第二章 化学热力学基础
习题2-1 什么叫状态函数?什么叫广度性质?什么叫强度性质?
答:体系的性质,如物质的量、温度、体积、压力等,可以用来描述体系的状态。体系的性质是由体系的状态确定的,这些性质是状态的函数,称为状态函数。具有加和性的性质称为广度性质;不具有加和性的性质称为强度性质。
习题2-2 自发过程的特点是什么?
答:在孤立体系中,变化总是自发地向熵增加的方向进行,即向混乱度增加的方向进行。不做非体积功的封闭体系中,定温定压条件下,变化总是自发的向着自由能降低的方向进行。
习题2-3 什么叫混乱度?什么叫熵?它们有什么关系?
答:混乱度Ω是体系的微观状态数。熵S是量度混乱度的状态函数,S = k lnΩ
习题2-4 什么是自由能判据?它的应用条件是什么?
答:在定温定压不做非体积功条件下,自由能降低的过程可以自发进行;自由能不变的过程是可逆过程。自由能判据适用于封闭体系、定温定压过程。
θθ习题2-5 298K时6.5g液体苯的弹式量热计中完全燃烧,放热272.3kJ。求该反应的?rUm和?rHm。
解:C6H6(l)?15O2?6CO2(g)?3H2O(l) 2??(g)??0?15?6??1.5 2mM?6.5mol ???178θ?U?QV????rUm??272.3kJ?rU??3267.6kJ?molθθ?rHm??rUm???(g)RTθm?1
??3267.6?103?(?1.5)?8.314?298??3271.3?103J?mol?1??3271.3kJ?mol?1
习题2-6 298K、标准状态下HgO在开口容器中加热分解,若吸热22.7kJ可形成Hg(l)50.10 g,
θ求该反应的?rHm,若在密封的容器中反应,生成同样量的Hg(l)需吸热多少?
解: HgO(s)?Hg(l)?1O2(g)
2??(g)?0.5
0???mM?50.10mol ?1200.6
θ?rHm?Qp,m/??22.71/0.250?90.84kJ?molθθ?rUm??rHm???(g)RT?1
?90.84?103?0.5?8.314?298?89601J?mol?1?89.601kJ?mol?1
Qv?Qv,m???89.601?0.250?22.40kJ
习题2-7 已知298K、标准状态下 (1)Cu2O(s)+
1O2(g)?2CuO(s) 2θmol-1 ?rHm(1)= -146.02kJ·
θ(2)CuO(s)+Cu(s)? Cu2O(s) ?rHmmol-1 (2)= -11.30 kJ·
求(3)CuO(s)? Cu(s)+
1θO2(g)的?rHm 22解: ? CuO(s)? Cu(s)+1O2(g) (1)?(2)得(3)θθθ?ΔrHm(3)=ΔrHm(1)-ΔrHm(2)=-(-146.02)-(-11.30)=157.32kJ?mol
习题2-8 已知298K、标准状态下
(1)Fe2O3(s)+3CO(g)?2Fe(s)+3CO2(g)
θmol-1 ?rHm(1)= -24.77 kJ·
-1
(2)3Fe2O3(s)+CO(g)?2Fe3O4(s)+CO2(g)
θ ?rHmmol-1 (2)= -52.19 kJ·
(3)Fe3O4(s)+CO(g)?3FeO(s)+CO2(g)
θmol-1 ?rHm(3)=39.01 kJ·
θ求 (4)Fe(s)+CO2(g)?FeO(s)+CO(g)的?rHm。
解:
1??3?(1)?(2)?2?(3)?得(4) 6Fe ?s??CO2?g??FeO?s??CO?g?111θθθθ??rHm(4)???rHm(1)??rHm(2)??rHm(3)263111??(?24.77)?(?52.19)?(?39.01)
263?16.69kJ?mol?1
θ习题2-9 由?fHm的数据计算下列反应在298K、标准状态下的反应热?rHm。
θ(1)4NH3(g) + 5O2(g) ? 4NO(g) + 6H2O(l)
(2)8Al(s) + 3Fe3O4(s) ? 4Al2O3(s) + 9Fe(s) (3)CO(g) + H2O(g) ? CO2(g) + H2(g) 解:
θθ(1)?rHm???(B)ΔfHm(B)θθθ?4??fHm(NO,g)?6??fHm(H2O,l)?(?4)??fHm(NH3)
