The `pH` of `0.05M` aqueous solution of diethy`1` amine is `12.0` . Caluclate `K_(b)`.

Explanation

pH of solution =12.0 (given) ,
`"But"" "pH +pOH =14 :. pOH =14 -pH =14 -12 =2`
`" or "" "[OH^(-) (aq)] =10^(-2) M`
the dissociation of `(C_(2)H_(5))_(2)` NH is represented as :
`{:(,(C_(2)H_(5))_(2)NH+H_(2)O,hArr,(Cr_(2)H_(5))_(2)NH_(2)^(+),+,OH^(-)),("Initial no. of moles",0.05M,,0,,0),("No. of moles at the",(0.05M-0.01),,0.01M,,0.01M),("equilibrium point",=0.04M,,,,):}`
Applying Law of chemical equilibrium ,
`K_(b) =[[(C_(2)H_(5))_(2)NH_(2)^(+)][OH^(-)]]/[[(C_(2)H_(5))_(2)NH]] =((0.01M) xx (0.01M))/((0.04 M)) =2.5 xx 10^(-3)M`