Questions tagged [entropy]
For questions about the thermodynamical state function entropy, commonly understood as a measure of disorder.
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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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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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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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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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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\left(\frac{k}{T}\...
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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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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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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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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 ...
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Entropy and specific heat capacity
I have seen the equation $S(T_2)=S(T_1)+C_p\ln(T_2/T_1)$ where $C_p$ is the molar heat capacity at a constant pressure. I understand that this assumes that the temperature range is sufficiently small ...
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Precise explanation of macrocyclic effect
In most of the books, the reason of macrocyclic effect is given that It occurs due to preorganised structure of macro-cyclic ligand.
But a proper explanation of these two particular examples isn't ...
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Na(s) vs NaCl(s) Entropy
I would think the crystalline, ionic solid would have the lower entropy, however, the tablature indicates otherwise. Why does $\ce{NaCl(s)}$ have a greater entropy than $\ce{Na(s)}$?
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Negative temperature as limiting case for two-level system
For N particles in a two-energy-level system, with energy levels being 0 and $\Delta$, the internal energy tends to $N \Delta /2$ as temperature tends to infinity. At this point, the occupancy of each ...
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Entropy concept
Entropy change does not depend on the heat that is actually absorbed,but it depends on the heat absorbed reversibly.
How?
Since the surroundings emit irreversible heat then how the system which is ...
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Entropy change of an ideal gas undergoing adiabatic expansion into vacuum [duplicate]
For the adiabatic expansion of an ideal gas into an empty chamber, I am told that the entropy change of the system is not zero, and that the entropy change of the surroundings is zero.
But if the ...
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Why is the entropy of deuterium greater than that of hydrogen gas
Why is the entropy of deuterium more than that of hydrogen gas?
I thought about it but couldn't figure out a reason for why that would happen. Why would the number of neutrons in the nucleus ...
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What does negative delta S imply?
What does it mean when there is a negative delta $S$ $(-\Delta S)$? One person asked if this implied negative entropy, but I don't see how this could be possible.
Does this imply a negative change in ...
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Entropy- Judge my knowledge [closed]
Entropy? — So basically I’ve been trying to understand what it is and what I’ve come to realize is. Entropy basically is energy dissipated. What I mean is this — so we know what enthalpy is — it ...
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Entropy of surroundings and heat
Apparently the entropy change of a system can be found by
$$\mathrm dS=\frac{\mathrm\delta q_\mathrm{rev}}T$$
I am slightly confused about this because I have seen this being used when the temperature ...
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Heat transfer with surroundings: why considered reversible?
I do not understand how the fact that the surroundings are large makes heat transfer with them reversible? I understand that the temperature of the surroundings is not going to change in the limit, ...
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Entropy change in mixing a gas at constant temperature and pressure
The expression given on Wikipedia is (https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj-_pDA2IfSAhUFto8KHa2kBAwQygQIIDAA&...
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Entropy as Sum of Kinetic Energy?
Is it possible to view entropy as the sum of the kinetic energy of all molecules in the system? Since a system with 0 entropy would have 0 motion, and as you increase the motion of the molecules, ...
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Why are absolute entropies given the units J mol−1 K−1?
I've just started looking at the concept of entropy and can't understand why absolute (or standard molar entropies) are given the units $\pu{J mol^−1 K^−1}$. Could someone explain the rationale for ...
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Why is ΔS the same regardless of whether a process is irreversible or reversible?
Why do we take the entropy change of the system to be the same in both irreversible and reversible processes? What is the idea behind this?
It would be nice if anyone could give me an example with ...
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What is entropy change in electrochemistry?
I keep seeing entropy change (or reversible effects) and irreversible effects (Joule heating) when reading about charging and discharging of Li-ion batteries. I understand the Joule heating part (the ...
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Thermodynamics: Relation between different types of energy: My Analogy
I have always been confused between the different kind of energies in thermodynamics so today I thought of finally getting it right. Here's my analogy(which is wrong and I need help in improving it, ...
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How to calculate what temperature change in entropy for the reaction equal to the change in entropy for the surroundings given Enthalpy and entropy
A reaction has $\Delta H_\textrm{rxn} = \pu{-107 kJ}$ and $\Delta S_\textrm{rxn} = \pu{285 J/K}$. At what temperature is the change in entropy for the reaction equal to the change in entropy for the ...
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Thermodynamics of DNA double helix formation?
The entropy of a system decreases when 2 single stranded DNA molecules come together and form a double stranded molecule. For this to occur the total entropy of the universe must increase. Thus, heat ...
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Molecules having higher enthalpy of vaporization and boiling point than another but with lower entropy of vaporization?
I came across the Trouton's rule that predicts the entropy of vaporization of most molecules to be around 85~88kJ/(K mol). It is said to fail when there is hydrogen bond between molecules.
When I ...
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Why is N2 enthalpy zero, entropy 191.5, yet G is listed as zero and not [-T*0.1915]?
In standard tables, $\ce{N2}$ at STP has an enthalpy formation ($\Delta H_\mathrm f$) listed as $0\ \mathrm{kJ/mol}$, entropy ($S$) as $0.1915\ \mathrm{kJ/K}$, and free energy of formation ($\Delta G_\...
