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1、第一章 習(xí)題解答
1. (1) Q=DU-W=200-160=40 kJ
(2) DU=Q+W=260-100=160 kJ
2. \W= -pDV= -R
3. (1) W= -pDV= -p(Vg–Vl)? -pVg= -nRT= -1′8.314′373.15= -3102 J
(2) W= -pDV= -p(Vs–Vl)
4. 在壓力p和房間容積V恒定時,提高溫度,部分空氣溢出室外,因此室內(nèi)氣體量n是溫度的函數(shù),。
5. (1) 恒溫可逆膨脹
(2) 真空膨脹 W = 0
(3) 恒外壓膨脹 W = -p外(V2–V3) =
2、
= -2327 J
(4) 二次膨脹 W=W1 + W2
以上結(jié)果表明,功與具體過程有關(guān),不是狀態(tài)函數(shù)。
6. (1) 理想氣體為系統(tǒng),等壓過程, Q=DH>0
(2) 電熱絲+理想氣體為系統(tǒng),等壓過程,Q=0,DU=W¢>0,DH=DU+D(pV)>0
7. DH=n×DHm,汽化=40670 J
DU=DH–D(pV)=DH–p(Vg-Vl)=40670–101325(30200–1880)′10-6
=40670–3058=37611 J
8.
過程
Q
W
DU
DH
(1)理想氣體自由膨脹
0
0
0
3、0
(2)理想氣體恒溫可逆膨脹
+
–
0
0
(3)理想氣體節(jié)流膨脹
0
0
0
0
(4)理想氣體絕熱恒外壓膨脹
0
–
–
–
(5)水蒸氣通過蒸氣機(jī)對外做功后復(fù)原,以水蒸氣為系統(tǒng)
+
–
0
0
(6)水(1 atm,0°C)? 冰(1atm,0°C)
–
–或?0
–
–
(7)剛性容器中石磨燃燒,整體為系統(tǒng)
0
0
0
+
9. Cp,m=29.07–0.836′103T+2.01′10-6T2
(1) Qp=DH
=20349–380+625=20.62 kJ
(2) QV=DU=DH–D(pV)=DH
4、–(p2V2–p1V1) =DH–nR(T2–T1)
=20.62–R(1000-300)′10-3 =14.80 kJ
10.(1)等溫可逆膨脹
DU =DH = 0
Q = -W
(2)等溫恒外壓膨脹
DU =DH =0
Q = -W = p2 (V2–V1) = p2V2–p2V1= p1V1–p2V1= (p1–p2)V1
=(506.6-101.3)′103′2′10-3 = 810 J
11. (1)常壓蒸發(fā):Q=DH= 40.7 kJ W= -p(Vg–Vl)? -pVg? -RT= -8.314′373= -3.1 kJ
5、DU=Q+W=37.6 kJ
(2) 真空蒸發(fā):DH=40.7 kJ W=0 DU =Q=37.6 kJ
12.
(1) p1T1=p2T2
(2) DU=nCV,m(T2–T1)=
DH=nCp,m(T2–T1)=
(3) 以T為積分變量求算:
pT=C(常數(shù))
也可以用p或V為積分變量進(jìn)行求算。
13.DU=nCV,m(T2–T1)=20.92′(370–300)=1464 J
DH=nCp,m(T2–T1)=(20.92+R)′(370–300)=2046 J
始態(tài)體積 體積變化:
壓力
6、W=W1+W2= -p2(V2–V1)+0= -821554′(0.003026–0.0246)= 17724 J
Q=DU -W=1464–17724=–16260 J
14. (1) DH=Cp,m(T2–T1) T2=373.8 K
p2=0.684′105 Pa
DU= CV,m(T2–T1) J
W=DU–Q=1255–1674=–419 J
(2)
狀態(tài)函數(shù)變化同上 DU=1255 J DH=2092 J
W=W1=–8.314′273.2×ln2=–1574 J
Q=DU–W=1255+1574 = 2829 J
15.
