Free Energy vs Standard Free Zog
Lub zog pub dawb yog dab tsi?
Tus nqi ntawm kev ua haujlwm uas lub tshuab hluav taws xob tuaj yeem ua tau yog hu ua lub zog dawb. Lub zog pub dawb tuaj yeem piav qhia siv ob nqe lus, Helmholtz dawb lub zog thiab Gibbs dawb zog. Hauv chemistry, thaum peb siv lo lus "dawb zog" uas txhais tau tias Gibbs dawb zog. Hauv physics, lub zog dawb yog hais txog Helmholtz dawb lub zog. Ob nqe lus tau piav qhia hauv qab no.
Txoj cai thib ob ntawm thermodynamics cuam tshuam nrog entropy, thiab nws hais tias, "entopy ntawm lub ntiaj teb nce hauv cov txheej txheem spontaneous." Entropy muaj feem xyuam rau cov nqi ntawm cov cua kub generated; uas yog qhov uas lub zog tau degraded. Tab sis, qhov tseeb, tus nqi ntawm cov teeb meem ntxiv los ntawm qhov muab cov cua sov q nyob ntawm qhov kub thiab txias. Yog tias nws twb kub heev lawm, me ntsis ntawm cov cua sov ntxiv tsis tsim ntau yam teeb meem, tab sis yog tias qhov kub thiab txias qis heev, cov cua kub tib yam yuav ua rau muaj kev cuam tshuam loj heev. Yog li ntawd, tsim nyog sau ntawv, ds=dq/T
Tshaj tawm qhov kev hloov pauv, peb yuav tsum xav txog kev hloov pauv hauv ob qho tib si thiab ib puag ncig. Cov kev tsis sib xws hauv Clausius hauv qab no qhia tias muaj dab tsi tshwm sim thaum lub zog hluav taws xob hloov pauv ntawm lub kaw lus thiab ib puag ncig. (Xav tias lub kaw lus nyob rau hauv thermal sib npaug nrog ib puag ncig ntawm qhov kub thiab txias T)
dS – dq/T ≥0.…………(1)
Yog tias cov cua sov ua tiav ntawm qhov ntim tas li, peb tuaj yeem sau cov kab zauv saum toj no (1) raws li hauv qab no. Qhov kev sib npaug no qhia txog cov txheej txheem rau ib qho kev tshwm sim tshwm sim los ntawm kev ua haujlwm ntawm lub xeev nkaus xwb.
dS – dU/T ≥0
Kev sib npaug tuaj yeem hloov kho kom tau qhov sib npaug hauv qab no.
TdS ≥dU (Equation 2), thiab yog li ntawd, nws tuaj yeem sau ua
dU – TdS ≤0
Cov lus qhia saum toj no tuaj yeem yooj yim los ntawm kev siv lub sijhawm Helmholtz zog, A, uas tuaj yeem txhais tau tias, A=U-TS
Los ntawm cov kab zauv saum toj no, peb tuaj yeem muab cov qauv ntsuas rau qhov tshwm sim ntawm tus kheej li dA ≤0. Qhov no tau hais tias, kev hloov pauv hauv qhov system ntawm qhov kub thiab qhov ntim tsis tu ncua yog tias dA ≤0. Yog li kev hloov pauv yog qhov tshwm sim thaum nws raug coj mus rau qhov txo qis hauv Helmholtz lub zog. Yog li ntawd, cov tshuab no txav mus rau hauv txoj hauv kev, kom muab tus nqi qis dua.
Gibbs lub zog pub dawb cuam tshuam nrog cov kev hloov pauv tshwm sim ntawm qhov siab tas li. Thaum tshav kub lub zog yog pauv mus tas li, tsuas muaj kev nthuav dav ua haujlwm; yog li ntawd, peb hloov kho thiab sau cov kab zauv 2 raws li hauv qab no.
TdS ≥dH
Qhov kev sib npaug no tuaj yeem hloov kho kom muab dH-TdS≤0. Nrog rau lo lus Gibbs dawb zog, G, qhov sib npaug no tuaj yeem sau ua, G=H-TS
Ntawm qhov kub thiab txias tsis tu ncua, tshuaj lom neeg cov tshuaj tiv thaiv yog tshwm sim los ntawm kev txo qis Gibbs dawb zog. Yog li ntawd, dG ≤0
Standard Free Zog yog dab tsi?
qauv dawb lub zog yog lub zog pub dawb uas tau teev tseg ntawm cov qauv txheej txheem. Cov txheej txheem yog kub, 298 K; siab, 1 atm lossis 101.3 kPa; thiab tag nrho cov solutes ntawm 1 M concentration. Standard free zog yog denoted as Go.
Dab tsi yog qhov txawv ntawm Dawb Zog thiab Standard Free Zog?
• Hauv chemistry, lub zog pub dawb raug xa mus rau Gibbs dawb zog. Nws muaj feem cuam tshuam nrog cov kev hloov pauv tshwm sim ntawm qhov siab tas li. Standard free zog yog lub zog dawb txhais ntawm cov txheej txheem.
• Yog li ntawd, tus qauv pub dawb yog muab rau ntawm 298K kub thiab 1 atm siab, tab sis tus nqi pub dawb tuaj yeem hloov pauv nyob ntawm qhov kub thiab txias.
