CHEM 102 1nd Edition Lecture 9 Outline of Last Lecture I. Decrease in Disorder ExampleII. Third Law of ThermodynamicsIII. Rusting of Iron ExampleIV. Reaction and Surroundings ExampleOutline of Current Lecture I. Calculation ΔS Equations- Example- Natural TendenciesII. Joshua GibbsIII. ΔG Energy Change- ΔG EquationCurrent LectureI. Calculation ΔS Equations- ΔSsurroundings = Δ HTo Where: ΔH is the entropy of the systemo T is Temperature, in Kelvins- ΔSrxn=∑S°products - ∑S°reactantso Where: ∑ is the sum of all S°o S° is the standard disorder for than compound or element- What is ΔSrxn of:o CO(g) + NO(g) CO2(g) + ½ N2 (g)o Use thermodynamics table to determine the ΔS of each compound/elemento ΔS of CO(g) = 197.9, of NO(g) = 219.62, of CO2(g) = 213.6,of N2(g) = 191.50- Using ΔSrxn=∑S°products - ∑S°reactants- ΔSrxn=∑S°products - ∑S°reactantso ΔS = 309.35 – 408.52 = -99.17 J/K- Natural Tendencieso Everything has natural tendencies toward exothermic reactions and more disorderII. Joshua GibbsThese 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.- 1st PhD in Science at American University (Harvard)- Chair of Mathematical Physics at Yale- Studied everything’s natural tendencies toward exothermic reactions and increasing disorderIII. ΔG Energy ChangeExothermic/Endothermic Disorder + or -ΔG (PredictsSpontaneity)Exothermic (-) + Disorder - (Spontaneous)Exothermic (-) - Disorder + (Never Spontaneous) Spontaneous at Low TempsEndothermic (+) + Disorder Depends Spontaneous at High TempsEndothermic (+) - Disorder Depends- When ΔG is positive, never spontaneous- When ΔG is negative, spontaneous- ΔG is 0, equilibrium- ΔG = ΔH – TΔSo Where ΔH is the Enthalpyo T is temperature in Kelvinso ΔS is the spontaneity- ΔG = ∑GProducts - ∑GReactants- ΔG also shows the maximum work that can be done; ΔG =
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