pH of 0.05(M) aqueous solution of diethylamine is 12. calculate the ionisation constant and degree of ionisationn of the amine.

Explanation

Diethylamine is a weak monoacidic base. For such on
aqueous basic solution,` pH=14-((1)/(2)pK_(b)-(1)/(2)logc)`
As, `pH=12 and c=0.05(M)`
`therefore 12=14-(1)/(2)pK_(b)+(1)/(2)+(1)/(2)log(0.05)=14-(1)/(2)pK_(b)-0.65`
or, `pK_(b)=2.7or, -log_(10)K_(b)=2.7" "thereforeK_(b)=2xx10^(-3)`
`therefore`Ionisation constant of diethylamine`=2xx10^(-3)`.
Degree of ionisation of the amine `(alpha)`
`=sqrt((K_(b))/(c))=sqrt((2xx10^(-3))/(0.05))=0.2`