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I have two "rechargeable" heat packs which from my understanding operate on the following phase change
$$NaCH_3COO_{(aq)} \rightleftharpoons NaCH_3COO_{(s)} + \Delta H$$
Triggering the crystallization releases heat, and leaving them in boiling water returns it to its supersaturated form. The packs say if they ar... |
Why do reusable heat packs have a limited time frame before the reaction becomes irreversible? |
When a gas expands by b charles law pressure increases
$$\frac{p}{t}=k$$
thermodynamics says:
$$dQ=dU+PdV$$
so herfe one is considering constant pressure but how b charles law says it changes?So shouldn't it be:
$$dQ=dU+PdV+VdP$$
can't we apply a variable external pressure?
|
How can one say pressure is constant in thermodynamics? |
Most Raman spectrometer has the laser converging into focus with the sample at center like this.
[![enter image description here][1]][1]
Usually how many millions of H2O atoms will be covered by one spot size?
What will happen if the laser beam would be made parallel instead of converging. Will it increase the... |
Will Raman photon counts/Spectral resolution increase if laser beam becomes parallel? |
Spectral resolution is not dependent on the laser intensity. It is determined by the state of the sample ( gas, liquid or solid) and more importantly by the components of the instrument itself. For example, what is the slit width anf the number of lines on the grating? What type of detector is there? If it is charged c... |
How does DeepHF (CRISPR sgRNA design tool) compute $\Delta G_{\text{binding}}$? |
I saw the MO diagram for a NH3 molecule but couldn't understand why the combined atomic orbitals were in the positions they were, and if these positions were fixed.
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/7Nh5H.jpg
Why is the sigma anti bonding lower in energy than the pi ant... |
Why does the emission of dansyl group diminish with time in this experiment? |
50 grams of NaOH solids are added to 1,5L of 2,4M NaOH. Water is then added to the mix until the solution reaches 5L.
I am a bit confused because I have different answers with my friends, my approach was :
Finding the molarity when I mix NaOH solids to 1,5L NaOH(x) <br />
x = (1.5*2.4)/1.55 <br />
x = 2.322
... |
Searching for a fireproof sponge? |
50 grams of NaOH solids are added to 1,5L of 2,4M NaOH. Water is then added to the mix until the solution reaches 5L.
I am a bit confused because I have different answers with my friends, my approach was :
Finding the molarity when I mix NaOH solids to 1,5L NaOH(x) <br />
I did this using the n1=n2 formula <br ... |
$\pu{50 g}$ of $\ce{NaOH}$ solids are added to $\pu{1.5 L}$ of $\pu{2.4 M}$ $\ce{NaOH}$. Water is then added to the mix until the solution reaches $\pu{5 L}$.
I am a bit confused because I have different answers with my friends, my approach was :
Finding the molarity when I mix $\ce{NaOH}$ solids to $\pu{1.5 L }... |
**Condensed question formulation:**
>*Is there an experimental method to directly visualise the form 3D of a MO wave function, or at least the electron density associated with it?*
**Full statement:**
Molecular orbital theory is a crowning achievement of modern Chemistry: it is by far the most accurate descripti... |
Can we observe the shapes of MOs? |
**Condensed question formulation:**
>*Is there an experimental method to directly visualise the 3D form of a MO wave function, or at least the electron density associated with it?*
**Full statement:**
Molecular orbital theory is a crowning achievement of modern Chemistry: it is by far the most accurate descripti... |
I have two "rechargeable" heat packs which from my understanding operate on the following phase change
$$NaC_2H_3O_2_{(aq)} \rightleftharpoons NaC_2H_3O_2_{(s)} + \Delta H$$
Triggering the crystallization releases heat, and leaving them in boiling water returns it to its supersaturated form. The packs say if the... |
I have two "rechargeable" heat packs which from my understanding operate on the following phase change
$$ NaC_2H_3O_{2 (aq)} \rightleftharpoons NaC_2H_3O_{2(s)} + \Delta H$$
Triggering the crystallization releases heat, and leaving them in boiling water returns it to its supersaturated form. The packs say if the... |
I have two "rechargeable" heat packs which from my understanding operate on the phase change
$$ CH_3COONa_{(aq)} \rightleftharpoons CH_3COONa_{(s)} + \Delta H.$$
Triggering the crystallization releases heat, and leaving them in boiling water returns it to its supersaturated form. The packs say if they are left i... |
In one of my books it is written that boron does not react with alkali but in another book it is written that it reacts with alkali.
