For a polybasic acid, the dissociation constants have a different values for each step, e.g.,
H₃A H⁺ + H₂A^–^, ; K = K_a₁
H₂A^– H⁺ + HA^2–^, ; K = K_a₂
HA^2– H⁺ + A^3–^, ; K = K_a₃
What is the observed trend of dissociation constants in successive stages?

Question

For a polybasic acid, the dissociation constants have a different values for each step, e.g.,
H₃A

H⁺ + H₂A^–^, ; K = K_a₁
H₂A^–

H⁺ + HA^2–^, ; K = K_a₂
HA^2–

H⁺ + A^3–^, ; K = K_a₃
What is the observed trend of dissociation constants in successive stages?

Accepted Answer

(A) K a 1 > K a 2 > K a 3

For a polybasic acid, the dissociation constants have a different values for each step…