7、雙原子分子
W=DU=nCV,m(T2–T1)
16. (1)等溫可逆膨脹
DU =DH = 0
Q = W
(2)絕熱可逆膨脹
Cp.m=20.79 CV.m= Cp.m-R=12.476
TVg-1=常數(shù)
Q =0
DU=W=nCV,m(T2–T1)=12.476′(160.06–273.15)= -1411 J
DH=nCp,m(T2–T1)= 20.79′(160.06–273.15)= -2351 J
17. (1)
(2) DU=nCV,m(T2–T1)=0.1755′(28
8、.8–R) ′(224.9–298)= -263 J
DH=nCp,m(T2–T1)=0.1755′28.8 ′(224.9–298))= -369 J
18. 設(shè)物質(zhì)量為1mol
始態(tài)溫度: K
求終態(tài)溫度: K
J
J
Q=0 W=DU= -1779 J
若設(shè)物質(zhì)量為n mol,可如下計(jì)算:
始態(tài)溫度, 終態(tài)溫度
在計(jì)算DU、DH、W時n可消去,得相同的結(jié)果。
19. 證明 U=H–pV
20. 證明 (1)
H=f(T,p)
V不變,對T求導(dǎo) 代入(1)
21. 發(fā)酵反應(yīng) C6H12O6(s)
9、 ?? 2C2H5OH(l) + 2CO2(g) Dn=2
DU=DH-DnRT= -67.8 -2R′298′10-3 = -72.76 kJ×mol-1
22. nQV+CDT=0
QV =–4807200 J
C7H16(l) + 11O2(g) = 8H2O(l) + 7CO2(g) Dn =–4
DcHm = QV + DnRT =–4807200–4R′298 = –4817100 J×mol–1 =–4817.1 kJ×mol-1
23.(1) 2H2S(g)+SO2(g) = 8H2O(l) + 3S(斜方) Dn =–3 QV =–22
10、3.8 kJ
DrHm = QV + DnRT = –223.8 + (–3)RT′10-3 = –231.2 kJ
(2) 2C(石墨) + O2(g) = 2CO(g) Dn = 1 QV =–231.3 kJ
DrHm = QV + DnRT = –231.3 +RT′10–3 = –228.8 kJ
(3) H2(g)+Cl2(g) = 2HCl (g) Dn =0 QV =–184 kJ
DrHm = QV =–184 kJ
24. (1) x=4 mol (2) x=2 mol (3) x=8 mol
25. 2NaC
11、l(s) + H2SO4(l) = Na2SO4(s) + 2HCl(g)
DfHOm(kJ×mol-1) –411 –811.3 –1383 –92.3
DrHOm=S(nDfHOm)產(chǎn)物–S(nDfHOm)反應(yīng)物
= (–1383–2′92.3)–(–811.3–2′411) = 65.7 kJ×mol-1
DrUOm =DrH°m–DnRT=65.7–2RT′10-3=60.7 kJ×mol-1
26.生成反應(yīng) 7C(s) + 3H2(g) + O2 (g) = C6H5COOH(l)
DcHOm(kJ× mol-1) –394 –286 –323
12、0
DrHOm=S(nDcHOm) 反應(yīng)物–S(nDcHOm) 產(chǎn)物
= [7′(–394) + 3′(–286)] – (–3230)= –386 kJ×mol-1
27. 反應(yīng) C(石墨) ? C(金剛石)
DcHOm(kJ×mol-1) –393.5 –395.4
DrHOm=DcHOm,石墨–DcHOm,金剛石 =–393.5–(–395.4)=1.9 kJ×mol-1
28. 3C2H2 (g) = C6H6 (l)
DfHOm (kJ×mol-1) 226.73 49.04
DcHOm (kJ×mol-1) –1299
13、.6 –3267.5
由生成熱數(shù)據(jù)計(jì)算: DrHOm=49.04–3′226.73=–631.15 kJ×mol-1
DrUOm=DrHOm–DnRT=–631.15+3′8.314′298.2′10-3= -623.71 kJ×mol-1
由燃燒熱數(shù)據(jù)計(jì)算: DrHOm=3′(–1299.6)–(–3267.5) =–631.3 kJ×mol-1
DrUOm=DrHOm–DnRT=–631.3+3′8.314′298.2′10-3= -623.86 kJ×mol-1
29. 反應(yīng) KCl(s) ? K+(aq, ¥) + Cl-(aq, ¥)
D
14、fHOm(kJ×mol-1) –435.87 ? –167.44 DrHOm=17.18 kJ×mol-1
DrHOm=S(nDfHOm)產(chǎn)物–S(nDfHOm)反應(yīng)物
17.18=[DfHOm (K+,aq, ¥)–167.44]–(–435.87) DfHOm (K+,aq, ¥)=–251.25 kJ×mol-1
30. 生成反應(yīng) H2(g) + 0.5O2(g) = H2O(g) DrHOm,298=–285.83 kJ×mol-1
Cp,m(J×K-1×mol-1) 28.824 29.355 75.291
DCp=75.291–(
15、28.824+0.5′29.355)=31.79 J×K-1
=–285.83+31.79′(373–298)′10-3 =–283.45 kJ×mol-1
31. 反應(yīng)N2(g) + 3H2(g) = 2NH3(g) DrHOm,298=–92.88 kJ×mol-1
a
b′103
c′107
N2(g)
26.98
5.912
–3.376
H2(g)
29.07
–0.837
20.12
NH3(g)
25.89
33.00
–30.46
D
–62.41
62.599
–117.904
=–928
16、80+[–6241+2178–144]= –97086 J×mol-1
H2(g) + I2(s)
H2(g) + I2(g)
DrHOm,291= 49.455 kJ ×mol-1
2HI(g)
2HI(g)
Cp,m=55.64 J×K–1×mol–1
T=386.7K D熔HOm=16736 J×mol-1
Cp,m=62.76 J×K–1×mol–1
Cp,m=7R/2 J×K–1×mol–1
T=457.5K D蒸HOm=42677 J×mol-1
s?l
l ?g
DrHOm,473=?
DHHI
Cp.m=7R/2
DHI
17、2
DHH2
Cp.m=7R/2
32. 按圖示過程計(jì)算:
DHH2=nCp,mDT=3.5R(473–291)=5296 J
DHHI=nCp,mDT=2′3.5R(473–291)=10592 J
DHI2=DH1(s,291?386.7K) + DH2(s?l) + DH3(l,1386.7?457.5K) + DH4(l?g)
+ DH5(g,457.5?473K)
=55.64′(386.7–291)+16736+62.76′(457.5–386.7)+42677+3.5R′(473–457.5)
=69632 J
DHH2+DHI2+DrHOm,473=DrHOm,291+DHHI 5296+69632+DrHOm,473=49455+10592
DrHOm,473=–14.881 kJ ×mol-1