Can any one help in clearing this confusion? |
> I can't understand what adjacent means here?
For first order reflections, you only consider parallel planes that contain crystal lattice points. If you have a first order reflection (i.e. the Miller indices have no common divisor), the plane closest to a given origin will go through a/h, b/k and c/l. There will al... |
Which of the following is the strongest oxidizing agent? |
> Which of the following is the strongest oxidizing agent?
>
> A) $\ce{I2}$
>
> B) $\ce{Ag^2+}$
>
> C) $\ce{Cu^2+}$
The answer is apparently B) but I think it has to be A) because it is the only non-metal which actually wants to lose electrons. I just wanted to confirm whether it’s an incorrect solution or ... |
A swimmer coming out from a pool is covered with a film of water weighing about 18g. How much heat must be supplied to evaporate this water at 298 K? Calculate the internal energy of vaporisation at 100
o
C.
Δ
vap
H
⊝
for water at 373K =40.66 kJ mol
[![enter image description here][1]][1]
[1]: https://i.stack.img... |
Why is steam assumed to be an ideal gas here? |
What equipment can I put a substance or substrate under vacuum pack?
After buying this SERS silver substrates (which can rapidly decay in air). I need to immediately put them in vacuum packaging or container. How do I do that?
[![enter image description here][1]][1]
[![enter image description here][2]][2]
... |
I have seen $\ce{P(tBu)3HBF4}$ salt used as a precursor to the phosphine ligands for aqueous Pd-catalyzed micellar Suzuki-Miyaura coupling, but why does it work - after $\ce{Et3N}$ has liberated the tributyl phosphine ligand why does it not deactivate in the presence of water? |
ammonium ion is formed when N in NH3 forms a coordinate covalent bond with a proton (H+) (or amine as shown in below picture) as a result the N gains a formal positive charge and a positive charge on the proton disappears[![enter image description here][1]][1]
Now my question is, in a coordinate compound when NH3 ac... |
Does N in NH3 ligand gains formal positive charge as N in ammonium ion (NH4^+)? |
Ammonium ion is formed when N in $\ce{NH3}$ forms a coordinate covalent bond with a proton $\ce{(H+)}$ (or amine as shown in below picture) as a result the N gains a formal positive charge and a positive charge on the proton disappears[![enter image description here][1]][1]
Now my question is, in a coordinate compou... |
Does N in NH3 ligand gains formal positive charge as N in ammonium ion? |
I am a high school student.Recently my teacher finished teaching the chapter Chemical kinetics in which I have gone through Arrhenius equation.Can we estimate the change in entropy using it? I have done my calculation, considering the reversible reaction, $\ce{A <=> B}$ which has forward and backward rate constants $\m... |
I am confused by "$\text{mol}$".
I denote the unit of a physical quantity with square brackets (e.g. $[V]=l$), and the value of a physical quantitiy using curly brackets (e.g. $\left\{ V\right\}$ = 0.01).
A simple second order rate equation for number concentrations $n=N/V$ is given by,
$$\dot{n} = k^*_{on}n^2,... |
I am a high school student.Recently my teacher finished teaching the chapter Chemical kinetics in which I have gone through Arrhenius equation.Can we estimate the change in entropy using it? I have done my calculation, considering the reversible reaction, $\ce{A <=> B}$ which has forward and backward rate constants $\m... |
Orthocresol advice of not reading too much into formal charge is sage advice.
Rephrasing your question a bit: When ammonia is coordinated to say Co as in your example, does N of the NH3 gains the formal positive charge?
