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It’s all about minimizing the energy of the system. Imagine a 2D example:
![2D example][1]
You can imagine the green circles as the cations ($\ce{Na+}$) and the blue ones as anions ($\ce{Cl-}$). Where is the next chloride you add going to go?
1. Not a great choice – it doesn’t really balance. The nearest blue... |
According to [Wikipedia's article about orbital hybridisation][1]:
> [...] today it is considered an effective heuristic for rationalising the
> structures of organic compounds. [...] Hybrid orbitals are assumed to be mixtures of atomic orbitals, superimposed on each other in various proportions.
So are hybrid o... |
Hybrid orbital is an actual solution of Schrodinger's equation or only a heuristic? |
The course calendar for my university describes Chem 101 and 102 as "math intensive". However, it doesn't say what kind of math is involved.
What kind of math should I expect in first year chemistry?
Would it be helpful to have first year calculus under my belt first? |
What kind of math should I expect in first year chemistry? |
In short this is the way I imagine them, as slight directional changes in spins propagating through the system.
The Heisenberg Hamiltonian for the [exchange energy][1] associated with magnetic coupling is a pairwise sum over an exchange integral $J_{ij}$ for two sites $i$ and $j$, with spin moments $\hat S_i$ and $... |
Got an really old sample of sodium tetraphenylborate. It should be white, but it is red. Does any know what was formed and how it influences precipitation of cations in water? |
Old red sample of sodium tetraphenylborate, why it is red? |
There’s an excellent question on Stack Exchange regarding the radiolysis of water [here][1] but I have one simple outstanding question that perhaps someone might now; in radiobiology, a common DNA damaging free radial is caused by the radiolysis of water. This reaction is something like
$$\ce{H2O + $h\nu$ -> H2O+ +... |
last week I tried synthesizing acetylsalicylic acid - the reaction is shown below - using $H_2 SO_4$ as a catalyst. However, as the title suggests the synthesis failed as I used too much sulphuric acid - approximately four times more than the prescribed volume. Needles to say, I had to redo the synthesis.
![Synthe... |
I bought a canned pineapple and finished the content. The part of the can that is in contact with the liquid appears like galvanized steel(crystalline surface or spangles sort of appearance), while the part that are not looks pretty shiny like the outside of the can.
I then washed the can and added water to it, and... |
Why is a tin can that appears like galvanised steel rusting? |
In spectroscopy we described the electric with the approximative separaility of internal motions as:
E=E<sub>e</sub>+E<sub>v</sub>+E<sub>r</sub>+E<sub>ns</sub>
(energies: electronic, vibratory, rotatory; nuclear spin (neclected))
With the Born Oppenheimer approximation of nuclei and electrons you get a formula... |
Last week, I tried synthesizing acetylsalicylic acid - the reaction is shown below - using $\ce{H2SO4}$ as a catalyst. However, as the title suggests the synthesis failed as I used too much $\ce{H2SO4}$ - approximately four times more than the prescribed volume. Needles to say, I had to redo the synthesis.
![Synth... |
In spectroscopy we described the electric with the approximative separaility of internal motions as:
E=E<sub>e</sub>+E<sub>v</sub>+E<sub>r</sub>+E<sub>ns</sub>
(energies: electronic, vibratory, rotatory; nuclear spin (neclected))
With the Born Oppenheimer approximation of nuclei and electrons you get a formula... |
In spectroscopy we described the electric with the approximative separaility of internal motions as:
E=E<sub>e</sub>+E<sub>v</sub>+E<sub>r</sub>+E<sub>ns</sub>
(energies: electronic, vibratory, rotatory; nuclear spin (neclected))
With the Born Oppenheimer approximation of nuclei and electrons you get a formula... |
In spectroscopy we described the electric with the approximative separaility of internal motions as:
\begin{equation}
E=E_e+E_v+E_r+E_{ns}
\end{equation}
(energies: electronic, vibratory, rotatory; nuclear spin (neclected))
With the Born Oppenheimer approximation of nuclei and electrons you get a formula whi... |
The major issue with the blood-brain barrier is that aside from small hydrophobic/lipophilic compounds (including $\ce{O_{2}}$ and $\ce{CO_{2}}$), almost everything else is prevented from passing due to cellular tight junctions and will only (potentially) pass through via active transport.
