PROPRIETARY MATERIAL
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τ2.256=TτT0
⋅:= T 1202.8 K=
Ans.
T 1705.4degF=
4.3 Assume air at the
g
iven conditions an ideal
g
as. Basis of calculation is 1 second
.
P 1 atm⋅:= T0122 degF⋅:= V 250 ft3
⋅:= T 932 degF⋅:=
Convert given values to SI units V 7.079 m3
=
T T 32degF−( ) 273.15K+:= T0T032degF−
()
273.15K+:=
T 773.15 K=T0323.15 K=
nPV⋅
RT
0
⋅
:= n 266.985 mol=
For air: A 3.355:= B 0.575 10 3−
⋅:= C 0.0:= D 0.016−105
⋅:=
∆H R ICPH T0T,A,B,C,D,
()
⋅:=
τ3:= (guess) Given
QnR⋅AT
0
⋅τ1−
()
⋅B
2T02
⋅τ
21−
()
⋅+
⎡
⎢
⎣
⎤
⎥
⎦
C
3T03
⋅τ
31−
()
⋅+
⎡
⎢
⎣
⎤
⎥
⎦
⋅=
τFind τ
()
:= τ 2.652=TτT0
⋅:= T 1413.8 K=Ans.
τFind τ
()
:=
77
PROPRIETARY MATERIAL
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⎢
⎥
⎢
⎥
Given T2T1
P2
P1
⎛
⎜
⎝
⎞
⎠
R
CP
⋅=CPFind CP
()
:= CP56.95 J
mol K⋅
=Ans.
∆Hncalc RT
n
⋅
1.092 ln Pc
bar
⎛
⎜
⎝
⎞
⎠1.013−
⎛
⎜
⎝
⎞
⎠
⋅
0.930 Trn
−
⋅:= ∆Hncalc 30.108 kJ
mol
=Ans.
∆H 13.707 kJ
mol
=Qn∆H⋅:=
Q 3.469 103
×BTU=Ans.
∆H R ICPH T0T,A,B,C,D,
()
⋅:=
∆H 9.441 104
×J
mol
=Qn∆H⋅:= Q 9.4315 106
×kJ=Ans.
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PROPRIETARY MATERIAL
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To compare with the value listed in Table B.2, calculate the % error.
%error
∆Hncalc ∆Hn
−
∆Hn
:= %error 3.464 %=
PROPRIETARY MATERIAL
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The ln P vs. 1/T relation over a short range is very nearly linear. Our
procedure is therefore to take 5 points, including the point at the
temperature of interest and two points on either side, and to do a linear
least-squares fit, from which the required derivative in Eq. (4.11) can be
found. Temperatures are in rankines, pressures in psia, volumes in cu
ft/lbm, and enthalpies in Btu/lbm. The molar mass M of tetrafluoroethane is
102.04. The factor 5.4039 converts energy units from (psia)(cu ft) to Btu.
4.10
The values calculated with Eq. (4.13) are within 2% of the handbook values.
%error
0.072
0.052−
0.814−
1.781
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
%=
∆H2
26.429
31.549
33.847
32.242
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
kJ
mol
=
Ans.
∆H2calc
26.448
31.533
33.571
32.816
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
kJ
mol
=
%error
∆H2calc ∆H2
−
∆H2
→
⎯
⎯⎯⎯⎯
⎯
:=
Eq. (4.13)
∆H2calc ∆H1
1T
r2
−
1T
r1
−
⎛
⎜
⎝
⎞
⎠
0.38
⋅
⎡
⎢
⎢
⎣
⎤
⎥
⎥
⎦
→
⎯
⎯⎯⎯⎯⎯⎯⎯
⎯
:=
∆H2
26.429
31.549
33.847
32.242
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
kJ
mol
=Tr1
0.658
0.673
0.628
0.631
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
=
∆H1∆Hn
:=∆H2∆H25 M⋅
()
→
⎯
⎯⎯
⎯
:=Tr2
25 273.15+()K
Tc
:=Tr1
Tn
Tc
→
⎯
:=
M
72.150
86.177
78.114
82.145
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
gm
mol
:=∆H25
366.3
366.1
433.3
392.5
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
J
gm
:=Tn
36.0
68.7
80.0
80.7
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
273.15+
⎡
⎢
⎢
⎢
⎢
⎣
⎤
⎥
⎥
⎥
⎥
⎦
K:=
∆Hn
25.79
28.85
30.72
29.97
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
kJ
mol
:=Pc
33.70
30.25
48.98
43.50
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
bar:=
Tc
469.7
507.6
562.2
560.4
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
K:=
b)
80
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∆H 85.817=85.834()
(c) ∆H 81.034=81.136()
(d) ∆H 76.007=75.902()
(e) ∆H 69.863=69.969()
4.11
M
119.377
32.042
153.822
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
gm
mol
⋅:= Tc
536.4
512.6
556.4
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
K⋅:= Pc
54.72
80.97
45.60
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
bar⋅:= Tn
334.3
337.9
349.8
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
K⋅:=
∆Hexp is the given
value at the normal
boiling point.