From the perspective and conventional thinking of inorganic chemistry, the central Co atom is a ... |
Why does it so long for an Lithium-ion battery to be charged from 98% to 100%?
It is not even comparable to the effort I exerce to pump my bike tires from 95 psi to (the minimally usable) 100 psi. There the effort is a few times more than that needed to pump from 35 psi to 40 psi. With Apple's Lithium ion batteries,... |
Why does it so long for a Lithium-ion battery to be charged from 98% to 100%? |
I'm struggling to understand why the following organic compound:
[![picture of 2-ethylhexane-1,3-diol][1]][1]
is named systemically as **2-ethylhexane-1,3-diol** (I think its common name is etohexadiol), if the longest carbon chain in the molecule is actually 7 carbons long, as labelled here: [![picture of 2-ethylh... |
I have recently reviewed the synthesis of the dehydrating agent DMC (7), but I could find no reported mechanisms for its formation. I have proposed the mechanism drawn below, but I am unsure about a few steps.
[![DMC Mech.][1]][1]
To start, It is clear that this reaction is similar to the Vilsmier-Haack reaction,... |
I have recently reviewed the synthesis of the dehydrating agent DMC (7), but I could find no reported mechanisms for its formation. I have proposed the mechanism drawn below, but I am unsure about a few steps.
[![DMC Mech.][1]][1]
To start, It is clear that this reaction is similar to the Vilsmier-Haack reaction,... |
so basically it's between primary benzylic carbocation which is known to be stable (benzlic) and secondary carbocation which is allylic... which is also stablized by resonance, i know that usually benzylic is more stable than allylic but when they are same degree.. here its different...
any help?
[![enter image des... |
Carbocation stability order? |
I'm currently doing a case study to find out the exact volume of helium gas required for FE tests on ball valves regards to the valves' volume and pressure class and the number of helium tanks needed for it (assuming the test is being done at room temperature)
The specifications of helium gas that is being supplied... |
I have searched everywhere but there are no worked examples of how to calculate the $\langle\chi_i |\hat{h}| \chi_j \rangle $ values for the Fock Operator using the SCF HF Roothaan method. I am given a wavefunction that is expanded as a set of basis functions, but I don't know how to apply the second derivative to some... |
How to calculate core electron SCF Fock Matrix Elements? |
> Why do reusable heat packs have a limited time frame before the
> reaction becomes irreversible?
This reaction should never become irreversible until and unless there is bacterial growth or loss of water for some reasons. For example, one manufacturer explains that the pads can re-used for 18 years! http://www.... |
What should be the order of electron density in monosubstituted halogen derivatives of benzene?
I am aware that fluorobenzene is more ring activating as compared to chlorobenzene due to the more effective +M effect of F over Cl, but I would like to know the full order among all the monohalogenated benzene compounds.
... |
What should be the order of electron density in monosubstituted halogen derivatives of benzene?
I am aware that fluorobenzene is more ring activating as compared to chlorobenzene due to the more effective +M effect of F over Cl, but I would like to know the full order among all the monohalogenated benzene compounds.
... |
How to determine what covalent compound a substance is? |
What will be no. of stereoisomers of CH3CH(OH)CH(OH)CH(OH)CH3..? |
The problem is huge, because there exist many millions of different compounds which are white, soluble in water, and do not conduct electricity. Here are a couple of preliminary tests.
You might first determine if it is organic, by heating it in a test tube in a Bunsen burner. It will darken and be progressively tra... |
> What will be the number of stereoisomers of $\ce{CH3CH(OH)CH(OH)CH(OH)CH3}?$
By formula $2^n - 1 + 2^n + 1/2$ for $n$ being the odd number of chiral centres, it's $6;$ four optically active and two optically inactive.
Optically active when <i>RRS</i>, <i>SSR</i>, <i>RR</i>, <i>SS</i>, but I am not getting how ... |
When performing a titration, once the acid/base in the burette is slowly released into the conical flask, it may splash onto the sides of the conical flask. It is then advised that we wash the sides of the conical flask with deionised water.
