Question

The p K a of acetic acid is 4.76, and the p K a of trichloroacetic acid, which is used to remove warts, is 0.7. Calculate the dissociation constant of each acid. Which is the stronger acid?

Answer 1

CH3COOH: Ka = 1.74 E-5

CCL3COOH: Ka = 0.1995

⇒ K CCl3COOH >> K CH3COOH ∧ pKCCl3COOH < pKCH3COOH; the higher pKa the extent of the dissociation is less; therefore CCl3COOH is a stronger acid than CH3COOH

Explanation :

CH3COOH:

pKa = 4.76 = - Log Ka

⇒ Ka = 1.74 E-5

CCl3COOH:

∴ pKa = 0,7 = -log Ka

⇒ Ka = 0.1995