Questions tagged [free-energy]
Also known as Gibbs energy, it is the enthalpy minus the product of thermodynamic temperature and entropy.
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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 ...
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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 ...
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Difference between exothermic and exergonic
In High School I learned that an exothermic reactions releases energy, while an endothermic reaction needs energy to occur. Now I learned that there is a separate, somewhat similar classification ...
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Why does water evaporate spontaneously at room temperature despite ΔG > 0?
Standard Gibbs free energy of formation of liquid water at $\pu{298 K}$ is $\pu{−237.17 kJ mol-1}$ and that of water vapour is $\pu{−228.57 kJ mol-1}$ therefore,
$$\ce{H2O (l) -> H2O (g)}\qquad\...
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Which equilibrium constant is appropriate to use?
I have learnt that the standard free energy change is related to the equilibrium constant of a reaction by,
$$\Delta G^\circ = -RT \ln K$$
Here, does $K$ refer to $K_p$ or $K_c$?
Also, please give ...
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What does "reaction coordinate" mean? What does it mean when a reaction has TWO reaction coordinates?
I'm familiar with the concept of a reaction coordinate from high school chemistry as some generic conformational parameter that all of the intermediate states of a chemical reaction lie upon. Recently,...
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How to treat pressure in computational chemistry?
I have a reaction where a gas at high pressure and a solution with all kinds of species is involved. How do I take pressure correctly into account to get reasonable values for $G$?
Do I calculate ...
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Is the Gibbs standard free energy always constant?
I am a biochemistry student and we are learning about thermodynamics. Is the Gibbs standard free energy for a reaction always constant? The equation below suggests that it changes with temperature:
$$...
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What is the difference between ΔG and ΔrG?
Consider the reaction
$$\ce{A -> B}$$
The reaction Gibbs free energy, $\Delta_\mathrm{r} G$ is given by the following equation
$$\Delta_\mathrm{r} G = \Delta_\mathrm{r} G^\circ + RT \ln Q$$
Now ...
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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 ...
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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 ...
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Transition state and free energy
We have products $\ce{A + B}$ combining to form $\ce{C + D}$ through the transition state $\ce{X}$.
Are all reactions at least virtually reversible? Is the difference between a reversible reaction ...
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How are $\sigma$ and $\sigma^\pm$ determined in Hammett plots?
The Hammett plot is commonly invoked in organic chemistry to reason about the plausibility (or implausibility) of various reaction mechanisms. The vertical axis is essentially the logarithm of an ...
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What is non-expansion work?
I learnt that Gibbs free energy is the maximum amount of non-expansion work.
But the phrase non expansion work confuses me. Work is defined as pressure times change in volume. If there is no expansion,...
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Why is entropy favorable?
I cannot seem to grasp the logic behind it. We say that more entropy (or more disordered system) is favorable over less entropy. But why? Why is randomness preferred over proper arrangement of atoms/...
