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**Background**:
Well, it's summer here in Brazil, a great way to keep cool is drinking a so called [Tereré](http://en.wikipedia.org/wiki/Terer%C3%A9), and, of course, we do need cold water for that.
**Problem**: I was looking for endothermic spontaneous reactions so I can cool the water in a bottle using an inner a... |
**Background**:
Well, it's summer here in Brazil, and a great way to keep cool is drinking a so called [Tereré](http://en.wikipedia.org/wiki/Terer%C3%A9), and, of course, we do need cold water for that.
**Problem**: I was looking for endothermic spontaneous reactions so I can cool the water in a bottle using an inn... |
Can whatever is special about quasicrystals be understood at A-Level standard or slightly above it? The material I saw online is either too layman or too advanced for me to follow. What practical uses do they have and why does their structure lead to the properties that allow them to have these practical uses? |
What is so special about quasicrystals? |
If Equilibrium constant stand for the extent of reaction at equilibrium, whether more of forward or backward reaction is taking place, then how come it is not affected by factors like concentration of reactants and product? Eg. If you increase concentration of reactant, equilibrium will shift to the right, which means ... |
What Does Equilibrium Constant represent? |
It's hard to know exactly what “level” you want address, as the [Wikipedia entry][1] seems a decent introduction to me. But in any case, here's what I consider “special” about quasicrystals:
**From the fundamental point of view:**
- Though they are regular (they are formed by symmetry operations that allow them t... |
If the Equilibrium constant stands for the extent of reaction at equilibrium, whether more of forward or backward reaction is taking place, then why is it not affected by factors like concentration of reactants and product?
For example, if you increase concentration of reactant, equilibrium will shift to the right,... |
What Does the Equilibrium Constant represent? |
![enter image description here][1]
[1]: https://i.stack.imgur.com/YS6pi.jpg
I have heard that acids taste sour because of hydrogen(I don't really know exactly).According to the definition of acids ,"An acid (from the Latin acidus/acēre meaning sour) is a chemical substance whose aqueous solutions are charact... |
Do acids without hydrogen taste sour? |
I have heard that acids taste sour because of hydrogen (I don't really know exactly). According to the definition of acids:
>An acid (from the Latin acidus/acēre meaning sour) is a chemical substance whose aqueous solutions are characterized by a sour taste, the ability to turn blue litmus red, and the ability to r... |
So when combining atomic orbitals to form molecular orbitals, you can either add the wave functions or subtract them. But at the same time, orbitals can exist in opposite phases (say one lobe of the p orbital is '+' and the other '-'). So what happens when you subtract two 1s orbitals of opposite phase, is that the sam... |
In an experiment we conducted, we heated 1.6 grams of copper dust, and got 1.7 grams of oxidised copper,
and our goal was to find which of the two forms, $CuO$ or $Cu_2O$ we got.
What I did:
\begin{array}{|c|c|c|}\hline
& Cu & O_2 \\ \hline
m(g) & 1.61 & 0.1 \\ \hline
... |
In an experiment we conducted, we heated 1.6 grams of copper dust, and got 1.7 grams of oxidised copper, (it probably reacted with 0.1 grams of $O_2$)
and our goal was to find which of the two forms, $CuO$ or $Cu_2O$ we got.
What I did:
\begin{array}{|c|c|c|}\hline
& Cu & O_2 \\ \hline
m... |
Your calculation looks good. Maybe the issue is not with the calculation, but with the experiment. Did you wait long enough so that all the copper is oxidized? |
Is H2CO3 (carbonic acid) soluble or insoluble in water? |
It's indeed not common, as the brittle/ductile transition is usually the other way around. You can, however, find counter-examples (in a limited range of temperature) by searching for [**“inverse brittle-to-ductile transition”**](http://www.google.com/?q=inverse+brittle-to-ductile+transition). |
I'd just like to ask for a little clarification here due to confusion from interdisciplinary studies.
