportional relationship for an increasing maximum absorption wavelength (UV-vis spectra) with increasing donor number of solvent ligands. The complex has a Cu2+ centre, so 9 d electrons. assuming a tetragonal configuration how does this tie in with ligand strengths... |
I stupidly applied spray sunscreen on my children inside our white, acrylic bathtub and the floor ended up with a white, very sticky residue that rubs off on things, but will not wash away with detergent. The sunscreen turns out to be based on denatured alcohol and contains Benzyl Alcohol, so I suspect it melted the to... |
[According to PubChem][1], diethylmethylamine has a remarkably low melting point of $-196.0\ \mathrm{^\circ C}$. This is substantially lower than the melting points of [dimethylethylamine][2] ($-140.0\ \mathrm{^\circ C}$), [trimethylamine][3] ($-117.1\ \mathrm{^\circ C}$), [triethylamine][4] ($-114.7\ \mathrm{^\circ C}... |
> From Costanzo's Physiology book in Acid-Base Physiology chapter, this titration curve of a weak acid (HA) is provided:
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/YeUcH.png
What confused me is that in this diagram, the pH is on the X-axis rather than the Y-axis. Also, why does ... |
> From Costanzo's Physiology book in Acid-Base Physiology chapter, this titration curve of a weak acid (HA), in the context of discussing buffers is provided:
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/YeUcH.png
What confused me is that in this diagram, the pH is on the X-axis r... |
Chlorpromazine is an old ("typical") *antipsychotic* medication with a chemical structure which I as a non chemist find almost identical to that of all *"ine" tricyclic anti depresseants* such as imipramine, amitryptiline, nortryptiline, maprottyline and alike.
If I understood correctly, imipramine itself and later ... |
Why does Chlorpromazine not characterized as tricyclic? |
Chlorpromazine is an old ("typical") *antipsychotic* medication with a chemical structure which I as a non chemist find almost identical to that of all *"ine" tricyclic anti depresseants* such as imipramine, amitryptiline, nortryptiline, maprottyline and alike.
If I understood correctly, imipramine itself and later ... |
Acid ([Brønsted–Lowry Acid][1]) is a substance that gives away its H+, but the environment should be able to accept that H+. After it accepted it - the acid (which is now its conjugate base) can accept it back. There are 2 extremes:
* The environment already has plenty of H+ already. So even if acid gives its H+ to ... |
Acid ([Brønsted–Lowry Acid][1]) is a substance that gives away its H+, but the environment should be able to accept that H+. After it accepted it - the acid (which is now its conjugate base) can accept it back. There are 2 extremes:
* The environment already has plenty of H+ already. So even if acid gives its H+ to ... |
Chlorpromazine is an old ("typical") *anti-psychotic* medication with a chemical structure which I as a non chemist find almost identical to that of all *"ine" tricyclic anti depressants* such as imipramine, amitryptiline, nortryptiline, maprottyline, and alike.
If I understood correctly, imipramine itself and later... |
Why does chlorpromazine not characterized as tricyclic? |
Acid ([Brønsted–Lowry Acid][1]) is a substance that gives away its $\ce{H+}$, but the environment should be able to accept that $\ce{H+}$. After it accepted it - the acid (which is now its conjugate base) can accept it back. There are 2 extremes:
* The environment already has plenty of $\ce{H+}$ already. So even if ... |
> From Costanzo's Physiology book in Acid-Base Physiology chapter, this titration curve of a weak acid ($\ce{HA}$), in the context of discussing buffers is provided:
>
>[![pH Curve][1]][1]
[1]: https://i.stack.imgur.com/YeUcH.png
What confused me is that in this diagram, the $\mathrm{pH}$ is on the $x$-axis... |
I'm peeping the NIST thermo tables for [$\text{H}$](https://janaf.nist.gov/tables/H-001.html) and [$\text{H}_2$](https://janaf.nist.gov/tables/H-050.html), and I'm perplexed.
Seems to me that using
$$G=[\Delta H^\circ_f+H-H^\circ(T_r)]-T\cdot S^\circ$$
(well, actually correcting the entropy for partial pressur... |
Why is chlorpromazine not characterized as tricyclic? |
My friend has an old spectrometer set that his father used to own and we are trying to figure out how to use it. Asking his father about it is not an option unfortunately.
The box contains a handheld spectrometer. It is cylindrical in shape, length around 10 cm and diameter around 1 cm. There is a lens at both ends.... |
How would you examine samples of rocks using a handheld spectrometer? |
For a weak acid $\ce{HA}$ with acid constant $K_\mathrm{a}$:
$$\ce{HA + H2O <=> H3O+ + A-} \tag1$$
$$K_\mathrm{a} = \frac{[\ce{H3O+}][\ce{A-}]}{[\ce{HA}]} \ \Rightarrow \ [\ce{H3O+}] = K_\mathrm{a} \cdot \frac{[\ce{HA}]}{[\ce{A-}]} \tag2$$
Taking $-\log$ of both side of equation $(2)$:
$$-\log [\ce{H3O+}] =... |
> $\pu{10 mol}$ of an ideal gas confined to a volume of $\pu{10 L}$ is released into atmosphere at $\pu{300 K}$ where the pressure is $\pu{1 bar}.$ The work done by the gas is:
Work done can be found as
$$W = -p_\mathrm{ext}(V_\mathrm{f} - V_\mathrm{i}).\tag{1}$$
$$V_\mathrm{f} = \frac{nRT}{p} = \frac{\pu{10 m... |
I saw rubber-like silicones. Are there types of silicone that can be used in injection molding and once the process is finished - become as hard as regular plastic? At the same time they should have silicone's properties (citing Wikipedia):
- Low thermal conductivity
- Low chemical reactivity
- Low toxicity
- The... |
Does silicone hard as plastic exist? |
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