Review Ssystem Ssurroundings Suniverse 0 for spontaneous processes
- Slides: 14
Review Ssystem + Ssurroundings = Suniverse > 0 for spontaneous processes Ssurroundings = - Hsys energetic disorder T Ssystem = qr T positional disorder
- Ssystem + Ssurroundings = Suniverse > 0 for spontaneous processes at 298 K H 2 O(s) H 2 O(l) Ssurroundings = - H T Ssurr < 0 spontaneous H a) > 0 b) < Ssurr does not contribute to spontaneity
- + Ssystem + Ssurroundings = Suniverse for spontaneous processes at 298 K H 2 O(s) H 2 O(l) solid liquid spontaneous increasing disorder S > 0 S positional disorder S does contribute to spontaneity
- + Ssystem + Ssurroundings = Suniverse H 2 O(s) H 2 O(l) S solid liquid positive - H / T endothermic negative At high T a) spontaneous Suniv > 0 b) non-spontaneous At low T non-spontaneous Suniv < 0
+ Suniverse= Ssystem+ Ssurroundings > 0 2 NO 2 (g) N 2 O 4 (g) NO 2 - brown, toxic gas N 2 O 4 - colorless gas Ssurr = - H / T H = Hof N 2 O 4 - 2 Hof NO 2 = (9. 66) - 2 (33. 5) = -58 k. J mol-1 Ssurr > 0 favors spontaneity
- + Suniverse= Ssystem+ Ssurroundings > 0 2 NO 2 (g) N 2 O 4 (g) S = Soproducts - Soreactants N 2 O 4 NO 2 So (J mol-1 K-1) 304. 18 239. 95 So. N O a) > So. NO 2 2 4 b) < S = [304. 18 - 2 (239. 95)]= -175. 7 J/mol K 2 mol gas 1 mol gas non-spontaneous
- + Suniverse= Ssystem+ Ssurroundings > 0 2 NO 2 (g) N 2 O 4 (g) S -175. 7 J mol-1 K-1 - H / T +58 k. J mol-1 T(K) At high T a) spontaneous b) non-spontaneous At low T spontaneous
Free Energy G Ssystem+ Ssurroundings = Suniverse > 0 - T S - H T H - T S = Suniverse > 0 = - T Suniverse< 0 G H - TS G = H - T S
G = H - T S G < 0 spontaneous reaction G > 0 non-spontaneous reaction G = 0 equilibrium G = wmax maximum useful work G is an extensive State function Gof = 0 elements in standard states Gorxn = Gof products - Gof reactants
G = H - T S calculate Go for: CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O (l) Gorxn = [ Gof CO 2 (g)+ 2 ( Gof H 2 O (l)) ] - [ Gof CH 4 (g) + 2( Gof O 2 (g))] = - 819 k. J a) > o S rxn 0 o o o b) < G rxn = H rxn - T S rxn = [-892 k. J]-[(298 K) (-242 J/K) ] = -819 k. J
Rubber band Thermodynamics State 1 = relaxed State 2 = stretched go from State 1 to State 2 What is sign of Go + What is sign of Ho a) + o What is sign of S b) Go = Ho - T So +
Ho Go = Ho - T So Go + - always positive - + + + - - always negative a) high T b) low T positive low T a) high T negative b) low T positive high T
Equilibrium Go = Ho - T S Go = 0 phase changes chemical reactions Ho- T So = H 0 o Ho = So T T= Ho So 2 NO 2 N 2 O 4 o prod - Ho react H ______________ f f Soprod - Soreact -58 k. J -175. 7 J/K =T = 331 K
Napoleon - 1812 tin buttons ΔHof (k. J/mol) So (J/mol K) Snwhite tin 0. 0 51. 55 grey tin -2. 1 44. 14 ΔHo = -2. 1 - 0. 0 = -2. 1 k. J SngreyΔSo = 44. 14 - 51. 55 = -7. 4 J/mol K T = -2100 J = 283 K = 10 o. C -7. 4 J/K ∆G 298 =. 105 k. J ∆G 233 = -. 376 k. J
- Suniverse reviews
- Suniverse ervaring
- Concurrent processes are processes that
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