Chem 113 1st Edition Lecture 4 Outline of Last Lecture I. Comparing energy and entropyII. Predicting the sign of ΔS°sysIII. Applications of the Second Law of ThermodynamicsIV. Entropy changes in surroundingsV. Calculating entropy changesVI. Temperature at which heat is transferredOutline of Current Lecture I. Components of ΔS°univ for spontaneous reactionsII. ΔHsys and the ΔSunivIII. Gibbs Free EnergyIV. Calculating ΔGCurrent LectureI. Components of ΔS°univ for spontaneous reactionsa. For an exothermic reaction in which ΔSsys>0, the size of ΔSsurr is not important since ΔSsurr>0 for all exothermic reactions. The reaction will always be spontaneousb. For an exothermic reaction in which ΔSsys<0, ΔSsurr must be larger than ΔSsys for the reaction to be spontaneousc. For an endothermic reaction in which ΔSsys>0, ΔSsurr must be smaller than ΔSsys forthe reaction to be spontaneous. ΔSsurr is always <0 for endothermic reactions.II. ΔHsys and the ΔSuniva. The enthalpy of a reaction affects the surroundingsi. qsurr= -ΔHsysii. Heat flows out of an exothermic reaction and into the surroundingsiii. Heat flows into an endothermic reaction from the surroundingsb. Hows does ΔHsys affect the ΔSsurr?i. ΔSsurr =qsurr/T and ΔSsurr =- ΔHsys/TIII. Gibbs Free Energya. Gibbs proposed the change in free energy of a process occurring at constant temperature and pressure is related to ΔSuniv via: ΔGsys=-T ΔSunivi. Notes the sign of ΔGsys and ΔSuniv are oppositeb. The free energy change (ΔG) is a measure of the spontaneity of a process and of the useful energy available from itThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. ΔGsys= ΔHsys-T ΔSsys1. ΔG>0 for a spontaneous process2. ΔG<0 for a nonspontaneous process3. ΔG=0 for a process at equilibriumIV. Calculating ΔGa. ΔGrxn can be calculated using the Gibbs equation:i. ΔGsys= ΔHsys-T ΔSsysb. ΔGrxn can also be calculated using values for the standard fee energy of formation of the componencti.
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