All Questions
Tagged with theoretical-chemistry thermodynamics
27
questions
114
votes
1
answer
6k
views
Is there a general consensus on the causes of the alpha-effect?
There have been various explanations posited for the α-effect. The α-effect refers to a phenomenon wherein nucleophiles with lone pairs on atoms adjacent (i.e., in the α- position) to the atom bearing ...
- 11.9k
18
votes
1
answer
732
views
What is the relation between surface tension and initial molecular harmonic?
Initial harmonic is measured as Hartree/Bohr^2 ( like IHarmonic=n in Gaussian Software ). As I am from physics background I am used to look at features from their dimension point of view:
Actually ...
- 2,141
16
votes
1
answer
13k
views
Why is there sulfur in black powder / gun powder?
Black powder is composed of charcoal, sulfur and a nitrate salt. The charcoal and sulfur serve as fuel and the nitrate is the oxidizing agent.
However, wouldn't it be cheaper to leave out the sulfur, ...
- 10.9k
12
votes
1
answer
3k
views
How to make approximation of rotational partition function of diatomic linear molecules?
Using the rigid rotor approximation to the level energies, and such other appropriate assumptions, we can approximate rotational partition function, $Q_{\mathrm{rot}}$, of linear molecules as follows:
...
- 181
11
votes
2
answers
2k
views
How does an oscillating reaction work?
I watched a Belousov--Zhabotinsky reaction video showing an orange solution that goes to clear and then back to orange (and so forth.)
The reaction goes through a number of cycles before it will no ...
- 6,801
8
votes
2
answers
588
views
Practical use of the partition function in molecular simulations
In the second chapter of Understanding Molecular Simulation, Frenkel and Smit derive an equation for the partition function and the thermal average of the generic observable A, stating that these ...
8
votes
1
answer
2k
views
Why is N₂ stable but HCN and C₂H₂ unstable?
Compounds with triple bonds generally seem to be unstable. $\ce{HCN}$ and $\ce{C2H2}$ are high-energy, relatively short-lived molecules that will readily polymerise or react with other organic ...
- 1,661
7
votes
1
answer
2k
views
Calculating internal energy of methane
I've recently found out my calculated value of internal energy of methane largely deviates from the ab initio output (at $\pu{1000 K}$ $0.058~\text{Hartree} = \pu{152.3 kJ mol-1}$). I used HF method, ...
- 303
6
votes
2
answers
327
views
Tunneling in chemical reactions
We know that quantum tunneling is the reason behind several natural phenomenon like alpha decay and thermonuclear fusion inside the stars. How can it influence chemical reactions by tunnelling a ...
6
votes
1
answer
237
views
Non-Arrhenius temperature dependence of bimolecular reaction rates at very high temperatures
Once I have read that in some cases bimolecular reactions can exhibit a maximum as a function of temperature due to the short lifetime of the activated complex at very high temperatures.
At low ...
- 163
6
votes
2
answers
814
views
Measuring Thermodynamic Stability
We can predict whether a reaction can occur spontaneously by calculating the change in Gibbs' free energy.
I was just wondering whether there is any general measure of the thermodynamic stability of ...
- 2,135
6
votes
1
answer
197
views
Understanding elementary rate laws from a probability stand point
I am learning about chemical kinetics and dynamics and as I understand for a general chemical reaction
$$\ce{aA + bB -> cC + dD} $$ whose reaction rate, r, can be described by an elementary rate ...
- 61
4
votes
1
answer
208
views
Plasma creation and condensation
Every chemical has a decomposition temperature. My understanding is that above that temperature molecular bonds are broken. And if we raise the heat high enough then all molecular bonds will break ...
- 3,340
4
votes
1
answer
998
views
How to estimate the dielectric constant of a liquid?
Are there any approximate relationships between the (static) dielectric constant of a liquid and properties of the individual molecules?
For example, suppose I know the polarizability and dipole ...
- 917
3
votes
1
answer
2k
views
Electrode potentials at interfaces?
My questions relates to the fundamental concept of electrochemistry, more specifically the electrode potentials.
1) First, why is there a potential difference at the interface of two phases? ...
- 6,795