Equilibrium - Result Question 17
####18. For dibasic acid correct order is
[2000]
(a) $K _{a_1}<K _{a_2}$
(b) $K _{a_1}>K _{a_2}$
(c) $K _{a_1}=K _{a_2}$
(d) not certain
Show Answer
Solution:
- (b) In polyprotic acids the loss of second proton occurs much less readily than the first. Usually the $K_a$ values for successive loss of protons from these acids differ by at least a factor
of $10^{-3}$ i.e., $K _{a_1}>K _{a_2}$
$H_2 X \rightarrow H \quad HX \quad K _{a_1}$
$HX \rightarrow H \quad X^{2} \quad K _{a_2}$