∆H is the value at
0 degC. Tr1
273.15K
Tc
→
⎯
⎯
:= Tr2
Tn
Tc
→
⎯
:=
(a) T 459.67 5+:= ∆V 1.934 0.012−:= i15..:=
Data: P
18.787
21.162
23.767
26.617
29.726
⎛
⎜
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎟
⎠
:= t
5−
0
5
10
15
⎛
⎜
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎟
⎠
:= xi
1
ti459.67+
:= yiln Pi
()
:=
slope slope x y,():= slope 4952−=
dPdT
P−()
3
T2slope⋅:= dPdT 0.545=
∆HT∆V⋅dPdT⋅
5.4039
:= ∆H 90.078=Ans.
The remaining parts of the problem are worked in exactly the same
way. All answers are as follows, with the Table 9.1 value in ( ):
(a) ∆H 90.078=90.111()
(b)
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Pr0.022=Pr
P
Pc
:=Tr0.648=Tr
Tn
Tc
:=
∆Hn29.1 kJ
mol
:=P 1atm:=Tn329.4K:=Vc209 cm3
mol
⋅:=
Zc0.233:=Pc47.01bar:=Tc508.2K:=ω 0.307:=
Acetone4.12
PCE
0.34
8.72
0.96−
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
%=
∆Hn
247.7
1195.3
192.3
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
J
gm
=
PCE
0.77−
4.03−
0.52−
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
%=
∆Hn
245
1055.2
193.2
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
J
gm
=
This is the % error
PCE
∆Hn∆Hexp
−
∆Hexp
100⋅%
⎛
⎜
⎝
⎞
⎠
→
⎯
⎯⎯⎯⎯⎯⎯⎯
⎯
:=
∆Hn∆H1T
r2
−
1T
r1
−
⎛
⎜
⎝
⎞
⎠
0.38
⋅
⎡
⎢
⎢
⎣
⎤
⎥
⎥
⎦
→
⎯
⎯⎯⎯⎯⎯⎯
⎯
:=
(a) By Eq. (4.13)
Tr2
0.623
0.659
0.629
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
=
Tr1
0.509
0.533
0.491
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
=
∆Hexp
246.9
1099.5
194.2
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
J
gm
⋅:=∆H
270.9
1189.5
217.8
⎛
⎜
⎜
⎜
⎝
⎞
⎟
⎠
J
gm
⋅:=
82
PROPRIETARY MATERIAL
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⎜
⎯
⎯
⎢
⎢
⎥
⎥
⎢
⎢
⎥
⎥
⎯
⎯
C 228.060:=B 2756.22:=A 14.3145:=
∆V 2.602 104
×cm3
mol
=∆VVV
sat
−:=
∆HT∆V⋅B
TC+()
2
⋅e
AB
TC+()
−
⎡
⎢
⎣⎤
⎥
⎦
⋅=
gives
Psat e
AB
TC+
−
=
with Antoine’s Equation
∆HT∆V⋅
T
Psat
d
d
⋅=
Combining the Clapyeron equation (4.11)
Vsat 70.917 cm3
mol
=
Eq. (3.72)
Vsat VcZc
1T
r
−
()
2
7
⋅:=
Liquid Volume
V 2.609 104
×cm3
mol
=VZR⋅Tn
⋅
P
:=
(Pg. 102)
Z 0.965=Z1B
0
Pr
Tr
⋅+ωB1
⋅Pr
Tr
⋅+:=
Eq. (3.66)
B10.924−=B10.139 0.172
Tr4.2
−:=
Eq. (3.65)
B00.762−=
B00.083 0.422
Tr1.6
−:=
Vapor Volume
Generalized Correlations to estimate volumes
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∆Hcalc Tn∆V⋅B
Tn273.15K−
KC+
⎛
⎜
⎝
⎞
⎠
2e
AB
Tn273.15K−
KC+
⎛
⎜
⎝
⎞
⎠
−
⎡
⎢
⎢
⎣
⎤
⎥
⎥
⎦
⋅kPa
K
⎡
⎢
⎢
⎢
⎢
⎢
⎣
⎤
⎥
⎥
⎥
⎥
⎥
⎦
⋅:=
∆Hcalc 29.662 kJ
mol
=Ans. %error
∆Hcalc ∆Hn
−
∆Hn
:= %error 1.9 %=
Acetic Acid 37.6 58.7%
Acetonitrile 31.3 3.5%
Benzene 30.8 0.2%
iso-Butane 21.2 -0.7%
n-Butane 22.4 0.0%
1-Butanol 43.5 0.6%
n-Pentane 25.9 0.2%
Phenol 45.9 -0.6%
1-Pro
p
anol 41.9 1.1%
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PROPRIETARY MATERIAL
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p
2-Propanol 40.5 1.7%
Toluene 33.3 0.5%
Water 41.5 2.0%
o-Xylene 36.7 1.2%
m-Xylene 36.2 1.4%
PROPRIETARY MATERIAL
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Q 1.372 103
×kW=Ans.