However, for small lipophi... |
I've been working on another CIF file, this time for (-)-*threo*-methylphenidate based on *[Pharma Res, 1995][1]* (sadly the relevant crystallography data isn't supplied in the free preview at Springer). I have several questions relating to this file, the most pressing is that so far I have this loop:
loop_
... |
Why does pKa of a acid-base indicator equal to the pH when the equivalence point is reached? |
I'm looking for a chemical reaction that produces a large amount of a gas in a very short amount of time (like less than a second). What are my options? |
What reactions create a lot of gas really quickly? |
When solving the lewis structure for the ClO$_2$$^-$ ion, taking into consideration formal charges, the structure is represented as
----------
![Chlorite ion lewis structure][1]
----------
A lewis model with **2 double bonds** also fits the formal charge and lewis model requirements, however this t... |
Turbidity is essentially the clarity of water. Turbidity can be measured in many ways such as a turbidimeter, secci disk or a turbidity tube (which incorporates a secci disk at the bottom). If you had a small turbid water sample - 20mL, how could you measure the turbidity with a turbidity tube? |
How to attach a liebig condenser to a flask for reflux heating? |
When solving the lewis structure for the $\ce{ClO2-}$ ion, taking into consideration formal charges, the structure is represented as:
----------
![Chlorite ion lewis structure][1]
----------
A lewis model with **2 double bonds** also fits the formal charge and lewis model requirements, however this... |
Is there any required data missing from my CIF file? |
I previously asked a question about a CIF file here (namely http://chemistry.stackexchange.com/questions/29696/cif-fields-that-are-available-for-some-atoms-but-not-others) I think I have the answer (namely to place dots [.] at places where the two missing terms would normally appear), although I felt I'd wait to see if... |
Are there any (liquid) chemicals that experience rapid, extensive, and controllable volume changes in reaction to heat? |
Turbidity is essentially the clarity of water. Turbidity can be measured in many ways such as a turbidimeter, secci disk or a turbidity tube (which incorporates a secci disk at the bottom). If you had a small turbid water sample - 20mL, how could you measure the turbidity with an electronic device?? |
I was once told on this site that it was incorrect form to use units that specify the chemical being referred to in dimensional analysis. For example:
$$150.~\mathrm{g}~~\ce{KNO3} \cdot \frac{1~\mathrm{mol}~~\ce{KNO3}}{101.103~\mathrm{g}~~\ce{KNO3}} \cdot{} \frac{1~\mathrm{mol}~~\ce{C7H4O}}{6~\mathrm{mol}~~\ce{KNO3... |
Is there an equation to figure out what the temperature of an the area will be a certain distance from the heat source? For example: If I know there is a heat source at 0m, and the temp is 100C, is there a way to find out what the temperature will be at 50m away from the heat source? Is there some sort of equation for ... |
Equation for heat loss over distance? |
Is there an equation to figure out what the temperature of an the area will be a certain distance from the heat source?
For example, If I know there is a heat source at 0m, and the temp is 100 °C, is there a way to find out what the temperature will be at 50m away from the heat source? Is there some sort of equatio... |
I know it's probably a stupid question, but I can not figure this out. I have a liebig condenser that I usually use for distillation with a Kjeldahl bulb, which makes it easy to attach to a flask because the bulb has a stopper on both ends?
Now I have an experiment that calls for reflux heating, where the condenser... |
Is there an equation to figure out what the temperature of an the area will be a certain distance from the heat source?
For example, If I know there is a heat source at 0 m, and the temp is 100 °C, is there a way to find out what the temperature will be at 50 m away from the heat source? Is there some sort of equat... |
How does standardising a secondary standard solution make it suitable as a standard solution? |
What are the products of partial hydrolysis of $\ce{XeF_6}$?
Is $\ce{XeOF_4}$ formed or $\ce{XeO_2F_2}$ is formed? |
According to the UC Davis ChemWiki [Chemistry of Helium][1], helium has a comparatively unusual property, specifically:
> Helium is the only element that cannot be solidified by lowering the temperature at ordinary pressures
'Ordinary' referring to standard air pressure (1 atmosphere). In order to solidify, ther... |
Why can't helium be solidified at 'ordinary' pressures? |
Suppose I am given some reaction in which
$$\ce{C6H12O6 -> CO2}$$
and I want to calculate n-factor for this reaction to ultimately calculate equivalent weight of carbon for this reaction. Since $$E=\frac{M}{n}$$
I know that n-factor is no of electron gained/lost by one atom of a compound.
