All Questions
Tagged with free-energy thermodynamics
200
questions
-3
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Gibbs free energy ( condition)
I want to derive Gibbs Free Energy formula from 1st and 2nd law of thermodynamics.
I saw some texts using T and P constant in derivation. I am confused about that. If n,P, T are constant then its ...
-1
votes
1
answer
31
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If the electron affinity for a neutral element is positive (i.e. endothermic process), is the anion more stable than the neutral atom (at STP)?
This might be a bad question, but I have to ask because I'm finding conflicting answers online. Let's say that I have the following reaction: $$O + e^-\rightarrow O^-$$ While I understand that the ...
0
votes
0
answers
51
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Change in Gibbs energy for lithium redox reaction
I was reading an electrochemistry book by Thomas F. Fuller, in this book the thermodynamic values for the lithium redox reaction at standard conditions are the following:
Reaction
$\Delta G^o$ [kJ/...
- 265
4
votes
1
answer
101
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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
3
votes
1
answer
95
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Calculation of Reaction Extent as a Function of Pressure and Temperature: Issue with Activity-Based Approach
I'm working on modeling reactions involving combinations of hydrogen (H), nitrogen (N), and strontium (Sr) elements. I've obtained the temperature-dependent Gibbs free energy of formation, enthalpy, ...
- 31
0
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0
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40
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Confused about free energy equation and entropy change
I'm confused about two equations and how they relate to each other. These are $\Delta S = \Delta Q/T$ and $\Delta G = \Delta H - T\Delta S$.
To derive the Gibbs' free energy change for the universe ...
- 11
0
votes
1
answer
126
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How does cell potential change with temperature for positive enthalpy and negative entropy?
A recent United States National Chemistry Olympiad question asked:
A certain voltaic cell has a standard cell potential that increases with increasing temperature. Which best explains this ...
- 206
0
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3
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110
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Definition of Gibbs Free Energy and its interpretation [closed]
RELATIONSHIP BETWEEN $\Delta G$ & $W_\mathrm{non-PV}$
$dU = dq + dw_\mathrm{py} + dw_\mathrm{non-PV}$
for reversible process at constant T & P
$dU+pdV-TdS = dw_\mathrm{non-PV}$
$dH-TdS = dw_\...
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-2
votes
1
answer
124
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Inconsistency in between Nernst Equation and Gibbs Free Energy Equation [closed]
Part 1 - Derivation of the Gibbs Free Energy Equation: [copied from this]
Using the fundamental equations for the state function (and its natural variables):
\begin{align}
\mathrm{d}G &= -S\...
0
votes
0
answers
53
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Spontaneity of irreversible reactions
I saw this reaction in my textbook:
$\ce{NH4Cl(s) -> NH3(g) + HCl(g)}$ given $\Delta{H}_{r} = \pu{176 kJ/mol}$ and $\Delta{S} = \pu{0.285 kJ/(mol \cdot K)}$
On a worksheet my teacher gave me, I saw ...
- 9
0
votes
1
answer
115
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What is the difference between standard Gibbs energy and Gibbs energy of formation?
Good day guys,
I am reading a book on electrochemical engineering, I came across some definitions of Gibbs energy and I am a bit confused as the book does not go into a lot of detail.
The book first ...
- 265
0
votes
0
answers
46
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Justifying that Standard Entropy of a Reaction is a Constant of Temperature
One of the parts in a question I'm trying to solve for an assignment goes like this:
A key issue in the Hydrogen Economy is Hydrogen Storage. This can be restored if a substance $X$ can bind to $H_2$....
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2
votes
1
answer
166
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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 ...
0
votes
1
answer
161
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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
$$dA = -...
- 281
5
votes
1
answer
387
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Total Differential of Chemical Potential
I have seen many sources (for example this libretext) cite that the total differential of chemical potential is
$$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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