Will this not affect the concentration of the acid/base solution and theref... |
Will washing a conical flask with deionised water to remove splashes affect the titration result? |
When performing a titration, once the acid/base in the burette is slowly released into the conical flask, it may splash onto the sides of the conical flask. It is then advised that we wash the sides of the conical flask with deionised water.
Will this not affect the concentration of the acid/base solution by decreas... |
Suppose we have in a box $3 \,{\rm mol}$ $\ce{O}$ and $3 \,{\rm mol}$ $\ce{N}$. Is the addition of these two quantities meaningfull? We do it all the time when we want to find the molar fraction. I can't understand if it dimensionally correct to add these two things. If a mole is like a dozen then a mole of eggs and a ... |
Are the units of mole of oxygen molecules the same with the units of mole of nitrogen molecules? |
I am currently studying for an organic chemistry exam and I just couldn't come up with a solution to the following question:
**Consider the reaction of 1-Propene + Br2 with water as solvent.**
Why will the nucleophilic water molecule add on C-2 and rather than on C1 of the Bromonium-Ion?
The answer seems to be, ... |
Regioselectivity of electrophilic addition of Halogen and Water (Halohydrin) on Alkenes? |
The laws of conservation of mass, definite proportions multiple proportions makes sense and were definitely useful for chemists in the early days of modern chemistry.
I don't understand how the law of reciprocal proportions is useful. It seems too unnecessarily complex for someone to intuitively come up with.
Is ther... |
So I'm trying to derive
$$\mu\nabla^2\vec{v}=\nabla P-\rho g$$
from Navier-Stokes equation
$$\begin{align}\rho \left(\frac{\partial\vec{v}}{\partial t}+\vec{v}\cdot(\nabla\vec{v})\right)&=\rho\vec{g}-\nabla P+\mu\nabla^2\vec{v}\\
\rho \left(\frac{\partial\vec{v}}{\partial t}+\vec{v}\cdot(\nabla\vec{v})\right)-\mu... |
I think the sentence cited above in the [wikipedia article][1] is very confusing.
But the [wiki article about the Avogadro constant][2] helped me resolve my confusion, which defines $mol$ via the Avogadro constant:
$$N_A = \left\{N_A\right\}[N_A] = 6.022\times10^{23} \text{mol}^{-1}.$$
Hence
$$k_{on} = k^*_... |
I am confused by "$\text{mol}$".
I denote the unit of a physical quantity with square brackets (e.g. $[V]=l$), and the value of a physical quantitiy using curly brackets (e.g. $\left\{ V\right\}$ = 0.01).
A simple second order rate equation for number concentrations $n=N/V$ is given by,
$$\dot{n} = k^*_{on}n^2,... |
cysteine amino acid has an embeded sulfur group in its side chain. Looking at electronegativity difference of hydrogen and sulfur, it can be consider a non polar because the electronegativity difference is less than 0.5 which make it non polar but still we put it in polar category, why? |
Does chloroantimonic acid exists? What do we get when we mix hydrochloric acid and antimony pentachloride and is the mixture stronger or weaker than fluoriantimonic acid. How about bromo and iodoantimonic acids? |
Chlroantimonic acid has been synthesised by dissolving antimony trioxide in concentrated hydrochloric acid. The relevant information can be found here[1]:
> Complex compounds are known to which the formulae $\ce{HSbCl6}$, $\ce{H2SbCl7 }$ and
> $\ce{H3SbCl8}$ have been ascribed; these may be regarded as meta-, pyro-... |
It is a good question which has already been somewhat addressed in the 1880s. This "field" was called *quantity calculus*. Calculus here is not the integration / differentiation, but rather the Latin calculus implying a *method of calculation*.
