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OpenStax Chem 16
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Term | Definition |
---|---|
entropy (S) | state function that is a measure of the matter and/or energy dispersal within a system, determined by the number of system microstates often described as a measure of the disorder of the system |
Gibbs free energy change (G) | thermodynamic property defined in terms of system enthalpy and entropy; all spontaneous processes involve a decrease in G |
microstate (W) | possible configuration or arrangement of matter and energy within a system |
nonspontaneous process | process that requires continual input of energy from an external source |
reversible process | process that takes place so slowly as to be capable of reversing direction in response to an infinitesimally small change in conditions; hypothetical construct that can only be approximated by real processes removed |
second law of thermodynamics | entropy of the universe increases for a spontaneous process |
spontaneous change | process that takes place without a continuous input of energy from an external source |
standard entropy (S°) | entropy for a substance at 1 bar pressure; tabulated values are usually determined at 298.15 |
K and denoted S°298 | standard entropy change (ΔS°) change in entropy for a reaction calculated using the standard entropies, usually at room temperature and denoted Δ°298 |
standard free energy change (ΔG°) | change in free energy for a process occurring under standard conditions (1 bar pressure for gases, 1 M concentration for solutions) |
standard free energy of formation (ΔGf° ) | change in free energy accompanying the formation of one mole of substance from its elements in their standard states |
third law of thermodynamics | entropy of a perfect crystal at absolute zero (0 K) is zero |