物理化学期中考试试卷来下

5.降低

6.不能确定, >0, >0, <0, <0, <0, >0 7. ?Siso 8.-187J

二、选择题(30×1=30分)

1~5 ACBCB 6~10 CDDBA 11~15 DDAAA 16~20 BBBAD 21~25 BBDBA 26~30 DACDA

三、计算题

1. (本题6分)解:(1)环丙烷的生成反应为:

? 3C(石)+3H2?C3H6 该反应的热效应即为环丙烷的生成热?fHm

?????fHm??rHm????B?CHm?3?(?393.8)?3?(?285.84)?2092?53.08KJ?mol?1

(2)异构化反应为:C3H6?CH3CH?CH2

?????fHm???rHm??fHm(丙烯)??fHm(丙烷)?20.5?53.08??32.58KJ?mol?1

2. (本题15分)解:(1)恒温可逆: ?U??H?0 W??Q??pdV?nRTln?p2300?1?8.314?298ln?2722J,Q??2722J p1100?S?nRlnp1100?1?8.314?ln??9.13J?K?1 p2300 ?A??U?T?S??T?S??Q?2722J ?G??H?T?S??T?S??Q?2722J (2) 绝热可逆压缩 Q?0,?S?0 (p11??T1001)?(2)??()?p2T13001.4?(T2)2981.4?T2?408K

?U?nCV,m(T2?T1)?1?2.5?8.314?(408?298)?2286J W??U?2286J

?H?nCp,m(T2?T1)?1?3.5?8.314?(408?298)?3201J

?G?? JH?S?T3?201?205?(408?298?)?K19 ?A?? JU?S?T2?286?205?(408?298?)?K20 (3) 绝热不可逆压缩 Q?0,?U?W 即:nCV,m(T2?T1)??pamb(V2?V1)??nR[T2?T1p2] p12.5R(T2?298)??R(T2?298?300)?T2?468.2K

100?U?nCV,m(T2?T1)?1?2.5?8.314?(468.2?298)?3540J

W??U?3540J

?H?nCp,m(T2?T1)?1?3.5?8.314?(468.2?298)?4955J

?S?nRlnp1T100468.2?nCp,mln2?1?8.314ln?1?3.5?8.314ln?4.02J?K?1 p2T1300298?S2?S1??S?205?4.02?209.02J?K?1

?G??H??(TS)??H?(T2S2?T1S1)?4955?(468.2?209.02?298?205)??31.84KJ?A??U??(TS)??U?(T2S2?T1S1)?3540?(468.2?209.02?298?205)??33.24KJ3(本题8分) .解:设计过程如下:

H2O(L),100KPa 270.2k △G1 H2O(L),489,16Pa 270.2k △G H2O(S) 100KPa 270.2k △G5 H2O(S),475.12Pa 270.2k △G2 △G3 H2O(g),489.16Pa 270.2k △G4 H2O(g),475.12Pa 270.2k

?G??G1??G2??G?3?G4??G5,其中?G1?0;?G5?0;

?G2?0;?G4?0??G??G3?nRTln

p4475.12?1?8.314?270.2ln??65.4J<0 p3489.16??Ssys<0,又

故上述过程为自发过程,此过程系统的有序度是增加的。

?Stotal>0,

?Stotal??Ssys??Samb 4.

(本题8分)

>0;

??Samb>0.

解:(1)因为等温且恒容故

W?0,?U?Q

1CO?O2?CO2 故其反应热为:

2???rHm??fHm(CO2)??fHm(CO)??393.51?110.52??283KJ

?rUm??rHm??(PV)??rHm??ngRT??283?0.5?8.314?298?10??281.8KJ?Q??rU??281.8KJ

?3

(2)因为绝热恒容

?Q??rU?0

1△U

T?298K:CO?O2?CO2,T 设产物的温度为T 12△rU △U2

T1=298K ;CO2 依题意:W?0,Q?0,?U?0 要求?H,则必须先求终态温度T

'?U??rU??U2??rU?nCV,m,CO2(T?T1)?0

即:?281.8?1000?46.5?(T?298)?0

?T?6357K

?rHm??rUm??(PV)??(PV)?n产RT-n反RT1?8.314?(6357-1.5?298)?49.14KJ5. (本题12分)

解:由于活塞是理想的,故可将右侧气体看成是一个绝热可逆压缩过程 根据:Tp?1???const

0.4101.3?1.4?298.2?()?363.5K

202.6pT2?T0(0)p21???p0V0101.3?103?0.02n???0.817mol

RT08.314?298.2(1)W?nCV,m(T2?T0)?0.817?20.9?(363.5?298.2)?1115J (2) 右侧气体的终态温度 T2?363.5K (3)

V2??nRT2P2V0=0.02m3 V0,T0,p0

T0?298.2K p0?101.3Kpa 0.817?8.314?363.5?12.2dm3

202.6T?298.2Kp?101.3KpaT?298.2Kp?101.3Kpa且此时p1?p2?202.6KPa

p1V1202.6?103?27.8?10?3?T1???829.2KnR0.817?8.314

(4) 因为绝热,故对整个系统Q=0

??U1?nCV,m(T1?T0)?0.817?20.9?(829.2?298.2)?9067J

对于右侧为绝热,故:

W2??U2?nCV,m(T2?T0)?0.817?20.9?(363.5?298.2)?1115J

对于整个系统: ?U?Q?Q1?Q2?Q1??U1??U2=9067+1115=10182J 四、证明题(本题5分)

?CV ??U??U证:()T?[()V]T?[()T]V

?V?V?T?T?V(?U?p)T?T()V?p?V?T

?CV??p?2p?p?p?2p?()T?[T()V?p]?T(2)V?()V?()V?T(2)V

?V?T?T?T?T?T?T

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