There is a very nice article "Quantity Calculus: Unambiguous Designation... |
Chlroantimonic acid has been synthesised by dissolving antimony trioxide in concentrated hydrochloric acid followed by saturation with chlorine. The relevant information can be found here[1]:
> Complex compounds are known to which the formulae $\ce{HSbCl6}$, $\ce{H2SbCl7 }$ and
> $\ce{H3SbCl8}$ have been ascribed; ... |
It is a good question which has already been somewhat addressed in the 1880s. This "field" was called *quantity calculus*. Calculus here is not the integration / differentiation, but rather the Latin calculus implying a *method of calculation*.
There is a very nice article "Quantity Calculus: Unambiguous Designation... |
What chemical can be used to absorb O2 from the air at normal temperature and pressure, then release the O2 at normal pressure and elevated temperature, below 900*C (1650*F), that can be cycled many times?
Closest solutions i've found are silver, but its quite expensive, and absorbs oxygen slowly at normal temperature... |
When ever I search B12H12 Borane I can't seem to find anything, and get met with only the dianion of B12H12. Why doesn't B12H12 exist on its own? |
What chemical can be used to absorb O2 from the air at normal temperature and pressure, then release the O2 at normal pressure and elevated temperature, below 900*C (1650*F), that can be cycled many times?
Closest solutions i've found are silver, but its quite expensive, and absorbs oxygen slowly at normal temperature... |
What chemical can be used to absorb $\ce{O2}$ from the air at normal temperature and pressure, then release the $\ce{O2}$ at normal pressure and elevated temperature, below $900 \,\pu{C}$ ($1650 \, \pu{F}$), that can be cycled many times?
Closest solutions i've found are silver, but its quite expensive, and absorbs ... |
What chemical can be used to absorb $\ce{O2}$ from the air at normal temperature and pressure, then release the $\ce{O2}$ at normal pressure and elevated temperature, below $\pu{900 ^\circ C}$ ($\pu{1650 ^\circ F}$), that can be cycled many times?
Closest solutions I've found are silver, but its quite expensive, and... |
I'm currently doing a case study to find out the exact volume of helium gas required for FE tests on ball valves regards to the valves' volume and pressure class and the number of helium tanks needed for it (assuming the test is being done at room temperature)
The specifications of helium gas that is being supplied... |
Whenever I searched "$\ce{B12H12}$ Borane", I can't seem to find anything, and get met with only the dianion of $\ce{B12H12}$. Why doesn't $\ce{B12H12}$ exist on its own? |
Why does B12H12 Borane not exist? |
> What will be the number of stereoisomers of $\ce{CH3CH(OH)CH(OH)CH(OH)CH3}?$
By formula $2^n - 1 + 2^n + 1/2$ for $n$ being the odd number of chiral centres, it's $6;$ four optically active and two optically inactive.
Optically active when <i>RRS</i>, <i>SSR</i>, <i>RR</i>, <i>SS</i>, but I am not getting how ... |
I'm currently doing a case study to find out the exact volume of helium gas required for FE tests on ball valves regards to the valves' volume and pressure class and the number of helium tanks needed for it (assuming the test is being done at room temperature)
The specifications of helium gas that is being supplied... |
The laws of conservation of mass, definite proportions multiple proportions makes sense and were definitely useful for chemists in the early days of modern chemistry. <br>
The law of reciprocal proportions states that
> If element A combines with element B and also with C, then, if B and C combine together, the pro... |
Explain why diethyl ether does not have a UV spectrum, even though it has lone-pair electrons.
My particular doubt is that can we say that pi star molecular orbital doesnt exist because there are no pi bonded electrons in the compound? |
To measure the atomic hydrogen spectrum people often uses hydrogen gas tubes as light source.
Since the gas in the tube is the molecule $H_2$ , why we obtain the spectrum of atomic hydrogen?
If you could give me some reference I would be grateful. |
The FFC Cambridge process (described here: https://en.wikipedia.org/wiki/FFC_Cambridge_process ) with platinium electrodes allows the reduction of almost any metal oxide to a pure metal, with an oxygen byproduct.