(b) Benzene: ∆Hv28.273 kJ
mol
=∆H 55.296 kJ
mol
=Q 1.536 103kW⋅=
(c) Toluene ∆Hv30.625 kJ
mol
=∆H 65.586 kJ
mol
=Q 1.822 103kW⋅=
4.15 Benzene Tc562.2K:= Pc48.98bar:= Tn353.2K:=
T1sat 451.7K:= T2sat 358.7K:= Cp162 J
mol K⋅
⋅:=
CPV T() A
V
BV
KT⋅+ CV
K2T2
⋅+
⎛
⎜
⎝
⎞
⎠
R⋅:=
P 3bar:= Tsat 368.0K:= T1300K:= T2500K:=
∆H
T1
Tsat
TCPL T()
⌠
⎮
⌡d∆Hv
+
Tsat
T2
TCPV T()
⌠
⎮
⌡d+:= ∆H 49.38 kJ
mol
=
n 100 kmol
hr
:= Qn∆H⋅:=
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PROPRIETARY MATERIAL
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∆Hv∆Hn
1T
r
−
1T
rn
−
⎛
⎜
⎝
⎞
⎠
0.38
⋅:= ∆Hv6.638 kJ
mol
=
∆Hf227480 J
mol
⋅:= ∆H298 ∆Hf∆Hv
−:= ∆H298 220.8 kJ
mol
=Ans.
Estimate ∆Hv using Riedel equation (4.12) and Watson correction (4.13)
Trn
Tn
Tc
:= Trn 0.628=Tr2sat
T2sat
Tc
:= Tr2sat 0.638=
∆Hn
1.092 ln Pc
bar
⎛
⎜
⎝
⎞
⎠1.013−
⎛
⎜
⎝
⎞
⎠
⋅
0.930 Trn
−R⋅Tn
⋅:= ∆Hn30.588 kJ
mol
=
∆Hv∆Hn
1T
r2sat
−
1T
rn
−
⎛
⎜
⎝
⎞
⎠
0.38
⋅:= ∆Hv30.28 kJ
mol
=
Assume the throttling process is adiabatic and isenthalpic.
Guess vapor fraction (x): x 0.5:=
Given CpT1sat T2sat
−
()
⋅x∆Hv
⋅=x Find x():= x 0.498=Ans.
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⎜
or dQ CPdT⋅RdT⋅− RdT⋅
1δ−
+=
which reduces to dQ CPdT⋅δ
1δ− R⋅dT⋅+=
or dQ CP
R
δ
1δ−
+
⎛
⎜
⎝
⎞
⎠R⋅dT⋅=(C)
Since CP is linear in T, the mean heat capacity is the value of
CP at the arithmetic mean temperature. Thus Tam 675:=
(b) For 1,3-butadiene: ∆H298 88.5 kJ
mol
=
(c) For ethylbenzene: ∆H298 12.3−kJ
mol
⋅=
(d) For n-hexane: ∆H298 198.6−kJ
mol
⋅=
(e) For styrene: ∆H298 103.9 kJ
mol
⋅=
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PROPRIETARY MATERIAL
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Parts (a) – (d) can be worked exactly as Example 4.7. However, with
Mathcad capable of doing the iteration, it is simpler to proceed differently.
∆H298 2 241818−()⋅2 393509−()⋅+ 52510−[]
J
mol
⋅:=
C2H4 + 3O2 = 2CO2 + 2H2O(g)4.19
Comparison is on the basis of equal numbers of C atoms.
Ans.
