instruction stringlengths 15 21.8k |
|---|
In the (spontaneous) Raman process, incident light $\hbar \omega_1$ scatters and transfers some energy $\hbar \omega$ to a vibrational excitation of molecule or solid.
Typically this is a very rare process, and only happens to one of every $10^9$ photons or so. So even if a sample is irradiated with a ultrafast pum... |
Can stimulated Raman processes be strong enough to drive out of equilibrium? |
In the (spontaneous) Raman process, incident light $\hbar \omega_1$ scatters and transfers some energy $\hbar \omega$ to a vibrational excitation of molecule or solid.
Typically this is a very rare process, and only happens to one of every $10^9$ photons or so. So even if a sample is irradiated with a ultrafast pum... |
Why could it be assumed that the standard enthalpy change is independent of temperature down to 25C? |
Benzene is a part of Trypo AAs but in laboratory it is prepared by acetylene in contact with red hot copper tube. Needless to say such high temperatures are not feasible in cells than how are aromatic amino acids prepared ? |
Benzene in Amino Acids? |
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? |
Why could it be assumed that the standard enthalpy change is independent of temperature down to 25 °C? |
For the reversible reaction of pyruvic acid to 2,2-dyhrydypropanic acid, we calculated enthalpy using NMR and extrapolated from area (integration) and peaks etc.
We then plotted $\ln K$ vs $1/T.$ I am confused by this questions because I thought enthalpy was temperature dependent.
I guess my question was unclea... |
For the reversible reaction of pyruvic acid to 2,2-dyhrydypropanic acid, we calculated enthalpy using NMR and extrapolated from area (integration) and peaks etc.
We then plotted $\ln K$ vs $1/T.$ I am confused by this questions because I thought enthalpy was temperature dependent.
I guess my question was unclea... |
Let's consider a generic reaction:
$$\sum_{i=0}^{i=I}n_{i}A_{i} \rightarrow \sum_{j=0}^{j=J}m_{j}B_{j} $$
where $n$ and $m$ are the
stoichiometric coefficients, while $A$ and $B$ are reagents and products. In order to compute the enthalpy of this reaction we use the enthalpy of formation of each product and each re... |
The lone pair at the nitrogen is very well suited to form hydrogen bonds. This bond is especially strong, since ammonia has a quite high proton affinity, it is a medium strong base.
Now consider the autoprotolysis reactions in pure water and (liquid) ammonia:
\begin{align}
\ce{2H2O &<=> H3O+ + OH-}\tag1\\
\ce{2NH... |
How to get the enthalpy of a reaction from the enthalpy of formations with Hess' law? |
I was reading Solomon's Organic Chemistry and came across the Dissolving Metal Reduction of 4-Octyne to (E)-4-Octene. (The same as can be found [this question](https://chemistry.stackexchange.com/questions/18635/what-is-the-purpose-of-ammonium-chloride-in-anti-hydrogenation-of-alkynes))
But the book states that the ... |
Dissolving Metal Reduction of 4-Octyne to (E)-4-Octene and What Else? |
For a solution where many redox reactions occur (e.g. cytosol, soil solution), can we consider anything as 'overall' redox potential of a system? Is there a formula to quantify it in relation to the amount of each of the constituents? |
Is it possible to calculate the 'overall' redox potential of a system? |
**Target Equation:** Mg(s) + 1/2O2 --> MgO(s)
**1)** MgO(s) + 2HCl(aq) --> MgCl2(aq) + H2O(l) ΔH = -1300 kJ
**2)** Mg(s) + 2HCl(aq) --> MgCl2(aq) + H2(g) ΔH = -602 kJ
**3)** H2(g) + 1/2O2 --> H2O(l) ΔH = -286 kJ
The target equation should have a negative ΔH meaning that it's exothermic, but when I add it up, ΔH... |
**Target Equation:** $\ce{Mg(s) + 1/2O2 -> MgO(s)}$
1. $\ce{MgO(s) + 2HCl(aq) -> MgCl2(aq) + H2O(l)} \quad ΔH = \pu{-1300 kJ} \tag {1}$
2. $\ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)} \quad ΔH = \pu{-602 kJ} \tag {2}$
3. $\ce{H2(g) + 1/2O2 -> H2O(l)} \quad ΔH = \pu{-286 kJ} \tag {3}$
The target equation sho... |
Target equation: $\ce{Mg(s) + 1/2 O2 -> MgO(s)}$
$$
\begin{align}
\ce{MgO(s) + 2 HCl(aq) &-> MgCl2(aq) + H2O(l)} &\quad ΔH &= \pu{-1300 kJ} \tag{1}\\
\ce{Mg(s) + 2 HCl(aq) &-> MgCl2(aq) + H2(g)} &\quad ΔH &= \pu{-602 kJ} \tag{2}\\
\ce{H2(g) + 1/2 O2 &-> H2O(l)} &\quad ΔH &= \pu{-286 kJ} \tag{3}
\end{align}
$... |
Why do you add the three equations ?
