Chemistry Stack Exchange Community Digest

Top new questions this week:

Could a positron be made to stably orbit an atom?

Suppose you have a single atom of neon, argon or some other noble gas of your choice. While the entire atom is electrically neutral a nearby positron would probably be more strongly attracted to the ...

quantum-chemistry orbitals atomic-structure nuclear-chemistry  
asked by frogeyedpeas 6 votes
answered by Pallas 4 votes

NMR terminology: "Transients"

I was reading a paper on hyphenating a gas chromatograph with an NMR. The authors describe a proof-of-concept type instrument. We have a couple of NMR experts here in SE, hoping to get some insight. ...

nmr-spectroscopy  
asked by M. Farooq 6 votes
answered by orthocresol 14 votes

Do the phosphoester and glycosidic bonds of dNTPs increase thermal stability?

A while ago, I provided an answer to a question on Biology.SE concerning the half-life of dNTPs under PCR conditions. At the beginning of my answer, I give a qualification: Caveat: ignoring the ...

organic-chemistry biochemistry stability  
asked by acvill 3 votes

Best bet for separating fused glassware

I have a sintered glass funnel stuck in a flask with a 24/40 ground glass joint. I regularly used this glassware to process very dilute solutions of uncured photopolymer resin dissolved in ethanol. ...

equipment cleaning  
asked by Jason C 3 votes

If a carbonic acid to bicarbonate reaction involves the release of H+, why does pH increase?

OK, I'm an engineer that took Aqueous Geochem 6 years ago, so please forgive this basic (get it?) question. But why do the two reactions which start from dissolution of CO2 in water increase pH if ...

ph  
asked by Mike Kelly 3 votes
answered by BrownBag 2 votes

What is an example of an exothermic reaction with negative ∆S?

In high school we learn that when a reaction has both negative $\Delta{}S$ (entropy change) and negative $\Delta{}H$ (enthalpy change) it occurs spontaneously at lower temperatures, but becomes non-...

thermodynamics enthalpy entropy spontaneity  
asked by Krzysztof PalatyƄski 3 votes
answered by Nicolau Saker Neto 10 votes

Why did these magnetic ball bearings corrode?

Before the pandemic, I bought a set of magnetic ball bearings (a few mm in diameter) and attached them to a side panel of my desk (presumably, the panel is iron coated in grey paint). On returning to ...

corrosion  
asked by user168715 2 votes
answered by AJKOER 1 vote

Greatest hits from previous weeks:

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 ...

thermodynamics enthalpy free-energy  
asked by Martin J.H. 30 votes
answered by Buttonwood 42 votes

How to convert g/L to mol/L

I know I should divide $\pu{g L-1}$ by the molar mass of the substance, but I don't seem to find the specific answer on Google. So just to be sure: If I have $10^{-5}~\pu{g L-1}~\ce{Cu^2+}$ solution, ...

concentration stoichiometry units  
asked by Ndrina Limani 2 votes
answered by bon 8 votes

What are t2g and eg in CFT?

In the crystal field theory (CFT), when the splitting of the d-orbital occurs, it gets divided into two parts. The upper part with higher energy is the $\mathrm{e_g}$ and the lower part with lower ...

coordination-compounds molecular-orbital-theory notation symmetry group-theory  
asked by NeilRoy 24 votes
answered by AngusTheMan 32 votes

Why lanthanides and actinides are shown separate from standard Periodic Table layout?

In the standard Periodic Table layout , all the elements up to 56 are in order i.e are in the same layout table. However, lanthanides and actinides are always shown separately from the layout like in ...

periodic-table history-of-chemistry  
asked by SRy 13 votes
answered by Uncle Al 12 votes

Why is the 2s orbital lower in energy than the 2p orbital when the electrons in 2s are usually farther from the nucleus?

My chemistry book explains that even though electrons in the $\mathrm{2p}$ orbital are closer to the nucleus on average, electrons from the $\mathrm{2s}$ orbital spend a very short time very close to ...

energy electrons quantum-chemistry orbitals  
asked by Gordon Gustafson 87 votes
answered by Philipp 66 votes

What is the difference between the KLMN and SPDF methods of finding electronic configuration?

I've always been puzzled by this because my teachers happen to use only the KLMN method, but what is the difference between the KLMN and SPDF methods of finding electronic configuration?

electronic-configuration  
asked by Madhav Sudarshan 5 votes
answered by Ben Norris 11 votes

How does one tell if a specific molecule is acidic or basic?

Let's take the $\ce{KOH}$ molecule into account. I know it is a base from literature, but how would one go about determining if a molecule is acidic or basic simply based on the structure of the ...

acid-base molecular-structure  
asked by 2567655222 25 votes
answered by bobthechemist 20 votes

Can you answer these questions?

Converse of ΔU = 0 for isothermal processes: is it true?

For an ideal gas undergoing an isothermal process $\Delta U = 0.$ But is the converse true? Let's say, $\Delta U$ for an ideal gas is zero. Is its temperature constant then? Can we say that it's ...

physical-chemistry thermodynamics ideal-gas  
asked by Sephin 1 vote

The mechanism of discoloration due to changes in the state of CP

I don't know the mechanism of discoloration due to phase change. https://pubs.rsc.org/en/content/articlelanding/2019/cc/c9cc02172h In the above paper, Cu(I) in CP1 (Figure 1 a) has a tetrahedral ...

coordination-compounds spectroscopy phase color uv-vis-spectroscopy  
asked by kkkkk 1 vote

Isomerization of tertiary carbocations in cholesterol synthesis

The following reaction mechanism happens in cholesterol synthesis inside human body. I am unable to understand why on earth the hydride shift happens here. I mean its already a tertiary carbocation, ...

organic-chemistry biochemistry  
asked by user3001408 2 votes
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