I'm currently reading the 1976 paper related to the recent 2013 Nobel Prize for Chemistry, by 2 of the laureates Warshel and Levitt — [*Theoretical Studies of Enzymic Reactions: Dielectric, Electrostatic and Steric ... |
Do enzyme/substrate reactions that adhere (largely) to quantum theory not require consideration of gravity? |
I'd just like to ask for a little clarification here due to confusion from interdisciplinary studies.
I'm currently reading the 1976 paper related to the recent 2013 Nobel Prize for Chemistry, by 2 of the laureates Warshel and Levitt — [*Theoretical Studies of Enzymic Reactions: Dielectric, Electrostatic and Steric ... |
How can enzyme/substrate reactions that adhere (largely) to quantum theory also require 'Newtonian' consideration of gravity? |
Having never given it a though before, I recently discovered (in a different context) that the prefix halo- actually means 'salt' or 'sea' and the suffix -gen means 'to form' or 'to generate'. So the Halogens are the elements that 'form salts'. But there are salts that do not have halogens in them, like $Na_2S$ or $(NH... |
How did Halogens become known as Halogens? They are not the only elements that form salts! |
I have some weird, yellow-amberish pebbles that have been filtered by my Zero waterfilter. Any idea what they are? Copper maybe?
The black stuff is charcoal from the filter.
The quality of the water in my area is fairly good, with a TDS of 40-60. With the filter, I have a TDS of 0, which is excellent. But I'm sti... |
Yellow-Amber debri above water filter: What is it? |
I have some weird, yellow-amberish pebbles that have been filtered by my Zero waterfilter. Any idea what they are? Copper maybe?
The black stuff is charcoal from the filter.
The quality of the water in my area is fairly good, with a TDS of 40-60. With the filter, I have a TDS of 0, which is excellent. But I'm sti... |
Yellow-amber debris above water filter: What is it? |
I completed a titration experiment in a lab. The aim was to find the concentration of the titrant KMnO4 solution by titrating it with a sodium oxalate solution of a known concentration.
I first made a standard solution of sodium oxalate solution, using 0.826 g of sodium oxalate powder, then poured 50ml of distilled... |
I completed a titration experiment in a lab. The aim was to find the concentration of the titrant KMnO4 solution by titrating it with a sodium oxalate solution of a known concentration.
I first made a standard solution of sodium oxalate solution, using 0.826 g of sodium oxalate powder, then poured 50ml of distilled... |
We have learnt that the energy evel of both R and S optical isomer of a compoud is same, just as well the entropy of each isomer is also same. If we consider the conversion of R form of a compound to it's S isomer we observe that the change in gibbs free energy is "0". This implies that the two isomers must exist in eq... |
Equilibrium between R and S configuration? |
We're asked often to calculate the density of a crystal , and there is a known formula for that related to the unit cell volume ; Now , for simple geometric structures such as the bcc structure (and since it is close packed) , i know how to relate the different radius of the constituent compounds with the unit cell (un... |
We're asked often to calculate the density of a crystal, and there is a known formula for that related to the unit cell volume. Now, for simple geometric structures such as the bcc structure (and since it is close packed), I know how to relate the different radii of the constituent compounds with the unit cell's (uniq... |
So often I see total energies of transition states corrected for zero-point vibrational energy which always confuses me. Zero point energy is the lowest energy that a ground state molecule can have at 0K in a vacuum. Transition states are indeed not ground state molecules, can never be observed or isolated, have one ... |
Why are the total energies of transition states so commonly corrected for zero-point vibrational energy? |
We always hear about the different arrangements of molecules that lead to the formation of polymorphs, my question here is why would a polymorph form in the first place? The material was given enough time to solidify in a proper arrangement, why did it choose to solidify in a form that isn't the most stable? |
Why polymorphs form? |
Recently I have watched video demonstration with sponge and mercury and sponge can't absorb Mercury like it's doing with the water.
Why is that?
