Question

The ionization constant of chloroacetic acid is `1.35xx10^(-3)`. What will be the `pH` of `0.1 M` acid and its `0.1M` sodium salt solution?

Answer 1

`{:(CH_(2)CIOOH hArr,CH_(2)CIOO^(-)+,H^(+)),(C(1-alpha),Calpha,Calpha):}`
`Csqrt((K_(a))/(C ))= sqrt(K_(a)C)`
`=sqrt((1.35xx10^(-3)xx0.1))`
`=1.16xx10^(-2)`
`:. pH= -log[H^(+)]= 1.94`
For sod. Salt
`underset(C(1-h))(CH_(2)CIOO^(-))+H_(2)OhArr underset(Ch)(CH_(2)CIOOH)+underset(Ch)(OH^(-))`
`:. [OH^(-)]=Ch=Csqrt((K_(H))/(C ))= sqrt((K_(w)xxC)/(K_(a)))`
`= sqrt((10^(-14)xx0.1)/(1.35xx10^(-3)))=0.86xx10^(-6)`
`:. pOH= -log[OH^(-)]= -log 8.6xx10^(-7)`
`= 6.06`
`:. pH= 14-6.06=7.94`