instruction stringlengths 15 21.8k |
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User permeakra's observation is right, but the inference is not. User Wildcat's answer is spot-on, but missed on one minor point, which I would explain at the end.
This is just a summary of Wildcat's explanation: The idea is that, we have a system comprising of indistinguishable fermions, which is why we need to use... |
In my research we have a method of making polymer open-cell foams with high tortuosity and pore sizes on the order of 50-200 nanometers. I can make thicknesses of 100 micron to 2 mm thick (and up to 5 inch diameter disk). I am looking for some cool things to do with this material, and one idea was to try to fill it wit... |
With higher period the d-electrons of the metal are less strong bonded and therefore oxidative addition is easier for $\ce{Ir(I)}$ than for $\ce{Rh(I)}$ and much easier than for $\ce{Co(I)}$.
For metal carbonyl hydride: electrons with higher period ($5d$) are stronger bound to the nucleus, so $\ce{pK}_{a}$ is increa... |
Studying biochemistry I noticed that equilibrium is reached for K and Na separately (not taking into account electric potential), as would be the case I assume for any molecule or atom. This is of course entropy.
Eg: My understanding is, you have two types of atoms, and a membrane separating them, with different con... |
Why does diffusion work in presence of similar atoms? |
With higher period the d-electrons of the metal are less strong bonded and therefore oxidative addition is easier for $\ce{Ir(I)}$ than for $\ce{Rh(I)}$ and much easier than for $\ce{Co(I)}$.
For metal carbonyl hydride: electrons with higher period ($5d$) are stronger bound to the nucleus, so $\mathrm{p}K_\mathrm{a}... |
In my research we have a method of making polymer open-cell foams with high tortuosity and pore sizes on the order of 50–200 nanometers. I can make thicknesses of 100 µm to 2 mm thick (and up to 5 inch diameter disk). I am looking for some cool things to do with this material, and one idea was to try to fill it with me... |
Average or individual molar heat capacity? |
![enter image description here][1]
[1]: https://i.stack.imgur.com/nJzG7.jpg
Edited to combine each question in one picture, so I can just ask my question here.
Okay.
I've spent a few days googling functional groups and reading my text assigned on organic functional groups. I'm understanding very littl... |
> Nomenclature priorities are in order of the degree of oxidation of the
> carbon atom.
I am not sure if it's advisable to just take it as it is and use it or try to understand the basis of the functional group prioritization. I guess the latter interest me. So looking at the priorities for functional groups,
A... |
Oxidation of Carbon atom in Alkene, Alkyne and Alkanes of functional groups? |
Nanotechnology and sciences are the study or the manipulation of matter on an atomic, molecular, and supramolecular scale especially at nano meter range. We know that at macro molecular level a system can be described using Newtonian/classicl mechanics (eg: $F=ma$) whereas for electronic level quantum mechanics were us... |
Nanotechnology and sciences are the study or the manipulation of matter on an atomic, molecular, and supramolecular scale especially at nano meter range. We know that at macro molecular level a system can be described using Newtonian/classical mechanics (eg: $F=ma$) whereas for an electronic level quantum mechanics are... |
I think that the ginger ale is born this way.
Anyway, if you put the ginger in a glass and add sparkling water, small drops splash out of the glass, the water is fizzier, more effervescent.
Why? what makes the two of them react? |
Why ginger reacts with sparkling water? |
The fluorescence quantum yield of a sample $\Phi$ is defined as the fraction of photons emitted per number of photons absorbed. The quantum yield is often calculated by comparing a sample with a reference substance of known quantum yield $\Phi_r$ such that
$$
\Phi=\Phi_r\times\frac{n^2}{n_r^2}\times\frac{I}{I_r}\tim... |
Which substances exist that are normally liquid and that will not freeze nor boil even at relatively low/high temperatures as compared to the freezing and boiling points of water? Or how can I identify such substances online?