By first adding (2) and (3) and then SUBSTRACTING (1), you find Mg + (1/2) O2 --> MgO.
On the other end, I think some of these numerical values are wrong, because one should obtain -602 kJ/mol, which is the heat of formation of MgO. And the combination of the given values d... |
For the reversible reaction of pyruvic acid to 2,2-dihydroxydypropanic acid, we calculated enthalpy using NMR and extrapolated from area (integration) and peaks etc.
We then plotted $\ln K$ vs $1/T.$ I am confused by this questions because I thought enthalpy was temperature dependent.
I guess my question was un... |
In the old fashioned process, we used buttermilk sugar and a bit of vanilla. We put them into a churn (which is just a small bucket with a mixing blade in it so you could hand mix the contents) and then added ice around the churn (outside the churn) to cool it down. And then you mixed and mixed and mixed and mixed. Bu... |
this is a dumb question but it's just slipping my mind on why this is done. so the question is to find the standard reduction potential of:
AgIO3 (s) + e- <-> Ag(s) + IO3- .
The Ksp is =3.1*10-8, and the standard reduction potential of Ag +e- <-> Ag(s) is E=0.799V.
(Not sure why exponents aren't working for me so... |
> Find the standard reduction potential of
> $$\ce{AgIO3(s) + e- <=> Ag(s) + IO3-}.$$
> $K_\mathrm{sp} = \pu{3.1E-8},$ and the standard reduction potential of $\ce{Ag +e- <=> Ag(s)}$ is $E = \pu{0.799 V}.$
So, $E^\circ$ will be standard reduction potential and $E$ will be the nonstandard.
$$
\begin{align}... |
I want to ask a question about peaks in a UV/VIS spectrum.
My lecturer in our introductory course mentioned the following:
> Two molecules may have the same molar extinction coefficient, but if I have two molecules, A and B, and B has a peak that is *broader* than molecule A, it will be a stronger absorber.
