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"Using a state-of-the-art atomic force microscope, the scientists have taken the first atom-by-atom pictures, including images of the chemical bonds between atoms, clearly depicting how a molecule's structure changed during a reaction. Until now, scientists have only been able to infer this type of information from spe... |
How did Scientists Capture The First Images of Molecules Before and After Reaction? |
I do not understand how equation(3) occurs.(taken from the book Internal Combustion Engines by John B.Heywood)
$$ $$
Consider a reactive mixture of ideal gases. The reactant species $M_a,M_b$ etc.and the product species $M_l,M_m$ etc. are related by the general reaction whose stoichiometry is given by:
$$\upsilon _a... |
I do not understand how equation(3) occurs.(taken from the book Internal Combustion Engines by John B.Heywood)
$$ $$
Consider a reactive mixture of ideal gases. The reactant species $M_a,M_b$ etc.and the product species $M_l,M_m$ etc. are related by the general reaction whose stoichiometry is given by:
$$\upsilon _a... |
There are a ton of papers on how AFM works, but I'll have a go at explaining it anyhow.
Atomic Force Microscopy (AFM) is a venerable technology for imaging nanostructures down to individual molecules by physically contacting atoms on surfaces. The whole process is very similar to a finger reading Braille.
What do... |
I am using Avogadro for visualizing some cluster systems. Is there a way to hide the bonds of the system, ie. only showing atoms?
Thanks! |
Avogadro - How can bonds be hidden and only show atoms? |
Let's take Hematoxylin, which is a pH indicator and a stain for histology, and therefore a chromophore, but does not fluoresce:
![enter image description here][1]
Now let's take Eosin, which stains tissue pinkish, but is also fluorescent:
![enter image description here][2]
I would like to know which feature... |
What's the physicochemical difference between a chromophore and a fluorophore? |
Good morning,
I am trying to run single point calculations on Gauss 09 for Mulliken population analysis on large graphene/graphite (940-1411 atoms).
I was having difficulty with memory issues (single CPU lic) running dftba for single point. I have stepped my convergence (beginning with conver=1, and increasing by ... |
What is the accuracy of scf=qc when convergence criteria is lowered (Gauss 09)? |
I am not very great at chemistry, and I feel like this may be an elementary problem; Howver, I was wondering if there is a decent and non complex way to predict the outcome of mixing two chemicals together.
I know that molecular dynamics is used in computational chemistry to understand some of these types of probl... |
I am trying to run single point calculations on Gauss 09 for Mulliken population analysis on large graphene/graphite (940-1411 atoms).
I was having difficulty with memory issues (single CPU lic) running dftba for single point. I have stepped my convergence (beginning with conver=1, and increasing by reading in my p... |
Something that I have discovered is that when Gaussian (or other good ab initio software) fails to converge, there is something sketchy about what one is trying to calculate. Sometimes DFT calculations just aren't appropriate, especially in cases that require multiconfigurational SCF for even a zero-th order descriptio... |
I don't know for sure, but I suspect these two reagents would lead to the same product. They are both superacids, and extremely harsh.
Whichever is a better Bronsted acid (proton donor) in benzene probably leads to a faster reaction, or better conversion. But who knows? Maybe the reactions are so acidic (two plus... |
Does $\ce{Ni((en)2(Cl)2)}$ show cis-trans form ?
And if No
Why not ? |
> If I add equal amounts of lemon juice and sugar in water, does the ph-value remain unchanged, as both cancel each other out?
This question arose in my head as I learned that pouring milk into black tea lowers the acidity of the beverage. Therefore, tea with milk tastes more pleasant (in the sense of 'less acidic).... |
I found betaine in my face wash. I think it is there because it's polar and can pick up grease. But my question is why are betaines used over other detergents? What are the factors that contribute to the which detergents are used in face wash (or indeed shampoo/shower gels)? |
How do chemists decide on which detergent to use? |
I'm currently in high school and I did two titrations. The first one is a titration of $10.0$mL $0.1$M $\ce{HCl}$ with $x$ mL $\ce{NaOH}$. I obtained the following titration curve:
![first titration][1]
The blue curve is what I measured and the red curve is what the curve would look like in theory, with these dat... |
Why is a theoretical titration curve higher than a practical one? |
I came across a compound FeO4^2- but Fe has +6 charge according to my calculations. How this is possible ? Or it is possible but my periodic table is kind of non-detailed one. (On the table I got d metals possible charges). |
I am having trouble understanding how valance electrons are counted in Helium.
