1. Tardigrade
  2. Question
  3. Chemistry
  4. For a polybasic acid, the dissociation constants have a different values for each step, e.g., H 3 A leftharpoons H ++ H 2 A - ; K=Ka1 H 2 A - leftharpoons H ++ H 2 A 2- ; K=Ka2 HA 2- leftharpoons H ++ A 3- ; K=Ka3 What is the observed trend of dissociation constants in successive stages?

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Q. For a polybasic acid, the dissociation constants have a different values for each step, e.g.,
$H _3 A \rightleftharpoons H ^{+}+ H _2 A ^{-} ; K=K_{a_1}$
$H _2 A ^{-} \rightleftharpoons H ^{+}+ H _2 A ^{2-} ; K=K_{a_2}$
$HA ^{2-} \rightleftharpoons H ^{+}+ A ^{3-} ; K=K_{a_3}$
What is the observed trend of dissociation constants in successive stages?

Equilibrium

Solution:

The values of dissociation constants for successive stages decrease.