This is link to the video.
http://izismile.com/2013/10/22/can_mercury_be_absorbed_with_a_sponge.html |
Recently I have watched video demonstration with sponge and mercury and sponge can't absorb Mercury like it's doing with the water.
Why is that?
[This is link to the video.][1]
[1]: http://izismile.com/2013/10/22/can_mercury_be_absorbed_with_a_sponge.html |
You are asking wrong way. Sponge does not absorb almost anything. Apples, sand, dust, wires,...
The point is: Why can sponge absorb water?
Because the interaction of water and the sponge are similarly or even more favorable than interaction inside water. The nature of this effect is [capilary action][1].
[... |
Recently I have watched a [video][1] demonstration with a sponge and mercury and the sponge can't absorb Mercury like it does with water.
Why is that?
[1]: http://izismile.com/2013/10/22/can_mercury_be_absorbed_with_a_sponge.html |
When formulating a rate a equation two experiments must take place: one in which the reactant concentrations are varied, and one in which the catalyst concentrations are varied.
If I am given a sample of a solid catalyst, such as $MnO_2$, how can I change its concentration? Because I can't dilute a solid and increa... |
How can I formulate a rate equation using a solid catalyst? |
I'm reading up on molecular modelling and have come across some terms I should probably have learnt a long time ago but always scared me off a bit with the Greek letters. I guess I'm a big boy now so it's probably time to clarify...
The textbook uses the lowercase symbol omega ($\omega$) for torsion (a.k.a. dihedral... |
Given a set of partial charges for the atoms in a molecule, which are educated guesses but do not add up to zero, we would like to zero them in an intelligent way.
For example, if the net charge is negative and we see a +0.1 atom bonded to a -0.9 atom, we should probably shift the -0.9 towards zero to make that sect... |
What is an algorithm for making a net neutral molecule from a set of guessed positive charges? |
A molecule of phenol is much more inclined to under go an electrophilic substitution reaction than a molecule of benzene because the -OH group is highly reaction favoring. From what I understand, this is because when the -OH group is attached, it contributes a resonance structure involving a double bond between the oxy... |
The molecular orbital diagram for $O_2$ says that the sigma 2p bonding molecular orbital is lower in energy than the pi 2p bonding molecular orbital. Why is this not the case in the $B_2$ MO diagram? |
Are there any tricks I can use to pull SO2F2 out of the air? |
The molecular orbital diagram for $\ce{O2}$ says that the sigma 2p bonding molecular orbital is lower in energy than the pi 2p bonding molecular orbital. Why is this not the case in the $\ce{B2}$ MO diagram? |
I am currently doing doping studies in a system similar to this ($A_{x}B_{1-x}$) and i have to find atomic weight percentage of $B$ element using atomic absorption spectroscopy(AAS). I have prepared different PPM of solutions accoriding to the weight perecntage of $B$ element.
Example to prepare 10 atomic weight per... |
Which of the contributing structures of the resonance below is more stable?
![enter image description here][1]
I'm watching a video lecture by a professor of my college where he puts this question to the class. The class unanimously says **B**. At first I thought they were wrong, but then the professor agreed wit... |
Oxygen with a positive charge more stable? |
I am currently doing doping studies in a system similar to this ($A_{x}B_{1-x}$) and i have to find atomic weight percentage of $B$ element using atomic absorption spectroscopy(AAS). I have prepared different PPM of solutions accoriding to the weight perecntage of $B$ element.
Example to prepare 10 atomic weight per... |
Is oxygen with a positive charge more stable? (comparison of canonical structures) |
>***Which of the contributing structures of the resonance below is more stable?***
>![enter image description here][1]
I'm watching a video lecture by a professor of my college where he puts this question to the class. The class unanimously says **B**. At first I thought they were wrong, but then the professor ag... |
My book gives me the following problem:
"A mixture of 125,0 g dinitrogen en 32,0 g dihydrogen reacts to 36,5 g ammonia. Calculate the efficiency."
