IMG_0001_NEW_0021 - As-rndinss and Temperature trElrrdc I:H...

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Unformatted text preview: As--rndinss and Temperature . trElrrdc - I:H: Free Energy and Spontaneity Process is spontaneous of AS determined by temperature ASuoi".^.: AS.rr,",n Etrrgy from random motions less randomness = Low -!fnU: A&Hrt + T e'ge Increase in S - El bF: more randomness = High,S ^S + o/o Aeg * llear + Smaller o/o Increase in S If ASry, and A,Sru,. oppose each other how do we determine if a reaction is spontaneous? ^t_a l/T Define new function: Gibbs ASso, q Fre-e Sf-'r<tut?-u -+tU feA:LI'tAn t5 Relationship to AS N*ir"..": Nryrt.. - AS =-*f (O Va G-H-TS -A,Hryru^ Energy LHryrr" l T = -ZAS*'"*,: Mor,.n1 - IASsystem AG LG: AIf - AG and Spontaneity &:6JI- TN atconstant TardP at constant T and P (in standard . . . Rslt 1:-! Spoairainos et f-r lon'tesrFr.tms is dominant) krc not {rmrse Fm (in standard states) 2NHr(g) AG": -33.3 kJ reactions comparison of reaction tendencies MoreNegative LG" + Equilib. furthertoright But, AGo cannot be measured directly. intrm:rall @p€ratucs Hgh tt npcr.turc S9m**bbtds!.raiurcs $m* {rt rc *dkqldiy is t*drtlf uti&por.tantt qt'G + Ads for dilferent + fi,ee energy decreases lslcrc a;*smiit-v states) Nr(g) + 3HrG:) rc < 0 = Spontaneous rc > 0 = NotSpontaneous & :0 = AtEquilibrium . Rdim is spontaneous in the direction ftdbe 6 AG and Chemical Reactions . Standard free energy change: AG" . AGo: Change in free energy (at STP) when: Reactants .-----> Products Sire: ^L* =-+ (@constantT&P) fA.S AGo:AH"- f .f At equilibrium AG = 0 : : spo*nms at arr-y emperaarc b s?ontanru at all tmpcraore) tr-(-)= -\TL) + AS. = AH' T e.g. atPhase change such as ice at273K ...
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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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