热力学定律 Helmholtz and Gibbs Energies
变不等式 到 状态函数热力学定律 Helmholtz and Gibbs Energies
Helmholtz Energy A (亥姆霍兹能 )
恒温 恒容最大功函 (Maximum Work Function)
dwmax = dA Why?
dQ? TdS
U = Q + W}
dU? TdS + dW? dW? dU - TdS
< 0
物理意义
Gibbs Free Energy G (吉布斯自由能 )
热力学定律 Helmholtz and Gibbs Energies
恒温 恒压最大非体积功 (Maximum Non-Expansion Work)
Chemical reactions are
spontaneous in the direction
of decreasing Gibbs energy.
标准 Gibbs能标准生成 Gibbs能
Combining First and Second Laws
First Law dU = dQ + dW
dWrev = -PdV dQrev = TdS (可逆 & 只有体积功 )
dH = TdS + VdP
Temperature Dependence of G
T
HGS
T
G
P


T
H
T
G
T
G
P










TdT
dG
T
G
TT
G
T PP
11
2
1
T
G
T
G
T P







T
G
T
G
T P
1
2T
H
T
G
T P




Gibbs – Helmholz
Equation
温度变化关系自由能 焓 可测
G求算
(1) 恒温过程恒温 dT = 0
21PP V d PG
Perfect Gases
2
1
1
2 lnln
V
Vn R T
P
Pn R TG
(2) 相变过程可逆相变?G = 0
不可逆相变 需设计可逆过程
(3) 化学反应恒温恒压? rG =? rH? T? rS
- T *?S
具体计算课下先看例子 ! (P68,69)