O=C(c1c[nH]c(C(=O)C(Cl)(Cl)Cl)c1)c1ccccc1Cl
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?