Question

The `pH` of `0.1 M` solution of cyanic acid `(HCNO)` is `2.34`. Calculate the ionization constant of the acid and its degree of ionisation in the solution.

Answer 1

(i). Calculation of degree of dissociation `(alpha)` in soluiton
`pH =2. 34 " or " - log [H^(+)] =2.34 " or " log [H^(+)] =- 2.34`
`[H^(+)] = " Antilog " (-2.34) = " Antilog " (bar(3) .66) = 4.571 xx 10^(-3) M`
`" Now"" " alpha [[H^(+)]]/(C) = ((4.571 xx 10^(-3)M))/((0.1M)) =4.571 xx 10^(-2) = 0.04571 M`
`= 4.571 xx 10^(-2) =0.04571 M`
(II). Calculation of ionisation constant of acid
`[H^(+)] =(K_(a) xx C) ^(1//2) " or " [H^(+)]^(2) =K_(a) xx C`
`K_(a) [[H^(+)]^(2)]/(C) =((.571 xx10^(-3) )^(2))/(0.1)= (20.89 xx 10^(-6))/(0.1) =20 .89 xx 10^(-5)`
`K_(a) =2.089 xx 10^(-4) ~~ 2.09 xx 10^(-4)`