Question

A weak acid `(HA)` is titrated with `N//100 NaOH`. What will be the `pH` when `50%` of titration is completed. Given `K_(a)=1^(-4)` & concentration of `HA=0.1M`
A. 4
B. 8
C. 6.9
D. 10

Answer 1

Correct Answer - 1
`{:(HA,+,NaOH,rarr,NaA,+,H_(2)O),("Weak acid",,"Strong base",,"Salt of weak acid & strong base.",,):}`
Upon `50%` neutralization the amount of weak acid left and that of salt formed will be same and the system will act as an acidic buffer.
`{:(,HA,+,NaOH,rarr,NaA,+,H_(2)O),("Upon 50% Neutralization",a//2,,,,a//2,,):}`
`pH=PK_(a)+log.([Sal t])/([Aci d])`
`=4+log.(a//2)/(a//2)=4 " "Ans.(1)`