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Here is some data on other well-soluble salts:
[![http://wps.prenhall.com/wps/media/objects/946/969212/images/table11_2.gif][1]][1]
Comparing the values, both the anion and the cation contribute to magnitude of enthalpy and entropy. The larger cations seem to contribute to a larger entropy of dissolution, as do t... |
The nearest I came to an explanation is an article (Ref. 1) by authors of the database explaining that, in the case of $\ce{H2O (cr,l)}$, the notation (cr,l) refers to the condensed state. Also, [a link][1] from the above data page explains that "cr=crystal" and "l=liquid" (thanks MaxW for hinting at the solution).
... |
Here is some data on other well-soluble salts:
[![http://wps.prenhall.com/wps/media/objects/946/969212/images/table11_2.gif][1]][1]
Comparing the values, both the anion and the cation contribute to magnitude of enthalpy and entropy. The larger cations seem to contribute to a larger entropy of dissolution, as do t... |
Can you please explain to me why are A and E not relevant resonance structures of the molecule F?
And is B aromatic? |
I was reading about the self-consistent extended Hückel method (SC-EHT), and stumbled upon various formulae for the diagonal elements of the Hamiltonian matrix. I noticed that many formulae depend on either the gross atomic population or Mulliken atomic charges. I know the formula for the Mulliken population analysis, ... |
What are Mulliken atomic charges, and how are they computed? |
Can you use something other than sodium chloride? Sodium bromide seems to be much more soluble in methanol:
Sodium chloride = [14.9 g/kg](https://en.m.wikipedia.org/wiki/Sodium_chloride)
Sodium bromide = [168 g/kg](https://en.m.wikipedia.org/wiki/Sodium_bromide)
A similar trend would be expected with other al... |
[![enter image description here][1]][1]
Can you please explain to me why are A and E not relevant resonance structures of the molecule F?
And is B aromatic?
[1]: https://i.stack.imgur.com/mDx2V.jpg |
the answer given by himanshupandey in the book advanced problems in organic chemistry
chapter isomerism
page 76 is 10.but by calculating using fundamental principle of counting and by viewing the same question in this site i figured the answer to be 16 .i don't get how he given 10? |
Electronegative atoms withdraw electrons by their inductuve effect. Does this fact remain true even when they are heavily loaded with electrons through negative formal charge? Are these two ideas related? |
Does an electronegative atom which carries a negative formal charge withdraw electrons by induction? |
The answer given by Himanshu Pandey in the book Advanced Problems in Organic Chemistry, Chapter Isomerism, Page 76 is 10. But by calculating using the fundamental principle of counting and by viewing [a similar question on this site](https://chemistry.stackexchange.com/q/107033/7951), I figured the answer to be 16. I d... |
The short answer to this is that there is no single answer to this problem as the vapor composition that is produced by any given atomizer is dependant upon a large number of components. To name a few:
- The initial composition of the liquid, which will vary flavor to flavor and manufacturer to manufacturer. You c... |
**Question:**
[![enter image description here][1]][1]
**My Approach:**
Since both the compounds have the **same principal functional group**, they can't be functional isomers. Obviously they are different compounds. Now options A and C are ruled out. Further the substituent ketone in first compound and aldehyde ... |
At low concentrations for which the ideal bp elevation/fp depression expressions usually apply, molarity is linearly proportional to molality, therefore the statements are equivalent.
[This webpage][1] explains nicely why low concentrations are important:
> Raoult's law only works for low concentration solutions... |
Chemistry newb here. I've been reading about how energy is released when new chemical bonds are formed but it's hard to find info on how that typically manifests itself (besides that it's via heat). I read somewhere that the valence electrons will move into lower energy orbits during a bond, but I thought that always... |
How does the energy released during a bond formation typically manifest itself on atomic level? |
Is the equation dG=Vdp-SdT valid only for reversible process. Can it be applied for irreversible too? |
In the derivation, we write:
$$
\begin{align}
G &= H - TS &\quad&\to&\quad \mathrm dG &= \mathrm dH - T\,\mathrm dS - S\,\mathrm dT \\
H &= U + pV &\quad&\to&\quad \mathrm dH &= \mathrm dU + p\,\mathrm dV + V\,\mathrm dp \\
U &= Q + W &\quad&\to&\quad \mathrm dU &= \mathrm dQ - p\,\mathrm dV \\
& & & & &= T\,... |
Is the equation dG = Vdp - SdT valid only for a reversible process? Can it be applied for an irreversible one too? |
For the following question:
Which molecules react to form a dative/coordinate bond?
A. CH4 and NH3
B. C2H2 and Cl2
C. NH3 and HF
D. Cl2 and HF
The answer scheme says C is correct, but I do not see how two already complete molecules can form coordinate bonds. NH3 has a lone pair of electrons, HF having none.... |
For the following question
> Which molecules react to form a dative/coordinate bond?
> **A**. $\ce{CH4}$ and $\ce{NH3}$
> **B**. $\ce{C2H2}$ and $\ce{Cl2}$
> **C**. $\ce{NH3}$ and $\ce{HF}$
> **D**. $\ce{Cl2}$ and $\ce{HF}$
the answer scheme says **C** is correct, but I do not see how two already comp... |
The temperature at which $\ce{NO_x}$ is in equilibrium with its liquid and vapor phase at 1 atm is about –84 °C. Does that mean $\ce{NO_x}$ exists as a liquid at that temperature? What about it's vapor phase then, because it's vapor and liquid phase should be at equilibrium, right?
Also, it's that the reason why com... |
There is no reason why *fluorescence emission* background should look similar at all with green and red excitation.
### Different substances
- You say the green excitation spectrum is of Coke.
- According to the video, the red excitation spectrum is of the peel of a tangerine.
Those samples consist of totall... |
There is no reason why *fluorescence emission* background should look similar at all with green and red excitation.
### Different substances
- You say the green excitation spectrum is of Coke.
- According to the video, the red excitation spectrum is of the peel of a tangerine.
Those samples consist of totall... |
There is no reason why *fluorescence emission* background should look similar at all with green and red excitation.
### Different substances
- You say the green excitation spectrum is of Coke.
- According to the video, the red excitation spectrum is of the peel of a tangerine.
Those samples consist of totall... |
i found several definitions of the activation energy in electrochemistry, but i dont know why they are different. For example in Atkins "Physical Chemistry" the activation gibbs energy is defined as:
$\Delta^‡G_c=\Delta^‡G_c(0)+\alpha F\Delta\phi$
and he assumed that $\Delta\phi$ is equal to $E^{eq}$ when no curr... |
What is the correct definition for the activation Gibbs energy? |
Our teacher told us that five membered ring can’t be formed through Friedel-Crafts alkylation but acylation is OK. Why is that? Is it because alkylation is an unfavored 5-endo-trig reaction but acylation is 5-endo-dig, thus favored? |
Can five membered ring form through Friedel-Crafts alkylation? |
This answer is based on the educated guess that the green excitation Raman spectrum was acquired with a **dispersive** Raman instrument\*.
> But why is there general nonzero background in intensity? What caused it?
**For any real-life instrumentation, you should never assume to measure 0 signal for 0 analyte co... |
There are few articles describing the conversion of lactose to GOS on Wiley Online Library with different enzymes. Yet none of them really talks about what % of the lactose in milk can be converted to GOS.
Is it possible to convert all lactose to GOS, and still be able to consume the milk/dairy product?
|
This answer is based on the educated guess that the green excitation Raman spectrum was acquired with a **dispersive** Raman instrument\*.
> But why is there general nonzero background in intensity? What caused it?
**For any real-life instrumentation, you should never assume to measure 0 signal for 0 analyte co... |
To find the ground state density in DFT, you set the following Lagrangian:
$$L = E[\rho(\vec r)] - \mu(\int \rho d\vec r - N)$$
While minimising with respect to the density, we get:
$$\frac{\partial L}{\partial \rho} = \frac{\partial E[\rho(\vec r)]}{\partial \rho} - \mu = 0$$
My problem is with the explici... |
I'm considering the following reaction:
ZnSO4 + 2 KCl = ZnCl2 + K2SO4
The high solubility of ZnCl2 would favour the ZnSO4 & KCl direction of the reaction, but I'm wondering if I could turn this around by making the reaction occur in a flow of boiling hot water.
The idea would be to subject (initially dry) Zn... |
Is the equation dG = Vdp − SdT valid only for a reversible process? Can it be applied for an irreversible one too? |
There are spectroscopy selection rules marking some radiative electronic transitions as forbidden. For example, it is stated that single electron of H atom can not move from S2 to S1, or from P2 to S2 (and vice versa) with photon emission/absorption.
