Chapter 16, Problem 55E

Acetic acid, CH₃CO₂H, can form a dimer, (CH₃CO₂H)₂, in the gas phase..

$2{\text{CH}}_3{\text{CO}}_2\text{H}\left(g\right)\to {\left({\text{CH}}_3{\text{CO}}_2\text{H}\right)}_2\left(g\right)$

The dimer is held together by to hydrogen bonds with a total strength of 66.5 kJ per mole of dimer.

At 25 °C, the equilibrium constant for the dimerization is $1.3\times {10}^3$ (pressure in atm). What is ?S ° for the reaction?