?4?90.25?6?(?285.84)?4?(?46.11)??1169.6kJ?mol?1θθ(2)?rHm???(B)?Hm(B)θθ?4??fHm(Al2O3,s)?(?3)??fHm(Fe3O4)
?4?(?1676)?3?(?1120.9)??3341.3kJ?mol?1θθ(3).?rHm???(B)ΔfHm(B)θθθ?1??fHm(CO2,g)?(?1)??fHm(CO,g)?(?1)??fHm(H2O,g)?(?393.51)?(?110.53)?(?241.82)??41.16kJ?mol?1θθ
习题2-10 由?cHm的数据计算下列反应在298K、标准状态下的反应热?rHm。 (1)C6H5COOH(s)+ H2(g)? C6H6(l)+ HCOOH(l) (2)HCOOH(l)+ CH3CHO(l)? CH3COOH(l)+HCHO(g) 解:
θθ(1)?rHm?-??(B)?cHm(B)θθθθ?-[-1??cHm(C6H5COOH,s)-1??cHm(H2,g)?1??cHm(C6H6,l)?1??cHm(HCOOH,l)]?-3223.87?(-285.84)?3267.54?254.64?9.47kJ?mo-1lθθ(2)?rHm?-??(B)?cHm(B)θθθθ?-[-1??cHm(HCOOH,l)-1??cHm(CH3CHO,l)?1??cHm(CH3COOH,l)?1??cHm(HCHO,g)]?-254.64?(-1166.37)?871.54?570.78?21.3kJ?mol-1
习题2-11 由葡萄糖的燃烧热和水及二氧化碳的生成热数据,求298K标准状态下葡萄糖的
θ。 ?fHm解: C6H12O6(s) + 6O2(g) ? 6CO2(g) + 6H2O(l)
θθ?cHm?-??(B)?fHm(B)θθθθ?fHm(C6H12O6,s)???cHm-[-6??cHm(CO2,g)?6??cHm(H2O,l)]
??(-2803.03)?6?(-393.51)?6?(?285.84)??1273.07kJ?mol-1
习题2-12 已知298K时,下列反应
BaCO3(s)? BaO(s)+ CO2(g)
θ/kJ·mol-1 ?fHmθ/J·K-1·mol-1 Smθ -1216.29 -548.10 112.13
θ-393.51 213.64
72.09
θ求298K时该反应的?rHm,?rSm和?rGm,以及该反应可自发进行的最低温度。 解:298K时
θθ?rHm???(B)ΔfHm(B)?(?548.10)?(?393.51)?(?1216.29)?274.68kJ?mol?1θθ?rSm???(B)Sm(B)
?72.09?213.64?112.13?173.60J?K?1?mol?1θθθ?rGm??rHm?T?rSm?274.68?103?298?173.60?222.95?103J?mol?1?222.95kJ?mol?1设反应最低温度为T,则
θθθ?T???rHm?T??T?rSm?T??rGmθm??rH?298K??T?rS?298K??0θm
274.68?103?T?173.60?0
T >1582K
习题2-13 由?fGm和Sm数据,计算下列反应在298K时的?rGm,?rSm和?rHm。 (1)Ca(OH)2(s) + CO2(g) ? CaCO3(g) + H2O(l) (2)N2(g) + 3H2(g) ?2NH3(g)
(3)2H2S(g) + 3O2(g) ?2SO2(g) + 2H2O(l) 解:
θθ(1)?rGm???(B)ΔfGm(B)θθθθθ?1?(?1128.8)?1?(?237.19)?1?(?898.56)?1?(?394.36)??73.07kJ?mol?1?rS???(B)S(B)?1?92.88?1?69.94?1?83.39?1?213.64??134.21J.K?1?mol?1θθθ?rHm??rGm?T??rSm??73.07?103?298?(?134.15)θmθm
??113.06?10J?mol??113.06kJ?molθθ(2)?rGm???(B)ΔfGm(B)3?1?1
