All Questions
Tagged with free-energy physical-chemistry
104
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
161
views
Criterion for Spontaneity for Closed Systems at Constant Volume and Pressure
For a closed system at constant temperature and volume, the criterion for spontaneity is $dA < 0$. However, for a system at constant composition, the total differential of $A$ is given by
$$dA = -...
- 281
11
votes
2
answers
1k
views
Why would there be a non-zero Gibbs energy of mixing for ideal gases?
When two ideal gases $\ce{A}$ and $\ce{B}$ mix, they don't interact. The chemical potential of each gas is independent of the other, e.g. for $\ce{A}$:
$$\mu_\ce{A} = \mu_\ce{A}^\circ + R T \ln \frac{...
- 41.2k
0
votes
2
answers
414
views
∆G or ∆G° to predict spontaneity
I have a doubt about using Gibbs free energy to predict the spontaneity of a reaction.
It is shown that ∆G = ∆G° + RT ln (Q).
That said, in order to predict which direction the reaction spontaneously ...
- 127
2
votes
2
answers
114
views
Is there an algebraic form for the textbook reaction coordinate curves?
So here is a curve often used in textbooks to illustrate a reaction coordinate.
It's a nice short-hand device to learn the relationship between kinetic and thermodynamic parameters that control the ...
- 731
6
votes
2
answers
246
views
Interpretation of Helmholtz energy and Gibbs energy
I know that this question has many other variations on this site, but I'm trying to see if I understood Helmholtz and Gibbs energy properly or not. The material I'm reading from is Physical chemistry ...
- 297
0
votes
0
answers
97
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Why is the Gibbs free energy of titanium(IV) chloride reduction to titanium metal positive?
I use the Ellingham diagram to find the Gibbs free energy at the equilibrium state to find the partial pressure of chlorine. I have to use the Van 't Hoff reaction isotherm and the partial pressure of ...
- 21
0
votes
1
answer
905
views
Standard Gibbs free energy when all the reactants and products are at standard condition
I have read in my textbook that for a reaction $\Delta G=\Delta G^o-RT\ln Q $, where $\Delta G^o$ is the Gibbs free energy change when the initial concentration of products and reactants are unity. ...
- 159
5
votes
0
answers
437
views
Is the formation of nitrogen dioxide spontaneous?
I was studying Thermodynamics from my Chemistry textbook (page 181-182, section 6.6 (a)).
I have a question regarding the following text from my book.
Now let us examine the following reactions:
$$\...
- 125
2
votes
0
answers
197
views
Gibbs energy of electron transfer
The reaction Gibbs free energy of a cell is
$\Delta_\mathrm{r}G^\circ = -nFE^\circ, \tag{1}$
and the Gibbs energy of photoinduced electron transfer according to IUPAC is
$$\Delta_\mathrm{ET}G^\circ = ...
user78790
3
votes
1
answer
3k
views
Heat capacity at constant volume and Gibbs free energy
I want to know if it is possible to derive heat capacities, in this case, in constant volume from another thermodynamic Potential which is not the Helmholtz free energy $F$. I am aware of the ...
- 133
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
0
votes
1
answer
80
views
How switching values of $R$, $K_p$ and $K_c$ does not alter the value of change in standard Gibbs energy? [duplicate]
$\Delta_\text r G=RT\ln \frac{Q}{K}$
If we switch $K_p$ from $K_c$, accordingly $Q_p$ will change to $Q_c$. Therefore, value of $\Delta_\text r G$ remains the same.
$��G^\circ=−RT\ln K=ΔH^\circ−TΔS^\...
- 1,280
1
vote
0
answers
207
views
Maximum non-PV work and reversibility at constant temperature and pressure
When we talk about systems at constant temperature and pressure, maximum amount of non-PV work can be extracted if process is carried reversibly and in that case it is equal to change in Gibbs energy ...
- 865
0
votes
0
answers
99
views
Entropy and Gibbs Free Energy of Chelate Complexes
Of [Cd(NH2CH3)4]2+ and [Cd(en)2]2+ the stability of the latter is higher than the former attributing to chelation in the en complex .This is evident from the fact that the Gibbs Free Energy change for ...
- 682