簡介:湖北民院化環(huán)學院天大教材熱力學第二定律課外習題解答103熱力學第二定律習題解答熱力學第二定律習題解答【35】高溫熱源溫度T1600K,低溫熱源溫度T2300K。今有120KJ的熱直接從高溫熱源傳給低溫熱源,求此過程兩熱源的總熵變ΔS。解題設過程本為不可逆過程,但可假設在T1和T2之間有無數(shù)個熱源,相鄰熱源間的溫差僅為DT,將系統(tǒng)逐個與每個人熱源接觸并達到熱平衡,結果是熱從高溫熱源可逆地傳到了低溫熱源。33111211201012010JKJK600300200JKSSS?????????????????【39】始態(tài)為T1300K,P1200KPA的某雙原子理想氣體1MOL,經(jīng)下列不同途徑變化到T2300K,P2100KPA的末態(tài)。求各不同途徑各步驟的Q、ΔS。(1)恒溫可逆膨脹。(2)先恒容冷卻至使壓力降至100KPA,再恒壓加熱至T2。(3)先絕熱可逆膨脹到使壓力降至100KPA,再恒壓加熱至T2。解(1)對于理想氣體恒溫可逆膨脹,ΔU0,于是QW21112DLNVVPPVNRTP??200183145300LNJ1729J100??????????1111729JK576JK300QST????????(2)設恒容冷卻至100KPA時,溫度為T。211100300K150K200PTTP????對于雙原子理想氣體,CV,M25R,CP,M35R,則Q1NCV,M(150K300K)12583145150J3118KJQ2NCP,M(300K150K)13583145150J4365KJQQ1Q231184365KJ1247KJ111,1150LN12583145LNJK1441JK300VMTSNCT??????????????????湖北民院化環(huán)學院天大教材熱力學第二定律課外習題解答21122,300LN13583145LNJK2017JK150PMTSNCT?????????????????111214412017JK576JKSSS?????????????(3),,/35/2514PMVMCCRR????設絕熱可逆膨脹到100KPA時,溫度為T,則111414112200300K2461K100PTTP???????????????????Q10Q2NCP,M300K2461K135831453002461J1568KJQQ1Q21568KJ10S??1122,300LN13583145LNJK576JK2461PMTSNCT?????????????????11120576JK576KJMOLSSS????????????【311】2MOL雙原子理想氣體從始態(tài)300K,50DM3,先恒容加熱至400K,再恒壓加熱使體積增大到100DM3,求整個過程的Q,W,△U,△H,△S。解題設過程如下圖所示。2MOLT1300KV150DM3P12MOLT2400KV250DM3P22MOLT3V3100DM3P3P2恒容加熱(1)恒壓加熱(2)系統(tǒng)終態(tài)壓力23232283145400PA133032PA5010NRTPPV???????系統(tǒng)終態(tài)溫度333313303210010K800K283145PVTNR???????雙原子理想氣體,CV,M25R,CP,M35R湖北民院化環(huán)學院天大教材熱力學第二定律課外習題解答53111029815256712JMOL170731KJMOLRMRMRMGHTS?????????????????(247269)(2)11137168205072394359KJMOL170743KJMOLRMBFMBGGB??????????????????(2)(3)整個過程可表示為CH4GCO2GP1CH4150KPAP1CO2150KPACOGH2GP4CO50KPAP4H250KPACH4GCO2GP1CH4100KPAP1CO2100KPACOGH2GP1CO100KPAP1H2100KPA123過程(1)為恒溫變壓過程2422,1,14,121412311113CHCOCHCOLNLNCHCO10010283145LNJMOLK6743JMOLK15010MMMPPSSSRRPP?????????????????????????????過程(2)為標準態(tài)下的化學反應O11,2BBB256712JMOLKMMSS?????????過程(3)為恒溫變壓過程442,3,3,32332311113COH2CO2H2LN2LNCOH5010483145LNJMOLK23053JMOLK15010MMMPPSSSRRPP?????????????????????????????整個過程11,1,2,311674325671223053JMOLK286507JMOLKRMMMMSSSS???????????????????對于理想氣體,H?僅是溫度的函數(shù),整個過程是恒溫過程。湖北民院化環(huán)學院天大教材熱力學第二定律課外習題解答6O1247269KJMOLRMRMHH??????O3112472692981528650810KJMOL161860KJMOLRMRMRMGHTS???????????????【344】證明(1),M,MPVPVNCNCTTDSDPDVTPTV??????????????????(2)對理想氣體,M,MLNLNVPDSNCDPNCDV??證(1)若SS(P,V)則PVPPVVSSSTSTDSDPDVDPDVPVTPTV????????????????????????????????????????????????????由VCDSDTT?知,VVCSTT?????????由PCDSDTT?知,PPCSTT?????????所以,,M,MPVPVNCNCTTDSDPDVTPTV??????????????????(2)對于理想氣體,PVNRT,VPPVTTPTTNRPVNRV????????????????????故PPVVPVCCCCTTTTDSDPDVDPDVTPTVTPTV????????????????????LNLNPVVPCCDPDVCDPCDVPV????
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