My references are:
1. [Here][1] where it appears that Helium has 0 valance electrons because the shells are finished
2. [Here][2] where it appears that Helium has two valence electrons (which is what I thought)
How many valanace... |
Valance electrons in Helium? |
I know that analytic forms of the Helium wavefunctions are not known. However, are there empirical expressions for the low-lying states of Helium? I'd like to use them to calculate some transition matrix elements for fun. |
I came across a compound $\ce{[FeO4]^{2-}}$ but $\ce{Fe}$ has +6 charge according to my calculations. How this is possible ? Or it is possible but my periodic table is kind of non-detailed one. (On the table I got $d$-metals possible charges). |
My chemistry text book says that "Atomic Absorption Spectrometry (AAS) can be used to determine the concentration of metal ions, but other methods must be used for anions. One convenient method is to use an ion-selective electrode (ISE)." What is the reason? Why ASP cannot be used for determining the concentration of a... |
Why Lanthanum is "fluoride ion sensitive electrode" and hence used for measuring "flouride concentration"? |
> If I add equal amounts of lemon juice and sugar into water, does the ph-value remain unchanged, as both cancel each other out?
This question arose in my head as I learned that pouring milk into coffee increases the ph-level of the beverage making it taste less sour (You might want to check out the following video ... |
- `What is the reason behind choosing "Lanthanum doped with europium"?`
Well, you said it yourself, `because "fluoride ions bind to the crystal"`.
Here's a great explanation from Wikipedia:
*In the lanthanum fluoride electrode, the sensing element is a crystal of lanthanum fluoride LaF3, doped with europium fl... |
- `What is the reason behind choosing "Lanthanum doped with europium"?`
Well, you said it yourself, `because "fluoride ions bind to the crystal"`.
Here's a great explanation from Wikipedia:
*In the lanthanum fluoride electrode, the sensing element is a crystal of lanthanum fluoride LaF3, doped with europium fl... |
Which has hotter temperature, blue flame or yellow flame? Why do moms prefer blue flame in cooking food? |
Which has hotter temperature, blue flame or yellow flame? |
As the title suggests - does there exist a liquid with a lower specific heat then water but with a higher thermal conductivity?
I thought of this in the context of [sous vide cooking](http://en.wikipedia.org/wiki/Sous-vide): Ideally, the liquid involved would transfer heat to the food quickly (hence high thermal co... |
Liquid with low specific heat and high thermal conductivity (relative to water)? |
How many protons are required to satisfy hydroxyamine's (NH2OH) lust for protons? |
- What is the general name for acids that can only lose one hydrogen ion? (i.e. $\ce{HCl}$)
- What is the general name for acids that can lose $n$ hydrogen ions? (i.e. $\ce{H_3PO_4}$, which can lose 3)
The answers to these questions are probably mentioned a million times on the internet, but I could not find them. |
I'm not a chemist but I'm working on an eco-friendly project that is supposed to recycle CO2 from the air and convert it to O2 or at least a usable fuel source ,the system can use the solar system as an energy source (I know that such system isn't efficient) but for the country in which the project is applicable it wou... |
Air recycling system(CO2-->O2) or (CO2-->fuel)? |
Well, hydroxylamine is technically amphoteric, meaning it can act as either a Bronsted acid or base. The acidic proton is presumably the one on the oxygen (although the resulting salts are apparently explosively unstable), while the nitrogen is the proton acceptor. I wouldn't expect the oxygen to be basic (which, unles... |
<p>
Chemistry Stack Exchange is for scientists, academics, teachers and students of <b>chemistry</b>.