If it is relatively non-reactive, non-toxic, cheap and has high thermal conductivity that i... |
The fluorescence quantum yield of a sample $\Phi$ is defined as the fraction of photons emitted per number of photons absorbed. The quantum yield is often calculated by comparing a sample with a reference substance of known quantum yield $\Phi_\mathrm{r}$ such that
$$
\Phi=\Phi_\mathrm{r}\times\frac{n^2}{n_\mathrm{r... |
Great question, but unfortunately without a great answer. Chemistry is very inconsistent in its naming of phosphates. In addition to the terms _diphosphate_ and _pyrophosphate_, the term _bisphosphate_ is also used.
Someone will probably put in an answer that cites "official" IUPAC or [IUBMB](http://www.iubmb.org/... |
Great question, but unfortunately without a great answer. Chemistry is very inconsistent in its naming of phosphates. In addition to the terms _diphosphate_ and _pyrophosphate_, the term _bisphosphate_ is also used.
Someone will probably put in an answer that cites "official" IUPAC or [IUBMB](http://www.iubmb.org/... |
To explain the [characteristic X-ray][1] emission peaks for various elemental targets, a formula was developed which was similar in construct to the Rydberg equation for H-atom as derived by the Bohr-model.
$$\tilde\nu=R\left(\frac{1}{n_\mathrm{f}^2}-\frac{1}{n_1^2}\right)\left(Z-\sigma\right)^2$$
where $\tilde... |
Understanding Moseley’s law from the Rydberg-type equation? |
> In finding enthalpy change $\Delta H$ during adiabatic, reversible expansion of mixture of two ideal gases $n_1$ mol of $\ce{A}$ ($C_{\mathrm{m},v}=\frac{3}{2}R$) and $n_2$ mol of $\ce{B}$ ($C_{\mathrm{m},v}=3R$) taken in a container and during this temperature change is $T_\mathrm{i}$ to $T_\mathrm{f}$. Then what s... |
Does ethanol react with potassium to form potassium ethanolate and hydrogen gas? |
Gallium melts at 30 °C but doesn't boil until 2200 °C. If 30 °C is a bit too warm to count as "room temperature" or "normally" for you, I found an [old paper](http://pubs.acs.org/doi/pdf/10.1021/je60009a029) that recommends tetralkyl silanes such as tetradodecyl silane as lubricants that are liquid over ve... |
Would I have any success putting coffee in a humidifier? Or perhaps water mixed with caffeine powder?
So I could wake up without a jolting alarm clock, feeling like I already had a cup of coffee?
I understand this will have to be a carefully controlled dose if working with caffeine powder, but is it feasible? |
Can I successfully use a humidifier to distribute caffeine to wake someone up without the usual morning drowsiness? |
According to this [MSDS](http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=C0750&brand=SIAL&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Fsial%2Fc0750%3Flang%3Den), there are several problems with your proposal.
I recommend [this](http://www.chemex... |
I was under the impression that differences between the various long range electrostatic algorithms, ewald, PME, PPPM, to name a few, lied solely in their treatment of the reciprocal space term. Specifically, I thought all methods looped over a particles neighbor and summed q(i)*q(j)*erfc(alpha*r)/r for the real space ... |
I know that NO2 has 3 effective pairs, so it is likely to have trigonal planar structure. In trigonal planar structure we usually see three atoms bonded to central atom at 120°. But in NO2-, I observe that though it has three effective pairs, but still, it is not having the desired structure, with only 2 O atoms bon... |
What is the structure of NO2-? |
I've noticed that water soluble fertilizers tend to be blue. What chemicals or chemical reactions cause this color here? Is this necessary or for aesthetic purposes? I haven't seen this in organic fertilizers. I figured chemists might be able to examine the ingredients of Miracle Grow or something and tell me. I'm gues... |
What makes many water soluble fertilizers blue? |
What is the meaning of $\ce{(en)}$ on this two coordination compounds:
$\ce{[Co(en)_2(NO_2)_2]Cl}$
<br>
$\ce{[Cd(en)_2(CN)_2]}$
Is it a type of compound? If yes, what is the meaning? |
Recently I was watching a video on *Valence Bond Theory*, on the *MIT Open-Course* youtube channel. The teacher there said that
> For hybridization to occur, electron promotion from fully filled orbitals to empty ones is a must.
