All Questions
45,378
questions
64
votes
7
answers
599k
views
Positive or Negative Anode/Cathode in Electrolytic/Galvanic Cell
In a galvanic (voltaic) cell, the anode is considered negative and the cathode is considered positive. This seems reasonable as the anode is the source of electrons and cathode is where the electrons ...
- 3,256
64
votes
4
answers
59k
views
How can one explain niobium’s weird electronic configuration?
As cited in an answer to this question, the ground state electronic configuration of niobium is:
$\ce{Nb: [Kr] 5s^1 4d^4}$
Why is that so? What factors stabilize this configuration, compared to ...
- 23.8k
64
votes
3
answers
6k
views
Why does pasta really boil over?
I was making pasta, and I noticed the pasta boiling over. I thought about it some more, and I realized I had no idea why this was happening. When the lid is on, the foam rises. When the lid is off, ...
- 852
63
votes
1
answer
9k
views
Why does shaking a match put the fire out?
Move a match slowly and nothing happens but if you shake it violently the fire will extinguish. Oxygen makes fire grow so why does waving a flame through the oxygen rich air put the fire out? Does ...
- 739
61
votes
6
answers
13k
views
Why is FORTRAN so commonly used in computational chemistry?
I've been using Ruby to write scripts for research, but I want to get into some heavier stuff that Ruby is just too slow for. I noticed there are a few things written in C and C++, but there is an ...
- 6,771
61
votes
2
answers
4k
views
Striking examples where Kohn-Sham orbitals clearly have no physical meaning
In Density Functional Theory courses, one is often reminded that Kohn-Sham orbitals are often said to bear no any physical meaning. They only represent a noninteracting reference system which has the ...
- 23.8k
60
votes
4
answers
246k
views
Why add water first then acid?
From school, I remember a very important rule: first you need to pour the water and then the acid (when you need to mix them) not vice-versa. This is because otherwise the aсid becomes very hot and ...
- 1,053
60
votes
4
answers
18k
views
Are diamonds really forever?
Common saying. Diamond possesses:
ultra hardness, (10 on the Mohs scale; 10000 HV on Vicker's Hard Test (iron merely 30-80))
hyper thermal conductivity, ($2320~\mathrm{W\, m^{-1}\, K^{-1}}$, or over ...
- 2,247
59
votes
4
answers
29k
views
Why do shampoo ingredient labels feature the term "Aqua"?
I keep seeing the term "Aqua" in the ingredient labels on several shampoo varieties, but I really don't see why it should be there in the first place.
I mean, if the manufacturers just wanted to say ...
- 18.8k
57
votes
4
answers
385k
views
Why is it important to use a salt bridge in a voltaic cell? Can a wire be used?
I was learning about voltaic cells and came across salt bridges. If the purpose of the salt bridge is only to move electrons from an electrolyte solution to the other, then why can I not use a wire?
...
- 799
56
votes
3
answers
14k
views
Why do we write NH3?
We've learnt that the electropositive element is written first. Then why is ammonia written as $\ce{NH3}$ ?
- 1,273
56
votes
6
answers
12k
views
The last element's atomic number
I was just thinking what can be the last atomic number that can exist within the range of permissible radioactivity limit and considering all other factors in quantum physics and chemical factors.
- 1,252
56
votes
5
answers
10k
views
How can antibonding orbitals be more antibonding than bonding orbitals are bonding?
In molecular orbital theory, the fact that a bonding and antibonding molecular orbital pair have different energies is accompanied by the fact that the energy by which the bonding is lowered is less ...
- 6,795
55
votes
4
answers
799k
views
How do I figure out the hybridization of a particular atom in a molecule?
I'm learning how to apply the VSEPR theory to Lewis structures and in my homework, I'm being asked to provide the hybridization of the central atom in each Lewis structure I've drawn.
I've drawn out ...
- 6,771
55
votes
2
answers
58k
views
What makes some metals melt at higher temperature?
I'm looking at the melting temperature of metallic elements, and notice that the metals with high melting temperature are all grouped in some lower-left corner of the $\mathrm{d}$-block. If I take for ...
- 23.8k