物理化學(xué)電子教案—第六章-資料下載頁
2025-10-08 14:11本頁面
【導(dǎo)讀】化學(xué)反應(yīng)的方向與限度。為什么化學(xué)反應(yīng)通常不能進(jìn)行到底。等溫、等壓條件下，公式表示有限體系中發(fā)生微小的變化；這時(shí)各物質(zhì)的濃度基本不變，化學(xué)勢。用判斷都是等效的。用判斷，這相當(dāng)于圖上曲線的斜率，因?yàn)槭俏⑿∽兓?，反?yīng)進(jìn)度處于0~1mol之間。反應(yīng)自發(fā)向左進(jìn)行，趨向平衡。于存在混合吉布斯自由能的緣故。何形式的混合，才可以使反應(yīng)從R點(diǎn)直接到達(dá)S點(diǎn)。先引進(jìn)了化學(xué)反應(yīng)親和勢的概念。他定義化學(xué)親和勢A為：。A是狀態(tài)函數(shù)，體系的強(qiáng)度性質(zhì)。任何氣體B化學(xué)勢的表達(dá)式。將化學(xué)勢表示式代入的計(jì)算式，得：pTG,mr)(?多種方法計(jì)算，從而可得的值。稱為熱力學(xué)平衡常數(shù)，它僅是溫度的函數(shù)。數(shù)值上等于平衡時(shí)的“逸度商”，是量綱為1的量，
【正文】 $將兩個(gè)方程聯(lián)立，解得 。 的轉(zhuǎn)化率為 ? 。 0. 04 8 , 0. 00 9xy??3CH Cl?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 反應(yīng)的耦合 耦合反應(yīng)（ coupling reaction） 設(shè)體系中發(fā)生兩個(gè)化學(xué)反應(yīng)，若一個(gè)反應(yīng)的產(chǎn)物在另一個(gè)反應(yīng)中是反應(yīng)物之一，則這兩個(gè)反應(yīng)稱為耦合反應(yīng)。例如： ( 1 ) A B C D( 2) C E F H? ? ?? ? ? 利用 值很負(fù)的反應(yīng)，將 值負(fù)值絕對值較小甚至略大于零的反應(yīng)帶動(dòng)起來。 rmG? $rmG? $?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 耦合反應(yīng)的用途： 例如：在 K時(shí)： 12 2 4 2 r m , 1 ( 1) T iO ( s) 2C l ( g) T iCl ( l ) O ( g) 1 61 .9 4 k J m ol G? ? ? ? ? ?$反應(yīng) (1)、 (2)耦合，使反應(yīng) (3)得以順利進(jìn)行。 12 2 r m , 2( 2) C( s) O ( g) CO ( g) 39 4. 38 k J m olG? ? ? ? ? ?$1r m2 2 4 2,3 ( 3) T i O ( s) C ( s) 2C l ( g) T i C l ( l ) C O ( g) 232. 44 kJ m ol G ????????則$?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 近似計(jì)算 1． 的估算 rm()GT? $r( 2 9 8 .1 5 K )T ?rrr m r m r mr m r m rr m r m r( ) ( ) ( )( ) ( ) d( ) ( ) dTpTTpTG T H T T S TH T H T C TCS T S T TT? ? ? ? ?? ? ? ? ??? ? ? ???$ $ $$$$$當(dāng) 不大，或不要作精確計(jì)算時(shí)，設(shè) ，則： pC? 0pC??r m r m r r m r( ) ( ) ( ) G T H T T S T a bT? ? ? ? ? ??$ $ $ 這里實(shí)際上設(shè)焓和熵變化值與溫度無關(guān)，從 K的表值求出任意溫度時(shí)的 值。 rmG? $?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 近似計(jì)算 2．估計(jì)反應(yīng)的有利溫度 r m r m r m( ) ( ) ( )G T H T T S T? ? ? ? ?$ $ $ 通常焓變與熵變在化學(xué)反應(yīng)中的符號(hào)是相同的。要使反應(yīng)順利進(jìn)行，則 越小越好。 rm()GT? $r m r m( 1 ) ( ) 0 , ( ) 0H T S T? ? ? ?$$提高溫度對反應(yīng)有利。 r m r m( 2 ) ( ) 0 , ( ) 0H T S T? ? ? ?$$降低溫度對反應(yīng)有利。 ?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 轉(zhuǎn)折溫度 通常將 時(shí)的溫度稱為轉(zhuǎn)折溫度，意味著反應(yīng)方向的變化。這個(gè)溫度可以用 K時(shí)的 和 值進(jìn)行近似估算。 rm ( ) 0GT??$rmH? $ rmS? $r m rr m r()(()HTTST???轉(zhuǎn)折）$$?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 JACOBUS HENRICUS VAN’T HOFF JACOBUS HENRICUS VAN’T HOFF (18521911) Dutch physical chemist,received the first Nobel Prize in chemistry in 1901 for “the discovery of the laws of chemical dynamics and of osmotic pressure.” Van’t Hoff was one of the early developers of the laws of chemical kiics,developing mehtods for determining the order of a reaction。he deduced the relation between temperature and the equilbrium constant of a chemical reaction. ?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 JACOBUS HENRICUS VAN’T HOFF In 1874, van’t Hoff (and also . Le Bel, independently) proposed what must be considered one of the most important ideas in the history of chemistry, namely the tetrahedral carbon bond. Van’t Hoff carried Pasteur’s ideas on asymmetry to the molecular level , and asymmetry required bonds tetrahedrally distributed about a central carbon atom. Structural anic chemistry was born. ?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 JOHN DALTON JOHN DALTON (17661844) English chemist, physicist, and meteorologist, is considered by many to be the “father of the atomic theory of matter,although grandfather is perhaps a more he suffered. In 1803, he published his paper “Absorption of Gases by Water and Other Liquids,” in which he presented what is now known as Dalton’s law of partial pressures. ?上一內(nèi)容 ?下一內(nèi)容 ?回主目錄 ?返回 JOHN DALTON He was led to his theory of atomism by his studies of gases. In one of his papers published in 1805, he said, “Why does not water admit its bulk of every kind of gas alike?…The circumstance depends on the weight and number of the ultimate particles of the several gases.” John Dalton was led to the atom by reflecting that different gases had different values of the Henry’s law constant.
教學(xué)課件相關(guān)推薦
鄂ICP備17016276號(hào)-1