1、Chapter 18Chapter 18Entropy,Free Energy,and EquilibriumEntropy,Free Energy,and Equilibrium100-2 Semester18.1 The Three Law of Thermodynamics 熱力學的三個定律熱力學的三個定律w Thermodynamicsw Law of Thermodynamicsw Enthalpy(DH)熱力學熱力學定義焓Vocabulary and Phrase 字與詞18.1 The Three Law of Thermodynamics 熱力學的三個定律熱力學的三個定律定義與
2、例句閱讀The first law of thermodynamics:Energy can be converted from one form to another,but it cannot be created or destroyed.ConvertCreateDestroy轉換創造毀滅中譯中譯:熱力學第一定律:能量可已由一種形式轉換為另一種形式,但不能被創造或毀滅。wqDU18.1 The Three Law of Thermodynamics 熱力學的三個定律熱力學的三個定律定義與例句閱讀One measure of changes in energy is the amount
3、 of heat given off or absorbed by a system during a constant-pressure process,which chemists define as change in enthalpy.Give offAbsorb散發吸收中譯中譯:能量改變得一種計量方式是定壓程序中系統所發散或吸收的熱量也就是化學家所定義的焓的變化量。18.2 Spontaneous Process 自發程序w Spontaneousw Non-spontaneousw Spontaneous reaction自發的非自發的自發的反應Vocabulary and Phr
4、ase 字與詞18.2 Spontaneous Process 自發程序定義與例句閱讀A reaction that does occur under a given set of conditions is called a spontaneous reaction.中譯中譯:一個反應自一組特定條件下能發生即稱之為自發反應。If a reaction that does not occur under specified conditions,it is said to be non-spontaneous.中譯中譯:Spontaneous processSpontaneous proces
5、sNonspontaneous process18.3 Entropy 火火商商w Entropy(S)w Change in entropy(DS)w Microstate(S=k lnW)w Standard entropy火火商商火火商商 的變化量微狀態標準火火商商Vocabulary and Phrase 字與詞18.3 Entropy 火火商商定義與例句閱讀Entropy is often described as a measure of how spread out or dispersed the energy of a system is among the differen
6、t possible ways that system can contain energy.中譯中譯:火商通常被描述為一個系統。18.3 Entropy 火火商商The greater the dispersal,the greater the entropy.中譯中譯:The greater the number of microstates,the greater is the entropy.中譯中譯:18.3 Entropy 火火商商定義與例句閱讀Like enthalpy,entropy is a state function.中譯中譯:如同焓一樣,火 商 是一個狀態函數。18.3
7、 Entropy 火火商商定義與例句閱讀A system with fewer microstates(smaller W)among which to spread its energy(small dispersal)has a lower entropy.中譯中譯:一個系統中能量能散佈的微狀態比較少時(W小,散佈小),該系統的火 商 值也較小。A system with more microstate(larger W)among which to spread its energy(large dispersal)has a higher entropy.中譯中譯:18.3 Entro
8、py 火火商商定義與例句閱讀Standard entropy is the absolute entropy of a substance at 1 atm and 25.中譯中譯:標準火 商 是物質在1大氣壓下25 時的絕對火 商 。The units of entropy are J/K or J/K mol for 1 mole of the substance.We use joules rather than kilojoules because entropy values are typically quite small.中譯中譯:火 商 的單位是(焦耳/K)或是 對一莫耳的物
9、質而言是(焦耳/K mole)中譯中譯:我們使用焦耳而非千焦是因為火 商 的數值通常相當的小。MeltingVaporizationDissolvingHeatingSliquid SsolidSvapor SliquidSsolution Ssolute+Ssolvent18.4 The Second Law of Thermodynamics 熱力學第二定律w Entropy change in the system(DSsys)w Standard entropy of reactionw Entropy change in the surrounding(DSsurr)w The ch
10、ange in entropy of the universe(DSuniv=DSsys+DSsurr)w The third law of thermodynamicsw Absolute entropyVocabulary and Phrase 字與詞系統火 商 變化量標準反應火 商環境火 商 變化量火 商 值總變化量熱力學第三定律絕對火 商 值18.4 The Second Law of Thermodynamics 熱力學第二定律定義與例句閱讀The second law of thermodynamics:The entropy of universe increases in a
11、spontaneous process and remains unchanged in an equilibrium process.中譯中譯:熱力學第二定律:宇宙的火商在自發程序中是增加的而在平衡中是保持不變的。TqrevDS18.4 The Second Law of Thermodynamics 熱力學第二定律定義與例句閱讀For a spontaneous processFor an equilibrium process0SDDDsurrsysunivSS0SDDDsurrsysunivSS18.3 Entropy 火火商商定義與例句閱讀Standard entropy of re
12、action is given by the difference in standard entropies between products and reactants.中譯中譯:反應火商是產物與反應物標準火商值的差。)(reactants(products)S000nSnSrxnDEntropy in the SurroundingsAn exothermic process transfers heat from the system to the surroundings and results in an increase in the entropy of the surroun
13、ding.An endothermic process absorbs heat from the surroundings and thereby decrease the entropy of the surrounding.THsyssurrDDS18.4 The Second Law of Thermodynamics 熱力學第二定律定義與例句閱讀If the change in entropy DSuniv is positive,we predict the reaction is spontaneous at that temperature.中譯中譯:當總火商值(DSuniv)
