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.

1,604 questions
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Sum of Bond Enthalpies in an Exothermic Reaction

The following reaction is exothermic. In an exothermic reaction, heat is given out to the surroundings so the enthalpy of the reaction mixture should decrease. Hence $\sum$ Reactant Bond Enthalpies ...
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How can change in Gibbs free energy ever be positive?

I have a question regarding this formula for Gibbs free energy of a system: $\Delta$G = $\Delta$H - T$\Delta$S. According to the second law of thermodynamics: T$\Delta$S $\ge$ $\Delta$Q and to my ...
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Could a non-spontaneous reaction occur “on its own”?

Does spontaneity really only apply to the net free energy change of a reaction? I used to be taught that spontaneous reactions could occur on their own BUT without enzymes or a spark they might take ...
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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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Boltzmann Transport equation: Is df/dt=o for collisionless only?

$$\frac{\mathrm df}{\mathrm dt} = \left(\frac{\partial f}{\partial t}\right)_\text{force}+\left(\frac{\partial f}{\partial t}\right)_\text{diff}+\left(\frac{\partial f}{\partial t}\right)_\text{coll}$$...
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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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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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Why is the enthalpy of a reaction equal to the difference between the enthalpies of combustion of the reactants and the products?

My textbook gives me the following formula for calculating the enthalpy change of any reaction: \Delta H_\mathrm{r}^\circ=\sum(\Delta H_\mathrm{c}^\circ)_\text{reactants}-\sum(\Delta H_\mathrm{c}^\...