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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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What's greater, enthalpy of combustion or heat of combustion? [closed]

What is the difference between the two? In my assignment book there is this question which asks if enthalpy of combustion is greater than, equal to or less than the heat of combustion. The answer ...
65 views

Relationship between Gibbs free energy and potential energy (related to reaction coordinate diagrams)

For a rate law, the rate constant $k$ is given by the equation $$\ln k = \ln A - \frac{E_\mathrm{a}}{RT}\tag{1}$$ If $k_\mathrm{fwd}$ is the forward rate constant and $k_\mathrm{rev}$ is the reverse ...
3k views

Why does thermodynamics only apply to macroscopic systems at equilibrium?

A text says: The laws of thermodynamics deal with energy changes of macroscopic systems involving a large number of molecules rather than microscopic systems containing a few molecules. ...
11k views

Is molarity an intensive property?

$$\mathrm{molarity} = \frac{\text{amount of solute}}{\text{volume of solution}}$$ and amount of substance is based on quantity (larger mass means larger amount), so how come it is an intensive ...
5k views

Why are hydrogenation reactions exothermic?

I learned that all reactions that yield hydrogen are endothermic (such has reforming) and reactions that use up hydrogen are exothermic (FCC cracking, hydrogenation, etc.). But why is this so? I know ...
109k views

Difference between thermodynamic and kinetic stability

What is the difference between thermodynamic and kinetic stability? I'd like a basic explanation, but not too simple. For example, methane does not burn until lit -- why?
12k views

Spontaneous/Non-Spontaneous Reactions and Reversible Reactions

My chemistry textbook states "Reversible reactions constitute a limiting case between spontaneous and non-spontaneous processes." Does this mean that some of the reversible reactions are spontaneous ...
2k views

Does an irreversible reaction have an equilbrium between reactants and products?

Retrospective analysis 2/13/2017 -- The barium sulfate example is a poor choice. Equilibrium equations should really be defined using activities, and the activity of solid barium sulfate is by ...
212 views

Why does Gibbs free energy correspond solely to non-expansion work?

First of all: I know this question has been asked before (Why does the Gibbs free energy only correspond to non-expansion work?), and although I understand the mathematical derivation given there, I ...
If 1 mole of gaseous carbon atoms are converted into diamonds, calculate enthalpy change of process given that bond enthalpy of $\ce{C-C}$ bond is $\pu{400 kJ mol-1}.$ According to me, the answer ...