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The pK(a0 of a weak acid (HA) is 4.5. Th...

The `pK_(a0` 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

`2.5`

B

`9.5`

C

`7.0`

D

`4.5`

Text Solution

Verified by Experts

The correct Answer is:
B
If the given weak acid is 50% ionised then its conjugate base will have the concentration same as that of weak acid.
`pH=pK_(a)+"log"(["conjugate base"])/(["Acid"])`
`=4.5+"log"(0.5c)/(0.5c)=4.5`
`therefore pOH = 14-4.5=9.5`
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