Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
I have encountered this reaction when I am learning entropy:
I don't understand why there is an increase in entropy (said to be slightly larger than 0).
What I am thinking is:
both reactants and ...
Since entropy increases when temperature increases, the entropy of surroundings increases during an exothermic reaction. When I apply the same logic, it seems like the entropy of a chemical system ...
Of [Cd(NH2CH3)4]2+ and [Cd(en)2]2+ the stability of the latter is higher than the former attributing to chelation in the en complex .This is evident from the fact that the Gibbs Free Energy change for ...
My broad question is how do you measure entropy change? I was doing a bit of digging into how thermodynamic tables are developed at I got this from NIST. Basically it seems like you need to indirectly ...
A tank is divided into two equal chambers by an internal diaphragm. One chamber contains methane at a pressure of $\pu{500 bar}$ and a temperature of $\pu{20 °C},$ and the other chamber is evacuated. ...
Is there a trend in alkali metal ion hydration entropy?
There's much talk of hydration enthalpy, but I have a hard time finding information about the change in entropy.
Am I right in thinking that Li$^...
I don't understand why entropy is maximum at equilibrium for a closed system:(
I tried understanding some of the answers her on chemistry StackExchange but they involved the use of probabilistic ...
I have been given a problem to derive a relation for change in entropy from change in Gibbs free energy:
Starting with the isothermal equation
$$G(p_2) = G(p_1) + nRT\ln\frac{p_2}{p_1}\label{eqn:1}\...
Let me tell what I understand of the concepts on which the question is based first.
Heat is a flow of energy that takes place due to a temperature gradient.
When doing reversible isothermal expansion ...
For the oxidation of iron,
$$\ce{4 Fe(s) + 3 H2O(g) -> 2 Fe2O3(s) + 3 H2(g)}$$
the entropy change is $ \pu{–549.4 J K^{-1} mol^{-1}}$ at $\pu{298 K}.$ In spite of the negative entropy change of ...
From the definition of entropy change,
$$S_2-S_1=\left ( \int_{1}^{2} \frac{\delta Q}{T}\right )_{int.rev}$$
From the closed system entropy balance, we have
$$S_2-S_1=\left ( \int_{1}^{2} \frac{\delta ...
Working from the thermodynamic identity
$$\Delta{S} = -\left(\frac{\partial{\Delta{G}}}{\partial{T}}\right)_p,$$
is it allowed to integrate both sides to obtain an expression derived from the Nernst ...
Here is what I think I know: The entropy of dissolution reactions increases as methylene groups are added (i.e. butanol has higher entropy of dissolution than propanol). Also, acyclic saturated ...
Given the following thermodynamic data at $\pu{298 K}:$
$$
\begin{array}{lrrr}
\hline
\text{Compound} & \Delta_\mathrm{f}H^\circ/\pu{kJ mol^-1} & S^\circ/\pu{J K^-1 mol^-1} & C_p^\circ/\pu{...
We know that dissolution of sugar in water is a spontaneous process.
So, change in Gibbs free energy $(ΔG)$ must be negative for the overall process:
$$ΔG = ΔH - TΔS < 0$$
Hence either the enthalpy ...
Entropy change is defined as $\Delta S = \int \frac{\delta Q_{rev}}{T} $, where $Q_{rev}$ is heat transferred through a reversible process. I’m a little confused how this works, so I have a couple of ...
I used to understand this (more molecules ⇒ more degrees of freedom), but do no longer, because the total number of atoms is conserved, so translational d.o.f. should just be turned into internal d.o....
"The total oxidation of glucose occurs according to the following chemical equation:
C6H12O6 (s) + 6O2 (g) -> 6CO2 (g) + 6H2O (l)
The following table gives us the free energies of standard ...
How to calculate/derive the change in entropy of a heat reservoir as function of its internal energy? If the constant temperature of heat reservoir is T, and
$$ S(U_0)=S_0,$$
what is $$ S(U)? $$
This is a pretty naive question. The probabilistic definition of entropy is (for a mole of particles)
$$-R\sum_i p_i\ln p_i $$ in which $p_i$ is the probability of a given microstate and $\sum p_i =1, ...
The $(b)$ part of the figure shows how thermodynamic variables change in a second order phase transformation.
We observe there is a kink in the plot of volume with temperature.
Why is that so?
The ...
I was researching for a question that asked me to find a ratio of temperatures, and I came across this, which would help me greatly:
Since, most of the temperature changes occur during the isochoric (...
My real question is in fact "How can dissolution happen if it's endothermic?" However, there
have been many questions regarding this exact topic and the answers about Gibbs free energy
...
We know that temperature is proportional to the average kinetic energy of a system. We also know that temperature is not the same as energy because the temperature is intensive while the temperature ...
