All Questions
Tagged with theoretical-chemistry thermodynamics
27
questions
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
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 ...
CommunityBot
- 1
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? ...
- 4,606
6
votes
1
answer
237
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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 ...
- 30.8k
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 ...
- 4,606
2
votes
0
answers
84
views
Diffusion vs mobility and the Einstein relation
This former question is about the mobility constant $M>0$ in the Cahn-Hilliard equation. To determine the value of such a mobility for a simulation study, Kim and Sanders (2020)
use the formula
$$
...
- 193
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 ...
- 116
1
vote
0
answers
55
views
Why probability for an atom is fraction for population?
In the canonical ensemble the probability of finding an atom (or molecule) in its $i$-th energy state is given by the Boltzmann factor.
This probability is interpreted as the number of microstates ...
- 766
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 ...
3
votes
0
answers
21
views
Correlating specific heat (Cp) of a substance with other substance on the basis of similar physio-chemical properties
I am modelling $\ce{H2O2}$ decomposition in ANSYS Chemkin-Pro and I have difficulty finding $C_p$ (specific heat at constant pressure) for liquid $\ce{H2O2}$ for various temperature ranges.
My ...
- 38.4k
2
votes
0
answers
32
views
expression of apparent reaction quotient
question
When computing the Gibbs energy change of a reaction using Legendre-transformed $\Delta_fG'$ values for a given $\mathrm{pH}$, the formula of the $\Delta_rG'$ of the reaction is:
$\Delta_rG' ...
- 306
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 ...
1
vote
0
answers
44
views
What makes determining entropy changes theoretically so hard compared to enthalpy?
It is really hard to determine the entropy change of a reaction accurately because of subtle solvent effects and a lack of standard entropies. On the other hand, enthalpy is relatively easy and ...
- 732
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 ...
CommunityBot
- 1
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, ...
- 38.4k