Question

For cationic hydrolysis, pH given by
A. `pH=(1)/(2)pK_(w)+(1)/(2)pK_(a)+(1)/(2)log C`
B. `pH=(1)/(2)pK_(w)-(1)/(2)pK_(a)-(1)/(2)log C`
C. `pH=(1)/(2)pK_(w)+(1)/(2)pK_(a)-(1)/(2)pK_(b)`
D. `pH=(1)/(2)pK_(w)+(1)/(2)pK_(b)+(1)/(2)log C`

Answer 1

Correct Answer - B
`B^(+)+H_(2)O hArr BOH+H^(+)`
`[H^(+)] = ((K_(w).C)/(K_(b)))^(1//2)`
`pH= - log[H^(+)]= -"log" ((K_(w).C)/(K_(b)))^(1//2)`
`= (-1)/(2)[log K_(w)-logK_(b)+log C]`
`= (1)/(2)[pK_(w)-pK_(b)-logC]`