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1500 questions
15
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1 answer
Why a higher s character increases a carbon atom's electronegativity?
To make us understand certain phenomenon like the higher acidity of alkynes than alkanes and alkenes, our teacher told us to learn this as a general rule:
Higher s character leads to a more electronegative carbon atom.
Note: By s character I mean…
Amritansh Singhal
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15
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5 answers
Can flames be colored black?
Most of us here would know that flames can be colored by adding an appropriate salt to the 'fuel' or by simply introducing it into a flame. Boron and Barium salts give the flame a green tinge, Strontium colors it red, Sodium does gold, copper a…
paracetamol
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15
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2 answers
Reaction of glucose with 2,4-dinitrophenylhydrazine (DNPH)
In its open-chain form, glucose possesses an aldehyde group; however, glucose does not test positive with 2,4-dinitrophenylhydrazine (which typically forms a yellow/orange/red precipitate with carbonyl compounds).
Why is this so? Is this a…
Manish Bhatt
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15
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3 answers
Why are only sigma bonds used in determining the geometry and bond angle in VSEPR theory? Why aren't pi bonds used?
I have read that in VSEPR theory, multiple bonds are considered or treated as single bonds when predicting the geometry of a molecule? I've read in Yahoo! Answers that it is because only sigma bonds are used in determining their shape. What's the…
Raniella C.
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15
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1 answer
Why is the carbon dioxide we exhale transparent?
Why is carbon dioxide that comes from dry ice opaque and smoky while the carbon dioxide that we exhale transparent?
Krikor Ailanjian
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15
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2 answers
Why is O2 the supporter of combustion?
It's there in every high-school textbook: $\ce{O2}$ is the supporter of combustion. Without $\ce{O2}$ combustion cannot take place. Why? And why only $\ce{O2}$? Why not some other element?
And, what happens when a combustible gas burns in air? Say…
Gerard
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15
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2 answers
What are typical runtimes for CASSCF calculations?
I'm doing single point energy calculations of FeS using ORCA. I originally used DFT with a variety of functionals, and these calculations all took less than a minute. Now I'm attempting to run CASSCF calculations using 8 active orbitals, 12 active…
Argon
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1 answer
Receiving milk for working in harmful environment
I just got a job in a chemical/biological lab (post-Soviet Country). Chemists here receive milk for "harmfulness of the work" (i .e. their work involves working with all kind of substances/reactives). I'm not a chemist; I do their analysis. The…
mil'
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Why are the densities of europium and ytterbium anomalously low?
Why do europium and ytterbium have lower densities than expected in comparison to other lanthanides? I know it has something to do with the fact that they have half-full and full 4f subshells in the +2 oxidation state, but how exactly does it relate…
waterlemon
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15
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4 answers
Why exactly does molten NaCl explode, when it is poured into water?
Why does molten $\ce{NaCl}$ explode, when it is poured into water?
$\ce{NaCl}$ has a high melting point, $1074\ \mathrm{K}$ ($801~\mathrm{^\circ C}$). $\ce{NaCl}$ has a molar mass of $58.44\ \mathrm{g/mol}$, it has specific heat capacity of $36.79\…
shre_sudh_97
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15
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2 answers
Molecular knots absolute configuration
How is the absolute configuration of chiral molecular knots determined? What rules should be applied? For centrochiral compounds, the CIP rules are applied, for axially chiral is described here and for planar chiral here. I can't find the system for…
EJC
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15
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2 answers
Why does KCl come in amber coloured bottles?
I remember from school that photosensitive chemicals are kept in amber coloured bottles. Is KCl photosensitive? I read up the impurities list on the bottle and it says that it may have bromides too? So is it because of the KCl or the bromides? If it…
Polisetty
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15
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3 answers
What is the difference between ΔG and ΔrG?
Consider the reaction
$$\ce{A -> B}$$
The reaction Gibbs free energy, $\Delta_\mathrm{r} G$ is given by the following equation
$$\Delta_\mathrm{r} G = \Delta_\mathrm{r} G^\circ + RT \ln Q$$
Now what is the difference between $\Delta G$ and…
CLAP or SLAP II
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1 answer
Why does LiAlH4 reduce an amide to an amine, but only reduce a ketone/aldehyde to an alcohol?
Here are two different reactions in which lithium aluminium hydride, $\ce{LiAlH4}$, reduces a carbonyl group:
Why does $\ce{LiAlH4}$ completely remove the oxygen from the amide, but only reduces the carbonyl group of a ketone/aldehyde to a hydroxyl…
mshum
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15
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4 answers
Are modern newspaper inks a health risk?
It's very common in India to see newspapers being used to absorb oils from oily snacks, or simply for temporary food packaging. Some articles say that covering food items in newspaper is a health risk. They also mention that using newspapers for…
NVZ
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