But here in a book it is specifically mentioned that
> Electron promotion, though ... |
I am looking for the precise definitions, as I am very confused as to what they are exactly, because although I mostly understand what they mean, I have encountered some conflicting definitions that confused me.
As it stands, this is what I understand them to mean:
> - Compound: two or more different atoms bonde... |
According to Wikipedia Caesium's density is $1,90 \frac{g}{cm^3}$ at $\Theta =20 °\mathrm{C}$. How does this change when T changes? E.g. will it expand when melting? |
Sucrose does melt at $366.8°\mathrm{F}$. It decomposes once you get to hotter temperatures, which is why caramel darkens till it becomes burnt sugar. Thus unlike sodium chloride and most other substances sucrose and lots of other sugars from trioses upwards in # of C's don't have a boiling point, just a melting point b... |
According to Wikipedia caesium’s density is $1.90\ \mathrm{g/cm^3}$ at $\Theta =20\ \mathrm{^\circ C}$. How does this change when $T$ changes? E.g. will it expand when melting? |
How does caesium’s density change with temperature? |
Question is simple.. If we take an atom of any element and then supply heat energy to it then what will happen?
What I thought is that in the beginning, energy (quanta; due to excitement of electron and then moving back to ground state) should be evolved and then electron should be emitted... Am I right? |
> Is there any extra force holding the two components together?
**Correct. Namely, hydrogen bonding.** As a quick refresher, hydrogen bonding is an electrostatic attraction between an electropositive hydrogen atom on one compound being (weakly) attracted to a highly electronegative atom on a... |
>What chemicals or chemical reactions cause this color here? Is this necessary or for aesthetic purposes?
I have some Miracle Gro on hand, the water soluble kind: The blue stuff is copper sulfate, or ${\rm CuSO}_{4}$. [Here](http://eldoradochemical.com/MSDS_Sheets/EDC/Third_Party_Products/MIRACLE_GRO_ALL_PURPOSE_PLA... |
$\ce{H-H}$ bond enthalpy is 436 kJ/mol. To break apart a mole of $\ce{H2}$ into H atoms, I apparently need to heat it by 436 kJ.
Does this only apply at the standard temperature of 298 kelvin?
What about $\ce{H2}$ gas (or liquid) at 0 K?
$\ce{H2}$ gas at 500 K?
Does the bond enthalpy vary with temperature? ... |
How can I use sunlight to heat a RBF and reflux a reaction? |
Well apart from the fact that the answer depends on the type of the paper that is used. Secondly how much is wasted and also the process used. Below is an article that might be helpful in answering the question
>Some industry sources estimate that an ordinary sheet of paper made from cellulose fibers derived from wo... |
Hi I need help calculating the conc. of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; log(NaF) (mol/L) vs EMF:
y = 59.8x +600.8
0.7540 g of toothpaste was diluted in 50 mL and tested to obtain a EMF value of 390. what is the ppm of F- in 198 g of toothpaste? |
I need help calculating the concentration of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}:
y = 59.8x +600.8$$
$0.7540~\mathrm{g}$ of toothpaste was diluted in $50~\mathrm{mL}$ and tested to obtain a EMF value of $390... |
Hi I need help calculating the conc. of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; log(NaF) (mol/L) vs EMF:
y = 59.8x +600.8
0.7540 g of toothpaste was diluted in 50 mL and tested to obtain a EMF value of 390. what is the ppm of F- in 198 g of toothpaste?
I plugged i... |
Hi I need help calculating the conc. of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; log(NaF) (mol/L) vs EMF:
y = 59.8x +600.8
0.7540 g of toothpaste was diluted in 50 mL and tested to obtain a EMF value of 390. what is the ppm of F- in 198 g of toothpaste?
