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Questions tagged [entropy]

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

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In dS≥dQ/T, material equilibrium means that there is not material changes at all or that a material change can be reversible and at equilibrium?

I am reading Levine's Physical Chemistry, I know how to arrive to that equation, but I have questions. First, $\mathrm{d}S=\mathrm{d}Q/T$ for material equilibrium, but if there is a heat flow I ...
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How to calculate gibbs free energy [on hold]

How is delta G calculated gibbs free energy it says its has enthalpy in KJ/g Mol and temperature in kelvin but how is entropy measured in what units?
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32 views

Why are catabolic reactions exergonic and anabolic reactions endergonic?

Catabolism breaks apart large molecules and anabolism creates large molecules. Catabolism is supposed to be exergonic, while anabolism is supposed to be energonic. Id on't really understand this. By ...
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Entropy change between between temperatures? [duplicate]

My chemistry textbook mentions the formula for change in entropy as $$\Delta S= \dfrac{\Delta q_{rev}}{T}$$ It then tells me that to calculate ΔS for a change between two temperatures, one would sum ...
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Entropy of lead storage cell

I am having trouble with calculating the entropy of a lead storage cell. The standard cell potential is given as $\pu{2 V}$ and the standard enthalpy change is $\pu{-306 kJ}$. I found out the Gibbs ...
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1answer
21 views

How does the concentration of a gas affect the entropy of a system in a chemical equilibrium?

The question asks about factors that increase the entropy of the system. The mark-scheme states that "decreasing the concentration of a gas without changing the volume of the container" is the answer. ...
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1answer
46 views

Thermodynamic stability and Inertness [duplicate]

The following is from my teacher's notes: The reaction (where the reaction mixture is thermodynamically unstable but kinetically inert) tends to go as indicated by a positive total entropy change, ...
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Why HF hydrogen bond become stronger in gas phase than liquid phase?

I found that $\Delta S_\mathrm{vap}$ of HF(similar as the ratio of the molar heat of vaporization of a liquid to its boiling point) is smaller than $90\ \mathrm{J\ K^{-1}\ mol^{-1}}$ which came from ...
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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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35 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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87 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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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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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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47 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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141 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
53 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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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
85 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
120 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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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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237 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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600 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
105 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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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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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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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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79 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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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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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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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
485 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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106 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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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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652 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
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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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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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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
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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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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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344 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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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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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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393 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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740 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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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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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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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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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 ...