?2?(?16.50)??33.0kJ?mol?1θθ?rSm???(B)Sm(B)
2?192.3?1?191.5?3?130.57??198.61J?K?1?mol?1
θθθ?rHm??rGm?T?rSm??33.0?103?298?(?198.61)??92.19?10J?mol??92.19kJ?mol?1θθ(3)?rGm???(B)ΔfGm(B)3?1
?2?(?300.19)?2?(?237.19)?2?(?33.6)??1007.56kJ?mol?1θ?rSm???(B)Sθm(B)2?248.1?2?69.94?2?205.7?3?205.03??390.41J?K?1?mol?1θθθ?rHm??rGm?T?rSm
??1007.56?103?298?(?390.41)??1123.90?10?3J?mol?1??1123.90kJ?mol?1
习题2-14 Calculate the standard molar enthalpy of formation for N2O5(g) from the following date:
(1)2NO(g) + O2(g) ?2NO2(g) (2)4NO2(g) + O2(g) ?2N2O5(g) (3)N2(g) + O2(g) ?2NO(g)
θ ?rHmmol-1 (3) = -180.5kJ·
θmol-1 ?rHm(1) = -114.1 kJ·
θ ?rHmmol-1 (2= -110.2kJ·
解: 0.5?(2)+(1)+(3)得(4) N2(g) + 2.5O2(g) ? N2O5(g)
θθΔfHm(N2O5,g)=ΔrHm(4)θθθ?0.5?ΔfHm(2)?ΔfHm(1)?ΔfHm(3)=0.5?(-110.2)+(-114.1)+(-180.5)=-349.7kJ?mol-1
习题2-15 A sample of D-ribose (C5H10O5) with mass 0.727g was weighed into a calorimeter and then ignited in presence of excess Oxygen. The temperature rose by 0.910K when the sample was
combusted. In a separate experiment in the same calorimeter the combustion of 0.825g of benzoic
?acid(C7H6O2), for which the ΔcUm?3251kJ?mol?1, gave a temperature rise of 1.940K. Calculate the
θθ and ?rHm of D-ribose combusted. ?rUm解: 0.825g苯甲酸燃烧,仪器温度上升1.940K, 设水当量(仪器温度上升1K所需的热量)为Q,
θQV??ΔrUmQ??ΔTΔTθm?ΔcUm ?M?ΔT
0.825?3251?103 ?
122?1.940 = 11.33?103J?K-1
0.727g D-核酸燃烧,仪器温度上升0.910K,
C5H10O5(s) + 5O2 (g) ? 5CO2(g) + 5H2O(l)
θ??ΔrUmθm?ΔcUm?
M?ΔTQ?ΔT3θ0.727?ΔcUm11.33?10?
150?0.910θθΔrUm?ΔcUm?2127kJ?mol?1 θθθΔrHm?ΔrUm????g?RT?ΔrUm
?2127kJ?mol?1
0.825?3251?103 ?
122?1.940 = 11.33?103J?K-1
0.727g D-核酸燃烧,仪器温度上升0.910K,
C5H10O5(s) + 5O2 (g) ? 5CO2(g) + 5H2O(l)
θ??ΔrUmθm?ΔcUm?
M?ΔTQ?ΔT3θ0.727?ΔcUm11.33?10?
150?0.910θθΔrUm?ΔcUm?2127kJ?mol?1 θθθΔrHm?ΔrUm????g?RT?ΔrUm
?2127kJ?mol?1
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