... |
Does broader peak mean stronger absorber in UV/VIS? |
I am supposed to say what is more basic and I ran into a problem. I would like to ask if anyone has any idea what is the correct $\mathrm{p}K_\mathrm{a}\ce{H}$ value of pyrrole. I know it is easy to just google it or open a book to find the answer. I have done that, but got pretty interesting (confusing?) results:
... |
What is the pKaH of pyrrole? |
I am supposed to say what is more basic and I ran into a problem. I would like to ask if anyone has any idea what is the correct $\mathrm{p}K_\mathrm{a}\ce{H}$ value of pyrrole. I know it is easy to just google it or open a book to find the answer. I have done that, but got pretty interesting (confusing?) results:
... |
Hi I am trying to figure out the mechanism of a reaction containing a lithium carbanion and 1,2-dibromoethane in THF. The lithium carbanion is generated by deprotonating using LDA. Then 1,2-dibromoethane is added to get the desired product (see image)
[![enter image description here][1]][1]
I think that the carbani... |
How does electrophilic bromination with 1,2-dibromoethane work? |
Hi I am trying to figure out the mechanism of a reaction containing a lithium carbanion and 1,2-dibromoethane in THF. The lithium carbanion is generated by deprotonating using LDA. Then 1,2-dibromoethane is added to get the desired product (see image)
[![enter image description here][1]][1]
I think that the carbani... |
[What is the difference between dish soap, handsoap, body wash and shampoo? And can they all be used interchangably? : NoStupidQuestions](https://old.reddit.com/r/NoStupidQuestions/comments/3tlmbu/what_is_the_difference_between_dish_soap_handsoap/)
> Dish soap is focused on your dishes, as the name implies. It is me... |
Op's question is what is the correct $\mathrm{p}K_\mathrm{a}\ce{H}$ value of pyrrole. Thus, I'm not going to elaborate OP's findings, but would try to give a reasonable answer to the question. The most reasonable answer I found for $\mathrm{p}K_\mathrm{a}\ce{H}$ value for the pyrrole is $0.4$ (for the novices, this is ... |
Op's question is what is the correct $\mathrm{p}K_\mathrm{a}\ce{H}$ value of pyrrole. Thus, I'm not going to elaborate OP's findings, but would try to give a reasonable answer to the question. The most reasonable answer I found for $\mathrm{p}K_\mathrm{a}\ce{H}$ value for the pyrrole is $0.4$ (for the novices, this is ... |
Why acidity of p methoxybenzoic acid is more acidic than p hydroxy benzoic acid? |
Yes, in principle it could be different, but the effect would be very small unless the increase in pressure were very large. To put it in simplified terms: The increase in ambient pressure compresses the liquid, bringing it to a higher-energy state, causing a higher proportion of the liquid molecules to want to escap... |
Op's question is what is the correct $\mathrm{p}K_\mathrm{a}\ce{H}$ value of pyrrole. Thus, I'm not going to elaborate OP's findings, but would try to give a reasonable answer to the question. The most reasonable answer I found for $\mathrm{p}K_\mathrm{a}\ce{H}$ value for the pyrrole is $0.4$ (for the novices, this is ... |
I know +M effect of $\ce{OCH3}$ is more than $\ce{OH}$, but in my book, it is given that $\mathrm{p}k_\mathrm{a}$ of *para*-substituted benzoic acid containing $\ce{OCH3}$ is less than that of *para*-substituted benzoic acid containing $\ce{OH}$. I... |
Why acidity of p-methoxybenzoic acid is more acidic than p-hydroxybenzoic acid? |
Why *m*-hydroxybenzoic acid has higher acidity than *p*-hydroxybenzoic acid?
I have a reasoning that since hydroxy group is an activating group, then it increases the electron density on its para position. So for *p*-hydroxybenzoic acid, the carbonyl carbon has a greater ability to share molecular orbital's elect... |
> Why is *ortho*-hydroxybenzoic acid $(\mathrm{p}K_\mathrm{a} = 2.98)$ more acidic than its *para*-isomer $(\mathrm{p}K_\mathrm{a} = 4.58)$?
March's Advanced Organic Chemistry (7th ed) gives the reason to be intramolecular hydrogen bonding between the $\ce{OH}$ and $\ce{COO-}$ groups of the conjugate base.
Howe... |
Why is ortho-hydroxybenzoic acid more acidic than its para-isomer? |
We know that in case of halogens, inductive effect is more dominant than resonance effect. So, the -$\ce{Cl}$ on the para position will withdraw electrons by a -I effect and should make *p*-chlorobenzoic acid more acidic than benzoic acid. But why is it not so? Am I missing something? |
Where are you getting your information? So far as I can find, 4-chlorobenzoic acid has a $\mathrm{p}K_\mathrm{a}$ of $3.98$ and benzoic is $4.2$. |
In the (spontaneous) Raman process, incident light $\hbar \omega_1$ scatters and transfers some energy $\hbar \omega$ to a vibrational excitation of molecule or solid.
