st law in throttling flow process application of the 1law in throttling flow process of a real gas
Joule experiment
expands to vacuum）
(Air expands to vacuum
ΔT=0 ot sensitive、not precise
、The heat capacity of water in
1The heat capacity of water in
the calorimeter vessel is much
than that of the gas；
larger than that of the gas
2、It does exist onflow
Th th d i The thermodynamic basis of Joule-Thomson
The thermodynamic basis of Joule-Thomson
=isenthalpic process h b b h h d hil h H 1= H 2isenthalpic process
(等焓过程)e T ，p have been both changed, while the H remains constant which indicates that the change of constant ，which indicates that the change of H with T has been compensated from the change of H with p . d i l f i f T d is not only a function of T .
The sign of the Joule-Thomson coefficient, μ
Th ‘Li d f i t ’The ‘Linde refrigerator ’
makes use of Joule-Thomson expansion to
liquefy gases. (Industrial q y g (
process of liquefying gas)
The Jou
equation of state of real gas For example assuming that it equation of state of real gas. For example, assuming that it satisfies the van der Waals equation, we have
C p m
2a (V m –b )2–RTbV m 2
RTV 3–2a (V –b )2
,m m m Inversion T l =——( 1 –—— 2 2a b ()temperature
Rb V m
22Inversion curve
——+ ———+ 1)2 –———= 023RTb b p 2a 8RTb a
2.8 Ap
in che y, 热化学）. Equation of chemical reactions
I Equation of chemical reactions
Chemical reactions (化学反应）：分子内部原子结合
(10 KJ.mol)，分子的种类和数
集方式发生改变的过程(10KJ mol-1分子的种类和数
目守恒。
uclear reaction （核反应）：原子核变革的过程(1010 N l ti原子核变革的过程10 KJ.mol-1)。分子的数目和原子的数目都在发生改变，但基本粒子守恒。
基本粒子守恒
Generalized equation of chemical reactions aA+bB=gG+hH
+ bB =gG + hH
0=
B B0=A+B+G+
∑νB B or0 νA A νB B νG G νH H B Chemical formula of substance
–Chemical formula of substance
νB-Stoichiometric number (化学计量数）of B:
product
II. Th
R ti A +bB G +hH Reaction aA + bB = gG + hH t = 0
n A °n B °n G °n H °
A –°
B –°G –°H –°———= ————= ————= ————n A n A n B n B n G n G n H n H νA
νB
νG
ν
H
n B –°B =n °+Definition
ξ≡————B n B ν
B
(B = A, B, G, H ) n B n
B + νB ξFor closed system,
d n B = νB d ξ
(1)(2)
000=−=
−=
−=
2
22
23
3H H N N NH NH n n n n n
n 10 mol
−−3
1
2
−−−000
n
n n n n
n =−=
−=
=
2
32
11
2
22
23
3H H N N NH NH 20 mol