I plugged i... |
Hi I need help calculating the conc. of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; log(NaF) (mol/L) vs EMF:
y = 59.8x +600.8
0.7540 g of toothpaste was diluted in 50 mL and tested to obtain a EMF value of 390. what is the ppm of F- in 198 g of toothpaste?
I plugged i... |
I need help calculating the concentration of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}:
y = 59.8x +600.8$$
$0.7540~\mathrm{g}$ of toothpaste was diluted in $50~\mathrm{mL}$ and tested to obtain a EMF value of $390... |
I need help calculating the concentration of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}:
y = 59.8x +600.8$$
$0.7540~\mathrm{g}$ of toothpaste was diluted in $50~\mathrm{mL}$ and tested to obtain a EMF value of $390... |
Following acetal aldole gives no selectivity. The question is why?
![enter image description here][1]
For the related propionate aldole we can draw two (considering R of aldehyde to be equatorial) possible transition states:
![enter image description here][2]
[1]: https://i.stack.imgur.com/lntJ1.png
... |
Why does acetale aldol gives no selectivity? |
Following acetate aldole gives no selectivity. The question is why?
![enter image description here][1]
For the related propionate aldole we can draw two (considering R of aldehyde to be equatorial) possible transition states:
![enter image description here][2]
[1]: https://i.stack.imgur.com/lntJ1.png
... |
Why does acetate aldol gives no selectivity? |
Why does acetate aldol gives no selectivity? |
Following acetate aldol gives no selectivity. The question is why?
![enter image description here][1]
For the related propionate aldol we can draw two (considering R of aldehyde to be equatorial) possible transition states:
![enter image description here][2]
[1]: https://i.stack.imgur.com/lntJ1.png
[... |
Following acetate aldol gives no selectivity. The question is why?
![enter image description here][1]
For the related propionate aldol we can draw two (considering R of aldehyde to be equatorial) possible transition states:
![enter image description here][2]
(As a side-note:
In practice chlorine is used in... |
Following acetate aldol gives no selectivity.
![enter image description here][1]
For the related propionate aldol we can draw two (considering R of aldehyde to be equatorial) possible transition states:
![enter image description here][2]
The question is why we don't get good selectivity if we compare the a... |
You can memorize the periodic table in one night, simply by emulating best-practice memorization techniques and doing what memory experts do. Common sense, right?
Memory experts and world champion memory ‘athletes’ activate the enormous natural power of their visual memory by using visualization and association mne... |
I'm looking at a chart in my book, and while cycloheptane has a higher boiling point than cyclohexane like I'd expect, cycloheptane has a melting point of -12 *C, while cyclohexane has a melting point of 6.6 *C. Why does it have a lower melting point only? |
How many electrons can have the quantum number set n=6, l=3, and ml=-1?
Also, please explain why. I know that n describes the number of shells in an atom but what do n,l, and ml have to do with electrons? |
How many electrons can have the quantum number set n=5 and l=0? |
There are not many reputable sources on the matter (as I could find) since it seems that cycloheptane isn't the most popular chemical around (poor guy) but I will present you with the best explanation/argument/insight into the situation as I can.
*Note that it would be solely my own interpretation, and a case of ex... |
Can anyone explain the shapes of ionic compound? What does it mean? What does the Coordinate number means? I have known that in NaCl, one Na atom is surrounded by 6 Cl atoms, and vice versa, but can it be explained with the help of Co ordinate numbers? |
Which are the elements of the Twofold Screw Axis in this image?
The "+" and "-" elements that intercept the red line are the elements of the Twofold Screw Axis 2/3?
And if so, is the height of the red line 2/3 plus or 2/3 minus?
But why the height of the red line is 2/3?
I have the same problem with the oth... |
I've noticed that water soluble fertilizers tend to be blue. What chemicals or chemical reactions cause this color here? Is this necessary or for aesthetic purposes? I haven't seen this in organic fertilizers. I figured chemists might be able to examine the ingredients of Miracle Gro or something and tell me. I'm guess... |
I’m looking at a chart in my book, and while cycloheptane has a higher boiling point than cyclohexane like I’d expect, cycloheptane has a melting point of −12 °C, while cyclohexane has a melting point of 6.6 °C. Why does it have a lower melting point only? |
I need help calculating the concentration of fluoride in toothpaste. Thanks in advance.