∆H298 3−=770,012 J⋅,∆H298 3770012−=
∆H298 6 393509−()⋅6 241818−()⋅+ 41950−()−:=
For the combustion of 1-hexene:
C6H12(g) + 9O2(g) = 6CO2(g) + 6H2O(g)
Ans.
∆H298 4−=058,910 J⋅,
For 6 MeOH:
∆H298 676485−=
Ans.
P211.45 bar=P2P1
T2
T1
⎛
⎜
⎝
⎞
⎠
δ
δ1−
⋅:=P11 bar⋅:=
Ans.
Q 6477.5 J
mol
=QCPm
R
δ
1δ−
+
⎛
⎜
⎝
⎞
⎠R⋅T2T1
−
()
⋅:=
δ1.55:=T1400 K⋅:=T2950 K⋅:=
Integrate (C):
CPm R 3.85 0.57 10 3−
⋅Tam
⋅+
()
⋅:=
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PROPRIETARY MATERIAL
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τFind τ
()
:= τ 8.497=TT
0τ⋅:= T 2533.5 K=Ans.
(b) nO20.75=nn214.107=T 2198.6 K⋅=Ans.
(c) nO21.5=nn216.929=T 1950.9 K⋅=Ans.
(d) nO23.0=nn222.571=T 1609.2 K⋅=Ans.
Index the product species with the numbers:
1 = oxygen
2 = carbon dioxide
3 = water (g)
4 = nitrogen
(a) For the product species, no excess air:
n
0
2
2
11.286
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
:= A
3.639
5.457
3.470
3.280
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
:= B
0.506
1.045
1.450
0.593
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
10 3−
K
⋅:= D
0.227−
1.157−
0.121
0.040
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
105
⋅K2
:=
i14..:= A
i
niAi
⋅
()
∑
:= B
i
niBi
⋅
()
∑
:= D
i
niDi
⋅
()
∑
:=
A 54.872=B 0.012 1
K
=D 1.621−105
×K2
=
For the products, ∆HPR
T0
T
T
CP
R
⌠
⎮
⎮
⌡
d⋅=T0298.15K:=
The integral is given by Eq. (4.7). Moreover, by an energy balance,
∆H298 ∆HP
+0=
τ2:= (guess)
Given ∆H298
−RAT
0
⋅τ1−
()
⋅B
2T02
⋅τ
21−
()
⋅+ D
T0
τ1−
τ
⎛
⎜
⎝
⎞
⎠
⋅+
⎡
⎢
⎣
⎤
⎥
⎦
⋅=
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Ans.
T 2282.5 K K=TT
0K⋅τ⋅:=τ 7.656=τ Find τ
()
:=
∆H298
−∆Hair
−RAT
0
⋅τ1−
()
⋅B
2T02
⋅τ
21−
()
⋅+
D
T0
τ1−
τ
⎛
⎜
⎝
⎞
⎠
⋅+
…
⎡
⎢
⎢
⎢
⎣
⎤
⎥
⎥
⎥
⎦
⋅=
Given
(guess)
τ2:=
D 1.735−105
×K2
=B 0.016 1
K
=A 78.84=
D
i
niDi
⋅
()
∑
:=
B
i
niBi
⋅
()
∑
:=
A
i
niAi
⋅
()
∑
:=
D
0.227−
1.157−
0.121
0.040
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
105
⋅K2
⋅:=
B
0.506
1.045
1.450
0.593
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
10 3−
K
⋅:=A
3.639
5.457
3.470
3.280
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
:=
n
1.5
2
2
16.929
⎛
⎜
⎜
⎜
⎜
⎝
⎞
⎟
⎟
⎠
:=
∆H298 ∆Hair
+∆HP
+0=
The energy balance here gives:
∆Hair 309399−J
mol
=
∆Hair 21.429 8.314⋅3.65606⋅298.15 773.15−()⋅J
mol
⋅:=
MCPH 773.15 298.15,3.355,0.575 10 3−
⋅, 0.0,0.016−105
⋅,
()
3.65606=
For one mole of air:
∆Hair MCPH 298.15 773.15−()⋅=
∆Hair ∆H298
+∆HP
+0=
(e) 50% xs air preheated to 500 degC. For this process,
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4.20 n-C5H12 + 8O2 = 5CO2 + 6H2O(l)
By Eq. (4.15) with data from Table C.4:
∆H298 5 393509−()⋅6 285830−()⋅+ 146760−()−:=
∆H298 3−=535,765 J⋅, Ans.
