On equilibrium constant 0 k1 k1 exp eaf wd rt 0 k 1

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Unformatted text preview: perature is increased! Le Châtelier’s Principle: Example Produc!on of Ammonia (Haber process): N2 + k1 3H2 ⌦ k-1 At Equilibrium: 2N H3 , 298 HrxnK = 92kJ/mol exothermic reac7on Keq n2 H3 k1 = = N3 k1 nN2 nH2 As T increases Keq decreases, and thus the equilibrium yield of NH3 decreases; The reac!on shiLs to the leL N2 + 3H2 ! 2N H3 + Hrxn As P increase the equilibrium shiLs to the right and the yield of NH3 increases; The equilibrium moves in the direc!on of fewer molecules. N 2 + 3H 2 ! 2N H3 + Hrxn I.e. system tries to minimize increase in pressure by producing fewer molecules Reac7on for Elementary Reac7on A+B k1 ⌦ k-1 C + heat ac7va7on state A+B C Arrhenius equa!on: Equilibrium Constant: 0 k1 = k1 exp( Ea,f wd /RT ) 0 k-1 = k-1 exp( Ea,rev /RT ) Keq 0 k1 k1 exp( Ea,f wd /RT ) = =0 k-1 k-1 exp( Ea,rev /RT ) Heat of Reac7on A+B k1 ⌦ k-1 C + heat H0 < 0 A+B exothermic C From Arrhenius equa!on: Thermodynamics: Keq 0 k1 k1 exp( Ea,f wd /RT ) = =0 k-1 k-1 exp( Ea,rev /RT ) Keq = exp Ea,f wd ✓ G RT 0 ◆ = exp Ea,rev = ✓ H0 S R 0 ◆ exp ✓ H RT 0 ◆ Rate of Produc7on in a Batch Rector T0 specify temperature nj (t) n A0 n A x= n A0 Conversion of species A: Rate of produc!on species A: CA = nA /VR A k1 ⌦ k-1 B k1 CA0 (1 Func7on of temperature RA k1 CA + k-1 CB NA (t) + NB (t) = NA0 Conserva!on of mass: RA = RA = x=1 x) + k 1 C A0 x T = constant RA = 0 xeq x CA CA0 Concentra7on Profile in Batch Reactor T0 specify temperature nj (t) CB eq CB CA eq CA CA = nA /VR A k1 ⌦ k-1 teq B !me Frac!onal conversion of species A: RB = k1 (1 x=1 x) eq C B VR Produc!on rate of species B: = teq CA CA0 7me to reach equilibrium depends on temperature k-1 x (Moles of B per unit !me) Is there an op!mal temperature to operate the react...
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This document was uploaded on 03/14/2014.

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