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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Why 40J energy was wasted in case of a non spontaneous process by the system? [closed]
If there is a system which while undergoing a process produced 30J energy and wasted 40J energy therefore the useful energy was -10J and this explains the process was non spontaneous because ∆G is ...
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Does it make any sense to graph 1/T versus ln(Kc)?
I calculated $K_c$ experimentally for the reaction $$\ce{CO2 + H2O -> H2CO3}$$ at different temperatures. Because $\Delta G =-RT\ln(K)$, I thought that graphing 1/T against $\ln(K_c)$ would give me ...
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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
$$dA = -...
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Total Differential of Chemical Potential
I have seen many sources (for example this libretext) cite that the total differential of chemical potential is
$$d\mu = V_m dP - S_m dT$$
where $V_m$ is the molar volume and $S_m$ is the molar ...
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Why is melting spontaneous when the liquid phase is less stable and should have more free energy than the solid phase?
Imagine a 1kg block of ice that has completely melted at room temperature. If melting is a spontaneous reaction, then wouldn't that mean the products (1kg of water) would have less Gibbs free energy ...
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What meaning does Gibbs energy acquire when applied to solutions?
I have been picturing functions like enthalpy and Gibbs free energy as mathematical tools, which were defined in such a way as to be useful for some specific cases. I understood enthalpy as a useful ...
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Understanding the Role of Gibbs Free energy and Enthalpy as the energy required to drive a reaction
I was looking at the enthalpy change for water-splitting reaction:
$$ \Delta H^o_R = [\Delta H^0_{H_2(g)} +\frac{1}{2}\Delta H^0_{O_2(g)}]-\Delta H^0_{H_2O(l)} = \pu{285.83 kJ/mol}$$
According to ...
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Finding ΔH and ΔS given Gibbs free energy at two temperatures
Question: Gibbs free energy of a reaction at $\ce{300 K}$ and $\pu{310 K}$ are $\pu{-28 kcal}$ and $\pu{–28.5 kcal}$
respectively. Determine $\Delta H$ and $\Delta S$ at $\pu{300 K}$.
I tried ...
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Gibbs free energy versus reaction progress plots
I am trying to make sense of these two graphs. They appear to have similar axes, yet display different curves.
Please let me know if this understanding is correct:
In the top image (x-axis = "...
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Chemical Equilibrium and Sponteneity
Consider the reaction $$\ce{N2O4 <=> 2 NO2}.$$ The forward direction of this reaction is non-spontaneous and under standard conditions $\Delta G^\circ = \pu{4.76 kJ/mol}$. Suppose we begin with $...
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Enthalpy of adsorption and adsorption rate
What I want to know is about the adsorption enthalpy change by the change of surface coverage and the adsorption rate. In general situations, adsorption would be exothermic. So in the Gibbs free ...
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Is the change ΔG for an ideal gas unknown?
When one is introduced to the first law of thermodynamics, one learns that enthalpy is only a function of temperature, and calculating its changes is straightforward
\begin{equation}
\Delta H^\pu{...
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Can ΔG = ΔG° + RT ln Q be used to calculate K at different temperatures?
Specifically, can $\Delta G=\Delta G^{\circ}+RT \ln Q$ be used to calculate reaction quotients if we choose T to be a different temperature than the one provided by ΔG°?
For example, suppose that we ...
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Why would there be a non-zero Gibbs energy of mixing for ideal gases?
When two ideal gases $\ce{A}$ and $\ce{B}$ mix, they don't interact. The chemical potential of each gas is independent of the other, e.g. for $\ce{A}$:
$$\mu_\ce{A} = \mu_\ce{A}^\circ + R T \ln \frac{...
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∆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 ...
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