Questions tagged [entropy]

For questions about the thermodynamical state function entropy, commonly understood as a measure of disorder.

Filter by
Sorted by
Tagged with
1
vote
0answers
18 views

Entropy between elements and compounds

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 ...
2
votes
3answers
64 views

Does the entropy of a chemical system increase in an endothermic reaction?

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 ...
-1
votes
1answer
65 views

Ordered and random energy

One of the books refer to potential energy being ordered whereas heat energy being random. Could someone explain what is ordered and random energy?
0
votes
0answers
30 views

Entropy and Gibbs Free Energy of Chelate Complexes

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 ...
2
votes
0answers
33 views

Is it possible to measure the entropy of a chemical reaction through calorimetry?

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 ...
0
votes
1answer
44 views

Entropy problem [closed]

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. ...
4
votes
1answer
34 views

What is the trend in hydration entropy of alkali metal ions?

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$^...
-1
votes
1answer
42 views

why is entropy maximum at equilibrium for a closed system? [closed]

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 ...
3
votes
2answers
42 views

Isobaric entropy relation from isothermal Gibbs free energy relation

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}\...
2
votes
0answers
41 views

Entropy of free expansion and isothermal process

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 ...
0
votes
2answers
124 views

Total entropy change for a spontaneous reaction

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 ...
3
votes
2answers
55 views

How can change in entropy be the same for all processes if the entropy production $\sigma$ is present for irreversible processes?

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 ...
3
votes
1answer
48 views

Derivation and visualization of cell potential dependency on temperature and entropy

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 ...
1
vote
1answer
35 views

Entropy of Dissolution of Hydrocarbons

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 ...
2
votes
0answers
71 views

How to find the equilibrium constant under non-standard conditions?

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{...
3
votes
2answers
176 views

Change in enthalpy and entropy when sugar dissolves in water

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 ...
1
vote
1answer
82 views

Entropy change during irreversible process

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 ...
7
votes
0answers
73 views

Why does entropy increase in reactions that make more molecules?

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....
0
votes
1answer
47 views

How to calculate ∆rGº from entropy and ∆fGº in different temperatures? [closed]

"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 ...
-1
votes
1answer
46 views

Change of entropy of a thermal reservoir [closed]

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 $$ S(U)? $$
3
votes
0answers
92 views

(Probabilistic) entropy associated with many equally probable microstates

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, ...
2
votes
0answers
58 views

Why does the plot of volume and temperature have a kink in a second order phase transition?

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 ...
3
votes
0answers
31 views

Total Entropy of the Atkinson Cycle

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 (...
2
votes
1answer
45 views

What is the mechanism of endothermic dissolution?

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 ...
1
vote
0answers
26 views

What is the fundamental difference between temperature and energy? [duplicate]

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 ...
1
vote
0answers
68 views

Entropy of a van der Waals' gas

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. ...
0
votes
0answers
34 views

Question about reading NIST datasheets & Gibbs energy of reaction

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 ...
1
vote
1answer
76 views

Helmholtz Free Energy Minimization Proof

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 ...
-2
votes
1answer
50 views

conceptual doubt on change in entropy [closed]

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 ...
2
votes
3answers
187 views

entropy calculation in an irreversible process

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 ...
8
votes
1answer
204 views

My Misconception of Entropy

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 ...
0
votes
2answers
77 views

How can you calculate the tendency of one compound to become another?

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 ...
2
votes
1answer
447 views

entropy of vaporization vs entropy of fusion

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 ...
1
vote
1answer
445 views

Adiabatic expansion of gas

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: ...
0
votes
2answers
73 views

Thermal equilibrium in reversible processes

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}=...
0
votes
1answer
53 views

Extrema in free energy of a solution?

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 ...
6
votes
2answers
412 views

Why is the molar entropy of hexane lower than that of butane?

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 ...
-1
votes
1answer
108 views

Feasibility of a Reaction [closed]

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 ...
0
votes
1answer
108 views

Sign of change in enthalpy and change in entropy

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 ...
1
vote
1answer
193 views

Entropy increase of both system and surroundings [closed]

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 ...
4
votes
1answer
518 views

Why does spontaneity of a reaction depend on temperature?

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 $\...
-1
votes
1answer
53 views

Change in Entropy and Spontaneity [closed]

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 ...
1
vote
1answer
86 views

Apparent paradox regarding spontaneity

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}=...
0
votes
0answers
40 views

How to find entropy of chemical network reaction?

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 &<=&...
0
votes
1answer
124 views

Is entropy of surroundings a state function?

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 ...
3
votes
1answer
116 views

What's the minimum amount of energy needed to remove CO2 from the atmosphere?

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 ...
3
votes
1answer
124 views

How does the entropic force arise within the hydrophobic effect?

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 ...
4
votes
0answers
55 views

Is entropy maximum in equilibrium?

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 ...
1
vote
1answer
79 views

A Curious (definitely wrong) result of Absolute Entropy [closed]

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, $...
0
votes
0answers
182 views

Why doesn't Delta S total = 0 for this reversible process?

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 ...

1
2 3 4 5 6