Typically this is a very rare process, and only happens to one of every $10^9$ photons or so. So even if a sample is irradiated with a ultrafast pum... |
I know +M effect of $\ce{OCH3}$ is more than $\ce{OH}$, but in my book (ALLEN *General organic chemistry*), it is given that $\mathrm{p}K_\mathrm{a}$ of *para*-substituted benzoic acid containing $\ce{OCH3}$ is less than that of *para*-substituted benzoic acid containing $\ce{OH}$:
> $\mathrm{p}K_\mathrm{a}$/Benzoic... |
While talking about ionic bonds my book states :
>Higher the value of electron gain enthalpy of the atom, greater the ease of formation of the anion from it, i.e., other atom should have high value of electron gain enthalpy.
Now I think it should say *more* negative than *higher* (as negative enthalpy means relea... |
What does higher electron gain enthalpy mean here? |
While talking about ionic bonds my book states :
>Higher the value of electron gain enthalpy of the atom, greater the ease of formation of the anion from it, i.e., other atom should have high value of electron gain enthalpy.
Now I think it should say ***more negative *** than just ***higher*** (as negative enthal... |
Hi I am trying to figure out the mechanism of a reaction containing a lithium carbanion and 1,2-dibromoethane in THF. The lithium carbanion is generated by deprotonating using LDA. Then 1,2-dibromoethane is added to get the desired product (see image)
[![enter image description here][1]][1]
I think that the carbani... |
While talking about ionic bonds my book states :
>Higher the value of electron gain enthalpy of the atom, greater the ease of formation of the anion from it, i.e., other atom should have high value of electron gain enthalpy.
Now I think it should say ***more negative*** than just ***higher*** (as negative enthalp... |
For example, can crystal iodine dissolved in ethanol react with sodium thiosulfate dissolved in water? |
Can compounds dissolved in different miscible solvents react? |
In the entire book, perturbation theory is used as a qualitative tool to rationalise some chemical phenomena. The authors write that
[![enter image description here][1]][1]
The proof of the derivation for $T_{ji}$ involves the following statement:
[![enter image description here][2]][2]
where
[![ent... |
For example, can crystal iodine dissolved in ethanol react with sodium thiosulfate dissolved in water when mixed together? |
In the entire book, perturbation theory is used as a qualitative tool to rationalise some chemical phenomena. The authors write that
$$\psi_i = \sum_\mu{T_{ji}\psi_j^\circ}\tag{1}$$
The proof of the derivation for $T_{ji}$ involves the following statement:
$$T_{ji} = \left(\mathbf{C}_j^\circ\right)^\mathrm{T}\... |
In the entire book, perturbation theory is used as a qualitative tool to rationalise some chemical phenomena. The authors write that
$$\psi_i = \sum_\mu{T_{ji}\psi_j^\circ}\tag{1}$$
The proof of the derivation for $T_{ji}$ involves the following statement:
$$T_{ji} = \left(\mathbf{C}_j^\circ\right)^\mathrm{T}\... |
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/xQbei.png
How is the redox couple as it is written for the oxidation of MnO4-, as MnO4-,H+/Mn2+,H2O correct?
I agree that MnO4 is being oxidized as it loses electrons (going from -1 charge to +2) but I dont see why H+ is also being oxi... |
As in other posts I have seen and learnt that, if one is given four compounds, namely *para*-nitrophenol, *ortho*-nitrophenol, *meta*-nitrophenol and phenol and is told to arrange them in order of acidity, then one has to take into account the -R and -I effect.
Now, for the inductive effect, the greatest intensity i... |
I have no idea of chemistry, just a little bit what I know from school, but I found through some search some connection between entropy (Shannon entropy) of the divisors of some natural numbers and the Madelung constants.
My question is this:
Are these numbers Madelung constants?
1 -0.000000000000000
... |
Are these numbers Madelung constants? |
As in other posts I have seen and learnt that, if one is given four compounds, namely *para*-nitrophenol, *ortho*-nitrophenol, *meta*-nitrophenol and phenol and is told to arrange them in order of acidity, then one has to take into account the $\text{-R}$ and $\text{-I}$ effect.
