For questions about the thermodynamical state function entropy, commonly understood as a measure of disorder.
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Why HF hydrogen bond become stronger in gas phase than liquid phase?
I found that deltaS_vap of HF(similar as the ratio of the molar heat of vaporization of a liquid to its boiling point) is smaller than 90J/K*mol which came from Trouton's rule.
Molecule with hydrogen ...
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0answers
25 views
Thermodynamics - linking Gibbs free energy, enthalpy and entropy [closed]
I wanted to write an expression for the entropy change of a reaction
Would I use ΔG = ΔH - TΔS OR ΔS = - ΔH/T I don't get the reason for these two different equations. Is the later for ...
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0answers
25 views
How to calculate relations among thermodynamic quantities
I'm trying to learn how to calculate the many relations that exist in thermodynamic. Like for example
$$ \left(\frac{\partial U}{\partial S}\right)_V $$ or $$ \left(\frac{\partial S}{\partial T}\...
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1answer
31 views
In chemistry what do they mean by disorder when in the context of entropy?
Entropy is often the amount of disorder is present in a system, but when they refer it to the degree of disorder in a system what do they mean. It just seems the term is quite vague and not very ...
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2answers
62 views
Why does ATP has a lower entropy than ADP
I was confused about why ATP has a lower entropy than ADP when ATP has 1 more phosphate group. According to https://chem.libretexts.org/Textbook_Maps/Biological_Chemistry/Metabolism/ATP%2F%2FADP#...
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1answer
31 views
An equal amount of hydrogen gas is dissolved in a 1L vessel and a 2L vessel, both filled with water. Which vessel has higher entropy? [closed]
This question came up in our chemistry class and we could not determine which would have the higher entropy. Clearly, Vessel 2 has a larger volume, but Vessel 1 has a higher concentration of $H_2$. ...
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0answers
29 views
Molar entropy of vaporization
If a substance has a molar heat of vaporization of $\pu{3.05\times10^4J/mol}$ and a normal boiling temperature of $\pu{80.0^\circ C}$, what is the value of its molar entropy of vaporization $\Delta S_\...
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0answers
45 views
Why don't these Entropy equations contradict each other?
My textbook says that $\delta S_{rev}= \frac{q_{rev}}{T}$. It also says that $\delta S_{surr}= \frac{-q_{rev}}{T}$. Logically, this should mean that the change in entropy in both the surroundings and ...
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2answers
113 views
Absolute entropy
The third law of thermodynamics states that the absolute entropy of a pure crystalline substance is $0$ at $0\,\mathrm{K}$. In the analysis of chemical reactions this absolute scale is sued to ...
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1answer
28 views
Reaction direction change based on phase of reactants and products
I am curious specifically how the entropy of a reaction will change if the phases of the reactants and products at different conditions change.
For instance, a reaction
$$\ce{O2(g) + C(s) -> CO2(...
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1answer
43 views
Where can I find the standard molar entropy for ammonium bicarbonate?
I'd like to know the standard molar entropy S0solid for ammonium bicarbonate to use in an example in class, to calculate ΔS0 for the reaction, NH4HCO3(s) → NH3(g) + H2O(g) + CO2(g).
Already checked: ...
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1answer
52 views
Entropy change of evaporating NaCl [closed]
What is $\Delta S$ for this process?
$$\ce{NaCl(s) -> NaCl(g)}$$
(A reference that I could quote would be ideal.)
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1answer
79 views
What exactly is entropy? [closed]
I have looked at other questions, videos and articles but I kept reading disorganization, messiness or energy distribution (probability) or a thermodynamical equilibrium and stuff. What do we mean by ...
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1answer
96 views
Energy at constant Entropy and Volume
The system of constant entropy and constant volume will attain the equilibrium in a state of minimum energy. Why?
I know that:
$\Delta G= \Delta H-T\Delta S$
And at constant volume and entropy: $\...
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0answers
49 views
How to compare standard entropy of diatomic gases?
Say, for example, I wanted to compare the standard entropies of $\ce{Cl2(g)}$ and $\ce{F2(g)}$. They both are equimolar.
I understand that entropy is a measure of how many states a particle can ...
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1answer
202 views
The confusion of entropy change
The entropy is defined as randomness of a substance or a system.
The randomness increases as we go from solids to liquids to gases. Similarly from hard diamond to soft graphite. Since graphite is soft ...
