Question

The `pK_(a)` of a weak acid `(HA)` is `4.5`. The `pOH` of an aqueous buffered solution of `HA` in which `50%` of the acid is ionized is:
A. `7.0`
B. `4.5`
C. 2.5
D. 9.5

Answer 1

Correct Answer - D
When HA is `50%` ionized, `[HA]=[A^(-)]`
`pH=pK_(a)+log.([A^(-)])/([HA])=pK_(a)=4.5`
(Given)
`pOH =14-pH=14-4.5 =9.5`