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

Explanation

Suppose the degree of ionisation of HCNO is ` alpha `.
` {:(,HCNO, hArr , H^(+) , +, CNO^(-)),( "Initial conc. " , 0.1M , ,-,,-),(" Conc. at equilibrium",0.1(1-alpha),,0.1xx alpha,, 0.1xx alpha):}`
Give that pH of the solution is 2.34 Therefore
` " " -log_(10) (0.1 xx alpha) = 2.34 `
` or " "log_(10) (0.1 xx alpha) = -2.34`
` or " " 0.1 xx alpha = " antilog"_(10) (-2.34) = 0.00457`
` or " " alpha = ( 0.00457)/(0.1) = 0.0457`
` " "K_a = ([H^(+) ][CNO^(-) ])/([HCNO]) = ((0.1 xx alpha ) xx(0.1 xx alpha))/(0.1(1-alpha))`
` " "~~ ( (0.1xxalpha)^(2))/(0.1) = ((0.1 xx 0.0457)^(2))/(0.1)`
`" " = 2.09 xx 10^(-4)`