All Questions
Tagged with equilibrium free-energy
54
questions
3
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1
answer
95
views
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
votes
1
answer
121
views
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
-2
votes
1
answer
122
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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\...
2
votes
1
answer
163
views
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
474
views
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 = "...
- 11
-2
votes
1
answer
165
views
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 $...
- 281
1
vote
1
answer
199
views
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 ...
- 111
0
votes
1
answer
74
views
Why does the reaction of dissolution stop at an equilibrium point? [closed]
The formula for Gibbs free energy is $\Delta G=\Delta H-T\Delta S$.
If Gibbs free energy is negative, the reaction is spontaneous. This also applies to dissolution reactions.
However, we know that ...
- 19
3
votes
1
answer
1k
views
Is the entropy change positive or negative in this reaction?
Suppose I have a reversible reaction
\begin{align}
\ce{A(g) + B(g) <=> C(g)}\\
\end{align}
with equilibrium constant K.
Its ΔΗ is positive throughout.
Now, suppose I start with 1 mole ...
0
votes
1
answer
897
views
Standard Gibbs free energy when all the reactants and products are at standard condition
I have read in my textbook that for a reaction $\Delta G=\Delta G^o-RT\ln Q $, where $\Delta G^o$ is the Gibbs free energy change when the initial concentration of products and reactants are unity. ...
- 159
0
votes
0
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75
views
How to find the temperature for when Kc = 1
The formulas I can use are $\Delta$G = H - T$\Delta$S, and $\Delta$G = $\Delta$G(s.t.d) + RTlnK
I understand that when Kc is 1, the reaction is barely spontaneous and thus I can use the first formula ...
0
votes
0
answers
41
views
At equilibrium, which one of the following is always Zero? [duplicate]
At equilibrium, which one of the following is always zero?
(A)∆H
(B)∆S(Total)
(C)∆S(System)
(D)∆G°
I know that at equilibrium ∆G=0, and was facing difficulty in connecting the above mentioned ...
0
votes
0
answers
62
views
Equilibrium and endergonic reaction
If a reaction A <-> B has a value of dG°>0, then I know that A -> B is endergonic while A <- B is exergonic.
Now if I start with 100% B I could see how equilibrium is reached, B reacts ...
- 1
-1
votes
1
answer
337
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Cause of reversible reactions in terms of Gibbs free energy
Heading
I recently learned about the standard Gibbs free energy change of reaction, ΔG=ΔH-TΔS, and how its sign indicates whether the conversion of (ALL) reactants and products is spontaneous or not.
...
- 551
0
votes
1
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135
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How is the change in Gibb's free energy a condition for spontaneity for reactions not happening under constant pressure conditions?
According to what I have studied, the change in Gibb's free energy is only a condition for spontaneity for processes happening at constant pressure and temperature conditions.
Consider a reversible ...
