Question

Which one of the following is true for any diprotic acid, `H_(2)X`?
A. `K_(a_(2))=K_(a_(1))`
B. `K_(a_(2))gt K_(a_(1))`
C. `K_(a_(2))lt K_(a_(1))`
D. `K_(a_(2))=(1)/(K_(a_(1)))`

Answer 1

Correct Answer - C
`H_(2)X hArr H^(+)+HX^(-)(K_(a_(1)))`
`HX^(-)hArr +X^(2-)(K_(a_(2)))`
In Ist equation hydrogen ion is formed from neutral molecule whereas in Iind equation it comes from negatively charged species. Due to negative charge removal of proton is difficult.
So, `K_(a_(1))gt K_(a_(2))`