CHEM 122 11th Edition Lecture 32 Outline of Last LectureI. ThermodynamicsII. SpontaneityIII. EntropyOutline of Current Lecture I. Predicting the sign of Change in EntropyII. 2nd Law of ThermodynamicsIII. Calculating the Entropy ChangesIV. Third Law of ThermodynamicsCurrent LecturePredicting the Sign Change in Entropy:1. Increase in moles of gases yields an increase in disorder (increase in entropy)2. Increase the number of particles yields an increase in disorder (increase in entropy)- Driving Forces for spontaneous processes:1. Enthalpy: an exothermic change serves as a driving force for the process2. Entropy: an increase in entropy serves as a driving force for a process. - A process that is exothermic and has in increase in entropy is always spontaneous.- A process that is endothermic and has a decrease in entropy is never spontaneous.- A process that exothermic and has a decrease in entropy depends on temperature.- A process that is endothermic and has an increase in entropy depends on temperature.- Reversible: a process that can go back and forth between states along the same path at constant temperature. A process that is at equilibrium will be a reversible process.- Irreversible: a process that goes spontaneously in only one direction. - A spontaneous process is not a reversible processThese 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.The Second Law of Thermodynamics: the entropy of the universe increases for a spontaneous process.-∆ Suniv=∆ Ssys+∆ Ssurr o For a reversible process, ∆ Suniv= 0o For an irreversible process ∆ Suniv>0Calculating enthalpy Changes:-nS(products)−¿∑mS(reactants)∆ S=∑¿o n and m are coefficients (moles) in the balanced chemical reactions.- The most highly ordered form of matter is a perfect crystalline solid.Third Law of Thermodynamics: the entropy of a perfect crystalline substance at absolute zero iszero.- In general entropy is expected to increase when:o Solid is converted to a liquido Solids or liquids are converted to gaseso The number of molecules of gases increaseso The temperature of a substance is
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