Questions tagged [entropy]
For questions about the thermodynamical state function entropy, commonly understood as a measure of disorder.
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Dependence of change in entropy on temperature
The thermodynamic definition of entropy is expressed as
$$dS = \frac{dq_{rev}}{T}$$
I understand that it depends on amount of heat transferred because heat transfer can be understood as the degree of ...
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Why the dilution of solvent doesn't affect the solid phase, in comparison to the liquid phase?
Dilution of the solvent adds new energy states to the liquid, but does
not affect the solid phase.
The above line appeared on the following page under the section "5: Colligative properties and ...
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Plotting ΔG vs Temp for Electrochemical Reaction
I’m doing an electrochemistry lab that requires me to construct various galvanic cells in an attempt to solve for $\Delta H$, $\Delta G$, and $\Delta S$ values of an unknown. During one part of the ...
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How to calculate the entropy change of benzene when it changes from vapour into liquid?
Given information:
The boiling point of benzene at atmospheric pressure is $353~\mathrm{K}$
the enthalpy of vaporization of benzene is $30.8~\mathrm{kJ~mol^{−1}}$ at this temperature.
...
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Predict Entropy based on the Balanced Equation
You cannot use values but must determine from looking
The equation I have trouble with is as follows:
$$\ce{2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2}$$
According to my teacher the entropy is ...
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Why does everything go in the direction of positive entropy change?
I read about entropy from different sources. Still don’t get why (universal) entropy change has to be greater than zero for irreversible process, i.e. $\mathrm{d}S_\mathrm{Univ}>0$. Is it a result ...
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What is the difference between ΔG and ΔG "with an o on top"? [duplicate]
What is the difference between $\Delta G$ and $\Delta G^\circ$? I couldn't figure it out.
Ex:
$\Delta G^\circ = -RT\ln K$
$\Delta G = \Delta G^\circ + RT \ln Q$
What is the difference, is it that $\...
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Why is it that increasing the molar mass generally increases the Entropy? [closed]
I've just found read that entropy increases through these reasons:
Changing the phase of the elements to a gas.
Increasing the molar mass of that specific element increases the entropy.
I understand ...
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In entropy change of surroundings, what is T?
This question is simpler than the previous one about intuition of entropy; I just need to know whether the $T$ term in $dS_{Surr} = \frac{-dH}{T}$ refers to the temperature of the surroundings or the ...
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Truly Understanding the Second Law of Thermodynamics and Entropy
There are some seemingly contradictory things I’d like cleared up:
Second Law states: $\mathrm dS_\text{univ} = \mathrm dS_\text{sys} + \mathrm dS_\text{surr}$, and $\mathrm dS_\text{univ}$ is always ...
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Is time a measurement of Entropy?
Is time a measurement of entropy? Is it because time is increasing forever?
Well after reading about the Second Law of Thermodynamics and working with Entropy, I began to realize that if time can be ...
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Raoult's Law explained with thermodynamics/ free energy
I got some confusion going on with this explanation of Raoult's Law.
This is what my book say:
Because the ideal solution has a higher entropy than the pure solvent, the energy of a vapor ...
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Are all naturally occuring reactions exothermic?
If a reaction is endothermic, then the reaction must take energy from the environment to occur (as far as I know), and if this is the case, then to me the reaction seems energetically unfavorable, as ...
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Where to find data for Gibbs energy, enthalpy, and entropy?
Where can you find the enthalpy and Gibbs free energy of formation and entropy of compounds either as a data file or web API? Technically, I only need two since I can figure out the other one from two ...
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How do I determine if a process is reversible without numeric information?
How do I determine if a process is reversible without numeric information?
It would be nice to know how to determine whether a process is reversible in order to solve problems LIKE this one:
A ...
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How can enthalpy change of a system be negative while entropy change is positive?
$$\Delta G = \Delta H_\text{system}-T\Delta S_\text{system}$$
$$
\begin{array}{ccc}
\hline
\text{Sign of}~ΔH & \text{Sign of}~ΔS & \text{Spontaneity} \\
\hline
+ & + & \text{The ...
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Entropy change of system in adiabatic irreversible process [duplicate]
In an adiabatic irreversible process we know that q = 0. Now change in entropy is defined as q/T. So when q is zero, why is change in entropy not zero ?
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Can a reaction with positive Gibbs free energy change ever occur?
If you have an endothermic reaction with a negative entropy change, is it still possible to induce the reaction in some way despite the fact that the Gibbs free energy change is positive or all ...
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Entropy - Negligible?
In electrochemistry, the Nernst equation tells us the cell potential for non-standard conditions. I read that the factor $\frac{-RT}{nF}\ln{Q}$ accounts for difference in cell potential due to ...
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Does adsorption violate thermodynamics?
My textbook reads as follows:
When a gas is adsorbed, the freedom of movement of its molecules become restricted. This amounts to decrease in the entropy of the gas after adsorption, i.e. Entropy ...
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Formula of entropy change
In my 12th standard book, the formula for entropy change is given as $\Delta S = \frac{q_\text{reversible}}{T}$. What is the importance of absorbing heat reversibly and not irreversibly? What does ...
