User:Milton Beychok/Sandbox

Using Riedel's method

Riedel proposed an empirical equation for estimating a liquid's heat of vaporization at its normal boiling point. The equation may be expressed as:

(3)     $H_{v}={\frac {1.092\,R\,T_{n}\,(\log _{e}p_{c}-\,1.013)}{0.930-(T_{n}/T_{c})}}$

where:
$H_{v}$	= Heat of vaporization, in J/mol
$R$	= 8.3144 = Universal gas constant, in J/(K $\cdot$ mol)
$T_{n}$	= The liquid's normal boiling point, in K
$T_{c}$	= The liquid's critical temperature, in K
$log_{e}$	= Logarithm on base $e$
$p_{c}$	= The liquid's critical pressure at $T_{n}$, in bar

For an empirical expression, equation (3) is surprisingly accurate. For example, given

Table 2: Application of
Trouton's rule

Name	Hv $\scriptstyle /$ Tn
Acetone	90.6
Benzene	87.3
Butane	82.3
Cyclohexane	84.8
Octane	87.3