But is this true in the case of collisional (or, more generally, ... |
Are there any forbidden collisional electronic transitions? |
I'm considering the following reaction:
$\ce{ZnSO4} + 2 \ce{KCl} \ce{->} \ce{ZnCl2} + \ce{K2SO4}$
The high solubility of $\ce{ZnCl2}$ would favour the $\ce{ZnSO4}$ & $\ce{KCl}$ direction of the reaction, but I'm wondering if I could turn this around by making the reaction occur in a flow of boiling hot water.
... |
Why is silver chloride less soluble than silver nitrate? |
The third law of thermodynamics states that the absolute entropy of a pure crystalline substance is $0$ at $0\,\mathrm{K}$. In the analysis of chemical reactions this absolute scale is sued to calculate the entropy change. However, it is also noted that some substances like $\ce{CO2}$ have residual entropy at $0\,\mat... |
How can residual entropies be reconciled with the Third Law? |
I plan to work with an electrolyte that contains 1 g of Palladium(II) chloride. I am trying to estimate how much of a hazard this system could possibly pose (and provide ventilation, chlorine monitoring and other safety measures accordingly).
How would you go about determining what max. ppm concentration of chlorin... |
How to estimate the maximum chlorine hazard from 1 g of Palladium(II) chloride? |
Consider the molecular mass, and the mass of chlorine in 1 g of $\ce{PdCl2}$. Then consider the volume of the work space, and how quickly the $\ce{Cl2}$ disperses to fill that space.
Until it disperses, the concentration at the source might be 1E6 ppm (i.e. 100%), but is that meaningful? If it disperses to fill a fl... |
I am considering labware options to handle NaOH solutions at ~150°C. One appealing idea would be to coat my current glassware with gold. I've read different sources mentioning the possibility without further detail.
The most detailed description of a process for this is [INSTRUCTIONS FOR GOLD PLATING ON GLASS][1] by... |
I was recently going studying about Metallurgy and read in a book namely Concise Inorganic Chemistry by J D Lee that the process of froth floating can also be applied to ores such as Malachite (CuCO3.Cu(OH)2) and Anglesite(PbSO4) by using Na2S as and activator.
The coatings formed are CuS and PbS respectively. Howev... |
Which compound has resonance structures? |
There is a well-known electron shielding effect: negatively-charged internal electronic shell screens external shells from positive nuclei, thus increasing their radii.
Thus, 2S orbital radius of Li atom (ground state) should be greater than radius of excited Li2+ cation with single 2S electron.
But is there a ... |
Do external electronic shells influence internal ones? |
The following compound is a carbocation.
[![enter image description here][1]][1]
Clearly, the given compound does not have any element of symmetry. The compound is non planar due to the presence of ethyl group. Thus it must be chiral. But my book says the compound is achiral. How is this possible? Please explain.... |
Unknowing that the tubes used in the centrifuge are made of polycarbonate, I cleaned them with acetone. following, a white smoky discolouration appeared and the tubes turned opaque. is there any way to remove this? |
**Asking why**
When you ask why, you want to know about causality. If I ask "why does the cold pack show a decrease in temperature" and the answer is "because the reaction is endothermic", this might be considered a tautology. After all, endothermic means that energy is needed, and this energy can come from the surr... |
The average c=c double bond has somewhere around 614 kJ/mol of energy, if we convert it to eV, then the bond strength is roughly 6.4 eV.
Additionally, Ethene absorbs light at 171 nm.
However, if we calculate the energy of 171 nm it is around 7.3 eV, hence ethene absorbs energy that is higher than its bonding energy, ... |
Why does ethene not disintegrate upon excitation? |
I've seen that it's defined as $h_0 = h + \frac{v^2}{2}$, where $h_0$ is the total enthalpy per unit mass. I can see that the $\frac{v^2}{2}$ term probably has something to do with kinetic energy, but I am still really confused. Doesn't $h$ already account for flow work? And also, how can both sides of the equation hav... |
What is total enthalpy? |
> The stability order of the following is:
> [![Carbocations][1]][1]
> **A**. **III** > **II** > **I** > **IV**
> **B**. **II** > **III** > **I** > **IV**
> **C**. **I** > **III** > **IV** > **II**
> **D**. **I** > **III** > **II** > **IV**
> Answer: **D**
I came across a question where we had to... |
> The stability order of the following is:
> [![Carbocations][1]][1]
> **A**. **III** > **II** > **I** > **IV**
> **B**. **II** > **III** > **I** > **IV**
> **C**. **I** > **III** > **IV** > **II**
> **D**. **I** > **III** > **II** > **IV**
Answer:
>! **D**
I came across a question where we h... |
I read that to test for the presence of Phenol Groups in an Organic Compound Aniline Dye Test can be performed. If the solution has phenol present it gives a red or orange precipitate to confirm the presence, however as a side note it was mentioned that this test is applicable for detection of small quantities of pheno... |
> Which compound has resonance structures?
