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?

Question

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? (A) Ka1 > Ka2 > Ka3 (B) Ka1 = Ka2 = Ka3 (C) Ka1 < Ka2 < Ka3 (D) Ka1 = Ka2 + Ka3

Tardigrade Admin · Accepted Answer

The values of dissociation constants for successive stages decrease.

$K_{a_{1}} > K_{a_{2}} > K_{a_{3}}$

$K_{a_{1}} = K_{a_{2}} = K_{a_{3}}$

$K_{a_{1}} < K_{a_{2}} < K_{a_{3}}$

$K_{a_{1}} = K_{a_{2}} + K_{a_{3}}$

The values of dissociation constants for successive stages decrease.

Q. For a polybasic acid, the dissociation constants have a different values for each step, e.g., H3​A⇌H++H2​A−;K=Ka1​​ H2​A−⇌H++H2​A2−;K=Ka2​​ HA2−⇌H++A3−;K=Ka3​​ What is the observed trend of dissociation constants in successive stages?

Ka1​​>Ka2​​>Ka3​​

Ka1​​=Ka2​​=Ka3​​

Ka1​​<Ka2​​<Ka3​​

Ka1​​=Ka2​​+Ka3​​

The values of dissociation constants for successive stages decrease.

$K_{a_{1}} > K_{a_{2}} > K_{a_{3}}$

$K_{a_{1}} = K_{a_{2}} = K_{a_{3}}$

$K_{a_{1}} < K_{a_{2}} < K_{a_{3}}$

$K_{a_{1}} = K_{a_{2}} + K_{a_{3}}$