A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}:
y = 59.8x +600.8$$
$0.7540~\mathrm{g}$ of toothpaste was diluted in $50~\mathrm{mL}$ and tested to obtain a EMF value of $390... |
>Given that $K_{\mathrm{sp}}(\ce{CaF2})=3.2\cdot 10^{-11}$, $K_{\mathrm{a}}(\ce{HF})=10^{-5}$, and $K_{\mathrm{w}}=10^{-14}$.
>Calculate $\mathrm{pH}$ of saturated $\ce{CaF2}$.
Here is my approach,
$$\ce{CaF2 -> Ca^2+ +2F-}$$
\begin{align}
K_{\mathrm{sp}} &=[\ce{Ca^2+}] \cdot [\ce{F-}]^{2}\\
K_{\mathrm{sp}}... |
A handy guide to visualise and explain the chemical differences between tetrahedron and trigonal pyramid geometries comes from the [The Nobel Prize in Chemistry 1971: Gerhard Herzberg][1] page:
![enter image description here][2]
There is a handy explanation of the geometries in a YouTube clip referenced to Grand ... |
Would isolated silicon engage in network covalent bonding as quartz does or would it engage in a different kind of bonding? Would germanium display similar qualities?
- I am asking what is the bonding of silicon, not why silicon is different from carbon.
- I am interested in isolated silicon, not silicon as a "hy... |
The shapes respectively denoted by '**tetrahedron**' and '**trigonal pyramid**' seem to be the same. Is there a difference between the two? If not, why are the two presented as different concepts in introductory chemistry courses? |
What's the difference between a tetrahedron and a trigonal pyramid? |
Following acetate aldol gives no diasteroselectivity:
![enter image description here][1]
Because I don't know what's the basis of above statement (I heard it in lecture and read it in some internet web pages) I expect the two products are formed racemic.
For the related propionate aldol we can draw two (consid... |
Why does acetate aldol with Evans auxiliary gives almost no diasteroselectivity? |
In the following question, the [water/wine mixing problem](https://en.wikipedia.org/wiki/Wine/water_mixing_problem) was recast in chemical terms. However, [partial molar volumes](https://en.wikipedia.org/wiki/Partial_molar_property) can make this a much more challenging problem than it appears on the surface.
http:... |
How is spiro nonatetraene antiaromatic? I know that spiro compounds exhibit homoaromaticity, but how do they exhibit antiaromaticity?
![enter image description here][1]
[1]: https://i.stack.imgur.com/AiysL.png |
How many electrons can have the quantum number set $n=6,\ l=3,\ m_l=-1$?
Also, please explain why. I know that n describes the number of shells in an atom but what do n, l, and ml have to do with electrons? |
How many electrons can have the quantum number set n=5, l=3, ml=-1? |
The orbital interaction between the 2 butadiene units in spiro[4.4]nonatetraene is referred to as **spiroconjugation**. Note that the 2 rings attached through the common or **spiro** carbon are perpendicular to one another. Each cyclopentadiene ring contains a 1,3-butadiene unit. In the figure below, I've drawn in t... |
How is spiro[4.4]nonatetraene antiaromatic? I know that spiro compounds exhibit homoaromaticity, but how do they exhibit antiaromaticity?
![enter image description here][1]
[1]: https://i.stack.imgur.com/AiysL.png |
The orbital interaction between the 2 butadiene units in spiro[4.4]nonatetraene is referred to as **spiroconjugation**. Note that the 2 rings attached through the common or **spiro** carbon are perpendicular to one another. Each cyclopentadiene ring contains a 1,3-butadiene unit. In the figure below, I've drawn in t... |
Following acetate aldol gives no diasteroselectivity:
![enter image description here][1]
Because I don't know what the basis of above statement is (I heard it in a lecture and read it on some internet web pages). I expect the two products are formed racemic.
