Question

The pH of 0.04 M hydrazine solution is 9.7 . Calculate its ionization constant `K_(b) and pK_(b)`.

Answer 1

Correct Answer - `8.96xx10^(-7), 6.04`
`NH_(2)NH_(2)+H_(2)O hArr NH_(2)NH_(3)^(+)+OH^(-)`
`pH = 9.7 :. Log [H^(+)]=-9.7 = bar(10).3 or [H^(+)] = 1.67 xx 10^(-10)`
`:. [OH^(-)]=(K_(w))/([H^(+)])=(10^(-14))/(1.67xx10^(-10))=5.98xx10^(-5)`
`K_(b)=([NH_(2)NH_(3)^(+)][OH^(-)])/([NH_(2)NH_(2)])=((5.98xx10^(-5))^(2))/(0.004) = 8.96xx10^(-7)`
`pK_(b) = - log K_(b) = - log (8.96 xx 10^(-7))=6.04`