Chapter 16, Problem 16.117CHP

Trouton’s rule says that the ratio of the molar heat of vaporization of a liquid to its normal boiling point (in kelvin) is approximately the same for all liquids: $\Delta H_{\text{vap}}/T_{\text{bp}}\approx 88\text{J}/\left(\text{K}\cdot \text{mol}\right)$.

1. (a) Check the reliability of Trouton’s rule for the liquids listed in the following table.
2. (b) Explain why liquids tend to have the same value of ΔH_vap/T_bp.
3. (c) Which of the liquids in the table deviate(s) from Trouton’s rule? Explain.

Liquid	bp (°C)	ΔHvap (kJ/mol)
Ammonia	–33.3	23.4
Benzene	80.1	30.8
Carbon tetrachloride	76.8	29.8
Chloroform	61.1	29.2
Mercury	356.6	59.11