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Heat given off from an electrochemical cell compared to mixing reactants
My confusion regarding the difference between the heat given off in a reaction that takes place in an electrochemical cell compared to in a beaker/appropriate container when the reactants are simple ...
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What value of temperature does T represent in Gibbs Free Energy Equation?
Temperature before, or after reaction? Temperature change? Or what is it?
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Whats the difference between entropy and the (dis)order of a system?
Entropy is often verbally described as the order/disorder of the thermodynamic system. However, I've been told that this description is a vague "hand-waving" attempt at describing what entropy is. For ...
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How to prove that entropy is a state function?
Consider the following steps:
\begin{align}
\mathrm{d}U &= \mathrm{d}q - p\,\mathrm{d}V\\
\mathrm{d}U &= C_V\,\mathrm{d}T\tag1\\
\end{align}
Side question: Is equation $(1)$ only true for a ...
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What Causes there to be a Maximum Amount of Salt which can be Dissolved in Water?
When you add salt to water and stir, after a while the salt will no longer dissolve. Why is this?
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Which has a greater entropy?
Which of the following has greater entropy?
a. $\ce{CH3COOH~ (aq)}$
or
b. $\ce{CH3COO^{-}~ (aq) + H+~(aq)}$
They are both in the same state, and have the same number of particles.. so how do ...
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How can -G/T and -A/T be thought of as 'disguised' entropies?
I understand that entropy is defined as $\mathrm{d}S=\mathrm{d}q/T$ for a reversible change but I fail to see why $-G/T$ and $-A/T$ can be thought of as 'disguised' entropies. This is a question on my ...
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If dS ≥ dq/T for a spontaneous change is dS ≤ dq/T for a non-spontaneous change and is that even possible?
I am struggling with the concept of entropy but might be on the verge of understanding it. The Clausius inequality, $$\mathrm{d}S \geq \mathrm{d}q/T,$$ is true for all spontaneous changes with the ...
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What does the Clausius Inequality mean in thermodynamics? (entropy)
$$\delta S\ge\frac{\delta q}T$$
I don't understand how a quantity (the change in entropy in this case) can be greater than the very thing that defines it ($\mathrm{\frac{\delta q}{T}}$).
Also what ...
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What kind of chemicals would exist at the heat death of the universe?
As the universe reaches the maximum entropy, presumably only the most stable chemicals would exist.
Assume that all the elements haven't turn into iron yet, what kind of chemicals would dominate at ...
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Is it possible for a reaction to have an entropy change of zero?
If the question seems rather "unscientific", be kind to accept my apology. My textbook is being highly unclear about the topic and I need to know the answer to this question before I go on with my ...
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Entropy - "Wiggle"?
The title is not a reference to a Jason Derulo song.
In any case:
1) How is change in entropy measured, experimentally? I've Googled this for a bit and I've found all sorts of mathematical ...
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The spontaneity of a redox reaction
Suppose we have a redox reaction and we want to see in what direction the reaction is spontaneous. We do this by comparing the standard reduction potentials of the sub-reactions available in the main ...
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Greater entropy: an atom or macromolecule?
A question that appeared on my last chemistry exam was :
Which of the following has greater entropy A) An atom
B) A
macromolecule
The question doesn't specify anything else(i.e. type/size of ...
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Entropies of Solvation for Chlorate and Nitrate Anions
Can anyone find any data on the entropies of solvation for these two anions in water solution? I can't find any.
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Calculation of the enthalpy change of reactions
First, I’m a high school student and I wonder why every textbook just tells you how to set up those equations and cancel them to get the entropy change but never tells you why you can cancel the same ...
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Which temperature is meant in the Gibbs free energy equation? [closed]
In the equation for Gibbs free energy change, $\Delta G = \Delta H - T\Delta S$, does $T$ refer to the temperature of the system or the surroundings?
I know we have to calculate Gibbs free energy of ...
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Entropy of solid, liquid, and gas at triple point of water
At the triple point of water how do the entropies of solid,
liquid, and gas compare?
I think that either they will be equal or it will be that gas > liquid > solid.
I don't know if entropy is ...
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Clarifications on the calculation of the $\Delta\mathrm{G}$ of a reaction
I'm trying to calculate the $\Delta\mathrm{G}$ of the following reaction. Are my calculations correct? I'm also a bit puzzled, 'cause this is a endoergonic reaction right? But the $\Delta\mathrm{G}$ ...
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Spontaneity of an exothermic reaction when temperature is decreased
How is the spontaneity of an exothermic reaction changed when temperature is decreased?
Assuming the entropy is negative.
Using Gibbs free energy equation, $\Delta G=\Delta H-T\Delta S$, $\Delta G$ ...
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Does minimizing ANY type of energy ALWAYS predict a state of equilibrium?
My intuition says no, but I am having trouble coming up with concrete examples.
I know that minimizing Gibbs free energy predicts a state of equilibrium, while minimizing kinetic or internal energy ...
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The entropy change during micellization
I was reviewing the thermodynamics of micelle formation from the Wikipedia page and this book. I understood most of the arguments but micellization is supposed to be an entropy driven process with a ...
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Does all processes that consume energy from outside result in negative entropy change?
In any spontaneous process entropy increases.In biological systems disordered elements are converted into highly ordered tissues etc(-ve entropy change) which make up living organisms. But, it ...
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