## 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

### 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

### 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

### 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

### 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

### 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

### 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

## 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

### 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

### 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

### 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

### 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

### 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

### 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

## 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

### 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