So Initial Oxidation st... |
$\ce{NaOH -> Na+ + OH-} \quad \Delta H^\circ = -44.51\ \mathrm{kJ/mol}$
The dissolution of sodium hydroxide in water is an exothermic process, and so, according to Le Chatelier’s principle, cooling the container should shift the reaction to the right. Shouldn’t this mean that cooling the container will increase the ... |
In spectroscopy we described the electric energy with the approximative separability of internal motions as:
\begin{equation}
E=E_e+E_v+E_r+E_{ns}
\end{equation}
(energies: electronic, vibratory, rotatory; nuclear spin (neclected))
With the Born Oppenheimer approximation of nuclei and electrons you get a for... |
$\ce{C4H6O2}$ (10.75 g) was dissolved in water (250 cm<sup>3</sup>) and then a 20 cm<sup>3</sup> sample was titrated against an alkali metal hydroxide solution. This required 17.35 cm<sup>3</sup> of the alkali. What was the concentration of the alkali?
The water was evaporated from the alkali solution (100 cm<sup>3</... |
I receive 120 ml bags of medicine in sterile water. The medicine is refrigerated and then packed with a significant amount of ice packs in an insulated bag. Generally three times the volume of all the medicine. When I remove the ice packs, they are still solid two hours after being packed. So, they are very cold.
Is... |
From what I understand, adding $\ce{NaOH}$ to a solution containing transition metal ions gives transition metal hydroxide precipitates. Why is $\ce{NaOH}$ soluble but transition metal hydroxides insoluble? I have a feeling it has something to do with ligands and complexes formed, which I am familiar with.
|
The difference between there acidity arises only due to the difference in inductive effect[or the electron donating capacity of the alkyl group] of the alkyl group attached to the $\ce{C=C}$ in both the cases.
[By this site there exists a difference of total one unit][1]
[For more info on Inductive Effect][2]
... |
According to [Wikipedia's article about orbital hybridisation][1]:
> [...] today it is considered an effective heuristic for rationalising the
> structures of organic compounds. [...] Hybrid orbitals are assumed to be mixtures of atomic orbitals, superimposed on each other in various proportions.
So are sp, sp2,... |
sp, sp2 and sp3 hybrid orbitals are actual solutions of Schrodinger's equation or only a heuristic? |
How would you determine the size of a polyatomic ion?
For example when determining which ion is bigger, $\ce{NH2-}$ or $\ce{I-}$, what would you use to determine the size difference?
I know that $\ce{I-}$ would be much smaller than $\ce{I2-}$ (since the $\ce{e-}$ are not held as tightly in the $\ce{I2-}$ causing ... |
In spectroscopy we described the electric energy with the approximative separability of internal motions as:
\begin{equation}
E=E_e+E_v+E_r+E_{ns}
\end{equation}
(energies: electronic, vibratory, rotatory; nuclear spin (neclected))
With the Born Oppenheimer approximation of nuclei and electrons you get a for... |
When copper is precipitated out of a solution e.g from CuI, why does it appear pink instead of copper-coloured? Are there other situations where copper appears pink in solid form? |
Why does copper precipitate out as a pink solid? |
The rule of thumb for hydroxide salts is actually that all hydroxides are insoluble save those of the alkali metals, $\ce{Ca^{2+}}$, $\ce{Sr}^{2+}$, and $\ce{Ba}^{2+}$. There are many resources you can look up to check the solubility rules of certain ions, [this one][1], for example.
Before researching this, I suspe... |
When talking about standards, there's always the dilemma: **How is a standard standardized?** Well, you compare it to another standard you already have, and after you consider all the sources of errors, you have a new standard.
In case of the primary standards, you can always promptly trust the label's purity inform... |
Objectively, what does make the solubility of $C_{5}H_{11}OH$ greater than the $C_{5}H_{11}Cl$ in water? |
Objectively, what makes the solubility of $\ce{C_{5}H_{11}OH}$ greater than the $\ce{C_{5}H_{11}Cl}$ in water? |
Objectively, what does make the solubility of $\ce{C_{5}H_{11}OH}$ greater than the $\ce{C_{5}H_{11}Cl}$ in water? |
Objectively, what makes the solubility of $\ce{C_{5}H_{11}OH}$ greater than the $\ce{C_{5}H_{11}Cl}$ in water? |
Objectively, what makes the solubility of $\ce{C5H11OH}$ greater than the $\ce{C5H11Cl}$ in water? |
I previously asked a question about a CIF file here (namely http://chemistry.stackexchange.com/questions/29696/cif-fields-that-are-available-for-some-atoms-but-not-others) I think I have the answer (namely to place dots [.] at places where the two missing terms would normally appear), although I felt I'd wait to see if... |
So, I have to find the delta t rxn of a solution for my lab report. Earlier in the lab, it gave the equation as deta t rxn=t mixture + 1/2 (t substance 1 + t substance 2) and all temperatures were at the exact time of mixing found from a linear equation of temperature points on a graph. Now, I have another mixture whic... |
Is there more than one equation for delta t rxn? |
If water is the solvent wouldn't the only thing that moves be water? (Osmosis) |
Why is pickle salty? How does salt get into pickle? |
What is the difference when following up ozonolysis with DMS, Zn/water, or just water? Or is there really no substantial difference at all?