Now, for the inductive effect, the gr... |
In my chemistry textbook, there is a table of the molar volumes for different gases. Most of them are below 22.42 l/mol, the ideal gas molar volume, but I noticed that hydrogen and helium do not. Hydrogen is 22.433 l/mol and helium is 22.434 l/mol. Why is this? What makes these particles, with mass, have higher molar v... |
In the (spontaneous) Raman process, incident light $\hbar \omega_1$ scatters and transfers some energy $\hbar \omega$ to a vibrational excitation of molecule or solid.
Typically this is a very rare process, and only happens to one of every $10^9$ photons or so. So even if a sample is irradiated with a ultrafast pum... |
In most types of batteries, primary and secondary, the metallic electrode is the anode, and a non-metal acts as cathode. Or a pure metal is the anode, and the cathode is a metal oxide.
Why is the opposite true in a lithium-ion battery? |
Why is the cathode of a lithium-ion battery metallic, which is the opposite of most other batteries? |
The graphene oxide solution was made from electrolytic exfoliation of graphite electrodes in a 10M NaOH solution. Some graphene powder deposited on the bottom of the recipient but a brownish solution remained, even after the powder settled. Graphene oxide is believed to be the source of the brown color.
The solution ... |
How do I separate a graphene/graphite oxide and NaOH solution without centrifugation? (filtration didn't work) |
I have small amount of rosemary herb powder mixed in a cup of water and it's only party dissolving. I was wondering if there is another powder that can be added to this water solution and dissolve the rosemary completely? |
Most elements are or have compounds that are gases or have a significant vapor pressure at room temperature. Carbon dioxide and [tungsten hexafluoride][1] are gaseous at room temperature despite being made using elements with extremely high melting/boiling points.
Organometallics such as [iron pentacarbonyl][2] and ... |
Most elements are or have compounds that are gases or have a significant vapor pressure at room temperature. Fluoride is a powerful tool for producing highly oxidized covalent and volatile compounds. [Tungsten hexafluoride][1] is gaseous at room temperature despite being made with the element with the highest melting a... |
Most elements are or have compounds that are gases or have a significant vapor pressure at room temperature. Fluoride is a powerful tool for producing highly oxidized covalent and volatile compounds. [Tungsten hexafluoride][1] is gaseous at room temperature despite being made with the element with the highest melting a... |
In my lab guide I readed: "Use a $0.1$ N solution of methanol-chloridic acid $(9:1)$ for the antocianin extraction" so, I tried to calculate the volume of $CH_3OH$ and $HCl$ to prepare it... but I don't know how to do it. I mean, if I push one mole of $CH_3OH$ and one mole of $HCl$ in 1 liter of water, I make a 2 molar... |
In my lab guide I read: "Use a $\pu{0.1 N}$ solution of methanol-chloridic acid $(9:1)$ for the anthocyanin extraction", so I tried to calculate the volume of $\ce{CH3OH}$ and $\ce{HCl}$ to prepare it, but I don't know how to do it. I mean, if I push one mole of $\ce{CH3OH}$ and one mole of $\ce{HCl}$ in $\pu{1 liter}$... |
Is it possible to prepare a 0.1 N solution of HCl and methanol? |
As Mirhoron says in the comments, tert-butyllithium is one choice. Like all pure organolithium compounds, this is **pyrophoric** and reactive to many common atmospheric gases or vapors. [This post from UCLA](https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.chemistry.ucla.edu/sites/default/files/safety... |
As Mithoron says in the comments, tert-butyllithium is one choice. Like all pure organolithium compounds, this is **pyrophoric** and reactive to many common atmospheric gases or vapors. [This post from UCLA](https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.chemistry.ucla.edu/sites/default/files/safety... |
Appreciate if anyone could help me understand this: at Eutectic point, there 3 phases: solid A, solid B and homogenous liquid phase containing both A and B.