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Can the enthalpy change of a reaction be changed, and if so, will this affect the value of the equilibrium constant?
In the case of an arbitrary equilibrium reaction, is it possible to change the absolute enthalpy of the final products, thus the reaction enthalpy change? For example, say pH affects the charge ...
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Why can't a reaction go to completion?
What is the reason for why an exergonic reaction would still have some remaining reactants (or an endergonic reaction to have any products)? The explanation given on this page (see Chemical reactions ...
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If entropy is decreased when an enzyme-substrate complex is formed, how can the reaction be feasible?
Is it due to the bond formation creating energy that increases the entropy of the surroundings/universe?
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When ∆Suniv = zero, does the concentration of reactant equal the concentration of product?
It is my understanding that when ∆Stot / ∆Suniv = 0 then the reaction does not occur, the position of equilibrium is not shifted in a specific direction. However, does this imply that [reactants] = [...
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Example of an endothermic reaction that can sustain itself for at least an hour?
Recall that in physical chemistry, the spontaneity of a reaction at constant pressure and a given temperature $T$ can be quantified by the Gibbs free energy
$$\Delta G = \Delta H - T \Delta S$$
A ...
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Deriving the entropy of mixing of a non-ideal solution
In the earlier posted question named Derive expression for internal energy of mixing and entropy of mixing using statistical thermodynamics the entropy of mixing was found by assuming an ideal ...
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Entropy change upon mixing cold and hot water
A closed, well-insulated container is filled with $\pu{454 g}$ of water at $\pu{94.4 ^\circ C}$. To the hot water, $\pu{200 g}$ of water ice at exactly $\pu{0 ^\circ C}$ is added. The mixture reaches ...
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Why can entropy be measured in joules per kelvin?
I'm a little confused as to what the measurement associated with entropy represents. It's obviously the joules of energy per kelvin, but how does this measure the disorder of a system?
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What aspects of a macromolecule/protein do the various contributions to its entropy relate to?
I've come across a few different contributions to entropy in macromolecules such as proteins: configurational, conformational and vibrational. The problem is that I can't seem to find a consistent ...
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Derive expression for internal energy of mixing and entropy of mixing using statistical thermodynamics
I want to derive an expression for the internal energy of mixing, $\Delta_\mathrm{mix}U$, and entropy of mixing, $\Delta_\mathrm{mix}S$. The framework for this is the Lattice Theory of Ideal Solutions....
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Is entropy change of the system for reversible process same as entropy change of the system for irreversible change?
Is entropy change of the system for reversible process same as entropy change of the system for irreversible change? Is Q for reversible change equal to Q for irreversible change? Or the change in ...
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Thermodynamics: Solving for Entropy, Gibbs and Helmholtz
A reversible melting of $32.0\ \mathrm g$ of ice at $0\ \mathrm{^\circ C}$ and $1\ \mathrm{atm}$. Solve for $\Delta G, \Delta S_\text{universe}$, and $\Delta A$
I'm also given latent heat of fusion/...
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Entropy change when indistinguishable particles suddenly become distinguishable
We have that
$$
S = \frac{U}{T} + k\ln Q
$$
Using that for indistinguishable particles in the canonical ensemble
$$
\ln Q_{\mathrm{indis}} = N\ln \frac{q_{\mathrm{tr}}e}{N} + N\ln q_{\mathrm{rot}} ...
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Does a messier room actually have higher entropy?
When my chemistry teacher was explaining entropy, she used the analogy of a clean vs. messy room. What I'm wondering is whether a messy room really does have higher entropy. Does this still work on a ...
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When DNA degrades, does any chemical environment preserve sequence information?
Small bits of DNA information can be found in ancient remains. In analogy to
old bones becoming mineralized, is there a chemical environment in which the
nucleic acid sequence of the original strand ...
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Mechanism for Hydrogen Peroxide decomposition?
Someone asked this question earlier and made no attempt at understanding it on their own so the question was flagged. However, it prompted me to attempt to figure it out. This is what I have come up ...
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Why are protein hydrophobic cores denatured by heat when entropic forces should be favoured at high temperature
The hydrophobic interaction is thought to be driven by an entropic force. If it is, shouldn't hydrophobic interactions be stronger at higher temperatures, where states of higher entropy are favoured? ...
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Why do reactions reach equilibrium?
If the forward reaction causes an increase in entropy then the backwards reaction causes a decrease in entropy, so the backwards reaction is non-spontaneous. If so, then why does the backwards ...
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Is enthalpy of activation the same as activation energy? Is there a purely mathematical way to find that value?
I asked about the effect of pressure on a reaction, and since then I learned a lot more. One of the things I learned was the Eyring equation:
$$\kappa = \frac{\kappa_B T}{h} e^\frac{\Delta^\ddagger S°...
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The road to solvation
To understand the behavior of solubility, it is helpful to look at the chemicals that misbehave, and apply the rules, and look for underlying explanations and common threads. Generally speaking, the ...
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