In my textbook, the alkenes section uses DMS or Zn/water but then in the alkynes section it uses water with no explanation as to why that happens. My professor also uses them inte... |
What is the difference when following up ozonolysis with DMS (dimethyl sulfide), Zn/water, or just water? Or is there really no substantial difference at all?
In my textbook, the alkenes section uses DMS or Zn/water but then in the alkynes section it uses water with no explanation as to why that happens. My professor ... |
When I learnt about polarity, I always come to the term electronegativity and always use the electronegativity chart. However, when I studied further, they have the word electroposivity.
So, I've been thinking why we use electronegavity more often than electropositivity? And why we have a electronegativity chart ins... |
I know this may look like some question easily answered with common sense, but please read.
If water is the solvent wouldn't the only thing that moves be water? (Osmosis)
**Edit:** this is basically what I think. If you imagine the skin of whatever you are pickling as a membrane that prohibit the flow of electrolytes... |
What would be the effect if someone were to drink ultra-pure, 18 M-ohm water? Would they immediately die? Would they just need to pee more? Would CO$_2$ from the air (after the bottle is opened) and whatever's in saliva dissolve into the water making it much less pure before it gets into the important parts of their... |
When I first learned this term. I was introduced to this graph: ![enter image description here][1]
The heat in this case is at 100C, which I had ever since believed to be the only temperature of vaporization, **assuming vaporization = boiling.**
Then I saw a table with all the heat of vaporization values for differen... |
What is heat of vaporization? How can it be used at temperature as low as 25 C? |
Think of vaporization as the removal of the fastest molecules. The separation of the gaseous form from the more closely-bound liquid therefore removes energy from the liquid. The heat of vaporization can apply at much lower temperatures than the BP of water *at atmospheric ressure*. Even on a day when the temperature i... |
> What would be the effect if someone were to drink ultra-pure, 18 M-ohm water?
Not much, although if they drank many gallons of the water it could be a problem.
> Would they immediately die?
No.
> Would they just need to pee more?
Probably.
> Would CO2 from the air (after the bottle is opened) a... |
> What would be the effect if someone were to drink ultra-pure, 18 M-ohm water?
Not much, although if they drank many gallons of the water it could be a problem.
> Would they immediately die?
No.
> Would they just need to pee more?
Probably.
> Would $\ce{CO2}$ from the air (after the bottle is op... |
What would be the effect if someone were to drink ultra-pure, 18 M-ohm water? Would they immediately die? Would they just need to pee more? Would $\ce{CO_2}$ from the air (after the bottle is opened) and whatever's in saliva dissolve into the water making it much less pure before it gets into the important parts of ... |
Turbidity is essentially the clarity of water. Turbidity can be measured in many ways such as a turbidimeter, secci disk or a turbidity tube (which incorporates a secci disk at the bottom). If you had a small turbid water sample - 20mL, how could you measure the turbidity without an electronic device?? |
What would be the effect if someone were to drink ultra-pure, 18 M-ohm water?
Would they immediately die? Would they just need to pee more? Would $\ce{CO_2}$ from the air (after the bottle is opened) and whatever's in saliva dissolve into the water making it much less pure before it gets into the important parts... |
When I first learned this term. I was introduced to this graph: ![enter image description here][1]
The heat in this case is at 100 °C, which I had ever since believed to be the only temperature of vaporization, **assuming vaporization = boiling.**
Then I saw a table with all the heat of vaporization values for di... |
What is heat of vaporization? How can it be used at temperature as low as 25 °C? |
Azide is a fairly common ion, but why aren’t there similar versions such as $\ce{P3-}$ or $\ce{B3+}$? Do they exist, is there something wrong with these ions as to make them more likely to just break apart rather than for ionic compounds. |
Think of vaporization as the removal of the fastest molecules. The separation of the gaseous form from the more closely-bound liquid therefore removes energy from the liquid. The heat of vaporization can apply at much lower temperatures than the BP of water *at atmospheric pressure*. Even on a day when the temperature ... |
So, I have to find the $\Delta t_{reaction}$ of a solution for my lab report. Earlier in the lab, it gave the equation as
$\Delta t_{reaction}=t_{mixture}+\frac{1}{2}(t_{substance1}+t_{substance2})$
and all temperatures were at the exact time of mixing found from a linear equation of temperature points on a grap... |
Is there more than one equation for $\Delta t_{reaction}$? |
At my school, my teacher tell us to extract sodium from normal salt ($\ce{NaCl}$) but without using electrolysis of molten sodium chloride. So is there a way to do that? |
Why do radical mechanisms favor the homolytic dissociation of a C-H bond over a C-C bond?
