Ionisation constant of `CH_(3)COOH` is `1.7 xx 10^(-5)` and concentration fo `H^(+)` in certain acetic acid solution is `3.4 xx 10^(-4) M` . The concentration of acetic acid solution is

Options

A. `3.4 xx 10^(-4)M`
B. `3.4 xx 10^(-3)M`
C. ``6.8 xx 10^(-4)M`
D. `6.8 xx 10^(-3)M`

Answer

D

Explanation

For a weak monobasric acid
`K_(a)=Calpha^(2)`
`K_(a)=C alpha.alpha=[H^(+)]alpha`
`alpha=(K_(a))/([H^(+)])`
`=(1.7 xx 10^(-4))/(3.4 xx 10^(-4)) =5 xx 10^(-2)`
`C alpha =[H^(+)]=3.4 xx10^(-4)`
`C=(3.4 xx 10^(-4))/(alpha)`
`=6.8 xx 10^(-3) M`