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.
3,029 questions
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Why can we only measure heat and not temperature?
I'm taking chemistry for the first time next semester, so a friend bought me a textbook on the subject. It should probably be mentioned that this textbook is non-traditional, called Chemistry: a Novel ...
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Does temperature-induced change in the equilibrium constant affect the equilibrium concentrations of products and reactants?
Suppose I have an endothermic reaction with the defined equilibrium constant $K_\mathrm{eq}:$
$$\ce{a A + b B <=> c C + d D}$$
If I increase the temperature, $K_\mathrm{eq}$ increases. Does it ...
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How can we assume that concentrations are continuous functions of time and how can we speak of a change in mole numbers that is smaller than one? [duplicate]
I am an undergraduate of chemistry, and I have recently found myself wondering about something very elementary yet somewhat puzzling. Consider a simple chemical equation such as the one below
$$\...
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Coexistence curves in phase diagrams and melting points
[Edited]
I read that "sublimation curve in a phase diagram represent vapor pressure of solid" and "vaporization curve in a phase diagram represent vapor pressure of liquid"
But I ...
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Reconciling experimental ΔH of iron(II) oxidation with silver(I) to a theoretical value
I've been trying to determine $\Delta H$ of the reaction
$$\ce{Ag+(aq) + Fe^2+(aq) <=> Fe^3+(aq) + Ag(s)}$$
experimentally by titrating against potassium thiocyanate at different temperatures (...
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Does the second law of thermodynamic mean that everything will be reduced to atoms/subatomic particles? [closed]
In chemistry, equilibrium is said to favor more of the stable product. And the molecular forms are considered more stable than atomic forms. So I was reading about Why should chemical bonds form at ...
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Assistance in predicting the concentration at the beta phase end of the desorption process
I am working on modelling hydrogen absorption and desorption in metal hydrides (e.g., $\ce{LaNi5}$), and I came across a thermodynamic formulation that connects the equilibrium pressure, temperature, ...
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Why is Ice not in equilibrium with Water at 1 degrees Celsius
Let's not consider supercooling . In this post water means liquid and ice-solid and vapor- gas .I know that water has 3 phases and how their Gibbs free energy changes . Freezing point is where Gibb's ...
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Attempt at proof - how to proceed in proof that dG<0 for a spontaneous reaction?
I have been studying thermodynamics for a few weeks now and am thinking about its applications in chemistry as I am a chemistry undergraduate. In particular, I wanted to derive the criterion for ...
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Entropy change during a reversible isothermal expansion of a van der Waals gas
The change of entropy for van der Waals (vdW) gas is
$$\Delta S_\mathrm{vdW}=nR\ln{\left(\frac{V_\mathrm f-nb}{V_\mathrm i-nb}\right)}.$$
Why is $\Delta S_\mathrm{vdw} > \Delta S_\mathrm{ideal}$ ...
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Should not the definition of enthalpy be $H = E - PV$ if we define work done by the system is taken as negative in chemistry?
In physics, we define the work done by the system as positive and write first law of thermodynamics as $$\Delta Q = \Delta U + \Delta W$$
But in chemistry, authors prefer to define work done by the ...
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Confusion in difference between the enthalpy of hydration and enthalpy of solution
I am currently studying thermodynamics. I am really confused in difference between the enthalpy of hydration and enthalpy of solution. I search on internet ; it shows that the enthalpy of hydration is ...
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Is the degree of dissociation of a reaction fixed throughout the reaction?
The relation of equilibrium constant $K$ and degree of dissociation $\alpha$ is defined as
$$K = \frac{n_0\alpha^2}{V(1 - \alpha)}$$
where $n_0$ is the initial amount of substance and $V$ is the ...
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What does "change in entropy" as in ∆S mean?
I want clarification on ∆S regarding non isolated reversible systems where:
∆Suniv =∆Ssys+∆Ssurr
(as universe is considered isolated).
I agree ∆Suniv (or ∆Ssys if isolated) = 0 (i.e. S is constant) ...
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How is PV work accounted for in enthalpy?
Consider the formula for enthalpy.
$\Delta$H = $\Delta$E + P$\Delta$V
I understand that the P$\Delta$V is not work; it does not confirm to the sign conventions. But then what is it? Are we really not ...
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