</p>
<p>Questions may be of any level, but should be of the following types:</p>
<ul>
<li>Questions asking for explanation of a chemistry concept</li>
<li>Questions relating to observed chemical phenome... |
Here is a question from my practice problems:
![enter image description here][1]
[1]: https://i.stack.imgur.com/dMSNJ.png
I know that the answer is A, but I don't know why. Is it because A has the most moles of gas on the left? thanks |
My question pertains generally to any form of spectroscopy, but I'll focus on UV spectroscopy. I am trying to get information on carrying out spectroscopy, but most of it is theoretical. Wikipedia is completely useless. Textbooks generally go into more detail about the underlying sub atomic processes being carried out.... |
<p>
Chemistry Stack Exchange is for scientists, academics, teachers and students of <b>chemistry</b>.
</p>
<p>Questions may be of any level, but should be of the following types:</p>
<ul>
<li>Questions asking for explanation of a chemistry concept</li>
<li>Questions relating to observed chemical phenome... |
This can be a stupid question but comes in mind and for me it's important.
How can we chill water poured in a plastic bottle without freezing it or without Refrigerator?
I believe that if question came in mind then there should be solution. I googled but not found any answer. |
How to make a water chill without freezing it? |
This can be a stupid question but comes in mind and for me it's important.
How can we chill water poured in a plastic bottle without freezing it or without Refrigerator?
I believe that if question came in mind then there should be solution. I googled but not found any answer.
**Scenario:**
I am sitting in a o... |
This is quite a hot topic at the moment - the current buzz-phrase is **[power to gas][1]**.
There are quite a few conference papers and technical papers, and at least one dedicated conference, for it.
And **it's too soon for there to be a known "best" process.**
[Audi][2] and others are using a modified [Sabat... |
I have been curious about this question for a while. If you want to warm up a large amount of water, is it feasible to do this by adding a substance that reacts with the water? What is the relevant chemistry one has to know to work out how much the water would be heated up by?
If someone could kindly suggest or add ... |
Can you heat water with additives? |
How can we chill water in a plastic bottle without a freezer or refrigerator?
**Scenario:**
I'm in the office and I have two plastic bottles of water (brought from home). I'm in the office for 3 to 4 hours and this means the bottles I brought from home will get hot (and won't be drinkable in a hot season). Now I ... |
How do I chill water without a refrigerator? |
I have been curious about this question for a while. If you want to warm up a large amount of water, is it feasible to do this by adding a substance that has an exothermic reaction with the water? What is the relevant chemistry one has to know to work out how much the water would be heated up by?
If someone could ki... |
Is there a word for a compound that has both ionic and covalent bonds? |
In reading a COA (Certificate of Analysis), I came across an Assay line:
The Assay is 100.5% where Min is 98.5 and max is 101.0
This product is L-Cysteine Hydrochloride Monohydrate. How can the Assay be over 100%? |
Does Cysteine break down in filtered water? Should this made more acidic?
If I mix Cysteine powder in Juice (something acidic maybe), does it remain at Cysteine? It seems that it can oxidize into Cystine and loose some of its qualities. |
In reading a COA (Certificate of Analysis), I came across an Assay line:
The Assay is 100.5% where "Lower Limit" is 98.5 and "Upper Limit" is 101.0
This product is L-Cysteine Hydrochloride Monohydrate. How can the Assay be over 100%?