(b) -905,468 J
(c) -71,660 J
(d) -61,980 J
(e) -367,582 J
(f) -2,732,016 J
(g) -105,140 J
(h) -38,292 J
(i) 164,647 J
(j) -48,969 J
(k) -149,728 J
(l) -1,036,036 J
(m) 207,436 J
(o) 178,321 J
(p) -132,439 J
(q) -44,370 J
(r) -68,910 J
(s) -492,640 J
(t) 109,780 J
(u) 235,030 J
(v) -132,038 J
(w) -1,807,968 J
(x) 42,720 J
(y) 117,440 J
(z) 175,305 J
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4.22 The solution to each of these problems is exactly like that shown in
Example 4.6. In each case the value of ∆Ho
298 is calculated in Problem
4.21. Results are given in the following table. In the first column the
letter in ( ) indicates the part of problem 4.21 appropriate to the ∆Ho
298
value.
T/K ∆A 103 ∆B 106 ∆C 10-5 ∆D IDCPH/J ∆HoT/J
(a) 873.15 –5.871 4.181 0.000 -0.661 -17,575 -109,795
(b) 773.15 1.861 -3.394 0.000 2.661 4,729 -900,739
(f) 923.15 6.048 –9.779 0.000 7.972 15,635 –2,716,381
(i) 973.15 9.811 –9.248 2.106 –1.067 25,229 189,876
(j) 583.15 -9.523 11.355 -3.450 1.029 -10,949 -59,918
(l) 683.15 -0.441 0.004 0.000 -0.643 -2,416 -1,038,452
(m) 850.00 4.575 -2.323 0.000 -0.776 13,467 220,903
(t) 733.15 4.016 –4.422 0.991 0.083 7,424 117,204
(u) 750.00 7.297 -9.285 2.520 0.166 12,172 247,202
(v) 900.00 2.418 –3.647 0.991 0.235 3,534 -128,504
(w) 673.15 2.586 -4.189 0.000 1.586 4,184 –1,803,784
(x) 648.15 0.060 0.173 0.000 -0.191 125 42,845
(y) 1083.15 4.175 -4.766 1.814 0.083 12,188 129,628
(g) –3.629 8.816 -4.904 0.114
(h) –9.987 20.061 -9.296 1.178
(k) 1.704 -3.997 1.573 0.234
(z) -3.858 -1.042 0.180 0.919
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∆HcCH4 890649−J
mol
=
Ans.
n HigherHeatingValue⋅5dollar
GJ
⋅7.985 105
×dollar
day
=
n 1.793 108
×mol
day
=nq
P
RT⋅
⋅:=
Assuming methane is an ideal gas at standard conditions:
4.24 q 150 106
⋅ft3
day
:= T6032−()
5
9K⋅273.15K+:= T 288.71 K=P 1atm:=
The higher heating value is the negative of the heat of combustion with water
as liquid product.
Calculate methane standard heat of combustion with water as liquid product:
CH4 + 2O2 –> CO2 +2H2O
Standard Heats of Formation:
∆HfCH4 74520−J
mol
:= ∆HfO2 0J
mol
:=
∆HfCO2 393509−J
mol
:= ∆HfH2Oliq 285830−J
mol
:=
∆Hc∆HfCO2 2∆HfH2Oliq
⋅+∆HfCH4
−2∆HfO2
⋅−:=
HigherHeatingValue ∆Hc
−:= ∆Hc8.906−105
×J
mol
=
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0.85 ∆HcCH4
⋅0.07 ∆HcC2H6
⋅+ 0.03 ∆HcC3H8
⋅+ 932.875−kJ
mol
=
c)
Gas b) has the highest standard heat of combustion. Ans.
.−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
N2(g)+2H2(g)+C(s)+1/2O2(g)=(NH2)2CO(s)
∆H298 ∆Hf1 ∆Hf2
+∆H+:= ∆H298 333509−J=Ans.
Calculate ethane standard heat of combustion with water as liquid product:
Standard Heats of Formation:C2H6 + 7/2O2 –> 2CO2 +3H2O
∆HfC2H6 83820−J
mol
:=
∆HcC2H6 2∆HfCO2 3∆HfH2Oliq
⋅+∆HfC2H6
−7
2∆HfO2
⋅−:=
∆HcC2H6 1560688−J
mol
=
0.95 ∆HcCH4
⋅0.02 ∆HcC2H6
⋅+ 0.02 ∆HcC3H8
⋅+ 921.714−kJ
mol
=
a)
0.90 ∆HcCH4
⋅0.05 ∆HcC2H6
⋅+ 0.03 ∆HcC3H8
⋅+ 946.194−kJ
mol
=
b)
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