All Questions
Tagged with equilibrium free-energy
54
questions
6
votes
3
answers
6k
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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
0
votes
1
answer
451
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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
1
answer
685
views
Why isn't standard Gibbs free energy always zero?
I read in my textbook that one of the standard conditions we should use when calculating the standard Gibbs free energy is having a concentration of 1 M of all the reagents and the products in the ...
1
vote
0
answers
74
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Is chemical equilibrium possible at any temperature and pressure?
Consider the chemical reaction ${\rm Na+Cl\to NaCl}$ by mixing ${\rm Na}$ with ${\rm Cl}$ (or by mixing ${\rm NaOH}$ with some acid). This process is exothermic while the reverse ${\rm NaCl\to Na+Cl}$ ...
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4
votes
2
answers
458
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How come ∆G ≤ 0 is used for spontaneity in electrochemistry, not ∆G ≤ W(other)?
The spontaneity condition for a system at constant temperature and pressure in which the only type of work accomplished is of the $pV$ type can be expressed as:
$$\Delta G\le0\tag1$$
In case of ...
- 41
4
votes
1
answer
137
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Equilibrium and Free Energy
$$\ce{CO2(g) + Ca^2+(aq) + H2O(aq) <=> CaCO3(s) + 2H^+(aq)}$$
Find the equilibrium constant using a free energy table.
Finding the free energy and plugging it into the equation $\mathrm{G = -RT ...
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3
votes
2
answers
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How to calculate Gibbs free energy from pKa?
Is it possible to calculate Gibbs free energy ($ΔG = -RT\ln K_\mathrm{eq}$) of an acid dissociation reaction using the $\mathrm{p}K_\mathrm{a}$? If so, how?
- 41
14
votes
3
answers
2k
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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
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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
2
votes
0
answers
540
views
Active mass,Pressure and concentration
The concentration is connected to the activity via
$$a(\ce{A})= \gamma_{c,\ce{A}}\cdot{}\frac{c(\ce{A})}{c^\circ},$$
where the standard concentration is $c^\circ = 1\:\mathrm{mol/L}$. At reasonable ...
42
votes
3
answers
39k
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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
4
votes
2
answers
505
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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
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
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
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