> **A**. $\ce{C6H12}$
> **B**. $\ce{CH3CHO}$
> **C**. $\ce{NaBr}$
> **D**. $\ce{Na2CO3}$
The answer key says **D** is correct, but I do not understand why $\ce{Na2CO3},$ which is an ionic compound between the polyatomic ion carbonate and sodium, can have resonan... |
Unknowing that the tubes used in the centrifuge are made of polycarbonate, I cleaned them with acetone. Following, a white smoky discolouration appeared and the tubes turned opaque. Is there any way to remove this? |
How to remove the foggy discoloration in polycarbonate tubes caused by acetone? |
Chemistry newb here. I've been reading about how energy is released when new chemical bonds are formed but it's hard to find info on how that typically manifests itself (besides that it's via heat). I read somewhere that the valence electrons will move into lower energy orbits during a bond, but I thought that always... |
I read about Ceric Ammonium Nitrate Test for Alcohols and a red colour is produced if the solution has an alcohol functional group however as a side note it was mentioned that this test is only useful for compounds having less than 10 Carbon atoms. Why is it so? |
I read about Lucas Test for Alcohols and a cloudy precipitate is produced if the solution has an alcohol functional group which has either 3 degree or 2 degree however as a side note it was mentioned that this test is only useful for compounds having less than 6 Carbon atoms. Why is it so? |
I have a problem. I have purified a protein with method A and then B. After method A I have a protein concentration of 20 mg/ml and after method B a concentration of 18 mg/ml. Method B is dialysis and my sample was diluted, so the volume went from 5 mL (A) to 6 mL (B).
When I present my total amount of protein at th... |
How should I interpret and present my total protein amount? |
How to avoid cannizaro reaction during aldol reaction? |
Im trying to calculate ion strength and pH of solution.
Components of the solution:
47 ul of 1000 pmol DNA in Elution Buffer (10 mM Tris-HCl pH 8.5) was bound to 3 ul of 10 µM YoYo1 (flourescent dye) in DMSO and was mixed with 50 ul of Tris-EDTA buffer (100 mM Tris-HCl, 0.01 M EDTA pH 8.0).
About calculation of ... |
Could please help me to calculating ionic strength and pH of buffer solution? |
Is it possible to use CI3TMS (a carbon with three iodo groups and a trimethylsilyl protecting group) and three equivalents of an ethyl grignard reagent to prepare 3-ethylpenan-1-ol? By deprotecting the product after the grignard reaction using tributylammonium fluoride, is it possible to produce the desired product? I ... |
I understand that tert-butoxide is used to favor the Hofmann product in elimination reactions due to its steric bulk (and thus inability to abstract a proton in a more substituted position); however, I have often seen proposed organic synthesis involving the use of tert-butoxide when it is seemingly irrelevant. For exa... |
Why is tert-butoxide often used in elimination reactions when it is not necessary? |
Generally, it's just because there's a big bottle of $\ce{t-BuOK}$ lying around, so why bother using something else?
In the same range of ideas, I've seen publications where they used $\ce{n-BuLi}$ to deprotonate an alcohol; it's completely overkill, but was probably just more convenient in their case than $\ce{NaH}... |
I read about the Lucas test for alcohols in which a cloudy precipitate is produced with a tertiary or secondary alcohol. However, on a side note it was mentioned that this test is useful only for compounds having less than six carbon atoms. Why is this so? |
Why is the Lucas test not recommended to differentiate higher alcohols? |
Not only do "outer" electrons impart some shielding to "inner" ones, but an analytical technique is based on that fact.
In [X-ray photoelectron spectroscopy](https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy), binding energies of electrons just below the outer shell are measured. These binding energies... |
Not only do "outer" electrons impart some shielding to "inner" ones, but an analytical technique is based on that fact.
In [X-ray photoelectron spectroscopy](https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy), binding energies of electrons just below the outer shell are measured. These binding energies... |
Is it possible to use CI3TMS (a carbon with three iodo groups and a trimethylsilyl protecting group) and three equivalents of an ethyl grignard reagent to prepare 3-ethylpenan-1-ol? By deprotecting the product after the grignard reaction using tributylammonium fluoride, is it possible to produce the desired product? I ... |
What produces this NMR spectrum? |
What is the mechanism by which the *ortho*- and *para*- spin isomers of hydrogen interconvert?
