西华大学物理化学复习题(1)

计算题

1、 在25℃将1mol的氧气(设为理想气体)从1个标准大气压p?,恒温可逆压缩到6个标准大气

压6p?

求此过程的功W,系统和环境交换的热量Q,氧气的?U,?H,?A,?G,?S,和环境的熵变?Ssyssur及总熵变?Stotal

。解:氧气被设为理想气体且过程恒温可逆。?U??U?Q?W?QR?WR?0?QR??WRV2V2?0(1分),?H?0

?RTlnp2p1?RTln6pp?WR???pdV???V1V1RTVdV?RTlnV1V2

?WR?RTln6?8.314?298.15ln6?4.4414?10J33

?6pp???QR??4.4414?10J?dA??SdT?PdV,等温,?dA??PdV??A?W?4.4414?10J3 ?dG??SdT?VdP,等温,?dG?VdP??G?3VdP

?G?RTln6?8.314?298.15ln6?4.4414?10JQRT?1

?Stotal??Ssys??Ssur?0J?K?1?Ssys??14.8967J?K?Ssur??QRT??14.8967J?K?1

10、已知P?下CPm,A(s),CPm,B(g)?1.1?4.8?10?3T?1.2?10?6T(J/mol/K)2

?6.26?2.746?10?3T?0.77?10?6T(J/mol/K)2

CPm,C(g)?6.6?1.2?10?3T(J/mol/K)

计算在P下在什么温度附近反应?A(s)?12B(g)?C(g)的?rH?m与温度无关?

解:若恒压下反应热与温度无关,则

???rHm? ?CPm?CPm,C(g)?1CPm,B(g)?CPm,A(s)?0?0??C?0Pm??2??T?P1?3?3?62??? ???6.6?1.2?10T??2?6.26?2.746?10T?0.77?10T??3?62?T1?2550K,T????1.1?4.8?10T?1.2?10T??0

2?586K

由于2550K温度太高了,反应一般不安排在此温度下进行,故在586K附近反应热与温度无关

3、某气体状态方程为PVm?RT?bP(b?0),该气体绝热向真空膨胀后温度如何变化? 解:Q?0,W?0?dUm?0??Um???Um???Um?dUm???dVm?CVmdT???dVm?dT???V?V??T?Vmm?Tm?T??

??Um???Sm?dUm?TdSm?PdVm????T???P??Vm?T??Vm?T

??Um???Sm???P?????T???P??T???P??T?Vm??Vm?T??Vm?T??Um?RRT ??P????P?0???????T?VmVm?b??Vm?TVm?b

??Um? dUm?0?CVmdT???dVm?CVmdT?0dVm?dT?0??Vm?T

2、根据下列数据计算反应H2S(g)?32O2(g)?H2O(g)?SO2?在, p(g)??298.15K时的反应焓变?rHm(298.15K)值及p,

?1000K的反应焓变?rHm(1000K)值。已知:?fHm(H2O(g),298.15K)??242.9KJ?mol??1

?fHm(SO2(g),298.15K)??296.0KJ?mol?fHm(H2S(g),298.15K)??20.0KJ?mol?3??1

??1

?62?1CPm(H2O(g))?30.204?9.933?10T?1.117?10TJ?mol?3?62?K?9?1

?1CPm(SO2(g))?25.719?57.907?10T?38.087?10T?8.607?10TJ?mol3?K?1

CPm(H2S(g))?26.715?23.866?10T?5.06?10TJ?mol?3?62?3?62?1?K?1

?K?1CPm(O2(g))?25.501?13.610?10T?4.286?10TJ?mol?1

?1解:

?rHm(298.15K)??242.9?296.0?(?20.0)??32?0??518.9KJ?mol???518900J?mol?1

????rHm??????CPm?d?rHm??CPmdT?T??P

1000?rHm(10K00)1000??rHm(298.15K)??d?rHm??298.15?CPmdT

?rHm(1000K)??rHm(298.15K)?1000???298.15?CPmdT

?rH(1000K)??rH(298.15K)??m?m?298.15?CPmdT

?1?CPm?CPm(H2O(g))?CPm(SO2(g))?32CPm(O2(g))?CPm(H2S(g))?CPm??9.044?23.559?10T?25.481?10T?8.607?10TJ?mol1000???3?62?93?K?1

?rHm(1000K)??rHm(298.15K)??298.15?CPmdT

?rHm(1000K)??520650J?mol??1

2、 每只滑冰鞋与冰接触面积约0.0762?0.0000245m2,若滑冰人重60Kg, 按两只脚站立记,

试问施加于冰上的压强是多少

3Pa?该压强下冰的熔点为多少K?已知:?(da an T2=262.2K)

dPdT??fusfusHm?6003.7J/mol ,

3 冰的密度0.92g/cm,水的密度1.00g/cm。解:P?60?9.81(N)2S(cm)2 ?157560375PaHmT?Vfusm?P2?P1???fusHmVfusmlnT2T1

lnT2?

(P2?P1)?fusVm?fusHm?lnT1 lnT2?(P2?P1)Vm,H2O(l)?Vm,H2O(s)?fus??Hm?ln273.2

???4、根据?fHm(298K)和Sm(298K)计算反应的?rGm(298K),

?rHm(298K),?rSm(298K)并判断那些反应在298K,P下能自发?

???(3)CH4(g)?12O2(g)?CH3OH(l) 已知298K,标准压力下的数据如下表:

02845.?/?1?2?285840?/KJmol??Jmol?解:(1)、?rHm29(8)K2845.?0?

?rSm(298K)?69.94?130.59?1?205.03?-163.1650J/mol/K2?5? 自发。

?rGm(298K)??285840?298?(-163.1650)?-2.3722?10J/mol?0(2)、

?rHm29(8)2K?3912.?0??0????Jmol

?-16824.0Km/Jol?1846240/???rSm(298K)?2?184.81?130.59?222.95?16.0800J/mol/K?rGm(298K)??1846240?298?(16.0800)?-1.8510?10J/mol?0自发。

?6?9(8)K25378.?(8748).?(3)、?rHm20????J?1?2mol

??17623.0Km/Jol163720/??rSm(298K)?126.8?186.19?1?205.03?-161.9050J/mol/K 2?rGm(298K)??1637220?298?(?161.9050)?-1.5890?10J/mol?0?6自发。

5.假设气体为理想气体,在P?,温度673K,下面的反应

?rGm(673K)?24012J/mol?673K,P?:12N2(g)?32H2(g)?NH3(g)的

?rGm(673K)?24012J/mol??0为非自发反应

,请问,若温度不变,采用加压方法应该加压到多高压力才自发呢? 解:设计如下途径673K,P??G1??rGm(673K)?24012J/mol?:12N2(g)?32H2(g)?

NH3(g)

??G3?rGm(P,673K)??J/mol32673K,P:?G3??12N2(g)?H2(g)?PP?NH3(g) ?G1??PPVdP???PP?2RTPPdP?2RTln?

P?PP?VdP??PP?1?RTPdP??RTln

?rGm(673K)??G1??rGm(P,673K)??G3

?rGm(P,673K)??rGm(673K)?(?G1??G3)

??rGm(P,673K)?24012?8.314?673lnPP?PP?(J/mol)

if?rGm(P,673K)?0??73.0718?P?73.0718P?

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