My question concerns polyprotic acids.

Question

Formulate a reasoning for the stepwise ionization and subsequent weakening of the acid for polyprotic acids.

Answer 1

Consider the hypothetical polyprotic acid H3A. The first ionization will be the greatest as the hydrogen ion is coming off a neutral molecule. The second hydrogen ion will have a lower ionization as the positively charged hydrogen ion is coming off the now negatively charged anion. The same reasoning applies to the third hydrogen ion as the anion will now have two negative charges.