I have found this statement: "If the substance under test is purer than ... |
I know that elements (ex. Ag) have spectral/emission/absorption lines, but do chemical compounds (ex. NaCl) have spectral lines as well? Ones that when seen you can tell that that compound (NaCl) is made up of certain elements (Na and Cl). |
Do chemical compounds have spectral lines, or only elements? |
From the comments:
> What do you want to do with the hot water? Swim in it. I was thinking
> of thousands of liters
That's an interesting idea, but unfortunately I don't think adding chemicals to a pool in order to heat it is a good idea (specially yellowish chemicals). The water temperature would drop in a few ... |
What is the biggest environmental issue with using methane, $\ce{CH4}$, (which is found as the major energy source in natural gas, shale gas, biogas, and synthetic natural gas), as a combustible fuel? |
What's the greatest environmental drawback with using methane as a combustable fuel? |
What are the biggest environmental issues with using methane, $\ce{CH4}$, (which is found as the major energy source in natural gas, shale gas, biogas, and synthetic natural gas), as a combustible fuel? |
What are the major environmental drawbacks with using methane as a combustable fuel? |
Who does molecules like alkanes with higher Molecular Mass (Mr) have stronger inter-molecular forces? For example, methane (CH4) has a weaker intermolecular force than pentane (C5H12). Pentane has a higher Mr than methane and therefore Pentane possess stronger inter-molecular force than Methane. These are members of th... |
Why molecules having higher Mr has stronger inter-molecular forces? |
Why does molecules like alkanes with higher Molecular Mass (Mr) have stronger inter-molecular forces? For example, methane (CH4) has a weaker intermolecular force than pentane (C5H12). Pentane has a higher Mr than methane and therefore Pentane possess stronger inter-molecular force than Methane. These are members of th... |
There are a lot of reasons for why some molecules have stronger IMF's than others, but the trend of increasing IMF for increasing Mr is due to an increase in London Dispersion Forces, part of the greater set of van der Waals forces. As you may or may not know, these alkanes are non-polar molecules (that is, they don't ... |
Why do molecules like alkanes with higher molecular mass ($M_r$) have stronger inter-molecular forces? For example, methane ($\ce{CH4}$) has a weaker intermolecular force than pentane ($\ce{C5H12}$). Pentane has a higher $M_r$ than methane and therefore pentane possesses stronger inter-molecular force than methane. The... |
Why do molecules having a higher Mr have stronger inter-molecular forces? |
As title says, why is methyl group more electron-donating than tert-butyl group? The context behind this is stabilization of conjugate base. (http://www.khanacademy.org/science/organic-chemistry/organic-structures/acid-base-review/v/stabilization-of-conjugate-base-iii look at 10:51)
|
Why is methyl group more electron-donating than tert-butyl group? |
We had a test and and we had a question asking the number of Valence electrons in an azide ion((N3)- ). I find out that the answer is 16 but I could not understand how.
I saw the structure. It says that the end nitrogen have a -1 charge and the Middle nitrogen has a +1 charge.
From where does the one of the en... |
[Cr(H$_2$0)_4Cl$_2$]Cl, Tetraaquadichlorochromium(III) chloride
According to a book, the (III) indicates that oxidation state of Cr, but it doesn't explain why. Cr has 6 valence electrons. How does it get to +3? |
$\ce{[Cr(H2O)4Cl2]Cl}$, Tetraaquadichlorochromium(III) chloride
According to a book, the (III) indicates that oxidation state of Cr, but it doesn't explain why. Cr has 6 valence electrons. How does it get to +3? |
Why do molecules having a higher $M_r$ have stronger inter-molecular forces? |
You can find some experimental information on dipole transition moments in the NIST Chemistry Webbook in the section on constants of diatomic molecules.
http://webbook.nist.gov/cgi/cbook.cgi?ID=B3000043&Units=SI&Mask=1000 |
Has diatomic oxygen ever been observed with a 3- charge, i.e. $\text{O}_2^{3-}$? Have any ab intio calculations been done on this ion? |
Are there substances that cannot undergo combustion? If so, what are they? |
Are there substances that cannot undergo combustion? |
I'm interested in measuring the stable isotope ratios of some bird feathers. I'm aware that a mass spectrometer is required to measure stable isotope ratios. Is it possible to measure stable isotope ratios at home, using your own 'DIY' spectrometer? |
stable isotope analysis at home? |
Just now I got some room temperature water and added some ice to cool it, and it just came to me, like the scientist I wish I was ... why doesn't frozen (freezing point) ice added to higher temperature liquid compound force the water molecules to solidify? |
Why won't water freeze if you put ice in it, despite ice being frozen? |
Is there a device that can measure the air in the room in lbs?
