All Questions
Tagged with equilibrium free-energy
23
questions
42
votes
3
answers
39k
views
What is the difference between ∆G and ∆G°?
In Brady's Molecular Nature of Matter, I read that $\Delta_\mathrm{r} G^{\circ}$ is $\Delta_\mathrm{r} G$ at $25~^\circ\mathrm{C}$. But later, it gives a value for $\Delta_\mathrm{r} G^\circ$ at ...
- 511
25
votes
2
answers
3k
views
Which equilibrium constant is appropriate to use?
I have learnt that the standard free energy change is related to the equilibrium constant of a reaction by,
$$\Delta G^\circ = -RT \ln K$$
Here, does $K$ refer to $K_p$ or $K_c$?
Also, please give ...
- 1,245
14
votes
4
answers
4k
views
Is there a reason for the mathematical form of the equilibrium constant? [duplicate]
Why are the two molarities multiplied and not added, and why is each raised to the power of the coefficient rather than multiplied by it? What is the reasoning behind this form? Was it simply ...
- 939
3
votes
2
answers
587
views
What is wrong in this argument that dG must always be zero?
Under constant temperature and pressure, the change of the Gibbs free energy can be written as
$$\mathrm dG_\textrm{sys} = \mathrm dH_\mathrm{sys} - T\,\mathrm dS_\mathrm{sys}$$
And in the textbook ...
- 43
39
votes
4
answers
30k
views
Gibbs free energy-minimum or zero?
A reaction proceeds towards the direction of lesser Gibbs free energy (at constant $T$ (temperature) and $P$ (pressure)). So, we could say that Gibbs free energy at equilibrium is minimum.
On the ...
- 15.2k
10
votes
1
answer
26k
views
Derivation of relationship between equilibrium constant and Gibbs free energy change
Why is $\Delta G=\Delta G^o+RT\ln Q?$
It feels like all online sources were written for introductory Chemistry students! Where do I find a rigorous proof of this identity? Greatly appreciate it!
- 1,201
6
votes
2
answers
2k
views
Why does equilibrium exist?
I've read an article that equilibrium exists when $G$ (Gibbs free energy) becomes minimum. If formation of products decreases Gibbs free energy, why won't the reaction proceed to completion so that ...
- 443
6
votes
1
answer
6k
views
Pressure at which graphite and diamond are in equilibrium
The standard state Gibbs free energies of formation of graphite and diamond at $T = \pu{298 K}$ are $\pu{0 kJ mol-1}$ and $\pu{2.9 kJ mol-1}$, respectively.
The conversion of graphite to diamond ...
- 407
16
votes
2
answers
8k
views
Is the Gibbs standard free energy always constant?
I am a biochemistry student and we are learning about thermodynamics. Is the Gibbs standard free energy for a reaction always constant? The equation below suggests that it changes with temperature:
$$...
- 455
4
votes
2
answers
505
views
Equilibrium constant. Can it be reached?
Consider the reaction below:
$$\ce{A + B <=> C}$$
Suppose that the equilibrium constant for this reaction is $K = 10$.
I then prepare a reaction vessel with volume of $\pu{1 dm^{-3}}$ which ...
- 41
10
votes
3
answers
4k
views
What kind of equilibrium constant we use for Gibbs free energy and Van't Hoff equation?
We know that the Gibbs free energy is related to the equilibrium constant by the following equation:
$$\Delta_\mathrm{r}G^\circ=-RT\ln K$$
We also know the Van't Hoff equation:
$$\ln\left(\frac{K_2}{...
- 2,518
6
votes
3
answers
6k
views
How to derive the relation between gibbs energy and equilibrium constant?
I want to understand the derivation between gibbs energy and equillibrium constant $$\Delta G=\Delta G^o+RT\ln Q?$$
I have seen a similar post on CSE Derivation of relationship between equilibrium ...
- 501
4
votes
3
answers
2k
views
If change in free energy (G) is positive, how do those reactions still occur?
I was doing a couple of problems for homework:
Calculate $K_\mathrm{sp}$ of $\ce{AgI}$ at $55.0\ \mathrm{^\circ C}$
Calculate $K_\mathrm{b}$ of $\ce{NH3}$ at $36.0\ \mathrm{^\circ C}$
I have to use ...
14
votes
3
answers
2k
views
Why can't a reaction go to completion?
What is the reason for why an exergonic reaction would still have some remaining reactants (or an endergonic reaction to have any products)? The explanation given on this page (see Chemical reactions ...
- 1,610
6
votes
1
answer
14k
views
Why are Kc and Kp interchangeable in the free energy-equilibrium equation? [duplicate]
In this equation that relates Standard free energy and the equilibrium constant:
$\Delta Gº=-RT \ln K_{eq}$
My textbook (and my teacher) say both $K_p$ (constant related to pressure) and $K_c$ (...
- 275