The `pH` of `0.005 M` codine `(C_(18)H_(21)NO_(3))` solution is `9.95`. Calculate its ionisation constant and `pK_(b)`.

Explanation

Codenine is `W_(B)`:
`BOH hArr B^(o+)+overset(Θ)(O)H`
`pH=9.95 :. pOH=14-9.95=4.05`
`pOH_(W_(B))=1/2(pK_(b)-logC)`
`4.05xx2=(pK_(b)-log 5xx10^(-3))`
`8.1=(pK_(b)-0.7+3), pK_(b)=8.1-2.3=5.8`
`K_(b)=Antilog (-5.8)=` Antilog `(-5-0.8+1-1)`
=Antilog `bar(6).2=1.588xx10^(-16)`
`:. K_(b)=1.588xx10^(-6)`