IMG_0005_NEW_0001 - cC + dD . Equilibrium constants for...

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Equilibrium Expressions For Gases To describe equilibria involving gases usually use partial pressures instead of concentrations Partial pressure : independent pressure exerted by each gas in a mixture Equilibrium expression for gases: *o + bP" =- cPc + dPD Equilibrium constant for partial pressures (rKr): u -(P.)"(Po)o ^r - 1polpY . Total pressure = sum ofthe partial pressures Pro,a: P^ + PB + Pc t Po . Units of prressure: S.I. Unit: Pascal (Pa) orAtrnospheres (atm), I atrn: 101.325 kPa Equilibrium Constants and Activities . Equilibrium constants = thermodynamic quantities > Instead of Concentration and Pressure Use Activities . Activity: effective concentration or partial pressure of a species . - Actirrity + Ratio of P or Conc. toBgfe,rcnce . Gas: Actitzity(c orrponent i) = a, . Solution: Actirzity(c onporrcnt Relationship between K and Kp . To describe equilibria involving gases can use: - Partial Pressures: *o + bP" : cP. + dPo OR- Concentrations: aA + bB =-
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Unformatted text preview: cC + dD . Equilibrium constants for gases . Ideal gas law + Pressure ++ Conc. relationship a K(RZlcextu:;ffi$ K" *(RZ)eXe:sI=T1& An: (sum of coefficients of gaseous products)- (sum of coefficients of gaseous reactants) lAl"[B]o Equilibrium Constants and Activities O Equilibrium constant in terms of activities: Fromconcentrations: aA + fS: cC + dD frcr(M))'fpr(M)\' "-(a.)"(ao)d -1. rM J l. lM ./ -tcl"tpl' '- 1ao)'(a")b rtAl(M))"rFl(M)'.\' tAr[BJ' I rM .il rM ./ ( r.1arq ')"( rolarn; )' I r"o" J t l"t"r ,, = ( r^1ar4 )"( r"1arn; '\h l. I "rr .J l. t.t" l Frompartialpressures: *o + bP" =- cP. * dPo n _la.)"(ao)d _ ^" - t"^tltoJ -) Pure solids and liquids _ [pure so[d] [pwe sohd] aPurcrcrid: tR"r"*"f = [o*" *0, =' lpre huill [pure huil] to*"ou,o=;p"6,g;e] = [r.'* lio*, =' For pure solids and liquids, the reference state is the pure solid or liquid Activity of pure solid and liquids always: I 8...
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This note was uploaded on 12/27/2011 for the course CHEM 122 taught by Professor Williams during the Fall '10 term at Simon Fraser.

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