# Questions tagged [thermodynamics]

Applicable to questions about heat, energy, work, and their interconversion in chemistry. See the tag wiki for a detailed list of topics. Questions tagged may also be tagged with [enthalpy], [energy], [free-energy] where appropriate.

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### How is entropy change defined for a chemical reaction?

I know that: ds = dq/T for reversible processes. Can I write change in entropy of a system in which a chemical reaction is happening using this equation. Basically, my question is about whether a ...
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### Basic question about an expression for Gibbs free energy

I'm getting into thermodynamics, and I have a basic question about the following expression for Gibbs free energy: $G = \sum \mu_i N_i$ Is it correct that this equality only holds for constant ...
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### Why is it necessary to consider infinitesimal changes in p,V,T for H,U and G given that they're state functions?

State functions such as $G$ only depend on the state of the system and are not dependent on the "path" that took the system to that state (which would be the case for work, for example, which is not a ...
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### How to prove that absolute zero is unattainable using Third law of thermodynamics? [closed]

By using second law of thermodynamics and Quantum Mechanics ,we can prove that Absolute zero is unattainable. A question was asked to prove this by using the Third law.
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### Current in a Lithium Ion Battery

I am trying to find the current transferred to the anode and cathode of a Lithium Ion Battery at different voltages. I know the temperature (approximately) of the battery, the battery's starting ...
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### If volatility depends on intermolecular forces, then why in Raoult's law, two substances have different volatility?

I have a doubt, Ideal solutions are solutions where intermolecular forces between solute-solute and solvent-solvent are nearly equal to solute-solvent. Since intermolecular forces between A-A = B-B, ...
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### Why work done Is 0 and why not a negative value?

If a gas expand in vacuum, $P_{ex.} =0$. Then why is the work done 0? Since the gas is expanding, it is doing some work on the piston so the work done must have some negative value.
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### When boiling water, how is evaporation rate affected by the surface area of the container?

Imagine two pots boiling on a stove. One is tall, while one is wide. Both contain the same volume of water. What will be the difference in the rate of evaporation between the two containers?
38k views

### Difference between reversible and irreversible processes

On a quiz, I was asked for the difference between reversible and irreversible processes. I said: For a reversible process, you can change direction at any time without disturbing equilibrium. For an ...
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### If the heat exchanged is different for reversible and irreversible processes, how can enthalpy be a state function?

From the definition of Gibbs free energy, we can write for an irreversible process: $dG=dH-TdS<0$ With $TdS=\pu{q_{rev}//T}$ this becomes: $dH-dq_{rev}<0$ Since G is defined for constant (p,...
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### Why does silver (I) have a larger lattice enthalpy and hydration enthalpy than sodium?

The ionic radius of the $\ce{Ag^+}$ ion is $129$ pm, and that of the $\ce{Na^+}$ ion is $116$ pm. Since the sodium ion is smaller than the silver ion, it makes sense that it has a stronger polarizing ...
6k views

### Why does a hard-boiled egg have more entropy than a normal egg?

The question "Why does a hard-boiled egg have more entropy than a normal egg?" was recently asked on one of my tests. I said that entropy will decrease as a hard boiled egg has molecules in a more ...
6k views

### Will NH3 decompose into N2 and H2?

In chemical kinetics , we learn that in a reversible reaction ,both the forward reaction and reverse reaction occur at the same time. At equilibrium , the rates are the same. For example:Production of ...
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### Methylhydrazine Calorimetry

Below is a chemistry practice problem. I am curious why the change in heat of the oxygen molecules doesn't affect the calculations. Methylhydrazine ($\ce{CH6N2}$) is commonly used as a liquid ...
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### answer the following question [closed]

The following is not true in case of thermodynamic work : (A) We JPav for a reversible process only | (B) W=0ifdV=0 (C) W+ J PdV for a free-expansion process : (D) W is an inexact differential
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### Whats the difference between reversible process in thermodynamics and reversible chemical reactions?

We know that in thermodynamics, reversible process never occur since entropy should be conserved. However, in chemistry we do have a lot of reversed chemical reactions that forms reactants from ...
1k views

### Relation between thermodynamic reversible process and reversible reaction

I know it seems to be a weird question. But for long I have been thinking whether there is any relation between thermodynamic reversible process and reversible reaction. Do they have any connection ...
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### Reversibility of a chemical process based on a graph [closed]

By what parameters can I establish whether a chemical process is reversible or not, based on a graph of the following type (assuming this is an ideal gas and mono-atomic): Thank you!
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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 ...
When $\pu{36.8 g}$ $\ce{N2O4(g)}$ is introduced into a 1.0-litre flask at $\pu{27 °C}$ the following equilibrium reaction occurs: $\ce{N2O4(g) <=> 2NO2(g)}$; $K_p = 0.1642~\mathrm{atm}$. ...