But at consolute point, we are told it has 2 phases: liquid A and liquid B.
My question: why isn't there a homogenous phase containing both liquid A and B ... |
Eutectic point has 3 phases but consolite point has 2 phases, why? |
What does "parallel in-register" mean for a protein structure in a fibril? |
Most elements are or have compounds that are gases or have a significant vapor pressure at room temperature. Fluoride is a powerful tool for producing highly oxidized covalent and volatile compounds. [Tungsten hexafluoride][1] is gaseous at room temperature despite being made with the element with the highest melting a... |
I have no idea of chemistry, just a little bit what I know from school, but I found through some search some connection between entropy (Shannon entropy) of the divisors of some natural numbers and the Madelung constants.
My question is this:
Are these numbers Madelung constants?
1 -0.000000000000000
... |
By what i understand by assigning the priority the parent is the ketone.
Now if i number carbonyl carbon as 1 then i should move towards the alcohol group because it has higher priority than the alkene and both are at number 3 so the alcohol shoul... |
What is the IUPAC name of the given compound? |
At eutectic point, there are three phases: solid A, solid B and homogenous liquid phase containing both A and B.
But at consolute point, we are told it has 2 phases: liquid A and liquid B.
Why isn't there a homogenous phase containing both liquid A and B at consolute point just like an eutectic point? |
Why does eutectic point has three phases, but consolute point has two phases? |
> IUPAC name of the given compound is
> [![enter image description here][1]][1]
> (1) 3-Hydroxycyclohex-4-en-1-one
> (2) 5-Hydroxycyclohex-3-enone
> (3) 5-Ketocyclohex-2-enol
> (4) 3-Ketocyclohex-5-enol
By what I understand by assigning the priority the parent is the ketone.
If I number carbonyl carb... |
As per my knowledge if i start numbering the compound from the alcohol then to mercapto group then alkene group.
So according to me the numbering should be from bottom alcohol as number 1 and making the way to the top alcohol as number 3. Then... |
What should be the name of the given compound? |
> Following compound is named as
> [![enter image description here][1]][1]
> (1) 6-Mercaptocyclohex-4-ene-1,3-diol
> (2) 1-Mercaptocyclohex-2-ene-4,6-diol
> (3) 1-Mercaptocyclohex-5-ene-2,4-diol
> (4) 4-Mercaptocyclohex-2-ene-1,5-diol
As per my knowledge if I start numbering the compound from t... |
We performed two experiments. Each of the peaks are reffering to the methyl peaks in both reactant and product of the hydrolysis reaction.
1. We varied H+ concentration of the reaction and the peaks move ever so slightly right (up field) as acid concentration increases. Why?
2. We varied temperature (45, 50, 55... |
Why do the NMR peaks shift when H+ concentration and temperature are varied on the reversible hydrolysis of pyruvic acid to 2,2-dihydroxypropionate? |
We performed two experiments. Each of the peaks are reffering to the methyl peaks in both reactant and product of the hydrolysis reaction.
1. We varied H+ concentration of the reaction and the peaks move ever so slightly right (up field) as acid concentration increases. Why?
As more acid is added there is more ... |
I have this reaction:
A + 4,5B → C + 2D + 2E (Reaction 1)
C + 7,5B → 8D + 2E (Reaction 2)
Does the volume change when the reactions has occured?
Because if so, the concentration changes too, right?
|
Does the volume change when the reactions occur? |
I have this reaction(all substances are gaseous):
A + 4,5B → C + 2D + 2E (Reaction 1)
C + 7,5B → 8D + 2E (Reaction 2)
Does the volume change when the reactions has occured?
Because if so, the concentration changes too, right?
|
I have this reaction (all substances are gaseous):
$$
\begin{align}
\ce{A + 4.5 B &→ C + 2 D + 2 E}\tag{R1}\\
\ce{C + 7.5 B &→ 8 D + 2 E}\tag{R2}
\end{align}
$$
Does the volume change when the reactions has occurred?
Because if so, the concentration changes too, right?
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.