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2answers
502 views
Is it possible to determine the absolute value of entropy of a system?
I came across a question (in some assignments I had received) where it was asked:
Can the absolute value of entropy of a system can be measured?
and to my surprise, the answer said yes. Till now, ...
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2answers
97 views
Can the change in the entropy of the surroundings always be obtained by dividing heat transferred by the temperature at which the transfer occurs?
Consider $\pu{1 mol}$ of an ideal monoatomic gas going through reversible isochoric heating from $\pu{100 K}$ to $\pu{1000 K}$.
Calculate $\Delta S_\pu{sys}, \Delta S_\pu{surr}.$
$$\Delta S_\pu{...
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2answers
377 views
Entropy is a measure of unavailable energy?
I came across a statement in my text book which said that entropy is a measure of unavailable energy.
What does this statement signify?
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1answer
44 views
How does the mathematical definition of entropy (ΔS=Qrev/T) give us the degree of disorder? [closed]
I think degree of disorder in thermodynamics means the number of possible locations that a molecule can take
How does the mathematical equation signify this?
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0answers
39 views
Are volcanic eruptions a form of entropy? [closed]
My understanding of entropy is 'order to disorder' so I was thinking whether volcanic eruptions are a form of entropy since when magma leaves the crater it becomes lava. Is it more favourable for this ...
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0answers
76 views
dq/T vs. CdT/T for measuring absolute entropy
In principal one could determine absolute entropy for a substance by integrating dq/T from 0K to the temperature of interest. However, I've seen this done using heat capacities, integrating CdT/T ...
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0answers
51 views
Change in Free Energy in Gas Reaction
I try to estimate whether particles form pairs or not.
What I know is the difference in the potential Energy $\Delta U_\mathrm{pot}$ which occurs when both particles form a pair.
When I have a ...
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4answers
4k views
Why is entropy favorable?
I cannot seem to grasp the logic behind it. We say that more entropy (or more disordered system) is favorable over less entropy. But why? Why is randomness preferred over proper arrangement of atoms/...
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0answers
22 views
Entropy and heat capacity [duplicate]
I’ve seen the entropy change for the surrounding in an exothermic reaction given as simply:
∆H/T
However, entropy change depends on heat capacity and ∆H/T doesn’t take that into account.
Wouldn’t the ...
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1answer
468 views
Does increasing the entropy of a system cause it to absorb heat?
This is my first time posting here, so bear with me. It was stated (in this video: https://youtu.be/7jT5rbE69ho?t=325) (Watch about the next fifteen seconds, until 5:40) that an increase in entropy ...
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1answer
100 views
Change of temperature upon dilution
Consider a concentrated dye solution, say 10µM of Rhodamine 6G in water, which is rapidly diluted down to 10nM in an open container. I'm trying to estimate the (presumably minute) temperature change, ...
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1answer
56 views
Does a polyethene shrinking signify negative or positive entropy?
When I think of something shrinking, I would intuitively think it decreases in entropy as there is less movement. E.g. if a gas was to reduce in volume, there would be less movement of the particles ...
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1answer
521 views
Why does the Second Law of Thermodynamics hold true?
The Second Law of Thermodynamics states that the state of entropy of
the entire universe, as an isolated system, will always increase over
time. The second law also states that the changes in the ...
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1answer
74 views
Entropy at zero kelvin for pure atom crystal
The third law of thermodynamics describes that the entropy of pure ideal crystaline substance is zero.
Now we know that in practice this could be wrong for water (for example) because of its ...
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1answer
78 views
Understanding entropy / spontaneity
I have issues understanding the spontaneity for these processes:
Which of the following processes are spontaneous:
(c) alignment of iron filings in a magnetic field;
(d) the reaction of sodium ...
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1answer
68 views
Biomolecular energy functions and entropy
From what I've been reading, it seems that entropy (rather than enthalpy) is the biggest driver of protein folding (especially the burying of hydrophobic residues). However, popular energy functions ...
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1answer
61 views
Notation for specific/volumetric entropy
I'm working on a problem related to entropy, and for this particular use case it's advantageous to write down properties in 'specific' units. In the case of entropy (with units Joules over Kelvin, I ...
