What concentration of dichloroacetic acid gives `[H^(+)]=8.5xx10^(-3)M` ?
`("Given": K_(a)"of acid" = 5.0xx10^(-2))`.

Explanation

`CHCI_(2)COOH hArr CHCI_(2)COO^(-)+H^(+)`
`[H^(+)]=[CHCI_(2)COO^(-)]= 8.5xx10^(-3)M= C alpha`
and `CHCI_(2)COOH=C(1-alpha)=C-C alpha`
`K_(a)= ([H^(+)][CHCI_(2)COO^(-)])/([CHCI_(2)COOH])`
`=((8.5xx10^(-3)xx8.5xx10^(-3)))/((C- 8.5xx10^(-3)))= 5xx10^(-2)`
`:. C = 9.95xx10^(-3)M`