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32
votes
4 answers
Why does pyrite form cubic crystals?
Pyrite ($\ce{FeS2}$) forms cubic crystals, like these ones:
I know that the crystal structure is primitive cubic, but I don’t see how cubic structure on the molecular level translates to cubic structure on much larger scales. If you are given some…
math_lover
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32
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Why are solids and liquids not included in the equilibrium constant? What about in a reaction rate calculation?
Take for instance the reaction
$$\ce{H2(g) + I2(s) <=> 2HI(g)}$$
The equilibrium constant would not include the solid $\ce{I2}$, but why is this? I have read that its concentration is a constant, but what does that mean? If you increase the amount…
1110101001
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32
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1 answer
What caused the flashes in the video footage of Chernobyl?
There is video footage of nearby villages in Pripyat, in the first week after the Chernobyl disaster. When I watch it there are villagers leading normal lives in normal clothing. Some Russian nuclear scientists pass by in full radioactive suits.…
Snack_Food_Termite
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31
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1 answer
How to name binary (inorganic) compounds given their chemical formula, and vice-versa?
How can I deduce the name of a binary (inorganic) compound like $\ce{B2F2}$ or $\ce{N2O4}$, from the formula?
And how can I convert a chemical name like diboron difluoride to the chemical formula?
I don't see why we do not need the numeric prefixes…
Gaurang Tandon
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31
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3 answers
What are angular and radial nodes?
Nodes are the points in space around a nucleus where the probability of finding an electron is zero. However, I heard that there are two kinds of nodes, radial nodes and angular nodes. What are they and what information do they provide of an atom?
Maneesh Dev
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31
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3 answers
Why does the 3rd electron shell start filling up with scandium?
The electron configuration of calcium is 2, 8, 8, 2, where up to that point each shell, asides from the first shell counts up to 8 - why then does scandium have an electron configuration of 2, 8, 9, 2?
What causes the 3rd shell to start filling up,…
user4076
31
votes
3 answers
Why does chocolate melt so easily?
(Yes, I know the question sounds super-trivial... but bear with me here)
Most chocolates (especially milk-chocolate) tend to melt into this sticky (albeit delicious) mess at temperatures slightly above room temperature. Why does this happen?
From my…
paracetamol
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31
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4 answers
What roles do neutrons play in an atom?
An atom typically consists of electrons, protons, and neutrons. Electrons are negatively charged and participate in bonding to stabilize the atom.
Conversely, protons are positively charged and balance the charge of the atom. In addition, their…
Harsh Kumar
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31
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Why is the Vitamin B complex, a "complex"?
I often come across the term "Vitamin B Complex" in my biology classes and innumerable times on the back of multivitamin packets, but what does the term "complex" here, even mean?
I'm still in high-school, and the only times we ever come across the…
paracetamol
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31
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3 answers
What is the physical basis for Hund's first rule?
According to Hund's first rule, a set of degenerate orbitals are singly occupied first, before the second slot in any of the orbitals are populated. This is quite intuitive because electron-electron repulsions would make an atom more unstable if the…
Aniansh
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31
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5 answers
Difference between exothermic and exergonic
In High School I learned that an exothermic reactions releases energy, while an endothermic reaction needs energy to occur. Now I learned that there is a separate, somewhat similar classification scheme of exergonic and endergonic reactions.
What is…
Martin J.H.
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31
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d-orbital splittings in WS2 monolayer
The formerly degenerate $d$ orbitals of the tungsten atoms in the $\ce{WS2}$ monolayer are split into three groups: (1) $\mathrm{d}_{z^2}$, (2) $\mathrm{d}_{x^2-y^2}, \mathrm{d}_{xy}$ and (3) $\mathrm{d}_{xz}, \mathrm{d}_{yz}$ in the order of…
Capo Pavel Mestre
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31
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4 answers
Why are isotopes of hydrogen the only ones with special names?
Why does no other element but hydrogen get special names for its isotopes?
Abhirath Anand
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31
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3 answers
Selective nitro reduction of poly nitro compounds
Is there any way through which I could selectively reduce one $\ce{NO2}$ group from a dinitro- or trinitro- compound to an amine.
I was reading Solomons and Frhyle and it says that m-dinitrobenzene can be selectively reduced by using $\ce{H2S}$ in…
Karan Singh
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31
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3 answers
Are there non-transparent gases?
Are there gases that are not transparent at room temperature (i.e. at temperature below the point where the substance starts to radiate visible light due to heating)?
Anixx
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