A `0.25M` solution of pyridinium chloride `(C_(5)H_(5)overset(o+)NHC1^(Theta))` has `pH` of `2.89`. Calculate `pK_(b)` for pyridine `(C_(5)H_(5)N)`.

Answer

B

Explanation

Pyridinium chloride is a salt of `W_(B)//S_(A)`.
`:. pH = (1)/(2) (pK_(w) - pK_(b) - log C)`
`2.89 xx2 = 14 - pK_(b) - log (25 xx 10^(-2))`
`5.78 = 14 -pK_(b) - 2 log 5+2`
`= 14 - pK_(b) - 2 xx 0.7 + 2 (log 5~~ 0.7)`
`= 14 - pK_(b) + 0.6`
`pK_(b) = 14 + 0.6 - 5.78 = 8.82`