14、的變化量為正值,我們可預測在該溫度下反應是自發的。18.4 The Second Law of Thermodynamics 熱力學第二定律定義與例句閱讀The third law of thermodynamics:The entropy of a perfect crystalline substance is zero at the absolute zero of temperature.中譯中譯:熱力學第三定律:完美結晶物質在溫度0時其火商值也為0。0lim0SKT18.5 Gibbs Free Energy(吉卜氏)自由能w Gibbs Free Energy(free energ
15、y)G=H-TS;DG=DH-TDSw Standard Free-Energy Changes()w Standard free energy of formationw Phase transitionVocabulary and Phrase 字與詞自由能標準反應自由能變化量 標準聲成自由能相變化0GrxnDPhase transitionMeltVaporizationCondensationFreezeSublimationVapor deposition 18.5 Gibbs Free Energy 自由能定義與例句閱讀G=H-TSG is called Gibbs Free En
16、ergy,or simply free energy.G has the units of energy.Like H and S,G is a state function.中譯中譯:G稱為吉卜氏自由能或簡稱為自由能。中譯中譯:自由能G具有能量的單位。中譯中譯:如同焓H與火商 S,G是狀態函數。18.5 Gibbs Free Energy 自由能定義與例句閱讀中譯中譯:定溫程序中系統的自由能變化量為焓變化量減去溫度乘以火商變化量。中譯中譯:自由能是可以提供用以作功的能量。The change in free energy of a system for a constant temperat
17、ure process is DG=DH-TDS Free energy is the energy available to do work.For a spontaneous process0000SDDDDDDDDDDDDsyssysunivsyssysunivsyssysunivsurrsysunivSTHSTHSTSTTHSSSSTHsyssurrDDSsyssysSTHGDDD18.5 Gibbs Free Energy 自由能定義與例句閱讀中譯中譯:定溫定壓下,以自由能變化量判定自發性與平衡的條件中譯中譯:自由能變化為負值,正反應為自發The conditions for spo
18、ntaneity and equilibrium at constant temperature and pressure in terms of DG DG 0The reaction is nonspontaneous.The reaction is spontaneous in the opposite direction.DG=0The system is at equilibrium.There is no net change.中譯中譯:自由能變化為正值,反應不自發,逆反應方向為自發中譯中譯:自由能變化為零,系統處於平衡狀態,無淨變化18.5 Gibbs Free Energy 自
19、由能定義與例句閱讀中譯中譯:標準反應自由能是一個發生於標準狀態下反應的自由能變化量,(也就是)標準狀態下的反應物轉化為標準狀態下的產物(的自由能變化量)。The standard free-energy of reaction is the free-energy change for a reaction when it occurs under standard state conditions,when reactants in their standard states are converted to products in their standard states.Convent
20、ions for Standard StatesGas1 atm pressureLiquidpure liquidSolidPure solidElementsDG=0Solution1 molar concentration18.5 Gibbs Free Energy 自由能定義與例句閱讀中譯中譯:一個化合物標準生成自由能,也就是該化合物由標準狀態下的元素形成該化合物時的自由能變化。is the standard free-energy of formation of a compound,that is the free-energy change that occurs when 1
21、mole of the compound is synthesized from its elements in their standard states.0GfD18.5 Gibbs Free Energy 自由能定義與例句閱讀中譯中譯:當焓與火商的變化量均為正值,僅有在溫度乘以商變化的結果遠大於涵變化量時自由能變化量才有可能為負值(自發),此一情況在高溫下較能符合。If both DH and DS are positive,then DG will be negative only when TDS term is greater in magnitude than DH.This c
22、ondition is met when T is large.D DG=D DH-TD DS18.5 Gibbs Free Energy 自由能定義與例句閱讀中譯中譯:當焓變化量為負而火商的變化量也為負值,僅有在溫度乘以商變化的結果小於焓變化量時自由能變化量才有可能為負值(自發),此一情況在低溫下較能符合。If DH is negative and DS is negative,then DG will be negative only when TDS term is smaller in magnitude than DH.This condition is met when T is
23、small.D DG=D DH-TD DS18.5 Gibbs Free Energy 自由能定義與例句閱讀中譯中譯:當焓變化量均為正值而火商的變化量為負值,無論溫度為何,自由能變化量恆為正值(不自發)。If DH is positive and DS is negative,DG will always be positive,regardless of temperature.中譯中譯:If DH is negative and DS is positive,then DG will always be negative regardless of temperature.D DG=D D
24、H-TD DSD DG=D DH-TD DS18.6 Free Energy and Chemical Equilibrium自由能與化學平衡w Reaction quotient (Q)w Equilibrium constant(K)Vocabulary and Phrase 字與詞反應商平衡常數18.6 Free Energy and Chemical Equilibrium自由能與化學平衡The larger the K is,the more negative DG0 is.KRT lnG0D中譯中譯:標準自由能負值越多時,平衡常數則越大。If DG0 0,there will be
25、 more reactants than products at equilibrium.中譯中譯:如果標準自由能變化量為負,平衡時產物的生成多於反應物。中譯中譯:如果標準自由能變化量為正,平衡時反應物會多於產物。KRT lnG0D18.7 Thermodynamics if Living System生物系統中的熱力學w Coupling reactionVocabulary and Phrase 字與詞耦合反應The principle of coupled reaction is based on a simple concept:We can use a thermodynamically favorable reaction to derive an unfavorable one.中譯中譯:耦合反應的原理建築在一個簡單的概念上:我們可以利用一個熱力學上有利的反應去驅動一個較不利於發生的反應。
