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1500 questions
18
votes
3 answers
Why is the enthalpy change not zero in an adiabatic process?
Which of the following must be true for adiabatic processes?
$C_V = C_p$
$\Delta H = 0$
$\Delta U = 0$
$\Delta S = 0$
$q = 0$
(Source: Chemistry GRE)
The answer is $q = 0$. From what I can find, an adiabatic process is when there is no transfer…
halcyon
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18
votes
3 answers
Can an aqueous solution conduct electricity forever?
We know that pure water does not conduct electricity, but salt water is a decent conductor. This is commonly explained by saying that “the ions carry the current through the solution”, which is an incomplete explanation, because it does not …
DanHickstein
- 377
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18
votes
3 answers
Hybridisation of Mn in potassium permanganate
I'm clear with the concepts of crystal field theory. But I can't figure out the exact reason why the hybridisation of manganese in potassium permanganate ($\ce{KMnO4}$) is $\mathrm{d^3s}$. Can anyone explain please?
Devgeet Patel
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18
votes
2 answers
Why is use of calcium carbide as an artificial fruit ripening agent banned?
Fruits like mangoes can be ripened using agents like ethylene, acetylene or calcium carbide. Of these, the latter is dangerous and is banned in most countries. Wikipedia says it is because calcium carbide has traces of arsenic and phosphorus. Is…
Ashwin
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18
votes
1 answer
How does a chemical "know" which other species are present and where equilibrium is?
Please forgive me if this is a vague question. I have always wondered how a chemical reaction "knows" where its equilibrium should be. For example, using a basic example of Le Chatelier's principle, for some theoretical reaction
$$\ce{A + B <-> C +…
Arcadium
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18
votes
5 answers
The Lewis structure of HNO3
So I was checking the structure of nitric acid in Wikipedia, however I couldn't quite fathom why it looked like that because it seemed to contradict the following statement:
A Lewis structure with small or no formal charges is preferred over a…
Zafer Cesur
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18
votes
3 answers
Have there been no advances in the determination of effective nuclear charges since Clementi and Raimondi in the 60s?
Effective nuclear charge is a very important concept in chemistry, and is the basis for the qualitative explanation of many observed chemical and physical properties, including several periodic trends. Hence it seems to me to be of significant…
Nicolau Saker Neto
- 28,697
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18
votes
3 answers
Ozonolysis conditions for benzene
What are the precise conditions under which benzene undergoes ozonolysis? All anyone can tell me is that it undergoes ozonolysis under "vigorous" conditions. But, what vigorous conditions?
Keerthana A.K.
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18
votes
1 answer
How does Polytetrafluoroethylene (Teflon) differ from Polyvinylidene fluoride (PVDF) as a protein binding membrane material?
PTFE and PVDF (durapore) are both used in protein binding filter membranes (Millipore specifically). Chemically speaking the two polymers differ quite significantly due to the additional fluorides and molecular weight. Their protein-binding…
bobthejoe
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18
votes
5 answers
Why can't I balance this reaction algebraically?
$$\ce{aCu + bHNO3 -> cCu(NO3)2 + dNO + eH2O}$$
(Source)
I calculated:
\begin{align}
a &= c &(\ce{Cu})\\
b &= 2e &(\ce{H})\\
b &= 2c + d &(\ce{N})\\
3b &= 6c + d + e &(\ce{O})
\end{align}
And I tried substituting $a= 1$, but it couldn't solve…
MCCCS
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18
votes
3 answers
Any false chemical element in history of chemistry?
Was there any false chemical element introduced in history of chemistry? I mean a substance that after a while proved that it was not an element.
Bahribayli
- 299
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18
votes
1 answer
How can I draw metallocenes in ChemDraw?
How can I properly draw the structure of metallocenes (e.g. ferrocene) and similar sandwich compounds in ChemDraw?
In particular, two problems cannot be solved with the usual workflow when building a molecule in ChemDraw:
How can I draw a bond…
user7951
18
votes
3 answers
Modern open-source tools for simulation of NMR spectra
I am interested in predicting the NMR spectrum of small organic compounds. It doesn't matter to me if the prediction is very accurate. I'll eventually be comparing the prediction to experimental results.
It looks as if several free online tools…
Curt F.
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- 115
18
votes
2 answers
Using table salt as a way to limit humidity in an unoccupied house
We own a static caravan in the UK (Snowdonia region, so rainy and wet all year round, moderately cold winters) and we leave it unoccupied during Winter (Oct-Feb).
We were advised of an apparently common practice among caravan owners which is to…
Wossname
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18
votes
1 answer
Fehling's test arrow pushing mechanism
I am currently attempting to generate an arrow pushing mechanism for the oxidation of glucose to gluconic acid using Fehling's solution. My original thought was to go the route of alcohol oxidation using acidified dichromate where the alcohol…
Jason Woodgate
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