My method to do this is - one I learned from my teacher, to put every given molecule's amount of substance (moles) in a table with 3 steps: start (S), gone (G)/formed (F... |
As far as i know a big equilibrium constant shows that the reaction wants to get complete , $$\ce{A <=> B}$$ if A and B are gases then K is $$\frac{[A]}{[B]}$$ but when I multiply the reaction by 20 , K is $$\frac{[A]^{20}}{[B]^{20}}$$ while the same moles of A are consumed . if first K = 10 then the second K is $$10^{... |
why equilibrium constant changes when the reaction is multiplied by a number? |
why does equilibrium constant change when the reaction is multiplied by a number? |
As far as i know a big equilibrium constant shows that the reaction wants to get complete , $$\ce{B <=> A}$$ if A and B are gases then K is $$\frac{[A]}{[B]}$$ but when I multiply the reaction by 20 , K is $$\frac{[A]^{20}}{[B]^{20}}$$ while the same moles of B are consumed . if first K = 10 then the second K is $$10^{... |
Why do the more easily oxidized elements displace the less easily oxidized elements?
Question inspired by Activity Series of Metals |
Why are more easily oxidized elements more reactive than less easily oxidized elements? |
I'm having trouble drawing this molecule because I don't understand how the functional group Phenyl (by -ene suffix) can also be a substituent (by 1-phenyl). Also, what does the 1,3-butadiene mean? |
How do you draw (E)-1-phenyl-1,3-butadiene? |
The most stable conformation of optically inactive Butane–2,3–diol is:
(A)![enter image description here][1]
(B)![enter image description here][2]
(C)![enter image description here][3]
(D)![enter image description here][4]
[1]: https://i.stack.imgur.com/ZII1f.jpg
[2]: https://i.stack.imgur.com... |
Which is most stable conformation of optically inactive Butane–2,3–diol? |
Firstly, the phenyl group is just a benzene with a hydrogen removed:
![enter image description here][1]
In other words, $\ce{C6H5 -}$.
> the functional group Phenyl (by -ene suffix) can also be a substituent (by 1-phenyl).
The -ene suffix is about the double bonds in the system, in this case it applies to ... |
ManishEarth put together the pieces to understand the *connection* of the atoms to form the molecule. Yet since the molecular structure requested in the original post is about [(*E*)-1-phenyl-1,3-butadiene][1], the answer actually is opposite *configuration*:
![enter image description here][2]
By convention, alk... |
My book gives me the following problem:
"A mixture of $125.0 g$ $\ce{N2}$ and $32.0 g$ $\ce{H2}$ reacts to $36.5 g$ $\ce{NH3}$. Calculate the efficiency."
My method to do this is - one I learned from my teacher, to put every given molecule's amount of substance (moles) in a table with 3 steps: start (S), gone (G)/f... |
Aluminium oxide is amphoteric. It is easy to see that it is a Bronsted-Lowry base through the following reaction:
$$\ce{Al_2O_3 + 6HCl \rightarrow 2AlCl_3 + 3H_2O}$$
The Alumnium oxide splits and the oxygen accepts a proton, forming water.
But what about the reaction with a base? In my textbook, they say:
... |
How can $\ce{Al_2O_3}$ be called an acid? |
I know that the mole is widely used in chemistry instead of units of mass or volume as a convenient way to express amounts of reactants or of products of chemical reactions.
I'm wondering why people in chemistry still excessively use it for their measurement? To be backward-compatible and consistent with traditional... |
Why do people still use the mole (unit) in chemistry? |
Simply speaking, because it's an appropriate unit to use.
Let's imagine I wanted to measure the length of a rope. What would be an appropriate length to use? Inches? Centimeters? Feet, maybe? It would really be awkward to express it as 0.000189393 miles, or as 304,800,000 nanometers.
