New answers tagged thermodynamics
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Entropy change during electrolysis of water
The answers to all your questions can be provided by using the open-system (control volume) version of the 1st and 2nd laws of thermodynamics to analyze a specific continuous flow system featuring ...
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Can free energy of a spontaneous reaction be positive?
The notion that a reaction is spontaneous if $\Delta G^0$ is < 0 is only a rule of thumb, and all it indicates that for a totally gas phase reaction, the equilibrium constant is <1. If there ...
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Can free energy of a spontaneous reaction be positive?
At the moment I am writing this, the question has $26$ edits and $19$ links to other pages. This is getting out of control, so I am answering to edit number $26$. My approach will be the following: I ...
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Effect of pressure on the vapour pressure of a liquid
They have provided a qualitative analysis as to why the vapour pressure changes with external pressure, however according to the coexistence curve, there should be a fixed vapour pressure at a fixed ...
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Effect of pressure on the vapour pressure of a liquid
They are talking about a pure liquid and and a gas composed of two or more chemical components, one of which the same vapor as the pure liquid and the rest of which are non-condensible. So the total ...
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2
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Can free energy of a spontaneous reaction be positive?
I've tried to summarise some points made in the comments and in the question's title.
The word 'spontaneous' is perhaps an unfortunate one when chemical reactions are involved. In a process such as ...
- 28.7k
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Can free energy of a spontaneous reaction be positive?
Decomposition temperature can have the standard reaction Gibbs energy still positive, if nonstandard one is already negative.
Thermal decomposition of solids to products partly gaseous (in context of ...
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Schottky Anomaly
To answer 'But I don't understand how a system with finite states can have a temperature', we can start with the thermodynamic definition of temperature as
$$\displaystyle T=\left(\frac{\partial U}{\...
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Schottky Anomaly
I understand temperature as the average translational kinetic energy
per particle.
Temperature isn't just related to the kinetic energy of particles, it also changes the potential energy. The ...
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9
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Why would there be a non-zero Gibbs energy of mixing for ideal gases?
With your reply you seem to have answered part of your question. I would like to add a bit about the other part. I will have to do it mathematically first, there is no other shortcut, but then we will ...
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Why would there be a non-zero Gibbs energy of mixing for ideal gases?
When we talk about mixing, we usually mean that two components are in different parts of a container before mixing and then they share the entire container after mixing. In other words, the total ...
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Why is the voltage produced by a voltaic cell affected by temperature as described by the Nernst Equation?
Both terms of the difference in the Nernst equation depend on the temperature.
$$E = E^\circ - \frac{R T}{z F} \ln Q$$
The second term obviously depends on temperature because it contains the ...
- 36.4k
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Why is the voltage produced by a voltaic cell affected by temperature as described by the Nernst Equation?
You are correct in understanding that changing the concentration of electrolytes in a voltaic cell affects the voltage through the Nernst equation. As for the effect of temperature, it is important to ...
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What is the basis for the relationship of Gibbs energy and extent of reaction shown in this graph?
The Gibbs energy for a system at a fixed pressure and temperature, is only a function of the concentration of the species. We write it in a differental form
$$ dG = \sum_j \mu_j dn_j \tag{1} $$
Our ...
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7
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What is the basis for the relationship of Gibbs energy and extent of reaction shown in this graph?
UPDATE: In the comments to this and other answers, the question came up why the Gibbs energy of mixing is related to chemical reactions. In a chemical reaction, reactant turns into product (or vice ...
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8
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What is the basis for the relationship of Gibbs energy and extent of reaction shown in this graph?
What an interesting question! I was perplexed when I first read this. And then I remembered what my professor told me in college, that is, "when in doubt, read." So, I read and found an ...
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Validly of the equation, du= nCv dt, for an adiabatic process
Consider a closed system for which $\mathrm{d}n=0$.
Then, the definition of $C_v$ is given by $\left(\dfrac{\partial U}{\partial T}\right)_V$.
$C_v$ is an intrinsic property of any material and it ...
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Accepted
Why aren't Gibbs energies additive in the serial reduction of cupric ion?
I had actually misplaced a decimal point and, upon correcting for the accurate values, the discrepancy was resolved.
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How can entropy of universe or surroundings be a state function?
A State Function has a value for a given state of a system. This means that if something undergoes a process and eventually returns to the exact same conditions as it started, its state functions U, G,...
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Accepted
How can entropy of universe or surroundings be a state function?
TL;DR: entropy, for reversible and irreversible processes, for system, surroundings and universe, is always a state function. You are not accurately considering the initial and final states of ...
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How can entropy of universe or surroundings be a state function?
There is no reversible route from A to B if those are the states of the universe.
If A and B are system states, and you take different paths, the surrounding state will be distinct for distinct paths. ...
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