All Questions
Tagged with free-energy energy
36
questions
4
votes
1
answer
101
views
Gibbs energy of an imperfect crystal
Our materials professor likes to do Kahoot quizzes and I am confused about why the following statement is true:
A defect in a crystal gives it higher energy.
I know that an imperfect crystal has a ...
- 211
0
votes
1
answer
115
views
What is the difference between standard Gibbs energy and Gibbs energy of formation?
Good day guys,
I am reading a book on electrochemical engineering, I came across some definitions of Gibbs energy and I am a bit confused as the book does not go into a lot of detail.
The book first ...
- 265
0
votes
1
answer
483
views
Gibbs free energy versus reaction progress plots
I am trying to make sense of these two graphs. They appear to have similar axes, yet display different curves.
Please let me know if this understanding is correct:
In the top image (x-axis = "...
- 11
0
votes
0
answers
51
views
Enthalpy and Bond Energy Sign Convention
I read that a negative enthalpy of formation means an exothermic reaction. Does that mean this reaction is true? The enthalpy of formation for $\ce{H_2O}$ is -285.8 kJ/mol.
$$\ce{2H2(g) + O2(g) -> ...
- 101
0
votes
1
answer
324
views
Why is the Gibbs free energy of a reversible reaction not always 0? [duplicate]
From my understanding, reversible proceses are those where the expression:
$$\Delta S_\mathrm{total} = \Delta S_\mathrm{system} + \Delta S_\mathrm{surroundings} = 0$$
is true for all for the entire ...
- 19
-1
votes
1
answer
223
views
Finding Gibbs energy at different temperatures just given Gibbs energy at one temperature
How would it be found the Gibbs energy at a certain temperature, if they just give you another Gibbs energy at a temperature? For example: Given $\Delta G = -230 Kcal/mol$ at $773K$ for the reaction $...
- 1
2
votes
1
answer
586
views
Calculation of free energy from potential and kinetic energy
I am having trouble understanding how (and even whether it's possible) to get free energy from kinetic and potential energy.
I have run molecular dynamics simulations (NPT ensemble, CP2K software), ...
- 149
0
votes
0
answers
1k
views
Calculating Gibbs free energy for the reaction of burning methanol
Calculate $Δ_\mathrm{r}G^\circ$ for the following reaction:
$$\ce{2 CH3OH(l) + 3 O2(g) -> 2 CO2(g) + 4 H2O(l)}$$
using $Δ_\mathrm{r}H^\circ$ and $Δ_\mathrm{r}S^\circ$ at $\pu{298.13 K}$ $(\pu{25 °C}...
1
vote
1
answer
52
views
Ground state elevation for phase transition
I have a question about the illustration from chem.libretexts.org:
the ground states of the liquid and gas are offset from that of the previous state by the heats of fusion and vaporization, ...
- 69
3
votes
1
answer
665
views
Relationship between Gibbs free energy and potential energy (related to reaction coordinate diagrams)
For a rate law, the rate constant $k$ is given by the equation
$$\ln k = \ln A - \frac{E_\mathrm{a}}{RT}\tag{1}$$
If $k_\mathrm{fwd}$ is the forward rate constant and $k_\mathrm{rev}$ is the reverse ...
- 89
3
votes
1
answer
2k
views
Change in heat of photosynthesis
Consider a plant that uses the energy it receives from the sun to do work (to undergo photosynthesis) to produce glucose. The minimum amount of work this plant can do to produce 1 mole of glucose is ...
0
votes
2
answers
2k
views
Could a non-spontaneous reaction occur "on its own"?
Does spontaneity really only apply to the net free energy change of a reaction?
I used to be taught that spontaneous reactions could occur on their own BUT without enzymes or a spark they might take ...
- 169
0
votes
1
answer
451
views
Energy at constant Entropy and Volume
The system of constant entropy and constant volume will attain the equilibrium in a state of minimum energy. Why?
I know that:
$\Delta G= \Delta H-T\Delta S$
And at constant volume and entropy: $\...
- 109
3
votes
2
answers
1k
views
Why energy of some intermediates of glycolysis increases?
It is possible that I do not understand the concept of energy, but according to the diagram in my book, the energy between steps 4 and 5 and between 6 and 8 increases. How is this possible? Also, as ...
- 31
3
votes
2
answers
20k
views
How to calculate Gibbs free energy from pKa?
Is it possible to calculate Gibbs free energy ($ΔG = -RT\ln K_\mathrm{eq}$) of an acid dissociation reaction using the $\mathrm{p}K_\mathrm{a}$? If so, how?
- 41