The C-H bond is stronger in magnitude (and it's also slightly polarized), so why would it break more easily as compared to the C-C bond?
My instructor explains this by claiming that the products of C-H bond dissociation are stab... |
What is the effect of hybridization and double-bond formation on the rest of the atoms/molecules attached to the central atom?
For example, in a benzene molecule, the Carbon-Carbon bonds are intermediate between single and double bonds. But what is the effect of the presence of the double bonds between the carbons on ... |
Why do radical mechanisms favor the homolytic dissociation of a $\ce{C-H}$ bond over a $\ce{C-C}$ bond?
The $\ce{C-H}$ bond is stronger in magnitude (and it's also slightly polarized), so why would it break more easily as compared to the $\ce{C-C}$ bond?
My instructor explains this by claiming that the products o... |
Why is the ionic product for water ($K_\text{w}$) temperature dependent? The concentration of $\ce{H+}$ and $\ce{OH-}$ ions in pure water is $[\ce{H+}] = [\ce{OH-}] = 1.0\times 10^{-7}\ \mathrm{mol/l}$ at $25\ \mathrm{^\circ C}$, and therefore the ionic product of water at $25\ \mathrm{^\circ C}$ is $1.0\times 10^{-14}... |
![enter image description here][1]
**technically the line between liquid and solid phase would go a long way before hitting the y-axis. But the point is it will eventually.**
So the question remains, can any liquids, including water (with its unique phase diagram) be liquefied regardless of the pressure?
[1]: http... |
Can water be liquefied or solidified just by adjusting the temperature, regardless of the pressure? |
![enter image description here][1]
**technically the line between liquid and solid phase would go a long way before hitting the y-axis. But the point is it will eventually.**
So the question remains, can any liquids, including water (with its unique phase diagram) be liquefied regardless of the pressure?
[... |
![enter image description here][1]
**technically the line between liquid and solid phase would go a long way before hitting the y-axis. But the point is it will eventually.**
So the question remains, can any liquids, including water (with its unique phase diagram) be liquefied regardless of the pressure?
![enter... |
Theoretically, **YES**!
**But why?**
In the real world there are a thousand different ways to accomplish a certain task, but only a few will be the most efficient. So in considering your question.
> So the question remains, can any liquids, including water (with its unique phase diagram) be liquefied regardless ... |
The first thing that should be highlighted here is that electropositivity is simply the opposite of electronegativity, any of the two can be used interchangeably with the necessary modifications to the sentence.
It is true though that electronegativity is more commonly used then electropositivity. For example, the ... |
I knew that Gaussian assumes the molecule is alone in vacuum, that is, the molecule doesn't interact with anything, when optimising the molecule. But I've found that Gaussian's optimisation(at HF or DFT levels) results are almost the same as experimental data, which were got in solid state by X-ray diffraction. Everyon... |
Are molecular optimisations in Gaussian really the optimisations of molecules in vacuum? |
I have a water softener for showers and dishwasher and a reverse osmosis filter for drinking water. For convenience of the install, the RO filter is using softened water (some calcium carbonate has been exchanged with sodium chloride -- this is my basic understanding; correct me if I'm wrong). I don't fully understan... |
It is possible to do crystal structure optimizations in Gaussian by adding translation vectors (DFT isn't as good with intermolecular reactions, but it will probably be a better approximation than optimizing without PBC, which is akin to a gas phase molecule).
Whether or not solid behavior and gas behavior are similar... |
Your concept of a cell is a little vague. Although the cell wall is made from a diglyceride bilayer, it is not impregnable. In fact, there are many proteins that pass through the cell wall where dissolved material can pass. One of the proteins is called the [sodium potassium pump][1]. In a living cell, the protein uses... |
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