If such a mechanism exists, does this mean that *ortho*-hydrogen increases in concentration on increasing temperature? |
The first question is:
>What is the mechanism by which spin isomers of hydrogen switch between the ortho and para forms?
There is some explanation in [*ChemPhysChem* **2006,** *7* (3), 551–554](https://doi.org/10.1002/cphc.200500559) (non-paywall version [here](https://userpage.fu-berlin.de/limbach/191.pdf)):
... |
Is it possible to use CI3TMS (a carbon with three iodo groups and a trimethylsilyl protecting group) and three equivalents of an ethyl grignard reagent to prepare 3-ethylpentan-3-ol? By deprotecting the product after the grignard reaction using tributylammonium fluoride, is it possible to produce the desired product? I... |
How do I solve this problem on Mole balance? |
I know how to use the standard addition equation for a single-point analysis from an equation I got from the Analytical Chemistry book "Quantitative Chemical Analysis" 9ed by D. Harris.
However, solving for a potentiometry problem, the equation doesn't seem to be effective anymore. I keep on getting negative value f... |
What is the equation for solving the concentration of the unknown from a Single-point Standard Addition Calibration for Potentiometry? |
I am trying to increase the final yield of acetylcholine (ACh) in my biofluid samples. I need to get the yield high enough for high confidence annotation of ACh (currently all I can really say is that I've got something that matches the ACh expected mz).
My first samples were prepared using C18 solid phase extracti... |
Chemistry newb here. I've been reading about how energy is released when new chemical bonds are formed but it's hard to find info on how that typically manifests itself (besides that it's via heat). I read somewhere that the valence electrons will move into lower energy orbits during a bond, but I thought that always... |
Chemistry newb here. I've been reading about how energy is released when new chemical bonds are formed but it's hard to find info on how that typically manifests itself (besides that it's via heat). I read somewhere that the valence electrons will move into lower energy orbits during a bond, but I thought that always... |
The neutralization reaction, such as $\ce{HCl + NaOH → NaCl + H2O}$, generates heat, which is around $\pu{57.30 kJ/mol}$.
**Can we use this energy to design a battery?**
This idea occurs in my mind for a long time.
----------------------------------------------------
---------- **Selection for Acid and Base** --... |
I know that an ether with a 3° alkyl group and a 1° alkyl group is cleaved by Sn1 mechanism to give a tertiary alkyl halide and a 1° alcohol. And an ether with a two 1° alkyl groups is cleaved by Sn2 mechanism to give a 1° alkyl halide and a 1° alcohol. But what happens if a ether with a 2° alkyl group and a 1° alkyl g... |
Chemistry newb here. I've been reading about how energy is released when new chemical bonds are formed but it's hard to find info on how that typically manifests itself (besides that it's via heat). I read somewhere that the valence electrons will move into lower energy orbits during a bond, but I thought that always... |
Let consider a steady state CSTR in which occurs the following reaction:
$$\ce{aA + bB \leftrightarrow cC}$$
----------
**Notations:**
$F_i$ is the molar flow of $i$, $r$ is the rate of reaction, $V$ is the volume, $X$ is the conversion at the end of the reactor, $\nu_i$ is the stoichiometric coefficient of... |
What are the equations giving the molar flow of different molecules linked by a reaction? |
I have some small cured epoxy shafts I am cutting segments out of for checking Tg by DSC. First scan gave a Tg of 118 C, follow on was 109 C. Scans were repeated on a new sample of the shaft with similar results.
250 F curing dicy based epoxy system.
Any idea why the first scan would be higher than the rescan? |
Why would the first Tg be higher than a rescan Tg of an epoxy by DSC? |
I have three chromatograms of the same eluted protein but at different concentrations and hense peak maximums at very different absorbances.
The highest is around 100 AU and lowest 20 AU.
I want to present these and look at the difference in peak shape (because I want to look at aggregation). Can I simply multiply ... |
Can I normalize my data in order to compare it? |
I have three chromatograms of the same eluted protein but at different concentrations, since it got diluted during purification process) and hence peak maximums at very different absorbances.
The highest is around 100 AU and lowest 20 AU.
I want to present these and look at the difference in peak shape (because I w... |
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