Chemistry Stack Exchange Community Digest

Top new questions this week:

Is it possible to achieve a level of "truly zero" concentration?

If we take some aqueous solution and dilute it further and further, will the concentration of the solution ever get to zero? I would say no, simply because total dilution implies that all the ...

aqueous-solution concentration molecules  
asked by Kara Kirkland 15 votes
answered by Raphaël 35 votes

What is a Herzberg?

Whatman lists the flow rates for their filters in a unit called a 'Herzberg': What is this? I've been searching around and I did find information about Herzberg flow rate testers, for example this ...

physical-chemistry terminology units filtering  
asked by Jason C 14 votes
answered by Mathew Mahindaratne 16 votes

Why can radioactive contamination be spread by people?

So I am reading a book called "Voices from Chernobyl" where witnesses, nuclear plant workers, firefighters and other persons involved in the 1986 accident give testimony of their ...

safety radioactivity  
asked by Matias Barrios 14 votes
answered by cbeleites unhappy with SX 26 votes

Do we have some "rule of thumb" to estimate the miscibility of metals?

For example, for ordinary fluids, we have polar and apolar ones. The "rule of thumb" is that polar fluids mix with each other, and also apolar fluids mix with each other, but polar fluids ...

metal alloy immiscibility  
asked by peterh - Reinstate Monica 6 votes
answered by Jon Custer 9 votes

Are there reactions where stirring direction would make a difference?

I'm not a chemist. I don't really do anything with chemistry, so I know little of the subject. I know a bit about chiral molecules. For example, I know that homochirality can affect light polarity. ...

asked by John Zhau 6 votes
answered by Karl 8 votes

Diastereomers or not

Why is the first one not a pair of diastereomers while the second is? The only reason I could think of was in the first $\ce{Me}$ is the same as $\ce{CH3}$ that is same groups even though differently ...

organic-chemistry stereochemistry isomers  
asked by Shaurya Goyal 6 votes
answered by Mathew Mahindaratne 6 votes

Help with mechanism similar to Robinson Annulation

I need to figure out a mechanism for this reaction. All I know is that it is supposed to have a similar mechanism to Robinson Annulation. This is the best I could come up with, but I've been told it ...

organic-chemistry carbonyl-compounds enolate-chemistry  
asked by dfalkjl3 4 votes

Greatest hits from previous weeks:

What is the inert pair effect?

I was reading about the p-block elements and found that the inert pair effect is mentioned everywhere in this topic. However, the book does not explain it very well. So, what is the inert pair effect? ...

inorganic-chemistry quantum-chemistry orbitals periodic-trends relativistic  
asked by radiantshaw 39 votes
answered by Philipp 35 votes

How to decide acidic or basic nature of oxides

How can we theoretically decide the acidic or basic nature of an oxide? What are the reasons/ factors which make an oxide acidic, basic, amphoteric or netural?

asked by shailendra 11 votes
answered by Yomen Atassi 15 votes

Why do branched chain compounds have lower boiling points than the corresponding straight chain isomers?

The branched chain compounds have lower boiling points than the corresponding straight chain isomers. For example, $\ce{CH_3CH_2CH_2CH_2CH_3}$ - No branching-Pentane (n-pentane) ...

organic-chemistry physical-chemistry  
asked by Immortal Player 23 votes
answered by matt_black 14 votes

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. 28 votes
answered by Buttonwood 39 votes

Reaction of silver nitrate and hydrochloric acid

Consider the reaction of $\ce{AgNO3}$ and $\ce{HCl}$. I read that silver chloride would be formed. But $\ce{H} > \ce{Ag}$ in reactivity, then how could $\ce{Ag}$ displace $\ce{H}$ from $\ce{HCl}$ ? ...

inorganic-chemistry precipitation  
asked by Mriganka Basu Roy Chowdhury 8 votes
answered by thomij 13 votes

Is there an easy way to remember charges on ions?

I have a chemistry test coming up and I might need to know the charge that goes with the different ions like $\ce{SO4}$ has $-2$, $\ce{NO2}$ is $-1$ and $\ce{PO4}$ is $-3$. Is there an easy way to ...

physical-chemistry ions  
asked by Chef Flambe 10 votes
answered by Mark 10 votes

What is the pKa Range for weak acids and bases?

Am I correct in assuming that the following is true? $\mathrm pK_\mathrm a < 3$ is for a strong acid $3 < \mathrm pK_\mathrm a < 7$ is for a weak acid $7 < \mathrm pK_\mathrm a < 11$ ...

physical-chemistry acid-base ph  
asked by user2679447 4 votes
answered by ShuklaSannidhya 10 votes

Can you answer these questions?

Grasping the concept of Electronic Spin, Effective Spin and Fictitious Spin

Trying to learn alone some aspects of quantum mechanics is, sometimes, a struggle. Reading the excellent paper by Piwowarska (DOI 10.1007/s00723-018-1080-4) I was hoping to, finally, understand what ...

quantum-chemistry computational-chemistry electrons spin epr-spectroscopy  
asked by Henrique Junior 1 vote

Why do atoms on the periodic table have the number of valence electrons that they do?

I'm studying year 11 and am learning about valence electrons and how these electrons drive intermolecular bonds. What I have not been able to find an explanation to is why all the elements on the ...

asked by Corey King 1 vote
answered by DrMoishe Pippik 0 votes

State of matter identifier (c) in chemical reaction equations

I stumbled across an equation, where (c) is used to identify the state of matter, e.g.: $$ \ce{Ni_{(c)}} $$ I am familiar with (s), (l) and (g) for solid, liquid and gaseous respectively. From the ...

asked by MiB_Coder 1 vote
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