I would appreciate the anseer |
At room temperature, water is a liquid. So the ice will gradually turn into liquid.
You may ask your question in a different way: if you add water to ice, why doesn't the ice turn into liquid? It does, at room temperature.
If you add water to ice, at freezing temperature (Antarctica), the water turns to ice.
... |
`Why won't water freeze if you put ice in it?`
It will, even at room temperature. You just need a big enough, cold enough ice cube.
Don't believe it? Add a few drops of water to an ice cube in an ice cube tray (which is the same as adding an ice cube to a few drop of water). Wait a few seconds, turn the tray upsi... |
this might be a slightly daft question as I'm a physicist rather than a chemist, but I have a slight problem in using Henry's law which I think I can circumvent using the ideal gas law - I'd be grateful if anyone can confirm or deny my logic!
I have an equation that yields the volume of volume of oxygen gas unit ma... |
this might be a slightly daft question as I'm a physicist rather than a chemist, but I have a slight problem in using Henry's law which I think I can circumvent using the ideal gas law - I'd be grateful if anyone can confirm or deny my logic!
I have an equation that yields the volume of oxygen gas per unit mass of ... |
This might be a slightly daft question as I'm a physicist rather than a chemist, but I have a slight problem in using Henry's law which I think I can circumvent using the ideal gas law - I'd be grateful if anyone can confirm or deny my logic!
I have an equation that yields the volume of oxygen gas per unit mass of ... |
I wrote out an answer to this but realized I was wrong. But I've noticed a number of things:
First off, your form of the ideal gas law has the Molar Mass inverted. If you make the substitution that n=m/M, then the rearrangement reads m = M*V*p/(RT), you have the M on the bottom.
Secondly, You are selecting a Volu... |
This might be a slightly daft question as I'm a physicist rather than a chemist, but I have a slight problem in using Henry's law which I think I can circumvent using the ideal gas law – I'd be grateful if anyone can confirm or deny my logic!
I have an equation that yields the volume of oxygen gas per unit mass of ... |
Recently the water cooler was replace with a new filter.
However, when I refill my water kettle with the water from the water cooler, there are many bubbles and the taste was a bit like soap.
What chemical cause such effects? (Is it related to the new filter?) |
I was wondering if there is any other way to crystallize materials from a solution other than using supersaturation?
Thanks, |
I'm attempting to extract the diels alder reaction into a generic reaction and am trying to gain a better understanding of it.
Can a conjugated diene react with another conjugated diene via the diels alder reaction? And is the reaction limited to only dienes or can it be expanded to polyenes?
Does anyone happen t... |
In an esterification reaction between a carboxylic acid and an alcohol, a carboxylate ester and water is produced.
I found the following diagram online, and my textbook has a similar one as well
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQ9mq0NHUu_AuMWy4FevPvFJ8ptXJ9SH5aGjDiZ4ItokoXSgROVVg
(Sorry, I... |
In an esterification reaction between a carboxylic acid and an alcohol, a carboxylate ester and water is produced.
I found the following diagram online, and my textbook has a similar one as well
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQ9mq0NHUu_AuMWy4FevPvFJ8ptXJ9SH5aGjDiZ4ItokoXSgROVVg
(Sorry, I... |
The mechanism of the reaction doesn't involve the direct exchange of ions in the way that, e.g., a metathesis/double replacement reaction might. Take a careful look at the [reaction mechanism from the Wikipedia page][1]. Notice that one of the intermediates (the product after step three) is a tetrahedral complex with t... |
I need help on identifying precipitation, acid-base, and redox reactions. I know what each one is in theory:<br>
- Precipitation: Creating a solid
- Acid-Base: neutralization
- Redox: exchange of electrons
But given a chemical reaction like:
HCl (aq) + NaOH (aq) → H2O (l) + NaCl (aq)
I need to understand... |
The boiling point of water is $100^o$C. However, we find that even at room temperature, water can evaporate into gas.
Therefore, water vapor can exist at temperatures of, say, $50^o$.
At what temperature, can you say for certain that all water vapor will turn into liquid?
In other words, what is the Condensat... |
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