How does the completeness of the reaction change in successive reactions of a polyprotic substance with water?

In successive reactions of a polyprotic substance with water, the completeness of each reaction generally decreases. This is because the first deprotonation typically occurs more readily than subsequent deprotonations due to the increasing negative charge on the anion, which makes it less favorable to lose additional protons. As a result, each successive reaction has a lower equilibrium constant, indicating that fewer protons are released and that the reactions become less complete.