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0answers
91 views
Change in entropy of surroundings
One mole of an ideal gas at $\pu{300 K}$ in thermal contact with surroundings expands isothermally from $\pu{1.0 L}$ to $\pu{2.0 L}$ against a constant pressure of $\pu{3 atm}$. What is the change in ...
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1answer
319 views
Entropy and enthalpy at the melting point of benzene
For the melting of Benzene, since it is melting, it feels intuitive to think that the change in entropy will be positive (more disorder) and enthalpy will be positive (exothermic). However, when I ...
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0answers
107 views
Change in enthalpy and entropy for the formation of nickel tetracarbonyl
I was working on an enthalpy/entropy problem and I had a question on predicting the signs of some reactions. For the reaction
$$\ce{Ni (s) + 4 CO (g) -> Ni(CO)4 (g)}$$
my textbooks says that ...
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0answers
77 views
A question about entropy changes
Is the total entropy change of the forward direction of a particular reaction equal to the total entropy change of the backwards direction of the same reaction ?
Just a thought...
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1answer
322 views
Why can we use standard entropy when determining temperature at which a reaction becomes spontaneous?
In this chemistry problem, $\Delta H$ and $\Delta S$ are given at $298\text{ K}$, and it asks for the temperature at which the reaction becomes spontaneous:
For the reaction $2\text{SO}_3 \...
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1answer
654 views
Adiabatic mixing of liquids
One mole of benzene at $\pu{20^\circ C}$ is adiabatically mixed with 2 moles of toluene at $\pu{40^\circ C}$. The heat capacity of benzene is $\pu{84 J K-1 mol-1}$ and the heat capacity of toluene is $...
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2answers
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Why does like dissolve like?
Polar solvents love polar solutes to be dissolved in it and non polar with non polar. Often said as like dissolves like.
Okay, polar loving polar can be understood with help of the facts: same polar ...
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2answers
199 views
Why is “Spontaneous” a part of 2nd law wording?
The way I understand the law, any process is implausible if the total entropy of the universe does not increase. Why is "Spontaneous" even a part of the wording, what does it mean?
Is it perhaps a ...
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1answer
1k views
Calculation of irreversible surrounding entropy
I have a specific query. In my undergraduate book Physical chemistry by Engel and Reid, sample problem 5.8 calculates the change in entropy of the surroundings and system for an irreversible ...
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0answers
54 views
Micelle formation [duplicate]
When micelles are formed... The movement of the molecules gets restricted so shouldn't it result in a decrease in entropy?
But it is said that increase in entropy is the driving force behind micelle ...
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2answers
1k views
Does deuterated water slow down the overall metabolism of a cell?
Would deuterated water, being heavier, slow down the metabolic rate of the cell and subsequently the aging process?
edit: lets say I wanted to observe a cellular event, like the formation of the ...
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1answer
421 views
Is protein folding thermodynamically favourable? If yes.. why? [duplicate]
The second law of thermodynamics dictates that the sum of entropy of the universe is always increasing. Is the process of protein folding a spontaneous process which is increasing the entropy? Is this ...
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0answers
400 views
Entropy of Activation and Temperature Dependence
I am trying to understand the extrapolation of enthalpy $\Delta H^{\ddagger}$ and entropy of activation $\Delta S^{\ddagger}$ from the Eyring equation. It's typically cast as: $$ln(k/T) = -\Delta H^{\...
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3answers
553 views
Why does the reaction between Na (s) and Cl2 (g) occur spontaneously if the entropy of the system decreases?
1- The reaction is exothermic.
2- My book says that it is because the total entropy change is very positive.
Here is my book's explanation and it is the highlighted part which i dont understand :
"...
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1answer
290 views
Can the idea of entropy be extended to orbitals?
The forward reaction for: $\ce{HF<->H^+ +F^-}$ is entropically favourable; but energetically unfavorable: as there is too much electron density for $\ce{F^-}$ ion to cope up. That's a reason why ...
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1answer
345 views
Why does increasing the temperature of a *solid* increase its entropy?
I understand why increasing the temperature of a fluid would increase its entropy, as the particles are free to move, and therefore an increase in kinetic energy would allow the particles to move more,...
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0answers
1k views
Why increase in enthalpy leads to increase in entropy? [closed]
Given statement: Enthalpy of adsorption is the strength at which molecule (say $\ce{H2}$) is bound to the adsorbent (say some metal center). For a free $\ce{H2}$ molecule, the entropy contribution is ...