I would like to ask how I could derive the entropy change $dS$ for a van der Waals' gas.
I think I would need to use the total differential of entropy and then use the Maxwell relation shown below.
...
I'm peeping the NIST thermo tables for $\text{H}$ and $\text{H}_2$, and I'm perplexed.
Seems to me that using
$$G=[\Delta H^\circ_f+H-H^\circ(T_r)]-T\cdot S^\circ$$
(well, actually correcting the ...
In the proof that Helmholtz free energy is minimized at equilibrium, we use the fact that $$\mathrm dS_\text{total}=\mathrm dS_\text{system}+\mathrm dS_\text{bath}\geq 0$$
But we also use the fact ...
we have learnt in thermo that delta S is zero in reversible process
Now, when a solid melts reversibly is delta s zero since reversible or positive since the particles are more energetic in liquid ...
I found out that if we want to find the entropy change in an irreversible process let's say $\text{state A} \to \text{state B}$ , we find or make an reversible path for the same process and find the ...
It was recently brought to my attention that my understanding of entropy is wonky at best.
In my experience, entropy was introduced (superficially at best) during general chemistry/foundations of ...
Excuse my inexperience with chemistry here. I've been poring over papers with terms like "Standard Gibbs free energy of formation", "Hess's Law", "standard enthalpy of ...
Is the entropy of vaporization greater than entropy of fusion, for elements? And in which case they can be same, if it so happens?
I have asked this here because I couldn't find any satisfactory ...
If a real gas is adiabatically expanded against constant pressure, then which of the following will definitely increase?
Compressibility factor (Z) or Entropy (S)
Correct answer: Entropy
My answer: ...
In whatever resources I have consulted to study reversible thermodynamic processes, a common statement seems to be :
The system and surroundings (if the boundary allows) are in mechanical ($P_{sys}=...
I am a high school student reading about the second law of thermodynamics, and one of the equations given was the free energy change in dilution.
$$\Delta G_{\text{dil}} = -RT \log(C_1/C_2)$$
This ...
Entropy is dependent on the complexity of the molecule.
Due to this, I expected entropy to increase as the complexity of the molecule increased.
According to p 918 of Atkins' Physical Chemistry (9th ...
I understand for a reaction to be feasible, $\Delta$H needs to be negative and $\Delta$S positive. But in terms of Gibbs free Energy Change, without considering kinectic factors, If $\Delta$H is ...
Why is it wrong to assert that the change in entropy and the change in enthalpy must always have the same sign?
What makes me think that they must have the same sign is the fact that every reaction ...
In "why chemical reactions happen" the author (James Keeler) says that "a process which leads to an increase in the entropy of the system can be ... exothermic." Could someone ...
As we know, $$\Delta G=\Delta H - T\,\Delta S.$$
Both in my textbook and on the internet, it was given that temperature was a determining factor in the spontaneity of a reaction. For example, when $\...
I was studying thermodynamics and got stuck with some questions. I am pointing them down.
I have studied that $\Delta S_{\text{total}}$
accompanied by a spontaneous process is greater than 0. But is ...
Consider the following analysis ( rev and irrev respectively refer to a reversible and an irreversible path, between the same initial and final states):
$dU_{rev}=dq_{rev}+dw_{rev}$,and,$dU_{irrev}=...
I have the following system of reactions:
$$
\begin{aligned}
\ce{X_1 + Y_1 &<=>[$k_{21}$][$k_{12}$] X_2} \\
\ce{X_2 &<=>[$k_{32}$][$k_{23}$] X_3} \\
\ce{X_3 &<=&...
It is a pretty common well known fact that the entropy of a system is a state function ie. it doesn't depend upon the path taken by the process as long as the initial and final states are the same.
I ...
I've been learning about CDR (Carbon Dioxide Removal) techniques to combat climate change. These all seem to involve extracting $\ce{CO2}$ from the atmosphere and converting to a mineral, which is ...
I know that the hydrophobic effect is usually explained by the entropic effect originating from the disruption of hydrogen bonds between molecules of water and the nonpolar substance. The hydrogen ...
Usually, in the context of non-equilibrium thermodynamics, it is said that entropy achieves a maximum in equilibrium, so the Taylor series expansion of entropy around the equilibrium state as a ...
The Gibbs free energy is defined as
$$G=H-TS$$
Differentiating both sides
$$dG=dH-TdS-SdT$$
For an adiabatic reversible expansion of an ideal gas, we would have $dG=0$, and $dS=0$.
Thus we can write, $...
My textbook (Engel Physical Chemistry 3rd Edition) says:
For any irreversible process in an isolated system, there is a unique direction of spontaneous change: $\Delta S > 0$ for the spontaneous ...
By clicking “Accept all cookies”, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy.