Question

`K_(a)` for ascorbic acid `("HA sc" ) ` is `5xx10^(-5)`. Calculate the hydrogen ion concentration and percentage of hydrolysis in an aqueous solution in which the concentration of `Asc^(-)` ions is 0.02 M.

Answer 1

As ascorbic acid is a weak acid, aqueous solution of `Asc^(-)` means the solution of a salt of weak acid with strong base. For such a salt , degree of hydrolysis is given by
`h=sqrt((K_(w))/(K_(a)xxc))=sqrt((10^(-14))/(5xx10^(-5)xx2xx10^(-2))=10^(-4) = 10^(-4) xx 100 % = 0.01 % `
`{:(Asc^(-),+,H_(2)O,hArr,HAsc,+,H^(-),),(c " mol" L^(-1),,,,,,,),(c -ch ,,,,ch,,ch,):}`
`[OH^(-)]=ch=0.02xx10^(-4)=2xx10^(-6) "mol " L^(-1) :. [H^(+)]=(K_(w))/([OH^(-)])=(10^(-14))/(2xx10^(-6))=5xx10^(-9) "mol" L^(-1)`