(Note: if you can't see why ... |
How can Al2O3 be called an acid? |
Your statement that the "mole is widely used in chemistry **instead** of units of mass or volume.." is misleading. There are [seven base units of measurement](http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf) in the SI system and your question alludes to two, mass and amount. The other 5 are length, time, te... |
Given the similarity in formula between pentane ($\small\ce{CH3(CH2)3CH3}$, b.p. 36.2°C) and neopentane ($\small\ce{C(CH3)4}$, b.p. 9.5°C), why are their boiling points so different? |
Is the rate of heat transfer between two bodies brought into thermal contact dependent upon the different in temperature between them, assuming they each have the same mass?
Imagine two bodies of water connected to each other by an impermeable glass barrier. If the difference between the temperatures is 10 degrees, w... |
Heat transfer dependence on temperature gradient? |
Is there a compound that turns to gas at a certain temperature but if heated more turns back to liquid and if heated more than turn to gas?
Does it exist naturally? Has a such a substance be found? Can such a substance exist? if yes, then why?
Why couldn't at some temperature molecules interact in such a harmo... |
Is there a element that shows this pattern of boiling point? |
As far as i know a big equilibrium constant shows that the reaction wants to get complete , $$\ce{B <=> A}$$ if A and B are gases then K is $$\frac{[A]}{[B]}$$ but when I multiply the reaction by 20 , K is $$\frac{[A]^{20}}{[B]^{20}}$$ while the same moles of B are consumed . if first K = 10 then the second K is $$10^{... |
I've always heard that different isotopes of the same element have exactly the same chemical properties.
But for example, I've read that some compounds which have hydrogen atoms interchanged by deuterium become odorless (this is one of the arguments for the [vibrational theory of olfaction][1]).
> A 2001 study ... |
What happens to the structure of tetrayclines when they expire? |
In the following figure http://cnx.org/content/m44390/latest/Figure_02_01_07.jpg, we can see that the p-orbitals overlap 1s orbital (though very little %). How can an electron in p-orbital be in the 1s orbital at any given point? |
In the following figure ![enter image description here][1]
we can see that the p-orbitals overlap 1s orbital (though relatively very little). How can an electron in p-orbital, be simultaneously in the 1s orbital at any given point in space and time?
[1]: https://i.stack.imgur.com/NQylA.jpg |
How do 1s and 2p orbitals overlap? |
Consider the following sets of problems:
![enter image description here][1]
[1]: https://i.stack.imgur.com/8CNGb.jpg
I was hoping someone could clarify what each checkbox means exactly. All of these answers are incorrect (except the first one with the check marks signifies the correct answers).
For exam... |
Consider the following sets of problems:
![enter image description here][1]
[1]: https://i.stack.imgur.com/8CNGb.jpg
I was hoping someone could clarify what each checkbox means exactly. All of these answers are incorrect (except the first one with the check marks signifies the correct answers).
For exam... |
I have graphite turning into diamond.I need to find the thermal effect of this reaction.How would one write that?I'm not sure how to proceed here.The teacher told us to use oxygen? |
How do I find the thermal effect of this reaction? |
why does equilibrium constant change when the reaction is multiplied by a number and nothing in the real has been changed? |
What exact nomenclature rule define the naming of Glucose 6-phosphate? |
Why is the nomenclature Glucose 6-phosphate, not 6-phosphateglucose? |
>***Which of the contributing structures of the resonance below is more stable?***
>![enter image description here][1]
I'm watching a video lecture by a professor of my college where he puts this question to the class. The class unanimously says **B**. At first I thought they were wrong, but then the professor ag... |
>Which of the contributing structures of the resonance below is more stable?
Technically, neither. Both structures A and B are resonance contributors to the same true structure of the ion. Structures A and B, because they both represent the same species, cannot have different energies, and therefor they cannot have ... |
How can epimerization in a peptide synthesis be detected? And how can we change or modify the coupling conditions to stop epimerization occurring? Thanks in advance. |
How can [epimerization][1] during peptide synthesis be detected? And how can we change or modify the coupling conditions to stop epimerization occurring? Thanks in advance.
[1]: http://en.wiktionary.org/wiki/epimerization |
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