Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Heat equation wikipedia , lookup
Internal energy wikipedia , lookup
Adiabatic process wikipedia , lookup
Thermodynamic system wikipedia , lookup
Heat transfer physics wikipedia , lookup
Van der Waals equation wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
Equation of state wikipedia , lookup
Gibbs free energy wikipedia , lookup
pKa is an Energy Term • A proton abstracted by a base is generalized in the following reaction AH + B(-) A(-) + BH o o We will worry about the descriptive details of how this happens later. • The half reaction in water is: AH + H2O A(-) + H3O(+) o o has an equilibrium constant associated with it Keq = [A][H3O]/[AH][H2O] o The terms in this equation are concentration. The molarity of water, [H2O] is 55 M or 55 moles/Liter o The acidity constant is • Ka = Keq[H2O] = [A][H3O]/[AH] Consider this equation: Ka = Keq[H2O] Taking the negative log of both sides and multiplying by RT gives: o −RTlogKa =−RTlog(Keq[H2O])= −RTlogKeq −RTlog[H2O] R is the gas constant and T is the absolute temperature −2.30RTlogKa = −RTLnKeq − RTLn[H2O] but −logKa = pKa and −RTLnKeq = ∆G 2.30RTpKa + RTLn[H2O]= ∆G Result: PKa increases linearly with energy! Acids conj. bases species with lone pairs Deprotonation Reaction Coordinate The species with lone pairs (conjugate bases) respond more to structural changes than the acids.