# lec 1 - Thermodynamics vs Kinetics Chemical Reaction or...

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Unformatted text preview: Thermodynamics vs Kinetics Chemical Reaction or Biological Process: K eq = [B]/[A] = k f /k rev (Thermo, 107A) k f = forward rate constant (Kinetics, 107B) Thermo predicts how far a rxn proceeds (i.e. % yield). State function depends on difference between final & initial state ( ∆ G°). Kinetics measures how fast (seconds, minutes or millenia). Rate depends on barrier and details of pathway . K eq = [B]/[A] ∝ exp(- ∆ Gº/RT) k f ∝ exp(-E a /RT) C(s) diamond → C(s) coal B A Time Conc Rxn coordinate Free Energy A B ∆ Gº E a A → B k f → k rev K eq ~ 10 4 1/k f ~ 1000 yrs A → B k f → k rev Kinetic Theory of Gases (Ch 2.6-2.9) Why study gases? • Gas properties (pressure or volume) relate to speed of moving molecules (hence, kinetics). • Gas properties are easy to measure (PV = nRT). • Gas reaction kinetics modeled by molecular collisions: A → B rate ∝ (# of collisions) X (collision speed) • Kinetics of ideal gas generalize to kinetics of biological reactions in dilute solution (i.e. ideal soln: <10-3 M). Ch 2 Homework Problems : 52, 54, 56, 58, 62, 64, 68, 78, 98 Ideal Gas Properties and States Pressure (P) = Force/area (# collisions/area) Volume (V) = length* width* height Temp (T) ∝ average velocity of gas molecule n = number of gas molecules (moles) R = ideal gas constant = 8.314 J K-1 mol-1 = 0.08206 L atm K-1 mol-1 PV = nRT (Ideal gas law) # of gas molecules (N) in 1-liter box: Pressure V o l u m e P = nRT V V = nRT P moles K mol K atm L L atm RT PV n 04 . ) 298 )( 08206 . ( ) 1 )( 1 ( 1 1 = ⋅ ⋅ ⋅ = = − − molecules mole moles nN N A 22 23 10 46 . 2 1 10 022 . 6 ) 04 . ( × = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ × = = Kinetic Theory of Gases Model: • Gas consists of large number of molecules far apart on average (~10 23 in 1-liter)....
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lec 1 - Thermodynamics vs Kinetics Chemical Reaction or...

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