Consider two carboxylic acids (acids that contain the-COOH group): CH3COOH (acetic acid, K...

Consider two carboxylic acids (acids that contain the

-COOH group): CH3COOH (acetic acid, Ka = 1.8 × 10−5) and CH2ClCOOH (chloroacetic acid, Ka= 1.4 × 10−3).

(a) Calculate ∆G° for the ionization of these acids at 25°C.

(b) From the equation ∆G° = ∆H° − T∆S°, we see that the contributions to the ∆G° term are an enthalpy term (∆H°) and a temperature times entropy term (TΔS°). These contributions are listed here for the two acids:

Which is the dominant term in determining the value of ∆G°(and hence Ka of the acid)? (c) What processes contribute to ∆H° ? (Consider the ionization of the acids as a Brønsted acid-base reaction.) (d) Explain why the T∆S° term is more negative for CH3COOH.