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:

Options

A. 4.5
B. 2.5
C. 9.5
D. 7

Answer

C

Explanation

For buffer solution`pH pK_(a) + "log" (["sal t"])/([Acid"]) = 4.5 + log (["sal t"])/([Acid"])`
As HA is 50% ionized, so [Salt] = [Acid]
pH = 4.5
`pH+pOH=14 therefore pOH=14-4.5=9.5`