So far, so good. What I'm trying to understand is how it would handle mixtures of of materials. For ex... |
The [FFC Cambridge process][1] with platinium electrodes allows the reduction of almost any metal oxide to a pure metal, with an oxygen byproduct.
So far, so good. What I'm trying to understand is how it would handle mixtures of of materials. For example, if it was a mixture of iron oide and titanium oxide, what w... |
One option might be something like [FFC Cambridge process][1] - it can reduce most (possibly all) oxides directly, at the cost of potentially high amounts of energy. It's been tested with [simulated lunar regolith][2] and while that's not exactly the same as your granite, they're definitly related.
I don't know if t... |
To measure the atomic hydrogen spectrum people often uses hydrogen gas tubes as light source.
Since the gas in the tube is the molecule $H_2$ , why we obtain the spectrum of atomic hydrogen?
My guess is that because the voltage is so high, so that the molecules are totally dissociated.
If you could give me some r... |
The laws of conservation of mass, definite proportions multiple proportions makes sense and were definitely useful for chemists in the early days of modern chemistry. <br>
The [law of reciprocal proportions][1] states that
> If element A combines with element B and also with C, then, if B and C combine together, th... |
What's the reason that alkanolamines (e.g. monoethanolamine, diethanolamine, triethanolamine) of technical purity change their color (from colorless over yellowish to red-brown) at storage?
Is it because of oxidation, or UV-light? |
What's the reason that alkanolamines change their color at storage? |
The pH at the equivalence point of titration of $\ce{Na2CO3}$ solution with $\ce{HCl}$ is around 3.7, as shown in this titration curve:
[![enter image description here][1]][1]
At this point, the following reaction is completed:
$$\ce{NaHCO3 + HCl -> NaCl + H2O + CO2}$$
But considering the fact that $\ce{NaC... |
The comments certainly clarify the law of definite proportions and are an excellent tutorial on how to write a good question but sheds little light on your question “Is there any intuition/specific reason that Jeremias Richter came up with it?”
From reading a number of short bibliographic sketches about Richter it... |
Oxidative degradation by oxygen certainly occurs and has been studied [1], [2]. I presume this is *via* the N-oxide, but I can't access the papers. I've seen no mention oof UV degradation, but that doesn't mean it does not happen.
[1]: https://ntnuopen.ntnu.no/ntnu-xmlui/bitstream/handle/11250/2461998/Vevelstad_... |
The comments certainly clarify the law of reciprocal proportions and are an excellent tutorial on how to write a good question but sheds little light on your question “Is there any intuition/specific reason that Jeremias Richter came up with it?”
From reading a number of short bibliographic sketches about Richter ... |
The comments certainly clarify the law of reciprocal proportions and are an excellent tutorial on how to write a good question but sheds little light on your question “Is there any intuition/specific reason that Jeremias Richter came up with it?”
From reading a number of short bibliographic sketches about Richter ... |
Oxidative degradation by oxygen certainly occurs and has been studied [1], [2]. I presume this is *via* the N-oxide, but I can't access the papers. I've seen no mention of UV degradation, but that doesn't mean it does not happen.
[1]: https://ntnuopen.ntnu.no/ntnu-xmlui/bitstream/handle/11250/2461998/Vevelstad_O... |
After defining the law of definite proportions and law of multiple proportions, we could successfully understand how two elements combine together.
The question arose: _What about if we took more than two elements?_. So, J. Richter came up with the law of reciprocal proportions, which is infact intuitive, I guess y... |
I've always wondered, what is the meaning of the following terms on a certificate of analysis:
- "Heavy Metals"
- "Heavy Metals (as Pb)"
What exactly is comprised in "heavy metals", "heavy metals (as Pb)" and what is excluded from each? What is the difference between the two variants? I tried to find a clea... |
Meaning of the Term "Heavy Metals" in CofA? |
I was wondering if either of SMILES or graph representations (in their vanilla form) can distinguish between two conformers of the same molecule.
1. Can this be enhanced by adding additional metadata on Graph nodes?
what info are necessary then?
2. Can this be enhanced for SMILES representations? |
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