The ratio of dissociation constant of two weak acids HA and HB is 4. At what molar concentration ratio, the two acids will have same pH ?

Options

A. 2
B. `0.5`
C. 4
D. `0.25`

Answer

D

Explanation

`K_(a)=([H^(+)][A^(-)])/([HA])=([H^(+)]^(2))/([HA]) ( :' [H^(+)]=[A^(-)])`
and `K_(b)= ([H^(+)][B^(-)])/([HB])= ([H^(+)]^(2))/([HB]) ( :' [H^(+)]=[B^(-)])`
Also `H^(+)` are same.
`:. (K_(a))/(K_(b))=([HB])/([HA])=(4)/(1)`
`([HA])/([HB])=(1)/(4)`