CHEM 104 1st Edition Lecture 25- Matter and energy will disperse in a spontaneous process (entropy)o Ex: probability that 2 particles stay in initial flask: (1/2)2 = ¼Probability that 3 particles stay in initial flask: (1/2)3 = 1/8 Probability that all particles will stay in initial flask: (1/2)N ~ 0 (N=6.022*1023 particles, i.e. 1 mol) - There is much higher probability that energy is dispersed over many particles, than concentratedin only a few particles - Entropy = measure of how many microstates are associated with a particular macroscopic state o Entropy is state function, i.e. ∆S = Sfinal – Sinitial - S = klnW o S = entropy, k = Boltzmann constant (1.38*10-23 J/k), W = number of microstates o ∆S = kln(Wf/Wi) If Wfinal > Winital ∆S > 0 (signifies dispersion of matter/energy, more microstates)o ∆S = qreverse/T q = heat transferred reversibly into the system, T = temperature in Kelvin - Second law of thermodynamics: the entropy of the universe increases in a spontaneous process o ∆Suniverse = ∆Ssystem + ∆Ssurroundings > 0 - Entropy and physical states: S(s) < S(l) < S(g) - Entropy and solutions: when a solid is dissolved in a solvent, entropy increases – same for liquids/gases in solutions (i.e. mixtures) - Entropy and chemical reactions: depends on states, and the greater the number of moles the higher the entropy - Third law of thermodynamics: the entropy of a crystalline solid is zero at 0 Kelvin o S = klnW if W = 1, then S = O- Larger and more complex molecules have greater entropies These 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.- Standard molar entropies (S˚) = molar entropies for substances at standard conditions (i.e. 1 bar, 298 K) o S˚ increase for solid < liquid < gaso S˚ for elements ≠ 0 o Larger molecules have higher S˚ ∆S = ∑nproductsS˚products -
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