Chemical thermodynamics
Gibbs’ collection of papers provided the first unified body of thermodynamic theorems from the principles developed by others, such as Clausius and Sadi Carnot.The first was the 1923 textbook Thermodynamics and the Free Energy of Chemical Substances by Gilbert N. Lewis and Merle Randall.[1] The primary objective of chemical thermodynamics is the establishment of a criterion for determination of the feasibility or spontaneity of a given transformation.In most cases of interest in chemical thermodynamics there are internal degrees of freedom and processes, such as chemical reactions and phase transitions, which create entropy in the universe unless they are at equilibrium or are maintained at a "running equilibrium" through "quasi-static" changes by being coupled to constraining devices, such as pistons or electrodes, to deliver and receive external work.Even for homogeneous "bulk" systems, the free-energy functions depend on the composition, as do all the extensive thermodynamic potentials, including the internal energy.If the quantities { Ni }, the number of chemical species, are omitted from the formulae, it is impossible to describe compositional changes.Explicitly, For the case where only PV work is possible, a restatement of the fundamental thermodynamic relation, in which μi is the chemical potential for the i-th component in the system The expression for dG is especially useful at constant T and P, conditions, which are easy to achieve experimentally and which approximate the conditions in living creatures While this formulation is mathematically defensible, it is not particularly transparent since one does not simply add or remove molecules from a system.There is always a process involved in changing the composition; e.g., a chemical reaction (or many), or movement of molecules from one phase (liquid) to another (gas or solid).The expressions above are equal to zero at thermodynamic equilibrium, while they are negative when chemical reactions proceed at a finite rate, producing entropy.Of course, it could have been obtained by taking partial derivatives of any of the other fundamental state functions, but nonetheless is a general criterion for (−T times) the entropy production from that spontaneous process; or at least any part of it that is not captured as external work.By accounting for the entropy production due to irreversible processes, the equality for dG is now replaced by or Any decrease in the Gibbs function of a system is the upper limit for any isothermal, isobaric work that can be captured in the surroundings, or it may simply be dissipated, appearing as T times a corresponding increase in the entropy of the system and its surrounding.In solution chemistry and biochemistry, the Gibbs free energy decrease (∂G/∂ξ, in molar units, denoted cryptically by ΔG) is commonly used as a surrogate for (−T times) the global entropy produced by spontaneous chemical reactions in situations where no work is being done; or at least no "useful" work; i.e., other than perhaps ± P dV.The assertion that all spontaneous reactions have a negative ΔG is merely a restatement of the second law of thermodynamics, giving it the physical dimensions of energy and somewhat obscuring its significance in terms of entropy.Similarly, a redox reaction might occur in an electrochemical cell with the passage of current through a wire connecting the electrodes.The current might be dissipated as Joule heating, or it might in turn run an electrical device like a motor doing mechanical work.
chemical reactionslaws of thermodynamicsthermodynamic systemJ. Willard GibbsRudolf Clausiusthermochemistrycombustion reactionsthermodynamicsWillard GibbsOn the Equilibrium of Heterogeneous Substancesthermodynamic equilibriumSadi CarnotGilbert N. LewisMerle Randallchemical affinityfree energyE. A. GuggenheimchemistryspontaneityenergyPhase changessolutionsstate functionsInternal energyEnthalpyEntropyGibbs free energyidentitieslaw of conservation of energyChemical energychemical substanceschemical reactionbond energiesenthalpies of formationheat of combustioncombustionfood energychemical potentialGibbs-Duhem equationdegrees of freedomphase transitionspistonselectrodescompositionextensivethermodynamic potentialschemical specieschemical substancefundamental thermodynamic relationcomponentlivingconservation of massvariableextent of reactionpartial derivativeexpressionstoichiometric coefficientaffinityThéophile de Donderchemical potentialsentropy productionGibbs functionisothermalisobaricsurroundingsdissipatedbiochemistrysecond law of thermodynamicsphysical dimensionsLegendre transformsnon-equilibrium thermodynamicsIlya Prigogineopen systemsdissipative systemssymbiosisisotropicthought experimentchemical kineticselectrochemicalcurrentJoule heatingmechanical workautomobilebatteryhydrolysisphosphatedistancemusclesmitochondriachloroplastscellularorganellesrubberballooncoefficientThermodynamic databases for pure substancesChemical engineeringHistory of chemical engineeringUnit operationsUnit processesChemical engineerChemical processMomentum transferHeat transferMass transferUnit processChemical reaction engineeringChemical process modelingChemical plant designFluid dynamicsProcess designProcess safetyTransport phenomenaOutline of chemical engineeringIndex of chemical engineering articlesEducation for Chemical EngineersList of chemical engineersList of chemical engineering societiesList of chemical process simulatorsGlossary of chemical formulaeList of biomoleculesList of inorganic compoundsPeriodic tableAnalyticalInstrumental chemistryElectroanalytical methods