For the related propionate aldol we can draw two (co... |
Why does acetate aldol with Evans auxiliary give almost no diasteroselectivity? |
Can anyone explain the shapes of ionic compounds? What does it mean? What does the coordinate number mean? I know that in $\ce{NaCl}$, one $\ce{Na}$ atom is surrounded by 6 $\ce{Cl}$ atoms, and vice versa, but can it be explained with the help of coordinate numbers? |
Sucrose decomposes at 186 °C. It doesn’t melt but when it reaches decomposition temperature, sucrose decomposes into fructose and glucose.
After cooling and hardening it is no longer sucrose. Am I right? |
So, I have 1 litre of acetate buffer, and 0.1 mol of oxonium ions/$\ce{H3O+}$ is added. The task is to calculate the pH of this solution.
What I was thinking:
$$\ce{CH3COOH + H2O <=> CH3COO- + H3O+}$$
$$\mathrm{pH} = \mathrm{p}K_\mathrm{a} + \log\frac{c(\ce{Ac-})}{c(\ce{HAc})} = \mathrm{p}K_\mathrm{a} + \log\fra... |
$\ce{SnF2}$ appears to have a predominantly covalent structure while $\ce{NaF}$ is ionic. So I think $\ce{SnF2}$ might release fluoride ions slower (more reluctantly) than $\ce{NaF}$.
Since toothpaste contains $\ce{Ca}$ containing minerals as well (as mentioned in the Wikipedia page), highly insoluble $\ce{CaF2}$ is... |
Looking at the electronegativities in the Periodic Table (below, from [ChemWiki][1]):
![enter image description here][2]
Asides from the overall trend of increasing electronegativity across and up the Periodic Table (towards fluorine), there seems to be a minor peak in the first 3 periods of the $d$-block element... |
Why are there peaks in electronegativities in d-block elements? |
Looking at the Pauling electronegativities in the Periodic Table (below, from [ChemWiki][1]):
![enter image description here][2]
Asides from the overall trend of increasing electronegativity across and up the Periodic Table (towards fluorine), there seems to be a minor peak in the first 3 periods of the $d$-block... |
The Raschig process (according to the [german wikipedia][1]) is divided in the following steps:
1. $\ce{2NaOH + Cl2 -> NaOCl + NaCl + H2O}$
2. $\ce{NaOCl + H2O -> HOCl + NaOH}$
3. $\ce{HClO + NH3 -> NH2Cl + H2O}$
4. $\ce{NH2Cl + NH3 -> N2H4 + HCl}$
5. $\ce{N2H4 + 2NH2Cl -> N2 + 2NH4Cl}$
But what happens ... |
The Raschig process (according to the [german wikipedia][1]) is divided in the following steps:
1. $\ce{2NaOH + Cl2 -> NaOCl + NaCl + H2O}$
2. $\ce{NaOCl + H2O -> HOCl + NaOH}$
3. $\ce{HClO + NH3 -> NH2Cl + H2O}$
4. $\ce{NH2Cl + NH3 -> N2H4 + HCl}$
5. $\ce{N2H4 + 2NH2Cl -> N2 + 2NH4Cl}$
But what happens ... |
What is the most recent scientific consensus regarding this matter? |
Are the elements La and Ac considered to be in the d subshell or the f subshell? |
How can one mimic a volcano eruption using household chemicals **safely**?
We've tried it in a testing tube with baking soda and vinegar. This wasn't quite as impressive as expected.
On the web we've found recipes that add food coloring (red) and dish washing liquid to the mix. I guess the latter is for some bubb... |
Many periodic tables place lanthanum and actinium in the f-block of elements, for example, [this periodic table](http://periodic.lanl.gov/index.shtml) from Los Alamos National Laboratory.
However, [this table](http://www.rsc.org/periodic-table) from the Royal Society of Chemsitry places lanthanum and actinium in the... |
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